MPB-07420; No of Pages 8 Marine Pollution Bulletin xxx (2015) xxx–xxx

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Trace metals in the surface sediments of the intertidal Jiaozhou Bay, China: Sources and contamination assessment Fangjian Xu a,⁎, Longwei Qiu a, Yingchang Cao a, Jingli Huang b, Zhaoqing Liu a, Xu Tian a, Anchun Li c, Xuebo Yin c a b c

School of Geosciences, China University of Petroleum, Qingdao 266580, China CNOOC Nanhai East Petroleum Bureau, Shenzhen 518067, China Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China

a r t i c l e

i n f o

Article history: Received 30 October 2015 Received in revised form 12 January 2016 Accepted 14 January 2016 Available online xxxx Keywords: Trace metals Anthropogenic activity Contamination Sediment Jiaozhou Bay

a b s t r a c t The major (Al) and trace metal (Cu, Pb, Zn, Cr, Cd, and As) concentrations in 29 surface sediment samples from the intertidal Jiaozhou Bay (JZB) are evaluated to assess the contamination level. The results show that the overall sediment quality in the area has been obviously impacted by trace metal contamination. The geoaccumulation index and the enrichment factor values indicate that no Cr or Cu contamination has occurred on the whole, only a few stations have been polluted by As, and some areas have been polluted by Cd, Pb, and Zn. Principal component analysis suggests that the Cu, Pb, Zn, and Cd are derived from anthropogenic inputs and that Cr, As, Cu, and Zn are influenced by natural weathering processes. Cu and Zn may originate from both natural and anthropogenic sources. The contamination in the northeastern JZB is higher than that in other areas of the bay. © 2015 Elsevier Ltd. All rights reserved.

Intertidal areas are complex and dynamic aquatic environments where the physical, chemical, and biological interactions between continents and marine systems have a profound influence on the transport and fate of trace metals (Spencer, 2002; Zhang and Gao, 2015). Intertidal sediments are therefore identified as one of the major reservoirs of trace metals from both natural and anthropogenic sources, such as industrial processes, including untreated wastewater, municipal sewage effluents, and surface run-off (Wang et al., 2007; Liu et al., 2012). These formations are important areas in coastal environments, but little attention has been paid to their ecological relevance. Trace metals are resistant to biodegradation and have the potential to bioaccumulate and to be biomagnified. These metals could be converted into more toxic organic complexes, which would not only pose a risk to aquatic organisms but also have long-term implications for human health and even damage the local ecosystem (Dou et al., 2013; Wang et al., 2015; Xu et al., 2015a). Therefore, spatial surveys of many trace metal concentrations in intertidal sediments are useful to assess the contamination between continents and marine environments and to provide basic information for the judgment of environmental health risks. The Jiaozhou Bay (JZB), which has an area of 340 km2 and an average depth of 7 m (Gao et al., 2014), is a typical semi-enclosed coastal embayment that is located within the territory of Qingdao City on the eastern coast of China (35°58′–36°18′N, 120°04′–120°23′E) and is connected to ⁎ Corresponding author at: School of Geosciences, China University of Petroleum, Changjiang West Road 66#, Qingdao, 266580, Shandong, China. E-mail address: [email protected] (F. Xu).

the Yellow Sea through a 3-km-wide channel (Fig. 1). The average annual precipitation in the JZB area is 680.5 mm, which primarily occurs from April to September and accounts for 92% of the annual precipitation (Yang et al., 2013). During the winter, the average precipitation is 34 mm, with a minimum of 9.8 mm, which occurs in December (Yang et al., 2013). The average tidal range is 2.7 m, with a maximum of 6.9 m, which induces strong turbulent mixing in the local waters (Deng et al., 2010). The tidal current moves back and forth in the north–south direction; east–west mixing is minimized by the tidal patterns (Liu et al., 2005b). After the completion of the spatial planning strategy, ‘Developing around the Bay based on the Core City’, the Jiaozhou Bay Bridge, which stretches 42 km over the sea and is the longest sea bridge in the world (Fig. 1), was opened in July, 2011. The JZB is the home of Qingdao Port, which is one of the top 20 trading ports in the world. From 1949 to 2013, the population of Qingdao City increased from 4.0 × 106 to 9.0 × 106 (Qingdao Municipal Statistics Bureau, 2014). More than 10 small seasonal streams empty into the bay with varying water and sediment loads, including the Yanghe, Daguhe, Moshuihe, Baishahe, and Licunhe Rivers (Fig. 1). However, most of these rivers have become canals of industrial and domestic waste discharge with the growth of economic activity and the increased population in the region (Shi et al., 2011). The discharge of waste water in urban districts was 84.6 × 106 t yr−1 in 1980 (Shen, 2001), which has increased to 472 × 106 t yr− 1 in 2013 (Qingdao Municipal Statistics Bureau, 2014). Although the cultivation area has declined, crop yields have actually increased through the heavier use of chemical fertilizers, which increased from 1.9 × 103 t yr−1 to 291.2 × 103 t yr−1 between

http://dx.doi.org/10.1016/j.marpolbul.2016.01.019 0025-326X/© 2015 Elsevier Ltd. All rights reserved.

Please cite this article as: Xu, F., et al., Trace metals in the surface sediments of the intertidal Jiaozhou Bay, China: Sources and contamination assessment, Marine Pollution Bulletin (2015), http://dx.doi.org/10.1016/j.marpolbul.2016.01.019

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F. Xu et al. / Marine Pollution Bulletin xxx (2015) xxx–xxx

Fig. 1. Sampling sites of the intertidal surface sediments in the Jiaozhou Bay (a), Shandong Province (b), China (c).

1957 and 2013 (Qingdao Municipal Statistics Bureau, 2014). Additionally, land reclamation has reduced the wetland and tidal flat area and the water volume in the JZB (Gao et al., 2014). Furthermore, the bay's shallow depth and restricted water exchange with the Yellow Sea have made the area particularly vulnerable to impacts from contamination (Ye et al., 2011). Because Qingdao was selected to be the co-host of the 2008 Beijing Olympic Games, measurements were adopted to manage the JZB, such as the foundation of erosion control efforts and improvements in effluent treatment. However, previous studies have indicated that increased trace metals have been observed in the JZB in recent years (e.g., Dai et al., 2007; Wang et al., 2007). Furthermore, data were only available for river outlets and/or deep water areas (e.g., Dai et al., 2007; Wang et al., 2007; Deng et al., 2010; Ye et al., 2011), so information from intertidal areas was lacking, which would limit our understanding of the transport or fate of such contaminants and their potential adverse environmental impacts. This field study is designed to address the identified research gaps that would provide valuable information regarding the spatial distribution of the selected trace metals in the intertidal areas of the JZB. Our primary objectives are to (1) determine the concentrations of trace metals, including Cu, Pb, Zn, Cr, Cd, and As, in the surface sediments of the JZB's intertidal zone; (2) assess the contamination status and potential ecological risk of these trace metals by using the Sediment Quality Guidelines (SQGs) and the geoaccumulation index (Igeo), respectively; and (3) distinguish the possible sources of trace metals by using enrichment factors (EFs) and principal component analysis (PCA). Surface (top 2 cm) sediment samples were collected from 29 sites (Fig. 1) during low tide in the intertidal areas in August, 2015. During sample collection, a hand-held global positioning system (GPS) was used to locate the sites. Plastic material was utilized to avoid metal pollution in the samples. After sampling, the sediment samples were sealed in clean polyethylene bags, transported back to the laboratory within a few hours and kept frozen until further analysis. The sediment samples were then oven-dried at 60 °C, and large calcareous debris and rock and plant fragments were removed. All the samples that were used for the grain-size analysis were pretreated with excess 30% H2O2 and 1 mol L−1 HCl in a water bath at 60 °C

for 1 h to remove organic matter and calcium carbonate, respectively. The suspension was centrifuged (3500 rpm, 6 min) 3 times with distilled water, and the upper clear liquid was discarded. The samples were then dispersed and homogenized by using ultrasound before passing through a Bettersize-2002 laser particle analyzer at the China University of Petroleum. This facility can measure grains in the 1 to 2600 μm range, with a measurement repeatability error of b 3%. The textural classification of the sediment samples was based on the relative percentages of clay (b4 μm), silt (4–63 μm) and sand (63–2000 μm) according to the Udden–Wentworth grade scale (Wentworth, 1922). The samples that were used for the elemental analysis were pretreated with an excess of 1 mol L− 1 HCl in a water bath at 60 °C for 1 h to remove calcium carbonate. The suspension was centrifuged (3500 rpm, 6 min) 3 times with distilled water, and the upper clear liquid was discarded. The residues of the leached samples were heated to dryness at 60 °C and then ground into powders by using an agate mortar and pestle. These samples were then digested with an HF + HNO3 + HClO4 acid mixture in Teflon vessels. The major (Al) and trace element concentrations were determined by a Thermo Icap6300 ICP-AES and a Perkin-Elmer ELAN DRC II ICP-MS, respectively. The analytical accuracy was assessed by analyzing selected USGS and Chinese certified reference materials (BHVO-2, GBW07315 and GBW07316). The differences between the measured and certified values were generally less than 10%, indicating satisfactory recoveries (Table 1). The sediment types were identified according to the ternary diagram of Folk's classification (Folk et al., 1970) and are listed in Table 2. Seven samples (2, 3, 13, 26, 27, 28, and 29) were classified as Sand, with sand, silt and clay contents of 91.0–100% (average 97.1%), 0–6.7% (average 2.3%), and 0–2.3% (average 0.6%), respectively. Six samples (4, 5, 16, 19, 22, and 24) were classified as Silty sand, with sand, silt and clay contents of 50.5–75.2% (average 60.5%), 22.2–39.1% (average 31.5%), and 2.6–10.9% (average 8%), respectively. Six samples (1, 9, 14, 18, 20, and 25) were classified as Sandy silt, with sand, silt and clay contents of 10.2–47.7% (average 34.6%), 43.8–69.4% (average 54.0%), and 6.4– 20.4% (average 11.4%), respectively. The remaining ten samples were classified as Silt, with sand, silt and clay contents of 0–8.0% (average 2.8%), 67.0–78.3% (average 70.7%), and 20.0–32.4% (average 26.5%),

Please cite this article as: Xu, F., et al., Trace metals in the surface sediments of the intertidal Jiaozhou Bay, China: Sources and contamination assessment, Marine Pollution Bulletin (2015), http://dx.doi.org/10.1016/j.marpolbul.2016.01.019

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Table 1 Results from an analysis of certified reference materials (BHVO-2, GBW07315, and GBW07316). The concentrations are in mg kg−1. Element

Al Cu Pb Zn Cr Cd As

BHVO-2

GBW07315

GBW07316

Measured values

Certified values

Recovery (%)

Measured values

Certified values

Recovery (%)

Measured values

Certified values

Recovery (%)

13.8 143 2.07 123 331 0.219 0.463

13.5 ± 0.2 127 ± 7 NA 103 ± 6 NA NA NA

102 103 NA 119 NA NA NA

11.1 339 45.0 138 64.9 0.350 7.16

11.41 ± 0.22 357 ± 20 37 ± 4 137 ± 15 59 ± 6 0.250 7.1 ± 0.6

97 95 122 101 110 140 101

7.86 237 21.9 144 38.4 0.282 4.74

7.7 ± 0.3 231 ± 10 22 ± 5 142 ± 22 38 ± 2 0.3 4.6 ± 0.5

102 103 100 101 101 94 103

NA: not available.

and coastal tourism, and the tertiary criteria (MSQ-3) are for harbors and ocean exploration. When compared to GB 18668-2002 (Table 3), 13 of the 29 sampling sites met the MSQ-1 for Cu, while 14 and 2 sites exceeded the MSQ-2 and MSQ-3; 23 sites met the MSQ-1 for Pb, while 5 and 1 sites exceeded the MSQ-2 and MSQ-3, respectively. Twenty-three sites met the MSQ-1 for Zn, and 6 sites met the MSQ-2; 22 sites met the MSQ-1 for Cd, and 7 sites met the MSQ-2. All 29 sites met the MSQ-1 for As. In general, the concentrations of the six trace metals in this study suggest that the overall sediment quality in the intertidal JZB has clearly been impacted by trace metal contamination. The threshold effect level (TEL)/probable effect level (PEL) SQGs were also applied to assess the degree to which the sedimentassociated metals might adversely affect aquatic organisms (Long et al., 1995; MacDonald et al., 2000). The TELs are intended to represent chemical concentrations below which adverse biological effects rarely occur, and the PELs are intended to represent chemical concentrations above which adverse biological effects frequently occur (Long et al., 1995; MacDonald et al., 2000). When compared to the TEL-PEL SQGs, the percentages of samples with Cu, Pb, Zn, Cr, Cd, and As concentrations below the TEL were 24.1%, 27.6%, 79.3%, 31.0%, 86.2%, and 34.5%, respectively, and 69.0%, 69.0%, 13.8%, 69.0%, 13.8%, and 65.5% of the samples fell in the range between the TEL and PEL, which indicates occasional adverse biological

respectively. The mean grain size of the sediments varied from 0.2 to 7.4 φ, with an average of 4.5 ± 2.2 φ. The elemental concentrations of the surface sediments in the study area were 5.6–17.0% for Al, 5.5–120.0 mg kg− 1 for Cu, 17.8– 325.4 mg kg−1 for Pb, 15.2–347.1 mg kg−1 for Zn, 7.1–141.4 mg kg−1 for Cr, 0–2.36 mg kg−1 for Cd, and 1.0–15.6 mg kg−1 for As (Table 2). The mean trace metal concentrations of the intertidal surface sediments from the JZB were much higher than those in other regions, such as the intertidal Bohai Bay (Gao and Li, 2012), the intertidal Laizhou Bay (Zhang and Gao, 2015), the coasts of northern Bohai and the Yellow Sea (Luo et al., 2010), and the intertidal Changjiang Estuary (Zhang et al., 2009) in China, which are listed in Table 3. In addition, the metal concentrations in the intertidal JZB were much lower than those in other larger urban-industrialized estuaries and coastal areas around the world (Table 3), such as the Pearl River Estuary in China (Yu et al., 2010), the Gironde Estuary in France (Larrose et al., 2010), and the Izmit Bay in Turkey (Pekey, 2006). Many Sediment Quality Guidelines (SQGs) have been established to evaluate the toxicity or risk of contamination to aquatic ecosystems. Marine Sediment Quality Standards (MSQ, GB 18668-2002) were promulgated by the China State Bureau of Quality and Technical Supervision (CSBTS, 2002). GB 18668-2002 contains three criteria for marine sediments, with the primary criteria (MSQ-1) for metal toxicity to wildlife and humans, the secondary criteria (MSQ-2) are for general industry

Table 2 Sediment type, clay, silt and sand contents (%), Al (%) and trace metal concentrations (mg kg−1) in the intertidal surface sediments in the Jiaozhou Bay. Sampling site

Sediment type

Clay

Silt

Sand

Al

Cu

Pb

Zn

Cr

Cd

As

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29

Sandy silt Sand Sand Silty sand Silty sand Silt Silt Silt Sandy silt Silt Silt Silt Sand Sandy silt Silt Silty sand Silt Sandy silt Silty sand Sandy silt Silt Silty sand Silt Silty sand Sandy silt Sand Sand Sand Sand

9.2 0.0 2.0 2.6 7.1 29.7 27.2 31.9 6.4 25.0 32.4 20.0 2.3 7.5 29.2 10.9 26.0 16.1 10.4 20.4 21.5 9.9 21.7 7.2 8.5 0.0 0.0 0.0 0.0

44.7 0.4 6.4 22.2 28.2 67.0 71.0 67.4 61.2 72.5 67.6 71.9 6.7 49.8 70.6 31.4 69.7 55.5 39.1 69.4 71.3 31.4 78.3 36.6 43.8 0.4 0.0 0.0 1.5

46.1 99.7 91.6 75.2 64.7 3.3 1.8 0.7 32.3 2.5 0.0 8.0 91.0 42.7 0.2 57.7 4.3 28.4 50.5 10.2 7.2 58.8 0.0 56.3 47.7 99.6 100.0 100.0 98.5

14.5 8.6 9.7 10.0 11.6 14.5 15.3 14.9 9.5 14.1 17.0 12.3 11.2 11.8 5.6 10.8 12.1 12.6 11.9 13.0 13.9 12.1 14.4 12.0 15.6 10.6 11.4 11.9 11.2

110.6 5.5 10.4 15.2 20.6 45.6 41.7 40.8 19.8 36.7 57.9 34.6 18.4 31.8 37.1 38.6 28.6 37.9 46.4 88.7 120.0 40.9 72.5 11.2 39.1 19.9 36.6 8.1 9.4

105.8 17.8 22.3 20.4 32.0 39.0 39.6 36.6 18.4 33.0 43.7 31.2 28.2 31.3 38.6 105.4 31.4 33.3 46.2 84.1 325.4 46.7 57.8 45.6 107.1 23.5 110.5 20.3 24.5

193.1 15.2 32.1 54.8 66.4 116.1 121.5 102.4 37.0 92.9 122.1 81.4 60.9 74.9 98.4 117.7 83.3 94.7 106.6 181.8 298.3 102.7 347.1 48.1 203.4 50.9 155.9 23.9 31.7

118.0 9.9 24.1 56.3 78.1 89.3 101.0 94.2 62.1 88.6 108.1 72.7 67.6 64.3 100.5 41.7 77.0 81.0 102.1 141.4 141.4 66.5 104.1 33.8 39.1 17.2 23.9 7.1 16.7

0.64 0.04 0.17 0.23 0.15 0.24 0.30 0.21 0.14 0.20 0.18 0.18 0.19 0.24 0.21 0.65 0.16 0.23 0.25 0.78 2.36 0.56 1.88 0.12 1.11 0.14 0.39 0.06 0.07

10.4 2.2 5.3 2.9 9.3 14.5 15.5 14.7 5.5 13.3 13.9 9.2 4.9 9.2 15.6 15.3 12.7 11.1 8.9 12.4 10.8 10.0 13.2 6.6 2.6 3.3 5.6 1.0 8.0

Please cite this article as: Xu, F., et al., Trace metals in the surface sediments of the intertidal Jiaozhou Bay, China: Sources and contamination assessment, Marine Pollution Bulletin (2015), http://dx.doi.org/10.1016/j.marpolbul.2016.01.019

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F. Xu et al. / Marine Pollution Bulletin xxx (2015) xxx–xxx

Table 3 A summary of the trace metal contents in the surface sediments of the intertidal Jiaozhou Bay. The average upper crust values in East China and the related values that are reported for surface sediments from other urban-industrialized estuaries and coastal areas are also shown for comparison. The concentration unit is mg kg−1 dry weight for all the elements. Location Intertidal Jiaozhou Bay, China Intertidal Bohai Bay, China Intertidal Laizhou Bay, China Coasts of the northern Bohai and Yellow Seas, China Intertidal Changjiang Estuary, China Pearl River Estuary Gironde Estuary, France Izmit Bay, Turkey Background value of Jiaozhou Bay sediments Average crust of East China MSQ-1a MSQ-2a MSQ-3a

Range Mean Range Mean Range Mean Range Mean Range Mean Range Mean Range Mean Range Mean Mean Mean

Cu

Pb

Zn

Cr

Cd

As

References

5.5–120.0 38.8 7.9–46.7 24.0 7.57–21.29 10.99 0.53–35 13 6.9–49.7 30.7 18.9–87.2 45.7 0.493–40.1 24.5 60.6–139 86.3 31.1 32 35 100 200

17.8–325.4 55.2 18.8–39.1 25.6 9.65–17.65 13.37 9.5–49 25 18.3–44.1 27.3 40.9–92.4 57.9 4.97–83.8 46.8 23.8–178 72.2 19.83 18 60 130 250

15.2–347.1 107.4 34.0–123 73.0 38.22–73.81 50.63 9.8–170 60 47.6–154 94.3 100–289 177 3.95–323 168 500–1190 716 44.93 70 150 350 600

7.1–141.4 69.9 36.7–110 68.6 25.85–42.75 32.69 4.2–94 47 36.9–173 78.9 74.1–123 106 1.34–140 78.4 57.9–116.1 79.6 65.3 80 80 150 270

0–2.36 0.42 0.05–0.19 0.12 0.11–0.28 0.19 0.05–0.83 0.15 0.12–0.75 0.26 NA NA 0.011–2.09 0.48 3.3–8.9 6.1 0.1 0.079 0.5 1.5 5.0

1.0–15.6 9.2 NA NA 4.65–9.65 7.1 5.6–13 8.5 NA NA NA NA 3.06–37.4 18.7 20.0–26.8 22.1 6.79 4.4 20 65 93

This study Gao and Li (2012) Zhang and Gao (2015) Luo et al. (2010) Zhang et al. (2009) Yu et al. (2010) Larrose et al. (2010) Pekey (2006) Liu et al. (2010) Gao et al. (1998) CSBTS (2002) CSBTS (2002) CSBTS (2002)

NA: not available. a The MSQ-1, MSQ-2, and MSQ-3 are the Marine Sediment Quality Standards (GB 18668-2002) that were issued by the China State Bureau of Quality and Technical Supervision (CSBTS, 2002).

effects on the aquatic ecosystems. For Cu, Pb, and Zn, 6.9%, 3.4%, and 6.9% of the sites slightly exceeded the PEL, which indicates potential harm to aquatic organisms (Table 4). The Igeo (Müller, 1979) is a classical assessment model for evaluating the trace metal contamination in sediments by comparing current concentrations with pre-industrial levels. The Igeo values were calculated with the following equation: Igeo = log2(Cn / 1.5Bn), where Cn is the concentration of a metal, and Bn is the geochemical background concentration of that metal. The factor 1.5 represents a background matrix correction factor that includes possible variations of the background values because of lithogenic effects (Müller, 1979). The elemental abundance of the pre-industrial sediments in the JZB (Liu et al., 2010) was adopted as the geochemical background concentration for the metals. The calculated Igeo values in the intertidal JZB sediments ranged from −3.09 to 1.36 for Cu, from −0.74 to 3.45 for Pb, from −2.15 to 2.36 for Zn, from − 3.78 to 0.53 for Cr, from − 1.83 to 3.98 for Cd, and from −3.41 to 0.61 for As (Fig. 2). Based on the Müller scale (Müller, 1981), the average Igeo values below zero that were observed for Cr (−0.81 ± 1.14) and Cu (−0.63 ± 1.10) suggest a lack of contamination by these metals in this region. However, the Igeo values for Cd (0.77 ± 1.34), Pb (0.49 ± 0.96), and Zn (0.33 ± 1.05) suggest moderate Cd, Pb, and Zn contamination in this area. Although the Igeo values for As (−0.40 ± 1.00) were less than zero, several sites had positive values, indicating minor to moderate metal contamination. The enrichment factors (EFs) of trace metals have been commonly used to assess human-made contamination. Al has been widely chosen

as the normalizing element to reduce the trace metal variability that is caused by the grain size and mineralogy of the sediments and to identify anomalous metal contributions (e.g., Zhang and Liu, 2002; Zhang and Shan, 2008; Hu et al., 2013). The EF is calculated with the following equation: EF = (Xsample / Alsample) / (Xbackground / Albackground), where Xsample, Xbackground, Alsample and Albackground represent the trace metal concentrations and aluminum contents of the samples and background references, respectively. In this study, the elemental abundance in the upper crust of East China (Gao et al., 1998) was used as the reference background. In general, EF values of 0.5–1.5 reflect regional rock compositions, whereas EF values that are greater than 1.5 indicate noncrustal contributions and/or non-natural weathering processes (e.g., anthropogenic influences) (Zhang and Liu, 2002; Zhang and Shan, 2008). The EFs of the intertidal surface sediments in the JZB are shown in Fig. 3. The EFs of these metals were ordered Cd N Pb N As N Zn N Cu N Cr. The average EFs of the Cu (1.3 ± 0.9) and Cr (1.0 ± 0.6) in the intertidal JZB were less than 1.5, which suggests that these metals are not a major concern. However, moderate Cu and Cr enrichment was also found in certain areas, with 7 sites enriched in Cu (1.5 to 3.7, mean of 2.6), and 3 sites enriched in Cr (1.7 to 3.1, mean of 2.2). The EF values of the Cd (5.6 ± 6.4), Pb (3.4 ± 3.3), As (2.4 ± 1.5), and Zn (1.7 ± 1.1) in the intertidal JZB, which exceed 1.5, indicate minor to moderately severe Cd, Pb, As, and Zn contamination in the study area

Table 4 Comparison of the trace metal concentrations (mg kg−1) in the study area with the TEL and PEL SQGs (MacDonald et al., 2000). Sediment Quality Guidelines

TEL PEL

Metal concentration (mg kg−1) Cu

Pb

Zn

Cr

18.7 108.2

30.2 112.2

124 271

52.3 160.4

Compared to TEL and PEL (% of the sample in each guideline) bTEL 24.1 27.6 79.3 ≥TEL b PEL 69.0 69.0 13.8 ≥PEL 6.9 3.4 6.9

31.0 69.0 0

Cd 0.68 4.2

86.2 13.8 0

As 7.2 41.6

34.5 65.5 0

Fig. 2. Geoaccumulation indexes (Igeo) of the trace metals in the intertidal surface sediments in the Jiaozhou Bay.

Please cite this article as: Xu, F., et al., Trace metals in the surface sediments of the intertidal Jiaozhou Bay, China: Sources and contamination assessment, Marine Pollution Bulletin (2015), http://dx.doi.org/10.1016/j.marpolbul.2016.01.019

F. Xu et al. / Marine Pollution Bulletin xxx (2015) xxx–xxx

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Fig. 3. Enrichment factors (EFs) of the trace metals in the intertidal surface sediments in the Jiaozhou Bay.

and suggest that the metals may primarily originate from anthropogenic sources. Compared to the Marine Sediment Quality Standards (GB 186682002), 22, 23, and 23 sites in the intertidal JZB met the MSQ-1 for Cd, Pb, and Zn, respectively. Compared to the TEL-PEL SQGs, only a few sites for Cu, Pb, and Zn slightly exceeded the PEL. However, the Igeo and EF values of Cd (0.77 ± 1.34 and 5.6 ± 6.4, respectively), Pb (0.49 ± 0.96 and 3.4 ± 3.3, respectively), and Zn (0.33 ± 1.05 and 1.7 ± 1.1, respectively) clearly show that elevated concentrations of Cd, Pb, and Zn occur in the region. Therefore, both Igeo and EF are more suitable tools for the assessment of trace metal contamination than the Marine Sediment Quality Standards (GB 18668-2002) and the TEL-PEL SQGs in the study region. Multivariate analysis techniques have been widely used to distinguish natural and anthropogenic contributions of elements based on variable levels of association (e.g., García et al., 2004; Hu et al., 2013). In our analysis, PCA was performed on the variables to establish possible relationships and input sources among the pollutant elements. The Kaiser–Meyer–Olkin (KMO) and Bartlett's results in this study were 0.667 and 176.48 (df = 21, p b 0.001), respectively, which indicates that PCA may be useful for dimensionality reduction. Two principal components with an eigenvalue N 1 (García et al., 2004; Hu et al., 2013) were determined, and together, they accounted for 80.3% of the total variance (Table 5; Fig. 4), which indicates that different sources or controlling factors are responsible for the trace metal distributions in the intertidal surface sediments of the JZB. In PC1 (45.6% of the total variance), Cu, Pb, Zn, and Cd have strong positive loadings. Both the Igeo and EF results suggest that these four metals are clearly influenced by anthropogenic inputs. Therefore, PC1 likely primarily represents anthropogenic sources. PC2 (34.7% of the total variance) has strong positive loadings for Cr and As and moderate positive loadings for Cu, Al, and Zn. Aluminum is a structural element of terrigenous aluminosilicates and is a primary lithogenic component,

Fig. 4. Principal component loading of metal variables in the intertidal surface sediments in the Jiaozhou Bay.

which implies that the four trace metals were predominantly affected by crustal materials or natural weathering processes. Therefore, PC2 likely primarily represents natural sources. Additionally, PC1 and PC2 both included Cu and Zn, which suggests that these elements may originate from both natural and anthropogenic sources. The regression of Al on Cd and Pb was performed. The scatter plots and the regression curves of Al on Cd and Pb are presented in Fig. 5. Al is weakly correlated with Cd and Pb (R for Cd = 0.35 and R for Pb = 0.27, respectively), which suggests that the anthropogenic influence on the concentrations of these metals in the intertidal JZB is apparent. Furthermore, several points in the scatter plots are obviously projected above the 95% confidence limit of the metal to Al regression lines, which suggests anomalous enrichment in these metals. Most of these sites are located in the northeastern JZB (Fig. 6).

Table 5 Total variance of the principle component analysis. Variables

Al Cu Pb Zn Cr Cd As Initial eigenvalue % of total variance % of cumulative variance

Rotated component matrix PC1

PC2

0.31 0.74 0.91 0.84 0.35 0.94 −0.01 3.19 45.6 45.6

0.57 0.59 0.09 0.43 0.85 0.17 0.91 2.43 34.7 80.3

Extraction method: principal component analysis. Rotation method: varimax with Kaiser normalization. The bold values indicate strong and moderate loadings.

Fig. 5. Cd:Al (a) and Pb:Al (b) scatter plots for the intertidal surface sediments in the Jiaozhou Bay. The solid lines represent the regression lines (n = 29), and the dashed lines define the 95% confidence limit. Sample sites that fall above the upper 95% confidence limit are considered anomalously enriched and are represented by red dots. Most of these sites are located in the northeastern Jiaozhou Bay. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

Please cite this article as: Xu, F., et al., Trace metals in the surface sediments of the intertidal Jiaozhou Bay, China: Sources and contamination assessment, Marine Pollution Bulletin (2015), http://dx.doi.org/10.1016/j.marpolbul.2016.01.019

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F. Xu et al. / Marine Pollution Bulletin xxx (2015) xxx–xxx

Please cite this article as: Xu, F., et al., Trace metals in the surface sediments of the intertidal Jiaozhou Bay, China: Sources and contamination assessment, Marine Pollution Bulletin (2015), http://dx.doi.org/10.1016/j.marpolbul.2016.01.019

F. Xu et al. / Marine Pollution Bulletin xxx (2015) xxx–xxx

Previous studies have shown that the Cd and Pb distributions were closely related to the intensive usage of phosphate fertilizers (Jones and Johnston, 1989; Zhang and Shan, 2008; Xia et al., 2011). In addition, Cd might come from the alloying, electroplating, and dyeing industries (Li et al., 2009; Xu et al., 2015b). Pb might come from industries, agricultural and fish farms, and dye and paper manufacturers that use herbicides, fungicides, and chemical fertilizers (Bastami et al., 2012). Pb was previously added to gasoline, and the use of gasoline-powered machines was another anthropogenic source of Pb (Wong et al., 2002; Zhang and Shan, 2008). Therefore, heavy Cd and Pb contamination is greatly associated with human activities, which leads to increased amounts of industrial, agricultural, and aquacultural input into the JZB. In this study, we paid more attention to Cd and Pb not only because the EFs of Cd (5.6 ± 6.4) and Pb (3.4 ± 3.3) in our study area were higher than those of the other trace metals but also because Cd and Pb have a similar origin (i.e., anthropogenic sources) based on the analysis in the former text. As shown in Fig. 6, the most apparent feature of the metal distribution is that the contamination in the northeastern JZB is generally higher than that in other areas of the bay. Liu et al. (2005a) found that the northeastern part of the JZB is experiencing severe eutrophication, which is consistent with our findings. This area is located just outside the Moshui River and Baisha River mouths and is embraced by the Jiaozhou Bay Bridge and the coastline. Previous studies also found that the total concentrations of trace metals, especially Cd and Pb in the eastern river sediments, were relatively high, such as in the Moshui River and Baisha River (Deng et al., 2010). These rivers pass through the industrial area of Qingdao, where a number of factories and companies are located. The Baisha River is a major freshwater source for Qingdao City, and its dams were constructed in the last century. For example, three dams are located upstream of the Baisha River, and they supply more than 5 × 107 m3 yr−1 of water to the city. A decline in water discharge in recent years has reduced the dilution of pollutants, which has potentially decreased the self-purification capacity of the rivers. Recently, the rapid transformation of the JZB has been strongly driven by government development and planning policies (Li et al., 2015). A large amount of reclamation occurred at the head of the bay (especially the northeastern part) several decades ago. The destruction of wetland areas could also strengthen the impact of pollutants (de Groot et al., 2012; Zhi and Ji, 2012). Furthermore, the heavy contamination in the northeastern JZB is most likely related to the construction of the Jiaozhou Bay Bridge (see Fig. 1). Model results showed that the Jiaozhou Bay Bridge had a relatively large impact on the bay's hydrodynamic environment, which was most obvious in the decreasing tidal flow and tidal flux (Li et al., 2014). Therefore, the cumulative and increasing land-based contamination (Deng et al., 2010) and the lost and/or reduced ecological function that is caused by the alteration of coasts and waters through reclamation and other management decisions (Shi et al., 2011; Gao et al., 2014; Li et al., 2014) are likely to be the primary causes of the detrimental environmental issues in the intertidal JZB. Consequently, conducting comprehensive and in-depth monitoring studies with regards to JZB management is urgently needed. When implementing the current government plan (Qingdao Municipal Government, 2013), each watershed region in the JZB was forced to cut the same proportion of their current annual discharge amount of pollutants without considering the differences in their capacities. The northeastern parts are fed by several rivers that carry wastewater from agricultural, industrial and domestic waste, as discussed above, and these rivers were the most seriously polluted ones in the JZB. However, this phenomenon does not occur in other watersheds or regions. Therefore, the Qingdao government must strictly control sources of contamination, eliminate the construction of land reclamation, and differentiate the reduction targets for pollutant discharge between regions.

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The concentration and spatial distribution of trace metals (Cu, Pb, Zn, Cr, Cd, and As) were analyzed in the surface sediments in the intertidal JZB in this study. The concentrations of the six trace metals in this study suggested that the overall sediment quality in the intertidal JZB has been clearly impacted by trace metal contamination. The Igeo and EF values of these trace metals indicated that no Cr and Cu contamination occurred in the study area on the whole, and only a few stations were polluted by As. Some areas were regionally polluted by Cd, Pb, and Zn (especially Cd and Pb), which indicates the potential to harm aquatic organisms. PCA results suggested that the Cu, Pb, Zn, and Cd were likely to be derived from anthropogenic inputs. Comparatively speaking, Cr, As, Cu, and Zn were influenced by natural weathering processes. The Cu and Zn may originate from both natural and anthropogenic sources. The contamination in the northeastern JZB is higher than that in other areas of the bay. The cumulative and increasing land-based contamination and lost and/or reduced ecological function that is caused by the alteration of the coasts and waters through reclamation and other management decisions appear to be the primary causes. This work presents the current state of the sediment quality in the intertidal JZB, and our results will be useful for marine environment managers to evaluate remediation plans for contamination sources. Greater attention should be paid to the anthropogenic sources of trace metals because of further industrialization and economic development in the study region. The government of Qingdao must strictly control the sources of contamination, eliminate the construction of land reclamation, and differentiate the reduction targets for pollutant discharge between regions. Acknowledgments We would like to thank the editor, Bruce J. Richardson, and the anonymous reviewers for their constructive reviews of the early version of this paper. Funding for this research was provided by the National Natural Science Foundation of China (41106040, 41430965), the Qingdao Science and Technology Development Plan Projects (13-1-4-197-jch), the National Science and Technology Major Project (2011ZX05009002, 2016ZX05047-003), and the Fundamental Research Fund for the Central Universities (12CX02003A, 14CX02099A, 14CX02183A). References Bastami, K.D., Bagheri, H., Haghparast, S., Soltani, F., Hamzehpoor, A., Bastami, M.D., 2012. Geochemical and geo-statistical assessment of selected heavy metals in the surface sediments of the Gorgan Bay, Iran. Mar. Pollut. Bull. 64 (12), 2877–2884. http://dx. doi.org/10.1016/j.marpolbul.2012.08.015. CSBTS, 2002. The People's Republic of China National Standards GB 18668-2002-Marine Sediment Quality. Standards Press, Beijing (in Chinese). Dai, J., Song, J., Li, X., Yuan, H., Li, N., Zheng, G., 2007. Environmental changes reflected by sedimentary geochemistry in recent hundred years of Jiaozhou Bay, North China. Environ. Pollut. 145 (3), 656–667. http://dx.doi.org/10.1016/j.envpol.2006.10.005. de Groot, R., Brander, L., van der Ploeg, S., Costanza, R., Bernard, F., Braat, L., Christie, M., Crossman, N., Ghermandi, A., Hein, L., Hussain, S., Kumar, P., McVittie, A., Portela, R., Rodriguez, L.C., ten Brink, P., van Beukering, P., 2012. Global estimates of the value of ecosystems and their services in monetary units. Ecosyst. Serv. 1 (1), 50–61. http://dx.doi.org/10.1016/j.ecoser.2012.07.005. Deng, B., Zhang, J., Zhang, G., Zhou, J., 2010. Enhanced anthropogenic heavy metal dispersal from tidal disturbance in the Jiaozhou Bay, North China. Environ. Monit. Assess. 161 (1–4), 349–358. http://dx.doi.org/10.1007/s10661-009-0751-x. Dou, Y., Li, J., Zhao, J., Hu, B., Yang, S., 2013. Distribution, enrichment and source of heavy metals in surface sediments of the eastern Beibu Bay, South China sea. Mar. Pollut. Bull. 67 (1–2), 137–145. http://dx.doi.org/10.1016/j.marpolbul.2012.11.022. Folk, R.L., Andrews, P.B., Lewis, D.W., 1970. Detrital sedimentary rock classification and nomenclature for use in New Zealand. J. Geol. Geophys. 13 (4), 937–968. http://dx. doi.org/10.1080/00288306.1970.10418211. Gao, X., Li, P., 2012. Concentration and fractionation of trace metals in surface sediments of intertidal Bohai Bay, China. Mar. Pollut. Bull. 64 (8), 1529–1536. http://dx.doi.org/ 10.1016/j.marpolbul.2012.04.026. Gao, S., Luo, T., Zhang, B., Zhang, H., Han, Y., Zhao, Z., Hu, Y., 1998. Chemical composition of the continental crust as revealed by studies in East China. Geochim. Cosmochim. Acta 62 (11), 1959–1975. http://dx.doi.org/10.1016/S0016-7037(98)00121-5.

Fig. 6. Distribution of enrichment factors (EFs) for the trace elements Cd (a) and Pb (b) in the intertidal surface sediments in the Jiaozhou Bay. The green shaded area indicates the heavy contamination in the northeastern Jiaozhou Bay. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

Please cite this article as: Xu, F., et al., Trace metals in the surface sediments of the intertidal Jiaozhou Bay, China: Sources and contamination assessment, Marine Pollution Bulletin (2015), http://dx.doi.org/10.1016/j.marpolbul.2016.01.019

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Please cite this article as: Xu, F., et al., Trace metals in the surface sediments of the intertidal Jiaozhou Bay, China: Sources and contamination assessment, Marine Pollution Bulletin (2015), http://dx.doi.org/10.1016/j.marpolbul.2016.01.019