Mitigation of two pyrethroid insecticides in a Mississippi Delta constructed wetland

Attenuation Effect of Azolla spp. on Lambda-Cyhalothrin Toxicity to Aquatic Organisms

Wetlands play a crucial role in providing valuable ecosystem services, including the removal of various pollutants. In agricultural basins, wetlands are exposed to agrochemical loads. This study aims to assess the attenuation effect of the ubiquitous macrophyte Azolla spp. on the toxicity of lambda-cyhalothrin to sensitive aquatic organisms. An indoor mesocosm experiment was conducted to compare the concentration of lambda-cyhalothrin at different time points after pesticide application in vegetated and unvegetated treatments, including a control without pesticide addition. Toxicity tests were performed throughout the experiment on three organisms: a fish (Cnesterodon decemmaculatus), a macroinvertebrate (Hyalella curvispina), and an amphibian (Boana pulchella). The results demonstrated that lambda-cyhalothrin concentration and toxicity in water were significantly lower in the Azolla spp. treatment. Furthermore, the half-life of lambda-cyhalothrin decreased from 1.2 days in the unvegetated treatment to 0.4 days in the vegetated treatment. The vegetated treatment also resulted in a significantly lower mortality rate for both H. curvispina and C. decemmaculatus. However, no mortality was observed in B. pulchella for any of the treatments. Sublethal effects were observed in this organism, such as lateral bending of the tail and impairment of the ability to swim, which were attenuated in the vegetated treatment. We conclude that Azolla spp. can effectively reduce the concentration and toxicity of lambda-cyhalothrin, suggesting its potential use in farm-scale best management practices to mitigate the effects of pesticide loads from adjacent crops.

Reduced concentrations and toxicity of sediment-associated pesticides from vegetable planting field to surrounding waterways: Impacts of chemical properties and intrinsic toxicity

Pesticides from agricultural activities transfer to surrounding waterways, jeopardizing aquatic ecosystem. To better characterize transfer of pesticide residues and toxicity, a batch of pesticides were analyzed in 22 sediment samples collected from the ditches (< 5 m away from field) and receiving streams nearby a vegetable planting area, South China. Sum concentrations of pesticides in ditch sediments (152 ± 121 ng/g dry wt.) were higher than those in stream sediments (24.9 ± 14.9 ng/g dry wt.). Toxicity reduction from ditch to stream was different for two invertebrates. Stream sediment toxicity to Chironomus dilutus decreased considerably but elevated toxicity was still observed (50% mortality on average), while stream sediments exhibited no significant lethality to Hyallela azteca (< 10% mortality). Fipronil and its transformation products (FIPs) were responsible for sediment toxicity to the midges, and pyrethroids contributed significantly to the death of the amphipods. Hydrophobic pyrethroids were tended to stay in the ditches, whereas FIPs were detected in stream sediments at considerable concentrations due their possible transfer to the nearby streams and/or residential use. This physicochemical property-related transfer characteristics and intrinsic toxicity of the major toxicants explained the distinct toxicity reduction patterns for the two species, which highlighted their importance in assessing aquatic transfer and risk of agriculture derived pesticides.

Reversion of CYP450 monooxygenase-mediated acetamiprid larval resistance in dengue fever mosquito, Aedes aegypti L

Aedes-borne diseases are on the rampant rise despite continued application of chemical insecticide-based interventions. The appearance of high degree of insecticide resistance in Aedes species and noxious effects on environment and non-targets have raised further concerns. Among new chemical interventions, neonicotinoids are considered a safe and effective approach. The present study investigated the control potency of acetamiprid and development of resistance in Aedes aegypti larvae; and the involvement of CYP450 monooxygenases in inducing resistance. The early fourth instars of Ae. aegypti parent susceptible strain (PS) were selected with acetamiprid for 15 generations (ACSF strain) increasing the resistance to 19.74-fold in ACSF-10 and 36.71-fold in ACSF-15. The ACSF-10 larvae were assayed with acetamiprid combined with piperonyl butoxide (PBO) in three different ratios (1:1, 1:5 and 1:10) and selected for next five generations with 1:10 combination. Selection with synergized acetamiprid (APSF strains) reversed as well as reduced the rate of resistance development resulting in only 1.35-fold resistance in APSF-15. The APSF strains showed %monooxygenase dependency ranging from 86.71 to 96.72%. The estimation of the monooxygenases levels in parent and selected larvae showed increased monooxygenase level in the ACSF strains by 2.42-2.87-fold. The APSF-15 strains exhibited 57.95% lower enzyme production than ACSF-15 strain. The reduction and reversion of resistance by using PBO and the elevated levels of monooxygenases in ACSF and reduction in APSF strains recommend the involvement of CYP450-mediated mechanism in the development of acetamiprid resistance in Ae. aegypti. These studies could help in devising resistance management strategies in order to preserve the efficiency of pre-existing insecticides.

Chronic exposure to deltamethrin disrupts intestinal health and intestinal microbiota in juvenile crucian carp

The indiscriminate use of deltamethrin in agriculture and aquaculture can lead to residues increased in many regions, which poses negative impacts on intestinal health of aquatic organisms. Although the potential toxicity of deltamethrin have recently attracted attention, the comprehensive studies on intestinal injuries after chronic deltamethrin exposure remain poorly understood. Herein, in a 28-day chronic toxicity test, crucian carp expose to different concentrations of deltamethrin (0, 0.3, and 0.6 μg/L) were used as the research object. We found that the morphology changes and increased goblet cells in intestinal tissue, and the extent of tissue injury increased along with the increasing exposure dose of deltamethrin. Additionally, the genes expression of antioxidant activity (Cu/Zn superoxide dismutase (Cu-Zn SOD), glutathione peroxidase 1 (GPX1), and catalase (CAT)), inflammatory response (tumor necrosis factor alpha (TNFα), interferon gamma (IFNγ), and interleukin 1 beta (IL-1β)), and tight junctions (Claudin 12 (CLDN12), and tight junction protein 1 (ZO-1)) dramatically increased. Meanwhile, the apoptosis and autophagy process were triggered through caspase-9 cascade and autophagy related 5 (ATG5)- autophagy related 12 (ATG12) conjugate. Besides, chronic deltamethrin exposure increased the amount of Proteobacteria and Verrucomicrobiota, while decreased Fusobacteriota abundance, resulting in intestinal microbiota function disorders. In summary, our results highlight that chronic exposure to deltamethrin cause serious intestinal toxicity and results in physiological changes and intestinal flora disturbances.

Can Pesticides Dissolved in Runoff and Exposed to Maturing Rice (Oryza sativa) Plants be Transferred to Seeds?

Agriculture's global challenge to feed an estimated 7.7 billion people is further exacerbated by less available cropland for production and rapidly changing climate patterns. Pesticides are often utilized to minimize crop losses due to pest infestations; however, problems arise when these chemicals are transported off production acreage, either by storm or irrigation events, and into nearby water bodies. Innovative management practices are needed to not only reduce the volume of runoff, but also to mitigate various pollutants, such as pesticides, within the runoff. One such practice being evaluated involves using rice (Oryza sativa) as a pesticide mitigation tool. While rice plants may serve as a mechanism for phytoremediation, whether the seeds harvested from exposed plants could then be utilized as a human food source is an unanswered question. Thirty round mesocosms (55 L volume; 56 cm diameter; six replicates per treatment) were established with rice and exposed to aqueous concentrations of the pesticides clomazone, propanil, or cyfluthrin, as well as a mixture of the three pesticides. Six replicates with rice and no pesticide exposure served as controls. Initial pesticide exposure took place 8 weeks post-planting and continued once a week for 5 weeks. Rice plants, unmilled seeds, and mesocosm sediment were collected from each mesocosm 2 weeks after seed formation began and analyzed for pesticide concentrations using gas chromatography. Concentrations of pesticides in unmilled seed were below detection for individual exposures of clomazone, propanil, and cyfluthrin. When rice was exposed to the pesticide mixture, the mean ± SE unmilled seed cyfluthrin concentration was 14.8 ± 1.25 µg kg^-1. These small-scale, preliminary studies offer insight into the possibility of using immature rice plants as a phytoremediation tool, while harvesting its grain after plant maturation for human consumption. Further research is needed to address this question on a larger scale and with multiple pesticide mixtures.

A Literature Review of Wetland Treatment Systems Used to Treat Runoff Mixtures Containing Antibiotics and Pesticides from Urban and Agricultural Landscapes

Wetland treatment systems are used extensively across the world to mitigate surface runoff. While wetland treatment for nitrogen mitigation has been comprehensively reviewed, the implications of common-use pesticides and antibiotics on nitrogen reduction remain relatively unreviewed. Therefore, this review seeks to comprehensively assess the removal of commonly used pesticides and antibiotics and their implications for nitrogen removal in wetland treatment systems receiving non-point source runoff from urban and agricultural landscapes. A total of 181 primary studies were identified spanning 37 countries. Most of the reviewed publications studied pesticides (n = 153) entering wetlands systems, while antibiotics (n = 29) had fewer publications. Even fewer publications reviewed the impact of influent mixtures on nitrogen removal processes in wetlands (n = 16). Removal efficiencies for antibiotics (35–100%), pesticides (−619–100%), and nitrate-nitrogen (−113–100%) varied widely across the studies, with pesticides and antibiotics impacting microbial communities, the presence and type of vegetation, timing, and hydrology in wetland ecosystems. However, implications for the nitrogen cycle were dependent on the specific emerging contaminant present. A significant knowledge gap remains in how wetland treatment systems are used to treat non-point source mixtures that contain nutrients, pesticides, and antibiotics, resulting in an unknown regarding nitrogen removal efficiency as runoff contaminant mixtures evolve.

Attenuation of insecticide impact by a small wetland in a stream draining a horticultural basin in Argentina

Horticulture has greatly increased in Argentina in recent decades mainly due to increasing greenhouse utilization and agrochemical consumption, thus representing a threat to adjacent water bodies. Riparian wetlands, however, could attenuate agrochemical contamination. The present work therefore compared insecticide concentrations in bottom sediments in addition to sediment toxicity to the amphipod Hyalella curvispina and investigated the macroinvertebrate composition upstream and downstream from a natural wetland in a small stream draining a basin undergoing intense horticultural production. The wetland surface was covered by macrophytes, mainly Thypha sp., and the insecticide concentrations measured downstream from the wetland were significantly lower, at roughly 19% of the upstream values. The growth rates of H. curvispina were significantly higher when exposed to the sediments downstream from the wetland, while the macroinvertebrate-assemblage composition was significantly different upstream and downstream: the snail Pomacea canaliculata was the dominant species upstream while the amphipod H. curvispina was dominant downstream. Pomacea canaliculata is often the dominant species in the regional streams draining agriculture and horticultural basins. Hyalella curvispina is sensitive to pesticide toxicity and is often dominant in streams draining extensive livestock basins and within a biosphere reserve. We conclude that riparian wetlands effectively attenuate horticulture contamination in pampean streams and should therefore be preserved and restored.

Sub-lethal effects of permethrin exposure on a passerine: implications for managing ectoparasites in wild bird nests

Permethrin is increasingly used for parasite control in bird nests, including nests of threatened passerines. We present the first formal evaluation of the effects of continued permethrin exposure on the reproductive success and liver function of a passerine, the zebra finch (Taeniopygia guttata), for two generations. We experimentally treated all nest material with a 1% permethrin solution or a water control and provided the material to breeding finches for nest building. The success of two consecutive clutches produced by the parental generation and one clutch produced by first-generation birds were tracked. Finches in the first generation were able to reproduce and fledge offspring after permethrin exposure, ruling out infertility. Permethrin treatment had no statistically significant effect on the number of eggs laid, number of days from clutch initiation to hatching, egg hatch rate, fledgling mass or nestling sex ratio in either generation. However, treating nest material with permethrin significantly increased the number of hatchlings in the first generation and decreased fledgling success in the second generation. Body mass for hatchlings exposed to permethrin was lower than for control hatchlings in both generations, but only statistically significant for the second generation. For both generations, an interaction between permethrin treatment and age significantly affected nestling growth. Permethrin treatment had no effect on liver function for any generation. Permethrin was detected inside 6 of 21 exposed, non-embryonated eggs (28.5% incidence; range: 693-4781 ng of permethrin per gram of dry egg mass). Overall, results from exposing adults, eggs and nestlings across generations to permethrin-treated nest material suggest negative effects on finch breeding success, but not on liver function. For threatened bird conservation, the judicious application of this insecticide to control parasites in nests can result in lower nestling mortality compared to when no treatment is applied. Thus, permethrin treatment benefits may outweigh its sub-lethal effects.

Effectiveness of wastewater treatment systems in removing microbial agents: a systematic review

Background

Due to unrestricted entry of wastewater into the environment and the transportation of microbial contaminants to humans and organisms, environmental protection requires the use of appropriate purification systems with high removal efficiency for microbial agents are needed. The purpose of this study was to determine the efficacy of current wastewater treatment systems in removing microbes and their contaminants.

Methods

A systematic review was conducted for all articles published in 5 Iranian environmental health journals in 11 years. The data were collected according to the inclusion and exclusion criteria and by searching the relevant keywords in the articles published during the years (2008–2018), with emphasis on the efficacy of wastewater treatment systems in removing microbial agents. Qualitative data were collected using a preferred reporting items for systematic reviews and meta-analyzes (PRISMA) standard checklist. After confirming the quality of the articles, information such as the name of the first author and the year of publication of the research, the type of study, the number of samples, the type of purification, the type of microbial agents and the rate of removal of microbial agents were entered into the checklist. Also the removal rates of the microbial agents mentioned in the studies were compared with united states environmental protection agency (US-EPA) standards.

Results

In this study, 1468 articles retrieved from 118 issues of 5 environmental health journals were reviewed. After reviewing the quality of the articles in accordance with the research objectives, 14 articles were included in the study that were published between 2010 and 2018. In most studies, two main indicators Total coliforms and Fecal coliforms in wastewater were investigated. Removing fungi and viral contamination from wastewater was not found in any of the 14 studies. Different systems (activated sludge, stabilization ponds, wetlands, and low and medium pressure UV disinfection systems were used to remove microbial agents in these studies. Most articles used active sludge systems to remove Total coliforms and Fecal coliforms, which in some cases were not within the US-EPA standard. The removal of Cysts and Parasitic eggs was only reporte from stabilization pond systems (SPS) where removal efficiency was found in accordance with US-EPA standards.

Conclusions

Different types of activated sludge systems have higher efficacy to remove microbial agents and are more effective than other mentioned systems in removing the main indicators of sewage contamination including Total coliforms and Fecal coliforms. However, inappropriate operation, maintenance and inadequate handling of activated sludge can also reduce its efficiency and reduce the removal of microbial agents, which was reported in some studies. Therefore, it is recommended to conduct research on how to improve the operation, maintenance, and proper management of activated sludge systems to transfer knowledge to users of sludge systems and prevent further health issues related to microbial agents.

Integrated wetlands for food production

The widespread use of compound pelleted feeds and chemical fertilizers in modern food production contribute to a vast amount of residual nutrients into the production system and adjacent ecosystem are major factors causing eutrophication. Furthermore, the extensive development and application of chemical compounds (such as chemical pesticides, disinfectants and hormones used in enhancing productivity) in food production process are hazardous to the ecosystems, as well as human health. These unsustainable food production patterns cannot sustain human living in the long run. Wetlands are perceived as self-decontamination ecosystems with high productivities. This review gives an overview about wetlands which are being integrated with food production processes, focusing on aquaculture.

Structural and metabolic responses of microbial community to sewage-borne chlorpyrifos in constructed wetlands

Long-term use of chlorpyrifos poses a potential threat to the environment that cannot be ignored, yet little is known about the succession of substrate microbial communities in constructed wetlands (CWs) under chlorpyrifos stress. Six pilot-scale CW systems receiving artificial wastewater containing 1mg/L chlorpyrifos were established to investigate the effects of chlorpyrifos and wetland vegetation on the microbial metabolism pattern of carbon sources and community structure, using BIOLOG and denaturing gradient gel electrophoresis (DGGE) approaches. Based on our samples, BIOLOG showed that Shannon diversity (H') and richness (S) values distinctly increased after 30days when chlorpyrifos was added. At the same time, differences between the vegetated and the non-vegetated systems disappeared. DGGE profiles indicated that H' and S had no significant differences among four different treatments. The effect of chlorpyrifos on the microbial community was mainly reflected at the physiological level. Principal component analysis (PCA) of both BIOLOG and DGGE showed that added chlorpyrifos made a difference on test results. Meanwhile, there was no difference between the vegetation and no-vegetation treatments after addition of chlorpyrifos at the physiological level. Moreover, the vegetation had no significant effect on the microbial community at the genetic level. Comparisons were made between bacteria in this experiment and other known chlorpyrifos-degrading bacteria. The potential chlorpyrifos-degrading ability of bacteria in situ may be considerable.

Reference scenarios for exposure to plant protection products and invertebrate communities in stream mesocosms

Higher tier aquatic risk assessment for plant protection products (PPPs) is often based on pond-like mesocosm studies in which transient and dynamic PPP exposure scenarios as observed in lotic systems are hardly achievable. Thus, the present study presents dynamic PPP exposure scenarios at different time scales under flow-through conditions as typical for streams in agricultural landscapes. The stream mesocosm setup allows testing the influence of spatial gradients of exposure over the length of themesocosms. The use of the fluorescent tracer uranine revealed the hydraulic processes generally underlying peak- and hour-scale exposure scenarios and demonstrated an optimized application technique to achieve stable day-scale exposures. Furthermore, to account for potential reactions of invertebrates to PPP exposures in streams (e.g. avoidance behavior and drift), the present study thus aimed at a comprehensive evaluation on how PPP exposure and the establishment of invertebrates can be advanced within streammesocosm testing. For both, peak- and hour-scale exposure as well as the experiments considering the establishment of invertebrates, the presented compilation of experiments was able to highlight the influence of aquatic macrophyteswithin streammesocosms. Since the field relevance of the higher tier aquatic risk assessment for PPPs relies qualitatively on the presence of potentially sensitive or vulnerable species, those species were especially considered. Thus, the establishment of aquatic invertebrates in nondosed streams was evaluated with respect to (i) the presence of different aquatic macrophytes and (ii) the duration of the pre-experimental period. The present study highlights the beneficial influence of complex-structured macrophytes and prolonged pre-experimental periods on the abundance of invertebrate taxa. Furthermore, population dynamics were evaluated statistically by simulating PPP-related declines of 30, 50 and 70%. Thereby,

Potential of barrage fish ponds for the mitigation of pesticide pollution in streams

Barrage fishponds may represent a significant surface water area in some French regions. Knowledge on their effect on water resources is therefore necessary for the development of appropriate water quality management plans at the regional scale. Although there is much information on the nutrient removal capacity of these water bodies, little attention has been paid to other agricultural contaminants such as pesticides. The present paper reports the results of a 1-year field monitoring of pesticide concentrations and water flows measured upstream and downstream from a fishpond in North East France to evaluate its capacity in reducing pesticide loads. Among the 42 active substances that had been applied on the fishpond's catchment, seven pesticides (five herbicides, two fungicides) were studied. The highest concentration in the inflow to the pond was 26.5 μg/L (MCPA), while the highest concentration in pond outflow was 0.54 μg/L (prosulfocarb). Removal rates of dissolved pesticides in the fishpond ranged from 0-8% (prosulfocarb) to 100% (clopyralid). Although not primarily designed for the treatment of diffuse sources of pesticides, the studied fishpond had the potential to do so.

Stormwater-related transport of the insecticides bifenthrin, fipronil, imidacloprid, and chlorpyrifos into a tidal wetland, San Francisco Bay, California

Suisun Marsh, in northern San Francisco Bay, is the largest brackish marsh in California, and provides critical habitat for many fish species. Storm runoff enters the marsh through many creeks that drain agricultural uplands and the urban areas of Fairfield and Suisun City. Five creeks were sampled throughout a major storm event in February 2014, and analyzed for representatives of several major insecticide classes. Concentrations were greatest in creeks with urban influence, though sampling was done outside of the primary season for agricultural pesticide use. Urban creek waters reached maximum concentrations of 9.9 ng/l bifenthrin, 27.4 ng/l fipronil, 11.9 ng/l fipronil sulfone, 1462 ng/l imidacloprid, and 4.0 ng/l chlorpyrifos. Water samples were tested for toxicity to Hyalella azteca and Chironomus dilutus, and while few samples caused mortality, 70% of the urban creek samples caused paralysis of either or both species. Toxic unit analysis indicated that bifenthrin was likely responsible for effects to H. azteca, and fipronil and its sulfone degradate were responsible for effects to C. dilutus. These results demonstrate the potential for co-occurrence of multiple insecticides in urban runoff, each with the potential for toxicity to particular species, and the value of toxicity monitoring using multiple species. In the channels of Suisun Marsh farther downstream, insecticide concentrations and toxicity diminished as creek waters mixed with brackish waters entering from San Francisco Bay. Only fipronil and its degradates remained measurable at 1-10 ng/l. These concentrations are not known to present a risk based on existing data, but toxicity data for estuarine and marine invertebrates, particularly for fipronil's degradates, are extremely limited.

Pesticide mass budget in a stormwater wetland

Wetlands are reactive landscape zones that provide ecosystem services, including the improvement of water quality. Field studies distinguishing pesticide degradation from retention to evaluate the sink and source functions of wetlands are scarce. This study evaluated based on a complete mass budget the partitioning, retention, and degradation of 12 pesticides in water, suspended solids, sediments, and organisms in a wetland receiving contaminated runoff. The mass budget showed the following: (i) dissolved pesticides accounted for 95% of the total load entering the wetland and the pesticide partitioning between the dissolved phase and the suspended solids varied according to the molecules, (ii) pesticides accumulated primarily in the <250 μm bed sediments during spring and late summer, and (iii) the hydrological regime or the incoming pesticide loads did not influence the pesticide dissipation, which varied according to the molecules and the wetland biogeochemical conditions. The vegetation enhanced the pesticide degradation during the vegetative phase and the pesticides were released during plant senescence. The dithiocarbamates were degraded under oxic conditions in spring, whereas glyphosate and aminomethylphosphonic acid (AMPA) degradation occurred under reducing conditions during the summer. The complete pesticide mass budget indicates the versatility of the pesticide sink and source functions of wetland systems.

Indicator pathogens, organic matter and LAS detergent removal from wastewater by constructed subsurface wetlands

BACKGROUND

Constructed wetland is one of the natural methods of municipal and industrial wastewater treatments with low initial costs for construction and operation as well as easy maintenance. The main objective of this study is to determine the values of indicator bacteria removal, organic matter, TSS, ammonia and nitrate affecting the wetland removal efficiency.

RESULTS

The average concentration of E. coli and total coliform in the input is 1.127 × 1014 and 4.41 × 1014 MPN/100 mL that reached 5.03 × 1012 and 1.13 × 1014 MPN/100 mL by reducing 95.5% and 74.4% in wetland 2. Fecal streptococcus reached from the average 5.88 × 1014 in raw wastewater to 9.69 × 1012 in the output of wetland 2. Wetland 2 could reduce 1.5 logarithmic units of E. coli. The removal efficiency of TSS for the wetlands is 68.87%, 71.4%, 57.3%, and 66% respectively.

CONCLUSIONS

The overall results show that wetlands in which herbs were planted had a high removal efficiency about the indicator pathogens, organic matter, LAS detergent in comparison to a control wetland (without canes) and could improve physicochemical parameters (DO, ammonia, nitrate, electrical conductivity, and pH) of wastewater.

Mitigating agrichemicals from an artificial runoff event using a managed riverine wetland

We examined the mitigation efficiency of a managed riverine wetland amended with a mixture of suspended sediment, two nutrients (nitrogen and phosphorus), and three pesticides (atrazine, metolachlor, and permethrin) during a simulated agricultural runoff event. Hydrologic management of the 500 m-long, 25 m-wide riverine wetland was done by adding weirs at both ends. The agrichemical mixture was amended to the wetland at the upstream weir simulating a four-hour, ~1cm rainfall event from a 16ha agricultural field. Water samples (1L) were collected every 30 min within the first 4h, then every 4h until 48 h, and again on days 5, 7, 14, 21, and 28 post-amendment at distances of 0m, 10 m, 40 m, 300 m and 500 m from the amendment point within the wetland for suspended solids, nutrient, and pesticide analyses. Peak sediment, nutrient, and pesticide concentrations occurred within 3 h of amendment at 0m, 10 m, 40 m, and 300 m downstream and showed rapid attenuation of agrichemicals from the water column with 79-98%, 42-98%, and 63-98% decrease in concentrations of sediments, nutrients, and pesticides, respectively, within 48 h. By day 28, all amendments were near or below pre-amendment concentrations. Water samples at 500 m showed no changes in sediment or nutrient concentrations; pesticide concentrations peaked within 48 h but at ≤11% of upstream peak concentrations and had dissipated by day 28. Managed riverine wetlands≥1 ha and with hydraulic residence times of days to weeks can efficiently trap agricultural runoff during moderate (1cm) late-spring and early-summer rainfall events, mitigating impacts to receiving rivers.

Responses of Hyalella azteca and phytoplankton to a simulated agricultural runoff event in a managed backwater wetland

We assessed the aqueous toxicity mitigation capacity of a hydrologically managed floodplain wetland following a synthetic runoff event amended with a mixture of sediments, nutrients (nitrogen and phosphorus), and pesticides (atrazine, S-metolachlor, and permethrin) using 48-h Hyalella azteca survival and phytoplankton pigment, chlorophyll a. The runoff event simulated a 1h, 1.27 cm rainfall event from a 16 ha agricultural field. Water (1L) was collected every 30 min within the first 4h, every 4h until 48 h, and on days 5, 7, 14, 21, and 28 post-amendment at distances of 0, 10, 40, 300 and 500 m from the amendment point for chlorophyll a, suspended sediment, nutrient, and pesticide analyses. H. azteca 48-h laboratory survival was assessed in water collected at each site at 0, 4, 24, 48 h, 5 d and 7 d. Greatest sediment, nutrient, and pesticide concentrations occurred within 3h of amendment at 0m, 10 m, 40 m, and 300 m downstream. Sediments and nutrients showed little variation at 500 m whereas pesticides peaked within 48 h but at <15% of upstream peak concentrations. After 28 d, all mixture components were near or below pre-amendment concentrations. H. azteca survival significantly decreased within 48 h of amendment up to 300 m in association with permethrin concentrations. Chlorophyll a decreased within the first 24h of amendment up to 40m primarily in conjunction with herbicide concentrations. Variations in chlorophyll a at 300 and 500 m were associated with nutrients. Managed floodplain wetlands can rapidly and effectively trap and process agricultural runoff during moderate rainfall events, mitigating impacts to aquatic invertebrates and algae in receiving aquatic systems.

The application of zero-water discharge system in treating diffuse village wastewater and its benefits in community afforestation

The proposed on-site zero-water discharge system was comprised of four main components: anaerobic tank, aerobic bioreactor, activated soil filter and water-collecting well. The results demonstrate that at 350 m(3) day(-1) of hydraulic load, the system can effectively remove pollutants from the wastewater, e.g., 86% removal of COD; 87% removal of SS; 80% removal of TP and 71% removal of TN. The growth states of the grasses, macrophytes and arbors in the activated soil filter were better than the control. The life of the activated soil filter was estimated to be ~12-15 yrs, based on the laboratory microcosm studies. However, humic acid contents and soil porosity have suggested that the activated soil filter was able to regenerate itself and thereby prolonging its life by reducing clogging of the pores. The results suggest that the zero-water discharge system was a promising bio-measure in treating diffuse village wastewater and benefiting community afforestation.

Copper clean-up procedure for ultrasonic extraction and analysis of pyrethroid and phenylpyrazole pesticides in sediments by gas chromatography-electron capture detection

A rapid ultrasonic extraction method coupled with a heated-copper clean-up procedure for removing interfering constituents was developed for analyzing pyrethroid and phenylpyrazole pesticides in sediments. Incubation of the 60 mL extract with 12 g copper granules at 60 °C for 2h was determined to be the optimal conditions for removing the interfering constituents. Eleven pyrethroid and phenylpyrazole pesticides were spiked into sediment samples to determine the effectiveness of the ultrasonic extraction method. The average recoveries of pyrethroids and phenylpyrazoles in sediment at 4 °C storage on day 0, 1, 7, 14, and 21 ranged from 98.6 to 120.0%, 79.2 to 116.0%, 85.0 to 119.7%, 93.6 to 118.7%, and 92.1 to 118.2%, respectively, with all percent relative standard deviations less than 10% (most <6%). This illustrated the stability of pyrethroids and phenylpyrazoles in sediment during sediment aging at 4 °C. Recoveries of the pesticides ranged from 98.6% to 120.0% for lowest fortification level (2-16 μg kg⁻¹), from 97.8% to 117.9% for middle fortification level (10-80 μg kg⁻¹), and from 94.3% to 118.1% for highest fortification level (20-160 μg kg⁻¹). Relative standard deviations of pesticide recoveries were usually less than 7%. Method detection limits of target pesticides ranged from 0.22 μg kg⁻¹ to 3.72 μg kg⁻¹. Furthermore, field sediment samples collected from four residential lakes during a three-month monitoring period were analyzed to evaluate the effectiveness of this method. Bifenthrin was detected in all of sediment samples (highest concentration 260.33±41.71 μg kg⁻¹, lowest concentration 5.68±0.38 μg kg⁻¹, and fipronil sulfone was detected at least once in sediment samples collected from three sites with concentrations ranging from 1.73±0.53 to 7.53±0.01 μg kg⁻¹.

Selected pesticides adsorption and desorption in substrates from artificial wetland and forest buffer

Buffer zones such as artificial wetlands and forest buffers may help decrease non-point-source pesticide pollution from agricultural catchments. The present study focuses on understanding the role of the substrates mainly found in such buffer zones for pesticide adsorption and desorption. Radiolabeled [(14)C]isoproturon, [(14)C]metazachlor, and [(14)C]epoxiconazole were used to measure adsorption and desorption isotherms on wetland sediments and plants and forest soil and litter from two sites in France. Wetland sediments and forest soil exhibited the most important potential for pesticide adsorption. Wetland plants and forest litter also showed high adsorption coefficients and were associated with highly hysteretic desorption, particularly for the moderately mobile isoproturon and metazachlor. Adsorption of the highly hydrophobic epoxiconazole was strong and associated with weak desorption from all substrates. Calculated sorption coefficients were larger than those classically measured on soils. Isoproturon, metazachlor, and epoxiconazole K(OC) sorption coefficients ranged from 84 to 372, 131 to 255, and 1,356 to 3,939 L/kg, respectively. Therefore, specifically collecting buffer zone substrate sorption data is needed for modeling purposes. Results showed that forests and wetlands present potential for pesticide retention. This may be enhanced by planting vegetation and leaving dead vegetal material in buffer zone design.

Pesticide risk mitigation by vegetated treatment systems: a meta-analysis

Pesticides entering agricultural surface waters threaten water quality and aquatic communities. Recently, vegetated treatment systems (VTSs) (e.g., constructed wetlands and vegetated ditches) have been proposed as pesticide risk mitigation measures. However, little is known about the effectiveness of VTSs in controlling nonpoint source pesticide pollution and factors relevant for pesticide retention within these systems. Here, we conducted a meta-analysis on pesticide mitigation by VTSs using data from the scientific literature and the European LIFE ArtWET project. Overall, VTSs effectively reduced pesticide exposure levels (i.e., the majority of pesticide retention performances was >70%). A multiple linear regression analysis of 188 retention performance cases identified the two pesticide properties, organic carbon sorption coefficient value and water-phase 50% dissipation time, as well as the VTS characteristics overall plant coverage and hydraulic retention time for targeting high efficacy of pesticide retention. The application of a Tier I risk assessment (EU Uniform Principle) revealed a higher toxicity reduction for hydrophobic and nonpersistent insecticides compared with less sorptive and not readily degradable herbicides and fungicides. Overall, nearly half (48.5%) of all pesticide field concentrations ( = 130) failed Tier I standard risk assessment at the inlet of VTSs, and 29.2% of all outlet concentrations exceeded conservative acute threshold levels. We conclude that VTSs are a suitable and effective risk mitigation strategy for agricultural nonpoint source pesticide pollution of surface waters. Further research is needed to improve their overall efficacy in retaining pesticides.

Removal mechanisms and fate of insecticides in constructed wetlands

Constructed wetlands (CWs), along with other vegetative systems, are increasingly being promoted as a mitigation practice to treat non-point source runoff to reduce contaminants such as pesticides. However, studies so far have mostly focused on demonstrating contaminant removal efficiency. In this study, using two operational CWs located in the Central Valley of California, we explored the mechanisms underlying the removal of pyrethroids and chlorpyrifos from agricultural runoff water, and further evaluated the likelihood for the retained pesticides to accumulate within the CWs over time. In the runoff water passing through the CWs, pyrethroids were associated overwhelmingly with suspended solids >0.7 μm, and the sorbed fraction accounted for 38-100% of the total concentrations. The derived K(d) values for the suspended solids were in the order of 10(4)-10(5), substantially greater than those reported for bulk soils and sediments. Distribution of pyrethroids in the wetland sediments was found to mimic organic carbon distribution, and was enriched in large particles that were partially decomposed plant materials, and clay-size particles (<2 μm). Retention of suspended particles, especially the very large particles (>250 μm) and the very fine particles, is thus essential in removing pyrethroids and chlorpyrifos in CWs. Under flooded and anaerobic conditions, most pyrethroids and chlorpyrifos showed moderate persistence, with DT(50) values between 106-353 d. However, the retained pyrethroids were very stable in dry and aerobic sediments between irrigation seasons, suggesting a possibility for accumulation over time. Therefore, the long-term ecological risks of CWs should be further understood before their wide adoption.

Constructed wetlands as a component of the agricultural landscape: mitigation of herbicides in simulated runoff from upland drainage areas

Constructed wetlands are a recommended practice for buffering pollutant source areas and receiving waters. A wetland consisting of a sediment trap and two treatment cells was constructed in a Mississippi Delta lake watershed. A 3-h simulated runoff event was initiated (2003) to evaluate fate and transport of atrazine and fluometuron through the wetland. Water samples were collected during a runoff simulation and then afterward at selected intervals for 21d, and analyzed for the herbicides. Breakthrough patterns for herbicide concentrations in water samples during the first 20h after simulated runoff showed peak concentrations in the first 6h, with gradual tailing as the herbicide pulse was diluted in the second, excavated (deeper) cell. Atrazine and fluometuron concentrations in the first (shallower, non-excavated) cell averaged 12- and 20-fold greater, respectively, than those in the second cell following simulated runoff, indicating entrapment in the first cell. Atrazine and fluometuron concentrations in the shallower cell decreased 32% and 22%, respectively, 9d following simulated runoff, indicating either degradation or sorption to soil or wetland flora. In the excavated cell, concentrations were even lower, and atrazine declined more rapidly than fluometuron. Results indicate constructed wetlands can improve downstream water quality though sequestration or processing of pollutants.

Removal of pesticide mixtures in a stormwater wetland collecting runoff from a vineyard catchment

Wetlands can collect contaminated runoff from agricultural catchments and retain dissolved and particle-laden pesticides. However, knowledge about the capacity and functioning of wetland systems with respect to the removal of pesticides is very limited. Here we show that stormwater wetlands can efficiently remove pesticides in runoff from vineyard catchments during the period of pesticide application, although flow and hydrochemical conditions of the wetland largely vary over time. During the entire agricultural season, the inflowing load of nine fungicides, six herbicides, one insecticide and four degradation products was 8.039g whereas the outflowing load was 2.181g. Removal rates of dissolved loads by the wetland ranged from 39% (simazine) to 100% (cymoxanil, gluphosinate, kresoxim methyl and terbuthylazine). Dimethomorph, diuron, glyphosate, metalaxyl and tetraconazole were more efficiently removed in spring than in summer. More than 88% of the input mass of suspended solids was retained, underscoring the capability of the wetland to trap pesticide-laden particles via sedimentation. Only the insecticide flufenoxuron was frequently detected in the wetland sediments. Our results demonstrate that stormwater wetlands can efficiently remove pesticide mixtures in agricultural runoff during critical periods of pesticide application, although fluctuations in the runoff regime and hydrochemical characteristics can affect the removal rates of individual pesticides.