Search

Temperature variation will affect the prediction accuracy when using the near-infrared (NIR) analytical model to measure the viscosity of bisphenol-A. In order to correct the effect of temperature on the prediction performance of NIR model, a multilevel least-absolute shrinkage and selection operator (LASSO) is proposed in this paper. The multilevel LASSO algorithm combines LASSO with the multilevel simultaneous component analysis (MLSCA) to enhance the robustness of the model under temperature changes and external disturbances. MLSCA is applied to decompose the molecular spectral data into two parts. One part denotes the property caused by temperature, the other means the changes of concentration. LASSO, a sparse regression model, is used to select the variables and perform the regularization to further enhance the robustness and interpretability of the model. Experimental results demonstrate the effectiveness of the proposed model in measuring bisphenol-A viscosity, which provides a more stable prediction result compared with the existing ones without temperature corrections. • Effect of temperature on viscosity analysis of bisphenol-A is firstly studied. • Multilevel least absolute shrinkage and selection operator is proposed to correct for temperature fluctuation and external disturbance. • The accuracy and robustness of Near-infrared analytical model has been simultaneously improved given temperature variation and external disturbance. • Multilevel simultaneous component analysis is used to split the spectral data into between-part and within-part for the purpose of eliminating temperature influence. • The quantitative relationship between within-part and concentration is built by least absolute shrinkage and selection operator, which is capable to select characteristic wavelengths at the same time. • Experimental results of viscosity measurement for bisphenol-A with temperature variation are compared with PLS-based temperature model and MLPCR model. [ABSTRACT FROM AUTHOR]

The filamentous fungus Trichoderma koningii is capable of fast and effective eliminate alachlor (90% after 72 h when added separately and 80–60% in the presence of 1–5 mM of copper). After 168 h over 99% elimination of alachlor resulted in detoxification and was connected with the mitigation of reactive oxygen species (ROS) production. Using MS/MS techniques, seven dechlorinated and hydroxylated metabolites were identified. Cytochrome P450 and laccase participate in biotransformation of the herbicide by this non-ligninolytic fungus. Laccase activity is stimulated both by copper and the mixture of copper and alachlor, which seems to be important for combined pollutants. T. koningii is characterized by high tolerance to copper (up to 7.5 mM). The metal content in mycelia reached 0.9–7.76 mg in 1 g of dry biomass. Our results suggest that T. koningii strain seems to be a promising tool for bioremediation of agricultural areas co-contaminated with copper-based fungicides and chloroacetanilide herbicides. [ABSTRACT FROM AUTHOR]

Lignocellulosic wastes and by-products containing lignin are now available in large amounts from forestry and industrial activities, and could be promising organic materials for the biosorption of pesticides by soils in order to reduce point-source pollution. Adding these materials to soil requires understanding the process of pesticide sorption-desorption by wood-soils, as sorption capacity could increase, with changes in pesticide bioavailability and final fate. The objective of this work was to study the effect that pine and oak wood added to soils had on the sorption/desorption of the pesticides linuron, alachlor, and metalaxyl. Experiments were conducted with two sandy loam and sandy clay soils each amended with two wood doses (5% and 50%) after different incubation times (0, 5 and 12 months). A low wood dose (5%) had no significant impact on the sorption (K f ) of alachlor, but K f increased for linuron (up to 5.4–1.7 times) and metalaxyl (up to 4.4 and 8.6 times) in all wood-soil systems. The results were not significantly different after different incubation times. The desorption results indicated that wood decreases the sorption irreversibility of alachlor, and increases that of linuron and metalaxyl, with a varying effect of the wood-soil incubation time. The addition of a high wood dose to soil (50%) was more significant for increasing the sorption of all the pesticides, and the sorbed amounts remaining after desorption (>49% for linuron, >33% for alachlor and >6% for metalaxyl), although there was no apparent discrimination between the two types of woods. The role of the nature of the organic carbón (K oc values) for sorption was evidenced for alachlor and metalaxyl, but not for linuron. These outcomes are of interest for extending wood application to soil as a barrier for avoiding environmental risk by point-source pollution due to the use and management of pesticides in farming systems. [ABSTRACT FROM AUTHOR]

Alachlor, a commonly used herbicide in agriculture, has been selected as a target pollutant to evaluate the oxidative performance of zero-valent iron (ZVI) coupling with persulfate (PS) for the first time. Compared with Fe 3+ and Fe 2+ , ZVI achieved the best degradation effect. Bench-scale kinetics tests were conducted to demonstrate the impacts of several key factors controlling the treatment performance, including ZVI dosage, PS dosage, initial pH, temperature, nature organic matter (NOM), citrate and anions. The alachlor degradation followed a pseudo-first-order kinetics pattern and was effective in a broader pH range. The optimum ZVI to PS molar ratio was found to be 2:1. Heat could facilitate production of sulfate radicals and thus enhance the alachlor degradation. Sodium citrate as a chelating agent at an appropriate concentration could improve the alachlor decay in the Fe 2+ +PS and ZVI+PS system. The removal was strongly inhibited in system added NOM, anions of Cl − or HCO 3 − while it was not obvious impacted by adding NO 3 − or SO 4 2 − . Seven proposed degradation pathways were evaluated, using Liquid Chromatography–Mass Spectroscopy (LC–MS) analysis. In conclusion, ZVI+PS can be as a potential technology for purifying alachlor-polluted water. [ABSTRACT FROM AUTHOR]

The article investigates trends in concentration and loads of acetochlor, alachlor, and metolachlor and their ethanasulfonic (ESA) and oxanilic (OXA) acid degradates from 1996 through 2006 in the main stem of the Iowa River and in the South Fork Iowa River. In general, acetochlor, alachlor, metochlor, and their ESA and OXA degradates were present in more than 50% of the samples collected from both sites. Their concentrations declined from 1996 through 2006, with the rate of decline being slower following 2001.

Abstract: Wormhole-shaped TiO2/Ti photoelectrodes were prepared by microarc oxidation method in H2SO4 solution. The morphology and structure were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The photocatalytic (PC) activity of TiO2/Ti photoelectrodes was evaluated by the degradation rates of alachlor in aqueous solution. All results showed that their porous increased with the anodization voltage, and the crystal structure transferred from anatase to rutile TiO2. The photoelectrodes, which were anodized 10 min at 160 V in 0.5 M H2SO4 solution, were composed of mixed crystal structures of anatase and rutile TiO2 and have optimal PC performance. Alachlor was almost completely removed by TiO2/Ti photoelectrodes after 120 min under the illumination of 150W xenon light. [Copyright &y& Elsevier]

Abstract: Organochlorine pesticides (HCB, HCH with α-, β-, and γ isomers, heptachlor, cis-heptachlor epoxyde, trans-heptachlor epoxyde, endosulfan with α- and β isomers, sulfate endosulfan, o,p′-DDT, p,p′-DDT, o,p′-DDE, p,p′-DDE, o,p′-DDD, p,p′-DDD, chlorothalonil, alachlor, aldrin, dieldrin, methoxychlor, oxychlordane, chlordane with α- and γ isomers, p,p′-dicofol and o,p′-dicofol) and indicators PCBs (IUPAC nos. 28, 52, 101, 118, 138, 153, and 180) were studied both in sediments and muscles of farmed fish species (Cyprinus carpio and Perca fluviatilis). Samples were collected from fish ponds located in the hydrographic basin of the Moselle River (Lorraine Region, France). OCPs and PCBs were present at low concentrations both in sediments and fish muscles. Concerning sediments, ∑DDTs revealed concentrations ranging from 0.2 to 2.30ngg−1 dw and ∑PCBs ranged from 0.3 to 3.5ngg−1 dw. Concerning fish muscles, the highest concentrations in OCPs were those of p,p′-DDE, with average concentrations of 0.57±0.44ngg−1 ww for carp and 0.58±0.29ngg−1 ww for perch. The contamination profiles proved to be different depending on the fish species. Indeed, HCH-isomers, HCB, and dieldrin were detected only for the carp and always at low concentrations. For example, the highest concentration of HCHs was observed for β-HCH with a mean value of 0.64±0.15ngg−1 ww for carp. As for PCBs, the levels of ∑PCBs ranged from 0.3 to 6.4ngg−1 ww in carp muscles and from 0.90 to 5.60ngg−1 ww in perch muscles. [Copyright &y& Elsevier]

The sorption of alachlor is one of the most important behaviors of transference and transformation of alachlor in soils, and it also plays significant role in the soil environment. Three soil samples were collected from the suburb farmland of Jiamusi (S1), Yilan (S2) and Harbin (S3) along the Songhua River (Northeast, China), and batch experiments were conducted to investigate the effects of dissolved organic matter (DOM) on the adsorption-desorption behavior of alachlor in soil-water system. The results showed that the adsorption capacity of alachlor was suppressed significantly after adding DOM into soil-water system, yet the DOM might accelerate the desorption process of alachlor from soil. The adsorption and desorption isotherms for alachlor in the soil samples were found to fit well with the Freundlich model ( R² > 0. 858 ) and the order of adsorption capacity of the soil samples was in the order of S1 > S2 > S3. Hysteresis Index showed that the hysteresis existed in the adsorption-desorption process of alachlor. [ABSTRACT FROM AUTHOR]

The article presents a study to determine if the use of glyphosate instead of residual herbicides used in corn production results in reduced losses of herbicide in surface runoff in the U.S. The study applied the herbicide to chisel-plowed and no-till watersheds. The study reveals less losses of atrazine, alachlor and linuron when glyphosate was applied to all tillage practices. It notes that glyphosate-tolerant corn planting and soybean using glyphosate reduces the impact of the production of corn on surface water quality.

The application rates for conventional herbicide formulations are generally greater than the recommended dosage, in order to overcome losses from degradation, leaching, volatilization, and sorption during the time needed for weed control. All these factors have encouraged the development of controlled release formulations (CRFs), which can reduce herbicides levels in the environment since less active ingredient need to be applied for maintaining the herbicidal efficacy. For soil applied herbicides, such as alachlor and norflurazon, the residual weed control is dependent on herbicide persistence and availability in soil. The present study describes the preparation, characterization and application to soil of CRFs containing the herbicides norflurazon and alachlor. Ethylcellulose formulations were obtained by a microencapsulation technique. The results of the in vitro release studies in water showed that a prolonged release of the herbicides to solution was successfully achieved by using ethylcellulose microspheres. In order to compare the herbicidal efficacy and persistence of norflurazon and alachlor applied as microencapsulated formulations with the commercial formulations, bioassay experiments were carried out. The formulations were applied as preemergence herbicides at 0.8 and 1.6 mg kg-1 for norflurazon and alachlor, respectively, and oat (soils treated with alachlor) and soybean (soils treated with norflurazon) seeds were sown. The herbicide persistence in soil was studied sowing fresh seeds in each pot at different times after herbicides treatment. The results showed that the ethylcellulose microencapsulated formulations of norflurazon and alachlor protected the herbicides against their dissipation in soil, and remained biologically active longer than the commercial formulations. [ABSTRACT FROM AUTHOR]

The article provides information on a study that investigated the effect of claypan soils at initial field capacity versus permanent wilting level on atrazine and alachlor transport. It evaluates the effects of highly contrasting antecedent soil water content on herbicide transport and degradation. It identifies the impact that shrinkage cracks have for different moisture conditions on preferential transport of herbicides in claypan soils. The methodology and results of the study are discussed. Simulation models for claypan soils will improve by understanding the effects of preferential flow paths on herbicide transport.

This article discusses the rates of herbicide losses of transgenic corn and soybean under crop rotation and various tillage systems in Ohio. They compared the concentrations of glyphosate and glufosinate in runoff water with residual herbicides metribuzin, alachlor, linuron and atrazine. They found that maximum, annual flow weighted concentrations of alachlor and atrazine could exceed their maximum contaminant level for drinking water regardless of tillage system. They concluded that glufosinate and glyphosate can replace these herbicides and can reduce dissolved herbicide concentrations in runoff which might have exceeded drinking water standards.

The article offers information about a study that measured losses of alachlor, atrazine, linuron, and metribuzin from seven small watersheds for nine years to investigate whether a reduced-input system for corn and soybean production with light disking, cultivation, and half-rate herbicide applications could reduce losses compared with chisel and no-till. Results showed that while banding and half-rate applications as part of a reduced-input management practice reduced herbicide loss, concentrations of some herbicides may still be a concern. Furthermore, regardless of tillage practice, a small number of runoff events, usually shortly after herbicide application, dominated herbicide transport.

Focuses on the Acetochlor Registration Partnership State Ground Water Monitoring Program conducted in Illinois, Indiana, Iowa, Kansas, Minnesota, Nebraska and Wisconsin. Quantification of alachlor, atrazine, metolachlor and two classes of soil degradates for acetochlor, alachlor and metolachlor; Geographic distribution of detections of herbicides in shallow ground water; Occurrence of surface water drainage features, irrigation practices and the vertical positioning of the well screen.

The performance of a narrow buffer strip in abating dissolved P, electrical conductivity and herbicides (terbuthylazine, alachlor, nicosulfuron, pendimethalin, linuron) in subsurface water coming from cropland was tested in an experiment carried out on the low plains of the Veneto Region (NE Italy). The experiment lasted from December 1997 to June 1999, monitoring subsurface water quality entering and exiting a buffer composed of a grass strip (5 m wide) and 1 m wide row of trees. Dissolved phosphorus concentrations were reduced by almost 100% passing through the buffer and in most cases exiting water satisfied the limit for avoiding eutrophication. A positive effect was also detected on ECW (reduced by 20%), while pH was not significantly altered. Herbicide concentration abatement varied between 60 and 90%, depending on the chemical and the time elapsed since application. [Copyright &y& Elsevier]

Focuses on the assessment of the feasibility of using waste green sand as a low-cost reactive medium for treating ground water contaminated with alachlor and metolachlor. Determination of transport parameters and reaction rate constants for the herbicides; Reduction in concentration of alachlor and metolachlor for seepage velocities; Impact of the organic carbon and clay in green sands.

Assesses the environmental risk of alachlor and bentazone losses from subsurface drainage of two soils. Contamination of drainage water by bentazone and alachlor; Detection of herbicide residues in drainage; Indication of herbicide leaching.

Herbicides transported to surface waters by agricultural runoff are partitioned between solution and solid phases. Conservation tillage that reduces upland erosion will also reduce transport of herbicides associated with the solid phase. However, transport of many herbicides occurs predominantly in solution. Conservation tillage practices may or may not reduce transport of solution‐phase herbicides, as this depends on the runoff volume. Reducing herbicide application rate is another approach to minimize off‐site transport. Herbicide banding can reduce herbicide application rates and costs by one‐half or more. Our objective was to compare herbicide losses in runoff from different tillage practices and with band‐ or broadcast‐applied herbicides. The herbicides alachlor [2‐chloro‐2′,6′‐diethyl‐N‐(methoxymethyl)acetanilide] and cyanazine [2‐[[4‐chloro‐6‐(ethylamino)‐1,3,5‐triazin‐2‐yl]amino]2‐methylpropionitrile] were broadcast‐ or band‐applied to plots managed in a moldboard plow, chisel plow, or ridge till system. Herbicide concentration in runoff was largest for the first runoff event occurring after application and then decreased in subsequent events proportional to the cumulative rain since the herbicide application. When herbicides were broadcast‐applied, losses of alachlor and cyanazine in runoff followed the order: moldboard plow > chisel plow > ridge till. Conservation tillage systems reduced runoff loss of herbicides by reducing runoff volume and not the herbicide concentration in runoff. Herbicide banding reduced the concentration and loss of herbicides in runoff compared with the broadcast application. Herbicide losses in the water phase averaged 88 and 97% of the total loss for alachlor and cyanazine, respectively. Cyanazine was more persistent than alachlor in the soil. [ABSTRACT FROM AUTHOR]

To improve understanding of the factors affecting pesticide occurrence in ground water, patterns of detection were examined for selected herbicides, based primarily on results from the National Water‐Quality Assessment (NAWQA) program. The NAWQA data were derived from 2227 sites (wells and springs) sampled in 20 major hydrologic basins across the USA from 1993 to 1995. Results are presented for six high‐use herbicides—atrazine (2‐chloro‐4‐ethylamino‐6‐isopropylamino‐s‐triazine), cyanazine (2‐[4‐chloro‐6‐ethylamino‐1,3,5‐triazin‐2‐yl]amino]‐2‐methylpropionitrile), simazine (2‐chloro‐4,6‐bis[ethylamino]‐s‐triazine), alachlor (2‐chloro‐N‐[2,6‐diethylphenyl]‐N‐[methoxymethyl]acetamide), acetochlor (2‐chloro‐N‐[ethoxymethyl]‐ N‐[2‐ethyl‐6‐methylphenyl]acetamide), and metolachlor (2‐chloro‐N‐[2‐ethyl‐6‐methylphenyl]‐N‐[2‐methoxy‐1‐methylethyl]acetamide)— as well as for prometon (2,4‐bis[isopropylamino]‐6‐methoxy‐s‐triazine), a nonagricultural herbicide detected frequently during the study. Concentrations were <1 μg L−1 at 98% of the sites with detections, but exceeded drinking‐water criteria (for atrazine) at two sites. In urban areas, frequencies of detection (at or above 0.01 μg L−1) of atrazine, cyanazine, simazine, alachlor, and metolachlor in shallow ground water were positively correlated with their nonagricultural use nationwide (P < 0.05). Among different agricultural areas, frequencies of detection were positively correlated with nearby agricultural use for atrazine, cyanazine, alachlor, and metolachlor, but not simazine. Multivariate analysis demonstrated that for these five herbicides, frequencies of detection beneath agricultural areas were positively correlated with their agricultural use and persistence in aerobic soil. Acetochlor, an agricultural herbicide first registered in 1994 for use in the USA, was detected in shallow ground water by 1995, consistent with previous field‐scale studies indicating that some pesticides may be detected in ground water within 1 yr following application. The NAWQA results agreed closely with those from other multistate studies with similar designs. [ABSTRACT FROM AUTHOR]

Several environmental pollutants, including pesticides, herbicides and persistent organic pollutants play an important role in the development of chronic diseases. However, most studies have examined environmental pollutants toxicity in target organisms or using a specific toxicological test, losing the real effect throughout the ecosystem. In this sense an integrative environmental risk of pollutants assessment, using different model organisms is necessary to predict the real impact in the ecosystem and implications for target and non-target organisms. The objective of this study was to use alachlor, a chloroacetanilide herbicide responsible for chronic toxicity, to understand its impact in target and non-target organisms and at different levels of biological organization by using several model organisms, including membranes of dipalmitoylphosphatidylcholine (DPPC), rat liver mitochondria, bacterial (Bacillus stearothermophilus), plant (Lemna gibba) and mammalian cell lines (HeLa and neuro2a). Our results demonstrated that alachlor strongly interacted with membranes of DPPC and interfered with mitochondrial bioenergetics by reducing the respiratory control ratio and the transmembrane potential. Moreover, alachlor also decreased the growth of B. stearothermophilus and its respiratory activity, as well as decreased the viability of both mammalian cell lines. The values of TC 50 increased in the following order: Lemna gibba < neuro2a < HeLa cells < Bacillus stearothermophilus. Together, the results suggest that biological membranes constitute a putative target for the toxic action of this lipophilic herbicide and point out the risks of its dissemination on environment, compromising ecosystem equilibrium and human health. [Display omitted] • A multi toxicological model using in vitro , bacterial and animal systems improved the prediction of Alachlor-induced environmental risk. • Alachlor strongly interacted with membranes of DPPC and interfered with mitochondrial bioenergetics. • Alachlor decreased the growth of B. stearothermophilus and reduced the viability of mammalian cells. • Alachlor decreased the proliferation of Lemna gibba. • Biological membranes may constitute a putative target for the toxic action of this lipophilic herbicide and point to the risks of its dissemination on environment, compromising ecosystem equilibrium and human health. [ABSTRACT FROM AUTHOR]

A soil‐column laboratory experiment and a 2‐yr field‐sampling study evaluated the overall dissipation of alachlor [2‐chloro‐N‐(2,6‐diethylphenyl)‐N‐(methoxymethyl) acetamide]. Theses studies also measured the effect of no‐till and chisel‐plow tillages on alachlor leaching and dissipation. In the top 30 cm layer of soil, the overall half‐life was 3 d or less, and the time to 90% dissipation ranged from 17 to 30 d. In no‐fill soil, alachlor dissipated slightly faster, and more was transported into the 10 to 30 cm soil layer. Weather conditions promoting the movement of alachlor into the soil, however, weakened the effect of tillage on the dissipation rate. Most of the alachlor present in the soil, regardless of tillage, was found in the top 10 cm at all times. Of the alachlor applied to 30‐cm tall soil columns, only 0.4% was removed by water flowing from chisel‐plow columns and 1.6% from no‐till columns. The results show that tillage was not a key factor in alachlor dissipation and leaching. Alachlor leaching was also a minor component in overall dissipation. [ABSTRACT FROM AUTHOR]

A field experiment was conducted in a randomized complete block design with triplicates to evaluate the effects of herbicide alachlor on weed, growth and yield parameters of maize. The seeds were subjected to preliminary germination study and the selected concentrations were applied (1.0, 2.5, 5.0, 7.5 and 10.0 ppm) followed by seed sowing and the treatments were compared with control. The maximum weed growth was recorded in the experimental site without herbicide treatment. At higher concentrations of the herbicide treatment the maize plants showed different types of morphological changes like improper leaf curling, malformation of leaf, stunted growth. The total weed dry weight showed considerable difference in all the concentrations treatments and least fresh weight was observed in weed free check (1.9 g) plot and the dry weight of weeds was also significantly different in different concentrations of herbicide. The weed control efficiency was increased as the concentrations of the herbicide increased and the maximum and minimum WCE (97.67% and 28.97%) was recorded in 10.0 and 1.0 ppm respectively. The weed index also found to be significantly increased from 6.87 to 91.7% as the herbicide concentrations increased from 1.0 to 10.0 ppm respectively. The yield associated parameters like height of the plants, number of leaves and cobs, length of cobs, weight of cob and grains weight were found to be significantly different under different concentrations of herbicide treatment. • The present study describes the efficacy of herbicide alachlor on maize. • Field experiment was conducted in a RCBD to evaluate the alachlor on different parameters of maize. • The application of herbicide showed different types of morphological changes like improper leaf curling, malformation of leaf, stunted growth. [ABSTRACT FROM AUTHOR]

This work provides the first spatial distribution report of micropollutants (MPs) in the entire Portuguese coast, comprising the ocean shore (sea water, SW) and whenever possible the nearest river discharging on it (estuarine water, EW). This surface water monitoring programme aimed to assess the spatial distribution of 37 MPs with a wide chemical nature, including some substances prioritized by the European Union Directive 39/2013/EU and contaminants of emerging concern targeted in the Watch List of Decisions 495/2015/EU and 840/2018/EU. The risk quotients were estimated in each sampling point for the detected MPs. High concentrations of diclofenac, tramadol and carbamazepine were determined, the latter with medium to high risk for algae. Some pharmaceuticals and perfluorooctanesulfonic acid (PFOS) were broadly distributed, maybe due to the direct discharge into the sea. Atrazine and alachlor were found in the majority of the samples, with alachlor levels often considered as medium to high risk. Unlabelled Image • 38 micropollutants were investigated along the Portuguese coast. • Atrazine was the most frequently detected compound in both estuarine and sea water. • Pharmaceuticals were found more often near highly urbanized areas. • PFOS, EHMC and pesticides were largely spread. • Only norfluoxetine, imidacloprid and methiocarb were never detected. [ABSTRACT FROM AUTHOR]

The extensive application of the herbicides for weed control in modern agriculture practices exerts a risk on various crop plants by way of chromosomal damage to the plants. In the current study the cytological effects of alachlor was studied in the root tip cells of maize and soybean. The maize and soybean were subjected to different concentrations of alachlor treatment (1.0–10.0 ppm and 1.0–8.0 ppm) respectively at room temperature. The mitotic index and relative division rate were decreased considerably as the herbicide concentrations increased, on the other hand the mitotic inhibition percentage and the relative abnormality rate was found to be increased as the herbicide concentration increased. The most frequently occurred chromosomal aberrations were nuclear lesion, sticky chromosome, sticky anaphase, sticky metaphase, chromosomal bridges and micronuclei. From the findings of the present study it can be concluded that alachlor might be responsible for the negative effects on cell division in maize and soybean. [ABSTRACT FROM AUTHOR]

Herbicides may contaminate groundwater when used over shallow aquifers. Alachlor [2-chloro-N-methoxymethyl-N-(2,6-diethylphenyl)-ac etamide] is widely used in corn (Zea mays L.) and soybean (Glycine mar L.)for grass control in eastern South Dakota where depth to groundwaterranges from <2 to >20 m. Sorption and degralotion of alachlor, two processes that control its fate in the environment, were measured in laboratory batch equilibrium and incubation studies. Surface soil and sediment samples from above and below the water table (~6 m below thesoil surface) were collected following aseptic procedures. Alachlor sorption to the surface A horizon soil (silty clay loam) was about 13times greater than sorption to the 2C horizon soil (sand and gravel). About 25% of the alachlor was completely mineralized after 112 din surface soil, whereas <0.5% was mineralized in the 2C horizon soils. The addition of C (lyophilized algae biomass) increased ring mineralization and polar metabolite formation in all samples. These data indicate that bacterial populations in the Big Sioux aquifer are sufficiently diverse to degrade complex organic molecules. Carbon was the factor most limiting alachlor metabolism in subsurface sediments. [ABSTRACT FROM AUTHOR]