Distribution And Main Influencing Factors Of Dissolved Trace Metals In Coastal,Estuarine And Hydrothermal Waters

Coasts and and estuaries are located at the interface of ocean and land,which are subject to intensive human activities,and variable environmental factorsdynamic biogeochemical processes.Therefore,trace metals in these waters are generally experiencing a series of biogeochemical processes.Besides riverine inputs,hydrothermal effluents serve as alternative contributing a large amount of elements into the ocean,and further modify the cycling of trace metals nearby.The study focused on three typical waters including estuarine,coastal and hydrothermal waters,and carefully investigated the distribution of trace metals in these waters,and then examined possible affecting factors contributing to the dynamics of the metals in these waters.We conducted surveys coastal Taipingling waters at Huidong,Guangdong monthly from July to December 2019;Jiulong estuarine waters seasonally in 2019 and the hydrothermal waters at Kueishantao,Taiwan in June 2019,and analylzed water samples for basic hydrological parameters such as temperature,salinity,pH,dissolved oxygen and dissolved trace metals.The results show that dissolved metals are dynamic among different seasons(months):(1)In the Taipinling coastal waters,the dissolved metals showed in relatively high concentrations in August and December.Spatially,dissolved Cu,Cr,Cd and Mn gradually decreased towards offshore,while dissolved V is the opposite;(2)In the waters of Jiulong River estuary and Xiamen Bay,dissolved Cu and Cr in winter were significantly higher than those in other seasons.dissolved Cu and Cr ranged from 4.564.2 nmol/L and 1.0-66.2 nmol/L respectively,with the highest concentration in spring,and in the estuary.Dissolved V was in the range of 4.5-64.2 nmol/L except the realtively high concenrations in winter.Dissolved Mo was in the range of 1.4-118.1 nmol/L in spring and summer,with higher concentrations in the bay.(3)In the hydrothermal waters of Kueishantao,Taiwan,dissolved Cr,Mn,Fe and As are variable along with hydrothermal activities,as theconcentrations were relatively higher as within hydrothermal vents.Cu and Cd showed in a opposite pattern.In summary,the study shows that:(1)dissolved metals in the estuary are mainly affected by the mixing of river water and sea water,as the the concentrations of dissolved metals varies closely along with the salinity.In addition,the estaury is characterized with dynamic environment factors including pH and Eh,which largely altered the valance and concentrations of each metals accordingly.In addition,the adsorption and desorption of metal ions by suspended particles in the estuary affect the metal concentration in the water.Finally,more and more frequent human activities may also be the main reason for the high concentration of dissolved metals in local waters.(2)The concentration of dissolved metals in the hydrothermal area is also affected by salinity and pH.Due to the wide range of temperature and pH,the distribution of dissolved metals shows a correlation with Eh.Fe exists in the form of Fe2O3(s)in the surface layer,and in the form of Fe2+and Fe3+dissolved ions inside the vents,and the concentration increases;there is a similar morphological change of Mn from the surface to the vents.Cu is in the form of ions from the surface to the vents,so the concentration of dissolved Cu does not change.This paper focuses on the distribution of trace metals in different typical coastal waters,and discusses the difference from the circulation mechanism of several metals.