Atrazine Residues Research Articles

Evaluation of the rotating disk sorptive extraction technique with polymeric sorbent for multiresidue determination of pesticides in water by ultra-high-performance liquid chromatography–tandem mass spectrometry

The use of pesticides has been associated with the increase of productivity of crops and control of vectors that cause diseases. However, excessive use of these compounds can cause human health and environmental problems, especially regarding to water resources. In this work, a method for multiresidue determination of 62 pesticides in surface water using the rotating disk sorptive extraction (RDSE) technique for sample preparation and ultra-high-performance liquid chromatography with tandem mass spectrometry (UHPLC–MS/MS) for analysis was optimized and validated. The parameters time and rotational disk velocity for the extraction step, types and amounts of sorbents, sample pH, ionic strength, time and velocity of the rotating disk in the desorption step, as well different desorption solvents were evaluated. The best results were obtained using 50mL of sample, acidified at pH 2.0, and 2.5g of sodium chloride. The selected velocity of rotation in the extraction step was 1600rpm for 80min. Inside the disk cavity, a small amount (20mg) of the polymeric sorbent Oasis® HLB was used. The desorption step was performed immerging the disk in 3mL of methanol and rotating the disk at 1600rpm for 60min. Procedural calibration curves showed linearity between 0.05 or 0.1–2μgL−1, with r2>0.99 for all compounds. The method presented practical limit of quantification of 0.05 or 0.1μgL−1 and suitable accuracy and precision, with recoveries from 70.1 to 119.9% and RSD≤20% for the levels 0.05, 0.1, 0.5 and 2μgL−1. The validated method was applied to surface water samples from different river and residues of atrazine, azoxystrobin, clomazone, difenoconazole, epoxiconazole, propoxur, simazine and tebuconazole were found in the range of 0.06–0.35μgL−1. The results indicate that the proposed method is suitable for the determination of pesticide residues in surface water, allowing an easy and simultaneously preparation of several samples with low material consumption.

Weed management in turmeric

Pre-emergence metribuzin 0.7 kg/ha, pendimethalin 1.0 kg/ha and atrazine 0.75 kg/ha each followed by i) hand weeding (HW) (45 and 75 DAP, days after planting), ii) fenoxaprop 67 g/ha + metsulfuron-methyl 4 g/ha (45 DAP) and iii) mulch + HW (75 DAP); pre-emergence oxyflourfen 0.3 kg/ha and oxadiargyl 0.25 kg/ha and post-emergence glyphosate 1.23 and 1.85 kg/ha (25 DAP) each followed by HW (45 and 75 DAP); HW (25, 45 and 75 DAP) and untreated control were evaluated at Palampur during 2014, 2015 and 2016 to develop an effective weed management strategy in turmeric for mid hill conditions of Himachal Pradesh. Treatments constituting fenoxaprop + metsulfuron-methyl were phyto-toxic resulting in poor turmeric crop canopy formation thereby more growth of Ageratum sp. and lower plant height, plant stand, daughter corms/mother corm, rhizome yield and economics. Other weed control treatments were effective in controlling Echinochloa colona and other grassy weeds. With every g/m2 increase in weed dry weight, the fresh turmeric rhizome yield was reduced by 64.2 kg/ha. Pre-emergence atrazine/metribuzin/pendimethalin fb mulch fb hand weeding had effectively controlled weeds and increased the fresh rhizome yield by 54.1 to 54.9%, cured rhizome yield by 57.6 to 59.4% and net return by 66.4 to 68.3% being comparable to hand weeding thrice. However, hand weeding thrice was the costliest treatment. Atrazine/metribuzin/pendimethalin fb mulch fb hand weeding had lower weed persistence index and weed index and higher weed management index, agronomic management index, integrated weed management index and overall impact index than other treatments. Residues of metribuzin, atrazine, pendimethalin, oxyfluorfen and metsulfuron--methyl in soil and rhizomes of turmeric were found below detectable level. Based on overall impact index metribuzin fb mulch fb hand weeding, atrazine fb mulch fb hand weeding and pendimethalin fb mulch fb hand weeding in that order are recommended as an alternative to hand weeding thrice in turmeric.

A Simple and Fast Solid-Phase Extraction GC-ECD Method for the Routine Assessment of Atrazine Residues in Agricultural Produces

A simple and rapid solid-phase extraction (SPE) supported Gas Chromatographic-Electron Capture Detection (GC-ECD) method has been presented for the routine determination of atrazine in some common agricultural produces. Equivalent to USP G-42 GC stationary phase, DB-35 ms capillary column and ECD detector was selected on the basis of physical and structural characteristics of atrazine. Temperature programming of 20 minutes with 0.8 mL/min optimized gas flow gave maximum number of the theoretical plates (N=104) and high resolution (Rs~2.1 min) with LOD and LOQ values of 0.001 μg/L and 0.1 μg/L respectively. LOQ achieved by the present method is almost below the maximum residue levels recommended by the European legislation. Satisfactory spiked recoveries of the atrazine were obtained from agricultural produces ranging from 82.2 to 97.8% with relative standard deviations below 3.8%. The minimum consumption of solvent (5 mL ethyl acetate) in SPE for residual workup in 5 minutes, with subsequent 20 minutes GC analysis makes the proposed method simple and fast having promise as an excellent economical alternative for the routine analysis of atrazine in environmental samples.

Distribution of atrazine and its phytoremediation by submerged macrophytes in lake sediments

We investigated sediments with high atrazine accumulation capability from 6 eutrophic lakes in Hubei Province of central China. Almost all lakes have atrazine in their sediments because of human activities. Honghu Lake and Liangzihu Lake were found to have higher levels of atrazine in sediment: 0.171 and 0.114 mg kg−1, respectively. The results showed that lake sediments could adsorb atrazine six times faster than soils. The equilibrium partition coefficient of atrazine desorption (KPd) is much larger than the adsorption equilibrium partition coefficient (KPa) of atrazine, indicating that the residue of atrazine in water is easily immobilized by the sediments. Meanwhile, the incubation experiment showed that the removal rateof atrazine in Potamogeton crispus-planted and Myriophyllum spicatum-planted sediments reached >90%, while the rate in unplanted sediments was 77.2 ± 2.12% over 45 d. In unplanted sediment, the half-life of atrazine dissipation was 14.30 d, which was strongly enhanced by P. crispus and M. spicatum, greatly reducing the half-life to 8.60 and 9.72 d, respectively. These two submerged macrophytes are considered to be potential tools in the remediation of atrazine-contaminated sediments.

Enhanced detoxification and degradation of herbicide atrazine by a group of O-methyltransferases in rice

Atrazine (ATR) as a toxic herbicide has become one of the seriously environmental contaminants worldwide due to its long-term intensive use in crop production. This study identified novel methyltransferases (MTs) involved in detoxification and degradation of ATR residues in rice plants. From a subset of MTs differentially expressed in ATR-exposed rice, forty-four O-methyltransferase genes were investigated. Total activities were significantly enhanced by ATR in rice tissues. To prove detoxifying capacity of the MTs in rice plants, two rice O-MTs (LOC_Os04g09604 and LOC_Os11g15040) were selected and transformed into yeast cells (Pichia pastoris X-33). The positive transformants accumulated less ATR and showed less toxicity. Using UPLC-TOF-MS/MS, ATR-degraded products in rice and yeast cells were characterized. A novel O-methylated-modified metabolite (atraton) and six other ATR-derivatives were detected. The topological interaction between LOC_Os04g09604 enzyme and its substrate was specially analyzed by homology modeling programs, which was well confirmed by the molecular docking analysis. The significance of the study is to provide a better understanding of mechanisms for the specific detoxification and degradation of ATR residues in rice growing in environmentally relevant ATR-contaminated soils and may hold a potential engineering perspective for generating ATR-resistant rice that helps to minimize ATR residues in crops.

Sorption and Leaching Potential of Isoproturon and Atrazine in Low Organic Carbon Soil of Pakistan Under a Wheat-Maize Rotation

Pesticide leaching is a great threat in low organic carbon soils when subjected to improper irrigation scheduling. Limited data are available on the sorption and leaching potential of pesticides in agricultural soils of Pakistan with low soil organic carbon (SOC). Lysimeter and field studies were conducted with and without manure application at two irrigation levels in a wheat-fallow-maize rotation in Faisalabad, Punjab, Pakistan. Isoproturon was applied to wheat 55 d after sowing at 1 kg active ingredient (a.i.) ha−1, while atrazine was sprayed on maize 30 d after sowing at 0.774 kg a.i. ha−1. Soil was sampled from three depths (0–35, 35–70, and 70–110 cm) for the field study and four depths (0–35, 35–70, 70–115, and 115–160 cm) for the lysimeter study, 280 and 65 d after application of isoproturon and atrazine, respectively. The soil-water partition coefficients (Kd) of isoproturon and atrazine ranged from 0.3 to 1.2 and 0.4 to 1.5 L kg−1, respectively, and increased linearly with increase in SOC contents. The organic carbon-normalized soil-water partition coefficient (Koc) of isoproturon and atrazine averaged 246.1 and 184.9 L kg−1, respectively, being higher with low spiking concentration. Isoproturon residues measured 280 d after application ranged from 2.1% to 3.6% of the applied mass in the lysimeter study and from 1.5% to 3.1% under field conditions. Atrazine residues 65 d after application ranged from only 0.62% to 0.78% and from 0.88% to 0.82% in the lysimeter and field studies, respectively. The lowest levels of residues for both pesticides were observed with frequent irrigation applied to manure-amended soil. A pesticide leaching risk screening tool, the ground water ubiquity score (GUS), indicated that in the absence of manure under both irrigation levels, isoproturon has a leaching potential (GUS = 2.8), while with the application of manure it has a very low leaching risk. Atrazine GUS ranged from 1.7 to 1.9, indicating a very low risk of leaching.

Rapid estimation of readily leachable triazine residues in soils using automatic kinetic bioaccessibility assays followed by on-line sorptive clean-up as a front-end to liquid chromatography

An automatic batchwise bioaccessibility test was proposed for on-line monitoring of readily mobile pools of ametryn and atrazine residues in agricultural soils with different physicochemical properties. A 0.01molL−1 CaCl2 solution mimicking rainwater percolation through the soil profiles was used for the herbicide extractions. The extract aliquots were successively sampled at regular time intervals in order to investigate the extraction kinetics. For extract clean-up and retention of freely dissolved target species, 30mg of restricted-access like copolymer were used as in-line sorptive material followed by elution with methanol and on-line heart-cut injection towards a C18 silica reversed-phase monolithic column (100×4.6mm) in a liquid chromatographic system. A mathematical model emphasized that the readily available pools vs time can be in most instances described by a first-order exponential equation, thus an asymptotical value is approached. Consequently, the leaching assays can be performed without attaining chemical equilibrium. Enhancement factors and detection limits were 10.2 and 18.8, and 0.40 and 0.37mgkg−1 for ametryn and atrazine, respectively. The automatic method features good repeatability for leaching tests (r.s.d.: 11.8−10.2% for sandy and 3.7–6.2% for clayey soil). Reliable data, demonstrated with relative recoveries in the soil leachates ranging from 86 to 104%, were achieved in less than 35min, thus avoiding the need for up to 24h as recommended by standard leaching methods.

Residual tembotrione and atrazine in carrot

ABSTRACTCarrot (Daucus carota L.) is a vegetable crop that is grown throughout the year across various regions of Brazil in rotation or in succession to other cultures. Herbicide residual effect has emerged as a concern, because of the possibility of carryover. Thus, the objective of this study was to evaluate the effect of tembotrione and atrazine residues – in mixture and isolated – on carrot planted in succession to corn. The experiment was designed in randomized blocks with five replications. Treatments consisted of tembotrione (50.4 g ha−1), tembotrione (100.8 g ha−1), tembotrione + atrazine (50.4 g ha−1+ 2 L ha−1), tembotrione + atrazine (100.8 g ha−1+ 2 L ha−1), and atrazine (2.00 L ha−1) applied eight months before carrot seeding, plus a control treatment with no herbicide application. Investigated variables were shoot dry mass, productivity, and classification of carrot roots. The presence of atrazine and tembotrione decreased dry mass in the area, and only tembotrione reduced total root productivity. Thus, there is a carryover effect to tembotrione application that reduces the dry matter accumulation of shoot and total productivity, and an atrazine + tembotrione (100.8 g ha−1) mixture reduces the total productivity after application of these herbicides to soil.

Bacterial community structure in atrazine treated reforested farmland in Wuying China

The Grain for Green (GFG) Project in China is currently the largest environmental rehabilitation project aimed at turning low-yielding farm land to forests and pastures. Such conversion of land use type also promotes remediation of the polluted environment. Soil microbes reflect soil function and are therefore considered an essential component of ecosystem restoration. To evaluate the environmental effects of converting atrazine polluted farmland to secondary forest, we determined soil chemical properties, soil bacterial communities and their responses to three types of land use (primary forest, PF; secondary forest, SF; farm land, FL) in Wuying, China. Our results showed that soil organic matter significantly decreases in the order PF>SF>FL. Bacterial 16S rRNA gene 454 pyrosequencing revealed that the soil bacterial diversity level remained unchanged. However between FL and the two forested sites, we observed an increase of Actinobacteria, β-proteobacteria and Firmicutes; and a decrease of Acidobacteria and Verrucomicrobia, while in SF the bacterial community structure was similar to PF. We conclude that reforestation permits bacterial community, resetting from FL back to a state that resembles natural conditions. In addition, 20 years of natural attenuation degraded soil atrazine residues in SF but traces remained in the soil. Reforestation generally resulted in favorable ecological impacts on soil quality and the bacterial community compared with active farm fields.

Quantifying Neonicotinoid Insecticide Residues Escaping during Maize Planting with Vacuum Planters.

Neonicotinoid residues escaping in vacuum-planter exhaust during maize planting were measured in 25 fields in southwestern Ontario in 2013-2014 using filter bags to collect planter exhaust dust and horizontal and vertical sticky traps to collect planter operation-generated dust. Atrazine residues were used to differentiate between neonicotinoid residues originating from seed or from disturbed soil. Recovery rates of seed-applied neonicotinoids in exhaust were 0.014 and 0.365% in 2013 and 2014, respectively, calculated on the basis of neonicotinoid concentrations in preplant soil and seed application rates. Neonicotinoid exhaust emission rates were 0.0036 and 0.1104 g/ha for 2013 and 2014, respectively, with 99.9472 and 99.7820% originating from treated seed in 2013 and 2014, respectively, calculated on the basis of the atrazine marker. Rates of recovery of seed-applied neonicotinoid residues by exhaust filter bags were 0.015 and 0.437% for 2013 and 2014, respectively. Neonicotinoid residues captured on horizontal and vertical traps were 1.10 ng/cm2 (0.1104 g/ha) and 1.45 ng/cm2 (0.0029 g/ha), respectively, with 92.31 and 93.03% originating from treated seed, respectively, representing 0.3896% of the original active ingredient applied to the seed planted. Exposure to pollinators can be best reduced by strategies to keep active ingredient on the seed, below the soil surface, and in the field where applied.

Effect of fly ash and bagasse charcoal on the mobility of atrazine in Indian sandy loam soil

AbstractThe study was undertaken to obtain an objective and realistic overview of atrazine residue reduction in sandy loam soil using two low-cost adsorbents. Fly ash and bagasse charcoal are waste products of thermal power plant and sugar mill, respectively, and are abundant, which have a disposal problem. A laboratory-based adsorption and leaching experiments were carried out to know the percentage reduction of atrazine by mixing these two abundant materials in soil at 1% level. In adsorption and leaching studies, atrazine 50% WP was used to know the reduction of atrazine concentration in fresh soil and soil with adsorbent. It was found that adsorbent mixed soil adsorbed atrazine greater than the fresh soil and the mobility of atrazine was reduced in adsorbent mixed soil as compared to fresh soil. It was concluded that the reduction of atrazine in adsorbent mixed soil was attributed due to the adsorption properties of these adsorbents as well as reducing the porosity of soil. Hence, these adsorbents wer...

Distribution of terbuthylazine and atrazine residues in crop-cultivated soil: The effect of herbicide application rate on herbicide persistence

Field experiments were carried out to compare the effect of herbicide application rate on the distribution and persistence of atrazine (ATR), terbuthylazine (TBA), and their dealkylated degradation products in two conventionally cultivated cornfield soils: a silt loam soil and a silty clay loam soil, both typical for the crop-producing area of continental Croatia. Herbicides were applied pre-emergence at the registered (R) (1.0–1.5kgha−1), double-registered (2R), and triple-registered (3R) rates. Topsoil (0–30cm) and subsoil (30–60cm) samples were collected periodically during a crop rotation cycle of 17months. Soil microcosm experiments were performed under controlled conditions to investigate the influence of the herbicide application rate on their biodegradation in herbicide-treated cornfield topsoils. The herbicide half-lives (DT50) calculated by using monophasic and biphasic first-order kinetics models were compared. The herbicide sorption intensity in the studied soils was evaluated in terms of the Freundlich sorption isotherm. Under field conditions, TBA was retained within the first 60cm of both agricultural soils at least twice as long as ATR. While ATR residues persisted in soil only until corn harvest (5months), the residues of TBA and its N-deethylated degradation product were still measurable at the end of the crop rotation cycle (17months). The persistence of both herbicides was higher in soil with higher herbicide sorption intensity. ATR and TBA application rates higher than registered generally did not significantly influence the herbicide biodegradation rates or dissipation from the topsoil layers. The enhanced application rate slightly decreased the TBA persistence only in soil exhibiting a rather slow biodegradation. A temperature-leaching potential index for ATR and TBA applied at R rate showed the same leachability class for both herbicides. The leachability class of TBA could be higher than that of ATR in soil with moderate TBA persistence (DT50=30–100days). From an environmental perspective, TBA could pose a similar risk for groundwaters as ATR.

Multi-Residue Analysis of Herbicides in Soil with an UPLC-ESI-MS Method

A rapid and sensitive method was developed for the determination of 51 herbicides in soil by ultra-performance liquid chromatography-electrospray ionization-mass spectrometry (UPLC–ESI–MS). Using acetonitrile effectively extracted 22 kinds of triazine and other basic herbicides, and using 90:10 v/v acetonitrile-phosphate buffer (pH = 7.5) effectively extracted another 29 herbicides. The extract has not cleaned up further. Chromatographic separation was achieved within 10 min using gradient elution with acetonitrile–water as a mobile phase for 22 triazine and phenylurea herbicides, and with 5 mM ammonium acetate containing 0.1% formic acid aqueous solution–acetonitrile as a mobile phase for another 29 herbicides. The response was linear over two orders of magnitude with correlation coefficients (r2) higher than 0.99. The limits of quantification for the herbicides varied from 0.2 to 20 µg kg−1. The intra- and inter-day precisions (relative standard deviation, RSD) were 2.2–9.3% and 5.7–17.1%, respectively. The average recovery varied from 61.6 to 112% with the RSD of 1.6–11.3%. Analyzing 51 soil samples from 17 counties formed the basis of this method. Three herbicide residues were found in four counties. Atrazine residue in soil for 17 counties was found; its content was 0.4–9.8 μg kg−1. Nicosulfuron residue in soil for two counties was found, with a high up to 133 or 1317 μg kg−1. Propazine (0.3 and 1.34 μg kg−1), atratone (2.14 and 3.93 μg kg−1), and cynanazine (0.34 μg kg−1) in soils for some counties were also found. The validated method can ensure the rapid multi-class, multi-residue analysis at low μg kg−1 level for 47 herbicides in soil. The developed method provides an effective analytical basis for controlling herbicide dosage, investigating their distribution and degradation, and evaluating their hazards on the environment and human health.

Assessment of Lindane and Atrazine Residues in Maize Produced in Ghana Using Gas Chromatography-Electron Capture Detector (GC-ECD) and Gas Chromatography-Mass Spectrometry (GC-MS)

Maize is consumed by over 95% of the Ghanaian populace and the practice of using Atrazine and Lindane (an Organochlorine) pesticides in its production has raised concerns about potential adverse effects on human health and the environment. A field survey was conducted in this study to assess farmers’ knowledge of safe handling and use of these chemicals as well as toxicity awareness and symptoms among farmers and traders. Residues of these pesticides in maize samples as well as the potential health risk associated with exposure to them were also evaluated. Composite maize samples were collected for nine of ten regions in Ghana and analyzed. Data obtained from the field survey indicate that a large proportion of farmers are at risk of pesticide poisoning through occupational exposure. Over 80% of applicators do not apply safety precautions during pesticide mixing and application; resulting in considerable prevalence of pesticide related illnesses in the study area. Residues of Lindane and atrazine were below detection limits of 0.005 mg/kg and 0.010 mg/kg respectively; except in the Ashanti region where atrazine was 0.05 mg/kg which was within the EU-MRL of 0.1 mg/kg. However, minute concentrations of other Organochlorines (endrin—0.007 mg/kg; heptachlor—0.023 mg/kg; alpha-endosulfan—0.013 mg/kg) were found in maize samples from Brong Ahafo, eastern, central and upper west regions. Though endrin and alpha-endosulfan were below the EU-MRL of 0.01 mg/kg and 0.10 mg/kg respectively, heptachlor was slightly above the EU-MRL of 0.01 mg/kg. The estimated dose for all these pesticides however does not pose direct hazard to human health although present in the maize samples since the values were lower than toxic thresholds and reference doses. However, due to the unsafe application practices by applicators, there exists a potential risk for systemic and carcinogenic health effects by these chemicals in the study area.

Hollow fiber-liquid phase microextraction for trace enrichment of the residues of atrazine and its major degradation products from environmental water and human urine samples

Miniaturized HF-LPME for trace enrichment of atrazine and its degradation products from environmental waters and human urine samples.

Evaluation of the agronomic performance of atrazine-tolerant transgenic japonica rice parental lines for utilization in hybrid seed production.

Currently, the purity of hybrid seed is a crucial limiting factor when developing hybrid japonica rice (Oryza sativa L.). To chemically control hybrid seed purity, we transferred an improved atrazine chlorohydrolase gene (atzA) from Pseudomonas ADP into hybrid japonica parental lines (two maintainers, one restorer), and Nipponbare, by using Agrobacterium-mediated transformation. We subsequently selected several transgenic lines from each genotype by using PCR, RT-PCR, and germination analysis. In the presence of the investigated atrazine concentrations, particularly 150 µM atrazine, almost all of the transgenic lines produced significantly larger seedlings, with similar or higher germination percentages, than did the respective controls. Although the seedlings of transgenic lines were taller and gained more root biomass compared to the respective control plants, their growth was nevertheless inhibited by atrazine treatment compared to that without treatment. When grown in soil containing 2 mg/kg or 5 mg/kg atrazine, the transgenic lines were taller, and had higher total chlorophyll contents than did the respective controls; moreover, three of the strongest transgenic lines completely recovered after 45 days of growth. After treatment with 2 mg/kg or 5 mg/kg of atrazine, the atrazine residue remaining in the soil was 2.9–7.0% or 0.8–8.7% respectively, for transgenic lines, and 44.0–59.2% or 28.1–30.8%, respectively, for control plants. Spraying plants at the vegetative growth stage with 0.15% atrazine effectively killed control plants, but not transgenic lines. Our results indicate that transgenic atzA rice plants show tolerance to atrazine, and may be used as parental lines in future hybrid seed production.

Chemical Modification and Degradation of Atrazine in Medicago sativa through Multiple Pathways

Atrazine is a member of the triazine herbicide family intensively used to control weeds for crop production. In this study, atrazine residues and its degraded products in alfalfa (Medicago sativa) were characterized using UPLC-TOF-MS/MS. Most of atrazine absorbed in plants was found as chemically modified derivatives like deisopropylated atrazine (DIA), dehydrogenated atrazine (DHA), or methylated atrazine (MEA), and some atrazine derivatives were conjugated through different functional groups such as sugar, glutathione, and amino acids. Interestingly, the specific conjugates DHA+hGSH (homoglutathione) and MEA-HCl+hGSH in alfalfa were detected. These results suggest that atrazine in alfalfa can be degraded through different pathways. The increased activities of glycosyltransferase and glutathione S-transferase were determined to support the atrazine degradation models. The outcome of the work uncovered the detailed mechanism for the residual atrazine accumulation and degradation in alfalfa and will help to evaluate whether the crop is suitable to be cultivated in the atrazine-polluted soil.

Soil microbial community toxic response to atrazine and its residues under atrazine and lead contamination.

Intensive use of atrazine and extensive dispersal of lead (Pb) have occurred in farmland with chemical agriculture development. However, the toxicological effect of their presence on soil microorganism remains unknown. The objective of this study was to investigate the impacts of atrazine or Pb on the soil microbiota, soil net nitrogen mineralization, and atrazine residues over a 28-day microcosm incubation. The Shannon-Wiener diversity index, typical microbe species, and a Neighbor-joining tree of typical species from sequencing denaturing gradient gel electrophoresis (DGGE) bands were determined across periodical sampling times. The results showed that the existence of atrazine or Pb (especially high concentration) in soils reduced microbial diversity (the lowest H value is 2.23) compared to the control (H = 2.59) after a 28-day incubation. The species richness reduced little (from 17~19 species to 16~17 species) over the research time. But soil microbial community was significantly affected by the incubation time after the exposure to atrazine or Pb. The combination of atrazine and Pb had a significant inhibition effect on soil net nitrogen nitrification. Atrazine and Pb significantly stimulated soil cumulative net nitrogen mineralization and nitrification. Pb (300 and 600 mg kg(-1)) accelerated the level of atrazine dissipation. The exposure might stimulate the significant growth of the autochthonous soil degraders which may use atrazine as C source and accelerate the dissipation of atrazine in soils.

Oxidative stress response induced by atrazine in Palaemonetes argentinus: The protective effect of vitamin E

The widespread contamination and persistence of the herbicide atrazine residues in the environment resulted in the exposure of non-target organisms.The present study was undertaken to investigate the effect of atrazine in the response of oxidative stress biomarkers in the freshwater shrimp Palaemonetes argentinus and the protective effect of vitamin-E against atrazine-induced toxicity. Therefore, two batches of P. argentinus were fed for 21 days with a commercial food enriched in proteins (D1) or with D2, composed of D1 enriched with vitamin-E (6.8 and 16.0mg% of vitamin-E, respectively). Subsequently, half of the individuals of each group were exposed to atrazine (0.4mgL−1) for 24h and the others remained as controls.Atrazine promoted oxidative stress response in P. argentinus fed with D1 as indicated by enhanced H2O2 content and induction of superoxide dismutase, glutathione-S-transferases and glutathione reductase. This antioxidant activity would prevent the increment of thiobarbituric acid reactive substances in the shrimp tissues. P. argentinus fed with D2 reversed the response of the biomarkers measured. However, the activation of antioxidants response had an energetic cost, which was revealed by a decrease in lipids storage in shrimps.These results show the modulatory effect of vit-E on oxidative stress and its potential use as an effective antioxidant to be applied in chemoprotection strategies during aquaculture.

Atrazine soil core residue analysis from an agricultural field 21 years after its ban.

Atrazine (2-chloro-4-ethylamino-6-isopropylamino-1,3,5-triazine) groundwater monitoring in the Zwischenscholle aquifer in western Germany revealed concentrations exceeding the threshold value of 0.1 μg L and increasing concentration trends even 20 yr after its ban. Accordingly, the hypothesis was raised that a continued release of bound atrazine residues from the soil into the Zwischenscholle aquifer in combination with the low atrazine degradation in groundwater contributes to elevated atrazine in groundwater. Three soil cores reaching down to the groundwater table were taken from an agricultural field where atrazine had been applied before its ban in 1991. Atrazine residues were extracted from eight soil layers down to 300 cm using accelerated solvent extraction and analyzed using liquid chromatography-tandem mass spectrometry. Extracted atrazine concentrations ranged between 0.2 and 0.01 μg kg for topsoil and subsoil, respectively. The extracted mass from the soil profiles represented 0.07% of the applied mass, with 0.01% remaining in the top layer. A complete and instantaneous remobilization of atrazine residues and vertical mixing with the groundwater body below would lead to atrazine groundwater concentrations of 0.068 μg L. Considering the area where atrazine was applied in the region and assuming instantaneous lateral mixing in the Zwischenscholle aquifer would result in a mean groundwater concentration of 0.002 μg L. A conservative estimation suggests an atrazine half-life value of about 2 yr for the soil zone, which significantly exceeds highest atrazine half-lives found in the literature (433 d for subsurface soils). The long-term environmental behavior of atrazine and its metabolites thus needs to be reconsidered.