Experiments in water-macrophyte systems to uncover the dynamics of pesticide mitigation processes in vegetated surface waters/streams

Arch Environ Contam Toxicol

Anderson

et al. 2022

The Salinas Valley in Monterey County, California, USA, is a highly productive agricultural region. Irrigation runoff containing pesticides at concentrations toxic to aquatic organisms poses a threat to aquatic ecosystems within local watersheds. This study monitored the effectiveness of a constructed wetland treatment system with a granulated activated carbon (GAC) filter installation at reducing pesticide concentrations and associated toxicity to Ceriodaphnia dubia, Hyalella azteca, and Chironomus dilutus. The wetland was supplied with water pumped from an impaired agricultural and urban drainage. Across five monitoring trials, the integrated system’s average pesticide concentration reduction was 52%. The wetland channel and GAC filtration components individually provided significant treatment, and within each, pesticide solubility had a significant effect on changes in pesticide concentrations. The integrated treatment system also reduced nitrate by 61%, phosphate by 73%, and turbidity by 90%. Input water was significantly toxic to C. dubia and H. azteca in the first trial. Toxicity to C. dubia persisted throughout the system, whereas toxicity to H. azteca was removed by the channel, but there was residual toxicity post-GAC. The final trial had significant input toxicity to H. azteca and C. dilutus. The channel reduced toxicity to H. azteca and removed toxicity to C. dilutus. GAC filtration reduced H. azteca toxicity to an insignificant level. There was no input toxicity in the other three trials. The results demonstrate that a wetland treatment system coupled with GAC filtration can reduce pesticide concentrations, nutrients, suspended particles, and aquatic toxicity associated with agricultural runoff.

Section: Discussionmentioning

confidence: 99%

Effectiveness of a Constructed Wetland with Carbon Filtration in Reducing Pesticides Associated with Agricultural Runoff

McCalla

Arch Environ Contam Toxicol

Anderson

et al. 2022

“…These methods may need further refinement to address emerging pesticides, such as neonicotinoids. Because of their high solubility, vegetation does not sorb these pesticides (Stang et al 2015), so carbon treatment (Voorhees et al 2017) or system designs that promote further solar or bacterial degradation may be necessary.…”

Section: Management Vision—approaches Tailored To Agricultural and Urban Pesticidesmentioning

confidence: 99%

Water Quality Impairments Due to Aquatic Life Pesticide Toxicity: Prevention and Mitigation in California, USA

Moran¹,

Anderson

Environmental Toxicology and Chemistry

et al. 2020

The management of pesticides to protect water quality remains a significant global challenge. Historically, despite regulatory frameworks intended to prevent, minimize, and manage off‐site movement of pesticides, multiple generations of pesticide active ingredients have created a seemingly unending cycle of pesticide water pollution in both agricultural and urban watersheds. In California, the most populous and most agricultural US state, pesticide and water quality regulators realized in the 1990s that working independently of each other was not an effective approach to address pesticide water pollution. Over the years, these California agencies have developed a joint vision and have continued to develop a unified approach that has the potential to minimize pesticide risks to aquatic life through a combination of prevention, monitoring, and management actions, while maintaining pesticide availability for effective pest control. Key elements of the current California pesticide/water quality effort include: 1) pesticide and toxicity monitoring, coupled with watershed modeling, to maximize information obtained from monitoring; 2) predictive fate and exposure modeling to identify potential risks to aquatic life for new pesticide products when used as allowed by the label or to identify effective mitigation measures; and 3) management approaches tailored to the different pesticide uses, discharge sources, physical environments, and regulatory environments that exist for agricultural runoff, urban runoff, and municipal wastewater. Lessons from this effort may inform pesticide management elsewhere in the world as well as other chemical regulatory programs, such as the recently reformed US Toxic Substances Control Act and California's Safer Consumer Products regulatory program. Environ Toxicol Chem 2020;39:953–966. © 2020 SETAC

“…Many water soluble pesticides such as neonicotinoids are not effectively treated by VTS (Stang et al 2016) and the use and detections of this class of insecticides are increasing in agricultural regions of California (Deng 2015;Deng et al 2019). Imidacloprid is used in conjunction with pyrethroids on most lettuce crops in the Salinas Valley, and has recently been detected in irrigation runoff in the central coast region.…”

Section: Introductionmentioning

confidence: 99%

Treating Agricultural Runoff With A Mobile Carbon Filtration Unit

McCalla

Siegler

et al. 2022

Preprint

Several classes of pesticides have been shown to impair water quality in California, including organophosphates, pyrethroids and neonicotinoids. Vegetative treatment systems (VTS) can reduce pesticide loads and associated toxicity in agricultural runoff, but many water soluble pesticides such as neonicotinoids are not effectively treated by VTS, and VTS installation is not always an option for growers required to remove non-crop vegetation for food safety concerns. Recent studies have shown that biochar filtration can be used to remove soluble contaminants, especially when coupled with other VTS components. We evaluated a mobile carbon filter system consisting of a trailer-mounted tank containing approximately 600L of biochar. Input water from a 1080 acre agricultural drainage was pre-filtered and treated with biochar during two multi-week study periods. Laboratory toxicity tests, and chemical and nutrient analyses were conducted on input and output water. Pesticide concentrations were initially reduced by greater than 99%. Treatment efficacy declined linearly and was expected to remain at least 50% effective for up to 34 weeks. Toxicity was assessed with Ceriodaphnia dubia, Hyalella azteca and Chironomus dilutus. Significant input toxicity was reduced to non-toxic levels in 6 of 16 samples. Some input concentrations of the neonicotinoid imidacloprid and the pyrethroid cypermethrin exceeded organism-specific toxicity thresholds and benchmarks, but the overall causes of toxicity were complex mixtures of agricultural chemicals. Nutrients were not reduced by the biochar. Results demonstrate the utility of biochar in treating agricultural runoff, and provide measures of the longevity of biochar under field conditions.