TRACING CONTAMINANT PATHWAYS IN SOILS AND PLANTS FROM OIL AND GAS PRODUCED-WATER DUMPING IN THE PERMIAN BASIN, USA

Water co-produced with hydrocarbons is an abundant waste product of oil and gasproduction. The Permian Basin, which underlies parts of southern New Mexico and western Texas, is the highest oil and gas (OG) producing region in the United States, yielding large volumes of OG produced water with complex chemistries. We present our study of illegal releases (dumps) of OG wastewater, which occurred adjacent to well pads located on Bureau of Land Management (BLM) managed lands, and discuss the environmental health hazards posed by these releases on sensitive desert ecosystems. Soils at dump sites were broadly enriched with elements typically found in regional OG produced waters compared to control sites where no dumping was apparent. We documented statistically significant increases in the concentrations of water extractable major anions and cations [sodium (Na), chloride, sulfate, bromide, strontium (Sr), lithium, boron, barium, magnesium, and potassium in soil samples that appeared to be dump-affected (n=18) relative to control soil samples (n=15) at 5 study sites. In addition, we observed changes in water content, total carbon, specific conductance, trace elements concentrations, ²²⁸Ra and ²²⁶Ra activity, and ⁸⁷Sr/⁸⁶Sr ratios in response to dumping. Further, we found corresponding shifts in soil microbial communities to more salt- and hydrocarbon-tolerant taxa in response to these dumping events. We also investigated translocation of major and trace elements and ⁸⁷Sr/⁸⁶Sr from soil into the emergent portions of vegetation. Plant samples from 4 species (Artemisia filifolia, Gutierrezia sarothrae, Quercus havardii, and Yucca elata) were collected from dump-affected and control areas at one study site. Dump-affected plant tissues were enriched in some OG water constituents including Na and Sr and had ⁸⁷Sr/⁸⁶Sr signatures consistent with regional OG produced water. Based on our results, produced water dumping likely results in the transport of inorganic constituents from the aqueous phase into soils and in some cases, into local plants. These observations can also help build a conceptual model for responding to accidental releases of OG produced water as well as inform potential contaminant pathways during intentional reuse of OG produced water for crop irrigation.