Persistence in soil

Urea and uracil herbicides tend to be persistent in soils and may carry over from one season to the next (299). However, there is significant variation between compounds. Bromacil is debrominated under anaerobic conditions but does not undergo further transformation (423), linuron is degraded in a field soil and does not accumulate or cause carryover problems (424), and terbacd [5902-51-2] is slowly degraded in a Russian soil by microbial means (425). The half-hves for this breakdown range from 76 to 2,475 days and are affected by several factors including moisture and temperature. Finally, tebuthiuron apphed to rangeland has been shown to be phytotoxic after 615 days, and the estimated time for total dissipation of the herbicide is from 2.9 to 7.2 years (426). 

Butler LC, Staiff DC, Davis JE. 1981a. Methyl parathion persistence in soil following simulated spillage. Arch Environ Contam Toxicol 10 451-458. 

Stewart DKR, Cairns KG. 1974. Endosulfan persistence in soil and uptake by potato tubers. J Agric Food Chem 22 984-986. 

The general picture, then, is that pyrethroids are reasonably persistent in soils and sediments but not to the same degree as OC compounds such as dieldrin and p,p -DDE. They do undergo bioconcentration from water by fish and other aquatic... 

An environmental protocol has been developed to assess the significance of newly discovered hazardous substances that might enter soil, water, and the food chain. Using established laboratory procedures and C-labeled 2,3,7,8-tetra-chlorodibenzo-p-dioxin (TCDD), gas chromatography, and mass spectrometry, we determined mobility of TCDD by soil TLC in five soils, rate and amount of plant uptake in oats and soybeans, photodecomposition rate and nature of the products, persistence in two soils at 1,10, and 100 ppm, and metabolism rate in soils. We found that TCDD is immobile in soils, not readily taken up by plants, subject to photodecomposition, persistent in soils, and slowly degraded in soils to polar metabolites. Subsequent studies revealed that the environmental contamination by TCDD is extremely small and not detectable in biological samples. 

Most phytoactive compounds do not persist in soil in a free and active form for very long, yet they have been plausibly implicated, for example, in a mechanism of infection or nutrient acquisition therefore some suitable explanation must be found. The right set of circumstances was invoked by Uren and Reisenauer (17) to explain how labile reducing agents may be protected physically from Oi and be directed toward insoluble oxides of Mn. The right set of circumstances may have relevance in other situations, and some po.ssibilities are discussed later in this chapter. 

Root products may be classified into types on the basis of their (1) chemical properties, such as composition, solubility, stability (e.g., hydrolysis, oxidation), volatility, molecular weight etc. (2) site of origin and (3) e.stablished, not just perceived, functions. The chemical properties determine in turn their biological activity and how the compounds will behave in soils their persistence in soil is very much an outcome of their chemical behavior, particularly sorption and their biodegradability. 

Undergoes photolysis in water rapidly. The compound is stable to photolysis in soil and is relatively persistent in soil, with a field half-life (ti/2) of 121 days in sandy soil and fi/2 of 302 days in clay soil. 

The polar character of neonicotinoids makes them, in general, potentially mobile in soil. Acetamiprid and nitenpyram have short soil persistence. Imidacloprid and thi-amethoxam, however, are sufficiently persistent in soil to be used for soil treatment. The definition of soil residues for the various neonicotinoid compounds except for imidacloprid are the parent compound and it metabolites. The metabolites of acetamiprid are lM-1-2, lM-1-4 and lC-0 (Figure 6). The metabolites of nitenpyram are 2-[N-(6-chloro-3-pyridyl-methyl)-A-ethyl]amino-2-methyliminoacetic acid (CPMA) and A-(6-chloro-3-pyridylmethyl)-Ai-ethyl-A -methylformamidine] (CPMF). 

Persistency Very persistent in soil and water and on surfaces. 

The aliphatic components of SOM, derived from various sources, tend to persist in soil (Almendros et al. 1998 Lichtfouse et al. 1998a Lichtfouse et al. 1998b Mosle et al. 1999 Poirier et al. 2000). The principal source of aliphatic materials in soil is plant cuticular materials, especially cutin, an insoluble polyester of cross-linked hydroxy-fatty acids and hydroxy epoxy-fatty acids (Kolattukudy 2001). Some plant cuticles also contain an acid and base hydrolysis-resistant biopolymer, comprised of aliphatic chains attached to aromatic cores known as cutan (Tegelaar et al. 1989 McKinney et al. 1996 Chefetz 2003 Sachleben et al. 2004). 

Park J-H, Feng Y, Ji P, Voice TC, Boyd SA (2003) Assessment of bioavailability of soil-sorbed atrazine. Appl Environ Microbiol 69 3288-3298 Pignatello JP, Sawhney BL, Frink CR (1987) EBD persistence in soil. Science 236 898... 

DDT and some of its breakdown products are relatively resistant to breakdown by enzymes and higher organisms found in the soil and are therefore highly persistent in soil, sediment and biota [54]. Despite significant reduction in the use of DDT in the Ebro since the 1960s, DDT still continues to cycle in the ecosystem, with high levels widely detected in both sediments and fish [47, 51, 52]. 

In terrestrial ecosystems, atrazine effectively inhibits photosynthesis in target weeds and can also affect certain sensitive crop plants. Atrazine metabolites are not as phytotoxic as the parent compound. Degradation is usually rapid, although atrazine can persist in soils for more than one growing season. Soil fauna may be adversely affected shortly after initial atrazine application at recommended levels, but long-term population effects on this group are considered negligible. 

Chlordanes and their metabolites are ubiquitous in the environment at low concentrations, but at a high occurrence in samples analyzed. Atmospheric transport is considered to be the major route of global dissemination. Some chlordane isomers persist in soils for 3 to 15 years, although there seems to be little accumulation of chlordanes by crop plants grown in these soils. Lengthy persistence of various chlordane isomers, especially m-chlordane and trans-nonachlor, has been reported in certain organisms, but this has varied greatly between species and tissues. 

Table 17.2 (continued) Diflubenzuron Persistence in Soil and Water... 

Toxaphene is persistent in soils, water, and other environmental compartments, with residence times measured in years. 

Histoplas-mosis Aerosol No High 1-2 weeks Weeks Low Persistence in Soil No... 

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). 

Organophosphates (Fig. 10, Table 3) are more toxic than chlorinated hydrocarbons, in particular to humans,but they exhibit lower persistence in soils and do not seem to accumulate in soil fauna or concentrate in birds and fish [74]. This behavior is also related to an enhanced water solubility and lower vapor pressure of organophosphates. Malathion and Parathion (Fig. 10, Table 3) insecticides are known to be chemically hydrolyzed and biodegraded by micro-... 

As a result of its persistence in soil and groundwater, and past widespread use as a gasoline additive and fumigant, 1,2-dibromoethane has been detected in ambient air, soils, groundwater, and food. However, most of the monitoring data reported in this section, although the latest available, are not current. Volatilization is the most important removal process for 1,2-dibromoethane released to surface waters. Since only a small fraction of the compound is sorbed to soil, sorption to sediment and subsequent persistence in sediment is not expected to be an important process in the removal of 1,2-dibromoethane from the environment. The data may reflect ambient concentrations of a decade or more ago, but because of the phaseout of the use of leaded gasoline and the ban on... 

DDT is very persistent in soil. The percentage of the initial dosage (1 ppm) remaining after 8 wk of incubation in an organic and mineral soil were 76 and 79%, respectively, while in sterilized controls 100 and 92% remained, respectively (Chapman et al., 1981). 

Soil. Dieldrin is very persistent in soil under both aerobic and anaerobic conditions (Castro and Yoshida, 1971 Sanborn and Yu, 1973). Half-lives in soil ranged from 175 d to 3 yr (Howard et al, 1991 Jury et al., 1987). 

Persistence in soil is approximately 6 to 10 wk (Hartley and Kidd, 1987) but is moderately slower in sandy soils low in organic matter (Ashton and Monaco, 1991) and much slower under sterilized conditions. In nonsterile soils, 39-54% of the applied amount degraded after 28 d (Fang, 1983). The half-lives for alachlor in soil containing 6 and 15% moisture were 23 and 5.7 d, respectively (Walker and Brown, 1985). In a Ustollic Haplargid clay with 1.1% organic matter. 

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