What are the factors that can influence the variation of arsenic concentration in rivers? I - Climate II - Mining activity III - Industrial and ur...

c) I, II, III and IV are correct.

All of these factors can influence the variation of arsenic concentration in rivers:

I - Climate: Rainfall can influence the amount of arsenic that is washed into rivers from the soil. In addition, certain climatic conditions can enhance the leaching of arsenic from rocks and soils into groundwater and rivers.

II - Mining activity: Mining can release arsenic into the environment through processes like blasting, which disturbs naturally occurring arsenic in the earth. The tailings (waste material) from mining operations can also contain high levels of arsenic that can enter rivers if not properly managed.

III - Industrial and urban waste disposal: Many industrial processes, especially those involving metal smelting, coal burning, or the use of certain pesticides, can release arsenic into the environment. If this waste is not properly disposed of, it can find its way into rivers. Similarly, untreated urban waste can also contain arsenic.

IV - Distance from the emission source: The concentration of arsenic in a river can decrease the further away you get from the source of pollution due to dilution. However, it can also increase in certain conditions, such as where arsenic-containing sediments are deposited or where water slows down and arsenic has a chance to accumulate.