WATER POLLUTION IN THE RIVER MOUTHS AROUND BOHAI BAY

Technical NotesWATER POLLUTION IN THE RIVER MOUTHS AROUND BOHAI BAYCheng LIu', Zhao-Yin WANGI.2 and Yun HE'ABSTRACTTwelve water samples were collcted and analyzed. The samples were taken from the rivermouths 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 arepolluted and the water quality exceeds Class V of the Environmental Quality Standard for SurfaceWater (EQSSW). The main pollutants are Hg, nitrogen (N) and phosphorus (P). The concentrationsof the other pollutants are within Class II of the Standard. The Hg content in the Haihe River mouthis now 10 times higher than it was 20 years ago, indicating that the accelerating water pollution hasreached 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 frequentlyoccurring red tides in the Bohai Sea.Key Words: River mouth, Water quality, Pollution, Red tide, Bohai Bay1 INTRODUCTIONBohai Bay is in the northwest part of the Bohai Sea. Many large cities and industrial hubs are locatedaround the bay, including Beijing, Tianjin, Tangshan, Cangzhou, Huanghua, Binzhou and Dongying. Thearea has experienced quick economic development and urbanization and has become one of China'spolitical, economic and cultural centers. The rapid development and corresponding human activities havehad severe influences on the water environment. Recent investigations show that a large part of thecoastal waters of Bohai Bay have been polluted with concentrations of pollutants exceeding Class II ofthe Sea Water Quality Standard (GB 3097-1997) of China (Zhao et al., 2000). The pollution hasdeteriorated the ecology and reduced biodiversity of the waters. From 1983 to 1993, the number of fishspecies 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 thebay. Forty rivers carry 95% of the terrestrial-source pollutants and nutrients into the Bohai Bay (Zhao etal, 2000). This paper reports a recent field investigation of the bay and the results of analysis of thesamples taken from the river mouths around the bay.2 WATER QUALITY IN THE RIVER MOUTHS AROUND BOHAI BAYDuring June 6 to 10, 2001, the authors conducted a field investigation at the mouths of the NewYongding, Jiyun, Haihe, Dagu, Dulijian, Qingjinghuang, New Ziya, Nanpai, Dakou, New Zhangwei, .Majia, Tuhai and Yellow Rivers. These are the most important rivers flowing into the Bohai Bay. Twelvewater samples and 24 sediment samples at 19 river mouths were taken (Fig. 1). The water samples wereanalyzed for concentrations of Hg, Cu, Zn, As, Pb, total nitrogen (TN) and total phosphorus (TP) (Liu etal., 2002; Liu et al., 2003).Dr, Asso. Prof, International Research and Training Center on Erosion and Sedimentation, Beijing 100044,China, E-mail: chliu@ iwhr.comProf, Dept. of Hydraulic Engineering, Tsinghua University & International Research and Training Center onErosion and Sedimentation, Beijing, 100084, China, E-m中国煤化工3 China Institute of Water Resources and Hydropower ReseE-mail: he_ yun@ mail.hf.ah.cnfYHCNMH GNote: The manuscript of this paper was received in June 2002.The revised version was received in Nov. 2002.Discussion open until Dec.2004-326-Intermational Journal of Sediment Research, Vol. 18, No. 4, 2003, pp. 326-332Nw YOyonpdingRiveSampling SitesQTianjin 1New YongdingQikou PortRiverKQul5Jiyun RiverNanpai RiverHuanghua HarbourPortHaihe River6Dakou River11mouth groyneKeNZiya Rives 12Bohai BayDredged sedimentNew Zhangwei Riverof Haie....Tianjin Freight8Majia River16Harbour9Tuhai River,17mouth182Dagu RiverDiaokou RiverDuliujian RiverDongying HarbourFerw/zhangwci River20 e10Dredged sediment 22Gudong groyneof DuliujianQingjinghuang23Qingshuigou-ChaheRiver (Yellow River)Dongying, I1New Ziya RiverQingshuigou River(Yellow River)Fig. 1 Map of Bohai Bay and surrounding area2.1 Water Quality and the Main PollutantsThe water quality was evaluated by employing China's Environmental Quality Standard for SurfaceWater (GHZB 1-1999) (EQSSW). Table 1 lists the classes of water quality at the sampling sites. All theriver 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 withthe eutrophication index showed that the N content at these river mouths was also very high. The mainpollutants in the river mouths between Jiyun to Qikou Port were N and P, and those near the Yellow Rivermouth were N and Hg.Table 1 Classes of water quality and the main pollutants in the waters of the sampling sitesSampling siteClass of water qualityMain pollutantsOver VHg, P, NNew Yongding RiverP, NGroyne of Haihe River mouthHg, P,NFreight harbour of Haihe River mouthI\Duliyjian RiverQingjinghuang RiverINHg, NGudong GroyneQingshuigou Cha-he of the Yellow River中国煤化工Mercury (Hg): Fig. 2 presents the Hg content in the 12 wTYHC N M H G. Higher valuesappear near the Haihe and the Yellow River mouths. The Hg content in the waters at Dongying HarbourInternational Jourmal 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 ug/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 rangedform 0.71 to 1.13 μg/L, which shows relatively higher values. Compared with the data of the 1980s (EPAof China, 1990A; EPA of China, 1990B), the Hg content in the waters near the Haihe river mouth is nowroughly 10 times that of 20 years ago. This reflects that the accelerating water pollution, which is causedby the increasing wastewater discharges of metallurgy, chemical and other industries in Tianjin and theupstream drainage area, has reached an alarming level. The Hg content in the Yellow River mouth is lowand has remained nearly unchanged compared with that of the 1980s, but the waters at Dongying Harbourand Gudong Groyne show significant increases in Hg concentration. This indicates that the wastewaterdirectly discharged by the oil and petrochemicals industries in the Yellow River Delta has caused seriousregional pollution, and that the fearful Hg pollution near the Yellow River mouth is not caused by theYellow River itself.Sampliing sites1. Jiyun river2.2. New Yongding pontClass IV and V of EQSSW3. Haibe groyne4. Haihe harbour5. Dagu river1.6. Dulivjian river7. Qingjinghuang river8. Qikou fishery port9. Dakou rRiver .0.10. Dongying harbour11. Gudong Groyne0L12. Qingshuigou ChaheNo.1!!926789112Sampling siteFig. 2 Hg Concentration in the waters at river mouths around Bohai Bay0.71000Sampling sites: .TPC 1. Jiyun river- Population density800目2. New Yongding port- Average TP3. Haihe groyne6000.4e 5. Dagu river6. Dulujian river0.3400、. Qikou fishery port009. Dakou river:oudong groyie 、12. Qingshuigou-ChaheNo. 16710 11 12Fig. 3 TP Concentration in the waters at river mouths around Bohai BayTotal 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 allthe values except that of the Qingjinghuang River and Tianjin Freight Harbour exceeded 0.20 mg/L, aClass V value of TP according to the EQSSW. The contents between Huanghua Harbour to the YellowRiver 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 inwaters 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 phos中国煤化工is related to humanactivity. Domestic sewage discharge, the quantity of syntfHEndustrial capacity allincrease with increased population density, so the phos,CN M H Geases with increasedpopulation density. If the TP content is averaged in three sections, Tianjin (the Jiyun to Dagu rivers),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 theaverage population density for the same three sections, the same steps can be found. The results of fieldmeasurements 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, whichshows only slight variation (Fig. 4). The relatively higher values appear near the Haihe and the YellowRiver mouths. The TN content is one of the import indexes used to evaluate water quality. High TNcontent in the waters of a bay or lake may cause a red tide or alga bloom. In China, half of the nitrogendischarged 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 TNcontent. Near the Haihe and Yellow River mouths, the TN content is relatively higher. This is becausethere is more domestic sewage and the chemical industry is more concentrated in the Tianjin andDongying areas.| Sampling sites:1. Jiyun riverClass V of the standard of the specific items2. New Yongding portfor eutrophication in lakes and reservoirs3. Haibhe groyne4. Haihe harbour5. Dagu river3I6. Duliujian river7. Qingjinghuang river8. Qikou Fishery port9. Dakou rvr10. Dongying harbour11. Gudong groyne12. Qingshuigou-ChaheNo.I25678101112Sampling siteFig. 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 12water samples. The concentrations of these metals in all of the waters were below the Class II of theEQSSW. The concentrations of Cu, Zn and As were between 0.056 and 0.119 mg/L, 0.067 and 0.118mg/L, and 1.31 and 4.22 μg/L respectively, and the concentrations presented lttle variation along the bay.The contents of Pb were between 0.73 and 16.74 μg/L, among which the contents at the Haihe Rivermouths, 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. Comparedwith the data from 1980s (EPA of China, 1990A; EPA of China, 1990B), the concentration anddistribution area of the Cu, Zn, As and Pb in the waters alng the bay have remained roughly the same,indicating that the water pollution control measures implemenied by the governments of Tianjin and othercities have controlled most of the heavy metals and arse nic oollution in the Bohai Bay.0.14Class I of the EQSSW for ZnDCu mg/L Sampling sts:0.12■Zn mg/LClass Iof the EQSSW for Cu2. Ncw Yongding port0.1|3. Haihe groyne0.080.060.04 I8. Qikou fishery port0.029. Dakou river0No.1678中国煤化工8gshuigou-ChaheHCNMHGFig.5 Cu and Zn Concentrations in the waters at river mouths around Bohau BayInternational Jourmal of Sediment Research, Vol. 18, No. 4, 2003, pp. 326-332- 329-.8rOAsSampling sites:16Class I of the EQSSW for As-50mg/L1. Jiyun river4■Pb2. New Yongding portClass Iof the EQSSW for Pb3. Haihe groyne124. Haibe harbour5. Dagu river6. Duliujian river7. Qingjinghuang river8. Qikou fishery port9. Dakou river10. Dongying harbour11. Gudong groyne12. Qingshuigou ChaheNo. 1671011Sampling siteFig. 6 As and Pb Concentrations in the waters at river mouths around Bohai Bay2.2 Contribution of river mouth pollution to the eutrophication of Bohai BayOf the four sea areas in China, the Bohai Sea, the South China Sea, the East China Sea and the YellowSea, the Bohai Sea has the smallest number of red tide occurrences recorded, with only 5 from 1933 to1989, which is 2% of the total number of red tides recorded in China. But the number of red tides hasbeen increasing since the 1990s (Zhang, 1994). During the period from 1998 to 2000, unusual red tideswith 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 whenthe nutrients (N, P) input is larger than output, or nutrients (N, P) accumulation is larger thanconsumption. Red tides may occur when nutrients are enriched in waters (Fang et al., 2001), so it is veryimportant to study the sources of the nutrients in the Bohai Bay.Table 2 Degrees of eutrophication in the river mouths around Bohai BayTNPClass of waterDegree ofcontentquality accordingeutrophication(mg/L)to TNtoTP(%)*Jiyun River3.250.66Over V85_New Yongding River3.900.3086Haihe Groyne0.2137Haihe Freight Harbour1.930.13Over v7Dagu River1.670.2375Duliujian River2.500.2581Qinginghuang River1.680.10Qikou Port2.330.2880Dakou River2.530.05I\Dongying Harbour2.940.03_I\83Gudong Groyne5.530.02IIQingshuigou Cha-he77* Based on the evaluation standard for eutrophication by the National Research Institute of Disaster in JapanNo general standard or method to evaluate the degree of eutrophication has been established. Muchresearch has reported that the concentration of N and P i中国煤化工to eutrophication. Ingeneral, it is believed that waters are in a state of eutroMYH_trations of inorganicnitrogen and total phosphorus reach 0.3mg/L and 0.02mCN M H G"" 198. Comparingthe TP concentrations found in the waters at the river mouths along the Bohai Bay with these values, all. 330-Intermational Journal of Sediment Research, Vol. 18, No. 4, 2003, pp. 326-332the river mouths are in a state of eutrophication. The EQSSW has standards for the specific itemsinvolved in the eutrophication of lakes and reservoirs, and the results of a comparison with thesestandards 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 takenat the river mouths from the Dakou to the Yellow rivers. The TN and TP content in the waters of theBohai Bay have reached dangerous loads for eutrophication.The National Research Institute of Disaster in Japan put forward a method to evaluate the degree ofeutrophication, in which the degree of eutrophication is determined by a percentage based on the 9 valuesof components such as TN, TP, chloropbyll, transparency and oxygen demand (Jin et al, 1989). Theeutrophication percentages for the twelve sarmples were determined applying only the TN and TP contentsto this method, and are also listed in the Table 2. The values were between 75 and 93% which indicatesthat a serious eutrophication problem exists in these waters.ldentical conclusions were reached using different evaluation methods: that the waters of the rivermouths around the Bohai Bay are all in a state of serious eutrophication, and the terrestrial pollution inthe bay is one of the main reasons for the increasing eutrophication and occurrence of red tide events inthe bay.3 RELATIONSHIP BETWEEN WATER QUALITY AND SEDIMENT QUALITYMost pollutants have similar distribution in the water and sediment along the bay; Hg, Zn and TP havethe most similar distributions in water and sediment. Fig.7 shows this similarity of TP. The similarity ofdistribution means that the pollutants are transferred between the sediment and overlaying water whichare in a state of dynamic balance. Affected by the tidal flow, the bed sediment and suspended sediment inthe river mouths are constantly being exchanged, i.e. the suspended sediment in the water is continuouslyfalling to the river bed to become part of the bed load while the bed sediment erodes and becomessuspended sediment simultaneously. In this process, the suspended sediment may absorb the pollutants inthe water and deposit them on the bottom, and the bed sediment may release the pollutants from thebottom during resuspension by the tide and waves.0.080.80.7 8 Sampling sites:0.6包1. Jiyun三2. New Yongding0.5等3.Haihe0.44. Dagu0.050.3号s. Duliujian0.20.04-- TP content in sediment01县6. Qingjinghuang..◆..TP content in waterg 7. Qikou porte 0.03No. 145690 e8. Dakou9. Qingshuigou-ChaheSampling siteFig. 7 Distributions of TP content in the water and sediment at the river mouths4 CONCLUSIONSThe water samples were taken from 12 river mouths around Bohai Bay including the Jiyun, NewYongding, 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 forSurface Water (GHZB 1-1999). The main pollutants are N, P and Hg. The most serious water pollution byHg appeared in the waters near the Yellow and Haihe River I” 中国煤化工reases from thenorth to the south along the bay which coincides with the (density. (2) Acomparison of the current data with data from the 1980s shows:YHCNMHGIginthewatersof the Haihe River mouth is 10 times that of 20 years ago. Though the concentration of Hg in the watersat the Yellow River mouth has remained nearly unchanged for the same 20 years, local Hg pollution in theIntermnational 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 hasreached a dangerous amount of eutrophication load; it is obvious that the terrestrial pollution flowing intothe bay is one of the main sources for the increasing eutrophication and the increasing occurrence of redtide events in the bay. (4) A similar distribution concentration for most of the pollutants were foundbetween the sediment and waters along the bay, indicating the pollutants are transferred between thesediment and overlaying water which are in a state of dynamic balance.ACKNOWLEDGMENTThe work is supported by the National Natural Science Foundation of China (NSFC) and the HongKong Research Grants Council (RGC) (No. 50379056, No.50318003).REFERENCESEPA of China, 1990A, Research on Polution Control of the Bohai and Yellow Seas, Science Press, Beijing, China (inEPA of China, 1990B, Atlas of Research on Pollution Control of the Bohai and Yellow Seas, Science Press, Beijing,China (in Chinese).EPA of China, 1997, Analysis Methods for Water and Wastewater, Chinese Environmental Science Publisher, Beijing(in Chinese).Fang, Z. G. and Mu, Y. X., 2001, Study on the Eutrophication Tendency in Liaodong Bay of the Bohai Sea, ACTAScientiae Circumstantiae, Vol. 27, No. 6, pp. 15-17 (in Chinese).Hu, S. 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