How does the Arsenic release to the groundwater?
Recent research suggests that the presence of organic matter may play a key role to release the As in groundwater. There are two sources of organic matter that really make the fresh groundwater contaminated with the As. Internal sources within the aquifer like peat layer may be responsible for the sources of organic matter that are released into the groundwater to cause the groundwater contamination. The external sources like anthropogenic and natural organic matter from the surface of the earth may percolate into the aquifer to release the As to the groundwater.
Here the degradable organic matter derived from multiple sources especially petroleum-derived OM play a key role to continue the microbial activity in the sediments. The fuel to survive the microbes are C from hydrocarbon.
The Role of Organic Matter for the Arsenic contamination
Study on As-rich aquifer from Cambodia and West Bengal, India shows that Organic matter in the sediments is derived from the multiple sources,
- Naturally occurring petroleum
- Organic matter that already existed in the sediments that are laid down at the time of deposition.
- Some OM may be reworked from the older sedimentary rocks and goes upstream
- Surface-derived recent organic matter-rich sediments
These multiple sources of organic matter may act as a key role in the microbial process. Because microbes need Carbon (C) as a fuel for their growth and release the Arsenic from the As- rich sediments to the groundwater. This mechanism is significant in the petroleum-derived organic matter within the aquifer.
By observing some biomarker like hopane and sterane that the OM is derived from the petroleum in Cambodian aquifer.
From this model, it clearly shows the multiple sources of OM that are the responsible for the As release as those are the sources of C and Carbon are the most important elements to survive for the microbes in the sediments and those microbial activity release Arsenic to the Groundwater.