IMPROVING WATER QUALITY IN AGRICULTURAL WATERSHEDS UNDERLAIN BY CLAYPAN AND RESTRICTIVE LAYER SOILS
Location: Cropping Systems and Water Quality Research
Title: Sulfamethazine sorption to soil: vegetative management, pH, and dissolved organic matter effects
| Chu, Bei - |
| Goyne, Keith - |
| Anderson, Stephen - |
| Lin, Chung Ho - |
Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 7, 2013
Publication Date: N/A
Interpretive Summary: Veterinary antibiotics (VAs) are commonly used in livestock feed to prevent disease and enhance weight gain. These VAs can then be introduced into the soil environment when animal manures are land applied as crop fertilizer or for waste disposal. Environmental concerns associated with VA contamination of soil include toxic effects to bacteria and potential development of antibiotic resistance genes. VAs may be also transported by surface runoff to streams or lakes where their presence may be toxic to existing bacteria. Of additional concern is the observation that some VAs can be taken up by vegetable crops produced on manure-amended soils, thereby resulting in VA entry into the food chain. Thus, understanding the fate of VAs in the soil environment is important to understanding their potential environmental impacts and for assessing the effectiveness of practices that can mitigate their off-site transport. Vegetative buffers are one example of a practice that has been shown to reduce VA loss in surface runoff. The objectives of this research were to investigate the effect of three soils with different vegetative management on the sorption intensity of the VA, sulfamethazine (SMZ). Sorption is the term used to describe the binding of a compound to the soil by chemical and physical processes. The results showed that the organic matter content and soil pH were the most important properties affecting SMZ sorption. Soils collected from grass buffers or tree-grass buffers tended to have greater organic matter than cropped soils, resulting in increased SMZ sorption. Sorption of SMZ decreased with increasing soil pH. The presence of dissolved organic matter derived from poultry litter resulted in slightly less adsorption compared to soils without dissolved organic matter. Overall, these results showed that vegetative buffers create soil conditions that can enhance the binding of SMZ and impede the transport of SMZ by surface runoff. This research will benefit land management agencies and growers by providing evidence to support the use of vegetative buffers as a best management practice for mitigating VA transport from treated fields.
Elucidating veterinary antibiotic (VA) interactions with soil is important for assessing and mitigating possible environmental hazards. Objectives of this study were to investigate the effects of vegetative management, soil physical and chemical properties, and manure-derived dissolved organic matter (DOM) on sulfamethazine (SMZ) behavior in soil. Sorption experiments were performed over a range of SMZ concentrations (2.5 – 50 µmol/L) using soil samples from one of three vegetation treatments: agroforestry buffers strips (ABS); grass buffer strips (GBS); and row crops (RC). Results show that sorption isotherms are well fitted by the Freundlich isotherm model (log Kf = -0.04 to 0.78 and N = 0.76 to 1.02). Further investigation of solid-to-solution partition coefficients (Kd) demonstrated that vegetative management significantly (p < 0.01) influences SMZ sorption (ABS > GBS > RC). Multiple linear regression analyses indicate that organic carbon (OC) content, pH, initial SMZ concentration, and clay content were important properties controlling SMZ sorption. Study of the two most contrasting soils revealed that increasing solution pH from 6.0 to 7.5 reduced SMZ sorption to the Armstrong GBS soil, but little pH effect was observed for the Huntington GBS soil containing nearly 50% kaolinite in the clay fraction. The presence of DOM (150 mg C/L) had little effect on Freundlich model parameters; however, DOM addition resulted in slightly lower SMZ Kd values overall, presumably due to competitive interactions for sorption sites. Results support the use of vegetative buffers to mitigate VA loss from agroecosystems, provide guidance for properly managing VBS to increase SMZ sorption, and enhance understanding of SMZ sorption in soils.