3. Sampling and methods
A total of 17 water points were sampled in May 2012, after the conclusion of all remedial actions. The
sampling was preceded by few rainy days, after a prolonged dry period. For a comparison between old
and new data, sampling followed the scheme of the campaigns on February 2000 and January 2001,corresponding to periods of minimum flow and flood, respectively [2] (Fig. 1). Fourteen samples were
collected along the BLs (BL-type sample), two samples (Tr1b and Tr2b) from low-As metal-rich
tributaries in the upper BLs course (As