Arsenic-safe alternate aquifers and their hydraulic characteristics in contaminated areas of Middle Ganga Plain, Eastern India

Abstract

Arsenic groundwater contamination exceeding 0.05 mg/l affecting the Newer Alluvial tracts of Patna and Bhojpur, the two worst affected districts located in the Middle Ganga Plain in the Bihar state, has been studied The area is underlain by two-tier Quaternary aquifer systems within a depth of 300 m below ground level, separated by a 15-32-m-thick clay/sandy clay aquitard. The upper part (<50 m depth) of the shallow aquifer system is arsenic-contaminated. The deeper aquifer system (lying below 120-130 m depth) exhibits low arsenic load (max 0.0035 mg/l), having hydraulic conductivity between 64.88 and 82.04 m/day. Groundwater in the deeper aquifer occurs under semi-confined to confined condition due to poor hydraulic conductivity of the middle clay (4.7×10(-2)-7.2×10(-3) m/day). Hydraulic head of the deeper aquifer remains close to the surface than the shallow aquifer. The two aquifer systems in the Newer Alluvium are replaced by a thick single aquifer system in the adjoining Older Alluvium, within a depth of 330 m below ground. In the arsenic-contaminated area, deeper aquifer is protected by a middle clay, which may be developed for community drinking water supply by deep tube wells having a yield capacity of 150 m3/h.

Hydrogeological typologies of the Indo-Gangetic basin alluvial aquifer, South Asia

“…Alluvium grain size: Alluvium grain-size changes from generally coarse gravel and sands (85% sands and gravels), up to boulder-sized, close to the mountain margins of the IGB aquifer and within megafan deposits (Day 1971;Shukla et al 2001;Singh 1996;Singhal et al 2010), to medium sands (70% fine-medium sands) within the central parts of the Ganges and Indus basin plains (Singh et al 1999;Saha et al 2011), to finally silt dominated (70% silts) deltaic deposits in the coastal regions (Goodbred and Kuehl 2000;BGS and DPHE 2001;Acharyya 2005; Fig. 3).…”

Bioremediation and Tolerance of Humans to Heavy Metals through Microbial Processes: a Potential Role for Probiotics?

“…Natural contamination of groundwater is a health problem globally but especially in India (88) and Bangladesh (100). It has been estimated that in these two countries alone, 60 million to 100 million people are at risk because of consumption of arsenic-contaminated drinking water.…”

Delineation of Holocene–Pleistocene aquifer system in parts of Middle Ganga Plain, Bihar, Eastern India through DC resistivity survey

“…The lower part (older alluvium) marked by sand, silt and clay is assigned to the Pleistocene age. The upper segment (newer alluvium) is divided into Belhar and Diara formations and assigned to the Holocene age (Saha et al 2010). The younger unit covers a 10-to 25-km wide stretch along the Ganga, is characteristically unoxidized and consists of sediments deposited in a fluvial and fluvio-lacustrine setup (Singh 2004) marked as Holocene sediments.…”

“…The Holocene newer alluvium surface was recognized by gray-to black-colored organic-rich argillaceous sediments in entrenched channels and floodplains of Ganga River, while the Pleistocene older alluvium surface was recognized by yellow-brown colored sediments with profuse calcareous and ferruginous concretions. A 25-to 35-km southern stretch along the east-west flowing Ganga River is marked as the boundary of newer alluvium (Saha et al 2010, Acharya 2005. Sone River has undergone avulsion several (9) times, in the recent geological past (\10,000 years) and its abandoned channels mostly lie within *50 km east from the present channel course .…”

“…A clay bed (*25-m thick) separating the Holocene and Pleistocene aquifer is delineated (Saha et al 2010). The clay bed vertically separates the aquifer system; the shallow aquifer occurring above the clay bed is assigned to the Holocene age and the aquifer occurring below this clay bed is marked as a Pleistocene aquifer.…”