Sorption of two classes of emerging contaminants by dissolved organic carbon from diverse sources

Nadia Carmosini, Purdue University

Abstract

In the past decade, diverse organic chemicals from industrial, agricultural, and commercial products have been identified as emerging contaminants (ECs) in the environment. Land disposal of biosolids from municipal wastewater treatment plants (WWTPs) and manure from confined animal feeding operations (CAFOs) is an exposure route for certain ECs. Among these are fluorotelomer alcohols (FTOHs) and amphoteric antimicrobials. Recent studies on these EC classes have reported a high affinity for dissolved organic carbon (DOC), raising concerns that DOC from biosolids, animal wastes, or soils may facilitate their global distribution by DOC-enhanced transport. However, direct measurements of DOC-water partition coefficients (Kdoc) with environmentally-relevant DOC materials are lacking. Therefore, K doc values were quantified for select FTOHs and the amphoteric antimicrobial ciprofloxacin (CIP) using standard humic materials, WWTP biosolids and effluent, beef lagoon effluent, and soils to evaluate the mechanisms and potential magnitude of facilitated transport by environmentally-relevant DOC. Measured log Kdoc values for a 10-carbon FTOH (8:2 FTOH) ranged from 2.00–3.97, which are 1–2 log units lower than estimated values, and slightly lower than measured OC-normalized sorption to soils. These Kdoc values result in potential increases in mobility of 8:2 FTOH of 1% to 50%. For CIP, sorption isotherms with standard DOC materials were nonlinear and well the Langmuir sorption model. Decreases in sorption with increasing pH are attributable to reductions in the fraction of the cationic CIP species, exemplifying the importance of sorption by cation exchange. CIP sorption by digested biosolids DOC was also non-linear but did not exhibit pH-dependence, suggesting the occurrence of additional unidentified binding processes. At CIP concentrations reported in biosolids (∼ 2 mg/L) and the DOC concentrations associated with the biosolids in this study (40 mg OC/L), the measured log K doc of ∼ 4 could potentially increase CIP mobility by ∼ 15%. Interaction of ECs and DOC with soil must also be considered when assessing mobility of ECs in the environment; however, the extent of FTOH and CIP interactions with environmentally-relevant DOC exemplified here warrants that DOC-facilitated transport should be included in assessments of the global distribution of these EC classes.

Degree

Ph.D.

Advisors

Lee, Purdue University.

Subject Area

Agricultural chemicals

COinS