Geochemical Characteristics and Geological Significance of Coalbed Methane in Suzhou Mining Area of the Huaibei Coalfield.

In this study, gas contents, geochemical features, and origins of coalbed methane (CBM) and their influence factors were investigated on nos. 7 and 8 CBM reservoirs from the Suzhou mining area of the Huaibei coalfield. Results have shown that the selected CBM reservoirs are characterized by various thickness (0.50-9.19 m) and buried depth (619-1226 m), but have relatively better lithology of surrounding rocks. Coal samples have similar maturity (Ro,max = 0.71-1.05%), but show differences in chemical composition and macerals. Gas content of nos. 7 and 8 CBM reservoirs ranges from 6.13-12.25 m3/t, but the value of former is lower than that of later one overall. In addition, CH4 is a predominantly component with a value of 88.23-99.00% (avg. 96.69%), and the heavy hydrocarbon gas (C2+) is 0.00-1.93% (avg. 0.41%). The δ13CCH4 value ranges from -64.54 to -46.36‰ (avg. -53.92‰), and the δ13DCH4 value is -224.36 to -211.75‰ (avg. -219.09‰). Based on the analysis of components and isotopic values, the CBM samples are thermogenic (20.92-71.30%; avg 50.09%) and secondary biogenic gases (28.70-74.49%; avg. 49.91%). Gas content shows changeable characteristics at a buried depth of 300-1300 m, which is affected by buried depth, reservoir temperature and pressure, Mad and vitrinite. However, the CH4 concentration shows no correlation with buried depth. Moreover, the buried depth is significantly positively correlated to δ13CCH4 and δ13DCH4. Based on the relationship between gas content and isotope values, it suggests that δ13CCH4 or δ13DCH4 may have a relationship with the main controlling factors of gas content.

Distribution pattern of dissolved organic matter in pore water of sediments from three typical areas of western Lake Taihu and its environmental implications.

The migration, transformation, and accumulation of dissolved organic matter (DOM) in pore water of sediment cores play a pivotal role in lacustrine carbon cycling. In order to understand the dynamics of DOM in the sediments of large shallow eutrophic lakes, we examined the vertical profiles of DOM and the benthic fluxes of dissolved organic carbon (DOC) in sediment cores located in algae accumulated, dredged, and central areas of eutrophic Lake Taihu, China. Optical properties showed the significant influence of terrestrial inputs on the DOM components of pore water in the algae accumulated area but an abundant accumulation of autochthonous DOM in the central area. The benthic fluxes of DOC ranging from -458.2 to -139.4 mg·m-2·d-1 in the algae accumulated area displayed an opposite diffusion direction to the other two areas. The flux ranges of 9.5-31.2 mg·m-2·d-1 in the dredged area and 14.6-48.0 mg·m-2·d-1 in the central area were relatively smaller than those in the previously reported lake ecosystems with low trophic levels. Dredging engineering disturbed the pre-dredging distribution patterns of DOM in sediment cores. The deposition, accumulation, and transformation of massive algae scums in eutrophic lakes probably promoted the humification degree of sediments.

Environmental geochemical baseline determination and pollution assessment of heavy metals in farmland soil of typical coal-based cities: A case study of Suzhou City in Anhui Province, China.

Soil is the foundation of agricultural green development and human survival; the study of local environmental geochemical baselines can guide soil management and ensure the safe use of soil. In this study, a total of 100 shallow farmland soil samples were collected in each township of Yongqiao District, Suzhou City, Anhui Province, China. Herein, the contents of 10 heavy metal elements including As, Hg, Cd, Pb, Cr, Cu, Mn, Ni, Zn and Fe were determined. In addition, the geochemical baseline of heavy metals was calculated based on the relative cumulative frequency curve method, and the soil pollution status was evaluated. The results show that the average contents of As, Hg, Cd, Cu, Mn and Zn exceeded the soil background values of Anhui Province by 3.82%-64.74% (1.04-1.65 times), meanwhile, the average contents of Pb and Cr were lower than the soil background values of Anhui Province. The average contents of Cd, Cr, Cu, Mn and Ni exceeded the Chinese soil background values by 1.61%-64.74% (0.98-1.65 times). The geochemical baseline values of As, Hg, Cd, Pb, Cr, Cu, Mn, Ni, Zn and Fe were 9.585 mg/kg, 0.028 mg/kg, 0.112 mg/kg, 21.59 mg/kg, 53.66 mg/kg, 19.31 mg/kg, 543.8 mg/kg, 24.93 mg/kg, 50.57 mg/kg and 2.654%, respectively. The pollution assessment results also showed that most of the farmland soil samples in the study area were non-polluting or slightly polluted based on geochemical baselines. Hg and Cu in a few samples were moderately polluted, and Cd in only one sample was moderately intensely polluted. Combined with the distribution of pollution and field investigation, it is considered that Hg comes from atmospheric deposition and agricultural non-point source pollution of industrial pollution. Cu comes from animal husbandry and agricultural pollution. Meanwhile, Cd is related to natural sources, wood processing and agricultural fertiliser application. The study demonstrated that the calculation of soil geochemical background value should take full account of the differences between the various regions, combined with the current state, particularly the pre-consideration of the distribution of elements or pollutants. Then, reasonably select the evaluation standard value so that the evaluation results can truly reflect the state of soil pollution.

Spatial distributions of microbial diversity in the contaminated deep groundwater: A case study of the Huaibei coalfield.

The impact of coal mining activities on the structure of groundwater microbial communities in coal mining areas has gradually received academic attention. In this study, hydrochemical analysis and sequencing of the V4 region of the 16S rRNA gene were carried out using groundwater samples from the fourth aquifer in the loose layer of Cenozoic, the sandstone fissure aquifer in the coal measure strata of Permian, the Carboniferous Taiyuan Formation limestone aquifer, and the Ordovician limestone aquifer, at depths of 250 m, 600 m, 750 m, and 1000 m in monitoring wells. Results showed that the operational taxonomy units (OTUs) in the deep groundwater ecosystem were clustered distinguishably between the contaminated and the uncontaminated aquifers. The microbial community alpha-diversity of groundwater was significantly correlated with depth, and the richness of microbial community composition decreased with increasing depth. Proteobacteria (34.41%-97.41%), was found to be the dominant phylum, Gammaproteobacteria (10.05%-92.06%) was the dominant class and "Unassigned" (4.12%-64.72%) was dominant at the genus level. The number of endemic bacteria in the four aquifers was 1, 33, 99 and 11, respectively. It was also found that F-, oxidation-reduction potential (ORP), and TOC were the main environmental variables affecting the groundwater all OTUs, abundant OTUs, and rare OTUs, respectively. These results indicate that the activity of rare OTU subcommunities increases gradually with increasing aquifer depth and that mining significantly enriched Thiovirga in deep groundwater. In addition, it was found that with the increase of depth, the effect of ORP on microbial community abundance decreased. This study deepens our understanding of the evolution characteristics of microbial communities in deep groundwater in coal mining areas. The unique characteristics of microbial communities characteristics of four aquifers with different depths provide a microbial perspective for understanding the characteristics of deep aquifers.

Occurrence, controlling factors and noncarcinogenic risk assessment based on Monte Carlo simulation of fluoride in mid-layer groundwater of Huaibei mining area, North China.

Fluoride groundwater pollution is a major challenge to ensuring a safe groundwater supply for the global community. This study emphasized mid-layer groundwater (MG) as the main water supply source in the Huaibei mining area, North China. A total of 74 groundwater samples were taken to determine the hydrochemistry, source provenance, driving forces of high-fluoride groundwater, and associated probabilistic health risk using Monte Carlo simulation. The fluoride concentration in 55.56 % of the MG samples exceeded the Chinese drinking water permissible limit of 1 mg/L. In addition, MG is characterized by the hydrochemical faces of HCO3- type and Na+ type, lower Ca2+ and higher TDS concentration. Fluoride enrichment was predominantly controlled by the geogenic sources of fluorite dissolution, silicate weathering and lateral supply from the Carboniferous Taiyuan Formation limestone aquifer (CLA). In addition, the driving forces of high-fluoride groundwater were an alkaline environment, low Ca2+ concentration, high Na+ and HCO3- concentration, cation exchange between Ca2+ and Na+ on the surface of clay minerals, and competitive adsorption of HCO3-. The health risk assessment of F- for noncarcinogenic risk showed that the HQ values of 28.16 % of groundwater samples exceeded the safety limit of 1 for infants, followed by 2.1 % for children and 0 % for both adult females and males. Infants and children are more prone to the impact of excessive F-. The findings of this study will provide new insights into the geochemical behavior of F- and the safety of drinking water.

Quantifying nitrate pollution sources of shallow groundwater and related health risks based on deterministic and Monte Carlo models: A study in Huaibei mining area, Huaibei coalfield, China.

Nitrate pollution in groundwater is a global environmental concern. As a result, accurate identification of potential sources for such pollution is of critical significance to the effective control of groundwater quality. In this study, forty-nine shallow groundwater samples were collected from the Huaibei mining area. Hydro-chemical characterization, geospatial analysis technique, dual nitrate isotopes (δ15N-NO3- and δ18O-NO3-), Bayesian model and health risk assessment model were adopted for exploring the conditions, sources, proportion, and potential health risks of nitrate pollution for the first time in the study area. The results showed that the nitrate concentration ranged from 0.00 to 293.21 mg/L, and that 18.37% groundwater samples exceeded the standard of drinking water in China (GB 5749-2006). Based on the dual isotopic values of nitrate, it could be concluded that nitrification was dominated migration and transformation process of nitrogen. The results of Bayesian model showed that the proportional contributions of the potential nitrate pollution sources in shallow groundwater were manure and sewage (M&S) (39.54 %), NH4+ in fertilizer and precipitation (NHF&P) (34.93 %), soil nitrogen (SN) (14.89 %), and NO3- in atmospheric deposition (NAD) (10.64 %). The health risk assessment indicated that non-carcinogenic risks posed by NO3--N was higher for children than adults. The primary exposure pathway was oral ingestion. Monte Carlo simulation were applied to evaluate model uncertainty. The probabilities of non-carcinogenic risks were up to 12.54 % for children and 5.22 % for adults. In order to protect water quality and drinking water safety, it was suggested that effective nitrate reduction strategies and better management practices can be implemented.

Study on the Influence of Mining Activities on the Quality of Deep Karst Groundwater Based on Multivariate Statistical Analysis and Hydrochemical Analysis.

Long-term mining activities have changed the hydrogeochemical evolution process of groundwater and threatened the safe use of groundwater. By using the methods of hydrochemistry and multivariate statistical analysis, this study determined the hydrogeochemical evolution mechanism affecting the quality of karst groundwater by analyzing the conventional hydrochemistry data of the karst groundwater of the Carboniferous Taiyuan Formation in Hengyuan Coal Mine in the recent 12 years. The results show that, under the disturbance of mining, the quality of karst groundwater in Taiyuan Formation is poor, mainly because the contents of Na++K+ and SO42- are too high to allow usage as drinking water. The reason for the high content of SO42- in karst groundwater lies in the dissolution of gypsum and the oxidation of pyrite, and the high content of Na++K+ lies in the cation exchange. Influenced by the stratum grouting, the circulation of karst groundwater is improved, the cation exchange is weakened, and the desulfurization is enhanced. In the future, it is predicted that the hydrochemical type of karst groundwater in Taiyuan Formation in the study area will evolve from SO4-Ca·Mg type to HCO3-Ca Mg type.

Health Risk Assessment of Heavy Metals in Shallow Groundwater of Coal-Poultry Farming Districts.

This study aimed to assess the heavy metal (Mn, Ni, Cu, Zn, Sr, Cd, Pb, and Cr) pollution characteristics, sources, and human health risks in shallow groundwater in the impact zones of urban and rural semi-intensive poultry farms in Suzhou City. Ordinary kriging interpolation showed that poultry farming contributed substantially to the pollution of shallow groundwater by Mn, Zn, and Cu. Positive matrix factorization was applied to identify the sources of heavy metals, and the health risks were assessed based on the hazard index and carcinogenic risks of the various sources. Heavy metal enrichment was closely related to anthropogenic activities. In addition, four sources were identified: poultry manure (29.33%), natural source (27.94%), industrial activities (22.29%), and poultry wastewater (20.48%). The main exposure route of carcinogenic and non-carcinogenic risks to adults and children was oral ingestion. The non-carcinogenic risk of oral ingestion in children was higher than that in adults; the carcinogenic risk was higher in adults than in children. Poultry manure (42.0%) was considered the largest contributor to non-carcinogenic risk, followed by poultry wastewater (21%), industrial activities (20%), and natural sources (17%). Industrial activity (44%) was the primary contributor to carcinogenic risk, followed by poultry wastewater (25%), poultry manure (19%), and natural sources (12%).

Treatment of As(III)-Laden Contaminated Water Using Iron-Coated Carbon Fiber.

This work presents the fabrication, characterization, and application of iron-coated carbon fiber (Fe@CF), synthesized in a facile in situ iron reduction, for As(III) removal from an aqueous solution. The physico-chemical properties of the composite were characterized using Brunauer-Emmett-Teller (BET) surface area, scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier-transform infrared (FTIR) spectroscopy. Adsorption studies were evaluated in batch experiments with respect to reaction time, the dose of adsorbent, As(III) initial concentration, pH, and co-existing ions. The results showed that the BET surface area and pore volume of Fe@CF slightly decreased after Fe coating, while its pore size remained, while the SEM and XRD analyses demonstrated that the Fe was successfully anchored on the CF. A maximum As(III) adsorption of 95% was achieved with an initial As concentration of 1.5 mg/L at optimum conditions (30 min of reaction time, 1 g/L of dose, 1 mg/L of As(III) concentration, and pH 3.5). Since the treated effluents could not meet the strict discharge standard of ≤10 µg/L set by the World Health Organization (WHO), a longer reaction time is required to complete the removal of remaining As(III) in the wastewater effluents. As compared to the other adsorbents reported previously, the Fe@CF composite has the highest As(III) removal. Overall, the findings suggested that the use of Fe@CF as an adsorbent is promising for effective remediation in the aquatic environment.

Thermochemical and Toxic Element Behavior during Co-Combustion of Coal and Municipal Sludge.

The thermochemical and kinetic behavior of co-combustion of coal, municipal sludge (MS) and their blends at different ratios were investigated by thermogravimetric analysis. Simulation experiments were performed in a vacuum tube furnace to determine the conversion behavior of toxic elements. The results show that the combustion processes of the blends of coal and municipal sludge are divided into three stages and the combustion curves of the blends are located between those of individual coal and municipal sludge samples. The DTGmax of the sample with 10% sludge addition reaches a maximum at the heating rate of 20 °C/min, indicating that the combustion characteristics of coal can be improved during co-combustion. Strong interactions were observed between coal and municipal sludge during the co-combustion. The volatilization rates of toxic elements decrease with an increasing proportion of sludge in the blends during co-combustion, which indicates that the co-combustion of coal and sludge can effectively reduce the volatilization rate of toxic elements. The study reflects the potential of municipal sludge as a blended fuel and the environmental effects of co-combustion of coal and municipal sludge.

Risks Assessment Associated with Different Sources of Metals in Abandoned Soil of Zhuxianzhuang Coal Mine, Huaibei Coalfield (Anhui, China).

In this paper, the 36 topsoil (0-10 cm) samples were collected and the contents of Cr, Mn, Co, Ni, Cu, Zn, As, Cd and Pb were analyzed. The results indicated that the contents of Cu and As in all samples exceeded the soil background values of Anhui province, while the Co and Pb contents were lower than the background values. Geo-statistics and positive matrix factorization were applied to identify the sources of soil heavy metals, which were nature factor (15.7%), industrial activities (21.2%), coal mine (50.9%) and traffic emission (12.2%), respectively. The calculation results of health risk model based on positive matrix factorization model showed that coal mine activities accounted for the largest proportion of total source contribution, followed by industrial activities. In addition, compared with adults, the trend of health risk of children from four sources in three lands were same as adults, but their health risk was higher than adults.

Hydrogeochemistry of Water in Coal Measures during Grouting Treatment of Taoyuan Mine, China.

Permian coal measure sandstone fissure water (referred to as "coal measure water," that is, water in coal measures) is one of the important water sources for industrial and agricultural activities in mining areas. However, the regional high-pressure grouting, one of the most widely used floor control methods, may affect the coal measure water which is connected with limestone aquifer. This study used Taoyuan mine, a typical coal mine in Huaibei coalfield, as the research area to study the influencing mechanism of a grouting treatment on the hydrogeochemical evolution of coal measure water. The hydrogeochemical characteristics and water-rock interaction mechanism of the coal measure water before and during the treatment were evaluated using a Piper trigram, ion combination ratio, and hydrogen-oxygen stable isotope. The anions and cations in the coal measure water before and during the treatment had the same trends at SO4 2-  > HCO3 -  > Cl- and Na+ > Ca2+ > Mg2+ , respectively. Hydrochemical types of coal measure water before treatment were mainly SO4 ·Cl-Ca·Mg, SO4 ·Cl-Na, and HCO3 -Na, and during treatment they were mainly SO4 ·Cl-Na and HCO3 -Na. The formation of chemical components of coal measure water before treatment was mainly caused by carbonate dissolution, sulfate dissolution, and pyrite oxidation. During the treatment, sulfate dissolution and pyrite oxidation were the main geochemical processes, and ion exchange was enhanced. Atmospheric precipitation was the source of all water samples, and all showed an obvious 18 O drift.

Arsenic release: Insights into appropriate disposal of arsenic-loaded algae precipitated from arsenic contaminated water.

Limited information is available on arsenic (As) release from As-loaded algae precipitated from As contaminated water and its subsequently appropriate disposal. In this study, selected M. aeruginosa as algal model, changes of As concentrations and its speciation were thus investigated in the in-situ treated algae water by optimal coagulation. Meanwhile, after ex-situ disposal, As release kinetics were also examined from its precipitated algae with living and heat-treated conditions. Results showed that in the in-situ treated water, total dissolved As slowly decreased for 6 days, but arsenite increased largely after 3 days partly caused by its reduction status. While being disposed ex-situ, As release from precipitated algae depended not only on intracellular As content but also on the living or heat-treated status of algae. Additionally, potential risks arised from As release in short-term duration (24 h) from both the precipitated algae at 1.0 µM As(V) pre-exposure with the living and heat-treated conditions due to their higher release. Furthermore, As release in long-term (6 d) duration from heat-treated algae at 10.0 µM As(V) pre-exposure also resulted in potential risks. Accordingly, this study offers insights into the appropriate methods at a proper time of disposing precipitated algae with As-contamination.

Biosafety of cadmium contaminated sediments after treated by indigenous sulfate reducing bacteria: Based on biotic experiments and DGT technique.

Sulfate reducing bacteria (SRB) biostabilization has attracted particular attention due to its ability to prevent and control heavy metal pollution. In this study, biotic experiments (immobilisation test of Daphnia (D.) magna, germination experiment of cucumber seeds, and in vitro experiment using gut juices of Sipunculus (S.) nudus) and diffusive gradients in thin films (DGT) technique were performed to investigate the biosafety of cadmium (Cd) contaminated sediments after being treated by indigenous SRB. Results showed that SRB treatment reduced Cd bioaccessibility of sediment to S. nudus, Cd levels in the overlying water and Cd bioavailability to D. magna. However, the treatment increased the biotoxicity of overlying water due to significant reduction in the root length and germination index of cucumber seeds. DGT results confirmed that SRB treatment increased Cd stability in sediment, and reduced its release from the sediment into the overlying water. The biotoxicity of overlying water was not caused by Cd, but possibly by the added culture medium, SRB itself, or its metabolites. More attention is required to assess the safety of SRB treatment when it is used to remediate environmental matrix contaminated by heavy metals.

Hydrogeochemical Characteristics and Water Quality Evaluation of Carboniferous Taiyuan Formation Limestone Water in Sulin Mining Area in Northern Anhui, China.

The Taiyuan formation limestone water in the Huaibei coalfield is not only the water source for coal mining, but also the water source for industry and agriculture in mining areas. Its hydrogeochemical characteristics and water quality are generally concerning. In this paper, conventional ion tests were carried out on the Taiyuan formation limestone water of 16 coal mines in the Sunan and Linhuan mining areas of the Huaibei coalfield. Piper trigram, Gibbs diagram and an ion scale coefficient map were used to analyze the hydrogeochemical characteristics of the Taiyuan formation limestone water. The water quality was evaluated in a fuzzy comprehensive manner. The results show that the main cation and anion contents in the Taiyuan formation limestone water were Na+ > Mg2+ > Ca2+ > K+, SO42- > HCO3- > Cl-. There were differences in the hydrogeochemical types of the Taiyuan formation limestone water in the two mining areas; HCO3-Na type water was dominant in the Sunan mining area and SO4·Cl-Na type water was dominant in the Linhuan mining area. The chemical composition of the Taiyuan formation limestone water is mainly affected by the weathering of the rock and is related to the dissolution of the evaporated salt and the weathering of the silicate. The fuzzy comprehensive evaluation results show that the V-type water accounts for a large proportion of the Taiyuan formation limestone water in the study area and the water quality is poor. This study provides a basis for the development and utilization of the Taiyuan formation limestone water and water environmental protection in the future.

Dissolved organic phosphorus enhances arsenate bioaccumulation and biotransformation in Microcystis aeruginosa.

Only limited information is available on the effects of dissolved organic phosphorus (DOP) on arsenate (As(V)) bioaccumulation and biotransformation in organisms. In this study, we examined the influence of three different DOP forms (ß-sodium glycerophosphate (ßP), adenosine 5'-triphosphate (ATP), and D-Glucose-6-phosphate disodium (GP) salts) and inorganic phosphate (IP) on As(V) toxicity, accumulation, and biotransformation in Microcystis aeruginosa. Results showed that M. aeruginosa utilized the three DOP forms to sustain its growth. At a subcellular level, the higher phosphorus (P) distribution in metal-sensitive fractions (MSF) observed in the IP treatments could explain the comparatively lower toxic stress of algae compared to the DOP treatments. Meanwhile, the higher MSF distribution of arsenic (As) in M. aeruginosa in the presence of DOP could explain the higher toxicity with lower 96-h half maximal effective concentration (EC50) values. Although we observed As(V) and P discrimination in M. aeruginosa under IP treatments with high intracellular P/As, we did not find this discrimination under the DOP treatments. As accumulation in algal cells was therefore greatly enhanced by DOP, especially ßP, given its lower transformation rate to phosphate compared to ATP and GP in media. Additionally, As(V) reduction and, subsequently, As(III) methylation were greatly facilitated in M. aeruginosa by the presence of DOP, particularly GP, which was confirmed by the higher relative expression of its two functional genes (arsC and arsM). Our findings indicate that As(V) accumulation and its subsequent biotransformation were enhanced by organic P forms, which provides new insight into how DOP modulates As metabolism in algae.

Methods of determing biokinetics of arsenate accumulation and release in Microcystis aeruginosa regulated by common environmental factors: Practical implications for enhanced bioremediation.

Only little information is available on combined effects of abiotic environmental factors on algal arsenate (AsV ) metabolic biokinetics. Herein, we demonstrated the methods of using the Taguchi statistical method to investigate four environmental factors including AsV , nitrate (N), orthophosphate (P) and pH for their combined effects on algal growth and arsenic (As) uptake but also extracellular adsorption of Microcystis aeruginosa, as well as As release from dead algal cells. Results showed that an increase of N facilitated M. aeruginosa growth and thus was the principal factor for the algal maximum specific growth rate ( µmax ). P was vital to AsV bioconcentration factor (BCF) and As partition coefficients (LogKd ) released from deal algal cells. AsV impacted the extracellular As adsorption onto the algal cells, which thereby increased with increasing initial AsV level. The initial pH had an imperative effect on the AsV uptake (ku ) and release rate (Ke ) from the dead cells. Collectively, the condition of low P, high N and alkaline pH level was favorable to As accumulation rate of living cells and restrictive to As release rate from dead cells of M. aeruginosa. The obtained information can pave a road for extensive understanding on efficient utilization of As bioremediation of algae in practical environment. •Principal factors were identified on AsV metabolic biokinetics by Taguchi method.•High N and pH but low P fasten AsV uptake and reduce As efflux from dead cells.•AsV only as the main factor impacted As extracellular adsorption on algal cells.

Pollution characteristics, source apportionment, and health risk of heavy metals in street dust of Suzhou, China.

To analyze the pollution characteristics, source apportionment, and health risk of heavy metals (HMs) in street dust of Suzhou, China, 23 sampling sites were selected and periodically sampled for 12 months. A total of 276 samples were collected, and the concentrations of selected HMs (e.g., Cr, Cu, Fe, Mn, Pb, V, and Zn) were examined with an X-ray fluorescence spectrum analyzer. Results showed that the mean concentrations of Cr, Cu, Fe, Mn, Pb, V, and Zn in the street dust of Suzhou were 112.9, 27.5, 19941.3, 410.3, 45.2, 75.6, and 225.3 mg kg-1, respectively. Cr, Cu, Pb, and Zn exceeded their background values in local natural soils by 1.3-3.6-fold, whereas Fe, Mn, and V were all within their background values. However, enrichment factor analysis revealed that Cr, Cu, Mn, Pb, V, and Zn, especially Cr, Cu, Pb, and Zn, were enriched in Suzhou street dust. The HMs showed no significant seasonal changes overall, but spatial distribution analysis implied that the high values of Cr, Cu, Mn, Pb, V, and Zn were mainly distributed in areas with frequent human activities. Results of multivariate techniques (e.g., Pearson correlation, hierarchical cluster, and principal components analyses) suggested that Pb and Zn had complicated sources; Cu and V mainly originated from traffic sources; Fe and Mn mainly came from natural sources; and Cr was dominantly related to industrial district. Health risk assessment revealed that a single heavy metal might not cause both non-cancer and carcinogenic risks to local residents. Nevertheless, the sum of the hazard index of all selected HMs for children slightly exceeded the safety value, thereby implying that the HMs from Suzhou street dust can possibly produce significant risk to children. Cr was the priority pollutant in the study area because of its high concentration, high enrichment, and high contribution to non-cancer risk values.

Hydrochemical characteristics and quality assessment of deep groundwater from the coal-bearing aquifer of the Linhuan coal-mining district, Northern Anhui Province, China.

There is little information available about the hydrochemical characteristics of deep groundwater in the Linhuan coal-mining district, Northern Anhui Province, China. In this study, we report information about the physicochemical parameters, major ions, and heavy metals of 17 groundwater samples that were collected from the coal-bearing aquifer. The results show that the concentrations of total dissolved solids, electrical conductivity, and potassium and sodium (K(+) + Na(+)) in most of the groundwater samples exceeded the guidelines of the World Health Organization (WHO) and the Chinese National Standards for Drinking Water Quality (GB 5749-2006). The groundwater from the coal-bearing aquifer was dominated by the HCO3·Cl-K + Na and HCO3·SO4-K + Na types. Analysis with a Gibbs plot suggested that the major ion chemistry of the groundwater was primarily controlled by weathering of rocks and that the coal-bearing aquifer in the Linhuan coal-mining district was a relatively closed system. K(+) and Na(+) originated from halite and silicate weathering reactions, while Ca(2+) and Mg(2+) originated from the dissolution of calcite, dolomite, and gypsum or anhydrite. Ion exchange reactions also had an influence on the formation of major ions in groundwater. The concentrations of selected heavy metals decreased in the order Mn > Zn > Cr > Cu > Ni > Pb. In general, the heavy metal concentrations were low; however, the Cr, Mn, and Ni concentrations in some of the groundwater samples exceeded the standards outlined by the WHO, the GB 5749-2006, and the Chinese National Standards for Groundwater (GB/T 14848-93). Analysis by various indices (% Na, SAR, and EC), a USSL diagram, and a Wilcox diagram showed that both the salinity and alkalinity of the groundwater were high, such that the groundwater could not be used for irrigating agricultural land without treatment. These results will be significant for water resource exploiting and utilization in coal mine area.

Monitoring of flow field based on stable isotope geochemical characteristics in deep groundwater.

The water circulation in deep aquifers controls not only chemical composition of the groundwater, but also stable isotope composition. In order to analyze the flow field in the process of the deep groundwater circulation in different aquifers, specimens belonging to the fourth aquifer in the Quaternary (the fourth aquifer for short), the coal and sandstone cranny aquifer in the Permian, and Carboniferous (the coal catena aquifer for short), the Taiyuan group limestone aquifer in the Carboniferous (the Taiyuan limestone aquifer for short), and the limestone aquifer in the Ordovician (the Ordovician limestone aquifer for short) were gained from the top down in Renlou colliery and local Linhuan coalmine district, northern Anhui, China, in the study. δD, δ(18)O, and the content of tall dissolve solids (TDS for short) of these specimens were tested. The experimental results had revealed that the groundwater in the fourth aquifer and the Taiyuan limestone aquifer takes on (18)O excursion and the coal catena aquifer takes on D excursion in Linhuan coalmine district, while excursion characteristic in the Ordovician limestone aquifer is not evident in the coalmine district. By analysis, δ(18)O and the content of TDS are in negative relationship in the groundwater of the fourth aquifer and the Taiyuan limestone aquifer in Linhuan coalmine district, yet δD and the content of TDS are in positive relationship in the coal catena aquifer. Mining greatly influences the fourth aquifer and the coal catena aquifer so the groundwater in the fourth aquifer flows from northwest and southeast to mining areas and the groundwater in the coal catena aquifer flows from around to mining areas. However, mining does not influence the Taiyuan limestone aquifer evidently so the groundwater flows from east to west still.