Expanding Wetland Mitigation: Can Rice Fields Remediate Pesticides in Agricultural Runoff?

Abstract

Pesticides are responsible for nearly 1900 water quality impairments in the United States. Impacts of pesticide runoff on aquatic ecosystems can be mitigated by implementing management practices such as constructed wetlands, grass buffers, and vegetated ditches. A new practice currently being examined is the use of rice (Oryza sativa L.) fields for phytoremediation of pesticide‐contaminated water. Rice is cultivated on every continent except Antarctica and is the staple food crop of 20% of the world's population. Four flooded 244‐m2 fields (two planted with rice, two left bare) were amended with a mixture of atrazine (C8H14ClN5), diazinon (C12H21N2O3PS), and permethrin (C21H20Cl2O3) during a one‐time simulated storm event, and pesticide concentrations and loads were monitored in water, sediment, and plant samples. The experiment was repeated the following year. Significant differences were noted for mitigation of atrazine and diazinon loads in rice versus bare systems. Overall, atrazine loads in the water of rice systems decreased 85 ± 8% from inflow to outflow, while atrazine loads in the water of bare systems decreased 58 ± 7%. Similar patterns were seen for diazinon (86 ± 4% versus 62 ± 7%), cis‐permethrin (94 ± 2% versus 64 ± 12%), and trans‐permethrin (97 ± 2% versus 67 ± 14%). All three pesticides were found repeatedly sorbed to plant material in the inflow and outflow areas during the first year, while the second year resulted in much less plant‐pesticide contribution to overall mitigation. Further investigation is needed to compare rice's mitigation capacity of different pesticide classes, as well as potential transfer of pesticides to edible seeds. Core Ideas Atrazine and diazinon loads significantly decreased in systems containing rice. Permethrin loads decreased in rice systems but also sorbed to unvegetated sediment. Rice may have the potential to remove pesticides from water column and serve as a food crop.

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

“…The primary studies that showed high removal efficiencies (greater than 75%) were larger for mesocosm studies. Of the studies that analyzed the mesocosm scale, 68% had at least one contaminant removed at an efficiency greater than or equal to 75% [16,23,45 160,173,174,184,186,187,189,191,196,206,208,212]. However, efficiencies between studies for specific contaminants and/or classes were not able to undergo statistical evaluation due to few studies having the same contaminant and/or class evaluated.…”

“…The least studied systems were depressions, ephemeral wetlands, wetland buffers, recirculating constructed wetlands, and salt marshes each appearing only once throughout the primary studies. However, six studies investigated the ability of rice fields to mitigate nutrients, pesticides, and antibiotics as a wetland system in Mississippi, U.S. [63,160,174], India [56], China [115], and Spain [103] with high removal efficiencies (58-100%) for several different contaminants (e.g., diazinon, benthocarb, carbofuran, atrazine, permethrin, NH 4 + -N, NO 3 -N, nitrate-N).…”

Metal Organic Frameworks (MOFs) as Photocatalysts for the Degradation of Agricultural Pollutants in Water

“…Herbicides account for about 62% of total pesticides usage in agriculture in the United States, and the five most used herbicides during the past two decades were glyphosate, atrazine, metolachlor-( S ), 2,4-D, and acetochlor . As one of the most frequently detected pesticides, the concentration of atrazine in surface water in the Midwest and South of the US reached 53 μg/L in 2018 . Very few pesticides are completely mineralized after biotic or abiotic degradation.…”

“…18 As one of the most frequently detected pesticides, the concentration of atrazine in surface water in the Midwest and South of the US reached 53 μg/L in 2018. 19 Very few pesticides are completely mineralized after biotic or abiotic degradation. Some of their degradation intermediates, which possess even higher toxicity, have been detected at higher concentrations in drinking water and surface water compared to their parent forms.…”

Pesticide peak concentration reduction in a small vegetated treatment system controlled by chemograph shape

“…VTSs studied in literature include very different types of systems (Lange et al, 2011), including vegetated ditches or detention ponds with hydraulic retention times (HRT) ranging in the order of minutes to several hours (Bundschuh et al, 2016;Elsaesser et al, 2011) or constructed wetlands in which HRT may reach several weeks, when operated in batch mode (Tournebize et al, 2017;Maillard et al, 2016). Pesticide mitigation has also been observed in other systems in which water is temporally stored such as barrage fish ponds (Gaillard et al, 2016) or rice fields (Moore et al, 2018). While contaminant mass loss (RM) is mainly observed in systems with longer HRT, systems with short HRT have been shown to efficiently reduce peak concentration (RC) and the associated acute toxicity (Bundschuh et al, 2016;Elsaesser et al, 2011;Stehle et al, 2011).…”