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1. Compromised Water Quality in Colonias of Nueces County, TX: A Vicious Cycle

   Rowles III, L. S.; Hossain, A. H.; Lawler, D. F.; Kirisits, M. J.; Araiza, I.; Saleh, N. B. (October 2019, University of North Carolina Chapel Hill Water & Health Conference)

   Colonias are self-built neighborhoods of mostly low-income families that lack basic infrastructure. While some funding from the state government has built roads and provided electricity, water and sewage systems are still lacking for many of the estimated 400,000 colonias’ residents in Texas. Of those that do have tap water, the supply is either inadequate or of questionable quality. Some colonias residents have access only to off-the-grid water supplies, and residents collect their water from community wells, or, if fortunate, from a personal well. Many of these wells are self-built and therefore shallow. In Nueces County, the groundwater in several colonias has been reported to contain arsenic, while poor sanitation practices (i.e., self-built septic systems) and heavy rainfall events in the region compromise the microbial quality of the groundwater. The naturally occurring arsenic in the aquifer and microbial contaminants from flooding events mean that the only available drinking water source in these colonias is contaminated throughout the year. In this research, datasets on water quality in nine colonias in Nueces County were collected both in wet (after a major rain/flooding event) and dry (no significant rainfall for four weeks) periods. The water quality analyses included traditional microbial quality assessment (total coliforms, Escherichia coli, and heterotrophs), pH, hardness, total dissolved solids, and a suite of metals that are relevant to human health (e.g., arsenic and lead). Microbial community analyses also were completed on select samples to assess the shifts in microbial ecology between wet and dry periods. Results reveal that water quality varies based on environmental conditions and presents a serious risk to human health. Water sampled during the wet period had extensive microbial contamination with elevated heterotrophs and total coliforms, and E. coli was identified in some samples. In the dry period, water from a number of colonias exhibited elevated levels of arsenic (above United States Environmental Protection Agency’s Maximum Contaminant Level of 10 µg/L). This study is one of the first to systematically investigate water quality in Texas colonias, and the results highlight how water quality in these communities is compromised year-round, going between microbial contamination in wet events and arsenic contamination in dry events. 

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2. Toxic elements in benthic lacustrine sediments of Utah’s Great Salt Lake following a historic low in elevation

   https://doi.org/10.3389/fsoil.2024.1445792  

   Jung, Julie; Frantz, Carie M; Fernandez, Diego P; Werner, Michael S (September 2024, Frontiers in Soil Science)

   Terminal lakes (without outflow) retain elements and compounds that reach them through fluvial, point source or atmospheric deposition. If the lake sediment is exposed, some of these chemicals could become toxic dust particulates. The Great Salt Lake (GSL) in Utah is a terminal lake that experienced record-low lake elevation in 2021-22, exposing vast areas of playa. Here, we used inductively coupled plasma mass spectrometry to analyze the environmental chemistry of GSL shallow sediment during historic lows in spring, summer, and fall of 2021. Contaminants at the subsurface interface are most able to influence diffusion into the water column and uptake by benthic biota. We focused our analysis on copper, thallium, arsenic, mercury, lead, and zinc, which have been historically deposited in this region and are toxic when at high concentrations. We compared records of regional mining activity to understand the current contamination and assess relevant spatial and temporal gradients. We also used two different extraction methods (EPA 3050b and NH₄AcO at pH=7) that can distinguish “environmentally available” vs. tightly associated and less available fractions. We observed consistent concentration of copper across sites indicating a larger relative impact of atmospheric deposition, with some evidence indicating further impacts of point sources. Arsenic, on the other hand, is maintained at high levels in submerged sediments and is likely geologically- and fluvially- derived. Thallium and mercury fluctuate seasonally and correlate with lake elevation. Lead and zinc levels are relatively low in GSL sites compared with freshwater input sites, indicating the deep brine layer may sequester these heavy metals, preventing their release into the water column. Overall, the concentrations of most metals in GSL sediments have declined from historic highs. However, each contaminant has distinct sources, seasonality, mobility and transmission. Complete recovery (if possible) may require many more decades and individual remediation strategies. 

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3. Characterization of Chemical and Bacterial Concentrations in Floor Dust Samples in Southeast Texas Households

   https://doi.org/10.3390/ijerph182312399  

   Davis, Felica R.; Ali, Hanan H.; Rosenzweig, Jason A.; Vrinceanu, Daniel; Maruthi Sridhar, Balaji Bhaskar (December 2021, International Journal of Environmental Research and Public Health)

   Indoor dust can be a major source of heavy metals, nutrients, and bacterial contamination in residential environments and may cause serious health problems. The goal of this research is to characterize chemical and bacterial contaminants of indoor, settled house dust in the Houston Metropolitan region. To achieve this, a total of 31 indoor dust samples were collected, along with household survey data, which were subsequently analyzed for elemental and bacterial concentrations. Microscopic and geospatial analysis was conducted to characterize and map potential hotspots of contamination. Interestingly Cd, Cr, Cu, Pb, and Zn concentrations of all 31 indoor dust samples were significantly enriched and exceeded soil background concentrations. Furthermore, As, Cd, Pb, and Zn concentrations in the dust samples were significantly correlated to the enteric bacterial load concentrations. Human health assessment revealed that cancer risk values via ingestion for Cd, Cr, and Ni were greater than the acceptable range. Of our 31 dust sample isolates, three Gram-negative and 16 Gram-positive pathogenic bacteria were identified, capable of causing a wide range of diseases. Our results demonstrate that both chemical and bacterial characterization of indoor dust coupled with spatial mapping is essential to assess and monitor human and ecological health risks. 

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4. Presence and Plant Uptake of Heavy Metals in Tidal Marsh Wetland Soils

   https://doi.org/10.3389/fpubh.2022.821892  

   Chintapenta, Lathadevi K.; Ommanney, Katharine I.; Ozbay, Gulnihal (February 2022, Frontiers in Public Health)

   Marsh grasses have been used as efficient tools for phytoremediation and are known to play key roles in maintaining ecosystem functions by reducing the contamination of coastlines. This study was initiated to understand how human activities in wetlands can impact ion-heavy metal concentrations in relation to native and invasive marsh grasses. The study site, Blackbird Creek (BBC) is a tidal wetland that experiences agricultural, fishing, recreational, residential and other anthropogenic activities throughout the year. Heavy metals cadmium, arsenic, and lead in the soils and marsh grasses were monitored along with the ion compositions of soils. The main objective of this study was to understand if the marsh soils containing monotypic stands of native ( Spartina ) and non-native ( Phragmites ) vegetation display similar levels of heavy metals. Differences were observed in the concentrations of heavy metals at study sites with varying marsh vegetation types, and in soils containing vegetation and no vegetation. The soils with dense Spartina and Phragmites stands were anaerobic whereas soil at the boat ramp site was comparatively less anaerobic and also had increased levels of cadmium. Heavy metal concentrations in soil and Phragmites leaves were inversely correlated whereas they were positively correlated in Spartina sites. Electrical conductivity and pH levels in soil also showed increased cadmium and arsenic concentrations. These findings collectively infer that human activities and seasonal changes can increase soil complexities affecting the bioavailability of metals. 

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5. Long-Term Arsenic Sequestration in Biogenic Pyrite from Contaminated Groundwater: Insights from Field and Laboratory Studies

   https://doi.org/10.3390/min11050537  

   Fischer, Alicia; Saunders, James; Speetjens, Sara; Marks, Justin; Redwine, Jim; Rogers, Stephanie R.; Ojeda, Ann S.; Rahman, Md Mahfujur; Billor, Zeki M.; Lee, Ming-Kuo (May 2021, Minerals)

   null (Ed.)

   Pumping groundwater from arsenic (As)-contaminated aquifers exposes millions of people, especially those in developing countries, to high doses of the toxic contaminant. Previous studies have investigated cost-effective techniques to remove groundwater arsenic by stimulating sulfate-reducing bacteria (SRB) to form biogenic arsenian pyrite. This study intends to improve upon these past methods to demonstrate the effectiveness of SRB arsenic remediation at an industrial site in Florida. This study developed a ferrous sulfate and molasses mixture to sequester groundwater arsenic in arsenian pyrite over nine months. The optimal dosage of the remediating mixture consisted of 5 kg of ferrous sulfate, ~27 kg (60 lbs) of molasses, and ~1 kg (2 lbs) of fertilizer per 3785.4 L (1000 gallons) of water. The remediating mixture was injected into 11 wells hydrologically upgradient of the arsenic plume in an attempt to obtain full-scale remediation. Groundwater samples and precipitated biominerals were collected from June 2018 to March 2019. X-ray diffraction (XRD), X-ray fluorescence (XRF), electron microprobe (EMP), and scanning electron microscope (SEM) analyses determined that As has been sequestered mainly in the form of arsenian pyrite, which rapidly precipitated as euhedral crystals and spherical aggregates (framboids) 1–30 μm in diameter within two weeks of the injection. The analyses confirmed that the remediating mixture and injection scheme reduced As concentrations to near or below the site’s clean-up standard of 0.05 mg/L over the nine months. Moreover, the arsenian pyrite contained 0.03–0.89 weight percentage (wt%) of sequestered arsenic, with >80% of groundwater arsenic removed by SRB biomineralization. Considering these promising findings, the study is close to optimizing an affordable procedure for sequestrating dissolved As in industry settings. 

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