A new exploration of health risk assessment quantification from sources of soil heavy metals under different land use.

Heavy metals in the topsoil affected adversely human health through inhalation, ingestion and dermal contact. The health risk assessment, which are quantified from soil heavy metals sources under different land use, can provide an important reference basis for preventing and controlling the soil heavy metals pollution from the source. In this study, simple statistical analysis and Positive Matrix Factorization (PMF) were used to quantify sources of soil heavy metals; then a health risk assessment (HRA) model combined with PMF was proposed to assess quantificationally the human health risk (including non-cancer risk and cancer risk) from sources under residential-land, forest-land and farm land. Xiang River New District (XRNQ) was chosen as the example and four significant sources were quantitatively analyzed in the study. For cancer risk, industrial discharge was the largest source and accounted for about 69.6%, 69.7%, 56.5% for adults under residential-land, forest-land and farm-land, respectively. For non-cancer risk, industrial discharge was still the largest significant source under residential-land and forest-land and accounted for about 41.7%, 39.2% for adult, respectively; while agricultural activities accounted for about 51.8% for adult under farm-land. The risk trend of children, including cancer risk and non-cancer risk, was similar with adults. However, the non-cancer risk areas of adults affected by industrial discharge was higher than that of children, while the cancer risk areas of adults were on the contrary. The new exploration was useful to assess health risk quantification from sources under different land use, thus providing certain reference in preventing and controlling the pollution from the source for local authorities effectively.

An exploration of an integrated stochastic-fuzzy pollution assessment for heavy metals in urban topsoil based on metal enrichment and bioaccessibility.

An integrated stochastic-fuzzy pollution assessment method (ISFPAM) for soil heavy metal was established based on geo-accumulation index (Igeo), stochastic-fuzzy theory and double weight system under synthetical consideration of metal ecotoxicity and bioaccessibility. The pollution characteristics of the topsoil heavy metals (Cu, Zn, Cd, Pb and Cr) in Xiangjiang New District were evaluated by the widely-used Single factor index (SF), Nemerow index (NI), Igeo, Potential ecological index (PERI), Risk assessment code (RAC) and the ISFPAM. The results of SF, NI, Igeo, RI and RAC of the studied metals revealed the following orders: Cd > Zn > Cr > Cu > Pb, Cd > Zn > Pb > Cr > Cu, Cd > Cr > Cu > Zn > Pb, Cd > Cu > Pb > Cr > Zn, and Cd > Pb > Cr > Zn > Cu, respectively. The different pollution assessment methods outputted the differentiated conclusions to some extent except the judgment for Cd. Results based on ISFPAM indicated that metal pollution degrees decreased in the order of Cd (5.91, Grade 6) > Cu (2.81, Grade 3) > Pb (2.66, Grade 3) > Cr (1.58, Grade 2) > Zn (0.69, Grade 1). By detailed comparison analysis, the double weight system and stochastic-fuzzy theory made ISFPAM better resolving ability to find out priority heavy metals and areas with relatively higher enrichment, ecotoxicity and bioaccessibility under efficient parameter uncertainty control. Cd, Cu and Pb were regarded as the priority control metals, especially Cd. Simultaneously, the reliabilities of heavy metal pollution corresponding to adjacent pollution grades were quite close in some sites, which recommend recheck for avoid misleading the decision-makers.

Investigation, Pollution Mapping and Simulative Leakage Health Risk Assessment for Heavy Metals and Metalloids in Groundwater from a Typical Brownfield, Middle China.

Heavy metal and metalloid (Cr, Pb, Cd, Zn, Cu, Ni, As and Hg) concentrations in groundwater from 19 typical sites throughout a typical brownfield were detected. Mean concentrations of toxic metals in groundwater decreased in the order of Cr > Zn > Cu > Cd > Ni > Pb > Hg > As. Concentration of Cr6+ in groundwater was detected to further study chromium contamination. Cr6+ and Cd in groundwater were recommended as the priority pollutants because they were generally 1399-fold and 12-foldgreater than permissible limits, respectively. Owing to the fact that a waterproof curtain (WPC) in the brownfield is about to pass the warranty period, a steady two-dimensional water quality model and health risk assessment were applied to simulate and evaluate adverse effects of Cr6 + and Cd on the water quality of Xiangjiang River and the drinking-water intake of Wangcheng Waterworks. The results indicated that when groundwater in the brownfield leaked with valid curtain prevention, the water quality in Xiangjiang River and drinking-water intake downstream were temporarily unaffected. However, if there was no curtain prevention, groundwater leakage would have adverse impact on water quality of Xiangjiang River. Under the requirements of Class III surface water quality, the pollution belt for Cr6+ was 7500 m and 200 m for Cd. The non-carcinogenic risk of toxic metals in Xiangjiang River exceeded the threshold in a limited area, but did not threaten Wangcheng Waterworks. By contrast, the carcinogenic risk area for adults was at a transverse distance of 200 m and a longitudinal distance of 18,000 m, which was close to the Wangcheng Waterworks (23,000 m). Therefore, it was essential to reconstruct the WPC in the brownfield for preventing pollution diffusion.

Influence of pH on heavy metal speciation and removal from wastewater using micellar-enhanced ultrafiltration.

pH plays an important role in heavy metal removal during micellar-enhanced ultrafiltration (MEUF). In the present work, the influence of pH on heavy metal speciation and removal from wastewater by MEUF was investigated using an anionic surfactant (sodium dodecyl sulfate, SDS) and a hydrophilic membrane (polyether sulfone). Experiments were performed with pH values in the range of 1-12. Metal ion removal efficiency (R) was used to assess the effects of the MEUF process. Results showed that better removal rate of copper and cadmium was achieved at high pH values (pH > 3) with SDS feed concentration of 8 mM, while the optimal pH range was 3-10 for zinc and lead. The corresponding efficiencies for heavy metal removal decreased with the increasing feed concentration of metal ions under the pH conditions of 1-12. Furthermore, the heavy metal ion removal rate (50 mg/L) followed the order of Pb2+ > Cd2+ > Zn2+ > Cu2+. These results showed that pH is a key parameter in metal ion speciation and removal during MEUF.

An exploration of spatial human health risk assessment of soil toxic metals under different land uses using sequential indicator simulation.

A modified method was proposed which integrates the spatial patterns of toxic metals simulated by sequential indicator simulation, different exposure models and local current land uses extracted by remote-sensing software into a dose-response model for human health risk assessment of toxic metals. A total of 156 soil samples with a various land uses containing farm land (F1-F25), forest land (W1-W12) and residential land (U1-U15) were collected in a grid pattern throughout Xiandao District (XDD), Hunan Province, China. The total Cr and Pb in topsoil were analyzed. Compared with Hunan soil background values, the elevated concentrations of Cr were mainly located in the east of XDD, and the elevated concentrations of Pb were scattered in the areas around F1, F6, F8, F13, F14, U5, U14, W2 and W11. For non-carcinogenic effects, the hazard index (HI) of Cr and Pb overall the XDD did not exceed the accepted level to adults. While to children, Cr and Pb exhibited HI higher than the accepted level around some areas. The assessment results indicated Cr and Pb should be regarded as the priority pollutants of concern in XDD. The first priority areas of concern were identified in region A with a high probability (>0.95) of risk in excess of the accepted level for Cr and Pb. The areas with probability of risk between 0.85 and 0.95 in region A were identified to be the secondary priority areas for Cr and Pb. The modified method was proved useful due to its improvement on previous studies and calculating a more realistic human health risk, thus reducing the probability of excessive environmental management.

Integrating hierarchical bioavailability and population distribution into potential eco-risk assessment of heavy metals in road dust: A case study in Xiandao District, Changsha city, China.

Modified eco-risk assessment method (MEAM) integrated with the hierarchical bioavailability determined by the fraction detection of Cd, Pb, Zn, Cu, Cr in road dust samples and the local population distribution derived from the local land use map, was proposed to make the hierarchical eco-risk management strategy in Xiandao District (XDD), China. The geo-accumulation index (Igeo), the original potential eco-risk index (Er(i)) and the modified eco-risk assessment index (MEAI) were used to identify the priority pollutant. Compared with the Hunan soil background values, evaluated metal concentrations were found to different extent. The results of mean Igeo, Er(i) and bioavailability of studied metals revealed the following orders: Cd>Pb ≈ Zn>Cu ≈ Cr, Cd>Pb>Cu>Cr>Zn and Cd>Zn>Cu ≈ Pb>Cr, respectively. Therefore, Cd was regarded as the priority pollutant. To identify the priority areas taking into account cost consideration, the hierarchical risk map based on the results of the modified eco-risk assessment index with overlay of the population density map was needed and made. The west and partly south areas of XDD were under higher eco-risk generally. Moreover, the whole XDD area was divided into 4 area categories with different management priorities based on the possibility of occurrence of eco-risk, and the hierarchical risk management strategy associated with protecting local population was suggested to facilitate allocation of funds for risk management.

Toxic metals in topsoil under different land uses from Xiandao District, middle China: distribution, relationship with soil characteristics, and health risk assessment.

To explore mutual relationship among soil characteristics (soil organic matter, soil texture, cation exchange capacity, and pH), land uses, toxic metal (As, Hg, Mn, and Ni) distributions and induced health risk, 156 topsoil samples (0-20 cm) were collected from farm land, forest land and construction land in a grid pattern throughout Xiandao District. Compared with Hunan soil background values, the elevated concentrations of As, Hg and Ni were found to different extent. Pearson correlation matrix suggested As-silt, Mn-Ni, CEC-Mn, CEC-Ni, and CEC-pH had significantly positive correlation, and significantly negative correlation existed in SOM-pH, CEC-clay, SOM-Ni, and SOM-pH. Results based on the soil texture analysis, analysis of variance, and Tukey test indicated the concentrations of As and Ni were higher in relatively fine textures, and the mean contents of As, Mn, Ni, pH, and SOM in construction land, construction land, construction land, forest land, and construction land, respectively, were with the significant difference from that in the other two land uses. For non-carcinogenic effects, Hazard Indexes (HIs) of Ni, Hg, Mn, and As decreased in the order of As > Hg > Mn > Ni to both children and adults. Risk contributions of each exposure pathway decreased in the order of ingestion > dermal contact > inhalation of resuspended particles for HI(As), HI(Mn), and HI(Ni). The inhalation of vapors was the highest contributor for HI(Hg), followed by ingestion, dermal contact, and inhalation of resuspended particles. As and Hg were regarded as the priority pollutants. The hierarchical risk areas were identified after comprehensive consideration of local residential population density distribution, and the different risk management measures were finally suggested for the different priority areas.

Spatial distribution and health risk assessment of toxic metals associated with receptor population density in street dust: a case study of Xiandao District, Changsha, Middle China.

Spatial characteristics of the properties (dust organic material and pH), concentrations, and enrichment levels of toxic metals (Ni, Hg, Mn and As) in street dust from Xiandao District (Middle China) were investigated. Method of incorporating receptor population density into noncarcinogenic health risk assessment based on local land use map and geostatistics was developed to identify their priority pollutants/regions of concern. Mean enrichment factors of studied metals decreased in the order of Hg ≈ As > Mn > Ni. For noncarcinogenic effects, the exposure pathway which resulted in the highest levels of exposure risk for children and adults was ingestion except Hg (inhalation of vapors), followed by dermal contact and inhalation. Hazard indexes (HIs) for As, Hg, Mn, and Ni to children and adults revealed the following order: As > Hg > Mn > Ni. Mean HI for As exceeded safe level (1) for children, and the maximum HI (0.99) for Hg was most approached the safe level. Priority regions of concern were indentified in A region at each residential population density and the areas of B at high and moderate residential population density for As and the high residential density area within A region for Hg, respectively. The developed method was proved useful due to its improvement on previous study for making the priority areas of environmental management spatially hierarchical and thus reducing the probability of excessive environmental management.