Seasonal variations of dissolved Mn concentration in the surface water of the Changjiang River Estuary and its adjacent area
Manganese(Mn)is an essential trace element for the marine ecosystem.As the transitional zone between rivers and oceans,estuaries have a significant effect on dissolved Mn and its terrigenous input.In this study,the dis-tribution of dissolved Mn,investigated in the surface water of Changjiang River Estuary and its adjacent area dur-ing September 2019(autumn),March 2021(spring)and July 2021(summer),was analyzed by automatic solid phase extraction and inductively coupled plasma mass spectrometry.The results indicated that the average concen-tration and estuarine behaviors of dissolved Mn showed seasonal variations between the three cruises:the maxim-um average concentration occurred in summer and dissolved Mn was removed firstly and then added with the in-crease of salinity;the medium average concentration occurred in autumn and dissolved Mn was mainly removed with the increase of salinity;the minimum average concentration occurred in spring and dissloved Mn was mainly conservative with the increase of salinity.The results of significance test indicated that only in the season when the fresh water had high concentrations,dissloved Mn carried by the Changjiang River had significant influence on the distribution of dissolved Mn in the Changjiang River Estuary and its adjacent area;the distribution of dissolved Mn was co-dominated by a variety of biogeochemical processes in the season when the concentrations were low in the fresh water.The high suspended particulate matter concentrations were the important factor of the removal of dis-solved Mn in the Changjiang Estuary's water with medium-low salinity.And the addition mechanism of dissolved Mn in water with high salinity needs further vestigation.
the Changjiang River Estuary and its adjacent areadissolved Mnseasonal distributionestuarine behaviorsuspended particulate matter