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The nutrient, total petroleum hydrocarbon and heavy metal contents in the seawater of Bohai Bay, China: Temporal–spatial variations, sources, pollution statuses, and ecological risks
Marine Pollution Bulletin xxx (2015) xxx–xxx
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The nutrient, total petroleum hydrocarbon and heavy metal contents in the seawater of Bohai Bay, China: Temporal–spatial variations, sources, pollution statuses, and ecological risks Shitao Peng ⇑ Laboratory of Environmental Protection in Water Transport Engineering, Tianjin Research Institute for Water Transport Engineering, Tianjin 300456, China
a r t i c l e
i n f o
Article history: Available online xxxx Keywords: Pollution status Ecological risk Nutrients Total petroleum hydrocarbons Heavy metals Bohai Bay
a b s t r a c t Seawater samples collected between 2007 and 2012 were determined the concentrations of nutrient (DIN and DIP), total petroleum hydrocarbon (TPH), and six different heavy metals (As, Cu, Zn, Pb, Cd and Hg). The DIN, DIP, TPH, Pb, and Cd concentrations decreased from 2007 to 2009 or 2010 and increased after 2010. However, the Hg and Cu concentrations increased from 2007 to 2012. In contrast, the As and Zn gradually decreased during the study period. All of the pollutant concentrations gradually decreased from the shoreline to the offshore sites. PCA result showed that urban and port areas, agriculture, and atmospheric deposition were the main sources of pollutants in the bay. Although most of the pollutants were present at concentrations bellow the highest seawater quality standards in China, eutrophication was a risk in Bohai Bay. In addition, DIN was the main pollutant and was responsible for the eutrophication risk in Bohai Bay. Ó 2015 Published by Elsevier Ltd.
Semi-enclosed bays are generally important areas for economic development and aquaculture (Chen and Yu, 2011; Gu et al., 2012). The environmental quality in these bays significantly influences economic growth and social progress at regional and larger scales (Peng et al., 2013). Furthermore, these bays serve as filters for trapping natural and anthropogenic materials that are transferred from continents to the open seas. Consequently, many pollutants have been discharged into semi-enclosed bays due to anthropogenic activities. These pollutants seriously threaten coastal and marine ecosystems and their inhabitants, resulting in structural and functional ecosystem changes, eutrophication, red-tide, increased fish and benthos mortality, decreased fishery yields, and greater economic loss (Gao et al., 2014). Bohai Bay is one of most important semi-enclosed bays in northern China and is located in the western Bohai Sea. Bohai Bay is surrounded by large cities, including Beijing (the capital city of China) and Tianjin. Tianjin is one of four municipalities surrounding the bay and is an important commercial and industrial center in China with an area of approximately 11,200 km2 and a population of 11 million. Approximately one billion tons of wastewater is discharged from Beijing, Tianjin, and Hebei province into Bohai Bay every year (Duan et al., 2010). Consequently, large
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quantities of contaminants have been discharged into the bay that can severely threaten the ecosystem. Nitrogen, phosphorus, petroleum hydrocarbons, and heavy metals are considered the four most common pollutants in Bohai Bay (Li et al., 2010). Recently, several publications have recorded the presence of these contaminants in seawater from Bohai Bay. For example, Peng et al. (2009) reported variations in the nitrogen and phosphorus concentrations in the seawater from 1996 to 2006. Dai et al. (2009) reported the decennary (1996–2005) variations of dissolved heavy metals in the seawater of Bohai Bay. In addition, Li et al. (2010) reported temporal and spatial trends in the total petroleum hydrocarbon contents in seawater from Bohai Bay between 1996 and 2005. These studies indicated long-term variations of the four main contaminants in the seawater of Bohai Bay before 2006. However, no information is available regarding the pollutant concentrations after 2006. Many important events have occurred in this region since 2006. For example, the Summer Olympic Games were held in Beijing in 2008. To increase the air quality in this region, strict environmental protection policies were put into practice in Beijing, Tianjin, and Hebei Province. These policies potentially improved the seawater quality in the bay. Meanwhile, the Tianjin Binhai New District (TBND), a pilot area undergoing a special national integrated development plan in China that has drawn concern from the rest of the world, was build in 2006 (Qin et al., 2010). Many industries, including chemical, electronic, and manufacturing industries, have been built along the bay. These industries have potentially increased
http://dx.doi.org/10.1016/j.marpolbul.2015.03.032 0025-326X/Ó 2015 Published by Elsevier Ltd.
Please cite this article in press as: Peng, S. The nutrient, total petroleum hydrocarbon and heavy metal contents in the seawater of Bohai Bay, China: Temporal–spatial variations, sources, pollution statuses, and ecological risks. Mar. Pollut. Bull. (2015), http://dx.doi.org/10.1016/j.marpolbul.2015.03.032
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S. Peng / Marine Pollution Bulletin xxx (2015) xxx–xxx
the discharge of wastewater into the bay. Additionally, ports and marine transportation have flourished in the bay area in recent years, which has likely influenced the water quality of the bay. However, little information is available regarding the concentrations of these four pollutants in the seawater in Bohai Bay. In this study, the nitrogen, phosphorus, total petroleum hydrocarbon, and heavy metal (As, Cu, Zn, Pb, Cd and Hg) concentrations in Bohai Bay seawater were collected from 2007 to 2012. The main objectives of this study were to (1) investigate the spatial and temporal variations of the pollutants in the seawater in Bohai Bay, (2) discriminate between the possible sources of pollution using multivariate analysis techniques, and (3) assess the status of the pollutants and determine the resulting ecological risk. Fifteen sampling sites were selected in Bohai Bay (Fig. 1). Station 1 is located on the coast of the Hangu District of Tianjin, near one of the largest chemistry plants in China. Station 3 is located in the Beitang Estuary, which serves as a pathway for many rivers, including the Yongdingxin River, Beiyun River, Chaobaixin River, Jiyun River, and Beijing Drainage River, that flow into Bohai Bay. Station 4 is located in the Dagu Drainage River estuary near Tianjin Port. Three sampling expeditions were carried out during three periods in one year (i.e., spring (May), summer (August) and winter (November)) for 6 years (2007–2012). Surface water (10–50 cm) was collected to determine the concentrations of nutrients (nitrogen and phosphorus), total petroleum hydrocarbons (TPH), and heavy metals (As, Cu, Zn, Pb, Cd and Hg) in the seawater. All samples were immediately filtered using 0.45 lm filters. The samples that were used to determine the nutrient contents were stored in a pre-cleaned plastic bottle and acidified with 98% H2SO4. In addition, the samples that were used for the heavy metal measurements were acidified to pH < 2 using suprapure HNO3. These samples were stored in sterilized glass jars and transported back to the laboratory on ice where they were immediately frozen until analysis.
The concentrations of ammonium (NH4–N), nitrate nitrogen (NO3–N), nitrite (NO2–N), and soluble reactive phosphorus (SRP) were determined following the standard methods of the APHA (1998). These measurements were completed within 24 h of sampling. The method detection limit for NH4–N, NO3–N, NO2–N, and SRP, were 4, 6, 3, and 1.4 lg/L, respectively. Because the nitrite and ammonium concentrations were negligible relative to the nitrate concentrations in this study, the three nitrogen sources were integrated into a single value of dissolved inorganic nitrogen (DIN). The total petroleum hydrocarbon (TPH) concentrations were determined using ultra-violet fluorescence spectroscopy according to the national standard method of China (GAQSIQ and SAC, 2008). The method detection limit for TPH was 6.2 lg/g. The heavy metal concentrations were determined using an Agilent 7500a ICP-MS (Agilent, USA). The quality control and assurance system in this study included reagent blanks, replicate samples, and certified international reference materials. The standard deviations of triplicate measurements were less than 5.0%. The limits of detection were 0.005 lg/L for Hg and Pb; 0.01 lg/L for As, Cd, and Cu; and 0.02 lg/L for Zn. The recoveries of the metals varied from 83% to 114%. The pollutions statuses of the different pollutants were assessed by comparing the detected pollutant concentrations to the seawater quality standards of China (GB 3097-1997, China), which are shown in Table 1 (SEPA, 1998). Different ecological risks result from different contaminants. For nitrogen and phosphorus, the ecological risks include the possibility of eutrophication in aquatic systems. Eutrophication has become a significant worldwide problem and catastrophically affects aquaculture and local economies (Richlen et al., 2010). Therefore, the ecological risks of nitrogen and phosphorus were assessed by using the trophic index (TRIX), which is calculated formulas follows (Vollenweider et al., 1998):
Fig. 1. Sampling sites in Bohai Bay.
Please cite this article in press as: Peng, S. The nutrient, total petroleum hydrocarbon and heavy metal contents in the seawater of Bohai Bay, China: Temporal–spatial variations, sources, pollution statuses, and ecological risks. Mar. Pollut. Bull. (2015), http://dx.doi.org/10.1016/j.marpolbul.2015.03.032
S. Peng / Marine Pollution Bulletin xxx (2015) xxx–xxx Table 1 Seawater quality standard of China for the selected pollutants (lg/L). Gradea
DIN
DIP
Hg
Cu
Pb
Cd
As
Zn
TPH
Grade-I Grade-II Grade-III
200 300 400
15 30 45
0.05 0.20 0.50
5.0 10 50.0
1.0 5.0 10
1.0 5.0 10
20 30 50
20 50 100
50 300 500
a The Grade-I refer to the fairly clean seawater, which can be used for mariculture, nature reserve, and endangered species reserve. The Grade-II indicates that seawater are clean, which can be used to marine aquiculture, human recreation leisure activities such as swimming. Grade-III indicates that seawater can be used to industry and tourism site.
TRIX ¼
LogðChl-a ½%DO DIN SRP þ 1:5Þ 1:2
where Chl-a, DIN and SRP are the concentrations of chlorophyll-a, dissolved inorganic nitrogen and soluble reactive phosphorus, respectively. In addition, %DO is the absolute value of the oxygen saturation deviation and is calculated as |100 %DO|. The four following trophic levels were defined: high with TRIX < 4, good with 4 < TRIX < 5, fair with 5 < TRIX < 6, and poor with TRIX > 6 (HerreraSilveira and Morales-Ojeda, 2009). The information of DO and Chl-a were presented in supplementary material (Figs. S1 and S2). TPH and heavy metals are threats to health. Thus, the ecological risks of TPH and heavy metals were assessed based on their adverse biological effects by using the reference table recommended by the National Oceanic and Atmospheric Administration (NOAA, 1999). The temporal and spatial differences of the different selected pollutants were performed by using a two-way analysis of variance (ANOVA). Principal component analysis (PCA) was used to determine the sources of the pollutants in the bay. Statistical significance was set at p < 0.05. The selected pollutant concentrations in the seawater from Bohai Bay collected from 2007 to 2012 are shown in Fig. 2. The average concentrations of the selected pollutants in the seawater from the 15 sites significantly varied from season to season (P < 0.01). In general, most of the selected pollutants decreased as follows: summer > winter > spring, with the summer month having the highest concentrations of all but Hg, As and Zn (their highest concentrations were found in the winter). It is possible that summer is the wet season, which would result in greater pollutants inputs to the bay by rivers (Zhou et al., 2014). In the present study, the concentrations of DIN, DIP, TPH, Hg, Cu, Pb, Cd, As, and Zn were in the range of 246–1417, 3.20– 36.61, 8.47–76, 0.003–0.36, 0.16–7.17, 0.17–9.55, 0.02–0.68, 0.25–4.02, and 17.3–90 lg/L, respectively. The concentrations in the present study were all lower that in the previous studies (e.g. Dai et al., 2009; Peng et al., 2009; Li et al., 2010). For example, the concentrations of DIN, DIP, and TPH were 103–2432, 0.9–120, and 8.47–76 lg/L, respectively, during 1996–2006 (Peng et al., 2009; Li et al., 2010). The maximum concentrations of Cu, Zn, Pb, Hg, and Cd were 16.3, 422, 40.4, 0.23, 0.89 lg/L respectively, during 1996–2005 (Dai et al., 2009), which were also higher than those in the present study. These results indicate that the concentrations of the selected pollutants decreased since 1996. The nutrient (DIN and DIP), TPH, Pb, and Cd concentrations generally decreased from 2007 to 2009 or 2010 and increased after 2010 (Fig. 3). The decreasing concentrations were explained by the promulgation of environmental protection policies. The first policy that was implemented is The Plan of Cleaning Bohai Sea. This policy was promulgated in the Bohai rim area by the Central Government of China in 2001 and aimed to halt industrial waste discharge to monitor environmental pollution and restore the damaged ecological system. One of our previous studies reported that the THP and heavy metal concentrations in sediment from
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Bohai Bay gradually decreased after this policy was put into place (Zhou et al., 2014). The second policy that was promulgated was the environmental protection program for the 2008 Summer Olympic Games in Beijing. In this case, the effluent was subjected to stricter regulations. To improve the environmental quality for the 2008 Summer Olympic Games, many protection programs were used to regulate the effluent in Beijing, Tianjin, and Hebei Province. For example, sewage treatment systems were installed and water pollution control regulations were enforced in Tianjin (Wu and Gao, 2010). These regulations significantly decreased waste air and water effluents. In addition, the pollution sources were controlled. Many industry plants that resulted in serious pollution were closed before 2008. In addition, the public and scientific awareness related to the environmental protection for the 2008 Summer Olympic Games helped to decrease the levels of pollution in the bay. Therefore, many of the selected pollutant concentrations decreased before 2009 or 2010. The concentrations of pollutant increased after 2009 was mainly attributed to the rapid development of the Tianjin Binhai New District (TBND). Within the last five years, the development of the chemical, electronics, port, and marine transportation industries has increased in the TBND. Such increases could produce more wastewater that is discharged into the bay. For example, the sewage discharge in 2011 was 628 million Mt, which was 1.1 times greater than it was in Tianjin in 2006 (Tianjin Environmental Protection Bureau, 2007, 2012). Furthermore, many industry plants that resulted in serious pollution were re-opened after the 2008 Summer Olympic Games. These enterprises discharge some of their wastewater into rivers, which was then transported into the bay with little to no treatment (Ren et al., 2010). Such discharge may increase the pollutant concentrations in the seawater from Bohai Bay. In addition, many pollution accidents have occurred in Bohai Bay in recent years (Zhou et al., 2014). Particularly an oil spill occurred that could cause a variety of environmental problems in the sea (White et al., 2012). For example, the oil spill of the Penglai 19-3 drilling platform in the Bohai Sea in June 2011 is one of the most serious oil spills that have occurred in China. This oil spill polluted 840 km2 of marine area and resulted in catastrophic economic losses for local aquaculture (Liu et al., 2015). Thus, this oil spill likely explains the occurrence of the highest TPH concentrations in 2011 (Fig. 3). The spatial variations of the selected pollutant concentrations generally gradually decreased from the shoreline to the offshore sites (Fig. 4). This finding is agree with those of previous studies regarding the spatial distributions of nutrients, THP, and heavy metals in seawater from Bohai Bay (Peng et al., 2009; Dai et al., 2010; Li et al., 2010). This finding occurred because terrestrial inputs are an important source of the pollutants in the bay, mainly riverine inputs and industrial discharge (Zhou et al., 2014). These two inputs have been considered as the most important sources of heavy metal concentrations for the seawater in the coastal areas of Bohai Bay (Wang and Wang, 2007). Thus, it is important to control riverine inputs and industrial discharge to improve the water quality of Bohai Bay. In this study, the highest pollutant concentrations were generally found at S3 or S4 (Fig. 4) because these two sampling sites are located in the estuary. In this study, the S3 sampling site is located in the Beitang estuary. This estuary received fresh and wastewater from the new Yongding, Chaobaixin, and Jiyun Rivers and the Tianjin Effluent Canal, before discharging into the Bohai Bay. The Beijing Drainage River, a major recipient of industrial effluents from Beijing, also transports a large amount of wastewater into Bohai Bay through the Beitang estuary (Ren et al., 2010). This result indicates that this estuary was subject to heavy anthropogenic influences from rapid economic development and urbanization in Tianjin and Beijing (Qin et al., 2010). Thus, it is not surprising that high concentrations of pollutants were found in this estuary. The S4 site is located in the Dagu Drainage estuary.
Please cite this article in press as: Peng, S. The nutrient, total petroleum hydrocarbon and heavy metal contents in the seawater of Bohai Bay, China: Temporal–spatial variations, sources, pollution statuses, and ecological risks. Mar. Pollut. Bull. (2015), http://dx.doi.org/10.1016/j.marpolbul.2015.03.032
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S. Peng / Marine Pollution Bulletin xxx (2015) xxx–xxx
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Fig. 2. Seasonal variations of the selected pollutants in the seawater.
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30
0.00
0
0.0 2007 2008 2009 2010 2011 2012
2007 2008 2009 2010 2011 2012
2007 2008 2009 2010 2011 2012
Fig. 3. Temporal variations of the selected pollutants in seawater.
Please cite this article in press as: Peng, S. The nutrient, total petroleum hydrocarbon and heavy metal contents in the seawater of Bohai Bay, China: Temporal–spatial variations, sources, pollution statuses, and ecological risks. Mar. Pollut. Bull. (2015), http://dx.doi.org/10.1016/j.marpolbul.2015.03.032
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S. Peng / Marine Pollution Bulletin xxx (2015) xxx–xxx
Fig. 4. Spatial variations of the pollutants concentration (lg/L).
This river is the main drainage river that contains effluents from Tianjin. Approximately 800,000 Mt/d of effluent were discharged into Bohai Bay from this estuary (Lü et al., 2007). Thus, this estuary may increase the pollutant concentrations at the S4 sampling site. Moreover, the S4 sampling site was located near Tianjin Port. This port was usually more heavily polluted than other water due to pollution from the ships (Zhou et al., 2014). However, some pollutants showed a high concentration of some heavy metals at other sampling sites (Fig. 4). For example, the highest Hg, As, and Zn concentrations were found at the S7, S10, and S2 sites, respectively. In this study, the S2 and S7 sites were located on the coast, while the S10 site was located offshore. This result indicates that other inputs may also exist for this bay. In this present study, a principal component analysis (PCA) was used to identify the sources of the selected pollutants in the seawater from Bohai Bay. The first three principal components (PC) explained 84.88% of the total variance in the original data (Table 2). This indicates that three main sources of pollutants existed in Bohai Bay. The first PC (PC I) was included strong positive values for DIN, DIP, THP, Cu, Pb, and Zn and indicated that they originated from the port. The nutrients and metals were of urban
Table 2 Principal component analysis (PCA) of the pollutants.
DIN DIP TPH Hg Cu Pb Cd As Zn Eigenvalue Explained variance (%) Total explained variance (%)
PC I
PC II
PC III
0.91 0.93 0.93 0.11 0.69 0.76 0.23 0.09 0.78 4.51 50.09 50.09
0.14 0.02 0.07 0.85 0.43 0.30 0.87 0.17 0.15 1.72 19.10 69.19
0.26 0.15 0.08 0.21 0.36 0.45 0.08 0.94 0.40 1.41 15.69 84.88
origin, which have been demonstrated in previous studies (e.g., Mendiguchía et al., 2007; Guéguen et al., 2012). The TPH mainly originated from the port due to shipping activities. In addition, Cd and Hg were in the second PC (PC II), and mainly originated from agriculture due to fertilizer use (Wu et al., 2010). Arsenic
Please cite this article in press as: Peng, S. The nutrient, total petroleum hydrocarbon and heavy metal contents in the seawater of Bohai Bay, China: Temporal–spatial variations, sources, pollution statuses, and ecological risks. Mar. Pollut. Bull. (2015), http://dx.doi.org/10.1016/j.marpolbul.2015.03.032
S. Peng / Marine Pollution Bulletin xxx (2015) xxx–xxx
presented a singular origin and was not related to any other pollutants (Table 2). The probable origin of As was atmospheric deposition, which resulted from the volatilization of As from coal during combustion (Chen et al., 2013). Thus, high concentrations of As were found during the winter (Fig. 2) because winter is the heating period in north China and coal combustion is the main source of heat. In this study, the pollution statuses of the selected pollutants were assessed by comparing their concentrations with the seawater quality standards of China (Table 1). Most of the selected pollutants met the highest seawater quality standards in China, except for the DIN and Zn (Fig. 2). This result indicates that the DIN and Zn are the main pollutants in Bohai Bay. Furthermore, some of the pollutants were greater than Grade-II in some years. For example, 66.67% of the samples had Pb concentrations that exceeded Grade-III. The DIP, THP, Hg, Cu and Hg concentrations in some years and at some sampling stations were above the Grade-III values. As shown in Fig. 5, the percentage of the selected Grade-I pollutants (Cd and DIP are exceptions) increased between 2007 and 2012, which indicated that the pollution status was aggravated in recent years in Bohai Bay. The eutrophication risk of the nutrients ranged form good to fair in Bohai Bay during the study periods (Fig. 6). High or poor levels were not observed in Bohai Bay for any year, indicating that the eutrophication risk was relatively low. However, the TRIX value decreased from 2001 to 2009 and increased after 2009. In addition, the status of 2011 and 2012 was fair, suggesting a potential eutrophication risk in Bohai Bay in recent years (Fig. 6). However, no ecological risks resulted from the other pollutants
Fair
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except, of for Cu in 2011 and 2012 (Table 3). Furthermore, the DIN concentrations exceeded the Grade-III seawater quality standards in China in all years (Fig. 2). These finding demonstrated that DIN has been the main pollutant in the seawater of Bohai Bay, and agrees with our earlier study from 1996 to 2006 (Peng et al., 2009). Due to nitrogen is a key element for phytoplankton (Seeyave et al., 2013; Treibergs et al., 2014). It is also the most important factor that can induce eutrophication in water system (Beversdorf et al., 2013; Loza et al., 2014). Due to the high concentrations of DIN in seawater, phytoplankton systems have dramatically changed in recent decade in Bohai Bay (Peng et al., 2012). Specifically, the primary production decreased while eutrophication became more severe (Tang et al., 2003). Although many environmental
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Fig. 6. The variations of TRIX.
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As
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Grade-III
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Fig. 5. The variations of the pollution status.
Please cite this article in press as: Peng, S. The nutrient, total petroleum hydrocarbon and heavy metal contents in the seawater of Bohai Bay, China: Temporal–spatial variations, sources, pollution statuses, and ecological risks. Mar. Pollut. Bull. (2015), http://dx.doi.org/10.1016/j.marpolbul.2015.03.032
S. Peng / Marine Pollution Bulletin xxx (2015) xxx–xxx Table 3 The ecological risks of THP and heavy metals.
CCC CMC 2007 2008 2009 2010 2011 2012
TPH
Hg
Cu
Pb
Cd
As
Zn
300
2.1 0.94 N N N N N N
4.8 3.1 N N N N CMC CCC
217 8.1 N N N N N N
43 9.3 N N N N N N
69 36 N N N N N N
95 81 N N N N N N
N N N N N N
CMC (Criteria Maximum Concentration) and CCC (Criteria Continuous Concentration) indicate that the acute and chronic toxicity, respectively (NOAA, 1999). N indicate that no risk.
protection policies have been promulgated since 2000, eutrophication risks have increases in recent years (Fig. 6). This increase is attributed to the greater discharge of wastewater discharge into Bohai Bay, although most of the wastewater was treated and met the China effluent criteria. Therefore, to decrease the eutrophication risks in the Bohai Bay, it is important to control the total emissions. The ecological risks of the THP and heavy metals were assessed based on their adverse biological effects by using the reference table recommended by the National Oceanic and Atmospheric Administration (NOAA). The results indicated that only Cu met the CMC and CCC criteria of the NOAA, which occurred in 2011 and 2012, respectively (Table 3). Thus, the ecological risks of THP and heavy metals in seawater from Bohai Bay were relatively low. Acknowledgments This work was supported by the National Nonprofit Institute Basic Research Fund of China (TKS150217), National Natural Science Foundation of China (21307045), International S&T Cooperation Program of China (2015DFA90250), and National Special Fund for Basic Science and Technology of China (2012FY112500). Appendix A. Supplementary material Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.marpolbul.2015. 03.032. References APHA, 1998. Standard Methods for the Examination of Water and Wastewater, 20th ed. APHA-AWWA-WPCF, Washington DC. Beversdorf, L.J., Miller, T.R., McMahon, K.D., 2013. The role of nitrogen fixation in cyanobacterial bloom toxicity in a temperate, eutrophic lake. PloS One 8, e56103. Chen, T., Yu, K., 2011. P/Ca in coral skeleton as a geochemical proxy for seawater phosphorus variation in Daya Bay, northern South China Sea. Mar. Pollut. Bull. 62, 2114–2121. Chen, J., Liu, G., Kang, Y., Wu, B., Sun, R., Zhou, D., Wu, D., 2013. Atmospheric emissions of F, As, Se, Hg, and Sb from coal-fired power and heat generation in China. Chemosphere 90, 1925–1932. Dai, M., Peng, S., Xu, J., Liu, C., Jin, X., Zhan, S., 2009. Decennary variations of dissolved heavy metals in seawater of Bohai Bay, North China. Bull. Environ. Contam. Toxicol. 83, 907–912. Duan, L., Song, J., Li, X., Yuan, H., Xu, S., 2010. Distribution of selenium and its relationship to the eco-environment in Bohai Bay seawater. Mar. Chem. 121, 87–99. Gao, X., Zhou, F., Chen, C.T.A., 2014. Pollution status of the Bohai Sea: an overview of the environmental quality assessment related trace metals. Environ. Int. 62, 12– 30. GAQSIQ (General Administration of Quality Supervision, Inspection and Quarantine of the People’s Republic of China), SAC (Standardization Administration of the People’s Republic of China), 2008. The Specification for Marine Monitoring—Part 4: Seawater Analysis.
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Long-term (1996–2006) variation of nitrogen and phosphorus and their spatial distributions in Tianjin Coastal Seawater. Bull. Environ. Contam. Toxicol. 83, 416–421. Peng, S., Qin, X., Shi, H., Zhou, R., Dai, M., Ding, D., 2012. Distribution and controlling factors of phytoplankton assemblages in a semi-enclosed bay during spring and summer. Mar. Pollut. Bull. 64, 941–948. Peng, S., Zhou, R., Qin, X., Shi, H., Ding, D., 2013. Application of macrobenthos functional groups to estimate the ecosystem health in a semi-enclosed bay. Mar. Pollut. Bull. 74, 302–310. Qin, X., Sun, H., Wang, C., Yu, Y., Sun, T., 2010. Impacts of crab bioturbation on the fate of polycyclic aromatic hydrocarbons in sediment from the Beitang estuary of Tianjin, China. Environ. Toxicol. Chem. 29, 1248–1255. Ren, H., Liu, H., Qu, J., Berg, M., Qi, W., Xu, W., 2010. The influence of colloids on the geochemical behavior of metals in polluted water using as an example Yongdingxin River, Tianjin, China. Chemosphere 78, 360–367. Richlen, M.L., Morton, S.L., Jamali, E.A., Rajan, A., Anderson, D.M., 2010. The catastrophic 2008–2009 red tide in the Arabian Gulf region, with observations on the identification and phylogeny of the fish-killing dinoflagellate Cochlodinium polykrikoides. Harmful Algae 9, 163–172. Seeyave, S., Probyn, T., Álvarez-Salgado, X.A., Figueiras, F.G., Purdie, D.A., Barton, E.D., Lucas, M., 2013. Nitrogen uptake of phytoplankton assemblages under contrasting upwelling and downwelling conditions: the Ría de Vigo, NW Iberia. Estuar. Coast. Shelf Sci. 124, 1–12. SEPA (State Environmental Protection and Administration of China), State Oceanic Administration of China, 1998. Sea Water Quality Standard GB 3097–1997. Tang, Q., Jin, X., Wang, J., Zhuang, Z., Cui, Y., Meng, T., 2003. Decadal-scale variations of ecosystem productivity and control mechanisms in the Bohai Sea. Fish. Oceanogr. 12, 223–233. Tianjin Environmental Protection Bureau, 2007. Tianjin Environmental Quality Bulletin of 2006. Tianjin Environmental Protection Bureau, 2012. Tianjin Environmental Quality Bulletin of 2011. Treibergs, L.A., Fawcett, S.E., Lomas, M.W., Sigman, D.M., 2014. Nitrogen isotopic response of prokaryotic and eukaryotic phytoplankton to nitrate availability in Sargasso Sea surface waters. Limnol. Oceanogr. 59, 972–985. Vollenweider, R.A., Giovanardi, F., Montanari, G., Rinaldi, A., 1998. Characterization of the trophic conditions of marine coastal waters with special reference to the NW Adriatic Sea: proposal for a trophic scale, turbidity and generalized water quality index. Environmetrics 9, 329–357. Wang, C.Y., Wang, X.L., 2007. Spatial distribution of dissolved Pb, Hg, Cd, Cu and As in the Bohai Sea. J. Environ. Sci. 19, 1061–1066. White, H.K., Hsing, P.Y., Cho, W., Shank, T.M., Cordes, E.E., Quattrini, A.M., Nelson, R.K., Camilli, R., Demopoulos, A.W.J., German, C.R., Brooks, J.M., Roberts, H.H., Shedd, W., Reddy, C.M., Fisher, C.R., 2012. Impact of the deepwater horizon oil spill on a deep-water coral community in the Gulf of Mexico. Proc. Natl. Acad. Sci 109, 20303–20308. Wu, G., Cao, S., 2010. Mercury and cadmium contamination of irrigation water, sediment, soil and shallow groundwater in a wastewater-irrigated field in Tianjin, China. Bull. Environ. Contam. Toxicol. 84, 336–341. Wu, S., Xia, X., Lin, C., Chen, X., Zhou, C., 2010. Levels of arsenic and heavy metals in the rural soils of Beijing and their changes over the last two decades (1985– 2008). J. Hazard. Mater. 179, 860–868. Zhou, R., Qin, X., Peng, S., Deng, S., 2014. Total petroleum hydrocarbons and heavy metals in the surface sediments of Bohai Bay, China: long-term variations in pollution status and adverse biological risk. Mar. Pollut. 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Please cite this article in press as: Peng, S. The nutrient, total petroleum hydrocarbon and heavy metal contents in the seawater of Bohai Bay, China: Temporal–spatial variations, sources, pollution statuses, and ecological risks. Mar. Pollut. Bull. (2015), http://dx.doi.org/10.1016/j.marpolbul.2015.03.032
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The nutrient, total petroleum hydrocarbon and heavy metal contents in the seawater of Bohai Bay, China: Temporal–spatial variations, sources, pollution statuses, and ecological risks Shitao Peng ⇑ Laboratory of Environmental Protection in Water Transport Engineering, Tianjin Research Institute for Water Transport Engineering, Tianjin 300456, China
a r t i c l e
i n f o
Article history: Available online xxxx Keywords: Pollution status Ecological risk Nutrients Total petroleum hydrocarbons Heavy metals Bohai Bay
a b s t r a c t Seawater samples collected between 2007 and 2012 were determined the concentrations of nutrient (DIN and DIP), total petroleum hydrocarbon (TPH), and six different heavy metals (As, Cu, Zn, Pb, Cd and Hg). The DIN, DIP, TPH, Pb, and Cd concentrations decreased from 2007 to 2009 or 2010 and increased after 2010. However, the Hg and Cu concentrations increased from 2007 to 2012. In contrast, the As and Zn gradually decreased during the study period. All of the pollutant concentrations gradually decreased from the shoreline to the offshore sites. PCA result showed that urban and port areas, agriculture, and atmospheric deposition were the main sources of pollutants in the bay. Although most of the pollutants were present at concentrations bellow the highest seawater quality standards in China, eutrophication was a risk in Bohai Bay. In addition, DIN was the main pollutant and was responsible for the eutrophication risk in Bohai Bay. Ó 2015 Published by Elsevier Ltd.
Semi-enclosed bays are generally important areas for economic development and aquaculture (Chen and Yu, 2011; Gu et al., 2012). The environmental quality in these bays significantly influences economic growth and social progress at regional and larger scales (Peng et al., 2013). Furthermore, these bays serve as filters for trapping natural and anthropogenic materials that are transferred from continents to the open seas. Consequently, many pollutants have been discharged into semi-enclosed bays due to anthropogenic activities. These pollutants seriously threaten coastal and marine ecosystems and their inhabitants, resulting in structural and functional ecosystem changes, eutrophication, red-tide, increased fish and benthos mortality, decreased fishery yields, and greater economic loss (Gao et al., 2014). Bohai Bay is one of most important semi-enclosed bays in northern China and is located in the western Bohai Sea. Bohai Bay is surrounded by large cities, including Beijing (the capital city of China) and Tianjin. Tianjin is one of four municipalities surrounding the bay and is an important commercial and industrial center in China with an area of approximately 11,200 km2 and a population of 11 million. Approximately one billion tons of wastewater is discharged from Beijing, Tianjin, and Hebei province into Bohai Bay every year (Duan et al., 2010). Consequently, large
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quantities of contaminants have been discharged into the bay that can severely threaten the ecosystem. Nitrogen, phosphorus, petroleum hydrocarbons, and heavy metals are considered the four most common pollutants in Bohai Bay (Li et al., 2010). Recently, several publications have recorded the presence of these contaminants in seawater from Bohai Bay. For example, Peng et al. (2009) reported variations in the nitrogen and phosphorus concentrations in the seawater from 1996 to 2006. Dai et al. (2009) reported the decennary (1996–2005) variations of dissolved heavy metals in the seawater of Bohai Bay. In addition, Li et al. (2010) reported temporal and spatial trends in the total petroleum hydrocarbon contents in seawater from Bohai Bay between 1996 and 2005. These studies indicated long-term variations of the four main contaminants in the seawater of Bohai Bay before 2006. However, no information is available regarding the pollutant concentrations after 2006. Many important events have occurred in this region since 2006. For example, the Summer Olympic Games were held in Beijing in 2008. To increase the air quality in this region, strict environmental protection policies were put into practice in Beijing, Tianjin, and Hebei Province. These policies potentially improved the seawater quality in the bay. Meanwhile, the Tianjin Binhai New District (TBND), a pilot area undergoing a special national integrated development plan in China that has drawn concern from the rest of the world, was build in 2006 (Qin et al., 2010). Many industries, including chemical, electronic, and manufacturing industries, have been built along the bay. These industries have potentially increased
http://dx.doi.org/10.1016/j.marpolbul.2015.03.032 0025-326X/Ó 2015 Published by Elsevier Ltd.
Please cite this article in press as: Peng, S. The nutrient, total petroleum hydrocarbon and heavy metal contents in the seawater of Bohai Bay, China: Temporal–spatial variations, sources, pollution statuses, and ecological risks. Mar. Pollut. Bull. (2015), http://dx.doi.org/10.1016/j.marpolbul.2015.03.032
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the discharge of wastewater into the bay. Additionally, ports and marine transportation have flourished in the bay area in recent years, which has likely influenced the water quality of the bay. However, little information is available regarding the concentrations of these four pollutants in the seawater in Bohai Bay. In this study, the nitrogen, phosphorus, total petroleum hydrocarbon, and heavy metal (As, Cu, Zn, Pb, Cd and Hg) concentrations in Bohai Bay seawater were collected from 2007 to 2012. The main objectives of this study were to (1) investigate the spatial and temporal variations of the pollutants in the seawater in Bohai Bay, (2) discriminate between the possible sources of pollution using multivariate analysis techniques, and (3) assess the status of the pollutants and determine the resulting ecological risk. Fifteen sampling sites were selected in Bohai Bay (Fig. 1). Station 1 is located on the coast of the Hangu District of Tianjin, near one of the largest chemistry plants in China. Station 3 is located in the Beitang Estuary, which serves as a pathway for many rivers, including the Yongdingxin River, Beiyun River, Chaobaixin River, Jiyun River, and Beijing Drainage River, that flow into Bohai Bay. Station 4 is located in the Dagu Drainage River estuary near Tianjin Port. Three sampling expeditions were carried out during three periods in one year (i.e., spring (May), summer (August) and winter (November)) for 6 years (2007–2012). Surface water (10–50 cm) was collected to determine the concentrations of nutrients (nitrogen and phosphorus), total petroleum hydrocarbons (TPH), and heavy metals (As, Cu, Zn, Pb, Cd and Hg) in the seawater. All samples were immediately filtered using 0.45 lm filters. The samples that were used to determine the nutrient contents were stored in a pre-cleaned plastic bottle and acidified with 98% H2SO4. In addition, the samples that were used for the heavy metal measurements were acidified to pH < 2 using suprapure HNO3. These samples were stored in sterilized glass jars and transported back to the laboratory on ice where they were immediately frozen until analysis.
The concentrations of ammonium (NH4–N), nitrate nitrogen (NO3–N), nitrite (NO2–N), and soluble reactive phosphorus (SRP) were determined following the standard methods of the APHA (1998). These measurements were completed within 24 h of sampling. The method detection limit for NH4–N, NO3–N, NO2–N, and SRP, were 4, 6, 3, and 1.4 lg/L, respectively. Because the nitrite and ammonium concentrations were negligible relative to the nitrate concentrations in this study, the three nitrogen sources were integrated into a single value of dissolved inorganic nitrogen (DIN). The total petroleum hydrocarbon (TPH) concentrations were determined using ultra-violet fluorescence spectroscopy according to the national standard method of China (GAQSIQ and SAC, 2008). The method detection limit for TPH was 6.2 lg/g. The heavy metal concentrations were determined using an Agilent 7500a ICP-MS (Agilent, USA). The quality control and assurance system in this study included reagent blanks, replicate samples, and certified international reference materials. The standard deviations of triplicate measurements were less than 5.0%. The limits of detection were 0.005 lg/L for Hg and Pb; 0.01 lg/L for As, Cd, and Cu; and 0.02 lg/L for Zn. The recoveries of the metals varied from 83% to 114%. The pollutions statuses of the different pollutants were assessed by comparing the detected pollutant concentrations to the seawater quality standards of China (GB 3097-1997, China), which are shown in Table 1 (SEPA, 1998). Different ecological risks result from different contaminants. For nitrogen and phosphorus, the ecological risks include the possibility of eutrophication in aquatic systems. Eutrophication has become a significant worldwide problem and catastrophically affects aquaculture and local economies (Richlen et al., 2010). Therefore, the ecological risks of nitrogen and phosphorus were assessed by using the trophic index (TRIX), which is calculated formulas follows (Vollenweider et al., 1998):
Fig. 1. Sampling sites in Bohai Bay.
Please cite this article in press as: Peng, S. The nutrient, total petroleum hydrocarbon and heavy metal contents in the seawater of Bohai Bay, China: Temporal–spatial variations, sources, pollution statuses, and ecological risks. Mar. Pollut. Bull. (2015), http://dx.doi.org/10.1016/j.marpolbul.2015.03.032
S. Peng / Marine Pollution Bulletin xxx (2015) xxx–xxx Table 1 Seawater quality standard of China for the selected pollutants (lg/L). Gradea
DIN
DIP
Hg
Cu
Pb
Cd
As
Zn
TPH
Grade-I Grade-II Grade-III
200 300 400
15 30 45
0.05 0.20 0.50
5.0 10 50.0
1.0 5.0 10
1.0 5.0 10
20 30 50
20 50 100
50 300 500
a The Grade-I refer to the fairly clean seawater, which can be used for mariculture, nature reserve, and endangered species reserve. The Grade-II indicates that seawater are clean, which can be used to marine aquiculture, human recreation leisure activities such as swimming. Grade-III indicates that seawater can be used to industry and tourism site.
TRIX ¼
LogðChl-a ½%DO DIN SRP þ 1:5Þ 1:2
where Chl-a, DIN and SRP are the concentrations of chlorophyll-a, dissolved inorganic nitrogen and soluble reactive phosphorus, respectively. In addition, %DO is the absolute value of the oxygen saturation deviation and is calculated as |100 %DO|. The four following trophic levels were defined: high with TRIX < 4, good with 4 < TRIX < 5, fair with 5 < TRIX < 6, and poor with TRIX > 6 (HerreraSilveira and Morales-Ojeda, 2009). The information of DO and Chl-a were presented in supplementary material (Figs. S1 and S2). TPH and heavy metals are threats to health. Thus, the ecological risks of TPH and heavy metals were assessed based on their adverse biological effects by using the reference table recommended by the National Oceanic and Atmospheric Administration (NOAA, 1999). The temporal and spatial differences of the different selected pollutants were performed by using a two-way analysis of variance (ANOVA). Principal component analysis (PCA) was used to determine the sources of the pollutants in the bay. Statistical significance was set at p < 0.05. The selected pollutant concentrations in the seawater from Bohai Bay collected from 2007 to 2012 are shown in Fig. 2. The average concentrations of the selected pollutants in the seawater from the 15 sites significantly varied from season to season (P < 0.01). In general, most of the selected pollutants decreased as follows: summer > winter > spring, with the summer month having the highest concentrations of all but Hg, As and Zn (their highest concentrations were found in the winter). It is possible that summer is the wet season, which would result in greater pollutants inputs to the bay by rivers (Zhou et al., 2014). In the present study, the concentrations of DIN, DIP, TPH, Hg, Cu, Pb, Cd, As, and Zn were in the range of 246–1417, 3.20– 36.61, 8.47–76, 0.003–0.36, 0.16–7.17, 0.17–9.55, 0.02–0.68, 0.25–4.02, and 17.3–90 lg/L, respectively. The concentrations in the present study were all lower that in the previous studies (e.g. Dai et al., 2009; Peng et al., 2009; Li et al., 2010). For example, the concentrations of DIN, DIP, and TPH were 103–2432, 0.9–120, and 8.47–76 lg/L, respectively, during 1996–2006 (Peng et al., 2009; Li et al., 2010). The maximum concentrations of Cu, Zn, Pb, Hg, and Cd were 16.3, 422, 40.4, 0.23, 0.89 lg/L respectively, during 1996–2005 (Dai et al., 2009), which were also higher than those in the present study. These results indicate that the concentrations of the selected pollutants decreased since 1996. The nutrient (DIN and DIP), TPH, Pb, and Cd concentrations generally decreased from 2007 to 2009 or 2010 and increased after 2010 (Fig. 3). The decreasing concentrations were explained by the promulgation of environmental protection policies. The first policy that was implemented is The Plan of Cleaning Bohai Sea. This policy was promulgated in the Bohai rim area by the Central Government of China in 2001 and aimed to halt industrial waste discharge to monitor environmental pollution and restore the damaged ecological system. One of our previous studies reported that the THP and heavy metal concentrations in sediment from
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Bohai Bay gradually decreased after this policy was put into place (Zhou et al., 2014). The second policy that was promulgated was the environmental protection program for the 2008 Summer Olympic Games in Beijing. In this case, the effluent was subjected to stricter regulations. To improve the environmental quality for the 2008 Summer Olympic Games, many protection programs were used to regulate the effluent in Beijing, Tianjin, and Hebei Province. For example, sewage treatment systems were installed and water pollution control regulations were enforced in Tianjin (Wu and Gao, 2010). These regulations significantly decreased waste air and water effluents. In addition, the pollution sources were controlled. Many industry plants that resulted in serious pollution were closed before 2008. In addition, the public and scientific awareness related to the environmental protection for the 2008 Summer Olympic Games helped to decrease the levels of pollution in the bay. Therefore, many of the selected pollutant concentrations decreased before 2009 or 2010. The concentrations of pollutant increased after 2009 was mainly attributed to the rapid development of the Tianjin Binhai New District (TBND). Within the last five years, the development of the chemical, electronics, port, and marine transportation industries has increased in the TBND. Such increases could produce more wastewater that is discharged into the bay. For example, the sewage discharge in 2011 was 628 million Mt, which was 1.1 times greater than it was in Tianjin in 2006 (Tianjin Environmental Protection Bureau, 2007, 2012). Furthermore, many industry plants that resulted in serious pollution were re-opened after the 2008 Summer Olympic Games. These enterprises discharge some of their wastewater into rivers, which was then transported into the bay with little to no treatment (Ren et al., 2010). Such discharge may increase the pollutant concentrations in the seawater from Bohai Bay. In addition, many pollution accidents have occurred in Bohai Bay in recent years (Zhou et al., 2014). Particularly an oil spill occurred that could cause a variety of environmental problems in the sea (White et al., 2012). For example, the oil spill of the Penglai 19-3 drilling platform in the Bohai Sea in June 2011 is one of the most serious oil spills that have occurred in China. This oil spill polluted 840 km2 of marine area and resulted in catastrophic economic losses for local aquaculture (Liu et al., 2015). Thus, this oil spill likely explains the occurrence of the highest TPH concentrations in 2011 (Fig. 3). The spatial variations of the selected pollutant concentrations generally gradually decreased from the shoreline to the offshore sites (Fig. 4). This finding is agree with those of previous studies regarding the spatial distributions of nutrients, THP, and heavy metals in seawater from Bohai Bay (Peng et al., 2009; Dai et al., 2010; Li et al., 2010). This finding occurred because terrestrial inputs are an important source of the pollutants in the bay, mainly riverine inputs and industrial discharge (Zhou et al., 2014). These two inputs have been considered as the most important sources of heavy metal concentrations for the seawater in the coastal areas of Bohai Bay (Wang and Wang, 2007). Thus, it is important to control riverine inputs and industrial discharge to improve the water quality of Bohai Bay. In this study, the highest pollutant concentrations were generally found at S3 or S4 (Fig. 4) because these two sampling sites are located in the estuary. In this study, the S3 sampling site is located in the Beitang estuary. This estuary received fresh and wastewater from the new Yongding, Chaobaixin, and Jiyun Rivers and the Tianjin Effluent Canal, before discharging into the Bohai Bay. The Beijing Drainage River, a major recipient of industrial effluents from Beijing, also transports a large amount of wastewater into Bohai Bay through the Beitang estuary (Ren et al., 2010). This result indicates that this estuary was subject to heavy anthropogenic influences from rapid economic development and urbanization in Tianjin and Beijing (Qin et al., 2010). Thus, it is not surprising that high concentrations of pollutants were found in this estuary. The S4 site is located in the Dagu Drainage estuary.
Please cite this article in press as: Peng, S. The nutrient, total petroleum hydrocarbon and heavy metal contents in the seawater of Bohai Bay, China: Temporal–spatial variations, sources, pollution statuses, and ecological risks. Mar. Pollut. Bull. (2015), http://dx.doi.org/10.1016/j.marpolbul.2015.03.032
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Fig. 3. Temporal variations of the selected pollutants in seawater.
Please cite this article in press as: Peng, S. The nutrient, total petroleum hydrocarbon and heavy metal contents in the seawater of Bohai Bay, China: Temporal–spatial variations, sources, pollution statuses, and ecological risks. Mar. Pollut. Bull. (2015), http://dx.doi.org/10.1016/j.marpolbul.2015.03.032
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S. Peng / Marine Pollution Bulletin xxx (2015) xxx–xxx
Fig. 4. Spatial variations of the pollutants concentration (lg/L).
This river is the main drainage river that contains effluents from Tianjin. Approximately 800,000 Mt/d of effluent were discharged into Bohai Bay from this estuary (Lü et al., 2007). Thus, this estuary may increase the pollutant concentrations at the S4 sampling site. Moreover, the S4 sampling site was located near Tianjin Port. This port was usually more heavily polluted than other water due to pollution from the ships (Zhou et al., 2014). However, some pollutants showed a high concentration of some heavy metals at other sampling sites (Fig. 4). For example, the highest Hg, As, and Zn concentrations were found at the S7, S10, and S2 sites, respectively. In this study, the S2 and S7 sites were located on the coast, while the S10 site was located offshore. This result indicates that other inputs may also exist for this bay. In this present study, a principal component analysis (PCA) was used to identify the sources of the selected pollutants in the seawater from Bohai Bay. The first three principal components (PC) explained 84.88% of the total variance in the original data (Table 2). This indicates that three main sources of pollutants existed in Bohai Bay. The first PC (PC I) was included strong positive values for DIN, DIP, THP, Cu, Pb, and Zn and indicated that they originated from the port. The nutrients and metals were of urban
Table 2 Principal component analysis (PCA) of the pollutants.
DIN DIP TPH Hg Cu Pb Cd As Zn Eigenvalue Explained variance (%) Total explained variance (%)
PC I
PC II
PC III
0.91 0.93 0.93 0.11 0.69 0.76 0.23 0.09 0.78 4.51 50.09 50.09
0.14 0.02 0.07 0.85 0.43 0.30 0.87 0.17 0.15 1.72 19.10 69.19
0.26 0.15 0.08 0.21 0.36 0.45 0.08 0.94 0.40 1.41 15.69 84.88
origin, which have been demonstrated in previous studies (e.g., Mendiguchía et al., 2007; Guéguen et al., 2012). The TPH mainly originated from the port due to shipping activities. In addition, Cd and Hg were in the second PC (PC II), and mainly originated from agriculture due to fertilizer use (Wu et al., 2010). Arsenic
Please cite this article in press as: Peng, S. The nutrient, total petroleum hydrocarbon and heavy metal contents in the seawater of Bohai Bay, China: Temporal–spatial variations, sources, pollution statuses, and ecological risks. Mar. Pollut. Bull. (2015), http://dx.doi.org/10.1016/j.marpolbul.2015.03.032
S. Peng / Marine Pollution Bulletin xxx (2015) xxx–xxx
presented a singular origin and was not related to any other pollutants (Table 2). The probable origin of As was atmospheric deposition, which resulted from the volatilization of As from coal during combustion (Chen et al., 2013). Thus, high concentrations of As were found during the winter (Fig. 2) because winter is the heating period in north China and coal combustion is the main source of heat. In this study, the pollution statuses of the selected pollutants were assessed by comparing their concentrations with the seawater quality standards of China (Table 1). Most of the selected pollutants met the highest seawater quality standards in China, except for the DIN and Zn (Fig. 2). This result indicates that the DIN and Zn are the main pollutants in Bohai Bay. Furthermore, some of the pollutants were greater than Grade-II in some years. For example, 66.67% of the samples had Pb concentrations that exceeded Grade-III. The DIP, THP, Hg, Cu and Hg concentrations in some years and at some sampling stations were above the Grade-III values. As shown in Fig. 5, the percentage of the selected Grade-I pollutants (Cd and DIP are exceptions) increased between 2007 and 2012, which indicated that the pollution status was aggravated in recent years in Bohai Bay. The eutrophication risk of the nutrients ranged form good to fair in Bohai Bay during the study periods (Fig. 6). High or poor levels were not observed in Bohai Bay for any year, indicating that the eutrophication risk was relatively low. However, the TRIX value decreased from 2001 to 2009 and increased after 2009. In addition, the status of 2011 and 2012 was fair, suggesting a potential eutrophication risk in Bohai Bay in recent years (Fig. 6). However, no ecological risks resulted from the other pollutants
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except, of for Cu in 2011 and 2012 (Table 3). Furthermore, the DIN concentrations exceeded the Grade-III seawater quality standards in China in all years (Fig. 2). These finding demonstrated that DIN has been the main pollutant in the seawater of Bohai Bay, and agrees with our earlier study from 1996 to 2006 (Peng et al., 2009). Due to nitrogen is a key element for phytoplankton (Seeyave et al., 2013; Treibergs et al., 2014). It is also the most important factor that can induce eutrophication in water system (Beversdorf et al., 2013; Loza et al., 2014). Due to the high concentrations of DIN in seawater, phytoplankton systems have dramatically changed in recent decade in Bohai Bay (Peng et al., 2012). Specifically, the primary production decreased while eutrophication became more severe (Tang et al., 2003). Although many environmental
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0
2007 2008 2009 2010 2011 2012
2007 2008 2009 2010 2011 2012
2007 2008 2009 2010 2011 2012
Cd
As
Zn
Grade-III
Grade-II
Grade-I
Fig. 5. The variations of the pollution status.
Please cite this article in press as: Peng, S. The nutrient, total petroleum hydrocarbon and heavy metal contents in the seawater of Bohai Bay, China: Temporal–spatial variations, sources, pollution statuses, and ecological risks. Mar. Pollut. Bull. (2015), http://dx.doi.org/10.1016/j.marpolbul.2015.03.032
S. Peng / Marine Pollution Bulletin xxx (2015) xxx–xxx Table 3 The ecological risks of THP and heavy metals.
CCC CMC 2007 2008 2009 2010 2011 2012
TPH
Hg
Cu
Pb
Cd
As
Zn
300
2.1 0.94 N N N N N N
4.8 3.1 N N N N CMC CCC
217 8.1 N N N N N N
43 9.3 N N N N N N
69 36 N N N N N N
95 81 N N N N N N
N N N N N N
CMC (Criteria Maximum Concentration) and CCC (Criteria Continuous Concentration) indicate that the acute and chronic toxicity, respectively (NOAA, 1999). N indicate that no risk.
protection policies have been promulgated since 2000, eutrophication risks have increases in recent years (Fig. 6). This increase is attributed to the greater discharge of wastewater discharge into Bohai Bay, although most of the wastewater was treated and met the China effluent criteria. Therefore, to decrease the eutrophication risks in the Bohai Bay, it is important to control the total emissions. The ecological risks of the THP and heavy metals were assessed based on their adverse biological effects by using the reference table recommended by the National Oceanic and Atmospheric Administration (NOAA). The results indicated that only Cu met the CMC and CCC criteria of the NOAA, which occurred in 2011 and 2012, respectively (Table 3). Thus, the ecological risks of THP and heavy metals in seawater from Bohai Bay were relatively low. Acknowledgments This work was supported by the National Nonprofit Institute Basic Research Fund of China (TKS150217), National Natural Science Foundation of China (21307045), International S&T Cooperation Program of China (2015DFA90250), and National Special Fund for Basic Science and Technology of China (2012FY112500). Appendix A. Supplementary material Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.marpolbul.2015. 03.032. References APHA, 1998. Standard Methods for the Examination of Water and Wastewater, 20th ed. APHA-AWWA-WPCF, Washington DC. Beversdorf, L.J., Miller, T.R., McMahon, K.D., 2013. The role of nitrogen fixation in cyanobacterial bloom toxicity in a temperate, eutrophic lake. PloS One 8, e56103. Chen, T., Yu, K., 2011. P/Ca in coral skeleton as a geochemical proxy for seawater phosphorus variation in Daya Bay, northern South China Sea. Mar. Pollut. Bull. 62, 2114–2121. Chen, J., Liu, G., Kang, Y., Wu, B., Sun, R., Zhou, D., Wu, D., 2013. Atmospheric emissions of F, As, Se, Hg, and Sb from coal-fired power and heat generation in China. Chemosphere 90, 1925–1932. Dai, M., Peng, S., Xu, J., Liu, C., Jin, X., Zhan, S., 2009. Decennary variations of dissolved heavy metals in seawater of Bohai Bay, North China. Bull. Environ. Contam. Toxicol. 83, 907–912. Duan, L., Song, J., Li, X., Yuan, H., Xu, S., 2010. Distribution of selenium and its relationship to the eco-environment in Bohai Bay seawater. Mar. Chem. 121, 87–99. Gao, X., Zhou, F., Chen, C.T.A., 2014. Pollution status of the Bohai Sea: an overview of the environmental quality assessment related trace metals. Environ. Int. 62, 12– 30. GAQSIQ (General Administration of Quality Supervision, Inspection and Quarantine of the People’s Republic of China), SAC (Standardization Administration of the People’s Republic of China), 2008. The Specification for Marine Monitoring—Part 4: Seawater Analysis.
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Please cite this article in press as: Peng, S. The nutrient, total petroleum hydrocarbon and heavy metal contents in the seawater of Bohai Bay, China: Temporal–spatial variations, sources, pollution statuses, and ecological risks. Mar. Pollut. Bull. (2015), http://dx.doi.org/10.1016/j.marpolbul.2015.03.032