Characteristics of iron isotopes in high arsenic groundwater systems of the Hetao basin, Inner Mongolia, P.R. China

Twenty eight sediment samples were taken from different depths (1.0∼22 m) at two sites. Twenty nine groundwater samples were collected from hand-pumped tube wells and electric-powered public water supply wells in July 2009. The depths of these wells range between 13 and 100 m. Groundwater was sampled from each well after pumping (usually 20 min). All of samples were filtered through 0.45 μm membrane filters in the field. Water samples for major, trace element and Fe isotope analysis were collected in 100 mL nitric Acid (HNO3)-washed polyethylene bottles, followed by addition of 6 M HNO3 until pH < 2. Those for analysis of As species were preserved with 0.25 M EDTA. Samples for anion analysis were not acidified. At the time of groundwater sampling, parameters, including water temperature, Electrical Conductivity (EC), pH, and Eh, were measured using a multiparameter portable meter (HANNA, HI 9828), which was calibrated using standard solution before use. Concentrations of sulfide, Fe(II), and alkalinity were determined by using a portable spectrophotometer (HACH, DR2800).