Anoxia begets anoxia: A positive feedback to the deoxygenation of temperate lakes.

Declining oxygen concentrations in the deep waters of lakes worldwide pose a pressing environmental and societal challenge. Existing theory suggests that low deep-water dissolved oxygen (DO) concentrations could trigger a positive feedback through which anoxia (i.e., very low DO) during a given summer begets increasingly severe occurrences of anoxia in following summers. Specifically, anoxic conditions can promote nutrient release from sediments, thereby stimulating phytoplankton growth, and subsequent phytoplankton decomposition can fuel heterotrophic respiration, resulting in increased spatial extent and duration of anoxia. However, while the individual relationships in this feedback are well established, to our knowledge, there has not been a systematic analysis within or across lakes that simultaneously demonstrates all of the mechanisms necessary to produce a positive feedback that reinforces anoxia. Here, we compiled data from 656 widespread temperate lakes and reservoirs to analyze the proposed anoxia begets anoxia feedback. Lakes in the dataset span a broad range of surface area (1-126,909 ha), maximum depth (6-370 m), and morphometry, with a median time-series duration of 30 years at each lake. Using linear mixed models, we found support for each of the positive feedback relationships between anoxia, phosphorus concentrations, chlorophyll a concentrations, and oxygen demand across the 656-lake dataset. Likewise, we found further support for these relationships by analyzing time-series data from individual lakes. Our results indicate that the strength of these feedback relationships may vary with lake-specific characteristics: For example, we found that surface phosphorus concentrations were more positively associated with chlorophyll a in high-phosphorus lakes, and oxygen demand had a stronger influence on the extent of anoxia in deep lakes. Taken together, these results support the existence of a positive feedback that could magnify the effects of climate change and other anthropogenic pressures driving the development of anoxia in lakes around the world.

A hydrochemical and isotopic approach for source identification and health risk assessment of groundwater arsenic pollution in the central Yinchuan basin.

Arsenic contamination of groundwater is becoming a major global issue as it can severely affect the safety of drinking water and human health. In this paper, 448 water samples were investigated to study the spatiotemporal distribution, source identification and human health risk of groundwater arsenic pollution in the central Yinchuan basin by applying a hydrochemical and isotopic approach. The results showed that arsenic concentrations in groundwater ranged from 0.7 µg/L to 26 µg/L with a mean of 2.19 µg/L, and 5.9% of samples were above 5 µg/L, indicating the arsenic pollution of groundwater in the study area. High arsenic groundwater was mainly distributed in the northern and eastern areas along the Yellow river. The main hydrochemistry type of high arsenic groundwater was HCO3·SO4-Na·Mg, and the dissolution of arsenic-bearing minerals in sediment, irrigation water infiltration and aquifer recharge from the Yellow river were the main sources of arsenic in groundwater. The arsenic enrichment was dominantly controlled by the TMn redox reaction and the competitive adsorption of HCO3-, and the influence of anthropogenic activities was limited. The health risk assessment suggested that the carcinogenic risk of As for children and adults greatly exceeded the acceptable risk threshold of 1E-6, displaying a high carcer risk, while the non-carcinogenic risks of As, F-, TFe, TMn and NO3- in 2019 were largely higher than the acceptable risk threshold (HQ > 1). The present study provides insight into the occurrence, hydrochemical processes and potential health risk of arsenic pollution in groundwater.

An integrated approach for quantifying source apportionment and source-oriented health risk of heavy metals in soils near an old industrial area.

Soil contamination of heavy metals (HMs) caused by the long-term industrial activities has become a major environmental issue due to its adverse effects on human health and ecosystem. In this paper, 50 soil samples were analyzed to evaluate the contamination characteristics, source apportionment and source-oriented health risk of HMs in soils near an old industrial area in NE China by applying an integrated approach of Pearson correlation analysis, Positive matrix factorization (PMF) model and Monte Carlo simulation. The results showed that the mean concentrations of all HMs greatly exceeded the soil background values (SBV), and the surface soils in the study area were heavily polluted with HMs, displaying a very high ecological risk. The toxic HMs emitted from the bullet production were identified as the primary source of HMs contamination in soils, with a contribution rate of 33.3%. The human health risk assessment (HHRA) suggested that the Hazard quotient (HQ) values of all HMs for children and adults are within the acceptable risk level (HQ < 1). The carcinogenic risk (CR) values of HMs for children and adults significantly exceeded the acceptable threshold of 1E-6 with a basic trend: As > Pb > Cr > Co > Ni, indicating a high cancer risk. For source-oriented health risk, the CR of four pollution sources for children and adults shows a same trend: Factor 4 > Factor 3 > Factor 2 > Factor 1. Among those, the source of HMs pollution from bullet production is the largest contributor to cancer risk, and As and Pb are the most important HMs pollutants that cause cancer risk to humans. The present study sheds some light on the contamination characteristics, source apportionment and source-health risk assessment of HMs in industrially contaminated soils, which helps improve the management of environmental risk control, prevention and remediation.

Spatial distribution, contamination characteristics and ecological-health risk assessment of toxic heavy metals in soils near a smelting area.

Soil heavy metals (HMs) contamination stemming from smelting and mining activities is becoming a global concern due to its devastating impacts on the environment and human health. In this study, 128 soil samples were investigated to assess the spatial distribution, contamination characteristics, ecological and human health risk of HMs in soils near a smelting area by using BP artificial neural network (BP-ANN) and Monte Carlo simulation. The results showed that the concentrations of all five HMs in the soil greatly exceeded the background value of study area with a basic trend: Pb > As > Cr > Cd > Hg, indicating a high pollution level. Arsenic and lead were the major pollutants in the study area with an exceedance rate of 78.95% and 28.95%, respectively. The toxic fume and dust emitted during the smelting process were identified as the major sources of HMs pollution in soil, while Cd pollution was mainly caused by agricultural activities near the study area. The probabilistic risk assessment suggested that the average HQ values of five HMs for children and adults exceeded the acceptable threshold with a trend: As > Pb > Cr > Cd > Hg. The average CR values of As, Cr and Pb for all population were greatly larger than the acceptable threshold (CR ≥ 1), indicating a high cancer risk. However, the CR values of Cd for adults and children were within the acceptable threshold (CR < 1), implying no cancer risk. The results of the present study can provide some insight into the contamination characteristics, ecological and human health risk of HMs in contaminated soils by mining and smelting activities, which can help prevent and control soil pollution and environmental risk.

Speciation, in vitro bioaccessibility and health risk of antimony in soils near an old industrial area.

Antimony (Sb) contamination in soil has become a major environmental issue due to its adverse effects on ecosystems and human health. In this paper, 1255 soil samples were analyzed to investigate the distribution, speciation, in vitro oral bioaccessibility (8 soil samples) and human health risk of Sb in contaminated soils and its impacts on groundwater. The results showed that 4.38 % of the soil samples within the depth of 0-31 m exceeded the Risk Screening Values (RSV). Sb mainly existed in the residual fraction (38.05 % ∼ 94.22 %), Fe/Mn oxides (0.01 % ∼ 31.80 %) and the organic fraction (0.32 % ∼ 21.55 %) with poor mobility. The bioaccessibility of Sb was approximately <31 %. The total concentration of Sb (TSb) in soil was the dominant factor influencing the bioaccessible concentration of Sb (SbBio). Soil physiochemical properties such as Fe, Mn, and organic matter content (OM) also affected the magnitude of SbBio. Health risk assessment based on in vitro bioaccessibility suggested that the hazard quotient (HQ) of adults was within the acceptable level (HQ < 1) for industrial scenario, while the HQ of children and adults was greater than the acceptable level (HQ ≥ 1) for residential scenario, with a higher risk to children than adults. The results of the leaching experiment involving Dilution-Attenuation Factor (DAF) model suggested that the predicted maximum concentration of Sb in groundwater was 2.40 µg/L that is lower than the acceptable standard value (5 µg/L), implying that groundwater was not contaminated by Sb in soil. The findings of this study provide some insights into the speciation, in vitro bioaccessibility and health risk of toxic trace metals in contaminated soils and the potential environmental impacts.

Bioavailability and health risk of toxic heavy metals (As, Hg, Pb and Cd) in urban soils: A Monte Carlo simulation approach.

Toxic heavy metals pollution in urban soil has become a major global issue due to its adverse effects on the environment and human health. In this paper, 26 soil samples were analyzed to assess the speciation, bioavailability and human health risk of Arsenic (As), Mercury (Hg), Lead (Pb) and Cadmium (Cd) in urban soils of a heavy industrial city in NE China by using a Monte Carlo simulation approach. The results showed that As, Hg, Pb and Cd concentrations in the soil all exceed the corresponding background value of study area. Mercury displays the highest value of geo-accumulation index (Igeo), followed by Cd, Pb and As. The pollution load index (PLI) value (>2) indicates a moderate pollution level in the study area. The chemical speciation of HMs mainly exists in residual fraction except Cd. The probabilistic health risk assessment demonstrated that the mean values of Total Carcinogenic Risk (TCR) and Hazard Index (HI) calculated with total concentration are at the unacceptable level, with a higher risk to children than adults. However, the mean values calculated with bioavailable fraction are all within the acceptable level. The mean value of TCR and HI obtained by bioavailable fraction is about 96% and 95% lower than that obtained by total concentration, respectively. Thus, this study suggested that the bioavailable fraction of HMs is a more reliable parameter for health risk assessment, while the total concentration of HMs can overestimate the true risk. The results of this study provide some insight into the speciation, bioavailability and health risks of toxic heavy metals in urban soils in those heavy industrial cities.

Potential risk assessment of groundwater to address the agricultural and domestic challenges in Ordos Basin.

The safety of groundwater has been a great concern for irrigation and drinking purposes in recent decades due to the increasing impacts of anthropogenic activities. There are several standards to evaluate the groundwater quality for different utilization purposes. In this paper, 804 samples covering the entire Ordos Basin across five provinces were used to evaluate the irrigation suitability and human health risks. The results showed that the sequence of cationic concentration was Na+ > Ca2+ > Mg2+ > K+ > NH4 +, and the anion concentration was HCO3 - > SO4 2- > Cl- > NO3 - > F- > NO2 -. For drinking purposes, TDS, Na+, SO4 2-, F-, TH and NO3 - exceed seriously the regulated standard in the study area. For irrigating purposes, 80% of the water in the study area belongs to "good water" according to the evaluation of salinity and alkalinity. Saline water which is not suitable for irrigation accounts for about 9%. High health risks of fluoride ions are mainly observed to the samples representing the western part of the study area, while the health risks of nitrates spread throughout the study area. Health risk is not only related to location, but also varies with age, and it is found that children suffer more threats than adults.

Simultaneous analysis of 11 haloacetic acids by direct injection-liquid chromatography-electrospray ionization-triple quadrupole tandem mass spectrometry and high resolution mass spectrometry: occurrence and evolution in chlorine-treated water.

A fast, simple, selective, and sensitive method for the analysis of 11 haloacetic acids (HAAs) in chlorine-treated water has been developed. The method is based on liquid chromatography-electrospray ionization-triple quadrupole tandem mass spectrometry (LC/ESI-QqQ-MS/MS) with direct injection of the aqueous sample. The main novelty of this method over the previously published procedures based on different techniques of mass spectrometry with direct injection is the combination of the simultaneous analysis of three types of HAAs (chlorinated, brominated, and iodinated) with its simplicity and low LODs (0.01-0.6 µg/L), avoiding the use of ion-pairing reagents for LC as well as the complexity and high cost of other techniques such as ion chromatography and capillary electrophoresis coupled to tandem mass spectrometry (IC-MS/MS and CE-MS/MS). The developed method was compared with another procedure carried out in our laboratory based on direct injection-liquid chromatography-electrospray ionization-high-resolution mass spectrometry with an Orbitrap analyzer (LC/ESI-Orbitrap-HRMS). The application of this technique to HAA analysis had not been previously described. LODs achieved by LC-HRMS (0.01-2 µg/L) were higher than the ones obtained by LC-MS/MS. Therefore, the LC/ESI-QqQ-MS/MS method was applied to the analysis of real samples. Quality parameters were calculated with satisfactory results and real samples related to three drinking water treatment plants (DWTPs), tap water, and the drinking water distribution system of Barcelona area (Catalonia, NE Spain) were analyzed. Furthermore, the evolution of HAA concentration along time in a DWTP-treated water sample was studied.

Health risk assessment of phreatic water based on triangular fuzzy theory in Yinchuan plain.

Groundwater quality relating closely to human health has become a great concern to the whole society, especially in heavily polluted areas. Yinchuan Plain, located in the arid and semi-arid region of Northwestern China, where people rely heavily on groundwater resource. However, due to the improper groundwater exploitation and negative effect of human activities in recent years, groundwater quality in Yinchuan plain become deteriorated. For the sustainable utilization and protection of groundwater resources, health risk assessment (HRA) of phreatic water is conducted in this paper. On the basis of model recommended by EPA, triangular fuzzy number is applied to establish risk assessment model for health risk assessment of adults and children in wet and dry seasons, respectively. Results of HRA indicate that carcinogenic risk of arsenic is highest among the risk from components in phreatic water, and the highest risk from arsenic to adults and children in wet and dry season are 6.48 × 10-6a-1 and 9.56 × 10-6a-1, 1.08 × 10-5a-1 and 1.59 × 10-5a-1, respectively. This study also states that in Yinchuan Plain carcinogenic risk from drinking groundwater can be 3-4 times magnitude higher than the noncarcinogenic risk. Also it is found that the health risk to children is as 1.5-2 times as to adults, while the uncertainties of adults' health risk are higher than that of children.

Identification of the hydrogeochemical processes and assessment of groundwater quality using classic integrated geochemical methods in the Southeastern part of Ordos basin, China.

Insufficient understanding of the hydrogeochemistry of aquifers makes it necessary to conduct a preliminary water quality assessment in the southern region of Ordos Basin, an arid area in the world. In this paper, the major ions of groundwater have been studied aiming at evaluating the hydrogeochemical processes that probably affect the groundwater quality using 150 samples collected in 2015. The two prevalent hydrochemical facies, HCO3Mg·Na·Ca and HCO3Mg·Ca·Na type water, have been identified based on the hydrochemical analysis from Piper trilinear diagram. Compositional relations have been used to assess the origin of solutes and confirm the predominant hydrogeochemical processes responsible for the various ions in the groundwater. The results show that the ions are derived from leaching effect, evaporation and condensation, cation exchange, mixing effect and human activities. Finally groundwater quality was assessed with single factor and set pair methods, the results indicate that groundwater quality in the study region is generally poor in terms of standard of national groundwater quality. The results obtained in this study will be useful to understand the groundwater quality status for effective management and utilization of the groundwater resource.

Hydrochemical characterization and pollution sources identification of groundwater in Salawusu aquifer system of Ordos Basin, China.

Ordos Basin is located in an arid and semi-arid region of northwestern China, which is the most important energy source bases in China. Salawusu Formation (Q3 s) is one of the most important aquifer systems of Ordos Basin, which is adjacent to Jurassic coalfield areas. A large-scale exploitation of Jurassic coal resources over ten years results in series of influences to the coal minerals, such as exposed to the oxidation process and dissolution into the groundwater due to the precipitation infiltration. Therefore, how these processes impact groundwater quality is of great concerns. In this paper, the descriptive statistical method, Piper trilinear diagram, ratios of major ions and canonical correspondence analysis are employed to investigate the hydrochemical evolution, determine the possible sources of pollution processes, and assess the controls on groundwater compositions using the monitored data in 2004 and 2014 (before and after large-scale coal mining). Results showed that long-term exploration of coal resources do not result in serious groundwater pollution. The hydrochemical types changed from HCO3(-)-CO3(2-) facies to SO4(2-)-Cl facies during 10 years. Groundwater hardness, nitrate and sulfate pollution were identified in 2014, which was most likely caused by agricultural activities.

Analysis of 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (MX) and its brominated analogues in chlorine-treated water by gas chromatography coupled to triple quadrupole tandem mass spectrometry (GC-QqQ-MS/MS).

A simple, selective and sensitive method for the analysis of the strong mutagen 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (MX) and its brominated analogues (BMXs) in chlorine-treated water has been developed. The method is based on gas chromatography coupled to triple quadrupole tandem mass spectrometry (GC-QqQ-MS/MS), previous liquid-liquid extraction (LLE) of a smaller sample volume compared to other methods and on-line derivatization with a silylation reactive. GC-QqQ-MS/MS has been raised as an alternative easier to perform than gas chromatography coupled to high resolution mass spectrometry (GC-HRMS) for the analysis of MX and BMXs, and it allows to achieve low LODs (0.3 ng/L for MX and 0.4-0.9 ng/L for BMXs). This technique had not been previously described for the analysis of MX and BMXs. Quality parameters were calculated and real samples related to 3 drinking water treatment plants (DWTPs), tap water and both untreated and chlorinated groundwater were analyzed. Concentrations of 0.3-6.6 ng/L for MX and 1.0-7.3 ng/L for BMXs were detected. Results were discussed according to five of the main factors affecting MX and BMXs formation in chlorine-treated water (organic precursors, influence of bromide ions, evolution of MX and BMXs in the drinking water distribution system, groundwater chlorination and infiltration of water coming from chlorination processes in groundwater).

Increased and mistimed sex hormone production in night shift workers.

BACKGROUND: Night shift work has been associated with an increased risk for breast and prostate cancer. The effect of circadian disruption on sex steroid production is a possible underlying mechanism, underinvestigated in humans. We have assessed daily rhythms of sex hormones and melatonin in night and day shift workers of both sexes. METHODS: We recruited 75 night and 42 day workers, ages 22 to 64 years, in different working settings. Participants collected urine samples from all voids over 24 hours on a working day. Urinary concentrations of 16 sex steroid hormones and metabolites (estrogens, progestagens, and androgens) and 6-sulfatoxymelatonin were measured in all samples. Mean levels and peak time of total and individual metabolite production were compared between night and day workers. RESULTS: Night workers had higher levels of total progestagens [geometric mean ratio (GMR) 1.65; 95% confidence intervals (CI), 1.17-2.32] and androgens (GMR: 1.44; 95% CI, 1.03-2.00), compared with day workers, after adjusting for potential confounders. The increased sex hormone levels among night shift workers were not related to the observed suppression of 6-sulfatoxymelatonin. Peak time of androgens was significantly later among night workers, compared with day workers (testosterone: 12:14 hours; 10:06-14:48 vs. 08:35 hours; 06:52-10:46). CONCLUSIONS: We found increased levels of progestagens and androgens as well as delayed peak androgen production in night shift workers compared with day workers. IMPACT: The increase and mistiming of sex hormone production may explain part of the increased risk for hormone-related cancers observed in night shift workers.

Circadian variation of melatonin, light exposure, and diurnal preference in day and night shift workers of both sexes.

BACKGROUND: Light-at-night has been shown in experimental studies to disrupt melatonin production but this has only partly been confirmed in studies of night shift workers. In this cross-sectional study, we examined the circadian variation of melatonin in relation to shift status, individual levels of light-at-night exposure, and diurnal preference, an attribute reflecting personal preference for activity in the morning or evening. METHODS: One hundred and seventeen workers (75 night and 42 day) of both sexes, ages 22 to 64 years, were recruited from four companies. Participants collected urine samples from all voids over 24 hours and wore a data logger continuously recording their light exposure. Sociodemographic, occupational, lifestyle, and diurnal preference information were collected by interview. Concentrations of urinary 6-sulfatoxymelatonin (aMT6s), the main melatonin metabolite, were measured. RESULTS: Mean aMT6s levels were lower in night [10.9 ng/mg creatinine/hour; 95% confidence interval (CI), 9.5-12.6] compared with day workers (15.4; 95% CI, 12.3-19.3). The lowest aMT6s levels were observed in night workers with morning preference (6.4; 95% CI, 3.0-13.6). Peak time of aMT6s production occurred 3 hours later in night (08:42 hour, 95% CI, 07:48-09:42) compared with day workers (05:36 hour, 95% CI, 05:06-06:12). Phase delay was stronger among subjects with higher light-at-night exposure and number of nights worked. CONCLUSIONS: Night shift workers had lower levels and a delay in peak time of aMT6s production over a 24-hour period. Differences were modified by diurnal preference and intensity of light-at-night exposure. IMPACT: Night shift work affects levels and timing of melatonin production and both parameters may relate to future cancer risk.

Linear and non-linear chemometric modeling of THM formation in Barcelona's water treatment plant.

The complex behavior observed for the dependence of trihalomethane formation on forty one water treatment plant (WTP) operational variables is investigated by means of linear and non-linear regression methods, including kernel-partial least squares (K-PLS), and support vector machine regression (SVR). Lower prediction errors of total trihalomethane concentrations (lower than 14% for external validation samples) were obtained when these two methods were applied in comparison to when linear regression methods were applied. A new visualization technique revealed the complex nonlinear relationships among the operational variables and displayed the existing correlations between input variables and the kernel matrix on one side and the support vectors on the other side. Whereas some water treatment plant variables like river water TOC and chloride concentrations, and breakpoint chlorination were not considered to be significant due to the multi-collinear effect in straight linear regression modeling methods, they were now confirmed to be significant using K-PLS and SVR non-linear modeling regression methods, proving the better performance of these methods for the prediction of complex formation of trihalomethanes in water disinfection plants.

Association of ITPA gene polymorphisms and the risk of ribavirin-induced anemia in HIV/hepatitis C virus (HCV)-coinfected patients receiving HCV combination therapy.

Polymorphisms of the ITPA gene have been associated with anemia during combination therapy in hepatitis C virus (HCV)-monoinfected patients. Our aim was to confirm this association in HIV/HCV-coinfected patients. In this prospective, observational study, 73 HIV/HCV-coinfected patients treated with pegylated interferon plus ribavirin (RBV) were enrolled. Two single nucleotide polymorphisms within or adjacent to the ITPA gene (rs1127354 and rs7270101) were genotyped. The associations between the ITPA genotype and anemia or treatment outcome were examined. Fifty-nine patients (80.8%) had CC at rs1127354, whereas 14 (19.2%) had a CA/AA ITPA genotype. Percent decreases from baseline hemoglobin level were significantly greater in patients with the CC genotype than in those with the CA/AA genotype at week 4 (P = 0.0003), week 12 (P < 0.0001), and week 36 (P = 0.0102) but not at the end of treatment. RBV dose reduction was more often needed in patients with the CC genotype than in those with the CA/AA genotype (odds ratio [OR] = 11.81; 95% confidence interval [CI] = 1.45 to 256.17; P = 0.0039), as was erythropoietin therapy (OR = 8.28; 95% CI = 1.04 to 371.12; P = 0.0057). Risk factors independently associated with percent hemoglobin nadir decrease were RBV dose reduction (OR = 11.72; 95% CI = 6.82 to 16.63; P < 0.001), baseline hemoglobin (OR = 1.69; 95% CI = 0.23 to 3.15; P = 0.024), and body mass index (OR = -0.7; 95% CI = -1.43 to 0.03; P = 0.061). ITPA polymorphism was not an independent predictor of sustained virological response. Polymorphisms at rs1127354 in the ITPA gene influence hemoglobin levels during combination HCV therapy and the need for RBV dose reduction and erythropoietin use in HIV/HCV-coinfected patients.

Chemometric modeling and prediction of trihalomethane formation in Barcelona's water works plant.

Formation and occurrence of trihalomethanes (CHCl3, CHBr3, CHCl2Br, and CHBr2Cl) are investigated in water chlorination disinfection processes in the Barcelona's water works plant (WWP). Twenty-three WWP variables were measured and investigated for correlation with trihalomethane formation. Multivariate statistical methods including principal component analysis (PCA), multilinear regression (MLR), stepwise MLR (SWR), principal component regression (PCR) and partial least squares regression (PLSR) have been used and compared to model and predict the complex behavior observed for the measured trihalomethane concentrations. The results, obtained by PCA as well as the evaluation of the statistical significance of the coefficients in the linear regression vectors, revealed that the most important WWP variables for trihalomethane formation were: water temperature, total organic carbon, added chlorine concentrations, UV absorbance and turbidity at different sites of the WWP, as well as other variables like wells supply flow levels and carbon filters age. Overall, MLR and PLSR methods performed the best and gave similar good predictive properties. Best results were obtained for the total sum of trihalomethane concentrations, TTHM, with average modeling and prediction relative errors of 12% and 16%, respectively. Among the individual trihalomethanes, the concentrations of CHBr3 were the worst predicted ones with average modeling and prediction relative errors between 21-25% and 29-31%, respectively, followed by CHCl2Br with 23-26% and 25-27%. Better predictions were obtained for the concentrations of CHBr2Cl with relative modeling and prediction errors varying between 14-17% and 21%, and for the concentrations of CHCl3 with 21-24% and 23-25% errors, respectively.