Effects on Microorganisms

Organomercurials - particularly the alkyl- and arylmercury compounds - are more active as bactericides or fungicides than the inorganic salts. Phenylmercury acetate prevents the growth of a variety of fungi in vitro at concentrations of approximately 0.125 mg L whereas ethylmercury salts are active at 0.05 mg In contrast, mercuric acetate or chloride are active at 1.0 mg L . The difference may partly be attributed to lipid solubility, where penetra- 

In aquatic plants adverse effects of mercury such as senescence, growth inhibition, decreased chlorophyll, protein and RNA content, inhibited catalase and protease activities, inhibited and abnormal mitotic activity, increased free amino acid content, discoloration of floating leaves, leaf and root necrosis, and death have been reported (Muramoto and Oki 1984, Mhatre and Cha-phekar 1985, Sarkar and Jana 1986). The level of mercury that results in toxic effects in aquatic plants varies greatly. Freshwater concentrations of between 50 and 3400 pg Hg or 0.8 to 6 pg methyl-mercury are toxic to plants, and for salt water 10 pg Hg for algae and 160 pg Hg for seaweed are reported. No data are available on methylmercury in saltwater plants (EPA 1997). 

Sublethal effects on terrestrial plants include decreased growth, leaf injury, root damage, inhibited root growth and function, hampered nutrient uptake, chlorophyll decline and reduced photosynthesis (Schle-gel etal. 1987, Linqvist 1991, Godbold 1991). Again, methylmercury is more toxic than Hg . 

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Mathur, S.P., H.A. Hamilton, R. Greenhalgh, K.A. Macmillan, and S.U. Khan. 1976. Effect on microorganisms and persistence of field-applied carbofuran and dyfonate in a humic mesisol. Canad Jour. Soil Sci. 56 89-96. 

Here we will describe the methods that are used to derive critical limits for soil, based on direct ecotoxicological effects on microorganisms and plants. The indirect approaches (food web models) to derive critical limits for soil based on critical limits for terrestrial fauna such as MPC values for target organisms will be also considered. 

Electrolysis has the potential advantage that a metal can be recovered in its most valuable forms as metal film or powder and sold or recycled to the process. Cf. also Walsh, Ref. [133]. Heavy metals, such as copper from metal complex dyes, or from catalysts in industrial effluents, have become a problem in clarification plants because of their toxic effects on microorganisms. Their disposal through deposition after chemical or physical treatment is senseless,... 

Environmental risk assessment examines the potential adverse effects to ecosystems from exposure of the aquatic, terrestrial and air components. Initial assessment normally focuses on the aquatic compartment, including effects on microorganisms in waste water treatment plants. This first tier risk assessment can be extended to cover the sediment part of the aquatic compartment and the soil compartment. At higher tonnage levels, effects relevant to the food chain are evaluated, i.e., secondary poisoning. Diderich in Chapter 8 of (73) discusses the principles of EU environmental risk assessment. 

Our laboratory first called attention to the bacterial effects of the simpler complexes in 1965. Over the next few years, in cooperative studies with microbiologists, a number of papers were published describing a multiplicity of effects on microorganisms caused by various complexes of platinum group metals platinum, palladium, ruthenium, rhodium, osmium, and iridium. 

While these experiments stimulated other research, it is sad to relate that the proposed explanation is not correct. It required almost seventy years, however, before it was realized that the curare-like action of the onium salts was a result of their ionic character. Other examples of the role of spatial arrangement were discovered. For example, quoting Stewart Ishizuka (1897) found that maleic acid was a much stronger poison than its stereoisomer, fumaric acid 1.94 grammes for every kilogramme in a dog s weight was a fatal dose of the former acid, while the same dose of fumaric acid was harmless. Similarly these isomers were found to have differential effects on microorganisms. Stewart also rationalized the mydriatic action of tropine and the inactivity of pseudotropine in terms of three-dimensional formulae as shown below (1 and 2). In many ways, these structural representations are close to the present-day conformational structures (pseudotropine = 3, tropine = 4) ... 

Some organic acids have no inhibitory effect on microorganisms for example, gluconic acid is a highly polar molecule, and is unable to penetrate the cell membrane of E. coli 0157 H7 (Bjornsdottir, Breidt, Jr., and McFeeters, 2006). A tolerance response in Salmonella enterica sv. Typhimurium, induced by lactic acid, will, however, induce sensitivity to hydrogen peroxide (Greenacre et al., 2006). 

For more information on the use of high-pressure processing and its effect on microorganisms, the reader is referred to Chapter 5. 

An Environmental Impact Report is also required for a notification. This is an assessment of the environmental compatibility made by the notifier, and is based on an evaluation of degradation, accumulation and mobility in the environment, effects on microorganisms, plants, animals and ecosystems and long-term indirect effects on humans via the environment. 

Some empirical uses of S. sclarea suggest that its essential oil, like many essential oils of the Lamiaceae family, has an inhibitory effect on microorganisms pathogenic to man. Ulubelen et al. [51] examined the antimicrobial activity of some diterpenes and sesquiterpenes found in an acetone extract of S. sclarea. They found that 2, 3-dehydrosalvipisone, sclareol, manool, 7-oxoroyleanone, spathulenol and caryophyllene oxide were active against Staphylococcus aureus 2, 3- dehydrosalvipisone and manool were active against Candida albicans and caryophyllene oxide was active against Proteus mirabilis. 

Terrazole has also an inhibiting effect on microorganisms active in the nitrification process (i.e., the conversion of ammonium salts to nitrates) in soil.486-"488 However, under field conditions, the inhibition of nitrification is of limited duration pasture yields, for example, are not increased.489 3-Trichloromethyl-l,2,4-thiadiazole-5-amines exhibit the same properties 490... 

Effects on Microorganisms and Plants Copper is toxic to many bacteria and viruses (Stauber 1995). For example, in cultures of... 

Waste Products and Recycling No chemotoxic or radiotoxic effects on microorganisms or plants are known from exposure to environmental radioactivity from natural and industrial sources of uranium, thorium and their decay products. 

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