Coastal ecological security assessment in Laizhou Bay, China: from the perspective of demographic-social-economic-natural complex ecosystem.

Assessment of ecological security is essential for understanding the status of bay ecosystem and developing appropriate management strategy. Based on the driving force-pressure-state-impact-response (DPSIR) model, the demographic, economic, social, and ecological data of Laizhou Bay and its three neighboring counties were selected for the period from 2015 to 2021. An ecological security evaluation index system of Laizhou Bay containing 26 indicators was established, and the weights of each indicator were determined by the methods of AHP and EWM, and a comprehensive evaluation of the ecological security of Laizhou Bay was carried out by ESI. Correlations between indicators were analyzed by the Spearman's rank coefficient of correlation. The results showed that there were significant correlations between marine conditions and indicators such as population size in the surrounding area, mariculture area, industrial and domestic wastewater discharge, and treatment rate. Overall, from 2015 to 2021, the ecological security of Laizhou Bay showed a favorable trend, from a relatively unsafe level to a generally safe level, and then to a relatively safe level. Through the comprehensive evaluation of the ecological security of Laizhou Bay, we can recognize the utilization of marine resources and ecological carrying capacity, guide the rational development and utilization of marine resources, and promote the sustainable development of the marine economy.

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.

A Low-Cost Electrochemical Method for the Determination of Sulfadiazine in Aquaculture Wastewater.

As the concept of green development spreads worldwide, environmental protection awareness for production and life has been continuously strengthened. Antibiotic residues in aquaculture wastewaters aggravate environmental pollution and threaten human health. Therefore, the detection of residual antibiotics in wastewater is crucial. In this paper, a new, simple, and low-cost method based on the glassy carbon electrode electrochemical sensor for the detection of sulfadiazine in aquaculture wastewater was developed without using complex materials to modify the electrode surface, to detect sulfadiazine which electrochemically oxidizes directly. The electrochemical performance of the sensor was studied and optimized with differential pulse voltammetry and cyclic voltammetry in the three-electrode system. The optimal electrolyte was acetic acid-sodium acetate buffer, and the optimal pH was 4.0. Finally, based on the optimized conditions, the newly established method showed satisfactory results for detecting sulfadiazine in aquaculture wastewater. The concentration of sulfadiazine and the peak current intensity showed a linear relationship in the range of 20 to 300 µmol/L, and the limit of detection was 6.14 µmol/L, the recovery rate of standard addition was 87-95%, with satisfactory reproducibility and low interference.

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.

Eutrophication status assessment in the Laizhou Bay, Bohai Sea: Further evidence for the ecosystem degradation.

Laizhou Bay is plagued by many environmental problems (e.g., acidification and eutrophication) that are likely to increase in the coming decades along with social and demographic trends. We thus conducted 12 cruises from July 2019 to December 2021 in the Laizhou Bay to evaluate the potential influences of human activities on its eutrophication status. The results showed that the parameters of dissolved inorganic nitrogen (DIN) and oxygen (DO) exceeded the water quality standard in some cases during the past 3 years, suggesting DIN and DO were the crucial factors controlling water quality in the bay. Meanwhile, DIN was identified as a major pollutant in the region, and played an important role in driving the phytoplankton dynamics. Furthermore, with the increases in human-related nutrient inputs (especially DIN), the bay environment reached the mild eutrophication level and was probably at risk from excessive nutrient loads at present, further evidencing the ecosystem degradation.