Laboratory studies on volatilization and mineralization of 14c‐p,p'‐DDT in soil,release of bound residues and dissipation from solid surfaces

Abstract

In support of field data, laboratory studies were conducted on volatilization, mineralization and binding of ¹⁴C‐p,p'‐DDT in soils at Sao Paulo. Incubation of soil for 6 weeks did not result in volatilized organics or mineralization; with >95% extractable radiocarbon in the form of p,p'‐DDT. Small amounts of bound residues (1.8%) were detected in soil. These data confirm the very slow dissipation of DDT in the field which presumably relates to the acidic pH of soil (4.5–4.8).

Bound ¹⁴C‐residues in soils treated with ¹⁴C‐p,p'‐DDT at Praia Grande and Sao Paulo could be released (5–21%) by sulphuric acid treatment. The released residue had the composition: 69–90% DDT, 7–32% DDD and 0–3% DDE. Incubation of soil bound ¹⁴C‐residues with fresh inoculum for 3 months did not result in release of ¹⁴C.

Dissipation from wooden surfaces was fairly slow. After 20 weeks, 74% of the applied radioactivity could be recovered; 44% hexane‐non‐extractable.     

Studies of the effects of temperatures and solar radiation on volatilization,mineralization and binding of 14c‐DDT in soil under laboratory conditions

Abstract

The effects of temperatures and solar radiation on the dissipation of ¹⁴C‐p,p'‐DDT from a loam soil was studied by quantifying volatilization, mineralization and binding. The major DDT loss occurred by volatilization, which was 1.8 times more at 45^oC than at ambient temperature (30°C). Mineralization of DDT slowly increased with time but it decreased slightly with increase in temperature. Binding of DDT to soil was found to be less at higher temperatures (35 and 45°C) as compared to ambient temperature. Degradation of DDT to DDE was faster at higher temperatures.

Exposure of non‐sterilized and sterilized soils treated with ¹⁴C‐DDT to sunlight in quartz and dark tubes for 6 weeks resulted in significant losses. Volatilization and mineralization in quartz tubes were more as compared to dark tubes. The volatilized organics from the quartz tubes contained larger amounts of p,p'‐DDE than the dark tubes. Further, higher rates of volatilization were found in non‐sterilized soils than in sterilized soils. The results suggest that faster dissipation of DDT from soil under local conditions relates predominantly to increased volatilization as influenced by high temperature and intense solar radiation.     

Studies on the dissipation of 14C‐DDT from water and solid surfaces

Abstract

Dissipation of ¹⁴C‐p,p'‐DDT from water was studied for 180 days under outdoor conditions. DDT dissipated rapidly with overall half‐life of 53 days. The main degradation products were p,p'‐DDE and p,p'‐DDD. A portion of ¹⁴C‐residues was found in the sediment plus biomass (pellet) and on the inner surface of the glass container. This amounted to 7.2 and 6.7% of the initially added radioactivity, respectively. After 6 months, bound¹⁴C was more as compared to extractable ¹⁴C and p,p'‐DDD was the major metabolite of p,p'‐DDT in the extractable fraction. DDT dissipated from clay plates under indoor conditions with an overall half‐life of 160 days.     

Laboratory studies of dissipation of 14C‐DDT from soil and plywood surfaces

Abstract

The effects of temperature and solar radiation on dissipation of ¹⁴C‐p,p'‐DDT from a latosol soil were studied under laboratory conditions. Volatilization was measured by trapping organic volatiles during 6 weeks and was found to increase with rise of temperature from 3.8% of initial amount at ambient temperature to 5.9% at 45°C.

Studies on the effect of solar radiation using quartz tubes under sterilized and non‐sterilized conditions have shown that volatilized organics were highest in quartz tubes, with soil microflora presumably playing a very minor role in volatilization. Mineralization was shown to be low in sterilized systems and highest in non‐sterilized quartz systems. Studies on binding suggest that soil bioactivity may be involved in the formation of a portion of the bound residue. These laboratory experiments seem to support data from the field, where it is maintained that volatilization is a major mechanism for dissipation. Degradation in soil and to a lesser extent solar irradiation contribute also substantially to the dissipation mechanisms. Radiocarbon dissipated from plywood surfaces under indoor conditions in a biphasic fashion. Loss of 50% occurred after 5.5 weeks while the remainder dissipated at a very slow rate.     

Chemical and biological release of 14C‐bound residues from soil treated with 14C‐p,p'‐DDT

Abstract

¹⁴C‐p,p'‐DDT‐bound residues in soil can be released by treatment with concentrated sulphuric acid at ambient temperatures. Within 6 days, about 70% of the bound residues was released. Bound residues released after 9 months incubation with ¹⁴C‐DDT showed the presence of DDT and DDE only while bound residues released after 18 months, contained in addition 13% DDD.

Release of bound ¹⁴C‐residues also occurs readily following inoculation of the soil‐bound residues with fresh soil or with individual microorganisms. Almost complete release of bound residues was observed after incubation for 45 days. The rate of release was rapid during the first two weeks and decreased thereafter. TLC and HPLC analysis showed that the released residues contained DDE (about 80%) and a smaller amount of DDD. The disappearance of DDT from the released residues may be attributed to its microbiological degradation to DDE and DDD, shortly after its release.     

Persistence of granular and EC formulations of chlorpyrifos in a mineral and an organic soil incubated in open and closed containers

Abstract

Samples of a mineral soil (Plainfield sand) and an organic soil (muck) were treated with granular and EC formulations of chlorpyrifos and incubated at 27±1°C and 65±5% RH in open and closed containers. Duplicate samples of each soil‐formulation‐container combination were analyzed for residual chlorpyrifos during a 23 wk period. The disappearance rates observed demonstrate that the relative importance of formulation and containment on overall persistence depends on soil type. For the mineral soil, disappearance was slower from closed containers and formulation had only a slight effect while, in the organic soil the granular formulation disappeared slower than the EC and there was little difference between open and closed containers. The relative importance of degradation and volatilization in the disappearance of chlorpyrifos from soil is discussed.     

Dissipation of DDT in natural water under field conditions

Abstract

¹⁴C‐DDT dissipated gradually from natural water under outdoor conditions and declined to 40% of the applied radioactivity after 5 months. The losses are due to adsorption to particulates and volatilization from the water surface. In natural water DDT undergoes gradual conversion to DDE as the major degradation product and to a lesser extent to DDD. It may be concluded that DDT dissipates and degrades fairly rapidly in subtropical natural waters. Adsorption to particulate matter contributes to partial “removal” of DDT.     

Removal technology for pesticide contaminants in potable water

Abstract

Granular activated carbon adsorption is one of the reliable and effective means of removing organochlorine pesticides from water. Continuous stirred tank and fix bed reactor systems were used for the screening of indigenous granular activated carbons in the removal of organochlorine pesticides from water at low microgram levels in simulated samples. The carbon dose reguired to treat raw water at initial concentrations of 5–10 ug/1 of Y‐HCH, p,p'‐DDT and p,p'‐DDE to <2 ug/1 potable level was computed. Data leads to the development of a tap attachable water treatment unit for pesticides removal for applications on domestic scale.     

Herbicide movement and dissipation at four midwestern sites

Abstract

This study was conducted to evaluate atrazine (2‐chloro‐4‐ethylamino‐6‐isopropyl‐1, 3, 5‐triazine) and alachlor (2‐chIoro‐N‐(methoxymethyl)acetamide) dissipation and movement to shallow aquifers across the Northern Sand Plains region of the United States. Sites were located at Minnesota on a Zimmerman fine sand, North Dakota on Hecla sandy loam, South Dakota on a Brandt silty clay loam, and Wisconsin on a Sparta sand. Herbicide concentrations were determined in soil samples taken to 90 cm four times during the growing season and water samples taken from the top one m of aquifer at least once every three months. Herbicides were detected to a depth of 30 cm in Sparta sand and 90 cm in all other soils. Some aquifer samples from each site contained atrazine with the highest concentration in the aquifer beneath the Sparta sand (1.28 μg L^‐1). Alachlor was detected only once in the aquifer at the SD site. The time to 50% atrazine dissipation (DT₅₀) in the top 15 cm of soil averaged about 21 d in Sparta and Zimmerman sands and more than 45 d for Brandt and Hecla soils. Atrazine DT₅₀ was correlated positively with % clay and organic carbon (OC), and negatively with % fine sand. Alachlor DT₅₀ ranged from 12 to 32 d for Zimmerman and Brandt soils, respectively, and was correlated negatively with % clay and OC and positively with % sand.     

The degradation of parathion and DDT in aqueous systems containing organic additives

Abstract

Laboratory studies were conducted to investigate some of the factors influencing pesticide degradation in‐ aqueous systems. Parathion added to natural water in ethanol, acetone or without organic solvent, was completely degraded within 2 wk. While most of the parathion was reduced to amino‐parathion when added in ethanol, no amino‐parathion was detected in the presence of acetone or when no solvent was added, suggesting that in the latter two cases the insecticide was aerobically degraded to other metabolites. No paraoxon was detected. When ethanol concentration was increased from 1% to 2 and 4%, the rate of parathion degradation was inversely related to the ethanol concentration. In the presence of glucose as a carbon source, approximately 50% of the parathion was reduced to aminoparathion. DDT degradation in natural water was more rapid when it was added in ethanol than when added in acetone. The only DDT metabolite detected was TDE, with about 36% conversion in presence of ethanol, and 20% when the DDT was added in acetone.     

Environmental implications of soil remediation using the Fenton process

This work evaluates some collateral effects caused by the application of the Fenton process to 1,1-bis(4-chlorophenyl)-2,2,2-trichloroethane (DDT) and diesel degradation in soil. While about 80% of the diesel and 75% of the DDT present in the soil were degraded in a slurry system, the dissolved organic carbon (DOC) in the slurry filtrate increased from 80 to 880mgl(-1) after 64h of reaction and the DDT concentration increased from 12 to 50microgl(-1). Experiments of diesel degradation conducted on silica evidenced that soluble compounds were also formed during diesel oxidation. Furthermore, significant increase in metal concentrations was also observed in the slurry filtrate after the Fenton treatment when compared to the control experiment leading to excessive concentrations of Cr, Ni, Cu and Mn according to the limits imposed for water. Moreover, 80% of the organic matter naturally present in the soil was degraded and a drastic volatilization of DDT and 2,2-bis(4-chlorophenyl)-1,1-dichloroethylene was observed. Despite the high percentages of diesel and DDT degradation in soil, the potential overall benefits of its application must be evaluated beforehand taking into account the metal and target compounds dissolution and the volatilization of contaminants when the process is applied.     

Modeling effects of moisture content and advection on odor causing vocs volatilization from stored swine manure

Abstract

Two models for evaluating the contents and advection of manure moisture on odor causing volatile organic compounds (VOC‐odor) volatilization from stored swine manure were studied for their ability to predict the volatilization rate (indoor air concentration) and cumulative exposure dose: a MJ‐I model and a MJ‐II model. Both models simulating depletion of source contaminant via volatilization and degradation based on an analytical model adapted from the behavior assessment model of Jury et al. In the MJ‐I model, manure moisture movement was negligible, whereas in the MJ‐II model, time‐dependent indoor air concentrations was a function of constant manure moisture contents and steady‐state moisture advection. Predicted indoor air concentrations and inhaled doses for the study VOC‐odors of p‐cresol, toluene, and p‐xylene varied by up to two to three orders of magnitude depending on the manure moisture conditions. The sensitivity analysis of both models suggests that when manure moisture movement exists, simply MJ‐I model is inherently not sufficient to represent a more generally volatilization process, which can even become stringent as moisture content increases. The conclusion illustrates how one needs to include a wide variety of manure moisture values in order to fully assess the complex volatilization mechanisms that are present in a real situation.     

Volatilization of 1,2‐dibromo‐3‐chloropropane (DBCP) from soils

Abstract

The volatilization of DBCP from soils, as affected by the soil characteristics and application techniques, was studied in a laboratory experiment. The volatilization rate of DBCP applied in water was higher from sandy and silty loam soils than from clay soil. Water added after DBCP application acted as a soil cover, decreasing the volatilization rate. The results obtained with DBCP application in hexane to air‐dry soils, indicate that adsorption could be an important factor in reducing the volatilization losses.

Diffusion coefficients were calculated from the volatilization parameters, by using a simplified relationship between volatilization losses and diffusion through soil.     

Leaching of mecoprop and dichlorprop in calcareous soil. Effect of the exogen organic matter addition in this process

Abstract

Leaching studies of mecorprop (R,S)‐2‐(4‐chloro‐2‐methylphenoxy)propanoic acid, and dichlorprop, (R,S)‐2‐(4‐chloro‐2,4‐dichlorophenoxy) propanoic acid, under saturated conditions were conducted in unamended and amended soil columns. The purpose of the study was to investigate the leaching of these herbicides in three type of soils and the exogen organic matter effect on this process. The leaching patterns could be related to variation in the soil texture and diffusion processes of the herbicides into micropores within the walls of conducting pore. The leaching rate in the amended soil columns decreased with the addition of organic matter. The breakthrough curves (BTC) of these herbicides in the leachates of the amended soil columns were wider and more diffused than the BTC obtained for the corresponding unamended soil. The theoretical BTC overestimated the pore volume required for the displacement of these pesticides from the soil column. This may be due to the differences in the adsorption process between the bacth and soil columns methods     

Atmospheric DDTs over the North Pacific Ocean and the adjacent Arctic region: Spatial distribution,congener patterns and source implication

During the 2003 Chinese Arctic Research Expedition (CHINARE 2003) from Bohai Sea to the high Arctic (37°N–80°N), air samples were collected and analyzed for DDTs. ∑DDTs (sum of six congeners) ranged from 0.52 to 265 pg m^?3 with an average of 13.1 pg m^?3. Higher DDT concentrations were observed in Bohai Sea and near eastern Russia. The congener patterns were obviously different between the Far East Asia and the higher latitudinal regions that p,p'-DDT and o,p'-DDT were dominated in the former; while o,p'-DDT and o,p'-DDE were dominated in the latter. The source contributions of technical DDT and dicofol type DDT were estimated. Results showed that technical DDT was the dominant source (>94%) which was fresher in the Far East Asia compared to the North Pacific Ocean and the Arctic. For dicofol type DDT, the estimated contribution was minor. The “new” o,p'-DDT observed should have relatively more contribution from dicofol type DDT in the North Pacific Ocean and the Arctic.     

Determining the role of humic substances in the fate of pesticides in the environment

Abstract

The data presented in this paper emphasize that the behavior and fate of pesticides in the environment is influenced by humic substances. Various methods most frequently used for the characterization of humic substances are discussed. Both humic acid and fulvic acid can solubilize in water certain organic compounds and are important carriers of some pesticides in soil. Humic substances have the potential for promoting the nonbiological degradation of many pesticides. Several methods of bleaching humus color from drinking water, including chlorination, ozonation, and UV‐radiation, are described. Finally, the photochemical stability to UV‐radiation of certain pesticides in aqueous fulvic acid solution is discussed.     

Monitoring transport of selected pesticides and phenols in soil columns by high performance liquid chromatography

Abstract

Soil columns were used to study pesticides and phenols transport under rapid infiltration land treatment conditions. An analytical procedure is described for the quantitative determination of atrazine, diuron, carbofuran, phenol, 2,4‐dinitrophenol, 2,4‐dimethylphenol, and 2,4‐dichlorophenol in soil and wastewater. Recoveries of all analytes were greater than 90%. The method detection limits for all analytes were ≤0.03 μg/ml (s/n=4) in wastewater and ≤ 0.1 μg/ml (s/n=5) in soil.     

Determination of organochlorine and organophosphate pesticide residues in fruits,vegetables and sediments

Abstract

A method is described for the determination of organochlorine and organophosphate pesticide residues in fruits, vegetables and sediments. The concentrated solvent extract was sealed in a polymeric membrane tube, dialysed in cyclohexane and the solvent replaced with hexane. The organophosphates were analysed on a specific thermionic detector without further clean‐up. For the organochlorine pesticides the extract was eluted through 3 g of alumina and analysed on GC/ECD. The clean‐up for sediment extract was carried out on a10 g alumina column with 100 mL hexane containing 5% acetone and the eluate was concentrated to 5 mL.

The detection limit for organophosphates on a 40 g sample and a final volume of 10 mL was on the average 0.01 mg/kg. The detection limit for organochlorine pesticides, with the final volume of 25 mL, was 0.005 mg/kg for all pesticides except for p,p'‐DDT and endosulfan sulphate, which was 0.01 mg/kg.

The detection limit for oganochlorine pesticides in sediment, with the final volume of 2 mL, was less than 1 μg/kg and for organophosphate pesticides less than 10 μg/kg when the final volume was made to 0.5 mL. At the detection limits the method produced a very high coefficient of variation for both organochlorine and organophosphate pesticides.     

Leaching,mobility and persistence of tebufenozide in columns packed with forest litter and soil

Abstract

Leaching, downward mobility and persistence of tebufenozide was investigated under laboratory conditions in columns packed with forest litter and soil, after fortification with the analytical grade material (purity > 99.6%) and with two commercial formulations, RH‐5992 2F (aqueous flowable) and RH‐5992 ES (emulsion suspension). Two types of litter and soil were used: one type with relatively high amounts of sand and the other with high amounts of clay.

The concentrations eluted in the leachates were lower when the analytical material (dissolved in acetone) was used for fortification, than when the two formulations (diluted with water) were used. The amount leached was higher for RH‐5992 2F than for RH‐5992 ES. The type of substrate, i.e., sandy or clay type, had only marginal influence on the amounts eluted in the leachates. Downward movement of tebufenozide from the top 2‐cm layer to the untreated middle and bottom layers (3‐cm segments) was consistently lower when the analytical material was used for fortification, than when the two formulations were used. Downward movement was higher for RH‐5992 2F than for RH‐5992 ES. Persistence of tebufenozide in substrates, maintained under submerged conditions for 70 days after leaching, indicated an initial 2‐week lag period prior to the onset of degradation. Formulation‐related differences were observed in the half‐life (DT₅₀) values. When the analytical material was used for fortification, the DT₅₀ ranged from ca 54 to 59 d. However, when the formulations were used for fortification, the DT₅₀ showed a higher range, i.e., from ca 62 to 67 d for RH‐5992 2F and ca 70 to 80 d for RH‐5992 ES. Formulation ingredients appear to have caused enhanced adsorption of tebufenozide onto the substrates, thus delaying degradation.     

Aerobic and anaerobic degradation of profluralin and trifluralin

Abstract

The degradation of profluralin [N‐(cyclopropylmethyl)‐α,α,α‐trifluoro‐2,6‐dinitro‐N‐propyl‐]p‐toluidine] and trifluralin (α,α,α‐trifluoro‐2,6‐dinitro‐N,N‐dipropyl‐p‐toluidine) was studied under aerobic and anaerobic soil conditions. Three soils (Goldsboro loamy sand, Cecil loamy sand, Drummer clay loam) were each treated with 1 ppmw herbicide; anaerobic conditions were maintained by flooding. Soil samples were extracted monthly and subjected to TLC analysis. No degradation was detected in sterile controls. Aerobic degradation of both herbicides was greatest in the Cecil loamy sand soil over the entire incubation period. Degradation of profluralin in Cecil soil under aerobic conditions was 86 percent after 4 months with three products detected; 83 percent of the trifluralin was degraded with two products detected. Anaerobic degradation accounted for 72 percent of the profluralin and 78 percent of the trifluralin after 4 months. Degradation of both herbicides increased with incubation time for the first 3 months and decreased slightly thereafter. Generally there was more extensive degradation (percent and in number of products formed) of profluralin than trifluralin under the conditions tested. More degradation products were detected for both herbicides under aerobic conditions than under anaerobic conditions.