Hannah Werdmuller :: Blog

I talked to my dissertation supervisor the other day and he pointed out some serious flaws in my dissertation plan. The problem is that I'm not starting out with a hypothesis, I'm fishing for results, which can easily mean I find a spurious result when in fact there is no relationship. It's the type of study where most of the work is actually coming up with the hypothesis, which is risky business for something this important in my degree.

So now I need to completely rethink it, and I've had a few ideas. So far this seems the most motivating:

The effect of soil microbial populations on drought resistance of millet.

This is mostly important in context of the paper Ekundayo, EO, 2003. “Effect of common pesticides used in the Niger Delta basin of southern Nigeria on soil populations.” Env. Monit. Ass. 89: 35-41, which found that some pesticides impaired soil microbes. The Niger Delta is seriously affected by drought, and one of the main crops grown on the floodplains is millet. So if soil microbes help plants resist drought, use of said pesticides may be exacerbating drought effects. One land management solution would be to protect flood forests, which provide nesting sites for cattle egrets and other waterfowl. Cattle egrets eat insects, particularly locusts, so removal of cattle egret habitat is likely to increase crop damage by locusts, combatted by pesticide use, which then exacerbates drought. I think it's likely that soil microbes will make plants more resistant to drought by facilitating nutrient transport and thereby allowing increased growth and lower incidence of plant malnutrition etc. Better growth also means better root networks, which in turn means less soil erosion. Hence, rather important.

I think that sounds pretty good. So I'll be writing to my supervisor on Monday to see if it's feasible and if so finalise methods.

Anyone have any information regarding drought and soil microbes, or on the Niger Delta in general? I find the region fascinating.

Tutorial 2 for Applied Ecology and Environmental Management at University of Edinburgh

Is the environmental cost of intensive livestock production too great?

Background

The British Government appears to be putting Environmental Protection ahead of Food Security. Other European countries seem to value the use of land for food production more highly than the UK. What should UK Government consider as appropriate action with regard to the livestock industries and the degree of their intensifaction that should be encouraged/tolerated. What should UK Farming look like 20 years from now, and why?

References

• DEFRA website. Scope the site using the search facility and terms such as LINK, science, environment, sustainability and Policy Commission for the Future of Farming and Food.
• DEFRA LINK Sustainable Livestock Production
• Scottish Executive (2002). Prevention of Environmental Pollution from Agricultural Activity.
• Ostergaard V and Hansen JP (1995). Indicators - a method to describe the sustainability of livestock farming.
• Scottish Executive (2001). A forward strategy for Scottish Agriculture. [Annexe A gives financial information about the livestock sector].
• The SAC 4 Point Plan

 

Here's an essay I've written on perfluorochemicals, for my 3rd year Environmental Pollution course at University of Edinburgh. It still needs to be beefed up by 350 words.

1658/2000

Pollution of the biosphere: Emerging chemical contaminants: the case of perfluorochemicals. Summarise and discuss the extent of biospheric contamination and the risk to health from the use of these fully fluorinated organic compounds by industry and commerce.
 

Persistent organic pollutants (POPs) are those that have the capacity to be retained in the environment over long periods of time, often with high potential for long-distance transport and bioaccumulation. Most POPs, such as PCBs and DDT, have lipophilic properties whereby they bioaccumulate in fatty tissues, concentrations increasing exponentially to toxic levels in higher trophic levels. Thus bald eagles (top predators) have experienced eggshell thinning through toxicity of DDT, despite insufficient concentrations in primary consumers to produce adverse effects (EPA, 1978). In order to prevent damage to wildlife and human health, the Stockholm Convention on Persistent Organic Pollutants has attracted 151 signatories worldwide with the intent of reducing or eliminating their release into the environment (UNEP, 2005).

In 1976, Guy & Taves detected organic fluorine in human blood after the fluoridation of drinking water, provoking investigation into the fate of fluorochemicals in the environment. Previously, the most abundant fluorochemical of concern and an end-stage metabolite and environmental degradation product of other fluorochemicals (Schnellman, 1990; Olsen et al., 1999; Karrman, 2004; Xu et al., 2004), perfluorooctane sulfonate (C₈F₁₇SO₃^-, PFOS), was deemed safe because, unlike most POPs, due to its lipophobic properties it does not accumulate in fatty tissues, and it does not react with DNA (EPA, 2000a). However, bioconcentration factors have been calculated at 10-20 for North American bald eagle and mink tissue, and approximately 1000 in benthic invertebrates, relative to their prey species (Kannan et al., 2005), and following accidental spillage of fire-retardant foam containing fluorinated surfactants, leading to contamination of Etobicoke Creek in Canada, bioconcentration factors of 6300-125000 were found in fish liver tissue relative to surface water (Moody et al., 2002). 

PFOS and the related perfluorochemical PFOA (perfluorooctanoic acid, a peroxisome proliferator – Kennedy et al., 2004) to a lesser degree tend to accumulate in the liver, kidneys, gall bladder and blood (perhaps recognised by the body as a bile acid, which is then recycled into the liver – Van den Heuvel et al., 1991; Kannan et al., 2002a; Kannan et al., 2002b; Jones et al., 2003), and impair gap junction intercellular communication, which is important for normal cell growth and function (Hu et al., 2002).

Previously, it was also assumed that PFOS would pose a lesser risk because it is relatively involatile, so should have low potential for long-range transport. However, it has been shown that PFOS an PFOA are degradation products (primarily via biological transformation in aquatic systems) of other more volatile and thus further-transported perfluorochemicals such as perfluoroalkyl sulfonamides (PFASs) (Shoeib et al., 2004; Dinglasan et al., 2004; Dimitrov et al., 2004), which would explain the worldwide detection of PFOS in oceanic water, and blood and tissue samples.

Kannan et al. (2002c) found PFOS present in the livers 100% of river otters sampled in Washington and Oregon, USA, and it is generally found at biomagnified concentrations at higher trophic levels, e.g. mink, otters, bald eagles, despite relatively low concentrations in fatty deposits (Giesy & Kannan, 2001). Higher levels of PFOS detected in liver and kidneys of stranded marine organisms of the North Sea further indicate biomagnification (Van de Vijver et al., 2003).

High residence time supports the theory that PFOS will persist in the environment (Giesy et al., 2001; Moody et al., 2002; Moody et al., 2003), and low levels have already been detected in animals in remote locations, e.g. 100% of a sample of Arctic species analysed in a 2004 investigation (Tomy et al., 2004; Martin et al., 2004a), indicating a potential for long-range transport, although at lower concentrations than closer to the source, e.g. the Great Lakes, Baltic and Mediterranean Seas (Giesy & Kannan, 2001; Martin et al., 2004b), downstream of the industrialised Pearl River Delta in southern China (So et al., 2004), and in Tokyo Bay (Taniyasu et al., 2004). Our contamination may have been even more extensive than planet Earth, due to the use of perfluorinated membranes manufactured by DuPont in fuel cells for space travel (Banerjee & Curtin, 2004).

In 2002, there was a class action suit against DuPont (also makers of the popular non-stick material Teflon®) after a farmer’s cows close to a landfill wasted and died, and it was found that drinking water had been contaminated (despite an appallingly unethical attempted cover-up by DuPont and West Virginia Department of Environmental Protection – Leach et al. v. DuPont and Lubeck Public Service District, 2002). Inhabitants near the PFOA-manufacturing plant were found to have a 12fold increase in blood serum concentrations compared to background levels (EWG, 2004), and a local newspaper reported respiratory difficulties and developmental problems in humans, and an observed increase in wildlife mortality (Lyons, 2003). Employees of one of 3M’s perfluorooctanesulfonyl fluoride manufacturing plant in Alabama, USA, who would have been exposed to a greater level of contamination than the background population, experienced benign colon polyps, malignant colorectal tumours and malignant melanoma (Olsen et al., 2004).

Indeed, dust samples of all the Japanese homes in a 2003 study contained PFOS and PFOA at low levels (Moriwaki et al., 2003), and PFOS was found in blood serum of all non-occupationally exposed human volunteers tested by both an American and a Canadian team, with all American volunteers also testing positive for PFOA, perfluorohexanosulphate (PFHxS), and perfluorononanoate (PFNA) and nine out of thirteen fluorochemicals in at least 75% of subjects (Kuklenyik et al., 2004; Kubwabo et al., 2004). Even Inuit of Nunavut, Northern Canada, were found to have traces of fluorinated organic compounds in their blood plasma (Tittlemier et al., 2004). Male humans tend to accumulate PFOA in their tissues quicker than females, although the levels are essentially equivalent after the age of about 60 (Harada et al., 2005). Kuklenyik’s investigation on American subjects could easily be applied to a wider sample of volunteers, providing a better indication of the global levels of perfluorochemical contamination in humans, and monitor their rate of change over time.

PFOA is the second most abundant fluorinated compound found in humans (Gilliland & Mandel, 1996; Kannan et al., 2004), and has been associated with increased occupational exposure leading to increased bladder cancer mortality (Alexander, et al., 2003) and a more than threefold increase in prostate cancer mortality (Gilliland & Mandel, 1993). Adverse effects on wildlife have also been shown in laboratory experiments with perfluorochemicals. Zooplankton and northern leopard frog population survival was seen to decrease by 90-100% in two weeks upon exposure to 10mg/L PFOS (Sanderson et al., 2002; Ankley et al., 2004). Postnatal mortality was observed in rats (Grasty, et al., 2002; Lau et al., 2001). Increased mortality and significant adverse effects were observed in monkeys when exposed to low levels (0.75mg/kg/day) of PFOS for 182 days, including weight loss, increased liver weight, reduced serum cholesterol, and reduced reproductive and thyroid enzymes (Seacat et al., 2002). PFOA is also a definite hepatocellular carcinoma promoter in rodents at a concentration of 0.02% of the basal diet (Abdellatif et al., 2003-2004).

Current ambient levels of PFOS and PFOA are lower by at least a factor of two than the level required to observe adverse effects in zooplankton and the midge Chironomus tentans (sensitive biotic indicators - Boudreau et al., 2003; MacDonald et al., 2004), but because the compounds are persistent and continue to be leached into the environment from landfills and public water disposal sites, e.g. the Kinki region of Japan (Harada et al., 2004; Saito et al., 2004), and continued industrial and commercial use of fluorinated compounds (4,481 metric tons globally in 2000 – OECD, 2002), e.g. in McDonalds packaging (EWG, 2004), their environmental concentrations can be expected to increase. Furthermore, the outdoor environmental concentrations of perfluorochemicals tend to considerably lower than those indoors (Shoeib et al., 2004). An increasing tendency for citizens of industrialized countries to spend more time indoors, with the age of information and consumerism, also means we subject ourselves to higher levels of exposure. Exposure in these cases could be lessened somewhat by reducing the proportion of carpeted floors in the home (Kubwabo et al., 2005), and not using non-stick pans or use food cartons with non-stick coatings, because perfluoro additives migrate from the cookware or food cartons to cooking oil by a factor of mgkg^-1 (Begley et al., 2005).

Ideally, of course, perfluorochemicals will become obsolete, having been replaced by compounds of similar utility but lower environmental impact. One example of a class of compounds that is being studied is hydrofluoropolyethers as flame-retardants (Malinverno et al., 2005). A couple of interesting development are the discovery that sonochemical decomposition of PFOS and PFOA yields shorter-chain polymers with decreased half-life (Moriwaki et al., 2005), and that a persulfate can be used as a photochemical oxidant to increase the decomposition rate of PFOA (Hori et al., 2005). These methods could in theory be used in waste disposal of PFOS and PFOA, lessening the impact of landfills and public water disposal sites.

However, so too seem the “safe levels” assigned to drinking water to increase sporadically, in Ohio by a factor of 150 (from 1ppb to 150ppb - OEPA, 2002). Regardless, the possibility of accidental spillage e.g. contamination of Etobicoke Creek, Canada, as well as deliberate concentrated use e.g. of fire-fighting foam in Tomakomai, Japan (Yamashita et al., 2004), raising environmental concentrations remains a real concern (Moody et al., 2002; Oakes et al., 2004). On the other hand, these concentrations may end up being almost entirely arbitrary, given that effects on cell membranes (facilitating contamination by all pollutants) are seen well below the levels associated with other adverse effects (Hu et al., 2003).

PFOS and the potentially hundreds of precursors and structural isomers (Langlois & Oehme, 2004) were under review to be added to the Stockholm Convention list in December 2005 (POPRC, 2006), and many manufacturers have endeavoured to voluntarily phase out PFOS-containing products, such as 3M’s Scotchgard (EPA, 2000b). However, the molecularly similar perfluorinated carboxylic acids and volatile telomer alcohols that degrade into PFOA are still used commercially as stain and water-repellents to treat textiles (Arsenault et al., 2004; Berger et al., 2004).

 

 

References:

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Abdellatif, A., Al-Tonsy, A.H., Awad, M.E., Roberfroid, M. & Khan, M.N. 2004 Peroxisomal enzymes and 8-hydroxydeoxyguanosine in rat liver treated with perfluorooctanoic acid. Disease markers 19(1): 19-25

 

Alexander, B.H., Olsen, G.W., Burris, J.M., Mandel, J.H. & Mandel, J.S. 2003 Mortality of employees of a perfluorooctanyl fluoride manufacturing facility. Occupational and environmental medicine 60(10): 722-9

 

Ankley, G.T., Kuehl, D.W., Kahl, M.D., Jensen, K.M., Butterworth, B.C. & Nichols, J.W. 2004 Partial life-cycle toxicity and bioconcentration modelling of perfluorooctanesulfonate in the northern leopard frog (Rana pipiens). Environmental toxicology and chemistry 23(11): 2745-55

 

Arsenault, G., Chittim, B., Ellis, D., Haldorson, T., Mabury, S.A., McAlees, A., McCrindle, R., Stock, N., Tomy, G. & Yeo, B. 2004 Nuclear magnetic resonance and LC/MS characterisation of native and new mass-labelled fluorinated telomer alcohols, acids and unsaturated acids. Dioxin 2004: 24^th international symposium on halogenated environmental organic pollutants and POPs, Berlin, September 6-10 2004. Organohalogen compounds 66: 4015-22

 

Banerjee, S. & Curtin, D.E. 2004 Nafion® perfluorinated membranes in fuel cells. Journal of fluorine chemistry 125(8): 1211-6

 

Begley, T.H., White, K., Honigfort, P., Twaroski, M.L., Neches, R. & Walker, R.A. 2004 Perfluorochemicals: potential sources of and migration from food packaging. Food additives and contaminants 22(10): 1023-31

 

Berger, U., Jarnberg, U. & Kallenborn, R. 2004 Perfluorinated alkylated substances (PFASs) in the European Nordic environment. Dioxin 2004: 24^th international symposium on halogenated environmental organic pollutants and POPs, Berlin, September 6-10 2004. Organohalogen compounds 66: 4046-52

 

Boudreau, T.M., Wilson, C.J., Cheong, W.J., Sibley, P.K., Mabury, S.A., Muir, D.C. & Solomon, K.R. 2003 Response of the zooplankton community and environmental fate of perfluorooctane sulfonic acid in aquatic microcosms. Environmental toxicology and chemistry 22(11): 2739-45

 

Dimitrov, S., Kamenska, V., Walker, J.D., Windle, W., Purdy, R., Lewis, M. & Mekenyan, O. 2004 Predicting the biodegradation products of perfluorinated chemicals using CATABOL. SAR and QSAR in environmental research 15(1): 69-82

 

Dinglasan, M.J., Ye, Y., Edwards, E.A. & Mabury, S.A. 2004 Fluorotelomer alcohol biodegradation yields poly- and perfluorinated acids. Environmental science and technology 38(10): 2857-64

 

EPA (Environmental Protection Agency) 1978 Determination of certain bald eagle populations as endangered or threatened. Federal Register Environmental Documents 43:6230-3

 

EPA 2000a Perfluorooctyl sulfonates: proposed new use rule. Federal Register Environmental Documents 65(202): 62319-33

 

EPA 2000b EPA and 3M announce phase out of PFOS. EPA Newsroom, for release May 16 2000

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Giesy, J.P. & Kannan, K. 2001 Global distribution of perfluorooctane sulfonate in wildlife. Environmental science and technology 35(7): 1339-42

 

Giesy, J.P., Kannan, K. & Jones, P.D. 2001 Global biomonitoring of perfluorinated organics. Scientific world journal 1(11): 627-9

 

Gilliland, F.D. & Mandel, J.S.1993 Mortality among employees of a perfluorooctanoic acid production plant. Journal of occupational medicine 35(9): 950-4

 

Gilliland, F.D. & Mandel, J.S. 1996 Serum perfluorooctanic acid and hepatic enzymes, lipoproteins, and cholesterol: a study of occupationally exposed men. American journal of industrial medicine 29(5): 560-8

 

Grasty, R.C., Grey, B.E., Thibodeaux, J., Lau, C. & Rogers, J.M. 2002 Critical period for increased neonatal mortality induced by perfluorooctane sulfonate (PFOS) in the rat. Toxicologist 66(1-S): 25

 

Guy, W.S. & Taves, D.R. 1976 Organic Fluorocompounds in human plasma:

Prevalence and characterisation. American Chemical Society, ACS Symposium Series No. 28: 117-34

 

Harada, K., Saito, N., Inoue, K., Yoshinaga, T., Watanabe, T., Sasaki, S., Kamiyama, S., Koizumi, A. 2004 The influence of time, sex and geographic factors on levels of perfluorooctane sulfonate and perfluorooctanoate in human serum over the last 25 years. Journal of occupational health 46(2): 141-7

 

Harada, K., Inoue, K., Morikawa, A., Yoshinaga, T., Saito, N. & Koizumi, A. 2004 Renal clearance of perfluorooctane sulfonate and perfluorooctanoate in humans and their species-specific excretion. Environmental research 99(2): 253-61

 

Hori, H., Yamamoto, A., Hayakawa, E., Taniyasu, S., Yamashita, N., Kutsuna, S., Kiatagawa, H. & Arakawa, R. 2004 Efficient decomposition of environmentally persistent perfluorocarboxylic acids by use of persulfate as a photochemical oxidant. Environmental science and technology 39(7):2383-8

 

Hu, W., Jones, P.D., Upham, B.L., Trosko, J.E., Lau, C., & Giesy J.P. 2002 Inhibition of gap junction intercellular communication by perfluorinated compounds in rat liver and dolphin kidney epithelial cell lines in vitro and Sprague-Dawley rats in vivo. Toxicological sciences 68(2): 429-36

 

Hu, W., Jones, P.D., de Coen, W., King, L., Fraker, P., Newsted, J. & Giesy, J.P. 2003 Alterations in cell membrane properties caused by perfluorinated compounds. Comparative biochemistry and physiology: toxicology and pharmacology 135(1): 77-88

 

Jones, P.D., Hu, W., de Coen, W., Newsted, J.L. & Giesy, J.P. 2003 Binding of perfluorinated fatty acids to serum proteins. Environmental toxicology and chemistry 22(11): 2639-49

 

Karrman, A., van Bavel, B., Jarnberg, U., Hardell, L. & Lindstrom, G. 2004 Levels of perfluoroalkylated compounds in whole blood from Sweden. Dioxin 2004: 24^th international symposium on halogenated environmental organic pollutants and POPs, Berlin, September 6-10, 2004. Organohalogen compounds 66: 4058-62

 

Kannan, K., Choi, J.W., Iseki, N., Senthilkumar, K., Kim, D.H. & Giesy, J.P. 2002a Concentrations of perfluoroniated acids in livers of birds from Japan and Korea. Chemosphere 49(3): 225-31

 

Kannan, K., Corsolini, S., Falandysz, J., Oehme, G., Focardi, S. & Giesy, J.P. 2002b Perfluorooctanesulfonate and related fluorinated hydrocarbons in marine mammals, fishes, and birds from coasts of the Baltic and the Mediterranean seas. Environmental science and technology 36(15): 3210-6

 

Kannan, K., Newsted, J., Halbrook, R.S. & Giesy, J.P. 2002c Perfluorooctanesulfonate and related fluorinated hydrocarbons in mink and river otters from the United States. Environmental science and technology 36(12): 2566-71

 

Kannan, K., Corsolini, S., Falandysz, J., Fillmann, G., Kumar, K.S., Loganathan, B.G., Mohd, M.A., Olivero, J., van Wouwe, N., Yang, J.H. & Aldoust, K.M.  2004 Perfluorooctanesulfonate and related fluorochemicals in human blood from several countries. Environmental science and technology 38(17): 4489-95

 

Kannan, K., Tao, L., Sinclair, E., Pastva, S.D., Jude, D.J. & Giesy, J.P. 2005 Perfluorinated compounds in aquatic organisms at various trophic levels in a Great Lakes food chain. Archives of environmental contamination and toxicology 48(4): 559-66

 

Kennedy, G.L. Jr, Butenhoff, J.L., Olsen, G.W., O’Connor, J.C., Seacat, A.M., Perkins, R.G., Biegel, L.B., Murphy, S.R. & Farrar, D.G. 2004 The toxicology of perfluorooctanoate. Critical reviews in toxicology 34(4): 351-84

 

Kubwabo, C., Vais, N. & Benoit, F.M. 2004 A pilot study on the determination of perfluorooctane sulfonate and other perfluorinated compounds in blood of Canadians. Journal of environmental monitoring 6(6): 540-5

 

Kubwabo, C., Stewart, B., Zhu, J. & Marro, L. 2004 Occurrence of perfluorosulfonates and other perfluorochemicals in dust from selected homes in the city of Ottawa, Canada. Journal of environmental monitoring 7(11): 1074-8

 

Kuklenyik, Z., Reich, J.A., Tully, J.S., Needham, L.L. & Calafat, A.M. 2004 Automated solid-phase extraction of perfluorinated organic acids amides in human serum and milk. Environmental science and technology 38(13): 3698-704

 

Langlois, I. & Oehme, M. 2004 Identification of the isomer composition in technical perfluorooctane sulfonate solution by LC-ESI(-)-IT-MS-/MS. Dioxin 2004: 24^th international symposium on halogenated environmental organic pollutants and POPs, Berlin, September 6-10 2004. Organohalogen compounds 66: 4023-8

 

Lau, C., Rogers, J.M., Hanson, R.G., Barbee, B.D., Nartosky, M.G., Schmid, J.E. & Richards, J.H. 2001 Developmental toxicity of perfluorooctane sulfonate in the rat and mouse. Teratology 63(6): 290

 

Leach, J.W. et al. v. E.I. DuPont de Nemours and Company and Lubeck Public Service District 2002 Injunction order directed to Dee Ann Staats, Ph.D. and the West Virginia Department of Environmental Protection. Civil Action No. 01-C-608 (Judge Hill) in the Circuit Court of Wood County, West Virginia, 25 June 2002

 

Lyons, C. 2003 Examining the water we drink: Concerns about C8 linger. The Marietta Times, Ohio, September 27 2003.

 

MacDonald, M.M., Warne, A.L., Stock, N.L., Mabury, S.A., Solomon, K.R. & Sibley, P.K. 2004 Toxicity of perfluorooctane sulfonate and perfluorooctanoic acid to Chironomus tentans. Environmental toxicology and chemistry 23(9): 2116-23

 

Malinverno, G., Colombo, I. & Visca, M. 2004 Toxicological profile of hydrofluoropolyethers. Regulatory toxicology and pharmacology 41(3): 228-39

 

Martin, J.W., Whittle, D.M., Muir, D.C. & Mabury, S.A. 2004a Perfluoroalkyl contaminants in a food web from Lake Ontario. Environmental Science and Technology 38(20): 5379-85

 

Martin, J.W., Smithwick, M.M., Braune, B.M., Hoekstra, P.F., Muir, D.C. & Mabury, S.A. 2004 Identification of long-chain perfluorinated acids in biota from the Canadian arctic. Environmental science and technology 38(2): 373-80

 

Moody, C.A., Martin, J.W., Kwan, W.C., Muir, D.C. & Mabury, S.A. 2002 Monitoring perfluorinated surfactants in biota and surface water samples following an accidental release of fire-fighting foam into Etobicoke Creek.  Environmental science and technology 36(4): 545-51

 

Moody, C.A., Hebert, G.N., Strauss, S.H. & Field, J.A. 2003 Occurrence and persistence of perfluorooctane sulfonate and other perfluorinated surfactants in groundwater at a fire-training area at Wurtsmith Airforce Base, Michigan, USA. Journal of environmental monitoring 5(2): 341-5

 

Moriwaki, H., Takatah, Y. & Arakawa R. 2003 Concentrations of perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) in vacuum cleaner dust collected in Japanese homes. Journal of environmental monitoring 5(5): 753-7

Moriwaki, H., Takagi, Y., Tanaka, M., Tsuruho, K., Okitsu, K. & Maeda, Y. 2004 Sonochemical decomposition of perfluorooctane sulfonate and perfluorooctanoic acid. Environmental science and technology 39(9): 3388-92

Oakes, K.D., Sibley, P.K., Solomon, K.R., Mabury, S.A. & van der Kraak, G.J. 2004 Impact of perfluorooctanoic acid on fathead minnow (Pimephales promelas) fatty acyl-CoA oxidase activity, circulating steroids, and reproduction in outdoor microcosms. Environmental toxicology and chemistry 23(8): 1912-9

 

OECD (Organisation for Economic Cooperation and Development) 2002 Cooperation on existing chemicals: Hazard assessment of perfluorooctane sulfonate and its salts. Joint meeting of the chemicals committee and the working party on chemicals, pesticides and biotechnology 21 November 2002

 

OEPA (Ohio Environmental Protection Agency) 2002 Little Hocking Water comments. Ohio Environmental Protection Agency meeting, Columbus, Ohio July 24 2002

 

Olsen, G.W., Burris, J.M., Mandel, J.H & Zobel, L.R. 1999 Serum perfluorooctane sulfonate and hepatic and lipid clinical chemistry tests in fluorochemical production employees. Journal of occupational and environmental medicine 41(9): 799-806

 

Olsen, G.W., Burlew, M.M., Marshall, J.C., Burris, J.M., and Mandel, J.H. 2004 Analysis in episodes of care in a perfluorooctanesulfonyl fluoride production facility. Journal of occupational and environmental medicine 46(8): 837-46

 

POPRC (Persistent Organic Pollutants Review Committee) 2006 Advance unedited draft: Decision POPRC-1/7on perfluorooctane sulfonate. http://www.pops.int/documents/meetings/poprc/meeting_docs/decision%20poprc-1-7.pdf visited 13/02/06

 

Saito, N., Harada, K., Inoue, K., Sasaki, K., Yoshinaga, T. & Koizumi, A. 2004 Perfluorooctanoate and perfluorooctane sulfonate concentrations in surface water in Japan. Journal of occupational health 46(1): 49-59

 

Sanderson, H., Boudreau, T.M., Mabury, S.A., Cheong, W.J. & Solomon, K.R. 2002 Ecological impact and environmental fate of perfluorooctane sulfonate on the zooplankton community in indoor microcosms. Environmental toxicology 21(7): 1490-6

 

Schnellmann, R.G. 1990 The cellular effects of a unique pesticide sulfuramid (N-ethylperfluorooctanesulfonamide) on rabbit renal proximal tubules. Toxicology in vitro 4(1): 71-4

 

Seacat, A.M., Thomford, P.J., Hansen, K.J., Olsen, G.W., Case, M.T. & Butenhoff, J.L. 2002 Subchronic toxicity studies on perfluoprooctanesulfonate potassium salt in cynomolgus monkeys. Toxicological sciences 68(1): 249-64

 

Shoeib, M., Harner, T., Wilford, B., Jones, K. & Zhu, J. 2004 A survey of perfluoroalkyl sulfonamides in indoor and outdoor air using passive air samplers. Dioxin 2004: 24^th international symposium on halogenated environmental organic pollutants and POPs, Berlin, September 6-10 2004. Organohalogen compounds 66: 3999-4003

 

So, M.K., Taniyasu, S., Yamashita, N., Giesy, J.P., Zheng, J., Fang, Z., Im, S.H. & Lam, P.K. 2004 Perfluorinated compounds in coastal waters of Hong Kong, South China, and Korea. Environmental science and technology 38(15): 4056-63

 

Taniyasu, S., Yamashita, N., Kannan, K., Horii, Y., Sinclair, E., Petrick, G. & Gamo, T. 2004 Perfluorinated carboxylates and sulfonates in open ocean waters of the Pacific and Atlantic oceans. Dioxin 2004: 24^th international symposium on halogenated environmental organic pollutants and POPs, Berlin, September 6-10 2004. Organohalogen compounds 66: 4035-40

 

Tittlemier, S., Ryan, J.J. & van Oostdam, J. 2004 Presence of anionic perfluorinated organic compounds in serum collected from Northern Canadian populations. Dioxin 2004: 24^th international symposium on halogenated environmental organic pollutants and POPs, Berlin, September 6-10 2004. Organohalogen compounds 66: 4009-14

 

Tomy, G.T., Budakowski, W., Halldorson, T., Helm, P.A., Stern, G.A., Friesen, K., Pepper, K., Tittlemier, S.A. & Fisk, A.T. 2004 Fluorinated organic compounds in an eastern Arctic marine food web. Environmental science and technology 38(24): 6474-81

 

UNEP (United Nations Environmental Program) 2005 Stockholm Convention on Persistent Organic Pollutants (POPs) http://www.pops.int/ visited 13/02/06

 

Van de Vijver, K.I., Hoff, P.T., Das, K., Van Dongen, W., Esmans, E.L., Jauniaux, T., Bouquegneau, J.M., Blust, R. & de Coen, W. 2003 Perfluorinated chemicals infiltrate ocean waters: link between exposure levels and stable isotope ratios in marine mammals. Environmental science and toxicology

 

Van den Heuvel, J.P., Kuslikis, B.I., Van Rafelghem, M.J. & Peterson, R.E. 1991 Tissue distribution, metabolism, and elimination of perfluorooctanoic acid in male and female rats. Journal of biochemical toxicology 6(2): 83-92

 

Xu, L., Krenitsky, D.M., Seacat, A.M., Butenhoff, J.L. & Anders, M.W. 2004 Biotransformation of N-ethyl-N-(2-hydroxyethyl)perfluorooctanesulfonamide by rat liver microsomes, cytosol and slices and by expressed rat and human cytochromes P450. Chemical research in toxicology 17(6): 767-75

 

Yamashita, N., Kannan, K., Taniyasu, S., Horii, Y., Hanari, N., Okazawa, T. & Petrick, G. 2004 Environmental contamination by perfluorinated carboxylates and sulfonates following the use of fire-fighting foam in Tomakomai, Japan. Dioxin 2004: 24^th international symposium on halogenated environmental organic pollutants and POPs, Berlin, September 6-10 2004. Organohalogen compounds 66: 4063-6

 

 

 

 

 

Anyone know of any fun papers on fluorochemicals in the environment?

Newest song, recorded at Modesto Sound with Brenda Francis, and retouched by Lucky Lew.

 Hannah Werdmuller - Your Fool

 

 

Yo, have a bit of stuff after F.C. Hoppensteadt's "Mathematical methods of population biology" on two-state Markov chains.

Markov chains

So begins third year. This practical report comprises 0.75% of my graduation mark for my entire university career (Biological Sciences, University of Edinburgh). The simulation programme we used was "Drift32". Any comments?

1. What is the fate of selectively neutral variation in red panda populations of finite size? How is this influenced by population size?

When there is selectively neutral variation in a simulation of an isolated zoo population of size 5, the majority of resultant red panda genotypes are by far homozygotes for either allele (only 12% of loci exhibiting polymorphism, whereas if the population were in Hardy-Weinberg equilibrium, given the allele frequencies, the expected frequency of heterozygotes would be 48%) and the genetic diversity has decreased from 0.48 to 0.0392 (9-fold). This indicates that there are effectively two subpopulations with very limited breeding between them, and higher instance of inbreeding within them, leaving them susceptible to inbreeding depression should a deleterious mutation arise. In the simulation of a population involved in a collaborative breeding program of 50 individuals, there is 96% polymorphism, and the mean genetic diversity remains comparatively high. In summary, small populations tend to result in monomorphism due to high levels of inbreeding, whereas large populations retain high genetic diversity and low inbreeding.

2. To what extent is balancing selection effective in maintaining genetic variation in the red panda populations? How is this affected by population size?

Balancing selection in the simulated population of size 5 resulted in nearly four times greater genetic diversity than in selectively neutral variation, but the value was still low (0.1512). However, in the simulated population of 50 individuals, 100% were polymorphic, and the genetic diversity remained almost the same (0.44, or nearly three times greater than that of a population of size 5). This indicates that small populations still have low genetic diversity even when there is balancing selection, whereas balancing selection is very effective at maintaining genetic variation in large populations.

3. What is the fate of newly arising deleterious alleles in the red panda populations? How is this influenced by population size?

Newly arising deleterious alleles in a simulated red panda population of size 5 resulted in complete homozygosity, with low genetic diversity: 80% of individuals fixed for the non-mutant allele, with purifying selection against the mutant allele, and 20% of the meta-population fixed for the deleterious allele by inbreeding. Continued genetic isolation will result in extinction of the deleterious allele. In a population of 50 the genetic diversity remains low, and no individuals are homozygous for the mutant allele. These results suggest that in smaller populations a newly arising deleterious mutation is selected against to some extent, and becomes fixed in a smaller, declining sub-population by inbreeding. In a larger population, homozygotes of the deleterious allele have extremely low breeding success, so homoygosity for the non-mutant allele and polymorphism are selected for, and deleterious effects of the mutant allele are not expressed in the population.

4. From a genetic point of view, is it best to maintain red pandas in separate populations of size 5, or with a collaborative breeding programme where population size is 50? Support your conclusions using the results from the simulations that you have conducted.

In the simulations for all of selectively neutral variation, heterozygous advantage and purifying selection, the populations of size 50 have greater genetic diversity than those of size 5 (0.37, 0.44 and 0.069 compared to 0.0392, 0.1512 and 0.056 respectively). Because of their increased heterozygosity, larger populations are less susceptible to deleterious mutations that would result in a decline in numbers due to inbreeding depression, which particularly in terms of an animal we are interested in conserving, such as the red panda, is a definite advantage. Furthermore, in the simulation of purifying selection, whereas there were a couple of individuals (20%) homozygous for the deleterious allele in the population of size 5, the phenotype with reduced fitness was never expressed in the population of size 50, so despite mean genetic diversity in the population of size 50 still being small compared to with balancing or no selection (0.069 as opposed to 0.37 and 0.44), and the deleterious allele remaining in both populations (28% polymorphism in the larger population), it is still advantageous in terms of total fitness to maintain red pandas in the larger population. For this reason I conclude that, from a genetic point of view, it is best to maintain red pandas with a collaborative breeding programme where the population size is 50.

Cape Cod resembles a flexed arm of sand thrust out into the Atlantic Ocean. It owes much of its origin to as recently as 14,000 years ago. Since tht time waves and currents have extensively reshaped the sedimentary deposits left by these glaciers into sandy beaches, barrier islands, and saltwater marshes. The coastline of Cape Cod is the longest natural coastline of New England, and it has hardly been modified by shore-protective structures.

About 15,300 years ago, all of New England was covered by a huge sheet of ice that flowed southward from Canada. As this ice mass crept along the continental shelf, one of its ice lobes - the Cape Cod Bay Lobe - deposited sediment along its edge and formed a ridge, called a terminal moraine because it marks the farthest (terminal) position of the glacier. The terminal moraine can now be traced across Martha's Vineyard and Nantucket Island, the two principal islands of the Cape. As the climate became warmer, the ice lobe melted and retreated northward, depositing a series of recessional moraines that stretch along the Elizabeth Islands and the northern coastline of Cape Cod Bay. During the retreat of the ice sheet, meltwater from the glaciers was trapped between the end of the ice lobe and the recessional moraine, forming the huge Lake Cape Cod. Beds of mud and silt and delta sands were deposited in this glacial lake and covered the glacial sediments.

With the melting of glaciers worldwide, sea levels rose. Erosion of the glacial deposits by waves produced steep cliffs called bluffs, many of which are still retreating at alarming rates, some by as much as 1m (3.3ish ft) per year. The glacial sediment eroded from the bluffs is poorly sorted and is moved about by waves and currents according to grain size. Gravel and boulders tend to accumulate at the base of the bluffs. Clay and silt particles are suspended in the water and swept offshore or into sheltered bays. Sand is kept in the nearshore zone and moved parallel to the shoreline by longshore currents, supplying many of the beaches of the area. To the north of Wellfleet-by-the-Sea, sand drifts northward and gets coarser towards Provincetwon; to the south of Wellfleet-by-the-Sea, it driftsdownards and gets finer-grained with distance of transport. The reason for the opposing grain-size trends is unclear.

This is the last one ...

What I think I know about wastes:

Wastes

Most general domestic/municipal waste is currently sent to landfill (83%); 8% is recycled; 9% is incinerated.

Burning was once considered to be the most effective method for disposing of waste materials, but since the industrial revolution, the nature of waste material has changed significantly. In particular, the mass production of chemicals and plastics means that incineration of current waste materials is a complex, costly and potentially highly polluting method of disposal. Incinerators generally do not destroy the wastes completely but instead produce solid ashes that require disposal in landfill sites – these may be contaminated with heavy metals, unburned chemicals and new chemicals formed during the incineration process, which, when emitted to the atmosphere, pose a significant threat to human health.

Electrostatic precipitators are currently used to remove more than 97% of large ash particulates. If these precipitators break down there is likely to be a significant breach of air quality regulations. The small amount of particulate matter that is not removed by the precipitators may cause problems where the flue gases are subsequently passed into SO2 removal plants.

High temperature incineration aims to destroy toxic and pathogenic materials and other combustible organic compounds, and highly efficient destruction of waste (e.g. principal organic hazardous constituents, dioxins and furans) is required by regulation, and achieved by sufficient O2 in the combustion zone, thorough mixing of the waste + oxidant, high temperature (900+, or 1000+ for PCBs), and a residence time of more than 2 seconds for the complete reaction. The main problems associated with this method are that very high temperatures mean that the process is very energy intensive, NOx and SO2 are emitted, and ash requires disposal.

Low temperature incineration involves the rotary kiln method, e.g. to treat contaminated soils. The soil is placed in the inner shell and heated (315-485degsC); steam is injected through the outer shell and volatilised organic chemicals are swept out of the soil. An activated carbon column removes the organic chemicals before the gases are vented to the atmosphere; the chemicals are then recovered and destroyed under controlled conditions (in the absence of the soil matrix). Advantages to this method are that destruction of waste is 10x more efficient, lower energy costs and lower NOx emissions.

Extremely high temperature incineration involves a plasma arc furnace at 30,000K, designed to destroy POHCs at a rate of 3-4L/min. This is very energy intensive, but it works, and some energy can be recovered: highly ionised exhaust gases, when passed trough a superconducting magnet looped around the exterior of the exhaust chimney, induce a voltage between a series of paired electrodes, and the energy can be used to power the plasma arc. Once the temperature of flue gases has been decreased to less than 2000K, the gases can be used to vaporise water, used to drive turbines and produce electricity. The flue gases contain Cl and H atoms which can be removed to produce industrially useful hydrochloric acid.

Heavy metals are not destroyed during incineration; high temperature combustion releases toxic heavy metals, e.g. lead, cadmium, arsenic, mercury and chromium, from waste products such as batteries, paints, and certain plastics. Metals may be emitted to the atmosphere in association with very small particles, with risk of inhalation. Some but not all of the metals can be removed from the flue gases, and disposed along with the solid wastes at landfill sites.

Fragments of partially combusted waste chemicals recombine within the incinerator to form 100s and 1000s of new chemicals, many of whom are more toxic than those contained in the original waste, e.g. dioxins and furans, which are created when chlorinated materials are combusted. Scrubbers designed to remove particles will cool flue gases to the ideal temperature for dioxin formation. These compounds can cause cancer, altered sexual development, immunosuppression, diabetes, organ toxicity, etc. The main route of human exposure is through ingestion.

Release of CO2, the most important greenhouse gas, a major contributor being fossil fuel combustion, is minimised by cryogenic distillation and deep ocean disposal, carbonate/silicate slurry, chemical absorption (monoethylamine), and fertilising the oceans.

New pollutants such as Nox (emitted from any high temperature combustion plant), SO2 (by oxidation of sulphur from wastes), and HCl (from chlorinated wastes) have appeared.

Release of NOx is minimised during combustion is achieved by low NOx burners, or low NOx burners with selective non-catalytic reduction, or low NOx burners with gas reburn. Post-combustion, selective catalytic reduction, iron(II) thiochelate complex formation, and phosphorous/alkali emulsion.

Release of SO2 is minimised pre-combustion use of low impurity coal or sulphur removal prior to combustion (by cleaning with water or using its greater density to separate pyritic sulphur, or by alkaline trapping of liberated H2S on precombustion in the presence of H2), and post-combustion by fluidised bed combustion (whereby limestone/gypsum reduces SOx emissions in flue gas) and flue gas desulfurisation (whereby limestone/gypsum, spray dry absorption, Wellman Lord Regenerative or seawater scrubbing are used to reacted or absorbed and neutralised). Seawater scrubbing realises 90% efficient particle removal, but is suitable only in areas with seawater available.

There are many alternatives to incineration, including thermal and bio treatments. Hot metal is used to treat contaminated oils; sodium is mixed with paraffin and then heated to melting point; the molten mixture is mixed with contaminated oil and heated to 160degsC for about an hour, after which dechlorination is efficiently achieved without the formation of dioxins. Solar energy is particularly good for treatment of small organic chemicals in wastewater, but not useful for treatment of other contaminated matrices. In situ bioremediation involves addition of other organic waste materials (manure, old newspapers, straw and woodchips) to stimulate microbial activity, causing breakdown of organic chemicals, e.g. DDT/DDD/DDE, PCBs, and PAHs. 95% destruction efficiency is achieved, at approximately half the cost of incineration, and there is no solid waste for disposal.

From past mining activities, closure was followed by flooding of mines, releasing substantial quantities of sulphuric acid and iron hydroxides into the environment. From present mining activities, open cast/surface mining, where rainwater and groundwater require pumping from the bottom of the pit, has the potential to pollute surface waters and deeper aquifers used for drinking water supplies.

Whereas the potential of bioremediation is substantial, its application has important limitations. The main difficulties are associated with the degree to which microoganisms can access the contaminants (this decreases over time due to contaminant being incorporated into organic matter), and the relative degradability of components of complex mixtures.

Aluminium is the 3rd most abundant element in the earth’s crust, and is mainly present in primay minerals and in clays (feldspars, keolinite); isolation of Al from these materials is not economic. Bauxite, a result of natural weathering processes, is the only commercially used ore for the production of Al, but bauxite deposits have iron and silicon impurities. The first stage of processing involves alkaline dissolution of Al (and Si) leaving an alkaline slurry of fine particulate material (mainly iron oxides); then precipitation of Al hydroxide generates an aqueous waste stream containing dissolved silicate. The second stage involves electrolysis, very energy intensive and creating gaseous wastes.

Red mud is the main solid waste from the aluminium industry; it was previously disposed of by dumping, but leachates, highly alkaline solutions of NaOH and NaCO3, contaminated local streams, rivers and lochs. Fine solids (mainly haematite) are washed into water bodies as suspended solids, and the result can be infilling of lochs at a rate of several cm/yr. The alternative is to utilise the waste material in the treatment of wastewaters containing, for example, high concentrations of dissolved heavy metals (iron oxides have well known sorption capabilities). This requires careful disposal of the waste material following treatment, e.g. solidification (waste mixed with cement-based formulations). Recycling reduces the volume of waste material produced.

Spent radioactive fuel rods are stored underwater for 6-12months, chopped into 3-5cm pieces, and dissolution of uranium, plutonium and fission products is achieved by boiling concentrated nitric acid, then separating the fission products using an organic solvent, and separating uranium and plutonium be reducing plutonium to the +III state and extracting it into aqueous solution. Reprocessing generates various wastes, which are generally highly acidic, contain small amounts of uranium, plutonium and fission products, many of the radionuclides have very long half-lives, and contain components of the solvents (both radioactive and inactive).

Past disposal methods included tipping into shallow, unlined pits. Nowadays we dispose of compressed radioactive wastes in steel canisters reinforced with concrete and placed in concrete-lined vaults. Eventually the vaults are sealed with concrete and covered over with clay, and the disposal site is re-vegetated. The disposal site is monitored by collecting leachates and screening them,prior to discharge via a marine pipeline, and gases before venting them into the atmosphere. Low-level liquid wastes contain small quantities of uranium and plutonium and fission products. Some clean-up of waste is followed by marine discharge, e.g. from Sellafield to the Irish sea, with accommodating regulatory limits.

Nowadays, after clean-up via precipitation, ion exchange, etc., there is marine discharge, which must comply with more stringent regulatory limits agreed with the Nuclear Inspectorate. Intermediate level liquids are neutralised, some high-level liquid waste is vitrified, and solid waste are stored on-site in steel canisters. On-site storage is not a long-term option due to the amount of material that can be stored, the hazards associated with degradation of steel canisters, and the potential terrorist threat. Sites are selected by the geological stability of the area; the absence of large fractures in the solid repository matrix; impermeability of the repository water to surface water; negligible groundwater circulation in the vicinity of the repository; good heat conductivity of the repository solid matrix.

A rock characterisation facility was planned at Longlands Farm but rejected by NIREX to address groundwater flow and radionuclide transport, natural and induced changes to the geological barrier, and design and construction of the repository. The concept involved a multibarrier containment system, with steel containers/cement grout, chemical cement backfill, stable rocks from the Borrowdale Volcanic Group, but there was potential movement of water through the repository and concern about microbial activity.

There is a waste isolation pilot plant in Saledo, New Mexico, where there is little rainfall so it’s very dry. Military wastes containing mainly plutonium are placed in steel canisters, being transferred to the WIPP repository. Unfortunately, the salt bed is not water free; there are saline pockets within it. Due to the thermal heat of the waste, the brine pockets migrate towards the repository promoting enhanced corrosion. Upon breach of the canisters, there is potential for transport of plutonium out of the canisters, so careful monitoring of groundwater and surface waters is currently being undertaken.

In the Yucca Mountain range, Nevada, there is extremely low rainfall, slow groundwater movement, and the rock is volcanic (very hard, highly absorbing, good heat conductivity). The repository here is positioned above the water table. However, volcanic cinder cones in the vicinity indicating seismic activity may occur within the 10,000 years needed for storage, and recent work has demonstrated the existence of fast flow paths, and chlorine-36has been found at the depth of the proposed repository. There has been little/no testing of the alloys used to construct the storage canisters, and once the canisters have been breached, the radionuclides would be exposed to air and potentially come into contact with water. Uranium(IV), for example, in the waste would be oxidised in air to uranium(VI), the soluble form, so contact with water could result in dissolution and potential transport out of the repository.

What I think I know about green chemistry:

Green chemistry is concerned with avoiding the creation of waste or pollution, but this is difficult because maximum yield and minimum cost were the driving factors for selecting a particular reaction route, and only recently is minimising or eliminating wasteful by-products becoming a focus. Atom economy incorporates as many materials used as possible into the final product. Wherever practicable, synthetic methods should be designed to use and generate substances that possess little or no toxicity, while still effectuating their desired function. The big drive for change is from environmental legislation, imposing fines and thus making it more economically sound to be green.

The use of auxiliary substances such as solvents or separating agents should be made unnecessary wherever possible and innocuous when used. Catalytic reagents (as selective as possible) are superior to stoichiometric reagents. Solvents are a major source of waste, causing atmospheric pollution (smog, etc.), and may be carcinogens.

Most feedstock sources are non-renewable, and waste-stream should be minimised anyway. In addition reactions, which are atom-efficient, all atoms of the reagent are incorporated into the product, whereas in an elimination reaction, atom-inefficient, waste is produced. For example, fine chemicals and pharmaceuticals manufacture normally involves many steps and lots of waste chemicals, so is atom-inefficient. Ibuprofen production has many steps and only 40% atom efficiency. A newer 3-step process has been introduced, whereby the catalyst, although hazardous, can be recovered. Overall, atom efficiency is at least 80% if acetic acid is recovered, or 99% if it is.

A catalyst is not incorporated into the product and is ideally not affected by the reaction, although this does not always happen. In theory, catalysts can be reused and do not contribute to waste. Furthermore, if the activation energy is lower, a lower temperature pressure with less energy cost is allowed. Catalysts can activate the use of greener reagents, or less reactive chemicals. For example, in the pulp and paper industry, chlorine is employed as an oxidant to bleach pulp. Toxic chlorinated organic by-products are produced (for environmental workers, etc.). A new alternative is to use hydrogen peroxide instead, which must be activated but can achieve an efficient process. An iron catalyst is developed to activate H2O2 for pulp bleaching in water between 0-90degsC (so high temperature is not required). This process prevents waste, generates less toxic substrates, and the less aggressive reagent becomes usable. This is not yet commercially viable large-scale, because industrial processes must be replaced, so there must be an economic advantage to the greener process.

Unnecessary derivitisation (use of blocking groups, protection/deprotection, and temporary modification of physical/chemical processes) should be minimised or avoided if possible, because such steps require additional reagents and can generate waste.

Water can be used instead of inorganic solvents, with the advantage of being non-toxic, naturally occurring and therefore cheap, and non-flammable. However, distillation is energy intensive, contaminated waste streams may be hard to treat, the reagent must be chosen or modified to be water-soluble, and water is hard to heat and cool rapidly because of its high specific heat capacity. Water is used in adipic acid synthesis, but the yield is low and a KHSO5 oxidant is used (preferably, it would be replaced by O2), and the RUPCS catalyst needs to be optimised, so industrial application is unrealistic.

In the catalytic oxidation of alcohols, a CrO5 oxidant is used with chlorinated hydrocarbon solvents, producing chromium waste. A relatively high yield (80-90%) can be achieved by using an O2 oxidant and H2O solvent, with a soluble palladium complex catalyst. This is more environmentally suitable but takes a long time at high pressure and temperature.

Biphasic reactions can be alternatives to solvents, e.g. in homogeneous catalysis, because the catalyst and products can locate in different phases so they are easy to separate; separation is important as homogeneous catalysts are often expensive heavy/precious metals. The catalyst dissolves in solvent A, and the reagent is chosen to dissolve in solvent B; when they are heated, they are single A+B phase, and after cooling are separated into B + products, and A + catalyst. An example is fluorous phase (containing fluorinated compounds), where F atoms interact poorly with other atoms since it is so electronegative and difficult to polarise, so a fluorinated solvent will only dissolve high-fluorinated molecules.

Supercritical fluid is a fluid that has been heated and compressed above its critical point. SCF has a density similar to liquid, but mass transport of solutes is superior, giving it favourable properties as a solvent. The atoms within move more rapidly, like a gas; atoms bump into each other more often, so the reaction is more efficient. SCFs avoid gradual evaporation of hydrocarbons into the environment, have rapid reactions due to low viscosities, extraction is selective to an extent by control of density of the SCF, by varying pressure or temperature, and by tuning to have certain properties, and separation of SCF from product is easy by changing the pressure, and solvent residues in product are benign (which is especially important for food products). A problem is that there is low solubility of catalysts and substrates, and high pressure is expensive. In the future, specifically designed catalysts and reactions with gases (which have high solubility at high pressure) may be used.

An example is SC-CO2: a non-toxic, environmentally benign, non-flammable, and abundant so cheap supercritical fluid with low critical temperature and pressure. Another example is SC-H2O, which has a high critical temperature and pressure, so is more expensive, and also corrosive to steel containers. Otherwise it is environmentally useful, although it decomposes organic compounds at high temperature and pressure.

Supercritical fluids are only sometimes able to replace organic solvents. Solvent extraction is used commercially for decaffeination of coffee beans, extraction of hops for beer, and production of many plant extracts. There are about sixty SCF extraction plants around the world.

Energy requirements of chemical processes should be recognised for their environmental impacts and should be minimised; if possible, synthetic methods should be conducted at ambient temperature and pressure. A raw material, or feedstock, should be renewable rather than depleting whenever technically and economically practicable, e.g. by using biomass energy.

Biomass energy encompasses energy derived from living matter such as field crops, trees, and water plants; also agricultural and forestry wastes and solid organic wastes e.g. sewage sludge (methane gas from sewage sludge is used to power biogas generators). The characteristics of an ideal energy crop are: high yield, low energy input to produce, composition with the least contaminants, and low nutrient requirement. Biomass energy only contributes 1% to the global energy requirements.

Pyrolysis conversion to liquid fuels is carried out in the absence of oxygen, yielding low molecular weight degradation products very similar to crude oil, refined using similar processes. The chemical is corrosive, acidic and thermally unstable, and contains 20-25% water, 25-3% insoluble lignin, and smaller quantities of organic acids, which are not useful. Bioethanol from fermentation of sugars and starch is often mixed with gasoline; a major advantage is the potential reduction of CO from vehicle emissions, but clogging of engines is common. Methane converted to gaseous fuels via thermal gasification or anaerobic digestion of energy crops and organic wastes can then be piped for domestic heating, combusted in gas fired power plants to produce electricity, or converted to methanol for use in internal combustion engines. A major limitation is the ncomplete conversion of biomass to ethane (only 50%). In theory, biomass and waste conversion to methane could generate about 20% of our global energy requirements per year.

Environmental cost is associated with the use of energy to power a chemical reaction. Catalysis can be used to reduce energy requirements, and alternative sources of energy can be explored that may influence selectivity, yield, etc. of a reaction and energy may be more directly targeted to reagents rather than the surroundings, allowing more efficient energy use. Some alternative methods of powering chemical reactions are photocatalysis, ultrasound and microwaves.

Photocatalysis involves electromagnetic waves, with light as the energy source, and energy being introduced in the form of an excited state pf a reagent or catalyst. This can lead to possible changes in the selectivity of reactions and may minimise the environmental cost of powering the reaction by using sunlight as the energy source.

Ultrasound involves acoustic waves which are not directly absorbed by the molecules, with irradiation of a reaction with ultrasound leading to a process known as cavitation. Sound is transmitted as a wave with alternating compression and rarefaction cycles. During rarefaction the negative pressure can overcome intermolecular forces binding the fluid together. Fluid is torn apart creating cavitation bubbles, and the succeeding compression cycle causes the bubbles to collapse with release of large amounts of energy. Local temperatures of 5000K and pressures of 1000atm can be caused by the collapse and this is then followed by very fast cooling. General rate and yield improvements can occur through bond cleavage/free radical formation (since bonds are torn apart so easily), shock waves causing mechanical effects, intense mixing, some heating, emulsion formation, fragmentation of solids, accelerated mass transport. The outcome of reactions can b altered with, in general, free radical processes enhanced and polar processes left unaffected.

Selective absorption of microwave energy by polar molecules can give heating of up to 100degsC per second. Reactions can be carried out in polar solvents and this gives rapid superheating of the solvent even to above boiling point. There can be some disadvantages of this approach: high pressures can be developed and sealed containers are needed. Solid-state reactions can be carried out – organic compounds absorbed on the surface of inorganic oxide (alumina, silica, clay); only the organic compound absorbs microwaves leading to local heating and relatively low bulk temperature. There is no need for high pressure or sealed vessels.

Chemical products should be designed so that at the end of their function they break down into innocuous degradation products and do not persist in the environment. Analytical methodologies need to be further developed to allow for real-time, in-process monitoring and control prior to the formation of hazardous substances. Substances and the form of a substance should be chosen to minimise potential for chemical accidents, including releases, explosions and fires.