**3.1 Water and soil chemistry**

Prevalence of total arsenic (As) in soil and water sources collected from areas at a gap of 0.5–1.0 km in the winter and spring seasons at Sonargaon is given in **Table 1**. Arsenic in pond water was due to seepage and water flow from the household use of As-contaminated HTW. The concentration of iron had direct correlation to the amount of arsenic present. Rice field soils in the areas had highest arsenic ranging from 5.83 to 8.01 mg/kg (due to weekly irrigation about nine times with STW water), followed by wheat (due to broadcast seeding and standing irrigation after 20, 60, and 80 days (before flowering)) and vegetable fields (due to non-standing irrigation two times during dry period). Water from the HTW was found to have 131 ± 0.1 μg As/l (10 years old) to 475.5 ± 10.6 μg As/l (25 years old). Similarly, 1-year-old STW water was found to have 92.2 ± 1.5 μg As/l, while the 3-year-old one had 495.0 ± 10 μg As/l indicating that the older the tube well, the more is the groundwater arsenic indicating tube wells having less than 100 μg As/l in the early 2000s most likely have now increased to several hundred or more.

The water of 1-year-old DTW was with very little or no arsenic, while STW had 150 ± 3.0 μg As/l and has been found to be moderately affected [1] at village Kachua in Meghna floodplain. In Ganges floodplain, there are reports of an average 210 μg As/l in DTW water in many areas of Jessore district and in highly affected areas (**Figure 1**). The most alarming point is that each and every crop had arsenic toxicity for irrigating with GW (**Table 1**). To get a good yield, irrigation is a must and alternative source(s) need to be found out.

Quality of pond and STW waters used in irrigating rice cultivation experiments is shown in **Figure 2**.
