Seasonal effects on arsenic in estuaries

Chesapeake Bay, USA, is the largest estuary on Earth and almost all of the arsenic entering the headwaters is As(V). Although inorganic As(V) is consistently the most abundant arsenic species in the estuary, extensive arsenic reduction and methylation occur during warm months (Sanders, Riedel and Osman, 1994), 295 (Millward et al., 1997), 53. The appearance of As(III) and methylarsenic species correlates well with phytoplankton production. Similar seasonal patterns involving arsenic reduction and methylation are seen in other estuaries (Sanders, Riedel and Osman, 1994), 295. 

Any relationships between salinity and arsenic chemistry in estuary waters often vary with location and climate. In some areas, periodic upwelling of high-arsenic and saline bottom waters locally dominates the arsenic chemistry of estuaries (e.g. the Taiwan Strait (Xiankun, Jing and Xinian, 1994), 332). In other situations, wet season flooding of highly arsenic-contaminated river waters increases the arsenic contents and lowers the salinity of estuaries. In contrast, fairly pristine river waters may dilute both estuary salinity and arsenic concentrations during flooding. 

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