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Zhou Y.,CAS Nanjing Institute of Geography and Limnology | Zhou Y.,Sino Danish Center for Education and Research | Zhou Y.,University of Chinese Academy of Sciences | Zhang Y.,CAS Nanjing Institute of Geography and Limnology | And 8 more authors.
Water Research | Year: 2016

Drinking water lakes are threatened globally and therefore in need of protection. To date, few studies have been carried out to investigate how the composition and dynamics of chromophoric dissolved organic matter (CDOM) in drinking water lakes are influenced by inflow rate. Such CDOM can lead to unpleasant taste and odor of the water and produce undesirable disinfection byproducts during drinking water treatment. We studied the drinking water Lake Qiandao, China, and found that the concentrations of suspended particulate matter (SPM) in the lake increased significantly with inflow rate (p < 0.001). Similarly, close relationships between inflow rate and the CDOM absorption coefficient at 350 nm a(350) and with terrestrial humic-like fluorescence C3 and a negative relationship between inflow rate and the first principal component (PC1) scores, which, in turn, were negatively related to the concentrations and relative molecular size of CDOM (p < 0.001), i.e. the concentration and molecular size of CDOM entering the lake increased proportionately with inflow rate. Furthermore, stable isotopes (δD and δ18O) were depleted in the upstream river mouth relative to downstream remaining lake regions, substantiating that riverine CDOM entering the lake was probably driven by inflow rate. This was further underpinned by remarkably higher mean chlorophyll-a and in situ measured terrestrial CDOM fluorescence (365/480 nm) and apparent oxygen utilization (AOU), and notably lower mean PC1 and CDOM spectral slope (S275-295) recorded in the upstream river mouth than in the downstream main lake area. Strong negative correlations between inflow rate and a(250):a(365), S275-295, and the spectral slope ratio (SR) implied that CDOM input to the lake in rainy period was dominated by larger organic molecules with a more humic-like character. Rainy period, especially rainstorm events, therefore poses a risk to drinking water safety and requires higher removal efficiency of CDOM during drinking water treatment processes. © 2016 Elsevier Ltd.


PubMed | University of Aarhus, CAS Nanjing Institute of Geography and Limnology, Chalmers University of Technology and Institute of Environmental Protection Science
Type: | Journal: Water research | Year: 2016

Drinking water lakes are threatened globally and therefore in need of protection. To date, few studies have been carried out to investigate how the composition and dynamics of chromophoric dissolved organic matter (CDOM) in drinking water lakes are influenced by inflow rate. Such CDOM can lead to unpleasant taste and odor of the water and produce undesirable disinfection byproducts during drinking water treatment. We studied the drinking water Lake Qiandao, China, and found that the concentrations of suspended particulate matter (SPM) in the lake increased significantly with inflow rate (p<0.001). Similarly, close relationships between inflow rate and the CDOM absorption coefficient at 350nm a(350) and with terrestrial humic-like fluorescence C3 and a negative relationship between inflow rate and the first principal component (PC1) scores, which, in turn, were negatively related to the concentrations and relative molecular size of CDOM (p<0.001), i.e. the concentration and molecular size of CDOM entering the lake increased proportionately with inflow rate. Furthermore, stable isotopes (D and (18)O) were depleted in the upstream river mouth relative to downstream remaining lake regions, substantiating that riverine CDOM entering the lake was probably driven by inflow rate. This was further underpinned by remarkably higher mean chlorophyll-a and in situ measured terrestrial CDOM fluorescence (365/480nm) and apparent oxygen utilization (AOU), and notably lower mean PC1 and CDOM spectral slope (S275-295) recorded in the upstream river mouth than in the downstream main lake area. Strong negative correlations between inflow rate and a(250):a(365), S275-295, and the spectral slope ratio (SR) implied that CDOM input to the lake in rainy period was dominated by larger organic molecules with a more humic-like character. Rainy period, especially rainstorm events, therefore poses a risk to drinking water safety and requires higher removal efficiency of CDOM during drinking water treatment processes.


Zhang Y.,CAS Nanjing Institute of Geography and Limnology | Yin Y.,CAS Nanjing Institute of Geography and Limnology | Yin Y.,University of Chinese Academy of Sciences | Liu X.,CAS Nanjing Institute of Geography and Limnology | And 7 more authors.
Organic Geochemistry | Year: 2011

From 2005 to 2009, the spatial distribution and the seasonal dynamics of chromophoric dissolved organic matter (CDOM) were explored in Lake Taihu in eastern China. The spatial-seasonal dynamics of CDOM absorption and three CDOM composition variables, including spectral slope (S), spectral slope ratio (SR) and the M value, defined as the ratio of absorption at 250nm/365nm, were analyzed and discussed. Furthermore, river input processes and degradation of phytoplankton were studied to assess their impact on CDOM composition and the factors involved in the spatial-seasonal variability of CDOM. The CDOM absorption coefficient at a wavelength of 350nm, a(350), ranged from 1.37-9.55m-1 with a mean of 3.33±1.32m-1. Spatially, higher a(350) values, but lower spectral slope, spectral slope ratio and M values, were recorded in the northern algae dominated bays while lower values were recorded in southeastern macrophyte dominated bays. The a(350) was significantly higher in inshore waters than in offshore waters. Values of S, SR and M decreased during the flood and algal bloom season in spring and summer whereas a(350) increased. In the three river profiles, the gradual decrease of a(350) along the trajectory from the river mouth into the lake during the flood season showed the contribution of allochthonous CDOM. A laboratory phytoplankton degradation experiment was conducted to determine the contribution of CDOM production from phytoplankton. The significant increase of a(350) with time in the CDOM production experiment underlines the importance of autochthonous CDOM production during the algal bloom season. In summary, the significant increase of a(350) in spring and summer (algal bloom season) may be due to both the allochthonous CDOM input from the surrounding rivers and the autochthonous production of CDOM from degrading phytoplankton. © 2011 Elsevier Ltd.


Wu Z.,Chun'an Environmental Monitoring Station | Zhang Y.,CAS Nanjing Institute of Geography and Limnology | Zhou Y.,CAS Nanjing Institute of Geography and Limnology | Zhou Y.,University of Chinese Academy of Sciences | And 3 more authors.
International Journal of Environmental Research and Public Health | Year: 2015

Water transparency is a useful indicator of water quality or productivity and is widely used to detect long-term changes in the water quality and eutrophication of lake ecosystems. Based on short-term spatial observations in the spring, summer, and winter and on long-term site-specific observation from 1988 to 2013, the spatial, seasonal, long-term variations, and the factors affecting transparency are presented for Xin’anjiang Reservoir (China). Spatially, transparency was high in the open water but low in the bays and the inflowing river mouths, reflecting the effect of river runoff. The seasonal effects were distinct, with lower values in the summer than in the winter, most likely due to river runoff and phytoplankton biomass increases. The transparency decreased significantly with a linear slope of 0.079 m/year, indicating a 2.05 m decrease and a marked decrease in water quality. A marked increase occurred in chlorophyll a (Chla) concentration, and a significant correlation was found between the transparency and Chla concentration, indicating that phytoplankton biomass can partially explain the long-term trend of transparency in Xin’anjiang Reservoir. The river input and phytoplankton biomass increase were associated with soil erosion and nutrient loss in the catchment. Our study will support future management of water quality in Xin’anjiang Reservoir. © 2015 by the authors; licensee MDPI, Basel, Switzerland.


Tang C.,Central South University of forestry and Technology | Li K.,Central South University of forestry and Technology | Li C.,Institute of Environmental Protection Science
Advanced Materials Research | Year: 2012

The effect of pH on Cd adsorption was studied using red soil as an adsorbent in this study.The curve of Cd adsorbed vs pH showed that the adsorption amount increased slowly at low pH, then quickly with the increase of pH, and reached the maximum amount at high pH. The adsorption data at different pH values and initial Cd(II) concentrations were fitted well by Langmuir isotherm. At last, a pH-dependent model of adsorption isotherms of Cd was established by substituting the fitting results obtained from experimental data for the parameters in Langmuir equation. © (2012) Trans Tech Publications, Switzerland.


Tang C.,Central South University of forestry and Technology | Zhou X.,Central South University of forestry and Technology | Li C.,Institute of Environmental Protection Science
Advanced Materials Research | Year: 2012

A constant direct current density of 0.5 mA/cm 2 was applied in a laboratory experiment for studing the feasibility of electrokinetic treatment on the removal of Cd from red soils. The result shows that the removal efficiency of Cd was remarkably pH-dependent. The initial Cd concentration was1 490 mg/kg and over 79% of Cd was removed from the red soils after 96 hours' treatment. The energy expenditure was about 77.6 kW.h/m 3 and the cost was 42.6 RMB Yuan/m 3, which suggest that electrokinetic soil processing is a promising technology for remedying cd-contaminated red soils. © (2012) Trans Tech Publications, Switzerland.


Zhang Y.,CAS Nanjing Institute of Geography and Limnology | Wu Z.,Chunan Environmental Monitoring Station | Liu M.,Institute of Environmental Protection Science | He J.,Institute of Environmental Protection Science | And 3 more authors.
Limnology and Oceanography | Year: 2014

Using the vertical temperature profiles of Lake Qiandaohu from January 2010 to April 2013, we evaluated the monthly and seasonal variations of water temperature and thermocline parameters, and developed empirical models among thermocline depth (TD), thickness (TT), and strength (TS). We also developed empirical models between TD, TT, TS, and surface-water temperature (0-2 m) (T0-2 m), and transparency (Secchi disk depth, SDD). Additionally, we assessed the changes in TD, TT, and TS over the past 62 yr, based on our empirical models, air temperature data from 1951 to 2012, and SDD data from 1987 to 2012. Lake Qiandaohu is warm monomictic, with a long period of thermal stratification from April until January, and only a short period of mixing in the winter or spring (February or March). There were significant correlations between SDD and TD (positive), and between SDD and TT (negative). There was a significant negative correlation between T0-2 m and TD during the stratification weakness period (July-February), and a significant positive correlation between T0-2 m and TT for all data, including the stratification formation and weakness periods. Air temperature near the lake rose 1.2°C between 1951 and 2012, corresponding to a 0.8°C increase in T0-2 m, and a 0.78 m decrease in SDD between 1987 and 2012. The increase in air temperature and the decrease in SDD caused a decrease in TD and an increase in TT, facilitating the thermal stratification and stability of the lake; therefore, climate warming has had a significant effect on the thermal regime of Lake Qiandaohu. © 2014, by the Association for the Sciences of Limnology and Oceanography, Inc.


Zhang Y.,CAS Nanjing Institute of Geography and Limnology | Wu Z.,Chunan Environmental Monitoring Station | Liu M.,Institute of Environmental Protection Science | He J.,Institute of Environmental Protection Science | And 7 more authors.
Water Research | Year: 2015

From January 2010 to March 2014, detailed depth profiles of water temperature, dissolved oxygen (DO), and chromophoric dissolved organic matter (CDOM) were collected at three sites in Lake Qiandaohu, a large, deep subtropical reservoir in China. Additionally, we assessed the changes in DO stratification over the past 61 years (1953-2013) based on our empirical models and long-term air temperature and transparency data. The DO concentration never fell below 2mg/L, the critical value for anoxia, and the DO depth profiles were closely linked to the water temperature depth profiles. In the stable stratification period in summer and autumn, the significant increase in CDOM in the metalimnion explained the decrease in DO due to the oxygen consumed by CDOM. Well-developed oxygen stratification was detected at the three sites in spring, summer and autumn and was associated with thermal stratification. Oxycline depth was significantly negatively correlated with daily air temperature and thermocline thickness but significantly positively correlated with thermocline depth during the stratification weakness period (July-February). However, there were no significant correlations among these parameters during the stratification formation period (March-June). The increase of 1.67°C in yearly average daily air temperature between 1980 and 2013 and the decrease of 0.78m in Secchi disk depth caused a decrease of 1.65m and 2.78m in oxycline depth, respectively, facilitating oxygen stratification and decreasing water quality. Therefore, climate warming has had a substantial effect on water quality through changing the DO regime in Lake Qiandaohu. © 2015 Elsevier Ltd.


PubMed | Chunan Environmental Monitoring Station, CAS Nanjing Institute of Geography and Limnology and Institute of Environmental Protection Science
Type: Journal Article | Journal: International journal of environmental research and public health | Year: 2015

Water transparency is a useful indicator of water quality or productivity and is widely used to detect long-term changes in the water quality and eutrophication of lake ecosystems. Based on short-term spatial observations in the spring, summer, and winter and on long-term site-specific observation from 1988 to 2013, the spatial, seasonal, long-term variations, and the factors affecting transparency are presented for Xinanjiang Reservoir (China). Spatially, transparency was high in the open water but low in the bays and the inflowing river mouths, reflecting the effect of river runoff. The seasonal effects were distinct, with lower values in the summer than in the winter, most likely due to river runoff and phytoplankton biomass increases. The transparency decreased significantly with a linear slope of 0.079 m/year, indicating a 2.05 m decrease and a marked decrease in water quality. A marked increase occurred in chlorophyll a (Chla) concentration, and a significant correlation was found between the transparency and Chla concentration, indicating that phytoplankton biomass can partially explain the long-term trend of transparency in Xinanjiang Reservoir. The river input and phytoplankton biomass increase were associated with soil erosion and nutrient loss in the catchment. Our study will support future management of water quality in Xinanjiang Reservoir.


PubMed | Chunan Environmental Monitoring Station, CAS Nanjing Institute of Geography and Limnology and Institute of Environmental Protection Science
Type: | Journal: Water research | Year: 2015

From January 2010 to March 2014, detailed depth profiles of water temperature, dissolved oxygen (DO), and chromophoric dissolved organic matter (CDOM) were collected at three sites in Lake Qiandaohu, a large, deep subtropical reservoir in China. Additionally, we assessed the changes in DO stratification over the past 61 years (1953-2013) based on our empirical models and long-term air temperature and transparency data. The DO concentration never fell below 2 mg/L, the critical value for anoxia, and the DO depth profiles were closely linked to the water temperature depth profiles. In the stable stratification period in summer and autumn, the significant increase in CDOM in the metalimnion explained the decrease in DO due to the oxygen consumed by CDOM. Well-developed oxygen stratification was detected at the three sites in spring, summer and autumn and was associated with thermal stratification. Oxycline depth was significantly negatively correlated with daily air temperature and thermocline thickness but significantly positively correlated with thermocline depth during the stratification weakness period (July-February). However, there were no significant correlations among these parameters during the stratification formation period (March-June). The increase of 1.67 C in yearly average daily air temperature between 1980 and 2013 and the decrease of 0.78 m in Secchi disk depth caused a decrease of 1.65 m and 2.78 m in oxycline depth, respectively, facilitating oxygen stratification and decreasing water quality. Therefore, climate warming has had a substantial effect on water quality through changing the DO regime in Lake Qiandaohu.

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