Illegal dumping of oil and gas wastewater alters arid soil microbial communities.

The Permian Basin, underlying southeast New Mexico and west Texas, is one of the most productive oil and gas (OG) provinces in the United States. Oil and gas production yields large volumes of wastewater with complex chemistries, and the environmental health risks posed by these OG wastewaters on sensitive desert ecosystems are poorly understood. Starting in November 2017, 39 illegal dumps, as defined by federal and state regulations, of OG wastewater were identified in southeastern New Mexico, releasing ~600,000 L of fluid onto dryland soils. To evaluate the impacts of these releases, we analyzed changes in soil geochemistry and microbial community composition by comparing soils from within OG wastewater dump-affected samples to unaffected zones. We observed significant changes in soil geochemistry for all dump-affected compared with control samples, reflecting the residual salts and hydrocarbons from the OG-wastewater release (e.g., enriched in sodium, chloride, and bromide). Microbial community structure significantly (P < 0.01) differed between dump and control zones, with soils from dump areas having significantly (P < 0.01) lower alpha diversity and differences in phylogenetic composition. Dump-affected soil samples showed an increase in halophilic and halotolerant taxa, including members of the Marinobacteraceae, Halomonadaceae, and Halobacteroidaceae, suggesting that the high salinity of the dumped OG wastewater was exerting a strong selective pressure on microbial community structure. Taxa with high similarity to known hydrocarbon-degrading organisms were also detected in the dump-affected soil samples. Overall, this study demonstrates the potential for OG wastewater exposure to change the geochemistry and microbial community dynamics of arid soils.IMPORTANCEThe long-term environmental health impacts resulting from releases of oil and gas (OG) wastewater, typically brines with varying compositions of ions, hydrocarbons, and other constituents, are understudied. This is especially true for sensitive desert ecosystems, where soil microbes are key primary producers and drivers of nutrient cycling. We found that releases of OG wastewater can lead to shifts in microbial community composition and function toward salt- and hydrocarbon-tolerant taxa that are not typically found in desert soils, thus altering the impacted dryland soil ecosystem. Loss of key microbial taxa, such as those that catalyze organic carbon cycling, increase arid soil fertility, promote plant health, and affect soil moisture retention, could result in cascading effects across the sensitive desert ecosystem. By characterizing environmental changes due to releases of OG wastewater to soils overlying the Permian Basin, we gain further insights into how OG wastewater may alter dryland soil microbial functions and ecosystems.

Advocating the Use of Bayesian Network in Analyzing the Modes of Occurrence of Elements in Coal.

Modes of occurrence of elements in coal are important because they can be used not only to understand the origin of inorganic components in coal but also to determine the impact on the environment and human health and the deposition process of coal seams as well. Statistical analysis is one of the commonly used indirect methods used to analyze the modes of occurrence of elements in coal, among which hierarchical clustering is widely used. However, hierarchical clustering may lead to misleading results due to its limitation that it focuses on the clusters of elements rather than a single element. To tackle this issue, we use the first part of a well-known Bayesian network structure learning algorithm, i.e., Peter-Clark (PC) algorithm, to explore the relationships of the coal elemental data and then infer modes of occurrence of elements in coal. A data set containing 95 Late Paleozoic coal samples from the Datanhao and Adaohai mines in Inner Mongolia, China, is used for the performance evaluation. Analytical results show that many instructive and surprising insights can be concluded from the first part of the PC algorithm. Compared with the hierarchical clustering algorithm, the first part of the PC algorithm demonstrates superiority in analyzing the modes of occurrence of elements in coal.

Datasets associated with the characterization of produced water and Pecos River water in the Permian Basin, the United States.

The data in this report are associated with "Characterization of Produced Water and Surrounding Surface Water in the Permian Basin, the United States" (Jiang et al. 2022) and include raw data on produced water (PW) quality and Pecos River water quality in the Permian Basin, which is one of the major oil and gas producing areas in the U.S. The data include 46 samples for PW and 10 samples for Pecos River water. The data include wet chemistry, mineral salts, metals, oil and grease, volatile and semi-volatile organic compounds, radionuclides, ammonia, hydraulic fracturing additives, and per- and polyfluoroalkyl substances. The PW samples were collected from five different locations in the Permian Basin. Twenty-four of the PW samples and the ten Pecos River samples were analyzed by the authors. The information for the rest of PW samples (22 samples) was provided by industrial collaborators in the Permian Basin. Statistical analyses were performed on the combined data to obtain Mean, Max, Min, 25th percentile, 50th percentile, and 75th percentile of each analyte.

Dissolved organic matter within oil and gas associated wastewaters from U.S. unconventional petroleum plays: Comparisons and consequences for disposal and reuse.

Wastewater generated during petroleum extraction (produced water) may contain high concentrations of dissolved organics due to their intimate association with organic-rich source rocks, expelled petroleum, and organic additives to fluids used for hydraulic fracturing of unconventional (e.g., shale) reservoirs. Dissolved organic matter (DOM) within produced water represents a challenge for treatment prior to beneficial reuse. High salinities characteristic of produced water, often 10× greater than seawater, coupled to the complex DOM ensemble create analytical obstacles with typical methods. Excitation-emission matrix spectroscopy (EEMS) can rapidly characterize the fluorescent component of DOM with little impact from matrix effects. We applied EEMS to evaluate DOM composition in 18 produced water samples from six North American unconventional petroleum plays. Represented reservoirs include the Eagle Ford Shale (Gulf Coast Basin), Wolfcamp/Cline Shales (Permian Basin), Marcellus Shale and Utica/Point Pleasant (Appalachian Basin), Niobrara Chalk (Denver-Julesburg Basin), and the Bakken Formation (Williston Basin). Results indicate that the relative chromophoric DOM composition in unconventional produced water may distinguish different lithologies, thermal maturity of resource types (e.g., heavy oil vs. dry gas), and fracturing fluid compositions, but is generally insensitive to salinity and DOM concentration. These results are discussed with perspective toward DOM influence on geochemical processes and the potential for targeted organic compound treatment for the reuse of produced water.

Characterization of produced water and surrounding surface water in the Permian Basin, the United States.

A thorough understanding of produced water (PW) quality is critical to advance the knowledge and tools for effective PW management, treatment, risk assessment, and feasibility for beneficial reuse outside the oil and gas industry. This study provides the first step to better understand PW quality to develop beneficial reuse programs that are protective of human health and the environment. In total, 46 PW samples from unconventional operations in the Permian Basin and ten surface water samples from the Pecos River in New Mexico were collected for quantitative target analyses of more than 300 constituents. Water quality analyses of Pecos River samples could provide context and baseline information for the potential discharge and reuse of treated PW in this area. Temporal PW and river water quality changes were monitored for eight months in 2020. PW samples had total dissolved solids (TDS) concentrations ranging from 100,800-201,500 mg/L. Various mineral salts, metals, oil and grease, volatile and semi-volatile organic compounds, radionuclides, ammonia, hydraulic fracturing additives, and per- and polyfluoroalkyl substances were detected at different concentrations. Chemical characterization of organic compounds found in Pecos River water showed no evidence of PW origin. Isometric log-ratio Na-Cl-Br analysis showed the salinity in the Pecos River samples appeared to be linked to an increase in natural shallow brine inputs. This study outlines baseline analytical information to advance PW research by describing PW and surrounding surface water quality in the Permian Basin that will assist in determining management strategies, treatment methods, potential beneficial reuse applications, and potential environmental impacts specific to intended beneficial use of treated PW.

Insights on Geochemical, Isotopic, and Volumetric Compositions of Produced Water from Hydraulically Fractured Williston Basin Oil Wells.

Tracing produced water origins from wells hydraulically fractured with freshwater-based fluids is sometimes predicated on assumptions that (1) each geological formation contains compositionally unique brine and (2) produced water from recently hydraulically fractured wells resembles fresher meteoric water more so than produced water from older wells. These assumptions are not valid in Williston Basin oil wells sampled in this study. Although distinct average 228Ra/226Ra ratios were found in water produced from the Bakken and Three Forks Formations, average δ2H, δ18O, specific gravity, and conductivity were similar but exhibited significant variability across five oil fields within each formation. Furthermore, initial produced water ("flowback") was operationally defined based on the presence of glycol ether compounds and water from wells that had produced <56% of the amount of fluids injected and sampled within 160 days of fracturing. Flowback unexpectedly exhibited higher temperature, specific gravity, conductivity, δ2H, and δ18O, but lower oxidation-reduction potential and δ11B, relative to the wells thought to be producing formation brines (from wells with a produced-to-injected water ratio [PIWR] > 0.84 and sampled more than 316 days after fracturing). As such, establishing an overall geochemical and isotopic signature of produced water compositions based solely on chemical similarity to meteoric water and formation without the consideration of well treatments, well completion depth, or lateral location across the basin could be misleading if these signatures are assumed to be applicable across the entire basin. These findings have implications for using produced water compositions to understand the interbasin fluid flow and trace sources of hydraulic fracturing fluids.

Geochemical and geophysical indicators of oil and gas wastewater can trace potential exposure pathways following releases to surface waters.

Releases of oil and gas (OG) wastewaters can have complex effects on stream-water quality and downstream organisms, due to sediment-water interactions and groundwater/surface water exchange. Previously, elevated concentrations of sodium (Na), chloride (Cl), barium (Ba), strontium (Sr), and lithium (Li), and trace hydrocarbons were determined to be key markers of OG wastewater releases when combined with Sr and radium (Ra) isotopic compositions. Here, we assessed the persistence of an OG wastewater spill in a creek in North Dakota using a combination of geochemical measurements and modeling, hydrologic analysis, and geophysical investigations. OG wastewater comprised 0.1 to 0.3% of the stream-water compositions at downstream sites in February and June 2015 but could not be quantified in 2016 and 2017. However, OG-wastewater markers persisted in sediments and pore water for 2.5 years after the spill and up to 7.2-km downstream from the spill site. Concentrations of OG wastewater constituents were highly variable depending on the hydrologic conditions. Electromagnetic measurements indicated substantially higher electrical conductivity under the bank adjacent to a seep 7.2 km downstream from the spill site. Geomorphic investigations revealed mobilization of sediment is an important contaminant transport process. Labile Ba, Ra, Sr, and ammonium (NH4) concentrations extracted from sediments indicated sediments are a long-term reservoir of these constituents, both in the creek and on the floodplain. Using the drivers of ecological effects identified at this intensively studied site we identified 41 watersheds across the North Dakota landscape that may be subject to similar episodic inputs from OG wastewater spills. Effects of contaminants released to the environment during OG waste management activities remain poorly understood; however, analyses of Ra and Sr isotopic compositions, as well as trace inorganic and organic compound concentrations at these sites in pore-water provide insights into potentials for animal and human exposures well outside source-remediation zones.

Utica Shale Play Oil and Gas Brines: Geochemistry and Factors Influencing Wastewater Management.

The Utica and Marcellus Shale Plays in the Appalachian Basin are the fourth and first largest natural gas producing plays in the United States, respectively. Hydrocarbon production generates large volumes of brine ("produced water") that must be disposed of, treated, or reused. Though Marcellus brines have been studied extensively, there are few studies from the Utica Shale Play. This study presents new brine chemical analyses from 16 Utica Shale Play wells in Ohio and Pennsylvania. Results from Na-Cl-Br systematics and stable and radiogenic isotopes suggest that the Utica Shale Play brines are likely residual pore water concentrated beyond halite saturation during the formation of the Ordovician Beekmantown evaporative sequence. The narrow range of chemistry for the Utica Shale Play produced waters (e.g., total dissolved solids = 214-283 g/L) over both time and space implies a consistent composition for disposal and reuse planning. The amount of salt produced annually from the Utica Shale Play is equivalent to 3.4% of the annual U.S. halite production. Utica Shale Play brines have radium activities 580 times the EPA maximum contaminant level and are supersaturated with respect to barite, indicating the potential for surface and aqueous radium hazards if not properly disposed of.

Methane and Benzene in Drinking-Water Wells Overlying the Eagle Ford, Fayetteville, and Haynesville Shale Hydrocarbon Production Areas.

Water wells (n = 116) overlying the Eagle Ford, Fayetteville, and Haynesville Shale hydrocarbon production areas were sampled for chemical, isotopic, and groundwater-age tracers to investigate the occurrence and sources of selected hydrocarbons in groundwater. Methane isotopes and hydrocarbon gas compositions indicate most of the methane in the wells was biogenic and produced by the CO2 reduction pathway, not from thermogenic shale gas. Two samples contained methane from the fermentation pathway that could be associated with hydrocarbon degradation based on their co-occurrence with hydrocarbons such as ethylbenzene and butane. Benzene was detected at low concentrations (<0.15 µg/L), but relatively high frequencies (2.4-13.3% of samples), in the study areas. Eight of nine samples containing benzene had groundwater ages >2500 years, indicating the benzene was from subsurface sources such as natural hydrocarbon migration or leaking hydrocarbon wells. One sample contained benzene that could be from a surface release associated with hydrocarbon production activities based on its age (10 ± 2.4 years) and proximity to hydrocarbon wells. Groundwater travel times inferred from the age-data indicate decades or longer may be needed to fully assess the effects of potential subsurface and surface releases of hydrocarbons on the wells.

Wastewater Disposal from Unconventional Oil and Gas Development Degrades Stream Quality at a West Virginia Injection Facility.

The development of unconventional oil and gas (UOG) resources has rapidly increased in recent years; however, the environmental impacts and risks are poorly understood. A single well can generate millions of liters of wastewater, representing a mixture of formation brine and injected hydraulic fracturing fluids. One of the most common methods for wastewater disposal is underground injection; we are assessing potential risks of this method through an intensive, interdisciplinary study at an injection disposal facility in West Virginia. In June 2014, waters collected downstream from the site had elevated specific conductance (416 µS/cm) and Na, Cl, Ba, Br, Sr, and Li concentrations, compared to upstream, background waters (conductivity, 74 µS/cm). Elevated TDS, a marker of UOG wastewater, provided an early indication of impacts in the stream. Wastewater inputs are also evident by changes in (87)Sr/(86)Sr in streamwater adjacent to the disposal facility. Sediments downstream from the facility were enriched in Ra and had high bioavailable Fe(III) concentrations relative to upstream sediments. Microbial communities in downstream sediments had lower diversity and shifts in composition. Although the hydrologic pathways were not able to be assessed, these data provide evidence demonstrating that activities at the disposal facility are impacting a nearby stream and altering the biogeochemistry of nearby ecosystems.

High Mercury Wet Deposition at a "Clean Air" Site in Puerto Rico.

Atmospheric mercury deposition measurements are rare in tropical latitudes. Here we report on seven years (April 2005 to April 2012, with gaps) of wet Hg deposition measurements at a tropical wet forest in the Luquillo Mountains, northeastern Puerto Rico, U.S. Despite receiving unpolluted air off the Atlantic Ocean from northeasterly trade winds, during two complete years the site averaged 27.9 µg m(-2) yr(-1) wet Hg deposition, or about 30% more than Florida and the Gulf Coast, the highest deposition areas within the U.S. These high Hg deposition rates are driven in part by high rainfall, which averaged 2855 mm yr(-1). The volume-weighted mean Hg concentration was 9.8 ng L(-1), and was highest during summer and lowest during the winter dry season. Rainout of Hg (decreasing concentration with increasing rainfall depth) was minimal. The high Hg deposition was not supported by gaseous oxidized mercury (GOM) at ground level, which remained near global background concentrations (<10 pg m(-3)). Rather, a strong positive correlation between Hg concentrations and the maximum height of rain detected within clouds (echo tops) suggests that droplets in high convective cloud tops scavenge GOM from above the mixing layer. The high wet Hg deposition at this "clean air" site suggests that other tropical areas may be hotspots for Hg deposition as well.

Hydraulic fracturing water use variability in the United States and potential environmental implications.

A U.S. map of water volumes used to hydraulically fracture oil and gas wells, 2011-2014Hydraulic fracturing water volumes differ regionally across the U.S.Discussion of variation in water use and potential environmental implications.

Gas emissions, minerals, and tars associated with three coal fires, Powder River Basin, USA.

Ground-based surveys of three coal fires and airborne surveys of two of the fires were conducted near Sheridan, Wyoming. The fires occur in natural outcrops and in abandoned mines, all containing Paleocene-age subbituminous coals. Diffuse (carbon dioxide (CO(2)) only) and vent (CO(2), carbon monoxide (CO), methane, hydrogen sulfide (H(2)S), and elemental mercury) emission estimates were made for each of the fires. Additionally, gas samples were collected for volatile organic compound (VOC) analysis and showed a large range in variation between vents. The fires produce locally dangerous levels of CO, CO(2), H(2)S, and benzene, among other gases. At one fire in an abandoned coal mine, trends in gas and tar composition followed a change in topography. Total CO(2) fluxes for the fires from airborne, ground-based, and rate of fire advancement estimates ranged from 0.9 to 780mg/s/m(2) and are comparable to other coal fires worldwide. Samples of tar and coal-fire minerals collected from the mouth of vents provided insight into the behavior and formation of the coal fires.

CO(2), CO, and Hg emissions from the Truman Shepherd and Ruth Mullins coal fires, eastern Kentucky, USA.

Carbon dioxide (CO(2)), carbon monoxide (CO), and mercury (Hg) emissions were quantified for two eastern Kentucky coal-seam fires, the Truman Shepherd fire in Floyd County and the Ruth Mullins fire in Perry County. This study is one of the first to estimate gas emissions from coal fires using field measurements at gas vents. The Truman Shepherd fire emissions are nearly 1400t CO(2)/yr and 16kg Hg/yr resulting from a coal combustion rate of 450-550t/yr. The sum of CO(2) emissions from seven vents at the Ruth Mullins fire is 726+/-72t/yr, suggesting that the fire is consuming about 250-280t coal/yr. Total Ruth Mullins fire CO and Hg emissions are estimated at 21+/-1.8t/yr and >840+/-170g/yr, respectively. The CO(2) emissions are environmentally significant, but low compared to coal-fired power plants; for example, 3.9x10(6)t CO(2)/yr for a 514-MW boiler in Kentucky. Using simple calculations, CO(2) and Hg emissions from coal-fires in the U.S. are estimated at 1.4x10(7)-2.9x10(8)t/yr and 0.58-11.5t/yr, respectively. This initial work indicates that coal fires may be an important source of CO(2), CO, Hg and other atmospheric constituents.

Mercury distribution in two Sierran forest and one desert sagebrush steppe ecosystems and the effects of fire.

Mercury (Hg) concentration, reservoir mass, and Hg reservoir size were determined for vegetation components, litter, and mineral soil for two Sierran forest sites and one desert sagebrush steppe site. Mercury was found to be held primarily in the mineral soil (maximum depth of 60 to 100 cm), which contained more than 90% of the total ecosystem reservoir. However, Hg in foliage, bark, and litter plays a more dominant role in Hg cycling than the mineral soil. Mercury partitioning into ecosystem components at the Sierran forest sites was similar to that observed for other US forest sites. Vegetation and litter Hg reservoirs were significantly smaller in the sagebrush steppe system because of lower biomass. Data collected from these ecosystems after wildfire and prescribed burns showed a significant decrease in the Hg pool from certain reservoirs. No loss from mineral soil was observed for the study areas but data from fire severity points suggested that Hg in the upper few millimeters of surface soil may be volatilized due to exposure to elevated temperatures. Comparison of data from burned and unburned plots suggested that the only significant source of atmospheric Hg from the prescribed burn was combustion of litter. Differences in unburned versus burned Hg reservoirs at the forest wildfire site demonstrated that drastic reduction in the litter and above ground live biomass Hg reservoirs after burning had occurred. Sagebrush and litter were absent in the burned plots after a wildfire suggesting that both reservoirs were released during the fire. Mercury emissions due to fire from the forest prescribed burn, forest wildfire, and sagebrush steppe wildfire sites were roughly estimated at 2.0 to 5.1, 2.2 to 4.9, and 0.36+/-0.13 g ha(-1), respectively, with litter and vegetation being the most important sources.

Atmospheric mercury emissions and speciation at the sulphur bank mercury mine superfund site, Northern California.

One pathway for release of mercury (Hg) from naturally enriched sites is emission to the atmosphere. Elemental Hg, when emitted, will enter the global atmospheric pool. In contrast, if reactive gaseous Hg or Hg2+ (as HgCl2, HgBr2, or HgOH2) is formed, it will most likely be deposited locally. This study focused on the measurement of elemental Hg flux and reactive gaseous Hg concentrations at the Sulphur Bank Superfund Site, an area of natural Hg enrichment with anthropogenic disturbance and ongoing geothermal activity. Mean Hg emissions ranged from 14 to 11000 ng m(-2) h(-1), with the highest emissions from anthropogenically disturbed materials. Reactive gaseous Hg concentrations were the highest ever reported for a natural setting (0.3-76 ng m(-3)). Measured Hg fluxes were used within a Geographic Information System to estimate mercury releases to the atmosphere from the site. Results indicated approximately 17 kg of Hg y(-1) of is emitted to the atmosphere from the 3.8 km2 area, with half from mine waste, ore, and tailing piles and half from relatively undisturbed naturally enriched substrate.

Scaling of atmospheric mercury emissions from three naturally enriched areas: Flowery Peak, Nevada; Peavine Peak, Nevada; and Long Valley Caldera, California.

With the development of analytical capabilities that allow for almost real time measurement of mercury concentrations in air, the fluxes of mercury between environment compartments is being more carefully scrutinized. Recent advances have demonstrated that the mercury cycle is much more complicated than previously realized. This study quantified the mercury emissions from three areas with low levels of mercury enrichment associated with precious and base metal mineralization and recent volcanic/geothermal activity. Area emissions were calculated using Geographic Information System technology, and in situ derived mercury fluxes and those parameters found to statistically be dominant in controlling emissions. The most important controls on emission strengths were found to be geologic while environmental parameters such as light and temperature were found to drive the diel pattern typically observed for mercury emissions. Calculated area averaged emissions were 18.5, 10.0, and 13.6 ng/m2 h for the Flowery Peak, NV, Peavine Peak, NV, and Long Valley Caldera, CA areas, respectively. These emissions are an order of magnitude higher than values applied in global models for natural sources. This study, along with other recent work, demonstrates that natural sources may contribute more mercury than previously recognized to the atmospheric mercury pool.