Biodegradation in soils and sediments

In summary, bioavailability strongly affects CP biodegradation in soil and sediments. The partitioning of CPs to water-saturated subsurface solids also affects groundwater bioremediation. The organic content of the solid matrix increases the unavailability of CPs to biodegradation. 

Ten of the 23 plastieizers can be expected to biodegrade in soil and sediments to some extent, bnt there were too few data available to make quantitative generahzations. Limited studies suggested that tri-(2-ethylhexyl) trimelhtate and di-(2-etliylhejqrl) seba-cate may be relatively persistent in soil. The biodegradation of ditridecyl phthalate, diun-... 

Potential Influences of Polymers during and after Biodegradation in Soil and Sediment... 

There are no procedures for estimating the rate of biodegradation of chemicals because of the complexity of the biochemical reactions, and the diverse experimental conditions imposed in individual investigations. The potential for even the more common imidazolium-based ionic liquids to biodegrade in soils and sediments remains unresolved. 

In soil and sediments, methyl parathion adsorbs to soil and is expected to display moderate mobility (EPA 1980c). The major degradation process of methyl parathion in soil is biodegradation by microbes (Badway and El-Dib 1984). Degradation by hydrolysis has been observed to occur at higher temperatures... 

Mihelcic JR, Lueking DR, Mitzell RJ, Stapleton JM (1993) Bioavailability of sorbed- and separate-phase chemicals. Biodegradation 4 141-153 National Research Council (2003) Bioavailability of contaminants in soils and sediments processes, tools, and applications. The National Academies Press, Washington DC, USA... 

Chlordecone is similar to mirex in structure and is also highly persistent in soils and sediments (halflife expected to be analogous to 10 years duration for mirex) because of its resistance to biodegradation, although some microbial metabolism of chlordecone has been reported (Lai and Saxena 1982 Ordorff and Colwell 1980). No evidence of microbial degradation was detected for chlordecone exposed to hydrosoils from a reservoir (not previously contaminated with chlordecone) and from Bailey Creek (contaminated with chlordecone) under either anaerobic or aerobic conditions for 56 days (Huckins et al. 1982). 

The reduction of sulfone to either sulfoxide or sulfide (i.e., disulfoton) was not observed under the same conditions. Since the bacterial populations in sediments and soils are higher than in typical surface waters (Mossman et al. 1988), biodegradation is expected to play a major role in the loss of disulfoton in soil and sediment, as occurred in the disulfoton spill in the Rhine River (Capel et al. 

The hydrochloric acid salt of 3,3 -dichlorobenzidine readily photolyses in water exposed to natural sunlight, but may not readily biodegrade in soil and aeelimated sludges. It has a strong tendency to partition to soils and sediments, a property which reduces the potential for human exposure (Boyd et al. 1984 Chung and Boyd 1987 Sikka et al. 1978). Once partitioned to soil, the compound apparently binds further with humie substances to form humie-like materials that presumably would be non-hazardous (Sikka et al. 1978). However, in a recent paper, Nyman et al. (1997) stated that dehalogenation of 3,3 -dichlorobenzidine to form benzidine (also a toxie substance) occurs in sediment/water mixtures under anaerobic conditions. 

Harkness, M. R. Bergeron, J. A. (1990). Availability of PCBs in soils and sediments to surfactant extraction and aerobic biodegradation. In Ninth Progress Report for the Research and Development Program for the Destruction of PCBs, pp. 109-20. Schenectady, NY General Electric Co. Corporate Research and Development. 

Radium in soils and sediment does not biodegrade nor participate in any chemical reactions that transform it into other forms. The only degradation mechanism operative in air, water, and soil is radioactive decay. Radium has 16 known isotopes (see Chapter 3), but only 4 occur naturally (Radium-223, -224, -226, and -228). The half-life of radium-226 is 1,620 years. The half-lives of radium- 228, radium-223, and radium-224 are 5.77 years, 11.4 days, and 3.64 days, respectively. 

Furan may be released to the environment as a waste industrial product or from unintentional, accidental releases. If released to soil it is expected to volatilize. If released to water, furan is not expected to adsorb to suspended particles and sediment and is likely to volatilize to ambient air. Sulfate-reducing bacteria can degrade furan. However, under non-sulfate-red-ucing conditions, biodegradation in soil and water is expected to be slow. In the air, furan will exist as a vapor and will be subject to degradation by reacting with hydroxyl radicals. 

Pentachlorobenzene is persistent and immobile in soil and sediment. Volatilization, adsorption, photooxidation, and aerobic biodegradation primarily control the fate of pentachlorobenzene in the environment. Bioaccumulation in the food chain may occur. 

Screening tests for biodegradability indicate that theophylline may be biodegradable in soil and water. The adsorption of theophylline to suspended solids and sediments in water and to soil should be unimportant. The estimated bioconcentration factor indicates that bioconcentration of theophylline in aquatic organisms should not be important. 

Biodegradation has been shown to occur under both aerobic and anaerobic conditions and is a major degradation process for PCBs in soil and sediment, as reviewed by Higson (1992), Robinson and Lenn (1994), Bedard and Quensen (1995), and most recently by Wiegel and Wu (2000). While photolysis of PCBs from soil surfaces may also occur, and PCBs may also undergo base-catalyzed dechlorination (Chiarenzelli et al. 1995 Taniguchi et al. 1997), neither of these processes is likely to be a significant removal mechanism in soil and sediment. 

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