Distribution, seasonal variation and influence factors of dissolved inorganic arsenic in the Sanggou Bay

The biogeochemical behavior of arsenic in the aquatic environment has already captured the attentions of scientists due to its complex forms and toxicity. Four cruises were carried out in April, August, October 2011 and January 2012 in the Sanggou Bay. The concentrations of total dissolved inorganic arsenic (TDIAs, TDIAs=[As⁵⁺]+[As³⁺]) and arsenite (As³⁺) were measured by Hydride Generation-Atomic Fluorescence Spectrometry (HG-AFS). The concentrations of TDIAs ranged from 3.4-12.4 nmol·L^-1 in April, 8.9-16.9 nmol·L^-1 in August, 14.7-21.3 nmol·L^-1 in October and 13.8-21.9 nmol·L^-1 in January. The concentrations of arsenite ranged from 0.3-2.1 nmol·L^-1, 0.4-3.8 nmol·L^-1, 1.8-4.0 nmol·L^-1 and 0.3-2.9 nmol·L^-1 during four cruises, respectively. The concentrations of TDIAs in spring and summer were lower than those in autumn and winter, and high values of TDIAs appeared in the bay-mouth and the coastal estuary. The concentrations of arsenite in spring and winter were lower than those in summer and autumn. The maximum As³⁺/TDIAs ratios appeared in summer. The mean value of TDIAs in the Sanggou Bay was (13.9±4.7) nmol·L^-1, which was lower than the national primary drinking in water Standards from USEPA and met the first grade water quality based on the environmental quality standards for surface water of China. It indicates that there is no obvious anthropogenic pollution. The concentrations of TDIAs in the Sanggou Bay were lower than those in the Ailian Bay and the Lidao Bay in spring and summer due to the different hydrological environments and terrestrial inputs. Riverine input, incursion of Yellow Sea and biological activities were the three main factors impacting the distribution of TDIAs in the Sanggou Bay, and the influence of aquaculture activities was particularly significant. The enrichment of arsenic by aquaculture may lead to potential ecological crisis and food safety problems, and need to be paid more attentions to ensure the sustainable development of aquaculture in the Sanggou Bay.