Читать книгу Groundwater Geochemistry - Группа авторов - Страница 20

Commonly salinity problems in groundwater are very prominent in the coastal region, followed by arid and semiarid regions. The coastal areas of Gujarat, Maharashtra, Goa, Kerala, Tamilnadu, Odisha, and West Bengal are facing the problem of saltwater intrusion termed as coastal salinity, and inland salinity problems have been reported in the states of Haryana, Rajasthan, Punjab, and Gujarat, with some limited problems in other states also. Mainly seawater intrusion is responsible for the salinity in groundwater in coastal areas, whereas agricultural wastes, agriculture runoff, heavy uses of fertilizers, and industrial effluents have caused the salinity in arid and semiarid regions. Ion exchange processes, rock–water interaction within subsurface, and the surface water with urban and semi‐urban wastes percolates through the soil and enters into the aquifer system and leads to salinity problems.

The Indian subcontinent has a coastline stretched about 7500 km long. Saltwater can intrude laterally or by coming up from the deeper layer when the groundwater level has dropped below the sea level. Moreover, tides and coastal floods may contribute to salinity in water by infiltration. Seawater intrusion incidents are common and have been observed in several states, including in Tamil Nadu, Pondicherry, and Saurashtra in Gujarat (Mondal et al. 2010; Garduño et al. 2011). There is no uptake of sodium salt by the plants. Only evaporation eliminates the sodium salts from the solution. The most significant source of sodium and chloride in groundwater, particularly in arid and semiarid expanses, is the precipitation of this salt permeating the soil in the shallow water tracts. Na⁺ and Cl⁻ concentration was reported higher in the coastal zone due to saltwater intrusion. Na⁺ concentration increases with Cl⁻ concentration, which resulted in an increase in the weathering of halite minerals in the groundwater. Other sources of Cl⁻ includes natural weathering of bedrocks, volcanic activity, natural brines, saline intrusions, and atmospheric deposition along with the geographical locations, i.e. coastal/inland areas (Grützmacher et al. 2013).