Adsorption, Bioavailability and Microbial Toxicity of Diclofenac in Agricultural Soil
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Adsorption, Bioavailability and Microbial Toxicity of Diclofenac in Agricultural Soil Jeya Prakathi1 · Biswanath Mahanty1 · Pema Lhamo1 Received: 9 April 2020 / Accepted: 25 July 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract Persistence and environmental implication of pharmaceuticals in agricultural soil is determined depending on adsorption, bioavailability and toxicity. This study aims to assess adsorption/partitioning behaviour of diclofenac (DCF) and its impact on microbial activity in four agricultural soils, differing in pH, organic carbon content, and cation exchange capacity. Results from batch studies suggests that soil/water partition coefficients of DCF are essentially nonlinear, i.e. depends on drug amount (p = 0.001), and positively correlated with soil organic carbon (p = 0.008). The adsorption data can effectively be modelled using Freundlich isotherm (regression coefficients between 0.84 and 0.90). In soil incubation studies, DCF could not be detected after 6 days of spiking (20 µg/g) in all soil types, including abiotic control. This suggests an interplay of combined biotic/abiotic process in DCF removal. Though microbial activity (based on tetrazolium reduction) declined with incubation time, but was not correlated with DCF exposure, particularly in soils rich in organic carbon. Keywords Agricultural soil · Diclofenac · Microbial activity · Organic carbon · Adsorption Non-steroidal anti-inflammatory drugs are among the most commonly used pharmaceuticals and personal care products from a global perspective (Valkhoff et al. 2013). Non-steroidal anti-inflammatory drugs, such as Diclofenac −(2-(2-(2,6-dichlorophenylamino) phenyl) acetic acid) are taken as painkillers and a major portion of unused or expired drugs along with excreted active metabolites are discharged into sewerage system. Diclofenac (DCF) present in the wastewater, however is not completely degraded in treatment facilities (Vergili et al. 2019) and released in effluents or sorb to sludge leading to contamination of different environmental matrices. Reclaimed wastewater containing residue of pharmaceuticals or active metabolites when utilized in agriculture, can contaminate soil and groundwater (Sathishkumar et al. 2020). DCF exposure in agricultural field can also be perceived through municipal biosolids application containing significant proportion of non-metabolized parent compounds, and therefore accumulate in the soil.
* Biswanath Mahanty [email protected] 1
Department of Biotechnology, Karunya Institute of Technology and Sciences, Karunya Nagar, Coimbatore 641 114, India
DCF exposure, though not directly from environmental media, has been the root cause of collapsed vulture populations across the Indian subcontinent (Green et al. 2004). Laboratory studies suggest phytotoxicity potential of diclofenac photo-transformation products at environmentally relevant concentration (Ali et al. 2019). Results from acute aquatic toxicity studies, though are not alarming, potential for long ter
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