Matter soil organic

Considerable research has been conducted to investigate the soil sorption and mobiUty of dinitroaniline herbicides. In general, these herbicides are strongly sorbed by soil (354), and sorption has been correlated to both soil organic matter and clay content (355). Dinitroaniline herbicides are not readily leached in most soils (356), although leaching of triduralin is enhanced by addition of surfactants (357). 

Acid amide herbicides are nonionic and moderately retained by soils. The sorption of several acid amide herbicides has been investigated (369). Acetochlor [34256-82-1] is sorbed more than either alachlor or metolachlor, which are similarly sorbed by a variety of soils. Sorption of all the herbicides is well correlated to soil organic matter content. In a field lysimeter study, metolachlor has been found to be more mobile and persistent than alachlor (370) diphenamid [957-51-7] and napropamide [15299-99-2] have been found to be more readily leached (356). 

Pyridine herbicides are not strongly sorbed to soils and ate readily leached. The mobiUty of flutoxypyt [69377-81-7] has been found to decrease with increasing incubation time (399) this is attributed to entrapment of the herbicide within the soil organic matter. 

Sulfonylurea herbicides ate weak acids and, in general, ate not strongly sorbed to soils. Sorption of chlotsulfuton and metsulfuron—methyl is inversely related to soil pH (407) and is positively correlated to soil organic matter (408). 

Preferential flow through root-mediated soil pores has been demonstrated for chloride, nitrate, and other ions that are not sorbed onto soil organic matter and clays. However, pesticide sorption onto soil affects both mobiUty of the pesticide as well as its residual life in the soil. Pesticide sorption onto root organic matter or organic linings of worm burrows may also slow transport of pesticides relative to water (72), thus countering the effects of increased permeabihty caused by roots. 

The fertilizer nitrogen in the soil organic matter was assumed to be remineralized in subsequent years according to the following pattern 10% in the first year, 3% of the remainder in the second year, and 1% of the remainder in each of all subsequent years. 

Remineralized from soil organic matter, then leached 7 2... 

Interrelated with change in particle size and changes in type and kind of soil minerals present, organic matter is formed and accumulates as an integral part of the soil. Organic-matter content varies from practically none in sands to almost 100%, as exemplified by peat formations. The amount of organic matter present thus reflects the interaction of all environmental... 

The relative immobility of the chlorodioxins is expected, based on the very low solubility of these compounds in water (0.6 / g/liter). In contrast, the herbicide, 2,4,5-T, is relatively mobile in sandy soils, but movement decreases as soil organic matter increases. What does this information tell us, and how does it compare with other organic compounds A mobility scale has been devised for a large number of pesticides (3). Higher mobility numbers reflect increased compound mobility in soils. The dioxins would be in Class 1—i.e., they are immobile in soils and would compare with several chlorinated hydrocarbon insecticides. 

It has been shown that N-nitrosation was enhanced by the increase in organic matter content of the soil (13). It was postulated that a simple constituent of soil organic matter may be involved as a catalyst. For example, thiocyanate has been... 

Achnich A, E Fernandes, J-M Bollag, H-J Knackmuss, H Lenke (1999) Covalent binding of reduced metabolites of [ NjJTNT to soil organic matter during a bioremediation process analyzed by NMR spectroscopy. Environ Sci Technol 33 4448-4456. 

D. Vaughan, R. E. Malcom, and B, G. Ord, Influence of humic sub.stances on biochemical processes in plants. Soil Organic Matter and Biological Activity (D. Vaughan and R. E. Malcom, eds.), Martinus Nijhoff Dr, W. Junk Publishers, Dordrecht, 1985, p. 78. 

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