Fractionation Analysis of Iron in Coastal Rivers to Yantai Sishili Bay with a Bismuth Microrods-Based Electrochemical Sensor

As an essential metal micronutrient, Fe plays an important role in the marine biogeochemical cycling process, and the bioavailability of Fe has a direct relationship with its fractions in water. The fractionation analysis of iron in main coastal rivers to Yantai Sishili Bay was achieved with an electrochemical sensor based on bismuth microrods (BiMRs). The sensor was characterized by scanning electron microscope and electrochemical methods, and the reliability of the sensor was verified by the determination of the standard samples. Different fractions of iron in coastal river waters, including total iron (TFe), total dissolved iron (TDFe) and particulate iron (PFe), have been determined by combining simple sample pretreatments and cathodic stripping voltammetry with the BiMRs-based sensor. The average concentrations of TFe in Guangdang River, Xin’an River and Yuniao River were 4.02, 3.66 and 4.42 μmol L−1, respectively. The main fractionation of iron in three rivers was PFe, which accounts for 84.46%, 87.56% and 92.34%, respectively. Furthermore, the relationships between iron concentration and tidal action, salinity, dissolved oxygen and other factors were also investigated.