Binghui Zheng

Analysis of phosphorus import characteristics of the upstream input rivers of Three Gorges Reservoir

The phosphorus import of upstream rivers of Three Gorges Reservoir (TGR) significantly affects water environment of TGR. To recognize phosphorus import characteristics of the Yangtze River, the Jialing River, and the Wu River, the accumulated 10-year statistic data (2004–2013) of total phosphorus concentration were analyzed. Two water sampling campaigns at the critical sites in three upstream rivers were carried out in October 2014 and January 2015 to determine phosphorus fractions in water and suspended particulate. The results showed that there were different import characteristics of phosphorus component in three upstream rivers. The phosphorus concentration in water of Wulong site in the Wu Rivers exhibited a sharply increasing trend from 2004 to 2011, and it was much higher than that in the Yangtze River and the Jialing River after 2005. Besides agricultural nonpoint pollutions, these were greatly attributed to phosphorus mine exploitations in the upstream basin of Wu River. In addition, the import of phosphorus fractions from three upstream rivers also showed significant temporal variations. During impounding stage of TGR (October 2014), total particulate phosphorus in water accounted for more than 50xa0% of total phosphorus (TP); meanwhile, 51xa0% of phosphorus in suspended particulate were in the form of bioavailable phosphorus, meaning that the potential impact of inputted particulate phosphorus from three upstream rivers on the water environment of TGR cannot be ignored. However, total dissolved phosphorus was the predominant phosphorus fractions in water which accounted for more than 61xa0% of TP during high water level stage of TGR (January 2015). During this period, large amount of reservoir backwater would flow into the tributaries of TGR; consequently, the inputted dissolved phosphorus could be accumulated in the tributaries and then may provide sufficient nutrients for algal bloom in spring.

Sediment quality assessment for heavy metal pollution in the Xiang-jiang River (China) with the equilibrium partitioning approach

Sediment quality criteria (SQC) of heavy metals (copper, lead, zinc and cadmium) for surface sediment have been developed to evaluate sediment contamination in the Xiang-jiang River of China using the equilibrium partitioning approach. USEPAs fresh water quality criteria [criterion continuous concentration (CCC), criterion maximum concentration (CMC)] were referenced to derive sediment quality criteria (SQC-low and SQC-high) of the Xiang-jiang River. The toxicological implications of SQC-low and SQC-high were similar with CCC and CMC, which were used to protect benthic organisms from short-term- and long-term exposure to pollutants. Sediment Pollution Index method was established based on the SQC-low and SQC-high values to evaluate sediment quality qualitatively and quantitatively. The evaluation method was applied to the Xiang-jiang River, and the result indicated that the cadmium contamination in the sediments was of concern; especially, in the Zhu-zhou, Yue-yang, and the middle and downstream reaches of Heng-yang section.

Seasonal variation of enrichment, accumulation and sources of heavy metals in suspended particulate matter and surface sediments in the Daliao river and Daliao river estuary, Northeast China

Suspended particulate matter (SPM) and sediment samples were collected from the Daliao river and Daliao river estuary (Northeast China) to clarify the changes of metal concentrations, enrichment and accumulation during the medium season, wet season and dry season, respectively. The results showed that concentrations, enrichment factor (EF) values and geo accumulation (Igeo) values for metals significantly changed during the time. Generally, metal concentrations in sediments during the dry season were higher than those during the medium season and wet season. SQGs results revealed that potential toxicity for aquatic organisms may frequently happen for most of the metals during the dry season, while during the wet season and medium season, adverse effects for aquatic organisms may occasionally happen. Enrichment factor values (EF values) showed that various range of EF values for metals were found and Cd, Pb, As and Zn showed the most sever enrichment among the studied metals. Seasonal mean EF values for metals in SPM showed the following orders: Pb (2.82)xa0>xa0Cd (2.53)xa0>xa0As (2.07)xa0>xa0Zn (2.05)xa0>xa0Mn (1.94)xa0>xa0Co (1.23)xa0>xa0Fe (1.20)xa0>xa0Ni (1.15)xa0>xa0Cr (1.12)xa0>xa0Cu (1.00) and showed the following decreasing order: medium seasonxa0>xa0dry seasonxa0>xa0wet season, while for Mn, Cd and Pb, it shows that dry seasonxa0>xa0medium seasonxa0>xa0wet season, indicating minor enrichment for all the elements. For sediments, seasonal mean EF values for metals are showed as follows: Cd (12.80)xa0>xa0Pb (9.62)xa0>xa0As (4.11)xa0>xa0Zn (3.15)xa0>xa0Co (2.32)xa0>xa0Cr (2.27)xa0>xa0Mn (2.05)xa0>xa0Fe (1.87)xa0>xa0Ni (1.46)xa0>xa0Cu (1.43), indicating severe enrichment for Cd, moderate severe enrichment for Pb, moderate enrichment for As and Zn and minor enrichment for Co, Cr, Mn, Fe, Ni and Cu, respectively. Geo-accumulation index (Igeo) results indicated that mean Igeo values for most of metals in sediment samples were below 0 which was classified as unpolluted except for Cd whose Igeo values was classified as unpolluted to moderately polluted sediment samples during the wet season and dry season, respectively. Igeo values in SPM for metals also showed seasonal variation and Cd, Pb, As and Zn displayed the highest seasonal mean Igeo values. Sources analysis for metals in sediments indicated that natural and anthropogenic sources both contributed to the metal accumulations in sediments and industrial and municipal sewage effluents discharged from the upstream cities may be the main anthropogenic sources for metals in the Daliao river and Daliao river estuary.

Impact of upstream river inputs and reservoir operation on phosphorus fractions in water-particulate phases in the Three Gorges Reservoir

The impoundment of the Three Gorges Reservoir (TGR) has changed water-sand transport regime, with inevitable effects on phosphorus transport behavior in the TGR. In this study, we measured phosphorus fractions in water and suspended particles transported from upstream rivers of the TGR (the Yangtze River, the Jialing River and the Wu River) to reservoir inner region over the full operation schedule of the TGR. The aim was to determine how phosphorus fractions in water and particulate phases varied in response to natural hydrological processes and reservoir operations. The results showed that total phosphorus concentration (TP) in water in the TGR inner region was 0.17±0.05mg/L, which was lower than that in the Yangtze River (0.21±0.04mg/L) and the Wu River (0.23±0.03mg/L), but higher than that in the Jialing River (0.12±0.07mg/L). In the TGR inner region, there was no clear trend of total dissolved phosphorus (TDP), but total particulate phosphorus (TPP) showed a decreasing trend from tail area to head area because of particle deposition along the TGR mainstream. In addition, the concentrations of TPP in water and particulate phosphorus in a unit mass of suspended particles (PP) in the TGR inner region were higher in October 2014 and January 2015 (the impounding period and high water level period) than that in July 2015 (the low water level period). The temporal variations of PP and TPP concentrations in the TGR may be linked to the change of particle size distribution of suspended particles in the TGR. The particle size tended to be finer due to large-size particle deposition under stable hydrodynamic conditions in the process of TGR impoundment, resulting in high adsorption capacities of phosphorus in suspended particles. The results implied that phosphorus temporal variations in the TGR could exert different impacts on water quality in the TGR tributaries.

Effect of algal bloom on phosphorus exchange at the sediment–water interface in Meiliang Bay of Taihu Lake, China

Taihu Lake, the third largest freshwater lake, is typical of many eutrophic lakes in China. In recent years, Taihu Lake is frequently suffering from extensive algal blooms which dramatically change the environmental conditions (e.g., oxygen concentration and pH) and thereafter may influence phosphorus (P) exchanges at the sediment–water interface. Here, we used the repeated ANOVA to compare the water P concentration either with or without algae addition by a mimic experiment. Over a period of 20xa0days of incubation, chlorophyll a (Chl-a), water temperature, dissolved oxygen (DO), oxidation–reduction potential (ORP), pH, nitrate (NO3−), as well as the P fractions of overlying water and sediments were monitored. Results showed that compared with the Control treatment algal bloom significantly decreased DO, ORP, and pH and increased P concentration of overlying water. The first 7xa0days of incubation could be considered as a period of algal decomposition for the Algae treatment based on the decreased Chl-a concentration, as well as the black and smelly water. The increased total P (TP), dissolved total P (DTP), and soluble reactive P (SRP) during the initial 7xa0days mainly resulted from the P release from the decomposing algae when DO concentration was lower than 0.5xa0mgxa0L−1, and NO3− having a potential to suppress iron (Fe) reduction was up to 1.1xa0mgxa0L−1. Subsequently, Chl-a concentration dramatically increased and reached at a maximum value on September 17, which indicated that algal growth became the dominant process. The increased P level during algal growth might result from the sediment Fe-bound P release when DO and NO3− concentration was kept at low levels, which could be further confirmed by the lowest NaOH-extractable P (NaOH-P) in the sediments on September 19. The results indicate that influence of algal blooms on sediments P release cannot be neglected during algal decomposition as well as the followed period of algal growth in Meiliang Bay, the highly polluted region of Taihu Lake.

Distribution, sources, and risk assessment of polycyclic aromatic hydrocarbons (PAHs) in surface water in industrial affected areas of the Three Gorges Reservoir, China

Water samples were collected from wastewater treatment plant (WWTP), drain water (DW), major tributaries (MT), and main course of the Yangtze River (MY) in areas of three industrial parks (IPs) in Chongqing city in the Three Gorges Reservoir (TGR). Sixteen EPA priority polycyclic aromatic hydrocarbon (PAH) pollutants were quantified to identify the effects of industrial activities on water quality of the TGR. The results showed that 11 individual PAHs were quantified and 5 PAHs (naphthalene (Nap), acenaphthylene (Acy), benzo[k]fluoranthene (BkF), indeno[1,2,3-cd]pyrene (InP), and benzo[g,h,i]perylene (BgP)) were under detection limits in all of the water samples. Three-ring and four-ring PAHs were the most detected PAHs. Concentrations of individual PAHs were in the range of not detected (nd) to 24.3xa0ng/L. Total PAH concentrations for each site ranged from nd to 42.9xa0ng/L and were lower compared to those in other studies. The mean PAH concentrations for sites WWTP, DW, MT, and MY showed as follows: DW (25.9xa0ng/L) > MY (15.5xa0ng/L) > MT (14.0xa0ng/L) > WWTP (9.3xa0ng/L), and DW contains the highest PAH concentrations. Source identification ratios showed that petroleum and combustion of biomass coal and petroleum were the main sources of PAHs. The results of potential ecosystem risk assessment indicated that, although PAH concentrations in MT and MY are likely harmless to ecosystem, contaminations of PAHs in DW were listed as middle levels and some management strategies and remediation actions, like strengthen clean production processes and banning illegal sewage discharging activities, etc., should be taken to lighten the ecosystem risk caused by PAHs especially risks caused by water discharging drains.

Sixty-year sedimentary records of polymetallic contamination (Cu, Zn, Cd, Pb, As) in the Dahuofang Reservoir in Northeast China

The sedimentation rate (by 210Pb and 137Cs dating), sediment characteristics, contamination and accumulation history of trace metals (Cu, Zn, Cd, Pb and As) were studied for sediments from Dahuofang Reservoir, which is the most important source of drinking water in Northeast China. The results indicated that the variation of sediment grain size has shown typical river-type, layoff period and lacustrine-type sediments characteristic, which is in accordance with the building and operation history of Dahuofang Reservoir. Concentrations of the five elements showed an increasing trend with a fluctuation in mid-1990s. Especially after 1975, the contaminations became more severe. Relationships between the elements and sediment parameters suggested that the increased level of contaminations of trace metals after 1975 occurred mainly as a result of anthropogenic input, including the mining and smelting of Cu at the upstream of Hun River, as well as the industrial, agricultural and economic activities around Dahuofang Reservoir after the “Reform and Open” policy embarked by China in 1978. Accumulation state of these elements was investigated based on the enrichment factors. In the whole study period, enrichment of Pb and As was minimal; Cu and Zn enrichment was moderate; Cd enrichment was moderate, but with significant aggregation in recent years.

Water quality analysis for the Three Gorges Reservoir, China, from 2010 to 2013

China’s “Environmental Quality Standards for Surface Water” (GB3838-2002) was combined with the Canadian Council of Ministers of the Environment Water Quality Index (CCME-WQI) to evaluate the water quality of the Three Gorges Reservoir (TGR) of China. The CCME-WQI values indicated that the overall water quality in the TGR remained stable and was ranked as “good” during the period 2010–2013. The water quality at the inflow sections of the Jialing and Wu Rivers was worse than that of the main channel (the Yangtze River), especially for backwater sections of these two tributaries. Total nitrogen, total phosphorus, and fecal coliform amounts were the three key pollutants affecting the water quality of the TGR. During low-water-level operation periods, the water quality of the TGR deteriorated. Human activities, such as the seasonal fertilization of croplands, appeared to be the main cause of the variation in water quality in different operation cycles. However, the relationship between water quality and reservoir operation cycles is complex and requires more research and data to be clarified. The CCME-WQI can be used to easily qualitatively and quantitatively assess whether the overall water quality meets the specified water objectives, and provides a clear indication of the water category. Compared with the single factor pollution index (SFPI) method, the CCME-WQI uses a group of typical criteria rather than worst-case criteria. The CCME-WQI, therefore, provides a more meaningful and comprehensive assessment than the SFPI method.

Temporal and spatial variation of arsenic species in the Dahuofang reservoir in northeast China

Overlying water, pore water, and sediment samples were collected from the Dahuofang reservoir in November 2011 and April 2012, respectively. Total arsenic and arsenic species including arsenite, arsenate, monomethylarsonic, and dimethylarsinic were analyzed by ICP-MS and HPLC–ICP-MS. The results indicated that the environments of the Dahuofang reservoir were in reduced conditions, arsenite was the predominant species in pore water and sediments in the reservoir. Arsenic concentrations in overlying water were very low in all the samples but showed different trend during the different time. In November, arsenic concentrations in the reservoir inlet were higher than that in the other sites, whereas arsenic showed accumulation from the upstream to downstream of the reservoir in samples collected in April. In pore water, arsenic concentrations were about 23 and 37 times higher than those in overlying water in November and April, respectively, and relatively high levels of arsenite were also detected in the pore water. In surface sediments, total arsenic and arsenic species content in the reservoir inlet showed the following decreasing order: R1u2009>u2009R10u2009>u2009R4. The results also showed that moderate ecological risks exist in pore water and sediments in the Dahuofang reservoir.

Arsenic release from the abiotic oxidation of arsenopyrite under the impact of waterborne H2O2: a SEM and XPS study

Our previous study has proven that waterborne hydrogen peroxide can affect the arsenic releasing process from arsenopyrite powder, but little is known about the change of morphology and element constitutes on arsenopyrite surface. In this study, a simulated experiment was conducted to examine the effects of hydrogen peroxide (at a concentration range of 5–50xa0μM) on the abiotic oxidation of arsenopyrite cubes. Scanning electron microscopy (SEM), energy dispersive X-ray spectrometer (EDS), and X-ray photoelectron spectroscopy (XPS) were used to characterize the changes of microstructure morphology and elemental species on arsenopyrite surface. The results showed that micromolar level of H2O2 accelerated the release of arsenic and iron but passivated the sulfur release from arsenopyrite surfaces. As(III) oxidation in solution was enhanced at the early part of the experiment, but the release of As(III) was facilitated at the latter part. As(V) concentrations in solution increased along with the elevated H2O2 dosage level. The SEM images showed different surface microstructure on the surface of CK and all the treatments. EDS results showed that the ratios of S/Fe, Fe/As, and S/As in bulk arsenopyrite revealed evident increasing trend along with the increase of H2O2 dosage level. As the result of surface leaching, the XPS results did not show significant trend, while it suggests that H2O2 accelerated the formation of Fe–As oxidized layer on the arsenopyrite surface.