Soil pollution with heavy metals (HMs) has been attracting more and more interests, however, assessment of eco-environmental and human risks particularly in a rapidly urbanization area (the upper ...Yangtze) remains limited. Multiple modern indices were firstly performed for complete risk assessment of eco-environment and human health based on a high-spatial-resolution sampling. Averages of HMs were far below grade II threshold level of the Chinese Environmental Quality standards for soils, whereas Cd, As and Hg considerably exceeded the local background values. EF suggested overall moderate enrichments of Cd and Se, resulting in soils uncontaminated to moderately contaminated with them. Potential ecological risk index showed significant differences among Counties that were characterized by moderate risk. However, several sites were moderately to heavily contaminated with As, Cd and Hg by Igeo, resulting in that these sites were categorized as "considerable risk", or "high risk". Moreover, children were more susceptible to the potential health risk irrespective of the carcinogenic or non - carcinogenic risk. There were no significant carcinogenic and non - carcinogenic risks for adults, children however showed significant non - carcinogenic effect. Our first assessment provided important information for policy making to reduce the potential effects of soil contamination on human and eco-environment.
Surface water samples were collected from 42 sampling sites throughout the upper Han River during the time period of 2005–2006. The concentrations of trace metals were determined using inductively ...coupled plasma-atomic emission spectrometry (ICP-AES) for the seasonal variability and preliminary risk assessment. The results demonstrated that concentrations of 11 heavy metals showed significant seasonality and most variables exhibited higher levels in the rainy season. Principal component analysis (PCA) and factor analysis (FA) revealed that variables governing water quality in one season may not be important in another season. Risk of metals on human health was then evaluated using Hazard Quotient (HQ) and carcinogenic risk, and indicated that As with HQ >1 and carcinogenic risk >10
−4, was the most important pollutant leading to non-carcinogenic and carcinogenic concerns, in particular for children. The first five largest elements to chronic risks were As, Pb, V, Se and Sb, in the dry season, while they were As, V, Co, Pb and Sb in the rainy season. This assessment would help establish pollutant loading reduction goal and the total maximum daily loads, and consequently contribute to preserve public health in the Han River basin and develop water conservation strategy for the interbasin water transfer project.
Soil heavy metal pollution now is a major environmental concern in China particularly in some rapidly developing areas with intensified agricultural practices. High-spatial-resolution sampling (1664 ...surface (0–20cm) and 416 deep (150–200cm) soil samples) was undertaken in four typical agricultural Counties of Municipality Chongqing (SW China) and consequently eight priority heavy metals (HMs; As, Cd, Cr, Cu, Hg, Ni, Pb and Zn) and other elements were measured. Classic and advanced multivariate statistics and multi-linear regression with factor analysis (FA-MLR) receptor modeling were applied for characterization and sources apportionment of HMs in soils. There was notably spatial variability in eight priority HMs with the mean concentrations decreasing as follows: Zn>Cr>Ni>Pb>Cu>As>Cd>Hg. Soil contamination was enhanced by As, Cd, Cr, while obvious enrichment of Cd and Hg in surface soils in comparison with deep soils should be noted. We revealed dominant anthropogenic contributions (64%–90%) of metal - bearing industrial emission, fuel consumption and agriculture to certain HMs, while the abundant elements of Si, Al and Fe were natural in origin. Our study will be helpful for improving soil environment and strengthening the capacity of multivariate statistic techniques and models in soil pollution research.
Four enriched heavy metals in both top and deep soils. Display omitted
•Receptor model provides apportionment of various sources to soil pollution.•Soil heavy metal contamination is enhanced by As, Cd and Cr.•Cd and Hg are obviously enriched in surface soils relative to deep soils.•Metal - bearing industry, fuel consumption and agriculture are primary sources.•Anthropogenic activities contribute up to 64–90% of certain heavy metals.
A data matrix (4032 observations), obtained during a 2-year monitoring period (2005–2006) from 42 sites in the upper Han River is subjected to various multivariate statistical techniques including ...cluster analysis, principal component analysis (PCA), factor analysis (FA), correlation analysis and analysis of variance to determine the spatial characterization of dissolved trace elements and heavy metals. Our results indicate that waters in the upper Han River are primarily polluted by Al, As, Cd, Pb, Sb and Se, and the potential pollutants include Ba, Cr, Hg, Mn and Ni. Spatial distribution of trace metals indicates the polluted sections mainly concentrate in the Danjiang, Danjiangkou Reservoir catchment and Hanzhong Plain, and the most contaminated river is in the Hanzhong Plain. Q-model clustering depends on geographical location of sampling sites and groups the 42 sampling sites into four clusters, i.e., Danjiang, Danjiangkou Reservoir region (lower catchment), upper catchment and one river in headwaters pertaining to water quality. The headwaters, Danjiang and lower catchment, and upper catchment correspond to very high polluted, moderate polluted and relatively low polluted regions, respectively. Additionally, PCA/FA and correlation analysis demonstrates that Al, Cd, Mn, Ni, Fe, Si and Sr are controlled by natural sources, whereas the other metals appear to be primarily controlled by anthropogenic origins though geogenic source contributing to them.
Sedimentary deposits often display a variety of grains and especially in gap graded materials or soil mixtures, it is expected that the finer particles may develop a coating in the contact region of ...coarser particles. Development of coatings in the vicinity of the contacts of coarser grains may also be encountered due to increase in depth and pressure which cause breakage of grain asperities forming in this way smaller particles which interact with larger grains and coatings may also influence reservoir quality. As the interactions of grains at their contacts have a significant influence on the mechanical, geophysical, hydraulic and thermal properties of sediments, it is essential to be examined in the laboratory through grain-scale tests to provide insights into their behaviour. In the present study, a new technique was developed in coating sand grains with siliciclastic non-plastic powder and emphasis was placed in the assessment of the mechanical behaviour of the specimens, comparing them with plastic-coated grains. The experiments were performed with grain-scale methods and were further supported with direct shear tests. The results showed that different frictional mechanisms involve in non-plastic coated grain contacts compared with the case of plastic coatings and that the influence of loading history played an important role on the tribological behaviour of the grains. Microcrushing and rearrangement of the siliciclastic non-plastic coating were the major contributing mechanisms, and their influence was found to be dependent on the magnitude of the applied normal load, which was not the case of plastic-coated grains. The results from the study provide fundamental understanding on the role of the type of natural coatings on the interface behaviour of sediments and highlight the important differences at the grain-scale between sand-silt and sand-clay mixtures.
•Quartz grains were studied in the presence of siliciclastic coatings with micro-scale tests.•Siliciclastic coating had a very different influence compared with plastic-based coatings.•Particle crushing and rearrangement were the major mechanisms contributing to friction.•The influence of grain-scale properties is important in the study of sediment behaviour.•Multi-scale studies provided additional insights into the behaviour of sedimentary materials.
Guided by the frameworks of the social identity model of deindividuation effects (SIDE) and the intergroup sensitivity effect, this experiment examined whether and how group identification manifested ...in user avatars, along with the supportiveness of others’ comments to a support-seeking post, may affect people’s support provision online. Participants were given the option to reply to a support-seeking post in an interactive forum. Participants’ responses were coded for verbal person-centeredness (VPC) and action-focused supportiveness. The SIDE model received some support. The results suggested that more participants replied to a support-seeking message posted by an in-group than by an out-group. Participants provided higher levels of action-focused supportiveness after viewing supportive comments from in-groups than from out-groups. They also provided messages with lower levels of VPC when exposed to unsupportive comments from in-groups than from out-groups. The intergroup sensitivity effect did not receive strong support. The implications of the study are discussed.
► We assess heavy metal pollution in the water level fluctuation zone of the Three Gorges Reservoir. ► There are higher concentrations of As, Cd, Pb, Cu, and Zn in the upper and low reaches. ► As and ...Cd are the primary pollutants originated from domestic sewage and industrial wastes before submergence. ► The major contaminants are Hg, Cd, and Pb with primary contribution from traffic exhaust and industrial effluent after submergence.
The water-level-fluctuation zone (WLFZ) between the elevations of 145–175
m in China's Three Gorges Reservoir has experienced a novel hydrological regime with half a year (May–September) exposed in summer and another half (October–April) submerged in winter. In September 2008 (before submergence) and June 2009 (after submergence), soil samples were collected in 12 sites in the WLFZ and heavy metals (Hg, As, Cr, Cd, Pb, Cu, Zn, Fe, and Mn) were determined. Enrichment factor (EF), factor analysis (FA), and factor analysis-multiple linear regression (FA-MLR) were employed for heavy metal pollution assessment, source identification, and source apportionment, respectively. Results demonstrate spatial variability in heavy metals before and after submergence and elements of As, Cd, Pb, Cu, and Zn are higher in the upper and low reaches. FA and FA-MLR reveal that As and Cd are the primary pollutants before submergence, and over 45% of As originates from domestic sewage and 59% of Cd from industrial wastes. After submergence, the major contaminants are Hg, Cd, and Pb, and traffic exhaust contributes approximately 81% to Hg and industrial effluent accounts about 36% and 73% for Cd and Pb, respectively. Our results suggest that increased shipping and industrial wastes have deposited large amounts of heavy metals which have been accumulated in the WLFZ during submergence period.
► We assess riverine water quality along the water conveyance systems. ► Multivariate statistics reveal remarkable spatio-temporal variations in water quality. ► Waters are more polluted due to ...increasing industrial effluents northward. ► CA and total factor scores vs sampling sites generate 3 significant categories. ► FA-MLR indicates more anthropogenic contributions to rivers in Beijing and Tianjin.
A total of 190 grab water samples were collected from 19 rivers along the water conveyance system of the Middle Route of China's interbasin South to North Water Transfer Project (MRSNWTP). Multivariate statistics including principal component/factor analysis (PCA/FA), analysis of variance (ANOVA), and cluster analysis (CA) were employed to assess water quality, and the receptor model of factor analysis-multiple linear regression (FA-MLR) was used for source identification/apportionment of pollutants from natural processes and anthropogenic activities to river waters. Our results revealed that river waters were primarily polluted by COD
Mn, BOD, NH
4
+-N, TN, TP, and Cd with remarkably spatio-temporal variability, and there were increasing industrial effluents in rivers northward. FA/PCA identified four classes of water quality parameters, i.e., mineral composition, toxic metals, nutrients, and organic pollutants. CA classified the selective 19 rivers into three groups reflecting their varying water pollution levels of moderated pollution, high pollution, and very high pollution. The FA-MLR receptor modeling revealed predominantly anthropogenic inputs to river solutes in Beijing and Tianjin, i.e., 77% of nitrogen and 90% of phosphorus from industry, and 80% of COD
Mn from domestics. This study is critical for water allocation and division in the water-receiving areas using the existing rivers for MRSNWTP.
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•pCO2, DOC, nutrients and Chl-a levels increase with the increasing urban coverage.•The pCO2 overall is positively correlated with nutrients, Chl-a, DOC and CFU.•pH and DOC predict ...pCO2 well in river with higher urban cover.•pH and Chl-a predict pCO2 well in river with lower urbanization.•Interaction of abiotic and biotic factors controls variations and key drivers of pCO2.
Rapid urbanization has been reported to affect carbon biogeochemical cycle of waterways, contributing to even higher carbon dioxide (CO2) outgassing from rivers to the atmosphere. However, knowledge on the magnitude and extent of the urbanization influence on riverine CO2 dynamics is still limited. In this study, we investigated partial pressure of CO2 (pCO2) and CO2 degassing rate in the surface water of three rivers that drain land areas with varied urban coverages. Field sampling and measurements were conducted in the Taohua, Nan and Puli Rivers in China’s mountainous Three Gorges Reservoir (TGR) area during winter 2018 and summer 2019 to determine the effect of urbanization intensity on riverine CO2 degassing. We found that pCO2 level was significantly higher in the river with increased proportion of urban land. Both pCO2 level and CO2 flux rate of the Taohua River (3872 μatm and 574 mmol m−2 d−1) with the highest urban land coverage were significantly higher than those of the Nan River (1737 μatm and 218 mmol m−2 d−1) and Puli River (1218 μatm and 130 mmol m−2 d−1) that drain less urbanized land areas. No significant seasonal difference in pCO2 was found in these subtropical rivers (2402 ± 1421 vs 2112 ± 1254 μatm in the summer and the winter). Overall, pCO2 was positively correlated with the concentration of chlorophyll-a (Chl-a), nutrients (i.e., TDN and TDP), dissolved organic carbon (DOC) and colony-forming units (CFU), and was negatively correlated with pH and dissolved oxygen (DO). We found that pH and DOC loading were the better parameters for predicting pCO2 in the river draining more urbanized land area, and pH and Chl-a were the better parameters for predicting pCO2 in the river draining less urbanized area. These findings highlight the role that urbanization plays in increasing riverine pCO2 through increasing nutrient and DOC inputs from the drainage basin under urban development.
We investigated experimentally the tribological behavior of tailing grain contacts using a micromechanical apparatus which allows high precision of force and displacement measurements to derive ...contact stiffness. A technique was developed to apply biopolymer coating to the grain surfaces and the emphasis of the study was placed on the investigation of the influences of saturation conditions, the presence of polymer-based coating, and the abrasion on the frictional behavior of the grains. Material characterization was based on interferometry, micro-indentation and elemental composition analyses. Elastoplastic displacements dominated the first cycles of normal loading and the Young’s modulus was interpreted based on different contact models. The tailing grains showed significantly higher inter-particle friction compared with that of quartz grains. Three major characteristics which influenced the frictional behavior of the grain contacts were the abrasion, which was more dominant in the first loading cycles, the high roughness of the grains and the presence of the biopolymer coating which increased significantly the friction.
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