Pesticide Bioavailability Research Articles

PH-responsive poly(acrylic acid) coated mesoporous silica nanoparticles for controlled abamectin release: Synthesis, characterization, and agricultural application

BackgroundSmart pesticides, capable of responding to environmental stimuli, hold promise for achieving precise and on-demand release of pesticides, thereby reducing environmental risks and optimizing pesticide utilization. MethodsHerein, we prepared a novel composite nanoparticle with a core-shell structure of poly(acrylic acid)-coated mesoporous silica by distillation precipitation polymerization method, which is simple and efficient. Then, abamectin was successfully loaded by impregnation adsorption, and a novel pH-responsive controlled-release pesticide formulation, Abamectin-MSN@PAA, was prepared. SignificantFindings In this work, Abamectin-MSN@PAA exhibited a loading content of 23.79 % and an average particle size of approximately 272.1 nm. Notably, the formulation demonstrated acid-responsive release kinetics, with cumulative release percentages of 85.91 %, 69.03 %, and 53.44 % observed at pH values of 5, 7, and 9, respectively, after 96 h. Moreover, Abamectin-MSN@PAA effectively preserved abamectin from degradation under UV light exposure. In comparison with abamectin suspension, Abamectin-MSN@PAA exhibited superior adhesion to radish leaves and demonstrated increased aphid mortality in bioassay experiments. Following 7 days of drug spraying, the aphid survival rate was 26.67 % for Abamectin (40 mg L−1) and only 18.3 % for Abamectin-MSN@PAA (40 mg L−1). These findings underscore the potential of pH-responsive poly(acrylic acid)-coated mesoporous silica nanoparticles as a versatile platform for controlled pesticide delivery, thereby enhancing pesticide bioavailability and efficacy in agriculture.

Tank-Mix Adjuvants Enhance Pesticide Efficacy by Improving Physicochemical Properties and Spraying Characteristics for Application to Cotton with Unmanned Aerial Vehicles.

Tank-mix adjuvants have been used to reduce spray drift and facilitate the efficacy of pesticides applied with unmanned aerial vehicles (UAVs). However, the effects of specific adjuvants on pesticide characteristics and the mechanism of action remain unclear. Herein, we analyzed the effects of three different types of tank-mix adjuvants (plant oil; mineral oil; and mixture of alcohol and ester) on the surface tension (ST), contact angle, wetting, permeation, evaporation, spray performance, and aphid-control effects of two types of pesticides. The mineral oil adjuvant Weichi (WCH) was highly effective in reducing the pesticide solution ST, improving the wetting and penetration ability, increasing droplet size, and promoting droplet deposition. The mixed alcohol and ester adjuvant Quanrun (QR) showed excellent wetting and antievaporation properties and promoted droplet deposition. A plant oil adjuvant (Beidatong) moderately improved wetting and penetration ability and reduced droplet drift. Field tests showed that the control efficiencies (CEs) of two pesticides were increased after the addition of adjuvants, even with 20% reductions in pesticide application. When the UAV was operated at 1.5 m, the CEs of two pesticides were increased from 65.39 and 66.63% to 73.11-76.52% and 77.91-88.31%, respectively. When operated at 2.5 m, the CEs were increased from 51.24 and 68.60% to 65.06-75.70% and 77.57-92.59%, respectively. Especially, the CEs of pesticides with WCH and QR increased obviously. Importantly, neither WCH nor QR inhibited hatching of the critical insect natural enemy ladybird beetle at concentrations used in the field. This study provides a framework for assessment of tank-mix adjuvants in aerial sprays and directly demonstrates the value of specific adjuvants in improving pesticide bioavailability and minimizing associated environmental pollution.

Excellent Foliar Deposition of Cyclodextrin‐Encapsulated Furyl/Thienyl‐Engineered Ingredients: Novel Effective Supramolecular Agrochemicals for Combating Plant Bacterial and Fungal Infections

AbstractRepeated epidemics caused by bacterial and fungal diseases pose a threat to global crop yields and food security, therefore, updating the structure of existing microbicides and improving the pesticide bioavailability are challenging tasks, perhaps planning to develop versatile supramolecular antimicrobial materials. Here, a low‐cost multifunctional supramolecular complex, named FT6@β‐CD, is constructed by host‐guest encapsulation of a thienyl‐engineered ingredient (FT6) into β‐cyclodextrin. This integrated architecture can significantly reduce the bounce and splash behaviors of droplets, improve the wetting performance, and eventually acquire excellent foliar deposition and targeted delivery. Whereafter, FT6@β‐CD can inhibit the transcription of type III secretion system (T3SS)‐associated genes, hypersensitive reaction, and final pathogenicity from a destructive pathogen Xanthomonas oryzae pv. oryzae (Xoo). Importantly, at a lower dosage of 200 µg mL−1, FT6@β‐CD presented excellent in vivo control effects (protection 48.1%, curative 50.1%) against Xoo, remarkably better than the commercial bactericidal formulation thiodiazole‐copper. Additionally, other supramolecular antifungal materials (FT24/FT25@HP‐β‐CD/β‐CD/Me‐β‐CD) constructed in this study can effectively treat Botryosphaeria dothidea and Botrytis cinerea with higher control efficiencies of 86.8% and 90.1% at 200 µg mL−1, respectively. This study provides a bright guidance for developing low‐cost, green, and eco‐friendly supramolecular microbicides for controlling agricultural diseases.

An enzyme-responsive core-double shell structured nano pesticide delivery system for improving the UV stability of emamectin benzoate (EB)

Currently, the inefficient application of pesticides results in substantial cost wastage and severe environmental contamination. The rapid advancement of nanomaterials and controlled/sustained-release technologies offer a promising guidance for reducing pesticide usage and enhancing pesticide bioavailability. In this study, naturally derived Zein and β-cyclodextrin (β-CD) polysaccharide were employed for synergistic encapsulation of emamectin benzoate (EB) pesticide molecule. Specifically, amino-functionalized Zein (AM-Zein) was effectively self-assembled onto β-cyclodextrin (β-CD) through electrostatic and hydrogen bonding interactions, with simultaneous encapsulation of EB through hydrophobic interactions, thereby establishing a core-double shell structured nano pesticide delivery system (EB@β-CD/AM-Zein). Compared to the single AM-Zein and β-CD, the double shell structured β-CD/AM-Zein demonstrated a notably higher encapsulation efficiency for EB. Importantly, the half-life period (t0.5) under UV irradiation of EB for EB@β-CD/AM-Zein was almost three times longer than that of EB alone. Enzyme-responsive controlled-release tests for EB@β-CD/AM-Zein revealed that the majority of EB was encapsulated within the inner β-CD layer. Specifically, the degradation of β-CD by α-amylase enabled the intelligent responsive release feature of EB. Moreover, the insecticidal activity of EB@β-CD/AM-Zein remained stable. This research offers valuable insights for developing effective and environmentally safe nano pesticide systems.

Emamectin-sodium alginate nano-formulation based on charge attraction with highly improved systemic translocation and photolysis resistance

Nano pesticides offer an effective means of improving the bioavailability of pesticide due to their excellent solubility and wettability, superior foliar adhesion, and permeability to target insects. By using high-speed homogenization and ultrasonic dispersion technology, an emamectin-sodium alginate nano-formulation (EB@SA) with a particle size ranging from 30 to 50 nm was successfully fabricated using electrostatic self-assembly. The microscopic morphology and structure of EB@SA were further analyzed through transmission electron microscopy, dynamic light scattering, infrared spectroscopy, and 1H NMR. The photolysis resistance behavior of EB@SA demonstrated an improved anti-photolysis ability more than double that of conventional formulations while also exhibiting good sustained-release properties. Not only does EB@SA maintain the inherent insecticidal toxicity of emamectin benzoate (EB), but it also significantly prolongs its insecticidal duration. At a concentration of 20 mg/L, the lethality rate against Armyworms remains above 70 % over a period of 16 days compared to <50 % for general emamectin emulsifiable concentrate. Furthermore, EB@SA greatly enhances the systemic translocation of EB in corn plants by exhibiting favorable bidirectional systemic translocation characteristics. This research presents an efficient and environmentally friendly pesticide nano-formulation that can be effectively utilized for field pest control.

Ecofriendly polysaccharide-based alginate/pluronic F127 semi-IPN hydrogel with magnetic collectability for precise release of pesticides and sustained pest control

Controlled-release systems are crucial for efficient pesticide utilization and environmental protection in agricultural production. The utilization of polysaccharide-based materials derived from biopolymers as carriers for controlling pesticide release holds significant potential. In this work, a reversible near infrared-responsive polysaccharide-based hydrogel (RNPH) was fabricated by employing a semi-interpenetrating polymer network (alginate-FeIII/pluronic F127) as a carrier to encapsulate Fe3O4@polydopamine (FP) and emamectin benzoate (EB)-loaded hollow mesoporous silica. The incorporation of FP into the RNPH introduced a photothermal effect, enabling the precise release of EB through reversible shrinkage of the hydrogel upon NIR irradiation. Additionally, the presence of magnetic Fe3O4 in the system facilitated the rapid removal of remaining RNPH from the environment using a magnet, reducing EB residue. Importantly, RNPH exhibited exceptional controlled-release performance and could be reused for at least 4 cycles. Furthermore, the anti-photolysis ability of EB protected by RNPH was enhanced by 4.8 times compared to EB alone. Moreover, RNPH significantly improved the adhesion of EB to foliar surfaces, thereby reducing the loss of EB while ensuring crop safety. Therefore, the polysaccharide-based hydrogel holds promise as a versatile carrier for the precise release of EB, offering valuable applications in enhancing pesticide bioavailability and promoting environmental safety.

Carboxymethyl β-cyclodextrin grafted hollow copper sulfide@mesoporous silica carriers for stimuli-responsive pesticide delivery

Stimuli-responsive controlled release systems have received extensive attention to improve the pesticide bioavailability and minimize environmental pollution. Herein, a multiple stimuli-responsive IMI@HCuS@mSiO2 @ -ss-CβCD delivery system was constructed using modified carboxymethyl β-cyclodextrin (CβCD-ss-COOH) as sealing materials, hollow copper sulfide nanoparticles with amino-functionalized mesoporous silica shell (HCuS@mSiO2-NH2) as carriers and imidacloprid (IMI) as the model drug. The cavity structure of HCuS@mSiO2-NH2 would provide a large space for pesticide loading. The results revealed that HCuS@mSiO2-ss-CβCD was approximately 230 nm in size and the loading efficiency for IMI was 25.7%, and exhibited better biosafety on bacteria and seed. HCuS carriers were also served as photothermal agent and possessed high photothermal conversion effect (η = 38.4%). IMI@HCuS@mSiO2 @ -ss-CβCD displayed excellent foliage adhesion and multiple stimuli-responsive release properties to pH, α-amylase, GSH, and NIR. The photostability of IMI embedded in CuS@mSiO2 @ -ss-CβCD was approximately 10 times that of IMI solution. This work provides an efficient nanoplatform for realizing pesticide delivery.

Cellulose Nanofiber Platform for Pesticide Sequestration in the Gastrointestinal Tract.

Exploitation of nature-derived materials is an important approach to promote environmental sustainability. Among these materials, cellulose is of particular interest due to its abundance and relative ease of access. As a food ingredient, cellulose nanofibers (CNFs) have found interesting applications as emulsifiers and modulators of lipid digestion and absorption. In this report, we show that CNFs can also be modified to modulate the bioavailability of toxins, such as pesticides, in the gastrointestinal tract (GIT) by forming inclusion complexes and promoting interaction with surface hydroxyl groups. CNFs were successfully functionalized with (2-hydroxypropyl)-β-cyclodextrin (HPBCD) using citric acid as a crosslinker via esterification. Functionally, the potential for pristine and functionalized CNFs (FCNFs) to interact with a model pesticide, boscalid, was tested. Based on direct interaction studies, adsorption of boscalid saturated at around 3.09% on CNFs and at 12.62% on FCNFs. Using an in vitro GIT simulation platform, the adsorption of boscalid on CNFs/FCNFs was also studied. The presence of a high-fat food model was found to have a positive effect in binding boscalid in a simulated intestinal fluid environment. In addition, FCNFs were found to have a greater effect in retarding triglyceride digestion than CNFs (61% vs 30.6%). Overall, FCNFs were demonstrated to evoke synergistic effects of reducing fat absorption and pesticide bioavailability through inclusion complex formation and the additional binding of the pesticide onto surface hydroxyl groups on HPBCD. By adopting food-compatible materials and processes for production, FCNFs have the potential to be developed into a functional food ingredient for modulating food digestion and the uptake of toxins.

Residues and Bioavailability of Neonicotinoid Pesticide in Shaanxi Agricultural Soil

Residues and Bioavailability of Neonicotinoid Pesticide in Shaanxi Agricultural Soil

Adsorption-Desorption Behavior and Pesticide Bioavailability of Biochar in Soil

Biochar is a porous carbon-rich substance generated by anoxic pyrolysis of biomass. Biochar has a high adsorption capacity for organic contaminants in water and soil environmental media due to its large specific surface area and surface physical and chemical characteristics. The effects of biochar application on the adsorption-desorption behavior and bioavailability of pesticides in soil are illustrated in this paper; biochar can strongly adsorb pesticides in soil due to its loose and porous properties, large specific surface area and surface energy, and highly aromatic structure. Residual pesticide pollutants are reduced, as is desorption hysteresis, which reduces pesticide desorption. Furthermore, the use of biochar reduced the absorption and efficacy of pesticides in soil. At the same time, it describes the present gaps in research on the influence of biochar on pesticide migration mechanisms and its application in pesticide pollution control, and it identifies the major scientific issues that need to be addressed. Finally, the potential application of biochar in pesticide pollution management is discussed.

The simple strategy to improve pesticide bioavailability and minimize environmental risk by effective and ecofriendly surfactants

Low pesticide efficiency has caused serious environmental pollution and economic loss, which are closely related to each link in the targeted delivery of pesticides. However, the existing strategies for improving pesticide utilization rate are not comprehensive, and the regulation of foliar absorption and biological activity has been neglected. As surfactants are the most important agricultural synergists, the impact, wetting, adhesion, and leaf retention behaviors of pyraclostrobin (PYR) droplets containing the surfactant Triton X (TX) series on hydrophobic scallion leaf surfaces were studied. The results showed that TX-102 can sufficiently reduce the splash and roll of droplets when they impact inclined leaves, owing to its low dynamic surface tension. Moderate wetting ability and high adhesion also maximizes leaf retention of the TX-102-added PYR solution sprayed on scallion leaves. Furthermore, TX-102 improved the permeation and absorption of PYR in scallion leaves through the synergistic effects of opening the stomata and dissolving the waxy layer. The synergistic bioactivity of TX-102 against pathogenic fungi Alternaria porri and its safety to non-target organism zebrafish have also been demonstrated. Our study provides a more comprehensive theoretical rationale for screening adjuvants to improve the effectiveness and bioavailability of pesticides and reduce the risk of pesticides entering the environment.

Effects of tank-mix adjuvants on physicochemical properties and dosage delivery at low dilution ratios for unmanned aerial vehicle application in paddy fields.

Unmanned aerial vehicles (UAVs) have been developed to improve the efficiency of pesticide applications, and they are now widely utilized in Asia. The deposition and retention periods of pesticides on plant surfaces present serious challenges for modern precision agriculture, as these factors directly affect pesticide bioavailability, efficacy, and loss. Tank-mix adjuvants have been utilized to improve pesticide performance, but their effects on physicochemical properties and dosage delivery at low dilutions are not well understood. We found that different tank-mix adjuvants affected droplet impact behavior, the wetting and spreading of spray dilutions, and pesticide deposition on rice leaves by changing the physicochemical properties of spray dilutions. The adjuvant methyl oxirane polymer with oxirane, mono (3,5,5-trimethylhexyl) ether (adjuvant c) significantly reduced the dynamic surface tension of the spray dilution and inhibited the rebound of large droplets (D0 =2 ± 0.2 mm) and spray droplets (0.2MPa with a LU-01 nozzle) on rice leaves, and improved the wetting and spreading performance of the spray dilution on rice leaves. Field tests showed that adjuvant c could significantly increase the deposition of chlorantraniliprole on rice leaves. Overall, the use of appropriate tank-mix adjuvants at low dilution ratios for UAV application in paddy fields can improve the performance of spray dilutions, increase the effective deposition and wetting spread of pesticides on rice leaves, further reduce the dosage of pesticide products and improve pesticide utilization. © 2022 Society of Chemical Industry.

Development of Chlorantraniliprole and Lambda Cyhalothrin Double-Loaded Nano-Microcapsules for Synergistical Pest Control.

Nanotechnology could greatly improve global agricultural food production. Chlorantraniliprole and lambda cyhalothrin double-loaded nano-microcapsules were fabricated to enhance the control of pests by pesticides and improve the pesticide utilization efficiency. The nano-microcapsules were synthesized using a method involving the solid in oil in water encapsulation technique and solvent evaporation. The nano-microcapsules slowly and simultaneously released lambda cyhalothrin and chlorantraniliprole. The cumulative lambda cyhalothrin and chlorantraniliprole release rates at 40 h were 80% and 70%, respectively. Indoor Spodoptera frugiperda control tests indicated that the double-loaded nano-microcapsules were more toxic than lambda cyhalothrin water-dispersible granules, chlorantraniliprole water-dispersible granules, and a mixture of lambda cyhalothrin water-dispersible granules and chlorantraniliprole water-dispersible granules, indicating that the pesticides in the nano-microcapsules synergistically controlled Spodoptera frugiperda. The results indicated that pesticide nano-microcapsules with synergistic effects can be developed that can improve the effective pesticide utilization efficiency and pesticide bioavailability. This is a new idea for achieving environmentally intelligent pesticide delivery.

Pesticide effects on nitrogen cycle related microbial functions and community composition

The extensive application of pesticides in agriculture raises concerns about their potential negative impact on soil microorganisms, being the key drivers of nutrient cycling. Most studies have investigated the effect of a single pesticide on a nutrient cycling in single soil type. We, for the first time, investigated the effect of 20 commercial pesticides with different mode of actions, applied at their recommended dose and five times their recommended dose, on nitrogen (N) microbial cycling in three different agricultural soils from southern Australian. Functional effects were determined by measuring soil enzymatic activities of β-1,4-N-acetyliglucosaminidase (NAG) and l-leucine aminopeptidase (LAP), potential nitrification (PN), and the abundance of functional genes involved in N cycling (amoA and nifH). Effects on nitrifiers diversity were determined with amplicon sequencing. Overall, the pesticides effect on N microbial cycling was dose-independent and soil specific. The fungicides flutriafol and azoxystrobin, the herbicide chlorsulfuron and the insecticide fipronil induced a significant reduction in PN and β-1,4-N-acetylglucosaminidase activity (P < 0.05) (NAG) in the alkaline loam soil with low organic carbon content i.e. a soil with properties which typically favors pesticide bioavailability and therefore potential toxicity. For the nitrifier community, the greatest pesticide effects were on the most dominant Nitrososphaeraceae (ammonia-oxidizing archaea; AOA) whose abundance increased significantly compared to the less dominant AOA and other nitrifiers. The inhibiting effects were more evident in the soil samples treated with fungicides. By testing multiple pesticides in a single study, our findings provide crucial information that can be used for pesticide hazard assessment.

Cyclodextrin polymer-valved MoS2-embedded mesoporous silica nanopesticides toward hierarchical targets via multidimensional stimuli of biological and natural environments

Targeted delivery of pesticides towards pests and pathogens can significantly improve the bioavailability and efficacy of pesticides and minimize the impact on the environment. Cyclodextrin polymer (CDP)-valved, benzimidazole functionalized, MoS2-embedded mesoporous silica (MoS2@MSN@CDP) nanopesticides were constructed toward hierarchical biological targets of pests, pathogens, and foliage. The splash and bounce of the aqueous droplets containing MoS2@MSN@CDP nanoparticles in the presence of Aersosol OT on superhydrophobic surfaces were well inhibited available for excellent wetting to prevent pesticides from losing to the environment. The multivalent supramolecular nanovalves between CDP and the functionalized benzimidazole moieties could be activated for the controlled release of pesticides in the cases of low pH and α-amylase. It is the first time to report the foliage-triggered controlled release of pesticides, owing to the competitive binding of epicuticular wax components to CDP. Furthermore, thermogenic MoS2 cores triggered the controlled release of pesticides under irradiation of near infrared light. The fungicidal efficacies of the stimuli-responsive nanopesticides against pathogenic fungi Rhizoctonia solani and Fusarium graminearum were demonstrated. It is clear that the smart nanopesticides could realize the controlled release of pesticides toward hierarchical biological targets for enhanced pesticide bioavailability and efficacy via the multidimensional stimuli of pH, α-amylase, epicuticular waxes, and sunlight.

Route of exposure influences pesticide body burden and the hepatic metabolome in post-metamorphic leopard frogs.

Pesticides are being applied at a greater extent than in the past. Once pesticides enter the ecosystem, many environmental factors can influence their residence time. These interactions can result in processes such as translocation, environmental degradation, and metabolic activation facilitating exposure to target and non-target species. Most anurans start off their life cycle in aquatic environments and then transition into terrestrial habitats. Their time in the aquatic environment is generally short; however, many important developmental stages occur during this tenure. Post-metamorphosis, most species spend many years on land but migrate back to the aquatic environment for breeding. Due to the importance of both the aquatic and terrestrial environments to the life stages of amphibians, we investigated how the route of exposure (i.e., uptake from contaminated soils vs. uptake from contaminated surface water) influences pesticide bioavailability and body burden for four pesticides (bifenthrin (BIF), chlorpyrifos (CPF), glyphosate (GLY), and trifloxystrobin (TFS)) as well as the impact on the hepatic metabolome of adult leopard frogs (Gosner stage 46 with 60-90days post-metamorphosis). Body burden concentrations for amphibians exposed in water were significantly higher (ANOVA p<0.0001) compared to amphibians exposed to contaminated soil across all pesticides studied. Out of 80 metabolites that were putatively identified, the majority expressed a higher abundance in amphibians that were exposed in pesticide contaminated water compared to soil. Ultimately, this research will help fill regulatory data gaps, aid in the creation of more accurate amphibian dermal uptake models and inform continued ecological risk assessment efforts.

Occurrence of agricultural pesticides in Mississippi Delta Bayou sediments and their effects on the amphipod: Hyalella azteca

ABSTRACT Agricultural activity enhances topsoil erosion and facilitates the transport of pesticides that alter watershed sediment quality. Agricultural stream (bayou) sediment quality in Mississippi, USA, was evaluated across three bayous, habitats (upstream, midstream, downstream), and seasonally from 2011 to 2014 for pesticide contamination, effects, and bioavailability to Hyalella azteca. Four-week (28-day) H. azteca sediment bioassays were conducted to assess survival and growth and tissue residues. Fourteen pesticides were detected in at least one sediment sample and nine pesticides were detected in H. azteca tissues. Sediment pesticides p,p’-DDT and p,p’-DDE were greatest in Cow Oak Bayou and heptachlor and bifenthrin were greatest in Howden Lake Bayou. Seasonally, λ-cyhalothrin and p,p’-DDT were greatest in winter while trifluralin, atrazine, and clomazone were greatest in the fall. H. azteca survival and growth ranged from 0 to 100% and 0.8–4.1 mg, respectively, with Cow Oak, downstream habitats, and spring samples having the greatest survival and growth. Greatest tissue pesticide residues were atrazine (1271 µg/kg), p,p’-DDT (1,093 µg/kg), and β-cyfluthrin (1003 µg/kg). Tissue pesticide residues were influenced primarily by p,p’-DDT with Cow Oak and fall tissue samples having the lowest residues. H. azteca tissue p,p’-DDT residues contributed to biological impairment. Although banned in the USA for 40 years, p,p’-DDT continues to impact sediment quality.

A Review on Adsorption and Desorption of Different Pesticides in Various Soil

Pesticides are important to the success of agriculture as well as an inevitable factor to maintain good public health. Over the years, the consumption of pesticides has increased manifold, particularly during the past two decades. However, this increase has caused great concern over the presence of residues or leftover pesticides in the environment. The understanding of adsorption and desorption behavior of different pesticides is an important phenomenon to describe the fate of pesticide in soil and other environmental compartment like water and sediment. The soil is considered as ultimate sink of pesticide as these were reached to soil directly or indirectly from the point/non-point sources. Adsorption–desorption processes are necessary in understanding pesticides retention behavior and its potential mobility within the soil. The behavior of pesticides in the soil depends on factors such as the physico-chemical properties of pesticides, the active surface of mineral, organic components and the amount of the pesticide applied. Henceforth, adsorption and desorption of soil applied pesticides needed to deal with greater sincerity. This review primarily ascertains dominant properties of pesticides including surface area, pH, surface functional groups, carbon content and aromatic structure and evaluate the adsorption and desorption of pesticide in agricultural soils. In addition, a vision for future research prospects has been anticipated by considering the pesticide bioavailability as residues in soil, influence of soil organic matter, clay content, pH and soil temperature on pesticide removal, pesticide properties and its behavior in soils.

Spatial variation of organochlorine pesticides and dissolved organic matter in urban closed lakes

Closed lakes located in urban parks act as sinks of organochlorine pesticides (OCPs), which have been used, for decades, as insecticides, herbicides and fungicides. The closed lakes from Bucharest, Romania, are periodically managed to prevent eutrophication and accumulation of pollutants. However, it is not known if these practices reduce or enhance the legacy pollution with OCPs. The aim of this study was to explore the spatial variation of OCPs in closed lakes. The total concentration of OCPs in water and sediments ranged between 0.0176 and 37.1 µg/L, and between 122 to 1,890 ng/g, respectively. The concentrations of OCPs were compared with the consensus-based sediment quality guidelines (SQGs) in order to evaluate the ecological risks of sediments. The highest potential adverse effects were associated with γ-HCH exposure. Periodical draining and dredging of lakes lead to the resuspension of contaminants, increasing pesticide bioavailability and accumulation in sediments. In addition, we observed that fluorescent dissolved organic matter (DOM) might influence the OCPs cycle. The quantity and character of fluorescent DOM can provide further insight into OCPs degradation. Also, this study may help urban planners to determine the state of urban waters and to find the best solution for water management.

Relationship between pesticide accumulation in transplanted zebra mussel (Dreissena polymorpha) and community structure of aquatic macroinvertebrates

This study examined to what degree bioaccumulated pesticides in transplanted zebra mussels can give an insight to pesticide bioavailability in the environment. In addition, it was investigated if pesticide body residues could be related to ecological responses (changes in macroinvertebrate community composition). For this at 17 locations, 14 pesticide concentrations and nine dissolved metals were measured in translocated zebra mussels and the results were related to the structure of the macroinvertebrate community. Critical body burdens in zebra mussel, above which the ecological status was always low, could be estimated for chlorpyrifos, terbuthylazine and dimethoate being respectively 8.0, 2.08 and 2.0 ng/g dry weight.With multivariate analysis, changes in the community structure of the macroinvertebrates were related to accumulated pesticides and dissolved metals. From this analysis, it was clear that the composition of the macroinvertebrate communities was not only affected by pesticides but also by metal pollution. Two different regions could be clearly separated, one dominated by metal pollution, and one where pesticide pollution was more important.The results of this study demonstrated that zebra mussel body burdens can be used to measure pesticide bioavailability and that pesticide body burdens might give insight in the ecological impacts of pesticide contamination. Given the interrelated impacts of pesticides and heavy metals, it is important to further validate all threshold values before they can be used by regulators.