Distribution and influencing factors of dissolved manganese in the northern South China Sea in autumn
The concentrations of dissolved manganese(dMn)in the Zhujiang Estuary-Qiongdong Sea area in Octo-ber 2017 and the northeast-central part of the South China Sea(SCS)in September 2020(the research areas are re-ferred to as the northern South China Sea,NSCS)were determined by online concentration-flow injection analysis.The results showed that the concentration of dMn in the NSCS ranged from 0.7 nmol/L to 8.6 nmol/L,with an aver-age of(2.6±1.3)nmol/L.The concentration of dMn was higher in the coastal area and decreased with distance from the coast,dMn in the Zhujiang Estuary-Qiongdong Sea area was higher than that in the northern and central of the SCS.The vertical profiles of dMn normally was highest in the surface layer,gradually decreased with depth and increased dMn in the intermediate water with relatively low dissolved oxygen,and then kept low concentration in the deep water.The factors affecting the distribution of dMn in the NSCS mainly include water mass mixing,partic-ulate adsorption-desorption and regeneration in low oxygen environment etc.Mn-rich shelf water was transported to the slope of NSCS along the upper layer(＜80 m).Using salinity and dMn as tracer to study the intrusion of Kur-oshio subsurface water(KSSW)into the SCS in autumn 2020,the results showed that the KSSW intrusion was mainly concentrated at the potential density surfaces of 24.5～25.0 kg/m3,and the intrusion scope extending to 117.5°E in the west and 20°N in the south.The concentration of dMn in the intermediate water of the central SCS(400～1 500 m,DO＜100 μmol/L)increased,and the concentration of dMn was positively correlated with apparent oxygen consumption(AOU),which indicated that remineralization process in low oxygen environment(DO＜100 μmol/L)affected the distribution of dMn in the NSCS.
dissolved manganesedistributioninfluencing factorsthe northern South China Sea
万方数据
维普
