Environmental complexation effects

The Natural Resources Defense Council (NRDC) report Intolerable Risk Pesticides in Our Children s Food focused on the increased risk of the adverse effects of pesticides on children. This was in part because of the smaller size of the child relative to the adult and because of different food consumption practices. Relative to their size, children eat, drink, and breathe more than adults in part because they are growing. The use and regulation of pesticides illustrate the complexities of risk analysis and risk management and the difficulties in determining an acceptable level of exposure with acceptable risks. In the United States approximately 1 billion pounds of pesticides (with about 600 different active ingredients) are used annually in the agricultural sector, and worldwide approximately 4 billion pounds are used. There are a range of human health and environmental health effects associated with the use of pesticides. 

Krech, D., Rosenzweig, M. R., and Bennett, E. L. "Effects of Environmental Complexity and Training on Brain Chemistry," Journal of Comparative and Physiological Psychology 53, 509-19, i960. 

The focus of this chapter is the response of microbial cultures to dc fields. The results showed that dc electric field intensity tends to have a complex effect on the activity of mixed microbial cultures. Anaerobic cultures seem to experience an "environmental shock" when exposed to electric field intensities greater than 1.5 V/cm. However, these cultures are able to recover their activities once the electric currents are switched off. Aerobic cultures did not seem to be affected by exposure to field intensities less than 0.28 V/cm. Higher dc field intensities, up to 1.14 V/cm, seem to stimulate aerobic cultures during the first 24 hours of exposure. However, continuous exposure to dc fields (in the range of 1.14 V/cm) following the first 24 hours seems to retard the growth of aerobic cultures. The authors identify the need for further evaluation and assessment of the impact of dc fields on the physicochemical and biochemical interactions in porous media. 

Onken, B.M. and Traina, S.J. 1997. The sorption of nonionic organic solutes to humic acid-mineral complexes effect of cosolutes. Journal of Environmental Quality, 26 132-8. 

In recent years, considerable efforts have been made in a variety of research groups to bridge the pressure and material gap and to experimentally as well as theoretically establish the new methods required to continuously vary the conditions starting form the model catalyst side (bottom up approach) or form the real catalyst side (top down approach). First examples support the importance of a detailed understanding of environmental and material complexity effects on catalytic reactions. The common distinction of pressure gap and material gap as depicted in Fig. 1.54 might, however, also be oversimplified as has been demonstrated in a recent contribution on the oxidation of CO on a ruthenium surface. The first step in this reaction consists in an... 

Olah GA, Mathew T, Goeppert A et al (2005) Ionic liquid and solid HF equivalent amine-poly(hydrogen fluoride) complexes effecting efficient environmentally friendly isobutane-isobutylene alkylation. J Am Chem Soc 127 5964—5969... 

In order to take into account the heterogeneous nature of the surroundings around the guest molecule in the a-CD inclusion-complex, a more realistic solvaton model was constructed. It was assumed that the a-CD cavity has the environmental(solvent) effect of dielectric constant on the included part of the guest molecule, while the other part of the guest is exposed to the aqueous layer of dielectric... 

These comments deal with environmental levels likely to produce toxic responses at the indicated species level. The focus has been on the probability of risk groups undergoing ecotoxic responses, mainly for comparative purposes. We do not deal with complex effects that may be expressed at low lead exposures in systems and populations, or interplays between relatively larger groupings that occur or may occur because certain populations are reduced, directly or indirectly, by changes in environmental compartment levels of lead. Lead readily accumulates in sediments so that there may be different sedimentary populations that relate to that lead accumulation more detrimentally than others. This topic of subtle, large-scale ecotoxic effects as an aspect of concern largely unknown in the lead literature is presented in WHO s 1989 report on the ecotoxicity of lead (WHO, 1989) and sections of the current EPA Pb criteria document (U.S. EPA, 2006). 

Solomatin SV et al (2003) Environmentally responsive nanoparticles from block ionomcr complexes effects of pH and ionic strength. Langmuir 19 8069-8076. doi 10.1021/ la0300151... 

West, R. W. and Greenough, W. T. (1972). Effect of environmental complexity on cortical synapses of rats Preliminary results. Behav. Biol, 7, 279-284. 

New information is constantly forthcoming. For example, approximately 600-700 DBFs have been identified in drinking water disinfected by chlorine, ozone, chlorine dioxide, chloramines, and their combinations, with new ones being discovered all the time [16]. Such complexity demonstrates the difficulty associated with trying to ascribe the causes of environmental toxic effects when people come down with strange illnesses and reactions. An example is increased rates of spontaneous abortions in women who drink water with elevated levels of THMs and other DBFs (Chapters 8 and 23). The mixture possibilities in disinfected water, for example, are endless and the exact causes of toxic consequences are extremely difficult to pin down. 

Complexing Effects on Behavior of Some Metals. K. A. Daum and L. W. Newland The Disposition and Metabolism of Environmental Chemicals by Mammalia. 

The chronic aquatic effects which relate silver speciation to adverse environmental effects were studied on rainbow trout eggs and fry. The maximum acceptable toxicant concentration (MATC) for silver nitrate, as total silver, was reported to be 90—170 ng/L (43). Using fathead minnow eggs and fry, the MATC, as total silver, for silver thiosulfate complexes was reported as 21—44 mg/L, and for silver sulfide as 11 mg/L, the maximum concentration tested (27). 

Free ionic silver readily forms soluble complexes or insoluble materials with dissolved and suspended material present in natural waters, such as sediments and sulfide ions (44). The hardness of water is sometimes used as an indicator of its complex-forming capacity. Because of the direct relationship between the availabiUty of free silver ions and adverse environmental effects, the 1980 ambient freshwater criterion for the protection of aquatic life is expressed as a function of the hardness of the water in question. The maximum recommended concentration of total recoverable silver, in fresh water is thus given by the following expression (45) in Fg/L. 

Many factors affect the mechanisms and kinetics of sorption and transport processes. For instance, differences in the chemical stmcture and properties, ie, ionizahility, solubiUty in water, vapor pressure, and polarity, between pesticides affect their behavior in the environment through effects on sorption and transport processes. Differences in soil properties, ie, pH and percentage of organic carbon and clay contents, and soil conditions, ie, moisture content and landscape position climatic conditions, ie, temperature, precipitation, and radiation and cultural practices, ie, crop and tillage, can all modify the behavior of the pesticide in soils. Persistence of a pesticide in soil is a consequence of a complex interaction of processes. Because the persistence of a pesticide can govern its availabiUty and efficacy for pest control, as weU as its potential for adverse environmental impacts, knowledge of the basic processes is necessary if the benefits of the pesticide ate to be maximized. 

Industrial solvent appHcations are broad, varied, and complex and each has its own set of characteristics and requirements. Proper solvent selection and blend development have a large impact on the success of the operation in which the solvent is used, from the perspectives of economic effects, technical adequacy, safety issues, and environmental impacts. 

---