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This study analyzed the variations of soil organic carbon (SOC), total nitrogen (TN), and total phosphorus (TP) with depth in coastal wetlands of Laizhou Bay, Bohai Sea. Generally, average contents of SOC and TN were higher at tidal flooding Guangrao wetland (GRA) than those at Changyi (CY) wetland where the tidal can rarely reached. Among the five profiles, higher variations of SOC and TN were observed in CYB1 and CYB2, where the TP contents showed lower variations. SOC showed a rapid decrease with depth in CYB1 and CYB2, whereas they tended to increase with depth in GRA1 and GRA2. Vertical distributions of TN were significantly correlated with SOC in profile GRA1, CYB1, and CYB2. However, no clear trend was found on the vertical variations of TP. Additionally, C, N, and P ecological stoichiometry in these two coastal wetlands had high complexities within wetland. The C/N ratios were generally higher, while the C/P ratios and the N/P ratios were comparatively low, indicating the coastal wetland biogeochemical processes were more limited by N and P, with the former may being the primary factor. Our results also indicated that both vegetation coverage and tidal flooding were important in the biogeochemical processes of these coastal wetlands. [ABSTRACT FROM AUTHOR]

Surface sediment samples were collected at 27 stations of Bohai Bay, North China. Sequential extractions were carried out in this study. REE were leached out from four labile fractions: Exchangeable (L1), bound to carbonates (L2), bound to Fe-Mn oxides (L3), bound to organic matter (L4), and the remainder was residual (R5). The total contents of REE fluctuate slightly in Bohai Bay, and are mainly concentrated in the middle region, showing relatively higher levels in the north than that in the south of Bohai Bay. Percentages of L1, L2, L3, L4, and R5 for REE suggest that the residual fraction accounts for the major component of REE, whereas Fe-Mn oxides also play important roles in combining labile REE. As the REE complex is not stabilized, the competition of complex could induce dissociation of the complex and redistribution of the REE in various environments. According to REE patterns and Y/Ho ratios of samples, REE are not anthropogenic or oceanic sources but riverine input, whereas suitable environment varieties can slightly affect the patterns and fractionations of REE. As powerful tracers for the variable of environment, higher anomaly of Eu and Ce in southern regions indicates a greater reduction in the condition of surface sediment in the south than that in the north of Bohai Bay. [ABSTRACT FROM AUTHOR]

Dissolved inorganic tin (DISn) and its spatial variation were examined in Bohai Bay seawaters to understand the DISn behavior and pollution in this area. DISn concentration gradually increased with the distance from the coast and showed a slight decrease with the increasing depth from surface water, suggesting the scavenged behavior of tin with an atmospheric input to surface water. Besides, the higher DISn values also were found near the Haihe Estuary inferring that the riverine input was a source of DISn. Based on the data in this study, a preliminary estimate of the tin budget via riverine input and atmospheric deposition has been established. According to our estimate, about 2 × 10 and 8.47 × 10 g/year of tin reach Bohai Bay via rivers and atmosphere. Environmental factors such as suspended particulate material, salinity, total organic matter, pH, nutrients, and phytoplankton had the important influences on DISn distribution. Among them, the negative correlation between DISn and phytoplankton at most stations might indicate the biological uptake of tin. [ABSTRACT FROM AUTHOR]

Abstract: Water samples collected from Bohai Bay were determined to describe the distributions of lead, mercury, and copper in this area, indicating that mean values of the three metals were 1.63μg/L, 4.85×10−2 μg/L, and 2.68μg/L, respectively. Only lead exceeded the first class limit of seawater quality standard in China. Then, antioxidant enzymes, lipid peroxidation, and metabolic enzymes were investigated in bivalves (Chlamys farreri), exposed to three metals at the environmental concentration levels obtained from our investigation. Significantly reduced SOD, CAT and GPx activities, in lead-exposed group were observed and resulted in obvious lipid peroxidation. In contrast, mercury and copper did not show such clear oxidative stresses. In consistent with the oxidative stress variations, exposed only to lead caused a great inhibition on EROD activity. Multi-biomarker responses in bivalve when exposed to lead at the environmentally relevant concentration in Bohai Bay suggested that lead may possess a potential risk in this area. [Copyright &y& Elsevier]

The Bohai Sea costal area is one of the most developed zones of China and the sewage water from populous and developed cities, including Beijing, Tianjin, Qinhuangdao and Dalian is discharged into the Bohai Sea. Additionally, its semi-enclosed characteristic restricts water exchange, which leads to high accumulation of pollutants in the environment. This overview presents the residues of 6 classes of Persistent Organic Pollutants (POPs), including PAHs, DDTs, HCHs, PCBs and PCDD/Fs, in the sediments and mollusks of the Bohai Sea through analyzing previous literatures. In the sediments, the highest PAH concentrations were detected in the vicinities of Qinhuangdao, while the northeast corner of the Bohai Bay possessed the highest levels of DDTs and PCBs. The investigations on HCHs and PCDD/Fs distributions on the whole sea scale have not been reported. In mollusks, PAH concentrations were in the same order of magnitude in the whole Bohai Sea, so were DDTs, HCHs and PCBs, while the outlier maximum values of PCDDs and PCDFs occurred in Yingkou. In general, the POPs residues in mollusks collected from Shandong Province were higher than the other areas. The compositions of DDTs, HCHs and PCBs in sediments indicated their recent usage. By comparing POP concentrations in sediments with the recommended criterions, it was shown that some individual PAH compounds occasionally associated with adverse biological effects in the vicinities of the Liaodong Bay and Qinhuangdao, and the Liaohe River Estuary were heavily contaminated with DDTs, but PCBs were all below the thresholds. In order to reveal the transference and transformation of POPs in the environment, further studies concerning with their behavior, fate and bioaccumulation in the different trophic levels should be programmed. Moreover, laws and regulations should be enforced to ban the illegal usage of POPs-containing pesticides to guarantee health of the environment and human. [Copyright &y& Elsevier]

Abstract: The Tl concentrations and chemical speciation were determined in the surface sediments of Bohai Bay to evaluate its biogeochemical characteristics. The total Tl concentrations were in the range of 0.506–0.770 μg/g and correlated significantly with clay and total organic carbon (TOC) contents, suggesting that the grain size and TOC were major factors controlling Tl distribution. The sequential extraction performed to indicate Tl speciation and availability in Bohai Bay sediments suggested that Tl occurred mainly in the residual fraction and Tl came mainly from natural input. In the non-residual fractions, Fe–Mn oxide and organic matter fractions accounted for the main portions, suggesting that the labile Tl adsorption was dominated by Fe–Mn oxides and organic matter. In addition, according to our estimate, about 2.7 t/yr and 0.16 t/yr of Tl reached Bohai Bay via rivers and atmosphere, respectively. [Copyright &y& Elsevier]

Abstract: We determined the selenite (Se(IV)) and selenate (Se(VI)) concentrations in the surface and bottom waters of Bohai Bay to understand the behavior of selenium in this area. The average concentrations of selenite and selenate were 0.72nM and 0.36nM, respectively. The surface concentration of selenite and selenate decreased from the western bay to the bay mouth, with the highest value near the Haihe Estuary. The bottom concentration of selenite and selenate displayed a similar distribution as the surface concentration. The selenium distribution was mainly controlled by environmental factors, riverine discharges and biological activities. Based on the data in this study, a preliminary estimate of the selenium budget via riverine input has been established. According to our estimate, about 7.18×107 mmol/yr of selenium reaches the Bohai Bay via rivers. Selenium showed significant positive correlations with dissolved inorganic nitrogen (DIN), phosphate and silicates, reflecting its strong nutrient-type behavior. The selenium concentration also correlated well with the chlorophyll a concentration and phytoplankton biomass, possibly implying that selenium plays a key role in regulating the phytoplankton productivity and that phytoplankton dynamics also affect the selenium inventory in Bohai Bay. Furthermore, the selenium concentration in each site was lower than the “no-effect” value of selenium and seemed to be required for the normal growth and development of phytoplankton, but it may have adverse effects for higher trophic levels due to the bioaccumulation of selenium. [Copyright &y& Elsevier]