Adsorption kinetics of the herbicide safeners, benoxacor and furilazole, to activated carbon and agricultural soils.

Chloroacetamide herbicides, namely acetochlor and metolachlor, are common herbicides used on corn and soybean fields. Dichloroacetamide safeners, namely benoxacor and furilazole, are commonly used in formulations containing chloroacetamide herbicides. Extensive reports on adsorption of chloroacetamide herbicides are available, yet little information exists regarding adsorption potential of co-applied safeners. Herein, the adsorption and desorption characteristics of selected herbicide safeners to granular activated carbon (GAC) and in agricultural soils are reported. Further, soil column studies were performed to understand the leaching behaviour of the herbicide Dual II Magnum. Equilibrium sorption experiments of safeners to three agricultural soils and one GAC showed that adsorption was best fitted by the Freundlich isotherm. The Freundlich adsorption constant, Kf, for benoxacor and furilazole sorption onto three agricultural soils ranged from 0.1 to 0.27 and 0.1 to 0.13 (mg/g) × (mg/L)ˆ(1/n), respectively. The Kf for benoxacor and furilazole to GAC was 6.4 and 3.4 (mg/g) × (mg/L)ˆ(1/n), respectively, suggesting more favorable sorption of benoxacor to GAC than furilazole to GAC. The sorption to soils was reversible as almost 40%-90% of both safeners was desorbed from three soils. These results were validated in four replicated soil column studies, where S-metolachlor was shown to leach similarly to the safener benoxacor, originating from the herbicide formulation. The leaching of S-metolachlor and benoxacor was influenced by soil texture. Cumulatively, these results show that safeners will move through the environment to surface waters similarly to the active ingredients in herbicides, but may be removed during drinking water treatment via GAC.

Solubility, partitioning, oxidation and photodegradation of dichloroacetamide herbicide safeners, benoxacor and furilazole.

Approximately 242 million kg of herbicides are applied in the United States (US) annually. While herbicides prevent the growth of weeds, they can damage crops resulting in so called "herbicide injury." To increase herbicidal tolerance of crops, herbicide safeners are commonly added to formulations. Herbicidal safeners are labeled as inert ingredients in herbicide formulations and typically minimal fate and transport information is available. The objective of this study is to experimentally derive the aqueous solubility, octanol-water partition coefficient, and photo-degradation and permanganate oxidation of two dichloroacetamide safeners, benoxacor and furilazole. These results can be used to understand the environmental chemodynamics of these compounds and their degradation via common drinking water treatment systems containing permanganate. The aqueous solubility of benoxacor and furilazole was 22 and 235 mg L-1 respectively while the estimated solubility from EPI Suite was 102.7 and 255 mg L-1 respectively. The log octanol-water partition coefficient of benoxacor and furilazole was 2.23 and 1.96 respectively. The selected safeners were not photodegradable to any great extent. Both benoxacor and furilazole oxidation were found to be second order with respect to initial KMnO4 concentrations. The results of this study can be used to predict distribution of safeners after application in agricultural fields and aid in the design of treatment systems.

Whole community transcriptome of a sequencing batch reactor transforming 2,4-dinitroanisole (DNAN) and 3-nitro-1,2,4-triazol-5-one (NTO).

Two sequencing batch reactors (SBRs) were run to bio-mineralize 2,4-dinitroanisole (DNAN) and 3-nitro-1,2,4-triazol-5-one (NTO) in lab scale settings. The reactors were shown to reproducibly biotransform these munitions under aerobic and anaerobic conditions during the operations of these SBRs. Complete removal (100% biotransformation) of DNAN (initially 17.7 ± 5.4 mg L-1) and NTO (initially 15.0 ± 7.1 mg L-1) was observed in an anaerobic SBR when Luria-Bertani (LB) broth was present. In contrast, an aerobic SBR degraded only 58 ± 22% of DNAN (initially 19.7 ± 6.2 mg L-1) and 45 ± 24% of NTO (initially 9.7 ± 6.3 mg L-1) when either LB or glucose was also added indicating that anaerobic conditions are more favorable for biotransformation of these munitions. Transcriptomic analysis of the DNAN and NTO degrading anaerobic SBR revealed upregulation of a putative nitroreductase, hydroxylaminophenol mutases, 4-hydroxylphenyl acetate associated genes, and quinone oxioreductases. Major Bacterial populations included Bacteroidales, Campylobacterales, Enterobacteriales, Pseudomonadales, Burkholderiales and Clostridiales. Results from this study can be used to inform investigation of munition degrading organisms and the functional genes responsible.

Transport and attenuation of Salmonella enterica, fecal indicator bacteria and a poultry litter marker gene are correlated in soil columns.

Millions of tons of fecal-contaminated poultry litter are applied to U.S. agricultural fields annually. Precipitation and irrigation facilitate transport of fecal-derived pathogens and fecal indicator bacteria (FIB) to groundwater. The goal of this study was to compare transport of pathogens, FIB, and a microbial source tracking marker gene for poultry litter (LA35) in a simulated soil-to-groundwater system. Nine laboratory soil columns containing four different soil types were used to evaluate microbial transport to groundwater via infiltration. Quantitative polymerase chain reaction was used to monitor Salmonella enterica Typhimurium, Escherichia coli, Enterococcus spp., Brevibacterium sp. LA35 and Bacteroidales leached from soil columns inoculated with poultry litter. S. enterica was correlated with LA35 poultry litter marker gene and FIB concentrations in column soils containing organic matter, but not in acid washed sands. In contrast, S. enterica was found to correlate with LA35 and FIB in the leachate from columns containing sand, but not with leachate from organic soil columns. The majority of recovered DNA was found in leachate of predominately sandy soil columns, and in the soil of loamy columns. At least 90% of the DNA retained in soils for each microbial target was found in the top 3cm of the column. These studies suggest that poultry litter associated pathogens and FIB are rapidly released from litter, but are influenced by complex attenuation mechanisms during infiltration, including soil type. This study advances our understanding of the potential for subsurface transport of poultry litter associated pathogens and FIB, and support the use of the LA35 marker gene for evaluating poultry litter impacts on groundwater.