Calculating pesticide sorption coefficients (Kd) using selected soil properties

Pesticide soil/solution distribution coefficients ( Kd values), commonly referred to as pesticide soil sorption values, are utilized in computer and decision aid models to predict soil mobility of the compounds. The values are specific for a given chemical in a given soil sample, normally taken from surface soil, a selected soil horizon, or at a specific soil depth, and are normally related to selected soil properties. Pesticide databases provide Kd values for each chemical, but the values vary widely depending on the soil sample on which the chemicals were tested. We have correlated Kd values reported in the literature with the reported soil properties for an assortment of pesticides in an attempt to improve the accuracy of a Kd value for a specific chemical in a soil with known soil properties. Mathematical equations were developed from regression equations for the related properties. Soil properties that were correlated included organic matter content, clay mineral content, and/or soil pH, depending on the chemical properties of the pesticide. Pesticide families for which Kd equations were developed for 57 pesticides include the following: Carboxy acid, amino sulfonyl acid, hydroxy acid, weakly basic compounds and nonionizable amide/anilide, carbamate, dinitroaniline, organochlorine, organophosphate, and phenylurea compounds. Mean Kd values for 32 additional pesticides, many of which had Kd values that were correlated with specific soil properties but for which no significant Kd equations could be developed are also included.     

Treatment and detoxification of a sanitary landfill leachate

The leachate from an old sanitary landfill (Gramacho Metropolitan Landfill, Rio de Janeiro) was characterized and submitted to coagulation and flocculation treatment followed by ozonation and ammonia stripping. The performance of the treatment was assessed by monitoring the removal of organic matter (COD and TOC), ammonium nitrogen and metals. Detoxification was assessed by determining acute toxicity, using the following organisms: Vibrio fisheri, Daphnia similis, Artemia salina and Brachydanio rerio. Membrane fractionation was employed to infer the range of molecular masses of the pollutants found in the effluent, as well as the toxicity associated to these fractions. Of the techniques under investigation, coagulation and flocculation followed by ammonia stripping were the most effective for toxicity and ammonium nitrogen removal. Membrane fractionation was effective for COD removal; however, acute toxicity was almost the same in all the fractionated samples. Ozonation was moderately effective for COD removal, but significant toxicity removal was only attained when high ozone doses were used.     

Ozonation of pentachlorophenol in unsaturated soils

A heterogeneous model was developed to describe interactions between ozone and hydrophobic organic compounds, exemplified by pentachlorophenol, in highly gas-saturated vadose zones where water moisture was limited to a thin film on soil particle surfaces. The soil was assumed to be free of soil organic matter. The model included a set of transient equations considering diffusion with simultaneous chemical reaction and hydrophobic partitioning. From dimensionless analysis, it was found that the film concentrations of ozone and the hydrophobic organic component were dependent on the Damk?hler numbers. Effects of Damk?hler numbers on the film profiles of components were examined. With the interfacial flux of ozone calculated from film profiles, dimensionless governing equations of ozone transport and contaminant removal across an experimental column were established. These equations were dependent on the Stanton number. One-dimensional column experiments were conducted to test the model. The optimal time for flow rate adjustment during the process was approximated. Finally, effects of ozone velocity and ozone gas concentration on the Stanton number were evaluated.     

Antioxidant enzyme activities as affected by trivalent and hexavalent chromium species in Fontinalis antipyretica Hedw

The detoxification mechanisms of the aquatic moss, Fontinalis antipyretica Hedw., exposed to Cr was analyzed. In addition, the influence of Cr salts (as Cr nitrate, chloride and potassium bichromate) on these mechanisms has also been studied. The activity of antioxidant enzymes superoxide dismutase (SOD, EC 1.15.1.1.), catalase (EC 1.11.1.6.), ascorbate peroxidase (APX, EC 1.11.1.11.), guaiacol peroxidase (GPX, EC 1.11.1.7.) and glutathione reductase (GR, EC 1.6.4.2.) increased in plants treated with Cr concentrations ranging from 6.25x10(-5) to 6.25mM when given as Cr(NO(3))(3). Antioxidant enzymes responded to the other two salts CrCl(3) and K(2)Cr(2)O(7) only with Cr concentrations higher than 6.25x10(-2)mM. Glutathione level and GSSG/GSH ratio also responded to Cr exposure but no dose-effect relationship could be observed. Moreover, two unknown thiol compounds were observed in mosses exposed to the highest Cr concentrations. Effects on chlorophyll contents and chlorophyll a/b ratios were also shown even at low Cr concentrations. Our results indicated that environmentally realistic concentrations of Cr could lead to impairment of the cellular activity towards F. antipyretica and that Cr(III), when present as a nitrate salt, was as harmful as Cr(VI).     

Salmonella enterica serovar Typhimurium hilA-lacZY fusion gene response to iron chelation or supplementation in rich and minimal media

Virulence expression of Salmonella enterica serovar Typhimurium under iron limited condition was measured by beta-galactosidase (beta-gal) assay using a hilA-lacZY fusion strain and calculated as Miller units. hilA-lacZY beta-galactosidase assays were performed in brain heart infusion (BHI) and minimal media (M9), after iron chelation with 2, 2-dipridyl and iron-supplementation respectively. Before performing virulence assays, concentrations of iron in the media were estimated using ferrozine. Iron content was found to be more in BHI (42.6 microg dL(-1)) as compared to M9 (10.03 microg dL(-1)). beta-gal activity of Salmonella Typhimurium in BHI was generally less than that observed in M9. After exposure to various combinations of iron chelator in BHI, hilA-lacZY activity only increased at the highest concentration of chelator (2001 microM) but decreased in M9 media for all iron concentrations when compared to controls with no iron amendment. These results indicate that iron availability may influence S. Typhimurium hilA expression.     

The effect of organic and hydraulic shock loads on the production of soluble microbial products in anaerobic digesters.

Anaerobic chemostats were used to investigate the effects of organic and hydraulic shock loads on the production of soluble microbial products (SMP). Production of SMP was found to increase during glucose spikes, reaching up 15% of the influent chemical oxygen demand. These SMP appear to be utilization-associated products produced as a result of the temporarily high organic load, and chemical analysis and ultrafiltration experiments revealed that most of these compounds are difficult to identify and that the majority of them are present in the low molecular weight (MW) range. Production of SMP also increased when the hydraulic retention time was reduced from 15 to 3 days, and an increase in DNA concentration in the bulk solution suggested enhanced cell lysis. Although the cause of lysis was not clear, it is believed that most of the SMP produced under such conditions were biomass-associated products following cell death. While the majority of these compounds lay in the low MW range, as much as 35% were found to have MWs greater than 1 kDa. During the period when the anaerobic chemostat was fed no alkalinity and the pH remained lower than 6.5 for more than a week, a slightly higher production of SMP and a shift in the MW distribution towards the production of higher MW SMP was observed.     

Simulation of global warming potential (GWP) from rice fields in the Tai-Lake region,China by coupling 1:50,000 soil database with DNDC model

Quantifying greenhouse gas (GHG) emissions from wetland ecosystems is a relatively new issue in global climate change studies. China has approximately 22% of the world's rice paddies and 38% of the world's rice production, which are crucial to accurately estimate the global warming potential (GWP) at regional scale. This paper reports an application of a biogeochemical model (DeNitrification and DeComposition or DNDC) for quantifying GWP from rice fields in the Tai-Lake region of China. For this application, DNDC is linked to a 1:50,000 soil database, which was derived from 1107 paddy soil profiles compiled during the Second National Soil Survey of China in the 1980–1990s. The simulated results show that the 2.34 Mha of paddy soil cultivated in rice–wheat rotation in the Tai-Lake region emitted about ?1.48 Tg C, 0.84 Tg N and 5.67 Tg C as CO₂, N₂O, and CH₄ respectively, with a cumulative GWP of 565 Tg CO₂ equivalent from 1982 to 2000. As for soil subgroups, the highest GWP (26,900 kg CO₂ equivalent ha^?1 yr^?1) was linked to gleyed paddy soils accounting for about 4.4% of the total area of paddy soils. The lowest GWP (5370 kg CO₂ equivalent ha^?1 yr^?1) was associated with submergenic paddy soils accounting for about 0.32% of the total area of paddy soils. The most common soil in the area was hydromorphic paddy soils, which accounted for about 53% of the total area of paddy soils with a GWP of 12,300 kg CO₂ equivalent ha^?1 yr^?1. On a regional basis, the annual averaged GWP in the polder, Tai-Lake plain, and alluvial plain soil regions was distinctly higher than that in the low mountainous and Hilly soil regions. As for administrative areas, the average annual GWP of counties in Shanghai city was high. Conversely, the average annual GWP of counties in Jiangsu province was low. The high variability in soil properties throughout the Tai-Lake region is important and affects the net greenhouse gas emissions. Therefore, the use of detailed soil data sets with high-resolution digital soil maps is essential to improve the accuracy of GWP estimates with process-based models at regional and national scales.