Quanfa Zhang

Risk assessment and seasonal variations of dissolved trace elements and heavy metals in the Upper Han River, China.

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.

Assessing soil heavy metal pollution in the water-level-fluctuation zone of the Three Gorges Reservoir, China

The water-level-fluctuation zone (WLFZ) between the elevations of 145-175 m in Chinas 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.

Spatial characterization of dissolved trace elements and heavy metals in the upper Han River (China) using multivariate statistical techniques

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.

Temporal and spatial variations of water quality in the Jinshui River of the South Qinling Mts., China

Water pollution has become a growing threat to human society and natural ecosystems in recent decades, increasing the need to better understand the spatial and temporal variabilities of pollutants within aquatic systems. This study sampled water quality at 12 sampling sites from October 2006 to August 2008 in the Jinshui River of the South Qinling Mts., China. Multivariate statistical techniques and gridding methods were used to investigate the temporal and spatial variations of water quality and identify the main pollution factors and sources. Two-way analysis of variance (ANOVA) showed that 25 studied water quality variables had significant temporal differences (p<0.01) and spatial variability (p<0.01). Using cluster analysis, the 12 sampling sites were classified into three pollution level groups (no pollution, moderate pollution, and high pollution) based on similarity of water quality variables. Factor analysis determined that 80.4% of the total variance was explained by five factors, that is, salinity, trophicity, organic pollution, oxide-related process, and erosion. The gridding methods illustrated that water quality progressively deteriorated from headwater to downstream areas. The analytical results suggested that the water pollution primarily resulted from domestic wastewater and agricultural runoff, and provided critical information for water resource conservation in mountainous watersheds of the South Qinling Mts., China.

Spatio-temporal dynamics of nutrients in the upper Han River basin, China

The upper Han River basin with an area of approximately 95,000 km(2), is the water source area of the Middle Route of Chinas South to North Water Transfer Project. Thus, water quality in the basins river network is of great importance. Nutrients including dissolved inorganic nitrogen (DIN), NO(3)(-)-N, NH(4)(+)-N, and dissolved phosphorus (DP) were analyzed in 41 sites during the period of 2005-2006. Cluster analysis (CA), analysis of variance (ANOVA) and general linear models (GLM) were performed to explore their spatio-temporal variations in the basin. The results revealed that the DIN, NO(3)(-)-N and NH(4)(+)-N increased over the 2 year study period, and their concentrations in the wet season was higher than those in the dry season. The seasonal variation in nitrogen was strongly associated with seasonal pattern of precipitation and there was a negative relationship between DP concentration and river flow. Cluster analysis indicated high nutrient contents in the urban and agricultural production areas. The research will help articulate water resource management strategy for the interbasin water transfer project.

Lake eutrophication associated with geographic location, lake morphology and climate in China

Lake eutrophication is influenced by both anthropogenic and natural factors. Few studies have examined relationships between eutrophication parameters and natural factors at a large spatial scale. This study explored these relationships using data from 103 lakes across China. Eutrophication parameters including total nitrogen (TN), total phosphorus (TP), TN:TP ratio, chemical oxygen demand (CODMn), chlorophyll-a (Chl-a), Secchi depth (SD), and trophic state index (TSI) were collected for the period 2001–2005. Sixteen natural factors included three of geographic location, five of lake morphology, and eight of climate variables. Pearson correlation analysis showed that TP and TSI were negatively related to elevation, lake depth, and lake volume, and positively related to longitude. All eutrophication parameters, except for CODMn and Chl-a, showed no significant correlation with climate variables. Multiple regression analyses indicated that natural factors together accounted for 13–58% of the variance in eutrophication parameters. When the 103 study lakes were classified into different groups based on longitude and elevation, regression analyses demonstrated that natural factors explained more variance in TN, TP, CODMn, Chl-a, and TSI in western lakes than in eastern lakes. Lake depth, volume, elevation, and mean annual precipitation were the main predictors of eutrophication parameters for different lake groups. Although anthropogenic impacts such as point- and nonpoint-source pollution are considered as the main determinants of lake eutrophication, our results suggest that some natural factors that reflect lake buffer capacity to nutrient inputs can also play important roles in explaining the eutrophication status of Chinese lakes.

Spatial and temporal patterns of the water quality in the Danjiangkou Reservoir, China

Abstract The three-route South-to-North Water Diversion Project (SNWDP), transferring water from the water-rich Yangtze River and its tributaries to the much drier area of North China for irrigation, industrial and domestic use, has been implemented in China since 2002. Thus, water quality in the Danjiangkou Reservoir, the water source area of the SNWDPs Middle Route, is of great concern. We investigate its water quality from 2004 to 2006 by monitoring some important physical (T, turbidity and SPM) and chemical (DO, pH, alkalinity, TDS, SpCond, ORP, CODMn and BOD) parameters and nutrient (nitrogen and phosphorus) contents. Consequently, their spatial and temporal patterns in the reservoir were examined. The results indicate that the water of the reservoir is of a Ca and HCO3 type, and the major pollutants are nitrogen and CODMn. Comparisons among the sampling sites show that water quality increases downstream, implying the self-purification capacity of the reservoir. The reservoir in general has better water quality in the dry season than in the wet season. Integrated basin management would be critical of the water quality in the Danjingkou Reservoir for the interbasin water transfer project.

Soil microbial community and its interaction with soil carbon and nitrogen dynamics following afforestation in central China.

Afforestation may alter soil microbial community structure and function, and further affect soil carbon (C) and nitrogen (N) dynamics. Here we investigated soil microbial carbon and nitrogen (MBC and MBN) and microbial community [e.g. bacteria (B), fungi (F)] derived from phospholipid fatty acids (PLFAs) analysis in afforested (implementing woodland and shrubland plantations) and adjacent croplands in central China. Relationships of microbial properties with biotic factors [litter, fine root, soil organic carbon (SOC), total nitrogen (TN) and inorganic N], abiotic factors (soil temperature, moisture and pH), and major biological processes [basal microbial respiration, microbial metabolic quotient (qCO2), net N mineralization and nitrification] were developed. Afforested soils had higher mean MBC, MBN and MBN:TN ratios than the croplands due to an increase in litter input, but had lower MBC:SOC ratio resulting from low-quality (higher C:N ratio) litter. Afforested soils also had higher F:B ratio, which was probably attributed to higher C:N ratios in litter and soil, and shifts of soil inorganic N forms, water, pH and disturbance. Alterations in soil microbial biomass and community structure following afforestation were associated with declines in basal microbial respiration, qCO2, net N mineralization and nitrification, which likely maintained higher soil carbon and nitrogen storage and stability.

Water quality assessment in the rivers along the water conveyance system of the Middle Route of the South to North Water Transfer Project (China) using multivariate statistical techniques and receptor modeling

A total of 190 grab water samples were collected from 19 rivers along the water conveyance system of the Middle Route of Chinas 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.

The impact of agricultural land use changes on soil organic carbon dynamics in the Danjiangkou Reservoir area of China

AimsOver recent decades, a large uncultivated area has been converted to woodland and shrubland plantations to protect and restore riparian ecosystems in the Danjiangkou Reservoir area, a water source area of China’s Middle Route of the South-to-North Water Transfer Project. Besides water quality, afforestation may alter soil organic carbon (SOC) dynamics and stock in terrestrial ecosystems, but its effects remain poorly quantified and understood.MethodsWe investigated soil organic C and nitrogen (N) content, and δ 13C and δ 15N values of organic soil in plant root-spheres and open areas in an afforested, shrubland and adjacent cropped soil. Soil C and N recalcitrance indexes (RIC and RIN) were calculated as the ratio of unhydrolyzable C and N to total C and N.ResultsAfforestation significantly increased SOC levels in plant root-spheres with the largest accumulation of C in the afforested soil. Afforestation also increased belowground biomass. The C:N ratios in organic soil changed from low to high in the order the cropped, the shrubland and the afforested soil. The RIC in the afforested and shrubland were higher than that in cropped soil, but the RIN increased from the afforested to shrubland to cropped soil. The δ15N values of the organic soil was enriched from the afforested to shrubland to cropped soil, indicating an increased N loss from the cropped soil compared to afforested or shrubland soil. Changes in the δ13C ratio further revealed that the decay rate of C in the three land use types was the highest in the cropped soil.ConclusionsAfforestation increased the SOC stocks resulted from a combination of large C input from belowground and low C losses because of decreasing soil C decomposition. Shifts in vegetation due to land use change could alter both the quantity and quality of the soil C and thus, have potential effects on ecosystem function and recovery.