[Spatial Distribution, Speciation, and Ecological Risk Assessment of Heavy Metals in Surface Sediments of Dongjiang Lake, Hunan Province].

To understand the heavy metal pollution status of Dongjiang Lake, the contents and species of heavy metals in the surface sediments were investigated during September 2021, and the heavy metal pollution level and potential ecological risk were evaluated. The results showed that Cd, Pb, As, Cu, Zn, Ni, and Cr contents were in the range of 0.40-34.1, 14.8-1688, 6.99-1155, 6.89-280, 26.2-1739, 6.29-55.4, and 23.3-44.8 mg·kg-1, respectively, with extremely uneven spatial distributions. The highest contents of Cd, Pb, As, Zn, Cu, and Ni were found in the site adjacent to Yaogangxian tungsten ore. The proportion of metal species with bioavailability was high, in which Cd in acid-soluble species was 46.7%-71.5% and Pb in reducible species was 46.8%-67.0%. The bioavailable species of Cu, Zn, Ni, and Cr were 35%-68%, 42%-72%, 26%-51%, and 6%-30%, respectively, although they primarily existed in residual species. According to the geo-accumulation index (Igeo), there was a moderate or extreme pollution status of Cd in all sites, moderate or extreme pollution status of Pb in 90% of sites, and moderate pollution status of As, Cu, and Zn in 30% of sites. The ecological risk factor (Eri) of Cd showed high potential ecological risk in all sites with significantly high potential ecological risk in 80% of sites. Moreover, As and Pb had significantly high potential ecological risk, and Cu had moderate potential ecological risk in S7, which was adjacent to Yaogangxian tungsten ore. There was a high total potential ecological risk in all sites and significantly high potential ecological risk in 50% of sites. Therefore, the surface sediments of Dongjiang Lake were under the combined pollution of Cd, Pb, As, Zn, and Cu with high bioavailability and high total potential ecological risk.

[Response Behaviors of Heavy Metals at Tidal Currents Interface and Salinity Interface in the Estuary Area].

In China, trace metals (such as dissolved Cu, Zn, Pb, Cd, and Cr) are the routine mandatory monitoring indicators in existing Freshwater Quality Standard (FWQS, 2002) and Seawater Quality Standard (SWQS, 1997). Using Daliao River estuary as an example, we tried to research the general response patterns of these metals in estuarine system. Firstly, we determined the location of FSI (freshwater-seawater interface) and TCI (tidal currents interface), which were based on biological, chemical and geographic similarities by descriptive and quantitative methods, respectively. Secondly, two hypotheses were proposed to explain the difference based on distribution coefficient Kd along salinity and SS (suspended solids) gradient, these results revealed that the indicators for As, Cd and Cr may be prone to be affected by salinity, and the ones in the second pattern may be more sensitive to SS. Finally, we classified the response behaviors into two patterns based on the changing trends along the distance and magnitudes affected by the FSI and TCI: 1the obvious boundary break point from FSI for As, Cd and Cr; 2 the boundary zones from TCI for Zn, Cu, Pb and Ni. The partitioning behaviors showed similar changing trends at particle and sediment phases, especially for particle phase, depending on the concentration of SS along the salinity. The difference between general behaviors for the two patterns mainly existed at water phase. In general, this paper highlighted the need to consider the background difference of trace metals and identified the sensitive indicators controlled by different environment factors (such as salinity and SS) based on the native estuarine characteristics. Our work will assist the implementation of updating the current water quality standards in China.

[Study on the changes of macrobenthos communities and their causes in Bohai Bay].

Based on the analysis of macrobenthos samples collected from Bohai Bay, China in 2011 and the data obtained from the nearly the same sampling area during last six years, as well as the hydrological conditions, nutrients and dissolved oxygen, the characteristics of the changes in macrobenthos communities and their response to environmental variables were derived. Results showed that the distribution of the values of species number, abundance, biomass, richness index and diversity index reflected a gradient from the coastline to the open sea with the higher values concentrated at the open sea in the north part of Haihe estuary. The macrobenthos communities showed an obvious fluctuation over last six years, composed of three nodes. The first time node was in 2005 and 2008, the total species number, abundance and biomass maintained relatively high; the second time node was in 2009 and 2010, the values of the above three indices were the lowest in the three time nodes due to the increasing anthropogenic disturbances and natural changes; the third time node was in 2011, the values of the above three indices were the highest since many effective environmental protection measures had been carried out, indicating that the macrobenthos communities were recovered to a certain degree. The integrated impacts from the physical, chemical and biological variables induced by natural changes and anthropogenic disturbances, such as over-fishing, coastal land reclamation and sewage discharge were the triggers for the changes of macrobenthos communities. Furthermore, the variation characteristics of macrobenthic communities and environmental factors were generally in accordance with each other.