Influence of varying nutrient and pesticide mixtures on abatement efficiency using a vegetated free water surface constructed wetland mesocosm

Abstract

The nutrient and pesticide abatement efficiency of varying mixtures was examined in a vegetated free water surface constructed wetland. Three different agricultural chemical pollutant mixture conditions were assessed: nutrients only (N and P); pesticides only (atrazine, S-metolachlor and permethrin); and a mixture of nutrients and pesticides. With nutrients only, 672 h nutrient mitigation of 77-91% total phosphorous (TP) and 74-98% total nitrogen (TN) was associated with distance from the injection point and rainfall, whereas with nutrient and pesticide mixtures, 672 h nutrient mitigation of 11-71% TP and 84-98% TN were associated with distance and time. With pesticides only, 672 h pesticide mitigation of 50-99% was associated with distance and time, whereas with nutrients and pesticide mixtures, 672 h pesticide mitigation of 48-99% was associated primarily with distance. Dissipation half-lives were 2-10 times greater for P and 1.5-5 times greater for N when pesticides were present. Pesticide dissipation half-lives showed no clear differences with or without nutrients. While vegetated free water surface constructed wetlands can be effective best management practice tools to trap and abate agricultural run-off during rainfall events, efficiencies can be affected by different types of complex pollutant mixtures and wetland design and implementation should accommodate varying efficiencies.

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

“…Only one study in 2020 considered a runoff mixture containing antibiotics, nutrients, pesticides, and other pharmaceuticals [103]. Of these studies that looked at mixtures, only 16 specifically analyzed the impact on nitrogen removal in the presence of different contaminants [23,30,58,59,67,97,102,103,[112][113][114]120,131,169,179,181,201]. Thus, the data shows that only recently have some of these contaminants started to be studied individually, in the case of antibiotics, but also as mixtures.…”

“…Sorption to wetland media was a removal mechanism of focus for 18% of the primary studies (Table 5). This included studies that compared different media types [67,104,170] or analyzed the amount of contaminant sorbed to the wetland media by determining the concentrations of contaminants [74,87,135,170,229] or determining sorption isotherm coefficients for the media [137,196,198]. The different media types found in the primary studies included biochar [59,170,179,192], straw [133,134], compost [170], different types of soil [67,145,196,197], gravel [104, 161,229], pebbles [179], zeolite [59,114,147,218], and cobbles [104].…”

“…Overall, the type of contaminants present has been reported to impact sorption processes due to competing cations [87] and differences between highly vs. weakly sorbing contaminants [54]. Additionally, sedimentation or sorption was not the primary removal mechanism in wetland systems with the presence of multiple removal mechanisms (e.g., increased hydraulic retention time, vegetation, microbial activity); instead, it enhanced contaminant removal [67,74,84,115,135,196,218]. For example, Uddin et al (2019) found electrical conductivity, total organic carbon, and total nitrogen in the soil significantly impacted microbial richness and diversity [115].…”

“…The location of the wetlands for these 31 primary studies with the highest removal efficiencies of TN and NO 3 -N occurred in the United States [67,99], while the highest removal efficiencies of NH 4 -N and pesticides occurred in the United States and Greece [77,99,218]. In contrast, the highest efficiencies of antibiotic removal occurred in China [58].…”

“…Several primary studies reported the impact of CUPs' and antibiotics' presence on nitrogen removal efficiencies. Of these, seven studies reported that the specific contaminant analyzed decreased nitrogen removal [30,58,67,113,114,169]. The impact of CUPS and antibiotics on nutrient removal was mainly attributed to a decline in the microbial communities responsible for nutrient metabolism and degradation [30,114,131,169], where the presence of plants and type of plant species [23,102,120,201], saturated vs. unsaturated conditions [120,201], weather conditions [201], and timing [48,169] also played a role in N removal in the presence of CUPS or antibiotics.…”