Occurrence and distribution of pesticides in soil at agrichemical facilities in Illinois

Detectable concentrations of pesticides were found in soil samples collected from 49 agrichemical facilities located throughout Illinois. Analysis of 822 soil samples resulted in the detection of 53 pesticides and nitrate; 20 pesticides were found in fewer than 1% of the samples. Most frequently detected were alachlor, atrazine, metolachlor, trifluralin, pendimethalin, cyanazine, metribuzin, metribuzin DA, butylate, and α‐BHC. Chlordane, dieldrin, and DDT, although not distributed at the facilities in recent years, were found in soil samples from more than one third of the sites. Approximately 24% of the pesticide detections occurred in a concentration range between the detection limit and 50 μg/kg, and 79% of all detections were less than 1000 μg/kg.

Pesticides were detected at sampling depths to 4.5 m. However, approximately 50% of all pesticide detections were found in the gravel fill that serves as the parking lot/road base for each facility. No predictable pattern in pesticide occurrence in relation to sampling depth could be determined on the basis of the mobility or persistence of the pesticide.     

Using Soil Available P and Activities of Soil Dehydrogenase and Phosphatase as Indicators for Biodegradation of Organophosphorus Pesticide Methamidophos and Glyphosate

The heavy use of organophosphorus pesticides in northeastern China strongly affects the ecological functions and the quality of the soil environment. In this work, a 30-day soil incubation experiment was conducted to evaluate the potential of using soil available P and the activities of soil dehydrogenase and acid phosphatase as indicators of the application of methamidophos and glyphosate. Two kinds of unpolluted soils, phaiozem and burozem, were selected as the test soils. The higher application rate of organophosphorus pesticide to the two soils caused more release of PO₄ ^3? which finally entered the soil available P pool, suggesting that soil available P is one of the effective chemical markers for biodegradation of organophosphorus pesticides. Methamidophos exhibited a significant inhibitory effect on the activity of soil dehydrogenase. The extent of enzyme inhibition was almost positively correlated with the insecticide concentration, and the enzyme activity was gradually restored after day 15. However, its effect on soil acid phosphatase activity (stimulation or inhibition) seemed to be indefinite, and varied with the application rate, soil type, and incubation time. In the case of glyphosate, soil acid phosphatase activity was depressed significantly and the depressing extent could be a function of herbicide concentration and incubation time, but soil dehydrogenase activity showed an irregular variation with the herbicide application rate and soil type. In general, dehydrogenase activity was a good biochemical indicator for the biodegradation of methamidophos, but for glyphosate biodegradation the indicator was acid phosphatase activity.     

Glyphosate bioavailability in soil

Biodegradation of glyphosate in sod-podzol soil by both the indigenous micro flora and the introduced strain Ochrobactrum anthropi GPK 3 was studied with respect to its sorption and mobility. The experiments were carried out in columns simulating the vertical soil profile. Soil samples studied were taken from soil horizons 0–10, 10–20, and 20–30 cm deep. It was found out that the most of the herbicide (up to 84%) was adsorbed by soil during the first 24 h; the rest (16%) remained in the soluble fraction. The adsorbed glyphosate was completely extractable by alkali. No irreversible binding of glyphosate was observed. By the end of the experiment (21st day), glyphosate was only found in extractable fractions. The comparison of the effect of the introduced O. anthropi GPK 3 and indigenous microbial community on the total toxicant content (both soluble and absorbed) in the upper 10 cm soil layer showed its reduction by 42% (21 mg/kg soil) and 10–12% (5 mg/kg soil), respectively. Simultaneously, 14–18% glyphosate moved to a lower 10–20 cm layer. Watering (that simulated rainfall) resulted in a 20% increase of its content at this depth; 6–8% of herbicide was further washed down to the 20–30 cm layer. The glyphosate mobility down the soil profile reduced its density in the upper layer, where it was available for biodegradation, and resulted in its concentration in lower horizons characterized by the absence (or low level) of biodegradative processes. It was shown for the first time how the herbicide biodegradation in soil can be increased manifold by introduction of the selected strain O. anthropi GPK 3.     

Sorption and desorption of arsenic from sandy soils: Column studies

Rate‐limited sorption/desorption can have a profound effect upon the transport of sorbing contaminants. Numerical and analytical models used to predict chemical movement through the subsurface rarely incorporate the effects of nonlinear sorption and desorption kinetics, resulting in potentially large overestimates of mass extractability. Mass transfer characteristics of arsenic‐contaminated soils at the site of a former arsenical herbicide manufacturer in Houston, Texas, were examined in the laboratory using soil columns. Unaffected soils comprised of silty sands to coarse sands were collected from the uppermost aquifer. Two soil columns were loaded with a known mass of mixed organic and inorganic forms of arsenic resident in site ground water. A third control column was prepared with dry 20 × 30 mesh ASTM silica sand. Leachate samples were collected from each void volume until arsenic breakthrough was achieved. The dynamic test applied a continuing head of water, operating in an upflow mode through 4‐in. diameter by 12‐in. long soil columns repacked to in situ density. A flow‐through velocity of one void volume per day was chosen for arsenic loading to the columns and 0.08 void volume per day during the desorption phase of the test. Uncontaminated ground water was then passed through the columns, and the tests were restarted in the desorption mode. Analysis of the leachate and resulting arsenic concentrations in the test columns allowed for the calculation of distribution coefficients that describe arsenic behavior. Measured distribution coefficients during desorption ranged from 0.26 after one void volume to 3.3 after six void volumes had been passed through the column.     

Sampling volume in root studies: the pitfalls of under‐sampling exposed using accumulation curves

Root systems are important for global models of below‐ground carbon and nutrient cycling. Notoriously difficult sampling methods and the fractal distribution of root diameters in the soil make data being used in these models especially susceptible to error resulting from under‐sampling. We applied the concept of species accumulation curves to root data to quantify the extent of under‐sampling inherent to minirhizotron and soil coring sampling for both root uptake and carbon content studies. Based on differences in sample size alone, minirhizotron sampling missed approximately one third of the root diameters observed by soil core sampling. Sample volumes needed to encounter 90% of root diameters averaged 2481 cm³ for uptake studies and 5878 cm³ for root carbon content studies. These results show that small sample volumes encounter a non‐representative sample of the overall root pool, and provide future guidelines for determining optimal sample volumes in root studies.     

Phytoremediation of pesticide wastes in soil

Soils at agrochemical dealer sites often are contaminated with pesticide residues from decades of accidental and incidental spillage. We have determined that prairie grasses native to the Midwestern U.S. are suitable for phytoremediation because they are tolerant of most herbicides and of climatic extremes, such as heat, cold, drought, and flooding. A mixed stand of big bluestem, switch grass, and yellow indiangrass develops a rhizosphere with microflora that can readily detoxify pesticide residues. Specific atrazine-degrading bacteria or the free enzyme atrazine chlorohydrolase also can enhance the rate of biotransformation of atrazine in soil. Metolachlor degradation can be accelerated significantly by the prairie grass/rhizosphere effect. Several grasses used in filter strips have also been evaluated for their pesticide-degradation capabilities. The prairie grasses also have been demonstrated to reduce the rates of leaching of pesticides through intact soil columns, since less water leaches out of vegetated soil columns compared to non-vegetated soil columns. The evaluation of the degree of success of remediation has relied heavily on chemical residue analysis, but recent studies on biological endpoints have shown promise for providing more ecologically relevant indications of the potential exposure of organisms to pesticides in the soil. Earthworm 8-day bioaccumulation assays and root growth assays have shown the value of assessing the bioavailability of the residues. Mass balance experiments have utilized radiolabeled atrazine and metolachlor to ascertain the complete metabolism and binding profile of those two pesticides in phytoremediation studies.     

Method of soil column preparation for the evaluation of viral transport.

A method for packing soil columns to investigate viral transport phenomena is described. The columns were 10 cm in diameter and ranged from 33 to 100 cm in length. Field conditions of the soil, including bulk density and profile, were reproduced in columns. Ionic gradients resulting from sequential applications of wastewater and distilled water affected the movement of poliovirus I (Chat) through soil. Compared with 33-cm- and 66-cm-length columns, lower concentrations of infectious virions were observed in the percolates from 100-cm soil columns. These results may be attributed to the greater pore volume in the longer columns (the greater volume of soil contained in these columns), whereas the volume of liquid applied was constant for all columns.     

Method of soil column preparation for the evaluation of viral transport.

A method for packing soil columns to investigate viral transport phenomena is described. The columns were 10 cm in diameter and ranged from 33 to 100 cm in length. Field conditions of the soil, including bulk density and profile, were reproduced in columns. Ionic gradients resulting from sequential applications of wastewater and distilled water affected the movement of poliovirus I (Chat) through soil. Compared with 33-cm- and 66-cm-length columns, lower concentrations of infectious virions were observed in the percolates from 100-cm soil columns. These results may be attributed to the greater pore volume in the longer columns (the greater volume of soil contained in these columns), whereas the volume of liquid applied was constant for all columns.     

基于探地雷达的滨河带藤本和次生乔木林土壤优先流特征

滨河带是河流生态系统和森林生态系统的过渡带,该区域林分的土壤优先流特征对流域的地表水文过程会产生重要影响。探究土壤异质性与优先流的关系,为当地地下水安全和河流上下游水生态安全提供参考。本研究以永定河滨河带的藤本和次生乔木林两种植被为研究对象,结合传统亮蓝(Brilliant Blue FCF)染色示踪法,利用探地雷达(Ground Penetrating Radar, GPR)技术进行测线扫描。提取探地雷达图像的单道波形图,对反射波各参数与染色面积比进行拟合,并结合优先流染色特征进行分析。染色形态特征表明,藤本样地土壤染色形态呈现断离式零散分布,优先流发育带为土壤表层以下5—30 cm的土层深度,而次生乔木林土壤呈现大面积斑块状分布,优先流发育较为迟缓,其发育带为土壤表层以下10—25 cm的土层深度,且平均染色面积比藤本小1.68%。探地雷达测线表明,土层深度为0—15 cm时,最大振幅和总振幅面积均随土层的深度增加而下降,土层深度为15—35 cm时,两参数开始波动变化,且藤本样地的最大振幅和总振幅面积大于次生乔木林样地。经拟合发现,染色面积比与最大振幅呈y=25.104lnx+2...     

A Quantitative Approach for Ranking Human Health Risks from Pesticides in Irish Groundwater

This study aims to quantitatively assess the risk of pesticides (used in Irish agriculture) and their degradation products to groundwater and human health. This assessment uses a human health Monte-Carlo risk-based approach that includes the leached quantity combined with an exposure estimate and the No Observed Adverse Effect Level (NOAEL) as a toxicity ranking endpoint, resulting in a chemical intake toxicity ratio statistic (R) for each pesticide. A total of 34 active substances and their metabolites registered and used in the agricultural field were evaluated. MCPA obtained the highest rank (i.e., in order of decreasing human health risk), followed by desethly-terbuthylazine and deethylatrazine (with risk ratio values of 1.1 × 10^?5, 9.5 × 10^?6, and 5.8 × 10^?6, respectively). A sensitivity analysis revealed that the soil organic carbon content and soil sorption coefficient were the most important parameters that affected model predictions (correlation coefficient of –0.60 and –0.58, respectively), highlighting the importance of soil and pesticide properties in influencing risk estimates. The analysis highlights the importance of taking a risk-based approach when assessing pesticide risk. The model can help to prioritize pesticides, with potentially negative human health effects, for monitoring programs as opposed to traditional approaches based on pesticide leaching potential.     

Glyphosate utilization byPseudomonas sp. andAlcaligenes sp. isolated from environmental sources

A total of 21 bacterial cultures were isolated that could utilize glyphosate (N-phosphonomethyl glycine) as a sole source of phosphorus in a mineral salts medium. Sources of inocula for enrichment cultures included aerobic digester liquid, raw sewage, trickling filter effluent, pesticide disposal pit liquid, and soil. Eleven cultures were identified asPseudomonas sp., one asPseudomonas stutzeri, and nine asAlcaligenes sp. Aminomethylphosphonic acid, the major metabolic intermediate of glyphosate degradation in soil, could also serve as a sole phosphorus source for all 21 isolates. Neither glyphosate nor aminomethylphosphonic acid could serve as carbon sources in mineral salts media. Experiments withPseudomonas sp. SG-1 (isolated from aerobic digester liquid) suggested that enzymatic activity responsible for glyphosate degradation was intracellular, inducible, and required the cofactors pyruvate and pyridoxal phosphate. The degradation pathway for glyphosate in this culture may be similar to that previously reported for aminoethylphosphonic acid.     

Pesticide dissipation and microbial community changes in a biopurification system: influence of the rhizosphere

The dissipation of atrazine, chlorpyrifos and iprodione in a biopurification system and changes in the microbial and some biological parameters influenced by the rhizosphere of Lolium perenne were studied in a column system packed with an organic biomixture. Three column depths were analyzed for residual pesticides, peroxidase, fluorescein diacetate activity and microbial communities. Fungal colonization was analyzed by confocal laser scanning microscopy to assess the extent of its proliferation in wheat straw. The L. perenne rhizosphere enhanced pesticide dissipation and negligible pesticide residues were detected at 20–30 cm column depth. Atrazine, chlorpyrifos and iprodione removal was 82, 89 and 74% respectively in the first 10 cm depth for columns with vegetal cover. The presence of L. perenne in contaminated columns stimulated peroxidase activity in all three column depth sections. Fluorescein diacetate activity decreased over time in all column sections with the highest values in biomixtures with vegetal cover. Microbial communities, analyzed by PCR-DGGE, were not affected by the pesticide mixture application, presenting high values of similarity (>65%) with and without vegetal cover. Microbial abundance of Actinobacteria varied according to treatment and no clear link was observed. However, bacterial abundance increased over time and was similar with and without vegetal cover. On the other hand, fungal abundance decreased in all sections of columns after 40 days, but an increase was observed in response to pesticide application. Fungal colonization and straw degradation during pesticide dissipation were verified by monitoring the lignin autofluorescence loss.     

基于酶生物传感器法检测果蔬中毒死蜱残留的提取工艺研究

使用自主研制的酶生物传感器型农残检测仪进行农药残留检测,通过筛选可测果蔬种类、调整优化样品处理大小、样品加标后静置时间、样品与提取液比例和振荡提取速度,提高检测用酶对农药的抑制敏感性,从而达到降低农药检出限、提高回收率的目的。主要设置的参数如下:样品处理方式分为打碎、切碎(切成1 cm×1 cm和1. 5 cm×3 cm大小);加标后静置时间为5 min、15min、30 min、60 min和90 min;料液比为1∶1、1∶2. 5、1∶5、1∶7. 5和1∶10;振荡提取速度为0 r/min、110 r/min、190 r/min和225 r/min;主要测定的农药为毒死蜱。结果发现,不同果蔬品种对固定化酶的抑制率影响小,样品大小为1 cm×1 cm、加标后静置时间为5 min、料液比为1∶1、加入提取剂后的振荡速度为190 r/min为最佳前处理方式组合。酶生物传感器农残检测仪能够满足快速检测果蔬中有机磷农药残留的需要。     

小型植保无人机超低量喷雾防治稻水象甲

【目的】通过建立适宜新疆荒漠绿洲特殊生态环境的稻水象甲超低量喷雾技术,为稻水象甲的大面积统防统治提供新型施药技术。【方法】以小型遥控多旋翼植保无人机(UAV)为施药机械,以稻水象甲常规喷雾防效大于90%的药剂为首选药剂,开展了药剂、施药量、助剂以及施药机型的筛选试验。【结果】施药后3、7、14和21 d虫口密度高于防治指标的样地所占比例依次为35.71%、21.43%、35.71%和78.57%。30%氯虫·噻虫嗪187.5 mL·hm~(-2)防效最佳,14 d药效高达93.43%;药后21 d,球孢白僵菌3000 mL·hm~(-2)的防效最高,达84.65%。各药剂施药量与防效呈正相关。此外,UAV喷雾防治稻水象甲时,添加助剂的平均防效可提高22.29%~28.49%。【结论】在农业精准施药、绿色生产中,综合考虑供试药剂的施药量、持效期、防效和药后存活虫量,建议以30%氯虫·噻虫嗪SC和14%氯虫·高氯氟CS作为全程以UAV为施药机械防治稻水象甲的首选药剂,在稻水象甲种群发展前中期优先考虑低浓度施药量;同时,为避免UAV在实际作业中药液雾滴发生飘失和流失问题,可以考虑添加飞防助剂提升防效。     

A comparison of sampling methods for bibionid larvae (Diptera: Bibionidae) in grassland

Three extraction methods were compared for the recovery of bibionid larvae from grassland soil samples. Only wet-sieving followed by flotation in a saturated salt solution yielded bibionids. No larvae were recovered either with modified Tullgren funnels or by slow immersion of soil cores into a saturated salt solution. The efficiency with which larval bibionid populations can be estimated is poor. Generally, smaller cores yielded more larvae per volume of soil. Most bibionids were found in the top 4 cm of soil. It is concluded that 10 cm diameter and 6–8 cm deep soil cores are an acceptable compromise between efficiency and sampling effort but sample size will largely be determined by the resources available for processing of samples.     

Temperature dependence on the pesticide sampling rate of polar organic chemical integrative samplers (POCIS)

Laboratory experiments were performed to determine the sampling rates of pesticides for the polar organic chemical integrative samplers (POCIS) used in Japan. The concentrations of pesticides in aquatic environments were estimated from the accumulated amounts of pesticide on POCIS, and the effect of water temperature on the pesticide sampling rates was evaluated. The sampling rates of 48 pesticides at 18, 24, and 30 °C were obtained, and this study confirmed that increasing trend of sampling rates was resulted with increasing water temperature for many pesticides.     

Influence of geographic database scale on prediction of groundwater vulnerability to pesticides

Selection of optimal locations for sampling of groundwater is an important aspect of determining the fate of pesticides in the environment. For large land areas such as states and counties, the interaction of physical and chemical properties of soil, geologic strata, and pesticide molecule are quite complicated and highly variable. This article presents information that shows that the scale of the database influences not only the prediction of the vulnerability of ground‐water to pesticides, but also the areal coverage. In this study, the statewide agricultural pesticide in groundwater model was modified to evaluate the vulnerability of the uppermost aquifer in Woodruff County, AR, to pesticides. The state scale model used soil, geological, and topological databases on a 1:500,000 scale. In contrast, the county‐scale model used databases that were specific to the data layer rather than inferred and used soils at a 1:24,000 scale. A land use component was added to both models to reflect where pesticides are possibly applied in the county. The predictive ability of the two models was compared for nine wells previously sampled for pesticides. On the average, the county‐scale model had higher indices for the wells, indicating a greater vulnerability of groundwater to pesticides at these locations. At the well site where the highest concentration of a pesticide was found, the county‐scale model had a considerably higher vulnerability index.     

Modeling Dicamba Sorption and Transport Through Zoysiagrass Thatch and Soil

The presence of turfgrass thatch complicates the sorption and transport of water soluble pesticides because the surface-applied pesticides must pass through an organic-rich thatch layer prior to entering the soil. The study was conducted (1) to determine the impact of zoysiagrass thatch (Zoy-sia japonica Steud.) on dicamba (3,6-dichloro-2-methoxy benzoic acid) transport through soil columns, and (2) to evaluate the effectiveness of linear equilibrium (LEM), two site nonequilibrium (2SNE) and one site nonequilibrium (1SNE) models to predict dicamba transport through columns containing a surface layer of thatch and columns devoid of thatch. The equilibrium sorption isotherms of ¹⁴C dicamba to homogenized samples of zoysiagrass thatch and a Sassafras loamy sand soil (fine loamy, mixed mesic, Typic Hapludult) were determined. Following the application of bromide to determine transport parameters, 0.56?kg dicamba ha^?1 was surface applied to undisturbed soil columns containing a surface layer of thatch and columns devoid of thatch and leachate samples collected for 12?h under steady-state unsaturated conditions. Zoysiagrass thatch (Kf = 0.82) had a three times greater sorption capacity than the soil (Kf = 0.28) beneath the thatch. Dicamba leaching for columns with thatch layers was ca. 21% less than soil columns devoid of thatch. When dicamba breakthrough curves were fitted to the different forms of the convective dispersive equation, the 2SNE model simulated dicamba transport better than LEM and 1SNE models, indicating the presence of two-site nonequilibrium sorption. Indications are that turfgrass thatch may have significant effects on dicamba leaching that presently used regulatory models based on LEM approach do not adequately consider.     

Effects of soil structural discontinuity on root and shoot growth and water use of maize

The role of roots penetrating various undisturbed soil horizons beneath loose layer in water use and shoot growth of maize was evaluated in greenhouse experiment. 18 undisturbed soil columns 20 cm in diameter and 20 cm in height were taken from the depths 30–50 cm and 50–70 cm from a Brown Lowland soil, a Pseudogley and a Brown Andosol (3 columns from each depth and soil). Initial resistance to penetration in undisturbed soil horizons varied from 2.5 to 8.9 MPa while that in the loose layer was 0.01 MPa. The undisturbed horizons had a major effect on vertical arrangement of roots. Root length density in loose layer varied from 96 to 126 km m^-3 while in adjacent stronger top layers of undisturbed horizons from 1.6 to 20.0 km m^-3 with higher values in upper horizons of each soil. For specific root length, the corresponding ranges were 79.4–107.7 m g^-1 (on dry basis) and 38.2–63.7 m g^-1, respectively. Ratios of root dry weight per unit volume of soil between loose and adjacent undisturbed layers were much lower than those of root length density indicating that roots in undisturbed horizons were produced with considerably higher partition of assimilates. Root size in undisturbed horizons relative to total roots was from 1.1 to 38.1% while water use from the horizons was from 54.1 to 74.0%. Total water use and shoot growth were positively correlated with root length in undisturbed soil horizons. There was no correlation between shoot growth and water use from the loose layers.     

Phytoremediation of groundwater contaminated with pesticides using short-rotation willow crops: A case study of an apple orchard

The occurrence of pesticides in groundwater represents an important health issue, notably for population whose drinking water supply source is located in agricultural areas. However, few solutions have been considered with regard to this issue. We tested the efficacy of a vegetal filtering system made of shrub willows planted at a high density (16,000 plants ha^?1) to filter or degrade pesticides found in the groundwater flowing out of an apple orchard. Ethylene urea (EU), ethylene thiourea (ETU), tetrahydrophthalimide (THPI), atrazine, and desethylatrazine were monitored in the soil solution in willow and control plots over one growing season. ETU and atrazine concentrations were lower in the willow plots relative to the control plots, whereas desethylatrazine concentration was higher in the willow plots. No significant difference was detected for EU and THPI. Furthermore, pesticide concentrations displayed complex temporal patterns. These results suggest that willow filter systems can filter or degrade pesticides, notably ETU and atrazine, and could be used for phytoremediation purposes. Yet, this potential remains to be quantified with further studies using experimental settings allowing more estimation in time and space.