Theme: 14. Emerging Contaminants

Topic Area: 14f. Microplastics, Pharmaceuticals, and Other Emerging Contaminants

Formatted Title:

Nontargeted Chemical Analysis for the Discovery of Dechlorinated Pesticide and Antibiotic Transformation Products Formed during Manure-Based Anaerobic Digestion

Background/Objectives:

A wide variety of organic chemicals are applied in agricultural systems for animal and crop growth including antibiotics, antifungals, and insect repellents. Many chemicals within these classes pose serious human and environmental health risks, and technologies to reduce their emission into the environment are needed. Anaerobic digestion is a biological process that converts organic materials (e.g., manure) into valuable biogas, and is considered a key component to enhancing agricultural sustainability. Anaerobic digestion may also be valuable as a technology for degrading agricultural chemicals prior to environmental release. While the removal of organic contaminants, in particular antibiotics, during anaerobic digestion has been investigated previously, little is known about the underlying degradation mechanisms and the formation of transformation products.

Approach/Activities:

Lab-scale anaerobic digestion batch reactors were prepared following the biochemical methane potential method with dairy manure and spiked with compounds individually and in mixtures. Digestion media samples were extracted using a modified QuEChERS method and analyzed using liquid chromatography high- resolution mass spectrometry to determine degradation kinetics. Electrospray ionization in full MS mode with data dependent MS/MS acquisition was combined with an automated nontargeted chemical analysis workflow to identify transformation products. Temporal trends were used to determine degradation pathways and mechanisms.

Results/Lessons Learned:

Out of the 20 total antibiotics and pesticides that were tested, nine compounds were persistent, while 11 compounds degraded. Forty-seven transformation products were identified through nontargeted and temporal trend analysis; their structures were elucidated through MS/MS scan comparisons. Of the 11 compounds that degraded, three degraded entirely through abiotic mechanisms, two degraded entirely through biotic mechanisms, and six degraded through combined biotic and abiotic mechanisms. The degradation mechanisms identified include dechlorination, ester and ether cleavages, amide and carbamide cleavages, among others. These results suggest that in addition to renewable energy generation, anaerobic digestion contributes to the degradation of chemical contaminants present in agricultural waste streams.

Melody Multra

Affiliation

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(Group 2, Poster Board #20) Nontargeted Chemical Analysis for the Discovery of Dechlorinated Pesticide and Antibiotic Transformation Products Formed during Manure-Based Anaerobic Digestion