Soil systems water relations

In relation to risk-based management, the JOINT project conclnded that accompanying activities are necessary that help to network within the scientific and end-users communities, to evalnate the resnlts and up-date the state of the art, and to focus on the main needs, strategies and fnture perspectives . Furthermore, an integrated management approach is needed, which considers soil and waters as one system, interacting with other compartments of the environment and with the socio-economic world through users and fnnctions (JOINT, 2005). 

Although the organophosphates are generally more soluble than the chlorinated hydrocarbons, they do not move any more readily in soil systems (289, 314). Dimethoate, malathion, phorate, disulfoton, methyl parathion, and parathion move in soils to some degree (315, 316). Their movement was related to their water solubilities with the more soluble compounds being the most mobile. The compounds were retained primarily in surface soils and did not leach into subsoils except in small... 

Fenuron was mobile in soil systems compared with other phenylurea herbicides (87, 356), Movement was related to the water solubilities of the compounds (87). Fenuron s leachability was also greater in coarse textured soils than in fine textured ones and was related to the organic matter content of the soil. In a recent field experiment fenuron moved substantially in a lateral direction over the soil surface and in a vertical direction into the subsoil (63). Femuron moved into the subsoil much more on coarse textured soils than on fine textured ones, but it moved only when excessive amounts (80-160 pounds per acre) were used (356). 

CDAA, molinate, EPTC, vernolate, pebulate, CDEC, and cycloate are all relatively mobile in soil systems (123, 385, 386, 387, 388 389, 390, 391). The herbicides leached more readily in coarse textured soils than in fine textured ones and did not significantly leach in peat or muck soils (386, 387, 388, 391), Leachability of the compounds was related to their water solubilities (compounds of higher solubilities moved more than less soluble ones) and to the organic matter and clay contents of the soils (less movement as the organic matter and clay content increased). 

Dichlobenil is considerably less soluble in water and has a much lower vapor pressure than the other herbicides given in Table XI, but in aqueous and soils system it behaves similarly. It was relatively immobile in most soils but did leach considerably in sand (402, 403). Adsorption was related to the organic matter content of soils (404). Much dichlobenil was adsorbed from aqueous solutions by organic soil, lignin, and lanolin wax, but it was not significantly adsorbed by cellulose, sandy soil, sand, or soybean protein (403). 

Steinheimer [995] studied atrazine and related compounds, deisopropylatrazine, deethylatrazine, and terbuthylazine, in soil and water samples. These compounds were resolved using a Cjg column (. = 220nm) and a complex 23-min 10/0/90 100/0/0-> 0/100/0 acetonitrile/methanol/water gradient. The last peak of interest eluted at 17-min. Acetonitrile and methanol flushes were done to clean the system between injections. Calibration curves are shown for four of the analytes and were linear over the 0.2-50 ppm range. Detection limits of extracted samples were reported as 0.4 pg/L (water) and 40 pgAs (soil). Solubility in water was given for the components, the lowest being terbuthylazine at 8 ppm. 

The higher concentrations of phenolic acids required for a given percent inhibition between the two systems stem from the fact that nutrient cultures have a much more consistent environment than soil culture systems in that water, nutrients, and phenolic acids are evenly distributed in the treatment container and thus are readily available to interact with root surfaces. Soil systems, on the other hand, are much more complex heterogeneous environments in which roots must compete with a variety of soil sinks (e.g., clays, organic matter, and microbes) for water, nutrients, and phenolic acids. There is also mechanical resistance to the movement of water, nutrients, and phenolic acids and the growth of roots in soils. The slower development of inhibition after treatment and the slower recovery after phenolic acid depletion in soil systems is very likely related to the slower growth of seedlings in soil culture. 

It must be noted that most certification systems are specifically aimed at the evaluation of industrial compostability, as this is the most frequently used end of life option. Some other systems are related to biodegradation in soil, water or home compostability. 

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