Speciation of Arsenic Across Water-Sediment Interface of Falgu River

Abstract

Two predominant species of arsenic compounds, As(III) and As(V), are found in soils and natural water and they have been classified as carcinogens. The focus of the present study was to examine the speciation of Arsenic (As) across the water-sediment interface at the confluence of drainage for Gaya city and the Falgu River. Gas Chromatography (GC) coupled to Inductively Coupled Plasma Mass Spectrometry (ICP-MS) was used to analyze the organic arsenic species while the inorganic arsenic species, As(III) and As(V), were analyzed by Anion Exchange Chromatography (AEC) coupled with Inductively Coupled Plasma Mass Spectrometry (ICP-MS). The determination of total arsenic load was carried out by colorimetric method using silver diethyldithiocarbamate and was measured at 535 nm. Results revealed that the waters contained Monomethylarsine (MMA), Dimethylarsine (DMA), Trimethylarsine (TMA), As(III) as Arsenite (AsO₃^-3) and As(V) as Arsenate (AsO₄^-3). However, the methylated species were found in much higher concentrations in pore water from the sediment as compared to in the free water. The high levels of arsenic compounds found at the drainage sites pose a threat to human health and as such should be monitored and remediated promptly by the local and state governments.