Question

Please answer
In the sediments, we can find concerning substances such as: (heavy metals) & (Polycyclic aromatic hydrocarbons)
Tell how each gets into the runoff?
what are the hazards and effects associated with each, and where it will end up?

Answer 1

Heavy metals such as arsenic, lead, mercury, nickel, chromium, cadmium etc. end up in the river due to effluents dumped from the industries such as mines, ores, heavy grinding, milling. When the effluents are not treated to remove the heavy metals before discharging into waterways, gradually their content increases. Some amount of heavy metal also gets into water due to chemical leaching of metal containing minerals due to acidic rainfall.

These heavy metals as part of sediments along the river bed get into the ecosystem by way of leaching in to the surface water and groundwater and soil, followed by absorption by plants, animals and from them to humans through food and water.

Heavy metals in the river are harmful to aquatic animals like fish and aquatic plants like planktons. In humans heavy metals can cause several disease of lungs, kidney, brain, liver and can adversely impact reproductive, immunological, ciruclatory, cardiovascular, haematological systems.

Polycyclic aromatic hydrocarbon (PAH) are usually produced by oil and coal industry during refining, catalytic cracking and distillative and separation processes. They also gets adsorbed into soil and through the food chain enter plants, animals and humans.

Long term exposure to PAHs may cause damage to kidney, lungs, liver, eyes.