Atrazine In Soil Research Articles

Bioavailability of Organoclay Formulations of Atrazine in Soil

Pesticide formulations based on organoclays have been proposed to prolong the efficacy and reduce the environmental impact of pesticides in soil. This research addressed the question of whether atrazine in organoclay-based formulations is irreversibly sorbed or is bioavailable for bacterial degradation in soil. Different cations of l-carnitine (CAR), tyramine (TYRAM), hexadimethrine (HEXADIM), phenyltrimethylammonium (PTMA), hexadecyltrimethylammonium (HDTMA), and Fe(III) were incorporated into Na-rich Wyoming montmorillonite (SWy-2) and Ca-rich Arizona montmorillonite (SAz-1) at 100% of the cation exchange capacity (CEC) of the clays as a strategy to enhance the affinity of the clay minerals for atrazine. A Buse loam soil from Becker, MN, was treated with three organoclay-based formulations of 14C-atrazine or free herbicide and incubated for 2 weeks. To determine the bioavailability of 14C-atrazine, the soil was inoculated with Pseudomonas sp. strain ADP, which rapidly mineralizes atrazine. At day 0, and after a 2 week incubation, mineralization and the amount of 14C-atrazine residues distributed between the aqueous-extractable, methanol-extractable, and bound fractions in the soil were determined to characterize the availability of nonaged and aged atrazine residues. By the end of the 2 week incubation, the microorganisms had mineralized >80% of the initial readily available (water-extractable) and >70% of the less readily available (methanol-extractable) 14C-atrazine in the soil. Bound residues increased from <4% at day 0 to ∼17% after the 2 week incubation for both the formulated and free forms of atrazine. The results of these incubation experiments show that the bioavailabilities of atrazine were similar in the case of the organoclay formulations and as free atrazine. This indicated that whereas more atrazine was sorbed and less likely to be transported in soil, when formulated as organoclay complexes, it was ultimately accessible to degrading bacteria, so that the herbicide is likely to be naturally attenuated by soil microorganisms.

Atrazine is not readily mineralised in 24 temperate soils regardless of pre-exposure to triazine herbicides

Mineralisation of atrazine in soil has been shown to depend on previous exposure of the herbicide. In this study, 24 Danish soils were collected and screened for potential to mineralise atrazine. Six soils were chosen, because they had never been exposed to atrazine, whereas 18 soils were chosen because of their history of application of atrazine or the related compound terbuthylazine. None of the 24 soils revealed a mineralisation potential of more than 4% of the added atrazine within a 60 day timeframe. In an atrazine adapted French soil, we found 60% mineralisation of atrazine in 30 days. Cattle manure was applied in order to boost the microbial activity, and a 2–3% increase in the atrazine mineralisation was found in some of the temperate soils, while in the highly adapted French soil it caused a 5% reduction.

Impact of climatic and soil conditions on environmental fate of atrazine used under plantation forestry in Australia

We studied the leaching and dissipation of atrazine (2-chloro-4-ethylamino-6-isopropylamino-1, 3, 5-s-triazine) and its two principal metabolites (desethylatrazine and desisopropylatrazine) for more than two years through soil profiles at five forestry sites across Australia (representing subtropical, temperate and Mediterranean climatic conditions with rainfall ranging from 780 to 1536 mm yr −1). Following atrazine applications at local label rates, soil cores were collected at regular intervals (up to depths of 90–150 cm), and the residues of the three compounds in soil were analysed in composite samples using liquid chromatography. Bromide was applied simultaneously with atrazine to follow the movement of the soil water. While bromide ion rapidly leached through the entire profile, in most cases the bulk of atrazine, desethylatrazine and desisopropylatrazine remained in the top 45 cm of the soil profile. However, a small fraction of residue moved deeper into the soil profile and at a subtropical site (Toolara) trace levels (ng L −1) of atrazine and one of its metabolites (DEA) were detected in perched groundwater located at a depth of 1.8 m. Data on the total residues of atrazine in soil profiles from all sites except the Tasmanian site fitted a first-order decay model. The half-life of atrazine in surface soils at the subtropical sites (Toolara and Imbil) ranged from 11 to 21 days. Four separate applications of atrazine at Toolara resulted in a narrow range of half-lives (16 ± 3.6 days), confirming relatively rapid dissipation of atrazine under subtropical conditions (Queensland). In contrast, a prominent biphasic pattern of initial rapid loss followed by very slow phase of degradation of atrazine was observed under the colder temperate climate of Highclere (Tasmania). The data showed that while its 50% (DT 50) loss occurred relatively rapidly (36 days), more than 10% of herbicide residue was still detectable in the profile even a year after application (DT 90 = 375 days). The rate of dissipation of atrazine at warm subtropical Queensland sites (Imbil and Toolara) was 2–3 times faster than sites located in colder climate of Tasmania. The marked contrast in DT 50 values between subtropical and temperate sites suggest that climatic conditions (soil temperature) is one of the key factors affecting atrazine dissipation. At the Tasmanian site, the combination of leaching of the herbicide in subsoil and slower microbial activity at cooler temperatures would have caused a longer persistence of atrazine.

Matéria orgânica em quatro tipos de solos brasileiros: composição química e sorção de atrazina

Soil organic matter is the main sorptive soil compartment for atrazine in soils, followed in a minor scale by the inorganic fraction. In this study, the soil organic matter quality and atrazine sorption were investigated in four different soil types. The pedogenic environment affected the humification and therefore the chemical composition of the organic matter. The organic matter contribution to atrazine sorption was larger (60-83%) than that of the inorganic fraction. The organic matter capacity in retaining the herbicide was favoured by a higher decomposition degree and a smaller carboxylic substitution of the aliphatic chains.

Cleanup of atrazine-contaminated soils: ecotoxicological study on the efficacy of a bioremediation tool with Pseudomonas sp. ADP

To mitigate the environmental effects of atrazine, one of the cleanup strategies available is based on the use of atrazine-degrading bacteria. This work aimed to evaluate the efficacy of a previously developed bioremediation tool for atrazine-contaminated soils (combining bioaugmentation with Pseudomonas sp. ADP, hereafter designated as P. ADP, and biostimulation with citrate) on both soil habitat and retention functions, by performing ecotoxicological tests with standard soil and aquatic species. Soil microcosms (incorporating earthworms, collembolans, and plants) were spiked with three doses of Atrazerba FL, an atrazine commercial formulation: the recommended dose (RD; 2 L/ha), 10 × RD and 20 × RD to simulate overuse/accidental spills scenarios. The experiment included two main groups of treatments: (1) microcosms sprayed solely with Atrazerba, i.e., nonbioremediated soils (NB) and (2) microcosms sprayed with both Atrazerba and the bioremediation tool (addition of P. ADP plus citrate), i.e., bioremediated soils (B). Control microcosms with no herbicide or P. ADP plus citrate addition were also set up. Besides soil chemical analysis, the following ecotoxicological endpoints were assessed to monitor bioremediation: plant biomass production, earthworm reproduction, microalgae growth (in eluates—collected 5 and 10 days after the bioremediation treatment—and leachates—collected on day seven), and cladoceran reproduction (in soil eluates). In NB soils, all Atrazerba doses induced a severe reduction in plant biomass production, and no effects were found for earthworm’s reproduction. Eluates and leachates obtained from the NB soils caused deleterious effects on both microalgae growth and cladoceran reproduction. Chemical analysis showed that atrazine degradation was faster in B soils than in the correspondent NB soils. Data from toxicity tests indicated that test organism performance was enhanced in B soils and respective eluates and leachates, compared to the NB samples. In fact, for soils contaminated with 10 and 20 × RD Atrazerba doses, plant biomass production was significantly higher in the B soils than in the correspondent NB soils. Regarding the effects of soil bioremediation on the toxicity of soil eluates and leachates, for the soil contaminated with 10 × RD of Atrazerba, over a 5-day treatment period, both microalgae growth and cladoceran reproduction were significantly higher in water extracts obtained from the B soils when compared with the NB extracts and also similar to the control. By the contrary, for the highest Atrazerba dose tested (20 × RD), no significant differences were found on the toxicity of B and NB eluates toward both aquatic test organisms. However, for this same dose, after 7 days, microalgae growth was higher in B than in the NB leachates and similar to the control. Yet, after a longer bioremediation period of 10 days, eluates were also no longer toxic to both aquatic organisms. Based on atrazine soil chemical analysis, one can state that the addition of P. ADP plus citrate to the atrazine-contaminated soils was clearly effective in promoting atrazine biodegradation. In addition, ecotoxicological data support the efficacy of this cleanup tool. Indeed, results showed that the bioremediation treatment resulted in a relevant reduction on soil toxicity to a plant (approximately 100% and 72% of control, respectively, for 10 × RD and 20 × RD contaminated soils). In addition, 5 days of P. ADP activity were enough to annul atrazine toxic effects toward microalgae and cladocerans in eluates obtained from the soil contaminated with 10 × RD of Atrazerba. For 20 × RD, an effective detoxification of eluates was achieved only after a longer bioremediation period of 10 days. The ecotoxicity tests proved not only the effective detoxification of bioremediated soils in 10 days but also the potential ability to concurrently reduce atrazine contamination of water compartments due to leaching and/or run-off events, to levels that may no longer be hazardous to ecosystems. Due to the worldwide continued use of atrazine/triazine-based herbicidal formulations, further studies viewing the optimization of this cost-effective cleanup tool at larger scales (mesocosm and real field scenarios) and testing of other commercial formulations containing mixtures of atrazine/triazine and other active ingredient are still needed so that bioremediation can be used as a valuable tool to reduce herbicide toxicity in contaminated land.

Effect of Organic Amendments on Degradation of Atrazine

Pesticide contamination of soil and ground water at or near the agricultural fields is a major problem world wide. The ability of several amendments like rice straw, manure, saw dust and charcoal were used to stimulate the degradation of atrazine in soil. Field soil fortified with pesticide at two concentration levels were amended separately with rice straw, farm yard manure, saw dust and charcoal at rates of 2.5% (w/w) and maintained at field capacity moisture regime and kept at ambient temperature 25 +/- 5 degrees C. The results indicate 89.5% degradation of atrazine in farm yard manure during 60-day period followed by rice straw, saw dust charcoal and recording 87.2% and 83.8%, 67.7%, respectively, as compared to unamended treatment where 63.3% degradation was observed. The FYM was found to be most effective in soil and enhances the degradation as compared to the other amendments. Although addition of organic manures has been an integral part of sustainable agriculture practices; the present findings give a new dimension of it's utilization for removal of persistent pesticides.

Crop‐Residue‐Derived Char Influences Sorption, Desorption and Bioavailability of Atrazine in Soils

The bioavailability of pesticides in soils is affected by the addition of crop‐residue‐derived char, which alters the sorption and desorption characteristics of the soils. Sorption, desorption, and biodegradation experiments were performed using atrazine [6‐chloro‐N‐ethyl‐N′‐(1‐methylethyl)‐1,3,5‐triazine‐2,4‐diamine] as the target compound in two soils (Hartsells and Grady) with and without a wheat (Triticum aestivum L.) char, and the char alone. The sorption isotherms for both soils were highly linear, whereas the isotherms for 1% char‐amended soils showed an increased sorption capacity and isotherm nonlinearity. The amount of atrazine sorbed by the char alone was 800 to 3800 times greater than sorbed by the soils. Successive desorption experiments showed that char‐amended soils contained higher nondesorbable fractions of atrazine than soils without char amendment. Pseudomonas sp. strain ADP capable of rapidly mineralizing atrazine was used to evaluate atrazine bioavailability. The presence of char reduced 14CO2 production by 11 and 20% in the char‐amended soils and char, respectively. The two‐step successive desorption experiments appeared to be able to predict the bioavailabilty of atrazine in char‐amended soils. This study shows that the presence of char in soils significantly influences the sorption and desorption processes and, ultimately, the bioavailability of atrazine.

Influence of Glomus etunicatum/ Zea mays mycorrhiza on atrazine degradation, soil phosphatase and dehydrogenase activities, and soil microbial community structure

The effects of an arbuscular mycorrhizal (AM) fungus ( Glomus etunicatum) on atrazine dissipation, soil phosphatase and dehydrogenase activities and soil microbial community structure were investigated. A compartmented side-arm (‘cross-pot’) system was used for plant cultivation. Maize was cultivated in the main root compartment and atrazine-contaminated soil was added to the side-arms and between them 650 or 37 μm nylon mesh was inserted which allowed mycorrhizal roots or extraradical mycelium to access atrazine in soil in the side-arms. Mycorrhizal roots and extraradical mycelium increased the degradation of atrazine in soil and modified the soil enzyme activities and total soil phospholipid fatty acids (PLFAs). Atrazine declined more and there was greater stimulation of phosphatase and dehydrogenase activities and total PLFAs in soil in the extraradical mycelium compartment than in the mycorrhizal root compartment when the atrazine addition rate to soil was 5.0 mg kg −1. Mycelium had a more important influence than mycorrhizal roots on atrazine degradation. However, when the atrazine addition rate was 50.0 mg kg −1, atrazine declined more in the mycorrhizal root compartment than in the extraradical mycelium compartment, perhaps due to inhibition of bacterial activity and higher toxicity to AM mycelium by atrazine at higher concentration. Soil PLFA profiles indicated that the AM fungus exerted a pronounced effect on soil microbial community structure.

Transport of Atrazine in Residue-Amended Soils

In this study, our aim was to quantify the transport of atrazine in soil columns where sugarcane (Saccharum spp. hyb.) residue was incorporated. The residue is a result of sugarcane combine harvest technology where massive amount of residue is deposited on the soil surface after each harvest. Miscible displacement experiments were carried out to quantify the mobility of atrazine in soil columns where sugarcane residue was mixed a Commerce soil. The residue was either incorporated uniformly with the soil or applied as a thin mulch layer over surface soil. The incorporation of residue with the soil resulted in retarded atrazine mobility because of strong sorption and slow release of the breakthrough curves (BTCs) during leaching. Moreover, early arrival of atrazine in the column effluent was observed from BTC results where the residue was uniformly incorporated with the soil, which is possibly due to physical nonequilibrium conditions, that is, preferential flow or macropore flow. An equilibrium-type model was incapable of describing atrazine BTCs from all columns regardless of whether the residue was placed as a surface layer or incorporated in the soil. In contrast, good overall description of measured BTC results was realized when a fully kinetic model was used. Therefore, our hypothesis that kinetic rather than equilibrium-type reactions are the dominant mechanisms for the release of adsorbed atrazine from the residue is supported.

Short-Term Accumulation of Atrazine by Three Plants from a Wetland Model System

This work describes the accumulation and distribution of the herbicide atrazine in soil, water, and roots from three wetland model systems using the monocots Typha domingensis, Sagittaria lancifolia, and Echinochloa pyramidalis. Results were analyzed from a 3(3) full factorial experimental design, in order to describe the effect of accumulation of atrazine and times of exposure in the species evaluated. We found that accumulation depends on the species and the herbicide concentration; about 30% was accumulated in soil, 40% in roots, and 10-20% in water. By the end of the experiment, E. pyramidalis accumulated 8.47 mg/l of atrazine and 14.39 mg/l T. domingensis; in all cases, adsorption accounted for 1.4%, fitting a Langmuir model with a k(d) of 14.47.

Bioaccessibility of Environmentally Aged 14C-Atrazine Residues in an Agriculturally Used Soil and Its Particle-Size Aggregates

After 22 years of aging under natural conditions in an outdoor lysimeter the bioaccessibility of 14C-labeled atrazine soil residues to bacteria was tested. Entire soil samples as well as sand-sized, silt-sized, and clay-sized aggregates (>20, 20-2, and <2microm aggregate size, respectively) were investigated under slurried conditions. The mineralization of residual radioactivity in the outdoor lysimeter soil reached up to 4.5% of the total 14C-activity after 16 days, inoculated with Pseudomonas sp. strain ADP. The control samples without inoculated bacteria showed a mineralization maximum of only about 1% after 44 days of incubation. Mineralization increased in the clay-sized aggregates up to 6.2% of the total residual 14C-activity within 23 days. With decreasing soil aggregate sizes, residual 14C-activity increased per unit of weight, but only minor differences of the mineralization in the soil and soil size aggregates using mineral-media for incubation was observed. Using additional Na-citrate in the incubation, the extent of mineralization increased to 6.7% in soil after 23 days following incubation with Pseudomonas sp. strain ADP. These results show that long-term aged 14C-atrazine residues are still partly accessible to the atrazine degrading microorganism Pseudomonas sp. strain ADP.

Coriolus hirsutus laccase effect on atrazine adsorption and desorption by different types of soil

Study of adsorption-desorption behavior of herbicide atrazine in soils of different geographical zones in the presence of Coriolus hirsutus laccase was performed. Laccase was shown to significantly increase adsorption coefficient and to facilitate irreversible adsorption of atrazine to soil. Supposably, laccase catalyzes oxidative binding of atrazine to soil. DOI: 10.1134/S0003683808040121

Macro-porosity and leaching of atrazine in tilled and orchard loamy soils

Atrazine is the most commonly detected herbicide in the groundwater. Leaching of atrazine largely depends on soil management practices. The aim of this study was to examine leaching of atrazine in tilled and orchard silty loam soils. The experimental objects included: conventionally tilled field (CT) with main tillage operations including pre-plow (10 cm) + harrowing, mouldboard ploughing (20 cm), and a 35 year-old apple orchard (OR) with a permanent sward. To determine leaching of atrazine soil columns of undisturbed structure were taken with steel cylinders of 21.5 cm diameter and 20 cm high from the depth of 0–20 cm. All columns were equilibrated at water content corresponding to field capacity (0.21 kg kg −1). Atrazine suspended in distilled water was dripped uniformly onto the surface of each column. Then water was infiltrated and breakthrough times of leachates were recorded. Atrazine concentration in the leachates was determined by means of HPLC Waters. Macro-porosity and percolation rate were higher in OR than CT soil. Cumulative recovery % of the atrazine applied was 1.267% for OR and approximately one third more from the CT soil but the rate of leaching (per unit of time) was greater from the OR soil. The lower leaching under OR than CT can be due to a greater SOM and the presence of earthworm burrows with organic burrow linings that could adsorb atrazine and contribute to preferential flow allowing solutes to bypass parts whereas the greater rate of leaching due to a greater infiltration rate.The results indicate potential of management practices for minimizing atrazine leaching.

Rapid Assay for Detecting Enhanced Atrazine Degradation in Soil

Atrazine is widely used to control broadleaf weeds and grasses in corn, sorghum, and sugarcane. Field persistence data published before 1995 showed that the average half-life of atrazine in soil was 66 d, and farmers expect to achieve weed control with a single application for the full season. However, reports of enhanced atrazine degradation in soil from fields that have a history of atrazine applications are increasing. A rapid laboratory assay was developed to screen soils for enhanced atrazine degradation. Soil (50 g) was placed in a 250 ml glass jar and treated with 7.5 ml of water containing atrazine (5 µg ai ml−1) and capped with a Teflon-lined lid. The assay was conducted at room temperature (25 C). Soil subsamples (1.5 to 3 g) were removed at 0, 1, 2, 4, 8, and 16 d after treatment and extracted with an equal weight of water (wt/vol). The atrazine in the water extract was assayed with high-pressure liquid chromatography (HPLC). The half-life of atrazine in soils with a history of use was ≤ 1.5 d, whereas the half-life in soils with no history of atrazine use was &gt; 8 d. The advantages of this assay are (1) the ease of set up; (2) the rapidity of extraction, and (3) the simplicity of the quantification of the atrazine.

Biodegradation of herbicide (atrazine) in contaminated soil using various bioprocessed materials

The concept of biostimulation i.e. enhancing the intrinsic degradation potential of a polluted matrix via the addition of amendments, nutrients, or other limiting factors has been used for a wide variety of xenobiotics. The objective of this research work was to study the degradation of atrazine (25 ppm) in soil amended with biogas slurry, mushroom spent compost, farmyard manure and sodium citrate as one of the chemical amendment. In the lab scale experiments carried out up to 21 days, atrazine in soil was extracted by column method and analyzed by HPLC. The atrazine dissipation was observed to be highest (34%) with biogas slurry. The study on synergistic effect of sodium citrate with farmyard manure showed a negative effect in initial phase, but dissipation gradually increased after 1st week (i.e. 32% degradation after 21 days). Although addition of organic manures has been an integral part of sustainable agriculture practices; the present findings give a new dimension of it’s utilization for removal of persistent pesticides.

Mineralization of atrazine in agricultural soil: Inhibition by nitrogen

Microbial mineralization of atrazine was characterized in soils and liquid media in the presence of nitrogen fertilizer concentrations representing typical field applications. The mineralization of atrazine in soils varied between 6 and 99% after 18 d of incubation. Half-lives of between 0.99 and more than 18 d were obtained. Mineralization kinetics and degree are related by a reciprocal trend to concentrations of available nitrogen in the soil. In liquid media, half-lives were calculated as 0.12 d in the absence of fertilizer nitrogen and as 79 d in the presence of 1,000 mg/L of KNO3-N. Only 20% of atrazine was mineralized after 18 d of incubation in the presence of this concentration of KNO3-N, whereas greater than 90% mineralization occurred after 2 d of incubation in liquid medium without KNO3-N. The results demonstrate that the mineralization of atrazine is inhibited even at fertilizer nitrogen levels lower than typical field applications. Inhibition in soil is lower than that in liquid medium, possibly because of the higher complexity of the soil system. This may explain why atrazine that infiltrates to the groundwater is persistent. The microbial consortium of the soils was characterized, and seven species were identified. The degrading capacity of these species suggests that only three species are involved in the degradation of atrazine.

Atrazine degradation and transport in runoff on a Black Vertosol

In Australia communities are concerned about atrazine being detected in drinking water supplies. It is important to understand mechanisms by which atrazine is transported from paddocks to waterways if we are to reduce movement of agricultural chemicals from the site of application. Two paddocks cropped with grain sorghum on a Black Vertosol were monitored for atrazine, potassium chloride (KCl) extractable atrazine, desethylatrazine (DEA), and desisopropylatrazine (DIA) at 4 soil depths (0–0.05, 0.05–0.10, 0.10–0.20, and 0.20–0.30 m) and in runoff water and runoff sediment. Atrazine + DEA + DIA (total atrazine) had a half-life in soil of 16–20 days, more rapid dissipation than in many earlier reports. Atrazine extracted in dilute potassium chloride, considered available for weed control, was initially 34% of the total and had a half-life of 15–20 days until day 30, after which it dissipated rapidly with a half life of 6 days. We conclude that, in this region, atrazine may not pose a risk for groundwater contamination, as only 0.5% of applied atrazine moved deeper than 0.20 m into the soil, where it dissipated rapidly. In runoff (including suspended sediment) atrazine concentrations were greatest during the first runoff event (57 days after application) (85 µg/L) and declined with time. After 160 days, the total atrazine lost in runoff was 0.4% of the initial application. The total atrazine concentration in runoff was strongly related to the total concentration in soil, as expected. Even after 98% of the KCl-extractable atrazine had dissipated (and no longer provided weed control), runoff concentrations still exceeded the human health guideline value of 40 µg/L. For total atrazine in soil (0–0.05 m), the range for coefficient of soil sorption (Kd) was 1.9–28.4 mL/g and for soil organic carbon sorption (KOC) was 100–2184 mL/g, increasing with time of contact with the soil and rapid dissipation of the more soluble, available phase. Partition coefficients in runoff for total atrazine were initially 3, increasing to 32 and 51 with time, values for DEA being half these. To minimise atrazine losses, cultural practices that maximise rain infiltration, and thereby minimise runoff, and minimise concentrations in the soil surface should be adopted.

Development and application of immunoaffinity column chromatography for atrazine in complex sample media

A rabbit antibody immunoaffinity (IA) column procedure was evaluated as a cleanup method for the determination of atrazine in soil, sediment, and food. Four IA columns were prepared by immobilizing a polyclonal rabbit anti-atrazine antibody solution to HiTrap Sepharose columns. Atrazine was bound to the IA columns when the loading solvents were either 100% water, 2% acetonitrile in water, or 10% methanol in phosphate buffered saline (PBS). Quantitative removal of atrazine from the IA columns was achieved with elution solvents of either 70% ethanol in water, 70% methanol in water, or 100% methanol. One control column was prepared using nonspecific rabbit IgG antibody. This control column did not retain any applied atrazine indicating atrazine did not bind indiscriminately to protein or the Sepharose support. The four IA columns showed reproducible coupling efficiency for the immobilization of the atrazine antibody and consistent binding and releasing of atrazine. The coupling efficiency (4.25 mg of antibody in 1 mL of resin bed) for the four IA columns ranged from 93 to 97% with an average of 96 ± 2% (2.1%). Recoveries of the 500, 50, and 5 ng mL −1 atrazine standard solutions from the four IA columns were 107 ± 7% (6.5%), 122 ± 14% (12%), and 114 ± 9% (8.0%) respectively, based on enzyme-linked immunosorbent assay (ELISA) data. The maximum loading was approximately 700 ng of atrazine for each IA column (∼0.16 μg of atrazine per mg of antibody). The IA columns could withstand 100% methanol as the elution solvent and could be reused more than 50 times with no change in performance. The IA columns were challenged with soil, sediment, and duplicate-diet food samples and effectively removed interferences from these various matrices for subsequent gas chromatography/mass spectrometry (GC/MS) or ELISA analysis. The log-transformed ELISA and GC/MS data were significantly correlated for soil, sediment and food samples although the ELISA values were slightly higher than those obtained by GC/MS. The IA column cleanup procedure coupled with ELISA analysis could be used as an alternative effective analytical method for the determination of atrazine in complex sample media such as soil, sediment, and food samples.

Ultra trace adsorptive stripping voltammetric determination of atrazine in soil and water using mercury film electrode

In situ mercury film electrode produced in the presence of thiocyanate has been shown extremely useful for highly sensitive adsorptive stripping voltammetric measurements of atrazine down to sub-μg L −1 level. Operational parameters have been optimized and the stripping voltammetric performance has been investigated using square wave scans. The adsorptive stripping response is linear over the range of 0.5–60 μg L −1 atrazine, with a detection limit of 0.024 μg L −1. The method has been applied to the determination of atrazine in soil and water samples.

Enhancing cell survival of atrazine degrading Rhodococcus erythropolis NI86/21 cells encapsulated in alginate beads

To develop a method to produce beads with encapsulated Rhodococcus erythropolis NI86/21 with high cell density, extended shelf life, ease of handling and good atrazine degradation capabilities in both liquid and in agricultural soil. Our findings show that the supplementary recovery step in nutrient broth media shortly after cell encapsulation facilitates cell survival in both wet and dry beads upon extended storage at 4 degrees C. Air drying has little or no impact on encapsulated R. erythropolis cell's ability to degrade atrazine in liquid or soil. Bead storage for periods extending up to 12 months at 4 degrees C did not affect the capacity of R. erythropolis encapsulated cells to degrade atrazine in either BMN or nonsterile soil extracts. Bentonite-amended beads formulated with 1% skim milk and exposed to the supplementary growth step, outperformed all other bead formats. These beads provided adequate numbers of vigorous R. erythropolis cells in either liquid or soil media to degrade atrazine. Supplementary growth in nutrient broth media immediately following cell encapsulation greatly enhances R. erythropolis cells survival in both wet and dry beads upon extended storage at 4 degrees C. Wet and dried beads have similar capacity for atrazine degradation, and their usefulness and appeal in agronomic practise will only be known after bioassay evaluation and successful demonstration at field scale using incurred residues. R. erythropolis NI86/21 encapsulated cells have the potential to reduce residual atrazine in soil, thereby minimizing the likelihood of off-site transport to ground or river water and reduce the loss of crops because of phytotoxicity of residual herbicide. Owing to their ease of handling, storage and possible compatibilities with pre-existing mechanical equipment, dried bead formats are ideally suited for agricultural and remediational applications.