ZHAO Mei-mei;FAN De-ling;GU Wen;WANG Zhen;LIANG Meng-yuan;LIU Ji-ning;ZHANG Zhi
Environmental Science,2021,Vol 42,No. 09
Because Jiangsu is an important economic province of China, it is necessary to examine the pollution characteristics and assess the ecological risk of environmentally persistent pharmaceutical pollutants (EPPPs) in this region. In this study, surface water samples were obtained from grade I–IV rivers and lakes (with an area of 50 km
2 or more) in Jiangsu Province, and then analyzed to determine the pollution level of EPPPs. In total, 35 EPPPs were detected in the surface water of Jiangsu Province, with total concentration in the samples ranging from 66.74 to 2 189.83 ng·L
−1. The 17 EPPPs with a detection rate of more than 25% were discussed in this study. The total concentration of 35 EPPPs was 72.48–1 142.79 ng·L
−1, and the mean concentration was 345.20 ng·L
−1. The total concentration of EPPPs was higher in the north and south than in the central part of Jiangsu. Yangzhou had the highest concentration of EPPPs in the whole province, and the main sources of this pollution were domestic sewage, shipping sewage discharge, and drug use in fishery breeding. The total concentration of EPPPs decreased on both sides of the region, with the Beijing-Hangzhou Canal and waste from the Yellow River forming the middle line. An ecological risk assessment of 17 EPPPs showed that single target drugs posed a low risk to water ecology in Jiangsu Province. The combined risk quotient of 17 EPPPs in water of Jiangsu Province was 0.03–0.52, indicating that EPPPs posed a low to moderate risk.
WANG Jia;RONG Hailiang;XUE Yu;SONG Baoping;WANG Zepeng;ZHANG Suzhen
South-to-North Water Transfers and Water Science & Technology,2021,Vol 19,No. 04
The riverside groundwater source area has both river and groundwater characteristics. Due to the particularity of its location and the complexity of recharge conditions, it is difficult to divide the protection area. In 2018, the Ministry of Environmental Protection of the People’s Republic of China issued the
Technical Specification for the Division of Drinking Water Source Protection Zones (HJ 338—2018), the regulation only stipulates that the boundary of the protected area should be divided according to the source of river water and the source of groundwater, both of them should be combined as the final boundary of the protected area. Operability does not provide a method and procedure for the classification of riverfront groundwater sources because of their special characteristics. To accurately determine the type of water source area, the land area of the protected area is calculated by empirical formula, and the results of pumping test are used to calculate the parameters of a complete well of phreatic water. The hydraulic gradient of group well is calculated accurately by the iterative operation of the interpolation method. The radius of the protected area is finally calculated with the radius of the empirical value. The analogy and empirical method are used to divide the water area of the protected area, taking into account the surrounding river and the influence of factors such as the distribution of upstream pollution sources, the size of risk sources, and river water quality on the size of the protected area. Finally, the scope of the protected area is revised according to the surrounding terrain and ground conditions. The type of Wangmu water source area is medium and small-sized pore phreatic water source area. The lithology of the phreatic water aquifer is mainly medium-coarse sand. The radius of the land area of the first-class protection area is 66.5 m and that of the second-class protection area is 665.0 m. The water area of the first-class protected area is divided by analogy and is extended to 1 000 m to the upper reaches and 100 m to the lower reaches of the Hutuo River. The water area of the second-class protected area extends 2 000 m to the upper reaches of the Hutuo River and 770 m to the lower reaches of the first-class protected area.
Conclusions (1) The investigation of the basic environmental conditions of the riverside groundwater sources and the nearby rivers is an important prerequisite for the division of the protection zones, and the flow direction and velocity of groundwater and surface water should be fully considered, according to the distribution of pollution sources, the migration and diffusion of pollutants, the pollution source type and risk grade can be determined accurately. (2) Taking into full account the hydrogeological characteristics of the region, combining with the geomorphological features and genetic analysis of the rivers near the region, comprehensively utilizing the information of well structure map and hydrogeological section map, etc., accurately judging the type of riverfront groundwater source area. (3) When choosing the method of the protection zone division of riverfront groundwater source area, the relationship between groundwater and river and the influence of groundwater exploitation on the quality and quantity of river water are fully considered. The radius of the protected area is calculated by the empirical formula method and the land area is divided, and the water area is divided by the analogy empirical method, the combination of the two methods is suitable for the division of the groundwater source protection area near the river, which is closely connected with the surrounding rivers. (4) The definition of the scope of the riverside groundwater source protection area should be based on the actual situation of the topography and topography of the area, the distribution of pollution sources, the flow direction of groundwater and surface water, etc., to facilitate the daily environmental management of the protected area, the boundary of the union area divided by the river-type water source and the groundwater-type water source is revised, wherever possible, clearly marked features should be used as the boundary of the protected area.
CONG Ming;YANG Hui;ZHANG Xiaojing;XIN Zhuohang;ZHANG Chi
South-to-North Water Transfers and Water Science & Technology,2021,Vol 19,No. 04
The rapid social-economic development has caused serious water environmental pollution, and water quality assessment is the basis of environmental water management. However, different assessment methods may yield different water quality grades results. The downstream reaches of the Liao River, Daliao River, and the estuary were focused on Water quality assessment was conducted based on several pollutants, and the applicability of the different methods was discussed. This study may provide scientific references for water quality assessment and management for the terrestrial-marine system. In September 2019 and June 2020, 30 sites in the downstream reaches of the Liao River, Daliao River, and the estuary were sampled. Dissolved oxygen (DO), total phosphorus, ammonia nitrogen, and permanganate index were selected as the evaluation indexes for rivers, and dissolved oxygen (DO), active phosphate, and inorganic nitrogen were selected as the evaluation indexes of estuarine waters. The single factor method and fuzzy variable method were selected for water quality assessment. The single factor method defines the grade of the worst single index as the comprehensive water quality grade. The fuzzy variable method uses the concept of opposite fuzzy sets to construct the relative subordinate degree matrix and to determine the weight of each index. Finally, the comprehensive relative subordinate degree was used to evaluate the water quality grade. Two methods were applied to determine the weights of indexes, i.e., the ordered binary comparison method and the entropy weight method. Results of single factor method showed that in the rivers, DO and permanganate indexes were the major pollutants in 2019, and the water quality varied from Grades Ⅱ to Ⅳ for all sampling sites. In 2020, the total phosphorus was the major pollutant, and 17 sampling sites have the water quality inferior to Grade V. For the estuary, water quality for all sampling sites was inferior to Glade Ⅳ due to the high mass concentrations of inorganic nitrogen. As for the fuzzy variable method, the water quality of the river water varied from Grade Ⅱ to Ⅳ, the estuary water was Grade Ⅱ and Ⅲ based on the ordered binary comparison method. Likewise, the water quality grades based on the entropy weight method were better than the ordered binary comparison method. In comparison, the water quality grades obtained by the fuzzy variable method were generally superior to single factor method both for the rivers and estuary water samples. The results proved that the fuzzy variable method can comprehensively consider the impact of each index on water quality grade by the index weight. The single factor evaluation method often produces “over-protection” results, but it can better reflect the strict requirements of water environment management and is more simple and feasible to implement. Overall, the results indicated that the water quality grades obtained by the fuzzy variable method were generally superior to single factor method. The major pollutants of river water were DO, permanganate index and total phosphorous, and the water quality grades were Ⅳ and inferior to Ⅴ based on the single factor method, while Ⅰ to Ⅲ based on fuzzy variable method. The major pollutants in the estuary were inorganic nitrogen. The single factor method is assessed based on the grade of the worst index, while the fuzzy variable method weighs the impacts of all indexes. Water quality grades using different assessment methods should be comprehensively considered in water environmental management.
LI Lianghui;LUO Xing;ZHAO Xu;LEI Sheng;XU Fugang
South-to-North Water Transfers and Water Science & Technology,2021,Vol 19,No. 04
Bank slope instability is a common geological hazard, which extremely threatens people’s property and life in China. Rainfall is an important cause of bank slope instability, and the slope angle and the slope material directly control the stability of the bank slope. Therefore, it is meaningful to study the influence of slope angle and slope material on bank slope stability under rainfall conditions. To explore the influence of slope angle and slope material on the instability of water banks under heavy rainfall, 5 model tests were carried out by taking different slope angles, slope materials and the deformation characteristics of bank slope were observed at different times. The change of pore water pressure and earth pressure in different positions of the slope were monitored by a pore water pressure gauge and earth pressure gauge. By comparing the failure process of 5 model tests at different times, the results showed that heavy rainfall had a significant effect on the stability of the slope surface structure. Under the action of rainfall, the surface structure rapidly saturated, the shear strength was greatly reduced and the stability deteriorates. However, the internal structure was less affected because the water was difficult to penetrate. At 60° slope angle, there were obvious cracks in the bank slope after 10 minutes of rainfall, and the cracks became larger as the rainfall time increased. After 2 hours of rainfall, the slope angle changed from 60° to 47°, and there were many obvious cracks on the surface of the bank slope. When the slope angle was 30° and 45°, there was no obvious damage on the bank slopes. The change in bank slope with different slope materials was also significantly different. There was little obvious damage to the clay slope during the whole test. When the sand content was 20%, the bank slope had erosion damage after 40 minutes of rainfall, and as the rainfall time increased, the damage gradually increased. Eventually, a collapse occurred on the surface of the bank slope when the sand content was 40%, and it was also noted that the bank slope had obvious cracks after 5 minutes of rainfall. About 70 minutes, there was a scour groove in the middle of the bank slope, which gradually widened with the increase of rainfall time. Under the rainfall, the bank slope became heavier and the sliding force increased. Moreover, with the increase of the water content of the bank slope, the shear strength decreased sharply, then induced bank slope instability. The slope angle had a great influence on bank stability. The bigger the slope angle, the deeper the rain seep, and the sliding force and infiltration force become stronger, which was not conducive to the stability of the bank slope, the influence was 60° > 45° > 30°, respectively. The slope material affected the bank slope stability directly, and different materials had different permeability. When the sand content was 40%, the permeability was best, and bank slope was damaged at 5 minutes and the response of pore water pressure was fast, the instability probability was higher with the worst permeability. When the bank slope was pure clay, and no damage obviously, and the response of pore water pressure was slow, the impact of rainfall on bank slope stability was low relatively.
LING Yanchen;SU Yuliang;HU Kewu;YUAN Hanhong;WU Bin;HUANG Hongbo;FANG Li;WU Jie;HUANG Tianyin;AO Xiuwei;SUN Wenjun
South-to-North Water Transfers and Water Science & Technology,2021,Vol 19,No. 04
The water supply system in Zhuhai City presents the characteristics of multiple water sources. The Xijiang River is the main drinking water source, and various reservoirs are auxiliary water sources. The reservoirs are responsible for the important function of water storage and water diversion. The water supply system combing the river and reservoirs in Zhuhai City makes the water quality not only affected by point and non-point source pollution in the river basin, but also interfered by the internal source pollution in the reservoir, which leads to the difficulty in controlling the stability of the water quality. The water quality of reservoirs in Zhuhai has gradually declined in recent years, and the algae content of the water body has continued to be high. The trend of eutrophication is becoming more and more obvious. However, there is still a lack of theoretical research into the impact of complex water supply system on algae in water sources, and technical guidance for algae control is therefore difficult and highly needed. The single factor analysis was used to compare the measured data and the regulated values of national standard, which aims to evaluate the water quality of four typical reservoirs (Meixi, Zhuyin, Dajingshan and Fenghuangshan reservoirs) in Zhuhai City from 2016 to 2019. The water quality characteristics and the spatial and temporal distribution of algae density in each reservoir were analyzed by the statistical method. The correlation between algae density and 10 water quality indexes (total nitrogen, total phosphorus, 5-day biochemical oxygen demand, ammonia-nitrogen, total organic carbon, permanganate index, dissolved oxygen, 2-methylisoborneol, geosmin, and turbidity) was studied by the bivariate analysis. The stepwise regression analysis was used to study and establish a regression model for preliminarily predicting the water quality of the reservoirs, with algae density, taste and odor compounds as dependent variables, and other environmental factors mentioned above as independent variables, respectively. Considering the current operational and problems of water plans in Zhuhai City, suitable solutions for solving the algae problems were analyzed and proposed from two perspectives: pollution source control and process transformation. The water quality of the reservoirs in Zhuhai City basically conformed to the standard of Class III surface water bodies from 2016 to 2019. However, the contents of total nitrogen and total phosphorus in some reservoirs exceeded the standard. From 2016 to 2019, the average algae density in the four reservoirs was 17.90 million cells/L in Meixi reservoir, 18.78 million L
−1 in Zhuyin reservoir, 9.43 million L
−1 in Fenghuangshan reservoir and 108.39 million L
−1 in Dajingshan reservoir, respectively. Under the influence of climate and water environment quality, the increase of algae density mostly occurred in spring, while the content of taste and odor compounds in the reservoirs were higher in autumn and winter, which could reach 5 times of the maximum odor threshold. Regression analysis showed that the water quality factors affecting algae density in Zhuhai reservoir involved total nitrogen and organic matter. The permanganate index was positively correlated with algal density, while total nitrogen and 5-day biochemical oxygen demand had negative correlation with the algal density. In addition, turbidity, organic matter and ammonia-nitrogen may contribute to the formation of taste and odor compounds in the reservoirs. And ammonia-nitrogen was the dominant factor and positively correlated with geosmin. Taking the monthly mean algae density of Zhuyin reservoir as the dependent variable while total nitrogen as the independent variable, a well-fitting regression model was established (
R2 = 0.911,
P < 0.001,
n = 9). Furthermore, taking geosmin as the dependent variable while turbidity, permanganate index ammonia-nitrogen as the independent variables, a well-fitted regression model was developed (
R2 = 0.911,
P < 0.001,
n = 54). High algae density, high taste and odor substances were the main water pollution problems in Zhuhai City. Ammonia-nitrogen and organic matter were the key factors affecting algae density and the production of taste and odor compounds in the reservoirs, algae problems in drinking water sources in Zhuhai City can be effectively solved by source control combined with the end treatment of ozone activated carbon or other advanced treatment technologies.
