Complex sentence: Arsenic contamination of groundwater is a natural occurring high concentration of arsenic in deeper levels of groundwater, is a high-profile problem due to the use of deep tubewells for water supply in the Ganges Delta, causing serious arsenic poisoning to large numbers of people.
Split into simpler sentences: Arsenic contamination of groundwater is a natural occurring high concentration of arsenic in deeper levels of groundwater. It is a high-profile problem due to the use of deep tubewells for water supply in the Ganges Delta, causing serious arsenic poisoning to large numbers of people.