Soils environmental fate

Figure 16-1 and 16-2 present the decision networks that guide contaminant release screening analysis. Figure 16-1 deals with contaminants in or under the soil and Fig. 16-2 addresses aboveground wastes. Any release mechanisms evident at the site will require a further screening evaluation to determine the likely environmental fate of the contaminants involved. 

If areas identified as likely to receive significant atmospheric contaminant concentrations include areas supporting edible biota, the biouptake of contaminants must be considered as a possible environmental fate pathway. Direct biouptake from the atmosphere is a potential fate mechanism for lipophilic contaminants. Biouptake from soil or water following transfer of contaminants to these media must also be considered as part of the screening assessments of these media. 

Fig. 16-5. Environmental fate screening Jccision nt-i -s urk soils and ground water.

Environmental Fate. Ammonia combines with sulfate ions in the atmosphere and is washed out by rairtfall, resulting in rapid return of ammonia to the soil and surface waters. Ammonia is a central compound in the environmental cycling of nitrogen. Ammonia in lakes, rivers, and streams is converted to nitrate. 

Environmental Fate. A portion of releases to land and water will quickly evaporate, although some degradation by microorganisms will occur. Xylene are moderately mobile in soils and may leach into groundwater, where they may persist for many years. Xylenes are VOCs. As such, xylene will react with other atmospheric components, contributing to the formation of ground-level ozone and other air pollutants. 

Environmental Fate. Most of the MEK released to the environment will end up in the atmosphere. MEK can contribute to the formation of air pollutants in the lower atmosphere. It can be degraded by microorganisms living in water and soil. 

The environmental fate of DATS has been the subject of extensive research efforts. The results from these studies show that DATS is mineralized in aquatic environments and in soils at rates sufficient to prevent accumulation [23-25]. 

Methyltins are less likely than the butyl- and octyl-tins to partition to sediments, soils, and organic carbon. Modelled data for K c suggest much lower capacity for binding to organic carbon than do measured values, often by several orders of magnitude. Measured data have been used in preference to model environmental fate of the compounds. The compounds also bind strongly to clay minerals, montmorillonite in particular. 

Environmental Fate. Endosulfan partitions to the atmosphere and soils and sediments. It is transported in the atmosphere (Gregor and Gummer 1989 Strachan et al. 1980), but it is immobile in soils (Bowman et al. 1965 El Beit et al. 1981c Hodapp and Winterlin 1989 Stewart and Cairns 1974). 

In Chapter 3, the distribution of enviromnental chemicals through compartments of the gross environment was related to the chemical factors and processes involved, and models for describing or predicting environmental fate were considered. In the early sections of the present chapter, the discnssion moves on to the more complex question of movement and distribntion in the living environment— within individuals, communities, and ecosystems—where biological as well as physical and chemical factors come into play. The movement of chemicals along food chains and the fate of chemicals in the complex communities of sediments and soils are basic issues here. 

Harvey J, JJ Dulka, JJ Anderson (1985) Properties of sulfometuroin methyl affecting its environmental fate aqueous hydrolysis and photolysis, mobility and adsorption on soils, and bioaccumulation potential. J Agric Food Chem 33 590-596. 

An appropriate mineral medium supplemented with the organic compound that is to be studied is inoculated with a sample of water, soil, or sediment. In studies of the environmental fate of a xenobiotic in a specific ecosystem, samples are generally taken from the area putatively contaminated with the given compound so that a degree of environmental relevance is automatically incorporated. Attention has, in addition been directed to pristine environments, and the issues of adaptation or preexposure have already been discussed. 

Environmental fate Persistence - P Soil or sediment >1 80 Soil, sediment >50 to Soil, sediment 30 to Soil, sediment <30 days... 

---