Technical Notes WATER POLLUTION IN THE RIVER MOUTHS AROUND BOHAI BAY Cheng LIU 1 , Zhao-Yin WANG 1,2 and Yun HE 3 ABSTRACT Twelve water samples were collected and analyzed. The samples were taken from the river mouths around Bohai Bay including the Jiyun, New Yongding, Haihe, Dagu, Duliujian, Qingjinghuang, Qikou, Dakou, and Yellow Rivers, and tested for concentrations of heavy metals, arsenic, total nitrogen (TN) and total phosphorus (TP). The results show that the river mouths are polluted and the water quality exceeds Class V of the Environmental Quality Standard for Surface Water (EQSSW). The main pollutants are Hg, nitrogen (N) and phosphorus (P). The concentrations of the other pollutants are within Class II of the Standard. The Hg content in the Haihe River mouth is now 10 times higher than it was 20 years ago, indicating that the accelerating water pollution has reached an alarming level. The high concentrations of N and P cause eutrophication of the waters. Analysis indicates that the terrestrial pollutants and nutrients are the main cause of frequently occurring red tides in the Bohai Sea. Key Words: River mouth, Water quality, Pollution, Red tide, Bohai Bay 1 INTRODUCTION Bohai Bay is in the northwest part of the Bohai Sea. Many large cities and industrial hubs are located around the bay, including Beijing, Tianjin, Tangshan, Cangzhou, Huanghua, Binzhou and Dongying. The area has experienced quick economic development and urbanization and has become one of China’s political, economic and cultural centers. The rapid development and corresponding human activities have had severe influences on the water environment. Recent investigations show that a large part of the coastal waters of Bohai Bay have been polluted with concentrations of pollutants exceeding Class III of the Sea Water Quality Standard (GB 3097-1997) of China (Zhao et al., 2000). The pollution has deteriorated the ecology and reduced biodiversity of the waters. From 1983 to 1993, the number of fish species decreased from 85 to 74 in the estuary (Qi et al., 2000). The pollutants mainly originate inland, and are transported by the rivers flowing into the bay. These account for 87% of the total pollutants in the bay. Forty rivers carry 95% of the terrestrial-source pollutants and nutrients into the Bohai Bay (Zhao et al., 2000). This paper reports a recent field investigation of the bay and the results of analysis of the samples taken from the river mouths around the bay. 2 WATER QUALITY IN THE RIVER MOUTHS AROUND BOHAI BAY During June 6 to 10, 2001, the authors conducted a field investigation at the mouths of the New Yongding, Jiyun, Haihe, Dagu, Duliujian, Qingjinghuang, New Ziya, Nanpai, Dakou, New Zhangwei, Majia, Tuhai and Yellow Rivers. These are the most important rivers flowing into the Bohai Bay. Twelve water samples and 24 sediment samples at 19 river mouths were taken (Fig. 1). The water samples were analyzed for concentrations of Hg, Cu, Zn, As, Pb, total nitrogen (TN) and total phosphorus (TP) (Liu et al., 2002; Liu et al., 2003). 1 Dr., Asso. Prof., International Research and Training Center on Erosion and Sedimentation, Beijing 100044, China, E-mail: chliu@iwhr.com 2 Prof., Dept. of Hydraulic Engineering, Tsinghua University & International Research and Training Center on Erosion and Sedimentation, Beijing, 100084, China, E-mail: zywang@tsinghua.edu.cn 3 China Institute of Water Resources and Hydropower Research, Beijing 100084, China, E-mail: he_yun@mail.hf.ah.cn Note: The manuscript of this paper was received in June 2002. The revised version was received in Nov. 2002. Discussion open until Dec. 2004 - 326 - International Journal of Sediment Research, Vol. 18, No. 4, 2003, pp. 326-332 Sampling Sites 1 New Yongding River 13 Qikou Port 2 Jiyun River 14 Nanpai River 3 New Yongding Port 15 Huanghua Harbour 4 Haihe River mouth groyne 16 Dakou River 5 Dredged sediment of Haihe 17 New Zhangwei River 6 Tianjin Freight Harbour 18 Majia River 7 Haihe River mouth 19 Tuhai River 8 Dagu River 20 Diaokou River 9 Duliujian River 21 Dongying Harbour 10 Dredged sediment of Duliujian 22 Gudong groyne 11 Qingjinghuang River 23 Qingshuigou-Chahe River (Yellow River) 12 New Ziya River 24 Qingshuigou River (Yellow River) Fig. 1 Map of Bohai Bay and surrounding area 2.1 Water Quality and the Main Pollutants The water quality was evaluated by employing China’s Environmental Quality Standard for Surface Water (GHZB 1-1999) (EQSSW). Table 1 lists the classes of water quality at the sampling sites. All the river mouths were seriously polluted: the water qualities at 8 of the 12 sampling sites exceeded Class V, and the main pollutants were P and Hg. A comparison of the pollutants found in the water samples with the eutrophication index showed that the N content at these river mouths was also very high. The main pollutants in the river mouths between Jiyun to Qikou Port were N and P, and those near the Yellow River mouth were N and Hg. Table 1 Classes of water quality and the main pollutants in the waters of the sampling sites Sampling site Class of water quality Main pollutants Jiyun River Over V Hg, P, N New Yongding River Over V P, N Groyne of Haihe River mouth Over V Hg, P, N Freight harbour of Haihe River mouth IV Hg, P, N Dagu River Over V Hg, P, N Duliujian River Over V Hg, P, N Qingjinghuang River II N Qikou Port Over V Hg, P, N Dakou River II N Dongying Harbour Over V Hg, N Gudong Groyne Over V Hg, N Qingshuigou Cha-he of the Yellow River IV Hg, N Mercury (Hg): Fig. 2 presents the Hg content in the 12 waters around the Bohai Bay. Higher values appear near the Haihe and the Yellow River mouths. The Hg content in the waters at Dongying Harbour International Journal of Sediment Research, Vol. 18, No. 4, 2003, pp. 326-332 - 327 - and Gudong Groyne was as high as 2.59 µg/L and 1.71 µg/L respectively, much higher than 1.0 µg/L, which is Class V of the EQSSW. The Hg content between the Haihe and Duliujian river mouths ranged form 0.71 to 1.13 µg/L, which shows relatively higher values. Compared with the data of the 1980s (EPA of China, 1990A; EPA of China, 1990B), the Hg content in the waters near the Haihe river mouth is now roughly 10 times that of 20 years ago. This reflects that the accelerating water pollution, which is caused by the increasing wastewater discharges of metallurgy, chemical and other industries in Tianjin and the upstream drainage area, has reached an alarming level. The Hg content in the Yellow River mouth is low and has remained nearly unchanged compared with that of the 1980s, but the waters at Dongying Harbour and Gudong Groyne show significant increases in Hg concentration. This indicates that the wastewater directly discharged by the oil and petrochemicals industries in the Yellow River Delta has caused serious regional pollution, and that the fearful Hg pollution near the Yellow River mouth is not caused by the Yellow River itself. 0 0.5 1 1.5 2 2.5 3 123456789101112 Hg content (mg/L) Class IV and V of EQSSW Sampling sites ： 1. Jiyun river 2. New Yongding port 3. Haihe groyne 4. Haihe harbour 5. Dagu river 6. Duliujian river 7. Qingjinghuang river 8. Qikou fishery port 9. Dakou rRiver 10. Dongying harbour 11. Gudong Groyne 12. Qingshuigou-Chahe No. Sampling site Fig. 2 Hg Concentration in the waters at river mouths around Bohai Bay 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 123456789101112 TP content (mg/L) 0 200 400 600 800 1000 Population density (person/km 2 ) TP Population density Average TP Class IV and V of EQSSW Sampling sites ： 1. Jiyun river 2. New Yongding port 3. Haihe groyne 4. Haihe harbour 5. Dagu river 6. Duliujian river 7. Qingjinghuang river 8. Qikou fishery port 9. Dakou river 10. Dongying harbour 11. Gudong groyne 12. Qingshuigou-Chahe No. Sampling site Fig. 3 TP Concentration in the waters at river mouths around Bohai Bay Total Phosphorus (TP): The TP Content in the waters decreases from north to south along the bay (Fig. 3). Between the Jiyun River to Qikou Port, the TP content ranged from 0.10 to 0.66 mg/L, and all the values except that of the Qingjinghuang River and Tianjin Freight Harbour exceeded 0.20 mg/L, a Class V value of TP according to the EQSSW. The contents between Huanghua Harbour to the Yellow River mouth were between 0.02 and 0.05 mg/L, which falls within the Class II category of the EQSSW. Phosphorus is one of the elements necessary for biological growth, but when the phosphorus content in waters is high, alga overgrowth may occur, even to the point of causing eutrophication (EPA of China, 1997). Wang et al. (2001) concluded that 90% of phosphorus entering the waters is related to human activity. Domestic sewage discharge, the quantity of synthetic detergent usage and industrial capacity all increase with increased population density, so the phosphorus discharge also increases with increased population density. If the TP content is averaged in three sections, Tianjin (the Jiyun to Dagu rivers), - 328 - International Journal of Sediment Research, Vol. 18, No. 4, 2003, pp. 326-332 Cangzhou (the Duliujian to Dakou rivers) and Dongying (Dongying Harbour to the Yellow river mouth), the averaged TP content in the three sections decreases in three steps from north to south. Comparing the average population density for the same three sections, the same steps can be found. The results of field measurements further prove Wang et al.’s viewpoint. Total Nitrogen (TN): The TN content in 12 water samples ranged between 1.67 and 5.67 mg/L, which shows only slight variation (Fig. 4). The relatively higher values appear near the Haihe and the Yellow River mouths. The TN content is one of the import indexes used to evaluate water quality. High TN content in the waters of a bay or lake may cause a red tide or alga bloom. In China, half of the nitrogen discharged to the sea comes from agriculture and the other half comes from industry and domestic sewage (Wang et al., 2001). Owing to this proportion, the water in every river mouth has roughly the same TN content. Near the Haihe and Yellow River mouths, the TN content is relatively higher. This is because there is more domestic sewage and the chemical industry is more concentrated in the Tianjin and Dongying areas. 0 1 2 3 4 5 6 123456789101112 TN content (mg/L) Class V of the standard of the specific items for eutrophication in lakes and reservoirs Sampling sites： 1. Jiyun river 2. New Yongding port 3. Haihe groyne 4. Haihe harbour 5. Dagu river 6. Duliujian river 7. Qingjinghuang river 8. Qikou Fishery port 9. Dakou river 10. Dongying harbour 11. Gudong groyne 12. Qingshuigou-Chahe No. Sampling site Fig. 4 TN Content in the waters at river mouths around Bohai Bay Other Pollutants: Figures 5 and 6 show the concentration of copper, zinc, arsenic and lead in the 12 water samples. The concentrations of these metals in all of the waters were below the Class II of the EQSSW. The concentrations of Cu, Zn and As were between 0.056 and 0.119 mg/L, 0.067 and 0.118 mg/L, and 1.31 and 4.22 µg/L respectively, and the concentrations presented little variation along the bay. The contents of Pb were between 0.73 and 16.74 µg/L, among which the contents at the Haihe River mouths, the Qikou fishery port and Dongying Harbour were evidently higher than that in other waters. The high values were presumably caused by oil leakage from ships at ports and in harbours. Compared with the data from 1980s (EPA of China, 1990A; EPA of China, 1990B), the concentration and distribution area of the Cu, Zn, As and Pb in the waters along the bay have remained roughly the same, indicating that the water pollution control measures implemented by the governments of Tianjin and other cities have controlled most of the heavy metals and arsenic pollution in the Bohai Bay. 0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 123456789101112 Cu mg/L Zn mg/L Concen. of Cu & Zn (mg/L) Class I of the EQSSW for Cu Class I of the EQSSW for Zn Sampling sites ： 1. Jiyun river 2. New Yongding port 3. Haihe groyne 4. Haihe harbour 5. Dagu river 6. Duliujian river 7. Qingjinghuang river 8. Qikou fishery port 9. Dakou river 10. Dongying harbour 11. Gudong groyne 12. Qingshuigou-Chahe No. Sampling site Fig. 5 Cu and Zn Concentrations in the waters at river mouths around Bohai Bay International Journal of Sediment Research, Vol. 18, No. 4, 2003, pp. 326-332 - 329 - 0 2 4 6 8 10 12 14 16 18 123456789101112 As Pb Concen. of As & Pb(mg/L) Class I of the EQSSW for As-50mg/L Class I of the EQSSW for Pb Sampling sites ： 1. Jiyun river 2. New Yongding port 3. Haihe groyne 4. Haihe harbour 5. Dagu river 6. Duliujian river 7. Qingjinghuang river 8. Qikou fishery port 9. Dakou river 10. Dongying harbour 11. Gudong groyne 12. Qingshuigou-Chahe No. Sampling site Fig. 6 As and Pb Concentrations in the waters at river mouths around Bohai Bay 2.2 Contribution of river mouth pollution to the eutrophication of Bohai Bay Of the four sea areas in China, the Bohai Sea, the South China Sea, the East China Sea and the Yellow Sea, the Bohai Sea has the smallest number of red tide occurrences recorded, with only 5 from 1933 to 1989, which is 2% of the total number of red tides recorded in China. But the number of red tides has been increasing since the 1990s (Zhang, 1994). During the period from 1998 to 2000, unusual red tides with influence areas of thousands of square kilometer have appeared in the Bohai Sea twice (Liang et al., 2000, Zhou et al., 2001). Eutrophication is the foundation for red tide occurring in seas. It happens when the nutrients (N, P) input is larger than output, or nutrients (N, P) accumulation is larger than consumption. Red tides may occur when nutrients are enriched in waters (Fang et al., 2001), so it is very important to study the sources of the nutrients in the Bohai Bay. Table 2 Degrees of eutrophication in the river mouths around Bohai Bay Sampling site TN content (mg/L) TP content (mg/L) Class of water quality according to TN Class of water quality according to TP Degree of eutrophication (%)* Jiyun River 3.25 0.66 Over V Over V 85 New Yongding River 3.90 0.30 Over V Over V 86 Haihe Groyne 5.67 0.21 Over V Over V 87 Haihe Freight Harbour 1.93 0.13 Over V Over V 77 Dagu River 1.67 0.23 Over V Over V 75 Duliujian River 2.50 0.25 Over V Over V 81 Qingjinghuang River 1.68 0.10 Over V V 75 Qikou Port 2.33 0.28 Over V Over V 80 Dakou River 2.53 0.05 Over V IV 81 Dongying Harbour 2.94 0.03 Over V IV 83 Gudong Groyne 5.53 0.02 Over V III 87 Qingshuigou Cha-he 1.93 0.05 Over V IV 77 * Based on the evaluation standard for eutrophication by the National Research Institute of Disaster in Japan No general standard or method to evaluate the degree of eutrophication has been established. Much research has reported that the concentration of N and P in waters is closely related to eutrophication. In general, it is believed that waters are in a state of eutrophication when the concentrations of inorganic nitrogen and total phosphorus reach 0.3mg/L and 0.02mg/L respectively (Tian et al., 1998). Comparing the TP concentrations found in the waters at the river mouths along the Bohai Bay with these values, all - 330 - International Journal of Sediment Research, Vol. 18, No. 4, 2003, pp. 326-332 the river mouths are in a state of eutrophication. The EQSSW has standards for the specific items involved in the eutrophication of lakes and reservoirs, and the results of a comparison with these standards are listed in Table 2, which shows that the TN contents of 12 water samples all exceed Class V (1.2 mg/L), and the TP contents all reach or exceed Class V (0.12 mg/L) except the water samples taken at the river mouths from the Dakou to the Yellow rivers. The TN and TP content in the waters of the Bohai Bay have reached dangerous loads for eutrophication. The National Research Institute of Disaster in Japan put forward a method to evaluate the degree of eutrophication, in which the degree of eutrophication is determined by a percentage based on the 9 values of components such as TN, TP, chlorophyll, transparency and oxygen demand (Jin et al., 1989). The eutrophication percentages for the twelve samples were determined applying only the TN and TP contents to this method, and are also listed in the Table 2. The values were between 75 and 93% which indicates that a serious eutrophication problem exists in these waters. Identical conclusions were reached using different evaluation methods: that the waters of the river mouths around the Bohai Bay are all in a state of serious eutrophication, and the terrestrial pollution in the bay is one of the main reasons for the increasing eutrophication and occurrence of red tide events in the bay. 3 RELATIONSHIP BETWEEN WATER QUALITY AND SEDIMENT QUALITY Most pollutants have similar distribution in the water and sediment along the bay; Hg, Zn and TP have the most similar distributions in water and sediment. Fig.7 shows this similarity of TP. The similarity of distribution means that the pollutants are transferred between the sediment and overlaying water which are in a state of dynamic balance. Affected by the tidal flow, the bed sediment and suspended sediment in the river mouths are constantly being exchanged, i.e. the suspended sediment in the water is continuously falling to the river bed to become part of the bed load while the bed sediment erodes and becomes suspended sediment simultaneously. In this process, the suspended sediment may absorb the pollutants in the water and deposit them on the bottom, and the bed sediment may release the pollutants from the bottom during resuspension by the tide and waves. 0.03 0.04 0.05 0.06 0.07 0.08 123456789 TP content in sediment (%) 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 TP content in water (mg/L) TP content in sediment TP content in water Sampling sites ： 1. Jiyun 2. New Yongding 3. Haihe 4. Dagu 5. Duliujian 6. Qingjinghuang 7. Qikou port 8. Dakou 9. Qingshuigou-Chahe No. Sampling site Fig. 7 Distributions of TP content in the water and sediment at the river mouths 4 CONCLUSIONS The water samples were taken from 12 river mouths around Bohai Bay including the Jiyun, New Yongding, Haihe, Dagu, Duliujian, Qingjinghuang, Qikou, Dakou and the Yellow Rivers in June 2001. The concentrations of mercury, copper, zinc, lead, arsenic, total nitrogen (TN) and total phosphorus (TP) are analyzed. The following conclusions can be drawn: (1) All of the river mouths are seriously polluted, and the degree of pollution in the waters exceeds Class V of the Environmental Quality Standard for Surface Water (GHZB 1-1999). The main pollutants are N, P and Hg. The most serious water pollution by Hg appeared in the waters near the Yellow and Haihe River mouths. The TP content decreases from the north to the south along the bay which coincides with the downtrend of the population density. (2) A comparison of the current data with data from the 1980s shows that the concentration of Hg in the waters of the Haihe River mouth is 10 times that of 20 years ago. Though the concentration of Hg in the waters at the Yellow River mouth has remained nearly unchanged for the same 20 years, local Hg pollution in the International Journal of Sediment Research, Vol. 18, No. 4, 2003, pp. 326-332 - 331 - sea area near the mouth has become very serious. (3) The TN and TP content of all 12 water samples has reached a dangerous amount of eutrophication load; it is obvious that the terrestrial pollution flowing into the bay is one of the main sources for the increasing eutrophication and the increasing occurrence of red tide events in the bay. (4) A similar distribution concentration for most of the pollutants were found between the sediment and waters along the bay, indicating the pollutants are transferred between the sediment and overlaying water which are in a state of dynamic balance. 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H., 2000, Present environmental condition of Bohai Bay and protective measures, Research of Environmental Science, Vol. 13, No. 2, pp. 23 – 27 (in Chinese). Zhou, M. J., Zhu, M. Y. and Zhang, J., 2001, Red tide tendency and research in China, Life Science, Vol. 13, No. 2, pp. 54-59 (in Chinese). - 332 - International Journal of Sediment Research, Vol. 18, No. 4, 2003, pp. 326-332 . recent field investigation of the bay and the results of analysis of the samples taken from the river mouths around the bay. 2 WATER QUALITY IN THE RIVER MOUTHS AROUND BOHAI BAY During June. 2 presents the Hg content in the 12 waters around the Bohai Bay. Higher values appear near the Haihe and the Yellow River mouths. The Hg content in the waters at Dongying Harbour International. transported by the rivers flowing into the bay. These account for 87% of the total pollutants in the bay. Forty rivers carry 95% of the terrestrial-source pollutants and nutrients into the Bohai Bay (Zhao