The document discusses arsenic levels in the rivers of the Amazon Basin. It notes that the rivers flowing from the Andes mountains bring over 5 tons of arsenic per year to the Atlantic Ocean through transported sediments and dissolved in the water. The combined arsenic content of about 1 mg/m3 is close to the maximum acceptable levels for drinking water in most countries. As the sediments are deposited in the Amazon Fan area, arsenic bound to iron oxides and hydroxides is released into more soluble forms, causing higher arsenic concentrations along coastal areas. Water flow and sediment data is collected throughout the Brazilian Amazon basin to study arsenic distribution.