Persistence forest soils

Lee, C.H., Oloffs, PC., and Szeto, S.Y Persistence, degradation, and movement of triclopyr and its ethylene glycol butyl ester in a forest soil, J. Agrlc. Food Chem., 34(6) 1075-1079, 1986a. 

Roy. D.N.. Konar. S.K.. Charles. D.A.. Feng. J.C.. Prasad. R.. and Campbell. R.A. Determination of persistence, movement, and degradation of hexazinone in selected Canadian boreal forest soils. J. Agric. Food Chem., 37(2) 443-447. 1989. 

Urease activity in soils has been found to reflect the bacterial count and content of organic matter. The urease isolated from an Australian forest soil (87) was crystallized and found to have a specific activity of 75 Sumner units (S.U.) per mg. The molecular weight species were estimated (sedimentation velocity) to be 42, 131, and 217 X 103. That urease activity persists in soils is shown by the finding that enzymic activities, including urease, could be demonstrated in soil samples over 8000 years old (88). 

There has been much interest in the fate of the persistent pesticides, especially DDT, in orchard soil. This subject has been reviewed by Ginsburg (4). Although most authors agree that the build-up of DDT in orchard soil is not linear with application, one recent publication (11) reports a continued accumulation of DDT in forest soils during the 3... 

Tables II and III show that downward leaching of DDT and its analogs is very slow, with less than 3% of the total residue having penetrated below the 1-foot level. The amount of o,p-DDT, p,p-DDE, and p,p-TDE [l,l-dichloro-2,2-bis(parachlorophenyl)ethane] present is expressed as a ratio with p,p-DDT in order to relatfe the soil concentrations of these analogs with their concentrations in the technical DDT originally applied. The p,p-DDT to o,p-DDT ratios range from 7 to 14 at the various soil depths analyzed, while in technical DDT the ratio is about 3. This change in relative concentration suggests that the o,p-isomer is less persistent in soil. This result is contrary to that of Woodwell and Martin (11) who found more o,p-isomer in the surface layers of forest soils exposed to DDT. The analytical methods used by these authors are not as reliable as those described here, however.

Plants readily accumulate lead from soils of low pH or low organic content however, uptake is significantly reduced after the application of lime or phosphate, which converts lead to hydroxides, carbonates, or phosphates of relatively low solubility (Demayo et al. 1982). Lead persists for lengthy periods in forest litter the estimated Tb 1/2 is 220 years (Turner et al. 1985). High levels of lead persisted for at least 6 years in litter, soil, amphibians, and mammals after zinc smelting was discontinued in Palmerton, Pennsylvania (Storm et al. 1994). Lead seems to be tightly bound by... 

Zinc concentrations in forest plants vary considerably. In oaks (Quercus spp.), for example, some species are accumulators, whereas others may be termed discriminators. For individual species, zinc concentrations tend to follow the pattern of roots > foliage > branch > trunk (Van Hook et al. 1980). Small lateral roots accumulate Zn to much greater levels than other vegetation components and are probably most sensitive to changes in zinc inputs. Half-time persistence of zinc in forest ecosystems varies from about 3 years in organic matter components to >200 years for large soil pools (Van Hook et al. 1980). 

Feng, J.C. Persistence, mobility and degradation of hexazinone in forest silt loam soils, J. Environ. Scl Health, B22(2) 221-233, 1987. 

Rapid growth of chemical weed control did not occur until after World War II when a herbicide was introduced by Jones in 1945 at the Imperial Chemical Industries of England 2,4-dichlorophenoxyacetic acid (2,4-D). Its utility has come from its ability to kill selectively broadleaf weeds in cereal grains, com, and cotton. It does not disturb the soil and is not persistent. 2,4,5-T was launched commercially by American Chemical Paint Co. in 1948 (now Union Carbide) to combat brush and weeds in forests, along highways and railroad tracks, in pastures, and on rice, wheat, and sugarcane. 

Soil persistence of triazines is important in forest usages. Much literature confirms that significant gains are made by reducing herbaceous plant cover for more than 1 year following planting. The triazines (e.g., simazine, atrazine,... 

The length of time pesticides persist in the forest floor and soil bears strongly on the probability they will be lost by volatilization (28-31). The phenoxy herbicides are commonly applied to forests as the low-volatile esters. These esters are readily hydrolyzed to their respective acids in soil or on the forest floor. For example, Smith (32) reported that no traces of 2,4,5-T and 2,4-D esters were observed in any of four moist soils after 48 and 72 hours, respectively, and most of them were hydrolyzed in less than 24 hours. The vapor pressures of the acids are much lower than the esters and this hydrolysis, along with subsequent degradation of the acids, results in a very low potential for volatilization of these materials from soil. 

Agnihotri, V P. (1970) Persistent of captan and its effects on microflora, respiration, and nitrification of a forest nursery soil. Can. J. Microbiol. 17, 377-383. 

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