Microbial degradation, in soil

Chapman RA, Tolman JH, Cole C. 1994a. The effect of multiple soil applications of disulfoton 011 enhanced microbial degradation in soil and subsequent uptake of insecticidal chemicals by potato plants. J Environ Sci Health Part B Pest Food Contamin Agric 29(3) 485-506. 

Soil. Undergoes microbial degradation in soil forming hydroxypropazine (Harris, 1967). Dealkylation of both substituted amino groups is presumably followed by ring opening and decomposition (Hartley and Kidd, 1987). Under laboratory conditions, the half-lives of propazine in a Hatzenbiihl soil (pH 4.8) and Neuhofen soil (pH 6.5) at 22 °C were 62 and 127 d, respectively (Burkhard and Guth, 1981). 

Microbial degradation in soils is greatest for the aromatic fractions of fuel oils, while the biodegradation of the aliphatic hydrocarbons decreases with increasing carbon chain length. Evaporation is the primary fate process for these aliphatics (Air Force 1989). 

Lewisite in soil may rapidly volatilize or may be converted to lewisite oxide due to moisture in the soil (Rosenblatt et al, 1975). The low water solubility suggests intermediate persistence in moist soil (Watson and Griffin, 1992). Both lewisite and lewisite oxide may be slowly oxidized to 2-chlorovinylarsonic acid (Rosenblatt et al, 1975). Possible pathways of microbial degradation in soil include epoxidation of the C=C bond and reductive deha-logenation and dehydrohalogenation (Morrill et al, 1985). Due to the epoxy bond and arsine group, toxic metabolites may result. Additionally, residual hydrolysis may result in arsenic compounds. Lewisite is not likely to bioaccumulate. However, the arsenic degradation products may bioaccumulate (Rosenblatt et al, 1975). 

Its half-life is less than 3 and 6 days under aerobic and anaerobic conditions, respectively. CO2 is the major metabolite following microbial degradation in soil. 

Biotic and abiotic degradation in water microbial degradation in soil (half-life approx. 5-6 weeks). 

Soil. Propanil degrades in soil forming 3,4-dichloroaniline (Bartha, 1968, 1971 Bartha and Pramer, 1970 Chisaka and Kearney, 1970 Duke et al., 1991) which degrades via microbial peroxidases to 3,3, 4,4 -tetrachlorazobenzene (Bartha and Pramer, 1967 Bartha, 1968 Chisaka and Kearney, 1970), 3,3, 4,4 -tetrachloroazooxybenzene (Bartha and Pramer, 1970), 4 (3,4-dichloroanilo)-3,3, 4,4 -tetrachloroazobenzene (Linke and Bartha, 1970), and l,3-bis(3,4-dichloro-phenyl)triazine (Plimmer et al., 1970), propionic acid, carbon dioxide, and unidentified products (Chisaka and Kearney, 1970). Evidence suggests that 3,3, 4,4 -tetrachloroazobenzene reacted with... 

On, L.-T. and Street, J.J. Monomethylhydrazine degradation and its effect on carbon dioxide evolution and microbial populations in soil. Bull. Environ. Contam. Toxicol, 41(3) 454-460, 1988. 

Several processes may play a role in the environmental dissipation of -triazine herbicides. Dissipation processes can include microbial or chemical degradation in soil metabolism or conjugation in plants photodegradation in air, water, and on soil and plant surfaces and volatilization and transport mechanisms. This chapter will address photolytic degradation and abiotic hydrolysis of the currently used triazine herbicides, the triazinone herbicides (metribuzin and metamitron), and the triazinedione herbicide hexazinone. 

Reversible sorption of phenolic acids by soils may provide some protection to phenolic acids from microbial degradation. In the absence of microbes, reversible sorption 35 days after addition of 0.5-3 mu mol/g of ferulic acid or p-coumaric acid was 8-14% in Cecil A(p) horizon and 31-38% in Cecil B-t horizon soil materials. The reversibly sorbed/solution ratios (r/s) for ferulic acid or p-coumaric acid ranged from 0.12 to 0.25 in A(p) and 0.65 to 0.85 in B-t horizon soil materials. When microbes were introduced, the r/s ratio for both the A(p) and B-t horizon soil materials increased over time up to 5 and 2, respectively, thereby indicating a more rapid utilization of solution phenolic acids over reversibly sorbed phenolic acids. The increase in r/s ratio and the overall microbial utilization of ferulic acid and/or p-coumaric acid were much more rapid in A(p) than in B-t horizon soil materials. Reversible sorption, however, provided protection of phenolic acids from microbial utilization for only very short periods of time. Differential soil fixation, microbial production of benzoic acids (e.g., vanillic acid and p-hydroxybenzoic acid) from cinnamic acids (e.g., ferulic acid and p-coumaric acid, respectively), and the subsequent differential utilization of cinnamic and benzoic acids by soil microbes indicated that these processes can substantially influence the magnitude and duration of the phytoxicity of individual phenolic acids (Blum, 1998). 

---