Study on the seawater quality and its spatial heterogeneity based on principle component analysis: A case study nearshore of Zhuanghe port

In order to reveal the water quality and its spatial pattern nearshore of the north yellow sea, this study evaluated the surface sea water quality in winter of Zhuanghe port.20 sampling sites were setup, and the principle component (PCA) analysis was applied to illustrate the seawater quality, combined with the Krigning spatial interpolation technology to display the spatial heterogeneity.Correlation analysis, regression analysis and redundancy analysis (RDA) were respectively used to reveal the main sources of the pollution and relationship between seawater quality with the geographical position of sampling sites, and to analyze effects of seawater quality on chlorophyll a and dissolved oxygen.Results showed that total inorganic nitrogen of surface seawater was higher than the fourth grade of seawater quality standard, and other water quality parameters all met the first grade.NO₃-N, NO₂-N and PO₄-P were showed significant correlations with each other and with Cd and Cr, illustrating they had similar sources.Inorganic nitrogen, inorganic phosphorus and the related heavy metal elements mainly affected the seawater quality of this area, with a significant spatial heterogeneity along coastline direction, illustrating that seawater quality was also relevant to the utilization way of this area.Coastal water quality calculated by PCA explained 82.67% variation of chlorophyll a and dissolved oxygen.And chlorophyll a was significantly and negatively related with the principal component score which represented the inorganic nitrogen and phosphorus.