Geology topics

Rebecca E. Travis

Publications and source records attributed to Rebecca E. Travis.

6 recordsLinked to original sources

USGS2024

Assessment of per- and polyfluoroalkyl substances in water resources of New Mexico, 2020–21

Per- and polyfluoroalkyl substances (PFAS) have been detected in public and private drinking-water wells, springs, and surface waters in New Mexico; however, the presence and distribution of PFAS in water resources across the State are not well characterized. From August 2020 to October 2021, the U.S. Geological Survey, in cooperation with the New Mexico Environment Department, collected water-quality samples from groundwater and surface-water sites throughout New Mexico. One hundred and seventeen groundwater wells were sampled from unconfined water-table aquifers for PFAS and a geochemical suite including major ions, trace elements, nutrients, dissolved organic carbon (DOC), stable isotopes of oxygen and hydrogen, tritium, and carbon-14 to provide context for groundwater age and geochemical evolution. Eighteen surface-water samples were analyzed for PFAS, and select samples were analyzed for wastewater tracers, major ions, trace elements, and DOC. Blanks and replicates indicated low bias and variability for PFAS, wastewater tracers, and geochemical compounds. Twenty-seven of the 117 groundwater sites had PFAS concentrations reported above the detection level, and there were no exceedances of the 2016 U.S. Environmental Protection Agency health advisory of 70 nanograms per liter (ng/L) perfluorooctanoic acid plus perfluorooctane sulfonic acid. Twenty-two sites were resampled and showed similar signatures, excluding some springs. Total PFAS concentrations ranged from 0.91 to 80.3 ng/L. The most frequently detected PFAS at groundwater sites were perfluorobutanesulfonic acid (PFBS; 11 sites), perfluoropentanoic acid (10 sites), and perfluorohexanoic acid (9 sites). Correlations were found between certain PFAS compounds that suggest similar sources. PFAS were also correlated with tritium, DOC, and nitrate, which indicated that a presence of anthropogenic compounds could in turn indicate a likelihood of PFAS occurrence. In addition, a cluster analysis showed that varying geochemical processes and sources of anthropogenic compounds likely contribute to the PFAS signature of each groundwater sample. Surface-water samples showed variable total PFAS concentrations ranging from 1.0 to 155.4 ng/L. Sites downstream from urban areas showed numerous PFAS detections. Some undeveloped areas where minimal PFAS detections would be expected had PFAS detections. Correlations between PFAS were found that suggested similar sources. Perfluoropentanoic acid and PFBS were the most frequently detected PFAS, and PFBS had the highest single concentration of 93 ng/L. Results of the study provide an overview of PFAS occurrences in the water resources of New Mexico along with geochemical context and are used to identify areas for further scientific investigations that could further characterize PFAS occurrences in New Mexico.

New Mexico↗

USGS2024

Temporal variability and sources of PFAS in the Rio Grande, New Mexico through an arid urban area using multiple tracers and high-frequency sampling

Per- and polyfluoroalkyl substances (PFAS) are ubiquitous in the environment but sources are not well defined for temporal and spatial aspects within an urban environment, and especially for an arid urban environment subject to seasonal short term high-intensity precipitation events. A focused diel sampling was conducted in the summer of 2021 to assess the temporal and spatial variability of PFAS in the Rio Grande near Albuquerque, New Mexico and showed an order of magnitude increase of PFAS as it flows through the Albuquerque urban area. Discrete samples were collected at two different locations on the Rio Grande in addition to wastewater treatment plant (WWTP) effluent that discharges directly to the Rio Grande between the sampling locations. Short-term high-intensity precipitation events occurred during the study period and mobilized PFAS from urban runoff. Dissolved organic matter composed of tryptophan-like organic substances and refined fuel and fuel byproducts, characteristic of an urban signature, were also related to the precipitation events. The PFAS in discharge from the WWTP was consistent over a 24-h period with slight differences in some compounds. Wastewater presence on the Rio Grande downstream of the WWTP was evidenced by a gadolinium anomaly as well as increases in several other trace elements, total dissolved nitrogen, and fluorescence indicators, in addition to PFAS. PFAS varied depending on source contribution, where urban runoff was associated with PFOA, PFOS, and PFBA, whereas PFHxA and PFPeA were associated with wastewater effluent. In addition, passive polar organic chemical integrative samplers (POCIS) using hydrophilic-lipid balance (HLB) sorption media were deployed for a month at two locations on the Rio Grande to assess longer term PFAS concentrations. The POCIS results show some compounds (PFPeA and PFHpA) were greater than the average concentration from discrete samples, whereas other compounds (PFHxA, PFOA, PFDA, and PFNA) were lower in the POCIS, and PFOS was very similar between the two. The POCIS did not detect PFBA, which may be related to the HLB media not performing well for short chain PFAS compounds. The results show promise for integrative samplers utilizing sorbent media. More detailed investigation of the spatial and temporal variability of water chemistry on the Rio Grande as it flows through Albuquerque could provide information applicable to urban areas worldwide.

New Mexico↗

USGS2023

Assessing Escherichia coli and microbial source tracking markers in the Rio Grande in the South Valley, Albuquerque, New Mexico, 2020–21

The Rio Grande, in southern Albuquerque, New Mexico, is a Clean Water Act Section 303(d) Category 5 impaired reach for Escherichia coli ( E. coli ). The reach is 5 miles in length, extending from Tijeras Arroyo south to the Isleta Pueblo boundary. An evaluation of E. coli and microbial source tracking markers (human-, canine-, and waterfowl-specific sources) was conducted by the U.S. Geological Survey to determine the extent and source of fecal bacteria within the impaired reach of the Rio Grande, primarily during the dry season (November through June) in 2020 and 2021. Samples were collected in the river cross section at three locations within each site and collected during both the dry season and the wet season, thereby providing data over a range of flow conditions to better understand the extent and source of fecal bacteria. Because fecal microorganisms may readily attach to sediments, riverbed material samples were also collected. During the dry season, E. coli concentrations in water were primarily detected below the New Mexico Surface Water Quality Standard of 410 colony forming units per 100 milliliters and mostly human and canine sources were detected. However, approximately 40 percent of the water samples exceeded the Isleta Pueblo water quality standard of 88 colony forming units per 100 milliliters. E. coli concentrations in bed material were detected at low concentrations, and the bed material was a sandy substrate, with little fine-grained material, a suitable habitat that would allow for bacterial growth during the dry season. Significant spatial and temporal differences, where p-values were less than 0.05, were found in water-quality samples for E. coli (seasonal) and the human tracker concentrations (between sites and within a cross section of a site). Given the lack of correlation between discharge and E. coli concentration and the human marker being most prevalent in the study area, the sources of E. coli in the dry season are likely nonpoint sources. The results from this study will help decision makers determine the efficacy of their best management practices and guide new practices to improve water quality in the reach.

New Mexico↗

USGS2022

Hydrogeology and groundwater quality in the San Agustin Basin, New Mexico, 1975–2019

This report describes the findings of a U.S. Geological Survey study, completed in cooperation with the Bureau of Land Management, focused on better understanding the present-day (1975–2019) hydrogeology and groundwater quality of the San Agustin Basin in west-central New Mexico to support sustainable groundwater resource management. The basin hosts a relatively undeveloped basin-fill and alluvium aquifer system and is topographically divided into east and west subbasins by the McClure Hills. Groundwater chemistry and groundwater elevation data were compiled, collected, and interpreted in the context of groundwater flow and quality. The analyses presented in this report consider groundwater chemistry data collected within the last decade (2010–19) and groundwater elevation data collected from 1975 through 2019 to provide insight into present-day conditions. Groundwater elevations show that groundwater typically moves from the highlands to the lowlands, with a prominent east to west regional trend. Groundwater elevations were lowest in the southwestern portion of the west subbasin, where estimated flow directions suggest underflow through the local highlands into the northern East Fork Gila River watershed, which is further supported by historical groundwater elevation data from the northern East Fork Gila River watershed. Gradual groundwater elevation gradients (about 2 feet per mile) near the east and west subbasin divide suggest that groundwater slowly flows from the east subbasin to the west subbasin. Quantitative analyses of groundwater chemistry data show that groundwater in both subbasins has similar chemical characteristics. A systematic east to west groundwater evolution in water chemistry was not observed despite evidenced subbasin connectivity. The absence of this pattern suggests that groundwater mixing is regionally prevalent, sediment reactivity is low and variable, and (or) recharge conditions are comparable in both subbasins. Groundwater chemistry was generally independent of aquifer type, suggesting that the aquifers are hydrologically well connected. Corrected carbon-14 groundwater age estimates in the basin ranged from 232 to 13,916 years before present with a median of 5,409 years. A wide range of groundwater ages is therefore present in the basin, with waters commonly being thousands of years old, thereby supporting generally slow regional groundwater movement. A component of relatively young groundwater, for which estimated ages could not be accurately computed, is also present in the basin, and it may commonly mix with older waters. The spatial distribution of categorical and quantitative groundwater ages indicates that most recharge likely occurs in the highlands through mountain-block recharge and as focused recharge within arroyos, although evidence of modern (1953 and after) groundwater was minimal at sampled sites. Median annual gradients (groundwater elevation change over time) indicate that most groundwater elevations in the lowlands changed little (−0.2 to 0.2 foot per year) from 1975 through 2019. Groundwater elevations in the highlands varied more annually, which is likely due to recharge from precipitation events. These more variable groundwater elevations in the highlands compared with the lowlands, along with groundwater ages, provide further evidence that most groundwater recharge takes place in the highlands, with minimal recharge in the lowlands. Median groundwater elevation change for all sites was −0.05 foot per year. Temporal consistency of lowland groundwater elevations suggests that regional groundwater dynamics have been more or less stable through time under current climate and development conditions, although median annual gradients indicate that groundwater elevations may have slightly declined on average between 1975 and 2019.

New Mexico↗

USGS2021

Utilizing multiple hydrogeologic and anthropogenic indicators to understand zones of groundwater contribution to water-supply wells near Kirtland Air Force Base Bulk Fuels Facility in southeast Albuquerque, New Mexico

In 1999, a jet-fuels release was discovered at the Bulk Fuels Facility on Kirtland Air Force Base, Albuquerque, New Mexico. Contaminants had reached the water table and migrated north-northeast toward water-supply wells. Monitoring wells were installed downgradient from the facility to determine the primary zones of groundwater production for water-supply wells and assess contaminant presence. The monitoring wells are screened within the Santa Fe Group aquifer system, which includes clay units, at depths as great as 445 meters below land surface, and were categorized as water table, shallow, middle, deep, and aquifer-test pumping wells. Water-supply wells are screened across multiple water-bearing units within the aquifer system. All wells were sampled for major ions, trace elements, nutrients, stable isotopes, dissolved gases, tritium, carbon isotopes, and chlorofluorocarbons. The deeper and water-supply wells have evidence of longer groundwater residence times, as much as thousands of years, and water from the shallower wells shows evidence of anthropogenic nutrient inputs. Aquifer recharge is derived from either the mountain front or seepage from the Rio Grande. Dissolved-gas data indicate that the middle, deep, and aquifer-test pumping, and water-supply wells have cooler recharge temperatures than the shallower wells. Inferred groundwater age varies by method but indicates that the deeper, aquifer-test pumping, and water-supply wells have older water, as much as 15,000 years before present. Results indicate that the water-supply wells draw primarily from the middle and deeper portions of the aquifer system below the clay units and have not been affected by the contaminant plume, although some data indicate a potential for modern water entering some of the deeper and water-supply wells.

New Mexico↗

USGS2021

Comparison of passive and pumped sampling methods for analysis of groundwater quality, Kirtland Air Force Base, Albuquerque, New Mexico, 2019

A plume of ethylene dibromide (EDB) dissolved in groundwater extends northeast from the Bulk Fuels Facility on Kirtland Air Force Base, New Mexico. The leading edge of the EDB plume is upgradient from several water-supply wells. In 2013, the U.S. Geological Survey (USGS), in cooperation with the Albuquerque Bernalillo County Water Utility Authority and the U.S. Air Force, installed four sentinel well nests and two aquifer-test pumping wells between the EDB plume and the water-supply wells to serve as an early warning if the plume travels toward the water-supply wells. Since 2015, the USGS has used submersible pumps to sample the sentinel wells quarterly. In February 2017, the USGS began using dual-membrane passive diffusion bag samplers for quarterly sampling in the wells. To ensure that the passive samplers are obtaining representative samples of the groundwater contaminants, the USGS, in cooperation with the U.S. Air Force, initiated a study in 2019 to compare results from pump sampling and passive samplers and to use vertical profiling to determine the optimal depth for passive sampler placement in the screened interval to better inform long-term monitoring of the site. Vertical profiling included deploying passive samplers throughout the submerged screened interval of four shallow sentinel wells. After retrieval of the passive samplers, pump samples were collected. The results of analyses of both types of samples were compared. Volatile organic compound results for this study were all below the raised reporting levels, which is a level five times the maximum concentration detected in a blank and determined by an in-depth quality assessment; therefore, this study focused on inorganic constituent results, including major ions, trace elements, and stable isotopes of water, to calculate the relative percent difference (RPD) between the pump and passive sampling method results as a way to determine where passive samplers would be best placed in each of the wells. Several analytes had an RPD of more than plus or minus 50 percent, and several analytes were not within the estimated variability for each sampling method. Additionally, the variability within each sampling method was quantified and compared. Factors that likely contributed to the lack of comparison between each sampling method included temporal variability, flow regime, volume of sample integrated through different aquifer intervals, and reduction/oxidation processes. RPD and method variability were used to determine the intervals within each well with the greatest agreement between sampling methods. Optimal sampling depths for each well were then correlated to the intervals where quarterly sampling has been occurring.

New Mexico↗