Spatial distribution and potential ecological risk assessment of heavy metals in the sediments of fishing ports along the coasts of the Yellow Sea and Bohai Sea.

More than 1,154 fishing ports are widely distributed in China's coastal areas. To date, however, few studies on the pollution and ecological risks of heavy metals in these fishing ports have been reported. In this study, the heavy metals of 148 sediment samples collected from 37 fishing ports along the coasts of the Yellow Sea and Bohai Sea were detected. The results showed that the average contents of Cu, Pb, Zn, and Cd were 53.58 ± 44.53, 27.90 ± 18.10, 143.52 ± 74.72 and 0.28 ± 0.15 mg/kg, respectively. Based on the geoaccumulation index (Igeo) and the potential ecological risk index (RI), we found that fishing ports were the most severely polluted by Cu, but Cd had the highest ecological risk, and most of fishing ports were in moderate potential ecological risk. The positive correlation between heavy metals and total organic carbon indicated that heavy metals in fishing ports were mainly affected by anthropogenic activities.

Ecological risk assessment of heavy metal pollutants and total petroleum hydrocarbons in sediments of the Bohai Sea, China.

Heavy metals and organic pollutants like total petroleum hydrocarbons (TPHs) in coastal marine sediments are receiving extensive attention, as they may pose a serious threat to the aquatic environment and ecosystem health. To date, however, data on the long-term variations in the levels of sedimentary heavy metals and TPHs as well as their ecological risks are relatively limited. Here, we conducted 12 cruises spanning 3 years in the Bohai Sea and obtained ~1400 sediment samples to explore the long-term variations of heavy metals (i.e., Hg, As, Cu, Zn, Pb, Cd) and TPHs, and to assess their potential ecological risks. The results suggested that the ranges for the levels of Hg, As, Cu, Zn, Pb, Cd, and TPHs in sediments between 2019 and 2021 were <0.01-0.07, 0.23-10.72, 8.07-20.67, 25.52-46.55, 10.94-28.19, 0.14-0.56, and 9.14-18.41 mg kg-1, respectively. Based on the single factor evaluation (Fi) for sediment quality, we found that most of the evaluation factors in the study area met the requirements of sediment quality standard (i.e., Fi < 1), except for the factor of metal Cd in some cases. The implication is that the sediment in the Bohai Sea was fairly clean in terms of heavy metals and TPHs. However, the concentration of metal Cd exceeded the sediment quality standard during May 2019 and 2020 (i.e., Fi > 1), indicating that Cd could be identified as a major pollutant in surface sediments. Also, based on the ecological risk assessment (Ei) of heavy metal pollutants, we found that the metal Cd had reached a level with potential ecological risk in some cases (80 ≤ Ei < 160). As such, we further suggested that the Cd contamination might have a potential risk on the Bohai Sea' ecosystem.

Spatiotemporal evolution of nutrients and the influencing factors in Laizhou Bay over the past 40 years.

The nutrient status in Laizhou Bay has changed in composition and structure as a result of anthropogenic activities and climate change, which has led to several environmental problems (e.g., eutrophication, organic pollution and red tides). To better understand the spatiotemporal variations in dissolved inorganic nitrogen (DIN), dissolved inorganic phosphorus (DIP), and eutrophication in the Laizhou Bay, we collected historical research data and conducted four cruises in 2021. The highest surface DIN was found to occur in autumn and predominantly concentrated in the southwestern bay. The highest surface DIP content was found in winter and distributed in the northwestern bay. Surface organic pollution showed estuaries as the most polluted areas. In the past 40-60 years, the DIN, DIP, and eutrophication have shown an inverted U-shaped trend, and the bay has changed from N limitation to P limitation. Economic development, phytoplankton absorption, and bottom mineral release are factors influencing the content and distribution of nutrient in the bay.

Improved simulation-optimization approach for identifying critical and developable pollution source regions and critical migration processes for pollutant load allocation.

Simulation-optimization approaches are widely used in land-based pollutant load allocation and management. However, existing simulation-optimization approaches do not optimize the entire pathway of pollution (i.e., generation, transportation, and emission). Thus, the selected allocated load scheme and its reduction management are incomplete and non-optimal in supporting effective reduction measures to set in further. This study aims to establish a simulation-optimization load allocation approach covering the entire pathway of pollution and construct separate allocated loads for each migration process. By comparing the allocated loads to the actual pollutant loads, the critical and developable pollution source regions (CPSRs and DPSRs) and the critical pollution migration processes (CPMPs) are identified, and specific pollution management indicators are established for each pollution source region. This approach is applied to the Bohai Rim, which is currently a major economic development center with a most seriously deteriorating sea area in China. The CPSRs, DPSRs, and CPMPs for total nitrogen are identified, and comparisons of the management indicators with existing approaches are made. Water quality under the allocated load emissions is simulated via a simulation water quality model and compared with that of the actual pollutant loads. Quantitative results indicate that the new approach combines the specific mitigation indicators for each CPSR and CPMP when allowing the extra generation of allocated loads for DPRSs while keeping the water quality of the Bohai Sea under control.