[Variation characteristics and potential ecological risk assessment of heavy metals in the surface sediments of Bohai Bay].

The geochemical characteristics of eight heavy metals (Cd, Co, Cr, Cu, Ni, Pb, V and Zn) in two sediment cores from Bohai Bay, North China, were studied. Sediment samples were collected from 27 stations in spring 2008. A sequential extractions, procedure was used to gain their fractionation information. Five operationally defined fractions were obtained by this protocol, i. e. exchangeable (L1), bound to carbonates (L2), bound to Fe/Mn-oxides (L3), bound to organic matter and sulphides (LA), and residual fraction (R5). Combined with ecological risk in total contents and fraction, a series of results and viewpoints with regard to distribution characteristics of heavy metals were presented, as well as ecological risk and controlling factors. Heavy metals in sediments were mainly concentrated in the middle region with fine particle. The distributions of V, Ni, Cu, Pb, Co, Cd were mainly controlled by nature source, while Zn and Cr can be easily impacted by environment or human input. Coming from atmospheric deposition and riverine, Pb was different with other heavy metals. Sequential extractions suggested that V, Zn, Cr were mainly composed with residual fractions, while Co, Ni, Cu were dominated by labile fractions. The percentage of labile Co increased from inner to outside, labile Ni reached maximum at station A3, labile Cu and Pb concentrated in the middle of Bohai Bay, while Cu achieved maximum at station D1 near Yellow River. Labile heavy metals were enriched near the estuary of Haihe River. The order of enrichment factors (EF) of heavy metals was Pb > Cd > Zn > Cr > V > Co > Cu > Ni. And the EF of Pb, Cd and Zn were above 1, suggesting that they could be polluted by exterior input, while the sediment quality was relatively good in general. The ratios of labile and residual fraction showed that V and Cr were clean, Zn was partly in slightly polluted, Co was mostly slightly polluted, Cu was from clean to moderately polluted, Ni was polluted from slightly to heavy, and Pb was polluted heaviest in all heavy metal. In conclusion, V, Cr and Co were clean, Cu and Zn may be polluted, while Pb was polluted heaviest.

Environmental geochemistry reflected by rare earth elements in Bohai Bay (North China) core sediments.

In Bohai Bay sediment, two cores were collected to estimate the source of sediments, and assess the environmental changes. Sequential extractions were carried out in this study. Rare earth elements (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 percentages of REE in different fractions follow the order: R5 > L3 > L2 > L4 > L1. With heavy REE depletion and no pronounced REE fractionation, NASC-normalized REE patterns of Bohai Bay sediments are quite consistent with that of Haihe River sediment, which is the key river of Bohai Bay. Y/Ho ratios of total contents are all much lower than the average value of continental crust, while Y/Ho ratios of L2 are higher than those of other fractions. Based on the patterns of REE and Y/Ho ratios of samples, sediments of Bohai Bay mainly come from terrigenous matters, which are mainly brought by Haihe River. And REE combined with carbonates may be partly inherited from anthropogenic matter. Moreover, environmental changes exert significant influences on the patterns and fractionations of REE, and they can be deduced from the characteristics of REE. Our results on the patterns and burial fluxes of REE reflect two environmental changes: Bohai Bay has been shifting towards more reducing conditions in the last one hundred years, and there was a large flood in 1939.

[Effects of excessive inorganic nitrogen on inorganic carbon system in seawater simulated experiments].

The influence of excessive inorganic nitrogen (NO3-, NH4+, NO2-) on the pH, inorganic carbon system and air-sea CO2 flux was studied in laboratory seawater simulation experiments. The result indicates that the excessive inorganic nitrogen significantly has an important influence on the inorganic carbon system in all conditions. At the NO3- addition groups, HCO3- and p (CO2) increase while pH and CO3(2-) decrease when the concentration of NO3- < or = 37.60 micromol x L(-1). But high concentrations > or = 188 micromol x L(-1) is just the reverse. The seawater changes from carbon source to carbon sink of atmospheric CO2 with NO3- addition increased. At the NH4+ addition groups, HCO3- and p (CO2) decrease while pH and CO3(2-) increase when the concentration of NH4+ < or = 25.20 micromol x L(-1). However, when the concentration of NH4+ > or = 126 micromol x L(-1), the concentrations of HCO3- and p (CO2) increase with NH4+ addition and the seawater changes from carbon sink to carbon source of atmospheric CO2 and the intensity of carbon source has a positive relationship with the concentration of NH4+. At the NO2- addition groups, the concentrations of HCO3- and p (CO2) decrease while pH and CO3(2-) increase with time scale and the seawater acts as a strong carbon sink with NO2- addition of 7.90 micromol x L(-1). While at the other NO2- concentration levels, the carbon sink is weak in seawater. The Chl-a concentration of nutrient addition groups compared with control (delta Chl-a) shows a significant negative correlation with delta p (CO2) (r = -0.87, p < 0.000 1, n = 16). The main controlling factor to the variation of inorganic carbon system is the adaptation of phytoplankton to different form and concentration of nitrogen.

[Variation characteristics and controlling factors of heavy metals in the South Yellow Sea surface seawaters].

Based on the 8 cruises data of surface seawater heavy metals and other related environmental factors from 1997 to 2004 of the South Yellow Sea (SYS), distribution patterns, mechanisms controlling the distributions and pollution levels of heavy metals (As, Cd, Cu, Hg, Pb, Zn) were studied with the data of 2003-10, and 8-year-fluctuation trends of heavy metals were also discussed. The average concentrations of heavy metals in surface seawater were 2.33, 0.078, 1.41, 0.003 6, 0.37, 6.21 microg/L respectively. The average concentrations showed a relatively stable trend in 8 years, except Zn's distinct upward tendency. The distribution patterns corresponded to the distance away from the coastline,that was, the content of heavy metals (except Pb) was low in central area while high inshore. Those were responses of human activity in the marginal sea, however, in some local areas, Pb was controlled by atmospheric deposition, Cd was relative to pH and salinity, Hg was related to organic carbon, Cu and Zn were influenced by runoff and drainage, and the resuspending of sediments played important roles on the content and distribution of As. Compared to the Marine Water Quality Standard of China, heavy metals indicated that SYS was a first class sea, and Ecological Risk Index analysis showed that SYS was a low ecological risk sea. In conclusion, seawater quality of heavy metals in SYS surface seawater is relatively good in general.