A zero-valent iron and organic matter mixture enhances herbicide and herbicide degradation product removal in subsurface waters

Abstract

The pesticide atrazine, its degradation products, and 2,6-dichlorobenzamide (BAM) are persistent in groundwater environment. We studied whether their dissipation can be enhanced with a mixture of a complex carbon source and zero-valent iron (ZVI) called EHC®. The application rates were 1.0% and 2.0% (by weight) in subsurface sediments slurries (atrazine 30mg/L), and 2.0% in 1.5m pilot-scale sediment columns with groundwater flowing through (atrazine 0.08, desethylatrazine DEA 0.03, BAM 0.02μg/L). In the slurries under aerobic conditions, atrazine of 0.88±0.14mg/g of EHC® was dissipated chemically, as concentrations did not differ significantly between the slurries and their sterilized controls. No degradation occurred in the slurries under anaerobic conditions. In the pilot-scale columns under water-saturated conditions, atrazine, DEA and BAM were not detected in effluents during 33, 64 and 64days from the beginning of the water flow through EHC® columns, respectively, but thereafter traces of compounds could be detected. No atrazine or degradation products (BAM, DEA, deisopropylatrazine, desethyldeisopropylatrazine) could be extracted from the column sediments at the end of the experiment. As a result, the sum of dissipated pesticides was about 7.6μg/g of EHC® in columns under water-saturated conditions, and 0.88mg/g of EHC® in slurries under aerobic conditions. EHC® can be used to enhance the dissipation of studied pesticides in small quantities, preferentially under aerobic conditions.

Improved Short-Term Microbial Degradation in Circulating Water Reducing High Stagnant Atrazine Concentrations in Subsurface Sediments

“…Although iron has been associated with the remediation of some pollutants [17,25], and the sediments of this study naturally contained about 12 mg g −1 of iron, it apparently did not significantly improve the chemical dissipation of colloid-bound atrazine. NH 4 -N and NO 3 -N concentrations below the detection limit suggest that nitrogen limited microbial growth in the sediments, and atrazine was used as the nitrogen source (Table 3).…”

Effects of tall fescue biochar on the adsorption behavior of desethyl-atrazine in different types of soil

“…Previously, the degradation of atrazine and its major metabolites (DEA and DIA) in water by photocatalytic oxidation under sunlight has achieved good results (Komtchou et al 2018). The use of a carbon source plus zero-valent iron under aerobic conditions can also effectively promote the dissipation of atrazine and DEA at a relatively low pollution level (Kerminen et al 2017). However, different remediation methods vary considerably and are limited by high energy consumption and excessive pollutant concentrations.…”

Non‐traditional atrazine degradation induced by zero‐valent‐copper: process optimization by the Doehlert experimental design, intermediates detection and toxicity assessment

“…ATZ has thus been the target of many studies regarding the development of alternative treatment techniques, such as AOPs, biological treatments, new adsorptive materials, zero‐valent metals, among others. Despite this large number of studies, none were found to be dedicated to testing the feasibility of monometallic copper.…”

“…For example, although the allowed concentration of ATZ in drinking water is up to 2 μg L −1 16 in Brazil and up to 3 μg L −1 in the United States of America, 17 it is detected above these concentrations in drinking water supplies. 18 ATZ has thus been the target of many studies regarding the development of alternative treatment techniques, such as AOPs, [19][20][21][22][23] biological treatments, [24][25][26] new adsorptive materials, 27 zero-valent metals, 11,[28][29][30] among others. Despite this large number of studies, none were found to be dedicated to testing the feasibility of monometallic copper.…”