Temporal and spatial variations and impact factors of nutrients in Bohai Bay, China.
The temporal and spatial distributions of dissolved inorganic nitrogen (DIN), dissolved inorganic phosphorus (DIP), and dissolved silicate (DSi), and their long-term changes were investigated in Bohai Bay (BHB) in spring, summer, and autumn (2013-2014). The high DIN values were consistently distributed in the western inshore waters, mainly determined by terrestrial factors, e.g., riverine input, while DIP and DSi were mostly distributed in the southern coastal waters, the central BHB, or near the sea port Caofeidian in northern BHB, largely related to non-terrestrial factors, e.g., sediment release. Based on the nutrient distribution, BHB could be partitioned into western and eastern parts, with -15 m depth as the separation. The long-term variations of nutrients since 2000 showed an increase in DIN and decreases in DIP and DSi. Relatively slow changes in DIN and DIP and a rapid decrease in DSi were exhibited in summer, which was associated with precipitation and sediment release.
Liu X
，Liu D
，Wang Y
，Shi Y
，Wang Y
，Sun X
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Composition and distribution of nutrients and environmental capacity in Dapeng Bay, northern South China Sea.
Seawater physicochemical parameters and environmental capacity are important ecological indicators and typical features of the marine environment. It has great significance in the marine material cycle and ecological health. In September 2021 (wet season) and March 2022 (dry season), two voyage investigations were conducted at 12 stations (D1-D12) on Dapeng Bay (DPB), northern South China Sea. The distribution of nutrient, water-quality status, environmental capacity, and impact of ecological environment were discussed. Results showed that NH4-N was the main form of dissolved inorganic nitrogen (DIN) during the wet season, with concentrations ranging from 0.008 mg/L to 0.109 mg/L, accounting for ~53 % of DIN. Conversely, NO3-N was the main form of DIN during the dry season, with concentrations ranging from 0.005 mg/L to 0.117 mg/L, accounting for ~50 % of DIN. The DIP concentration ranged from 0.002 mg/L to 0.019 mg/L, accounting for ~51 % and 31 % of the total dissolved phosphorus in the wet and dry seasons, respectively. The distributions of NH4-N, NO3-N, NO2-N, and DIP were relatively similar, decreasing from the inner bay to the outer bay. The eutrophication indices of 12 stations <1, indicating a poor eutrophication state. Single-factor indices including chemical oxygen demand (COD), DIN, and dissolved inorganic phosphorus (DIP) were less than the class I seawater-quality standard. However, except for station D1, the overall water quality was good. Dissolved oxygen with DIP had a significantly negative correlation during the dry season, indicating that DIP was primarily dominated by marine biological activity and organic-matter decomposition. The remaining environmental capacities of COD, DIN, and DIP in DPB were calculated to be 13,742, 1418, and 141 tons, respectively. Based on the functional-zone division of the sea area, the remaining environmental capacities of COD, DIN, and DIP were exceeded 75 % of the total environmental capacity. This study provided a scientific basis for the protection of marine ecological environment and the sustainable development of DPB.
Wu K
，Xiu B
，Cui D
，Lu D
，Yang B
，Liang S
，Zhou J
，Huang H
，Peng S
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Aerosol concentrations and atmospheric dry deposition fluxes of nutrients over Daya Bay, South China Sea.
Based on one and a half years of observations (September 2015 to March 2017) in Daya Bay, we analysed the nutrient concentrations in aerosols and calculated dry deposition fluxes of nutrients. DON was the dominant species of TDN in aerosol particles, accounting for 63.3%. The mean values of DIP, DOP and DSi were 0.78, 0.61 and 2.6 nmol·m-3, respectively. The mean fluxes of nutrients (TDN, TDP and DSi) from dry deposition during the field observation were 2150, 7.4 and 28.2 μmol·m-2·month-1, respectively. The fluxes of nitrogen species show a seasonal pattern with higher input in spring and winter. The dry deposition of nutrients accounted for approximately 20% of the total deposition budget. The molar ratios of DIN/DIP in the dry deposition (mean value 167) suggest that atmospheric dry deposition of nutrients may increase the risk of the unbalanced nutrient condition in the seawater column of Daya Bay.
Wu Y
，Zhang J
，Liu S
，Jiang Z
，Huang X
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Effect of submarine groundwater discharge on nutrient distribution and eutrophication in Liaodong Bay, China.
Driven by the anthropogenic activities associated with coastal settlements, eutrophication has become a global issue. Submarine groundwater discharge (SGD) is a significant continuous pathway for transporting nutrients from land to coastal waters, but its influence on eutrophication in Liaodong Bay (LDB) has received limited attention. In this study, radium isotopes and nutrient data from coastal waters were analyzed to evaluate the SGD flux and its implications for potential eutrophication in LDB. We found that the mean concentrations of dissolved inorganic nitrogen (DIN), phosphorous (DIP), and silicate (DSi) in groundwater were higher than those of seawater and river water. Based on 223Ra and 228Ra mass balance models, the SGD fluxes were estimated to be (0.53-2.03) × 109 m3/d, of which the fresh SGD accounted for 4 %-15 %. SGD is a vital invisible source of nutrients, contributing more than 79 % of the total inputs of DIN, DIP, and DSi into LDB. With high DIN/DIP ratios (average=85.8) and large nutrient inputs, SGD may significantly drive the phosphorus limitation and eutrophication in LDB. This study shows that SGD-derived nutrient fluxes should be considered in the assessment of water eutrophication for the formulation of future environmental management protocols in coastal systems.
Luo M
，Zhang Y
，Xiao K
，Wang X
，Zhang X
，Li G
，Li H
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