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.

Seasonal changes of heavy metals and health risk assessment based on Monte Carlo simulation in alternate water sources of the Xinbian River in Suzhou City, Huaibei Plain, China.

The urban alternate water source (AWS) is of great significance to the sustainable development of the city, the pollution degree, and source of heavy metals (HMs) in AWS, and whether it will adversely affect human health has received widespread attention. In this study, the urban AWS of Xinbian River in Suzhou City, Huaibei Plain, China, was used as the research object to study the seasonal changes of HMs (As, Cr, Cu, Cd, Pb, and Zn), quantitative identification of pollution sources, and human health risks (HHR). Research results show that the contents of those HMs, except As, are less than the drinking standards limit set by the World Health Organization (WHO), and the contents of As, Cr, and Zn are the largest in summer. The multivariate statistical analysis combined with positive matrix factorization (PMF) model analysis revealed that industrial sources accounted for 44.83%, and agricultural sources accounted for 55.17%. HHR assessment based on Monte Carlo simulation shows that the noncarcinogenic risks of adults and children are in the acceptable range (hazardous ingestion (HI) < 1), and the probability of carcinogenic risk values of children and adults are 95.03% and 38.96%, respectively, which are exceed the acceptable range (1 × 10-4) recommended by the United States Environment Protection Agency (USEPA). Approximately 30.75% of the carcinogenic risk value of agricultural source HMs to children exceeds the acceptable range (1 × 10-4). The above research results indicate that the effect of agricultural non-point source pollution on AWS should be prevented.

Effects of multi-factors on the spatiotemporal variations of deep confined groundwater in coal mining regions, North China.

Natural processes and anthropogenic activities simultaneously control the long-term spatial and temporal variations of groundwater hydrogeochemistry in coalfields. In this study, the spatiotemporal variations and primary controlling factors of deep groundwater hydrogeochemistry in the Carboniferous limestone aquifer of the Huaibei coalfield, North China were investigated using cluster analysis combined with geological conditions, water-rock interactions and mining activities. The analysis data of 176 groundwater samples collected over five years from 20 monitoring wells were subdivided into six clusters through hierarchical cluster analysis. Moreover, principal component analysis, box plots and Piper and Stiff diagrams were employed to analyze the statistical and hydrogeochemical characteristics of each cluster, and to reveal the differences and connections between the clusters. The results show that there are significantly spatial variations in groundwater hydrogeochemistry, while the temporal variations are not evident with only a few notable exceptions. Geological conditions dominate the groundwater hydrogeochemistry by controlling the hydraulic connection between groundwater and meteoric water and the flow conditions of groundwater. Moreover, the types and degrees of diverse water-rock interactions in different regions are another important factor controlling the spatial variations of groundwater hydrogeochemistry. Anthropogenic activities are mainly pumping and drainage, which has led to the overall decline in groundwater levels and the temporal variations of hydrogeochemistry in some zones. The findings of this study not only have important implications for deep groundwater resources management in the Huaibei coalfield, but also provide a research template for other highly exploited coalfields in North China.

Multi-isotopes and hydrochemistry combined to reveal the major factors affecting Carboniferous groundwater evolution in the Huaibei coalfield, North China.

Both natural processes and anthropogenic activities have significant effects on groundwater evolution in coal mining regions. In this study, the primary controlling mechanism of the groundwater chemistry evolution for the Carboniferous groundwater in the Huaibei coalfield, North China was proposed based on the hydrogeochemical indicators combining with multiple isotope tracers. The diversity of hydrochemical types indicates the complexity of the hydrogeochemical environment in the groundwater, which is recharged by precipitation infiltration with minimal evaporation according to the distributions of δD and δ18O. Additionally, ion correlation analysis suggests that minerals dissolution and cation exchange between Na+ and Ca2+ are the dominant processes within that groundwater. The hydrochemical and δ13CDIC characteristics of the groundwater demonstrate that HCO3- is mainly controlled by the dissolution of carbonate minerals and soil CO2, and the proportion of the latter is believed to be dominated by the hydrogeologic conditions. Similarly, the values of SO42- and δ34SSO4 indicate that a small portion of SO42- in the groundwater in the northern part originates from the meteoric precipitation, while it is mainly derived from the dissolution of gypsum in the southern part. Furthermore, mining activities also alter the groundwater level and flow conditions through pumping and drainage, which enhances the interaction between groundwater and aquifer lithologies, thereby affects the hydrogeochemical processes. The findings of this work are of great significance for promoting the safe exploitation of deep coal resources and the sustainable utilization of groundwater in the Huaibei coalfield, as well as the most of other coalfields in North China.

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.

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.

A methylation-blocked cascade amplification strategy for label-free colorimetric detection of DNA methyltransferase activity.

DNA methyltransferase (MTase), catalyzing DNA methylation in both eukaryotes and prokaryotes, is closely related with cancer and bacterial diseases. Although there are various methods focusing on DNA MTase detection, most of them share common defects such as complicated setup, laborious operation and requirement of expensive analytical instruments. In this work, a simple strategy based on methylation-blocked cascade amplification is developed for label-free colorimetric assay of MTase activity. When DNA adenine methylation (Dam) MTase is introduced, the hairpin probe is methylated. This blocks the amplified generation of G-riched DNAzyme by nicking endonuclease and DNA polymerase, and inhibits the DNAzyme-catalyzed colorimetric reaction. Contrarily, an effective colorimetric reaction is initiated and high color signal is clearly observed by the naked eye in the absence of Dam MTase. A satisfying sensitivity and high selectivity are readily achieved within a short assay time of 77 min, which are superior to those of some existing approaches. Additionally, the application of the sensing system in human serum is successfully verified with good recovery and reproducibility, indicating great potential for the practicality in high concentrations of interfering species. By using several anticancer and antimicrobial drugs as model, the inhibition of Dam MTase is well investigated. Therefore, the proposed method is not only promising and convenient in visualized analysis of MTase, but also useful for further application in fundamental biological research, early clinical diagnosis and drug discovery.