Soil activity

Mercury Recovery Services, Inc. (MRS), has developed the Mercury Removal/Recovery Process (MRRP) to treat media contaminated with mercury. The ex situ process uses medium-temperature thermal desorption to remove the mercury from contaminated wastes. Process wastes are heated in a two-step process to recover metallic mercury in a 99% pure form. MRS claims MRRP can be applied to soils, activated carbon, mixed waste, catalysts, electrical equipment, batteries, lamps, fluorescent bulbs, mercurous and mercuric compounds, mercury-contaminated waste liquids, and debris. 

Atrazine plays a central role in ecofallow because of its low cost, effective weed control, and extended soil activity. Atrazine controls volunteer wheat and most of the winter annual weed complex - including cheat, downy brome, wild mustards, and henbit, plus many spring annuals. No alternative herbicide has similar characteristics. Repeated applications of nonresidual, foliar-applied herbicides such as glyphosate or paraquat are not as economical. 

Triazine herbicide soil activity, movement, and residues depend primarily on content of organic matter, and to a lesser extent, clay colloids (Nearpass 1965 Day et al, 1968 Weber et al, 1969). Soils that are low in organic matter or clay usually require lower herbicide rates, but result in more potential phytotoxicity (Lange et al, 1969a). Simazine (4.0kg/ ha) or diuron (5.0kg/ha) gave season-long weed control in soils of the Northwest (Hogue and Neilsen, 1987). 

Stone, D.M., A.R. Harris, and W.C. Koskinen (1993). Leaching of soil-active herbicides in acid, low base saturated sands Worst-case conditions. Environ. Toxicol. Chem., 12 399-404. 

Registered formulations of hexazinone are soil active products. Selective brush control around pines occurs when lethal amounts of chemical is absorbed by brush species but not the pines. Pines are generally more resistant to the active ingredient than hardwoods. Thus a threshold level of chemical can be applied without damaging pines. However, selective rates of this herbicide vary by soil type and the applicator must carefully prescribe rates accordingly. 

Surprises or unpredicted events can happen. The early dogma, also based largely on our experience of triazine resistance, suggested that soil residual activity of herbicides was an important, if not essential, contributor to the selection of resistant biotypes. The subsequent development of multiple instances of paraquat resistance, followed by resistance to acetyl CoA carboxylase (ACCase) inhibitors, demonstrated that soil activity was not necessary for resistance to evolve. 

Measurement of soil activity there are a number of laboratory methods which are suitable for measuring the biological activity of the soil. In principle, a distinction is made between direct and indirect methods for the determination of soil activity. The biomass in the soil, for example, can be estimated by counting the individual organisms in the soil, or the measurement of respiration after the addition of a nutrient in excess can provide an indication of active biomass. Moreover, in determinations of activity, a distinction is made between actual and potential activity. Actual activity values are values measured at the time that the sample was taken. Determinations of potential activity, on the other hand, show the level of performance that microorganisms are capable of under optimum experimental conditions, after the addition of a nutrient substrate and prolonged incubation. 

To create or maintain a healthy soil structure and soil activity at a high level. 

This is the residue left after pressing the seeds of the castor oil plant. Castor oilmeal is mainly used as a nitrogen fertilizer and soil activator. The amounts used depend on the results of the analyses and the needs of the crops, and range from 800 to 1500 kg/ha. 

Globally, the oxides of nitrogen, NO (nitric oxide), NO2 (nitrogen oxide), and N2O (nitrous oxide), are key species involved in the chemistry of the troposphere and stratosphere. NO and N2O are produced mostly by microbial soil activity, whereas biomass burning is also an important source of NO. Nitric oxide is a species involved in the photochemical production of ozone in the troposphere, is involved in the chemical produaion of nitric acid, and is an important component of acid precipitation. Nitrous oxide plays a key role in stratospheric ozone depletion and is an important greenhouse gas, with a global warming potential more than 200 times that of CO2. 

Drake, J.J., 1980, The effect of soil activity on the chemistry of carbonate groundwaters. Water Resources Research, 16 381-386. 

All soil types showed a similar pattern of tritium loss to leachate with time. After a short period of about a month, the tritium concentration in the leachate peaked at about 100 - 200 mBq ml It then fell over the next month or so to a low and fairly constant value of about 10-20 mBq m Where measurements were made, there was no significant difference between the aqueous and total tritium concentration. It would therefore be reasonable to assume that all of the tritium lost via downward leaching was in the form of tritiated water. Although tritium could be measured in the leachate, the overall flux did not account for all of the losses as broadly implied from the measurements in soils from the containers. Table 4 shows that for all soil types, only about one third of the decrease in soil activity can be accounted for in the leachate. 

Replacement of the normal pyrethroid ester by alternative linkages usually leads to diminution of biological activity. One important exception to this general phenomena is several oxime ether derivatives, in particular, 3-phenoxybenzyl derivatives of various alkyl aryl ketones. Pyrethroid esters derived from certain 2-substituted-[1,1 -biphenyl]-3-methanols have been shown to possess initial and residual activity surpassing that of esters derived from 3-phenoxybenzyl alcohol. Now it has been demonstrated that the same enhancement of activity was observed for alkyl aryl oxime ethers of certain [1,1 -biphenyl]-3-methanols compared to the corresponding 3-phenoxybenzyl alcohol derived oximes. The synthesis, biological activity, including soil activity, structure-activity relationships and toxicity of several of these biphenylmethyl oxime ethers are described. 

Table III. Soil Activity of Alkyl Aryl Oxime Ethers...

Examination of these data clearly shows that none of the three compounds Is as effective as terbufos In the jar test. Perhaps the most Interesting aspect of this data Is the relative soil efficacy of the second compound compared to the first. The substitution of a methyl group for a hydrogen between the two sulfur atoms greatly enhances the soil activity of this molecule. Quantitation of the relative soil stability of these three molecules as measured by the bioassay data are collected in Table 5 using a pseudo first order kinetic analysis of the data. 

Toxicity to house fly is obviously quite good. Moderate efficacy is demonstrated against the corn rootworm beetles and mosquito larvae. For an insecticide of the prolan/DDT class, the potency demonstrated against the wild strain German cockroach is quite remarkable. Preliminary tests on the larval stage corn rootworm revealed soil activity of a monochloro compound, unlike most previously reported chemicals in this class. Overall, the spectrum of activity is quite broad, although other categories of insect pests must still be tested (e.g., lepidopteran larvae). 

To examine the effect of initial concentration on the development of activity, four soil types were initially treated with five levels of carbofuran ranging from 0.01 to 100 ppm. The results of the subsequent activity tests are summarized in Table V. Concentrations of 1 ppm were sufficient to cause activity to develop in the three mineral soils. Concentrations in excess of 1 ppm were required for the organic soil. Activity appears to develop quickly over a broad range of conditions that one would encounter naturally during use of the insecticide. 

This means that those organisms in soil active in denitrification have N2O as a freely diffusable, obligate intermediate of denitrification. Since the cells did not seem to sequester pools of N2O, factors that stimulate N2O production or reduce N2O reduction would be expected to cause an increase in the N2O emitted from denitrifying cells. This interpretation helps explain why a number of factors affect N2O production (see the section on factors affecting N2O production). 

Other Potential Problems in Universal Pre-screens. Some soil active herbicides are highly volatile and there are problems in keeping them in the media for use in herbicide studies. This problem was overcome by using a non-volatile fnon-commerclal) thiocarbamate in cell culture studies to screen for heroicide resistant strains (IS). This solution to the problem of volatility does not apply to universal pre-screens. 

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