Molybdenum distributions and variability in drinking water from England and Wales

Nitrate-induced mobilization of trace elements in reduced groundwater environments

Groundwater is an essential source for drinking water production. Nitrate infiltration into groundwater due to over-fertilization can cause a potential risk for groundwater quality. Pyrite and other geogenic minerals can be oxidized and trace metals consequently released into water, e.g., nickel and uranium. To achieve a better understanding of the nitrate-induced mobilization of metals, this study investigated the release of antimony, arsenic, chromium, cobalt, molybdenum, uranium, and vanadium from three different reduced sediments after nitrate addition. The experiments were conducted as batch and soil column tests under oxygen-free conditions. In addition to the ORP, the pH value was a relevant driver for the metal mobilization due to pH dependent adsorption and ion exchange processes. Uranium concentrations in the water increased with increasing redox potential. Also, antimony and, to a lesser extent, molybdenum showed higher mobilization at higher ORP as well as at higher pH values. On the contrary, arsenic and cobalt was immobilized with increasing redox potential. Pourbaix diagrams demonstrated very complex species distributions even in synthetic water. The mobilization of trace metals is expected to be also influenced by the type of surrounding rocks and water quality parameters such as dissolved organic carbon.

The risk of pulmonary NTM infections and water-quality constituents among persons with cystic fibrosis in the United States, 2010-2019

Rationale

The prevalence of nontuberculous mycobacterial (NTM) pulmonary disease varies geographically in the United States. Previous studies indicate that the presence of certain water-quality constituents in source water increases NTM infection risk.

Objective

To identify water-quality constituents that influence the risk of NTM pulmonary infection in persons with cystic fibrosis in the United States.

Methods

We conducted a population-based case-control study using NTM incidence data collected from the Cystic Fibrosis Foundation Patient Registry during 2010-2019. We linked patient zip code to the county and associated patient county of residence with surface water data extracted from the Water Quality Portal. We used logistic regression models to estimate the odds of NTM infection as a function of water-quality constituents. We modeled two outcomes: pulmonary infection due to Mycobacterium avium complex (MAC) and Mycobacterium abscessus species.

Results

We identified 484 MAC cases, 222 M. abscessus cases and 2816 NTM-negative cystic fibrosis controls resident in 11 states. In multivariable models, we found that for every 1-standardized unit increase in the log concentration of sulfate and vanadium in surface water at the county level, the odds of infection increased by 39% and 21%, respectively, among persons with cystic fibrosis with MAC compared with cystic fibrosis-NTM-negative controls. When modeling M. abscessus as the dependent variable, every 1-standardized unit increase in the log concentration of molybdenum increased the odds of infection by 36%.

Conclusions

These findings suggest that naturally occurring and anthropogenic water-quality constituents may influence the NTM abundance in water sources that supply municipal water systems, thereby increasing MAC and M. abscessus infection risk.

An Overview to Technical Solutions for Molybdenum Removal: Perspective from the Analysis of the Scientific Literature on Molybdenum and Drinking Water (1990–2019)

A bibliometric analysis using the Scopus database was performed to investigate the research documents published from 1990 to 2019 in scientific sources related to molybdenum in drinking water and determine the quantitative characteristics of the research in this period. The results from the analysis revealed that the number of publications was maintained at a regular production of around 5 papers per year until 2009, followed by a fast linear increase in the production in the period from 2010 to 2016 (29 papers in 2016), but the scientific production regarding this topic was reduced in 2017 and 2018 to recover the production obtained in 2016 once again in 2019. The total contribution of the three most productive countries (USA, China and India, respectively) accounted for around 50% of the total number of publications. Environmental Science was the most common subject (51.4% contribution), followed by Chemistry (26.7% contribution). The research efforts targeted toward the search for technical solutions for molybdenum removal from water are not as important as the ones focused on the identification of molybdenum-polluted water bodies and the analysis of the health effects of the intake of molybdenum. Nevertheless, examples of technological treatments to remove molybdenum from the aqueous solution include the use of adsorption and ion exchange; coagulation, flocculation and precipitation followed by filtration; membrane technologies and biological treatments.

Bioaccumulation and human health risks of potentially toxic elements in fish species from the southeastern Carajás Mineral Province, Brazil

Anthropogenic activities may have increased the concentrations of potentially toxic elements (PTEs) in fish from the southeastern Carajás Mineral Province in Brazil, which has not yet been studied. The objectives were to determine the quality parameters of surface water and bottom sediments, and to assess the bioaccumulation and risks of Al, Fe, Ba, Cd, Co, Cr, Cu, Mn, Mo, Ni, Pb, Ti, V and Zn in fish species from the southeastern Carajás Mineral Province. Water, sediments and fish species (Colossoma macropomum, Curimata cyprinoides, Geophagus sp., Leporinus trifasciatus, and Serrasalmus eigenmanni) were collected in 14 areas in the municipalities of Parauapebas, Marabá and Canaã dos Carajás, contemplating the Gelado Stream and the Parauapebas, Tapirapé and Itacaiúnas Rivers. Water samples were subjected to physicochemical analysis using a multiparameter meter. Concentrations of PTEs in all samples were quantified by inductively coupled plasma-optical emission spectrometry. Enrichment factor (EF) and geoaccumulation index (Igeo) were calculated to study the sediment enrichment and contamination. Ecological and human health risk assessments were performed to determine the risks to the environment and population's health. EF and Igeo revealed that the sediments from the Parauapebas River and Gelado Stream are respectively enriched by Ba, Co, Cu, Cr, Mn, Pb, and Ba, Co, Cr, Ni, Pb and V. The concentrations of Fe (1.67 mg L^-1) and Mn (0.11 mg L^-1) in water and the concentrations of Cr (>0.1 mg kg^-1) and Pb (>2 mg kg^-1) in fish were above the Brazilian legislation thresholds. The ecological risk assessment revealed considerable risk from Ni and moderate risk from multiple PTEs in sediments from the Gelado Stream. Human health risks were detected for Pb in all fish species and for Mo in L.trifasciatus. These results indicate that techniques for monitoring and controlling contamination must be implemented by the environmental agencies.

Geospatial assessment of water quality using principal components analysis (PCA) and water quality index (WQI) in Basho Valley, Gilgit Baltistan (Northern Areas of Pakistan)

Public health quality in Gilgit Baltistan (GB) is at threat due to multiple water-borne diseases. Anthropogenic activities are accelerating the burden of pollution load on the glacio-fluvial streams and surface water resources of Basho Valley in Skardu district of GB. The present research has investigated the drinking water quality of the Basho Valley that is being used for domestic purposes. The study also comprehends public health status by addressing the basis drinking water quality parameters. A total of 23 water samples were collected and then analyzed to elucidate the current status of physico-chemical, metals, and microbial parameters. Principal component analysis (PCA) was applied and three principal components were obtained accounting 53.04% of the total variance, altogether. PCA identified that metallic and microbial parameters are the major factor to influence the water quality of the valley. Meanwhile, water quality index (WQI) was also computed and it was observed that WQI of the valley is characterized as excellent in terms of physico-chemical characteristics; however, metals and microbial WQI shows most of the samples are unfit for drinking purpose. Spatial distribution is also interpolated using the Inverse distance weight (IDW) to anticipate the results of mean values of parameters and WQI scores. The study concludes that water quality is satisfactory in terms of physico-chemical characteristics; however, analysis of metals shows that the concentrations of copper (Cu) (0.40 ± 0.16 mg/L), lead (Pb) (0.24 ± 0.10 mg/L), zinc (Zn) (6.77 ± 27.1 mg/L), manganese (Mn) (0.19 ± 0.05), and molybdenum (Mo) (0.07 ± 0.02 mg/L) are exceeding the maximum permissible limit as set in the WHO guidelines for drinking water. Similarly, the results of the microbial analysis indicate that the water samples are heavily contaminated with fecal pollution (TCC, TFC, and TFS > 3 MPN/100 mL). On the basis of PCA, WQI, and IDW, the main sources of pollution are most likely to be concluded as the anthropogenic activities including incoming pollution load from upstream channels. A few underlying sources by natural process of weathering and erosion may also cause release of metals in surface and groundwater. This study recommends ensuring public health with regular monitoring and assessment of water resources in the valley.

Contamination of drinking water by neonicotinoid insecticides in China: Human exposure potential through drinking water consumption and percutaneous penetration

Neonicotinoids (NEOs) are the most widely used pesticides and have posed a serious threat to human health. However, data on human exposure to NEOs are extremely scarce. To bridge this gap, human exposure potential of NEOs through drinking water consumption and percutaneous penetration was evaluated with the influences of 17 age groups, 4 seasons, 6 regions, and 2 genders. The results showed that drinking water in the present study had an upper middle level of NEO contamination. Anthropogenic activity and weather condition played important roles in the regional distribution of NEOs in tap water. For both children and adults, NEOs intake from drinking water exposure (NDE) and percutaneous exposure (NPE) in the south regions of China are significantly higher than those in the north regions, while the order of NDE and NPE by season is summer > spring = autumn > winter. Furthermore, human age and gender also have remarkable impacts on NDE and NPE. The age groups of children subjected to the highest NDE and NPE were 9 months - 2 years old and 9-12 years old, respectively. This study provides insights into the role of seasonal and regional influence, age and gender in the risk of drinking water and percutaneous exposure to NEOs.

Water quality assessment, multivariate analysis and human health risks of heavy metals in eight major lakes in Kenya

This study evaluates water quality, concentrations and health risks of heavy metals (HMs) in eight major lakes in Kenya namely Naivasha, Elementaita, Nakuru, Baringo, Bogoria, Turkana, Victoria and Magadi. Water quality was assessed using water quality index (WQI) and pollution evaluation index (PEI), while human health risk associated with ingestion and dermal contact of HMs was assessed using hazard quotients (HQ) and hazard index (HI). Principal component analysis (PCA) and hierarchical cluster analysis (HCA) were used to deduce the probable sources of the HMs. The average concentration of aluminium (Al), molybdenum (Mo), manganese (Mn), nickel (Ni), arsenic (As), zinc (Zn), selenium (Se), lead (Pb), chromium (Cr), mercury (Hg), cobalt (Co) and cadmium (Cd) in the eight lakes was 824.6, 66.1, 58.9, 16.2, 8.40, 7.84, 6.91, 4.65, 2.66, 0.86, 0.78 and 0.46, respectively, all in μg/L. Al, Mn, As, and Mo were relatively high in Rift Valley lakes and exceeded the maximum permissible levels for drinking water. Notably, high HM concentrations were recorded at the entry points of rivers and areas with high human activities. Lake Magadi had the highest average WQI of 158.8 followed by lake Elementaita (128.4), Bogoria (79.5), Nakuru (73.3), Turkana (57.6), Victoria (52.3), Baringo (42.6) and Naivasha (25.5). Lake Magadi also had the highest average PEI of 40.0 followed by Elementaita (30.1), Bogoria (16.2), Nakuru (15.7), Victoria (10.8), Baringo (9.57), Turkana (9.53) and Naivasha (5.12). Based on WQI, Lake Naivasha water was excellent for drinking, Lake Victoria, Turkana, Baringo, Nakuru, and Bogoria had good water, but water from Lake Elementaita and Magadi was of poor quality. PEI classified the lakes as minimally polluted except Lake Magadi. Multivariate analysis concluded that Pb, Cr, Ni and Se had anthropogenic sources, mainly agricultural and urban runoff, but other HMs had natural influence. Although the HMs did not pose any health risks through dermal contact, HQingestion was >1 for adults and children consuming water from Lake Elementaita, Nakuru, Bogoria and Magadi due to non-carcinogenic risks associated with As, Zn and Mo. These results are important for formulating the necessary remediation policies to improve water quality in the eight lakes.

Associations between molybdenum exposure and ultrasound measures of fetal growth parameters: A pilot study

Previous studies have suggested the association of molybdenum (Mo) exposure with some adverse outcomes. However, limited epidemiological studies have been performed to explore the association between maternal Mo exposure level and fetal growth. This study recruited 220 pregnant women during their second trimester. The mother's urinary Mo concentration was measured by inductively coupled plasma mass spectrometry (ICP-MS). The fetal biometric parameters, including head circumference (HC), biparietal diameter (BPD), femur diaphysis length (FL), and abdominal circumference (AC) were assessed by prenatal ultrasound. Estimated fetal weight (EFW) was evaluated using the formula of Hadlock. Multivariable linear regression models were applied to estimate the relationships between Mo level and fetal biometric parameters, and potential confounders were adjusted. A one-unit increment in natural-logarithm transformed urinary Mo level was significantly associated with reductions in fetal AC of -0.34 cm (95%CI: -0.63, -0.04), and was negatively related to EFW (β = -18.2, 95%CI: -40.5, 4.2). Furthermore, when participants were stratified by copper (Cu) level, the results showed that the magnitude of negative association between Mo and AC (β = -0.55, 95%CI: -1.13, 0.04) was greater in pregnant women with Cu level below median value, comparing with those with Cu level above median value (β = -0.08, 95%CI: -0.57, 0.42), and a similar pattern was found for EFW, although the interaction between Mo and Cu was not significant. Our data suggested an inverse association of maternal urinary Mo level with fetal AC and EFW during the second trimester of pregnancy. These associations might be stronger in pregnant women with relatively lower Cu levels.

Mobilization of Arsenic and Other Naturally Occurring Contaminants during Managed Aquifer Recharge: A Critical Review

Population growth and climate variability highlight the need to enhance freshwater security and diversify water supplies. Subsurface storage of water in depleted aquifers is increasingly used globally to alleviate disparities in water supply and demand often caused by climate extremes including floods and droughts. Managed aquifer recharge (MAR) stores excess water supplies during wet periods via infiltration into shallow underlying aquifers or direct injection into deep aquifers for recovery during dry seasons. Additionally, MAR can be designed to improve recharge water quality, particularly in the case of soil aquifer treatment and riverbank filtration. While there are many potential benefits to MAR, introduction of recharge water can alter the native geochemical and hydrological conditions in the receiving aquifer, potentially mobilizing toxic, naturally occurring (geogenic) contaminants from sediments into groundwater where they pose a much larger threat to human and ecosystem health. On the basis of the present literature, arsenic poses the most widespread challenge at MAR sites due to its ubiquity in subsurface sediments and toxicity at trace concentrations. Other geogenic contaminants of concern include fluoride, molybdenum, manganese, and iron. Water quality degradation threatens the viability of some MAR projects with several sites abandoning operations due to arsenic or other contaminant mobilization. Here, we provide a critical review of studies that have uncovered the geochemical and hydrological mechanisms controlling mobilization of arsenic and other geogenic contaminants at MAR sites worldwide, including both infiltration and injection sites. These mechanisms were evaluated based on site-specific characteristics, including hydrological setting, native aquifer geochemistry, and operational site parameters (e.g., source of recharge water and recharge/recovery cycling). Observed mechanisms of geogenic contaminant mobilization during MAR via injection include shifting redox conditions and, to a lesser extent, pH-promoted desorption, mineral solubility, and competitive ligand exchange. The relative importance of these mechanisms depends on various site-specific, operational parameters, including pretreatment of injection water and duration of injection, storage, and recovery phases. This critical review synthesizes findings across case studies in various geochemical, hydrological, and operational settings to better understand controls on arsenic and other geogenic contaminant mobilization and inform the planning and design of future MAR projects to protect groundwater quality. This critical review concludes with an evaluation of proposed management strategies for geogenic contaminants and identification of knowledge gaps regarding fate and transport of geogenic contaminants during MAR.

Accurate Determination of Trace Molybdenum in Drinking Water by Isotope Dilution Inductively Coupled Plasma Mass Spectrometry

A method for accurate and precise determination of trace molybdenum in drinking water by isotope dilution inductively coupled plasma mass spectrometry was developed, given the concentrations of Mo in drinking-water samples from Chaoyang and Changping districts of Beijing (China) as 1.017 ± 0.008 and 1.033 ± 0.007 μg kg^-1 (k = 2), respectively. Special care was taken for the validation of the proposed ID-ICPMS method using CRM 7203-a, a certified reference material for elemental analysis of tap water.

Provenance of drinking water revealed through compliance sampling

Understanding drinking water hydrochemistry is essential for maintaining safe drinking water supplies. Whilst targeted research surveys have characterised drinking water hydrochemistry, vast compliance datasets are routinely collected but are not interrogated amidst concerns regarding the impact of mixed water sources, treatment, the distribution network and customer pipework. In this paper, we examine whether compliance samples retain hydrochemical signatures of their provenance. We first created and subsequently undertook the first hydrochemical analysis of a novel national database of publically available drinking water compliance analyses (n = 3 873 941) reported for 2015 across England and Wales. k-means cluster analysis revealed three spatially coherent clusters. Cluster 1 is dominated by groundwater sources, with high nitrate concentrations and mineralisation, and lower organic carbon, residual chlorine and THM formation. Cluster 2 was dominated by surface water sources and characterised by low mineralisation (low conductivity and major ion concentrations), low nitrate and high organic carbon concentrations (and hence residual chlorine and THM formation). Cluster 3 shows a mixture of groundwater overlain by confining layers and superficial deposits (resulting in higher trace metal concentrations and mineralisation) and surface water sources. These analyses demonstrate that, despite extensive processing of drinking water, at the national scale signatures of the provenance of drinking water remain. Analysis of compliance samples is therefore likely to be a helpful tool in the characterisation of processes that may affect drinking water chemistry. The methodology used is generic and can be applied in any area where drinking water chemistry samples are taken.

Chemometric tool to study the mechanism of arsenic contamination in groundwater of Puducherry region, South East coast of India

To understand occurrence, distribution and source of arsenic, 175 groundwater samples from coastal aquifers of the Puducherry region were collected and analyzed for major ions and trace metals. The concentration of As in groundwater of study area ranges from not detectable - 28.88 μg/L during the post-monsoon and not detectable - 36.88 μg/L in the pre-monsoon. The desirable limit for As in groundwater is 10 μg/L as per World Health Organization and Bureau of Indian standard. About 13.64 and 11.50% of groundwater samples shows arsenic concentration higher than recommended limit. Hydrochemical facies which dominate during pre and post monsoon are Na-K-Cl-SO₄, Ca-Cl and Ca-Mg-Cl-SO₄type and Na-K-Cl-SO₄, mixedCa-Na-HCO₃, Ca-HCO₃ and mixed Ca-Mg-Cl type respectively. The Gibbs diagram suggested that rock-water interaction is major process controlling hydrochemistry of groundwater. From the Pourbaix diagram, it is inferred that H3AsO3 is the principal As species in groundwater. The PHREEQC modelling indicates supersaturation of ferric oxides and hydroxide mineral phases in aquifer system which on reductive dissolution releases arsenic into groundwater. Statistical analysis (Spearman Correlation and Principal Component Analysis) showed that reductive dissolution of As-bearing minerals and Fe-oxyhydroxides in the presence of organic matter is the major process contributing arsenic into groundwater. The relationship between As, K⁺ and HCO^-₃ indicates agricultural and competitive exchange process which is an additional contributor of arsenic in groundwater. The sources which act as a sink and responsible for the release of As into the groundwater are marine sediments enriched in As and Fe-bearing minerals and organic matter.

Variability in the chemistry of private drinking water supplies and the impact of domestic treatment systems on water quality

Tap water from 497 properties using private water supplies, in an area of metalliferous and arsenic mineralisation (Cornwall, UK), was measured to assess the extent of compliance with chemical drinking water quality standards, and how this is influenced by householder water treatment decisions. The proportion of analyses exceeding water quality standards were high, with 65 % of tap water samples exceeding one or more chemical standards. The highest exceedances for health-based standards were nitrate (11 %) and arsenic (5 %). Arsenic had a maximum observed concentration of 440 µg/L. Exceedances were also high for pH (47 %), manganese (12 %) and aluminium (7 %), for which standards are set primarily on aesthetic grounds. However, the highest observed concentrations of manganese and aluminium also exceeded relevant health-based guidelines. Significant reductions in concentrations of aluminium, cadmium, copper, lead and/or nickel were found in tap waters where households were successfully treating low-pH groundwaters, and similar adventitious results were found for arsenic and nickel where treatment was installed for iron and/or manganese removal, and successful treatment specifically to decrease tap water arsenic concentrations was observed at two properties where it was installed. However, 31 % of samples where pH treatment was reported had pH < 6.5 (the minimum value in the drinking water regulations), suggesting widespread problems with system maintenance. Other examples of ineffectual treatment are seen in failed responses post-treatment, including for nitrate. This demonstrates that even where the tap waters are considered to be treated, they may still fail one or more drinking water quality standards. We find that the degree of drinking water standard exceedances warrant further work to understand environmental controls and the location of high concentrations. We also found that residents were more willing to accept drinking water with high metal (iron and manganese) concentrations than international guidelines assume. These findings point to the need for regulators to reinforce the guidance on drinking water quality standards to private water supply users, and the benefits to long-term health of complying with these, even in areas where treated mains water is widely available.

Aquatic acute toxicity assessments of molybdenum (+VI) to Daphnia magna

Generally, molybdenum (Mo) metals in the environment are very rare, but wastewater discharges from industrial processes may contain high concentrations of Mo, which has the potential to contaminate water or soil if not handled properly. In this study, the impact of three common compounds of hexavalent Mo (sodium molybdate (Na2MoO4‧2H2O), ammonium molybdate ((NH4)6Mo7O24‧4H2O) and molybdenum trioxide (MoO3)) in an aquatic system were assessed based on 48-h exposure acute toxicity to Daphnia magna (D. magna). The LC50 toxicities for associated conjugate ions including Na(+), Cl(-), SO4(2-), and NH4(+) were determined. Furthermore, the LC50 values for the three forms of hexavalent Mo were determined, and the acute toxicities of the Mo forms were found to follow the order: (NH4)6Mo7O24‧4H2O > MoO3 > Na2MoO4‧2H2O in solution. (NH4)6Mo7O24‧4H2O exhibited the lowest LC50 of 43.3 mg L(-1) (corresponding to 23.5 mg Mo L(-1)) among the three molybdenum salts. The research confirmed that the toxicity of molybdenum in the aquatic system is highly dependent on the form of molybdenum salts used, and is also associated with the influence of the background water quality.