Maximum Contaminant Level Research Articles

Fast oxidation and deep removal of As(III) by integrating metal–organic framework ZIF-67 and sulfite: Performance and mechanism

Elimination of As(III) from water has gotten more attention in comparison with As(V) due to its higher mobility and toxicity. In this work, we provide an effective method by integrating a cobalt-based metal–organic framework ZIF-67 and sulfite (S(IV)) to purify As(III)-laden water. The coupled oxidation with adsorption process (i.e., As(III) removal by ZIF-67/S(IV)) surpasses a divided preoxidation-adsorption process (i.e., As(V) removal by ZIF-67) for arsenic removal from the multi-component water containing various coexisting anions. Herein, the mechanism investigation corroborated that the S(IV) plays dual roles as a complexing ligand and a precursor of oxysulfur radicals. The enhanced As(III) removal is attributed to the S(IV) activation on the ZIF-67 surface via various reactions (e.g., surface complexation and intramolecular electron transfer), which not only generates SO4− radicals for rapid oxidation of As(III) to As(V), but also provides more adsorption sites for the immobilization of the oxidized product (As(V)). Furthermore, the combined process can rapidly treat arsenic in the realistic contaminated water from 242 to 7 μg L−1 within 15 min, directly meeting the provisional maximum contaminant level (<10 μg L−1). Overall, the proposed work may aid the rational design of S(IV) mediated oxidation-adsorption process to remove arsenic from a variety of contaminated waters.

The history of the Department of Occupational Hygiene of the Federal Scientific Center of Hygiene named after F.F. Erisman” of Rospotrebnadzor

The history of the creation of the Department of Occupational Hygiene of the Federal Scientific Center of Hygiene named after F.F. Erisman of Rospotrebnadzor dates back to 1942, when the subject of scientific research was devoted to the study of sanitary working conditions at defense industry enterprises and the development of personal protective equipment for workers. By 1950, the range of issues under study was expanded with initiation of the comprehensive clinical and hygienic studies in the mining, chemical industries, mechanical engineering and agriculture using hygienic, physiological, biochemical research methods, animal experiments. In 1960-1990, the research was carried out in areas including the study of working conditions, workers’ health and toxicological assessment of new substances in the chemical industry, study of the dust factor and occupational health issues in the coal and mining industries; study of the effects on the body of working physical factors (noise, vibration, ultrasound, magnetic fields) in industry and agriculture, study of working conditions, working and rest regimes with new technological processes and new forms of labour management. During the period of 1957-2001, employees of the Occupational Health Department developed 14 sanitary rules (SP) and sanitary rules and regulations (SanPiN), hygienic norms of infrasound and vibration in the workplace. Maximum permissible concentrations (MPC) in the air of the working area for 42 harmful substances, maximum permissible levels (MPC) of skin contamination of workers for 17 chemicals have been developed and approved, the toxicity of 35 different compounds has been studied. According to the results of the research, 45 candidate’s and 18 doctoral dissertations were defended. In the modern period, the accumulated experience of effective scientific activity of the Department of Occupational Hygiene has been mastered .and implemented by a new generation of researchers of the Department of Occupational Medicine of the Institute of Complex Hygiene Problems of the "Federal Research Center of Hygiene named after F.F. Erisman" of Rospotrebnadzor.

Gross Alpha-Particle Activity and High 226Ra Concentrations Do Not Correspond with High 210Po in the Atlantic and Gulf Coastal Plain Aquifers of the United States

210Po, which is of human-health concern based on lifetime ingestion cancer risk, is indirectly regulated in drinking water through the U.S. Environmental Protection Agency’s gross alpha-particle activity (GAPA) maximum contaminant level of 15 pCi/L (picocuries per liter). This regulation requires independent measurement of 226Ra for samples exceeding the GAPA screening level of 5 pCi/L. There is no such requirement for 210Po. Co-occurrence of 226Ra and 210Po, alpha-emitting 238U-decay-series progeny, might be helpful in locating high-210Po waters but is unverified. Relations among 210Po, 226Ra, and GAPA evaluated for samples from 257 public-supply wells from Coastal Plain aquifers showed that concentrations of 226Ra correlated with GAPA but neither correlated with 210Po concentrations. The highest concentrations of 226Ra and 210Po were found under differing geochemical conditions. The highest 226Ra occurred in low-pH oxidizing waters and in neutral-pH reducing waters, where geochemical conditions render Fe–Mn-hydroxide sorbents inefficient. 210Po was highest (10.1 pCi/L) in reducing waters with high pH (>7.5, which results from progressive cation exchange), where 226Ra was lowest─exchanged to clay minerals. Because 226Ra and 210Po did not co-occur, the GAPA screening might not be protective for 210Po. Independent 210Po analysis is prudent, especially where groundwater is reducing with high pH and low 226Ra concentrations.

Robust and tunable performance of a cell-free biosensor encapsulated in lipid vesicles.

Cell-free systems have enabled the development of genetically encoded biosensors to detect a range of environmental and biological targets. Encapsulation of these systems in synthetic membranes to form artificial cells can reintroduce features of the cellular membrane, including molecular containment and selective permeability, to modulate cell-free sensing capabilities. Here, we demonstrate robust and tunable performance of a transcriptionally regulated, cell-free riboswitch encapsulated in lipid membranes, allowing the detection of fluoride, an environmentally important molecule. Sensor response can be tuned by varying membrane composition, and encapsulation protects from sensor degradation, facilitating detection in real-world samples. These sensors can detect fluoride using two types of genetically encoded outputs, enabling detection of fluoride at the Environmental Protection Agency maximum contaminant level of 0.2millimolars. This work demonstrates the capacity of bilayer membranes to confer tunable permeability to encapsulated, genetically encoded sensors and establishes the feasibility of artificial cell platforms to detect environmentally relevant small molecules.

Assessment of Mercury Concentrations in Water and Fish Tissue Analysis in Kaw Lake, Oklahoma, 2022

The Kaw Nation has been collecting water, sediment, and fish samples from Kaw Lake and upper Arkansas River from 2007 to present to examine the concentrations of Mercury and other heavy metals to protect the health of the tribal members. Kaw Lake is in the North-Central part of Oklahoma. Kaw Lake is a permanent water body constructed in 1976 by the Army of Corps of Engineers. The Lake is consistently fed by the Arkansas River and other tributaries as runoff coming all the way from Colorado through Kansas to Kaw Lake of Oklahoma. The Lake has a surface area of 26.64 square miles (69 km2) and shoreline of 168 miles (270 km) with a total drainage area of 56,345 square miles (145,393 km2) and an average water depth of 8 meters. The water and fish samples were collected from 7 sites of Kaw Lake, once in a month and the fish samples once in a year during summertime, early July to end of July. The fish samples focused on 5 sport, predator, and bottom dwelling species of large consumable size, greater than 200 mm length and 560 grams weight. The five fish sampled were Catfish, White bass, Largemouth and Smallmouth bass, Black and White crappie. The fish and water samples were sent to Accurate Environmental Labs for detailed analysis. Predator species were analyzed as fillet and the bottom dwellings as a whole fish using EPA Method 7471A-M. Mercury from Water and Fish Tissue Samples were analyzed by Atomic Fluorescence Spectrometry. The laboratory analysis indicated that all the Mercury concentration in the fish samples except in Blue Catfish and Spotted Bass fall below the Maximum Contaminant Level (MCL) of 0.5 mg/kg.

Drinking water disparities and aluminum concentrations: Assessing socio-spatial dimensions across an urban landscape

The United States Environmental Protection Agency does not enforce a maximum contaminant level of Aluminum (Al) in treated drinking water and trace amounts are commonly found in household tap water. Al is known to impact the aesthetics of tap water, and research shows that exposure may have adverse impacts on human health. Socioeconomic status (SES) may play a role in Al exposure since some water treatment plants utilize “Alum” as an affordable treatment method, even though higher Al concentrations can result in finished drinking water. The objective of this study is to identify socio-spatial variations in concentrations of Al in household tap water across a highly diverse urban landscape. A total of 96 households in eastern Palm Beach County, Florida were randomly selected and tap water samples were collected from an unfiltered faucet and tested for Al. Al was above method detection limit in 56% of the samples analyzed, and 6% of the samples were above Florida’s secondary maximum contaminant level (concentrations ranged from 0.009 mg/L - 0.429 mg/L). Significant spatial clusters of higher Al concentrations in areas of lower SES were identified using local spatial autocorrelation (Getis-Ord Gi*). Maximum Likelihood of Spatial Lag and Spatial Weighted Least Squares HET regression models confirm a significant association between higher Al concentrations in tap water and lower SES. The findings of this study may be useful to water officials who aim to reduce levels of Al in tap water by prioritizing communities that experience the greatest socioeconomic deprivation.

Northwestern Kansas Well Water Contaminant Study

Kansas residents rely on well and aquifer water sources. These sources may contain several contaminants that can greatly affect the lives and health of Kansans. Testing well and aquifers is important for the health and well-being of our Kansas residents, specifically those residing in areas where Prairie Dog Creek and the alluvial plain surrounding it are the key water sources for large portions of Northwestern Kansas and Southwestern Nebraska. Therefore, the aim of this study is to sample water wells in the alluvial plain of Prairie Dog Creek in Norton and Phillips County, Kansas. Samples were shipped to the Kansas Health and Environment Lab (KHEL) laboratories for analysis. After receiving results from KHEL, we input data into ArcGIS to create maps of the following contaminants: Arsenic, Iron, Nitrate, Sulfate, and Uranium . All contaminants were evaluated against their known MCL (maximum contamination level). All residents were informed of their well’s contaminant results, which were put into a database that contains their well number, contamination results, and location.

Improvements in the reduction coagulation filtration process for hexavalent chromium treatment

AbstractReduction coagulation filtration using ferrous iron (Fe(II)‐RCF), or reduction filtration using stannous tin (Sn(II)‐RF), for the removal of hexavalent chromium (Cr(VI)) from drinking water represent attractive alternatives to ion exchange or reverse osmosis. With a new maximum contaminant level for Cr(VI) anticipated in California, this study sought to expand on previous research by applying Fe(II)‐RCF and Sn(II)‐RF to multiple groundwaters under a variety of reductant dose and reduction time scenarios. Four different granular filter media were also tested for removal of total chromium (Cr(T)) following Cr(VI) reduction to trivalent chromium (Cr(III)). Sodium hypochlorite, instead of aeration, was used to oxidize excess Fe(II) to Fe(III) prior to filtration, with minimal Cr(III) to Cr(VI) reoxidation. Sn(II)‐RF was also able to achieve Cr(T) and Cr(VI) treatment goals without dedicated reduction time prior to filtration. Results of this study were used to develop more up‐to‐date, feasibility‐level, 20‐year annualized cost estimates.

Sustainability of Regional Groundwater Quality in Response to Managed Aquifer Recharge

AbstractGrowing demands on water supply worldwide have resulted in aquifer overdraft in many regions, especially in alluvial basins under intensive irrigation. This further leads to serious deterioration of groundwater quality. Managed aquifer recharge (MAR) has been shown to mitigate groundwater overdraft, but whether MAR can actually stabilize or reverse the ongoing declines in regional groundwater quality caused by non‐point sources has not been demonstrated. This study was intended to address the question by investigating impacts of different MAR strategies on regional groundwater quality. A geostatistical model was first used to characterize a heterogeneous alluvial aquifer system in a portion of the Tulare Lake Basin. Three‐dimensional numerical models were then employed to simulate groundwater flow and mass transport. Next, MAR strategies were applied in locations with different geological conditions or joint with different irrigation activities, and their performances were evaluated. Results demonstrate the potential of significant, long‐term benefits for regional groundwater quality by applying strategic, high‐intensity recharge operations on geologically favorable subregions. Siting MAR above the incised valley fill (IVF) deposit, a near‐surface paleochannel containing unusually coarse, high‐conductivity hydrofacies, leads to more extensive improvement in the groundwater quality in terms of salinity due to significant vertical flow and lateral outward flow from the IVF. Overall, decades would be required to alleviate groundwater quality concerns in the studied 189 km2 region. The simulations indicate that the deep concentrations remain below the secondary maximum contaminant level as the solute mass migrates downward with the prominent contribution from the attenuation via dispersion and matrix diffusion.

Hydrochemical and geological controls on dissolved radium and radon in northwestern Algeria hydrothermal groundwaters

This study presents the results of the first investigation on natural occurrence of radium and radon in Algerian thermal water systems. Activity concentrations of Rn and Ra isotopes were measured in sixteen hydrothermal springs of northwestern Algeria. Samples displayed high activities, especially for 222Rn, 224Ra and 226Ra (up to 377 × 103 Bq/m3, 730 Bq/m3 and 4470 Bq/m3, respectively). Approximately, 50% of the investigated springs displayed activities of combined long-lived Ra (226Ra + 228Ra) in excess of the maximum contaminant level (MCL) of the WHO and EPA for drinking water. Factors controlling the distribution of radionuclides in the aquifer system are investigated. The observed correlation between Ra isotope and TDS suggests that adsorption/desorption is not the dominant process controlling the distribution of Ra in waters. Our results indicate that the excess SO42− limits the concentration of dissolved Ba2+ and thereby, the elevated Ra activities in these hydrothermal systems are not simply limited by co-precipitation with BaSO4 (barite). The data shows that Ra activities are likely dominated by the recoil process of parent isotopes in the aquifer solids. The minimal abundance of clay minerals and oxides in the aquifer, in addition to thermal activities in northwestern Algeria, significantly enhances the mobilization of Ra into waters.

Bottled water contaminant exposures and potential human effects

BackgroundBottled water (BW) consumption in the United States and globally has increased amidst heightened concern about environmental contaminant exposures and health risks in drinking water supplies, despite a paucity of directly comparable, environmentally-relevant contaminant exposure data for BW. This study provides insight into exposures and cumulative risks to human health from inorganic/organic/microbial contaminants in BW. MethodsBW from 30 total domestic US (23) and imported (7) sources, including purified tapwater (7) and spring water (23), were analyzed for 3 field parameters, 53 inorganics, 465 organics, 14 microbial metrics, and in vitro estrogen receptor (ER) bioactivity. Health-benchmark-weighted cumulative hazard indices and ratios of organic-contaminant in vitro exposure-activity cutoffs were assessed for detected regulated and unregulated inorganic and organic contaminants. Results48 inorganics and 45 organics were detected in sampled BW. No enforceable chemical quality standards were exceeded, but several inorganic and organic contaminants with maximum contaminant level goal(s) (MCLG) of zero (no known safe level of exposure to vulnerable sub-populations) were detected. Among these, arsenic, lead, and uranium were detected in 67 %, 17 %, and 57 % of BW, respectively, almost exclusively in spring-sourced samples not treated by advanced filtration. Organic MCLG exceedances included frequent detections of disinfection byproducts (DBP) in tapwater-sourced BW and sporadic detections of DBP and volatile organic chemicals in BW sourced from tapwater and springs. Precautionary health-based screening levels were exceeded frequently and attributed primarily to DBP in tapwater-sourced BW and co-occurring inorganic and organic contaminants in spring-sourced BW. ConclusionThe results indicate that simultaneous exposures to multiple drinking-water contaminants of potential human-health concern are common in BW. Improved understandings of human exposures based on more environmentally realistic and directly comparable point-of-use exposure characterizations, like this BW study, are essential to public health because drinking water is a biological necessity and, consequently, a high-vulnerability vector for human contaminant exposures.

Characteristics of groundwater microbial communities’ structure under the impact of elevated nitrate concentrations in north China plain

In groundwater environments, the interaction between microbial communities and the hydrogeochemical parameters have been investigated extensively in the past years. However, little is known whether the maximum contamination level (MCL) is a threshold value that dictates the microbial composition. In this study, we analyzed 10 groundwater samples for their nitrate, nitrite, COD and sulfate concentrations, and characterized their microbial compositions using 16 S rRNA based high-throughput sequencing methods. All the 10 samples had oxygen demands higher than the corresponding MCL of China (10 mg L−1); moreover, 4 out of 10 samples also had nitrate concentrations higher than the corresponding MCL, which indicated that the groundwater quality was negatively impacted by anthropogenic activities. Comparing the microbial composition of groundwater that had higher-than-MCL nitrate concentrations to those that had lower-than-MCL nitrate concentrations, no significant differences were detected in communities' richness and diversity. However, the non-metric multi-dimensional analysis suggested that the 4 groundwater samples whose nitrate concentration exceed MCL are distinctly different from those of the rest 6 samples, indicating that MCL does have a significant impact on microbial structures. Pearson's correlation analysis suggested that none of the four analyzed hydrochemical parameters had significant impact on microbial communities' richness and diversity; however, at the genus level, the correlation results suggested that JG30-KM-CM45, Sphingomonas and Rhodococcus are closely correlated with nitrate concentration. The findings of this study deepened our understanding with respect to the relationships between the environmental quality indices and the microbial compositions of groundwater.

Exposure to Inorganic Arsenic in Rice in Brazil: A Human Health Risk Assessment.

In certain populations, rice is the main source of exposure to inorganic arsenic (iAs), which is associated with cancer and non-cancer effects. Although rice is a staple food in Brazil, there have been few studies about the health risks for the Brazilian population. The objective of this study was to assess the risks of exposure to iAs from white rice and brown rice in Brazil, in terms of the carcinogenic and non-carcinogenic effects, and to propose measures to mitigate those risks. The incremental lifetime cancer risk (ILCR) and hazard quotient (HQ) were calculated in a probabilistic framework. The mean ILCR was 1.5 × 10-4 for white rice and 6.0 × 10-6 for brown rice. The HQ for white and brown rice was under 1. The ILCR for white and brown rice was high, even though the iAs concentration in rice is below the maximum contaminant level. The risk for brown rice consumption was lower, which was not expected. Various mitigation measures discussed in this report are estimated to reduce the risk from rice consumption by 5-67%. With the support of public policies, measures to reduce these risks for the Brazilian population would have a positive impact on public health.

Environmental impact and mechanical improvement of microbially induced calcium carbonate precipitation-treated coal fly ash–soil mixture

Reuse of coal fly ash (CFA) as construction materials is one of the sustainable methods for mitigating its environmental impacts. However, the potential leaching of heavy metals and the limited effect on mechanical improvement impede the reuse of CFA. The objective of this research was to investigate the effects of environmental impact and mechanical improvement of the microbially induced calcium carbonate (CaCO3) precipitation (MICP) process on the CFA–soil mixture. Two resources of CFA, named CFA1 and CFA2, were used. CFA1 is classified as off-specification fly ash, and CFA2 is classified as class F-type fly ash. Experimental results showed that the unconfined compressive stress (UCS) of MICP-treated soil increased significantly with the addition of CFA. The MICP-treated 3% CFA1–soil mixture obtained the highest UCS of 2200 kPa, which was much higher than that of the MICP-treated soil (798 kPa). The maximum UCS of the MICP-treated 3% CFA2–soil mixture was 1398 kPa. X-ray diffraction analysis indicated that the main mineral crystal pattern present in the MICP-treated samples was calcite. Scanning electron microscopy images revealed that the formed calcium carbonate worked as a bridge to connect soil particles together, attached to the surface of soil or located in the pore side of soil particles. In addition, the batch leaching test indicated that cadmium (Cd), copper (Cu), magnesium (Mg), nickel (Ni) and zinc (Zn) were detected in the MICP-treated soil. With the addition of CFA, there was no metal exceeding the maximum contaminant level from the MICP-treated CFA1–soil mixture.

Enhancement of per- and polyfluoroalkyl substances removal from water by pyrogenic carbons: Tailoring carbon surface chemistry and pore properties

Several countries, including the United States, plan to set an enforceable maximum contaminant level for certain per- and polyfluoroalkyl substances (PFAS) in drinking water. Among the available treatment options, sorption by pyrogenic carbonaceous sorbents (PCS) is a practical and effective approach to remove PFAS from water in pilot- and full-scale applications. The two most important properties of PCS, surface chemistry and pore structure, were tailored in this study to understand their importance in the sorption of various anionic shorter-chain and longer-chain PFAS. Brief thermal oxidation (post-pyrolysis air oxidation, PPAO) of PCS, including biochars, at a moderate temperature (400 °C) was used to increase specific surface area and nanoporosity. The sorption distribution ratio, KD, of individual PFAS after PPAO treatment increased by as much as three orders of magnitude compared to the unmodified PCS—more effectively so for longer-chain than shorter-chain compounds. Pore reaming plays a major role in the sorption enhancement and an ion-pair (PFAS-counterions) sorption mechanism is proposed. In addition, irreversible sorption of a quaternary ammonium cationic polymer, poly(dimethyldiallylammonium) chloride (pDADMAC), was employed to reverse the surface charge of biochar. Coating with pDADMAC increased PFAS sorption by a factor of 10–3000 predominantly by an anion-exchange mechanism. Sorption enhancement was more effective for the sulfonate than the carboxylate with the same perfluoro chain length. The results of this study are expected to inform the design of carbons with greater ability to remove PFAS from water, which are urgently needed for water facilities to comply with state and federal regulations.

A novel application of a geotechnical soil stabilization technology for improved delivery of remedial amendments

AbstractAccelerating the remediation of contaminants that have diffused into low‐permeability (low‐k) geologic units such as silts and clays is a key need for the groundwater remediation industry. Injection‐based remedial technologies are often ineffective because the injected amendments are more likely to influence transmissive media (sands and sandy silts) and generally do not penetrate low‐k units. While some emerging technologies are now being tested, they are often expensive or have other technical limitations (e.g., installation depth and rate of amendment emplacement). To address the problem of treating contaminants in low‐k media, a geotechnical technology called the “Grout Bomber” (Keller North America) was repurposed for an environmental application to emplace ~800 vertical “reaction columns” containing zero valent iron (ZVI), sand, and neat vegetable oil for the treatment of chlorinated volatile organic compounds (CVOCs) in lean clays and sandy clays. The reaction columns were closely‐spaced (2–3 ft apart) to greatly accelerate the back diffusion of CVOCs from the low‐k media to the reaction columns where contact with ZVI and vegetable oil promotes abiotic and biotic reductive dechlorination of CVOCs, respectively. Overall, 35 tons of ZVI were emplaced into the 5200 cubic yard (yd3) (~4000 m3) source zone during the project. Key benefits of this technology include rapid installation (average of 107 reaction columns per day), ease of remediation amendment mixing, consistent amendment dosing, and relatively low unit installation costs ($71 per cubic yard of treatment zone). It should be emphasized that this application of the Grout Bomber relies on diffusion of contaminants into the reaction columns from the surrounding low‐k media—a process that occurs slowly over years to decades. A planning‐level model showed that installation of closely spaced vertical reaction columns in a TCE‐laden clay unit reduced the time to achieve maximum contaminant levels from greater than 500 years to approximately 26 years. Groundwater monitoring confirmed the establishment of a concentration gradient between the reaction columns which promotes diffusion of CVOCs toward the reaction columns. The presence of dissolved acetylene and gaseous “higher coupling” products (&gt;C3) provide further evidence of ongoing abiotic reductive dechlorination within the reaction columns.

Evaluation of a water arsenic filter in a participatory intervention to reduce arsenic exposure in American Indian communities: The Strong Heart Water Study

Many rural populations, including American Indian communities, that use private wells from groundwater for their source of drinking and cooking water are disproportionately exposed to elevated levels of arsenic. However, programs aimed at reducing arsenic in American Indian communities are limited. The Strong Heart Water Study (SHWS) is a randomized controlled trial aimed at reducing arsenic exposure among private well users in American Indian Northern Great Plains communities. The community-led SHWS program installed point-of-use (POU) arsenic filters in the kitchen sink of households, and health promoters delivered arsenic health communication programs. In this study we evaluated the efficacy of these POU arsenic filters in removing arsenic during the two-year installation period. Participants were randomized into two arms. In the first arm households received a POU arsenic filter, and 3 calls promoting filter use (SHWS mobile health (mHealth) & filter arm). The second arm received the same filter and phone calls, and 3 in-person home visits and 3 Facebook messages (SHWS intensive arm) for program delivery. Temporal variability in water arsenic concentrations from the main kitchen faucet was also evaluated. A total of 283 water samples were collected from 50 households with private wells from groundwater (139 filter and 144 kitchen faucet samples). Ninety-three percent of households followed after baseline had filter faucet water arsenic concentrations below the arsenic maximum contaminant level of 10 μg/L at the final visit during our 2 year study period with no difference between study arms (98 % in the intensive arm vs. 94 % in the mHealth & filter arm). No significant temporal variation in kitchen arsenic concentration was observed over the study period (intraclass correlation coefficient = 0.99). This study demonstrates that POU arsenic filters installed for the community participatory SHWS program were effective in reducing water arsenic concentration in study households in both arms, even with delivery of the POU arsenic filter and mHealth program only. Furthermore, we observed limited temporal variability of water arsenic concentrations from kitchen faucet samples collected over time from private wells in our study setting.

Drinking water and health assessment in a Northern Arizona community

Arizona is a mineral rich state that relies on a mix of surface and ground water supplies for drinking water requirements. Small, rural water systems relying on groundwater frequently encounter elevated metal(loid) measures, particularly inorganic arsenic (As +3, +5). Such contaminant occurrences can be associated with adverse health outcomes including cancers. The Hopi Environmental Health Project examined drinking water quality and water consumption behaviors from 76 homes on Hopi lands over a four-year period. Water samples were analyzed for 28 elements and compared to US Environmental Protection Agengy (EPA) maximum contaminant levels (MCL). Only municipal/piped water had a mean arsenic concentration (11.01 µg/L) exceeding the MCL (10.0 µg/L). All other water types and elements occurred below MCL when detected. A lifetime cancer and hazard quotient associated with arsenic consumption through each water type was performed and piped/municipal water was found to carry the greatest risks (9.96 cases per 10,000 people). Results from this study showed the potential for multiple contaminants to be present in drinking water from Hopi lands and the need for further health assessment of routine exposure to low doses of contaminant mixtures through drinking water.

A Fully Integrated, Ready-to-Use Distance-Based Chemosensor for Visual Quantification of Multiple Heavy Metal Ions.

Point-of-care devices offering quantitative results with simple steps would allow great useability for untrained end-users. Here, we report a ready-to-use chemosensor integrating automatic sample metering, on-chip reaction, gravitational-magnetic separation, and a distance-based readout for visual quantification of multiple heavy metal ions. Deoxyribozymes (DNAzymes), probe-modified magnetic microparticles (MMPs), and polystyrene microparticles (PMPs) are preloaded into a microfluidic chip and freeze-dried. After the water sample is collected with automatic volume metering, the particles are resuspended, and the MMPs and PMPs hybridize with DNAzyme at its two termini, forming the "MMPs-DNAzyme-PMPs" structure. When target metal ions are present, the DNAzymes are cleaved, yielding an increased number of free PMPs. All on-chip reactions are controlled by stopping the liquid flow at capillary valves and bursting it with hand-controlled tilting. Using the chip with a gravitational-magnetic separator, the free PMPs are separated from "MMPs-DNAzyme-PMPs" and accumulate into the trapping channel with a nozzle, forming a visual bar with growing distances proportional to the concentration of target metal ions. The achieved limit of detection (LOD) values for Cu2+ (103.1 nM), Pb2+ (69.5 nM), and Ag+ (793.6 nM) are below the maximum contamination levels. High selectivity of 100-fold, 200-fold, and 20-fold against interference is obtained. Moreover, by integrating three identical channels in parallel, simultaneous detection of the above-mentioned heavy metal ions in fresh and tap water samples is also achieved with high accuracy. Together, this fully integrated and easily operated platform embodies excellent potential for rapid, on-site sensing by unskilled users.

Threonine Phosphorylation of an Electrochemical Peptide-Based Sensor to Achieve Improved Uranyl Ion Binding Affinity

We have successfully designed a uranyl ion (U(VI)-specific peptide and used it in the fabrication of an electrochemical sensor. The 12-amino acid peptide sequence, (n) DKDGDGYIpTAAE (c), originates from calmodulin, a Ca(II)-binding protein, and contains a phosphothreonine that enhances the sequence's affinity for U(VI) over Ca(II). The sensing mechanism of this U(VI) sensor is similar to other electrochemical peptide-based sensors, which relies on the change in the flexibility of the peptide probe upon interacting with the target. The sensor was systematically characterized using alternating current voltammetry (ACV) and cyclic voltammetry. Its limit of detection was 50 nM, which is lower than the United States Environmental Protection Agency maximum contaminant level for uranium. The signal saturation time was ~40 min. In addition, it showed minimal cross-reactivity when tested against nine different metal ions, including Ca(II), Mg(II), Pb(II), Hg(II), Cu(II), Fe(II), Zn(II), Cd(II), and Cr(VI). Its reusability and ability to function in diluted aquifer and drinking water samples were further confirmed and validated. The response of the sensor fabricated with the same peptide sequence but with a nonphosphorylated threonine was also analyzed, substantiating the positive effects of threonine phosphorylation on U(VI) binding. This study places emphasis on strategic utilization of non-standard amino acids in the design of metal ion-chelating peptides, which will further diversify the types of peptide recognition elements available for metal ion sensing applications.