Heavy metal distribution patterns and their influence factors in Modaomen estuary of the Pearl River

Based on the field data obtained in Modaomen estuary during the salt intrusion period in January 2018, the contamination level and distribution characteristics of heavy metals in this area were analyzed and the influence of environmental factors on the transformation and partitioning of heavy metals were studied. The study area was divided into fresh water zone, mixed zone and salt water zone based on salinity and water stratification level. The contents of particulate and dissolved heavy metals had significant difference between fresh water zone and salt water zone. The particulate heavy metals showed a decreased trend with the increase of salinity. The order of variation coefficients in the spatial distribution of particulate heavy metals was Cd>Cr>Zn>Pb>Cu>As>Ni>Co. The concentrations of dissolved Pb, Cr, As and Co increased gradually in the seaward direction, while the concentrations of Cd, Cu, Ni and Zn showed a "low-high-low" distribution pattern. The order of variation coefficients in the spatial distribution of dissolved heavy metals was Zn>Cr>Cd>Pb>Cu>Co>As>Ni. The partitioning coefficients decreased gradually in the seaward direction. Results of the principal component analysis showed that salinity and suspended sediment concentration are the main environmental factors that affect the partitioning of heavy metals in the estuary.