The production of oil and gas (OG) results in large volumes of co-produced wastewaters that require proper disposal. One such disposal method is transportation to a wastewater management facility. Due to the complex chemistries of OG wastewaters, this transportation process poses unknown environmental health risks, particularly in the case of accidental or intentional releases. Starting in November 2017, over 39 illegal releases, or dumps, of OG wastewater were identified in southeastern New Mexico (within the Permian Basin), which resulted in ~4,000 barrels of drilling and production wastewaters being released onto desert soils. To evaluate the environmental health impacts of these releases, we analyzed changes in soil geochemistry and microbial communities. We compared soils collected from within the OG wastewater dump zones to unaffected soils (controls) collected from the same site. Soils were water extracted (1:1), with cations and anions analyzed using inductively coupled plasma-optical emission spectroscopy (ICP-OES) and ion chromatography, respectively. For microbial community analyses, soil DNA was extracted, and phylogenetic composition was captured using Illumina 16S iTag sequencing. Sequences were aligned to a non-redundant database and assigned to operational taxonomic units (OTUs) based on a 97% similarity cutoff. Downstream bioinformatics analysis assessed community structure and composition.
Results/Conclusions
Across all dump sites, significantly elevated Na, Cl, Br, Sr, and low concentrations of Ba, were observed. Microbial community analysis revealed that communities in dump soils had significantly lower alpha diversity compared to control soils, with an average 4,917 observed OTUs compared to an average 6,947 OTUs, respectively. Subjecting a weighted UniFrac distance matrix to a permutational analysis of variance (PERMANOVA) revealed significant variation between dump and control soil community structure. Using a non-metric multidimensional scaling (NMDS) ordination to visualize community differences, microbial communities from control soils showed distinct clustering away from the more widely distributed communities from dump affected soils. Soil geochemical variables such as elevated Na, Cl, and % Carbon strongly (and significantly) co-occurred with dump microbial communities, while Al, Fe, and Si co-occurred with control community clustering. Differential abundance analyses showed significant shifts towards halotolerant, halophilic, aerotolerant, and anaerobic microorganisms in dump soils, including an increased abundance of Halanaerobiaeota and Deferribacteres phyla. Further work will assess potential microbial community functions, e.g., hydrocarbon degradation, affected by OG wastewater inputs through metagenomic prediction of reconstructed 16S rRNA sequences. This study elucidates the role of microorganisms as biological markers for, and their potential to naturally attenuate, OG wastewater releases.