Groundwater Pollution: Sources, Mechanisms, and Protection

POSTIGO CRISTINA; MARTINEZ DANIEL; GRONDONA SEBASTIÁN; MIGLIORANZA KARINA SILVIA BEATRIZ

ENCYCLOPEDIA OF THE ANTHROPOCENE

elsevier

Año: 2018; p. 87 - 96

Groundwater pollution, caused or induced by human activities, is a phenomenon that has occurred since the earliest Holocene,about 10,000 years ago, when mankind became sedentary and began to settle villages and farm the land. As a consequence, relevantamounts of nitrogen were released into groundwater from farming activities, and microbial pathogens and bacteria were alsospread in the aquifers from sanitary disposal of domestic waste. Since then, agriculture activities and urbanization have expandedand intensified through time due to population growth, and with them the associated groundwater pollution. Moreover, industryis another relevant human activity responsible for alteration of the groundwater quality. Initially, in this regard, ancient civilizationsthat mined for gemstones, gold, silver, copper, and lead were responsible for releasing essentially inorganic compounds intogroundwater bodies. After the industrial revolution and the later development of the petrochemical and the pharmaceuticalindustries, wastes reaching groundwater also included organic compounds, such as tars, phenols, oils, and complex mixtures ofsynthetic organic chemicals (Morris et al., 2003).p0020 Due to population growth, groundwater pollution has dramatically increased over the past 50 years as a result of intensive andextensive exploitation of this water resource for human consumption (drinking and sanitation) and diverse economic uses(tourism, landscaping, agriculture, energy production, and other industrial purposes), and radical changes in land use. Groundwater over-abstraction lowers the level of the groundwater table. This may result in reduced surface waterAu2naturaldischarge flows, land subsidence, and even groundwater quality impairment. Changes in groundwater flow pattern may displacesaline waters and move the sea water?groundwater interface inland, and moreover, increase surface water infiltration. Furthermore,different quality waters could mix in wells and boreholes, impacting even water quality of deep aquifers (Custodio, 2000).p0030 Land-use practices have an impact on groundwater resources by increasing groundwater demand (e.g., land irrigation foragriculture or irrigation of golf courses in arid and semi-arid areas) and changing recharge patterns. Recharge rate is reduced onsloping ground deforested areas or re-forested areas with nondeciduous species. However, it is substantially increased in areasdedicated to irrigated crops. Land use affects not only the recharge rate but also the recharge quality. In fact, pollutants found in agroundwater body are usually closely related to the activity carried out on the land surface. For instance, in the case of urbanizedareas, nitrogen compounds, synthetic organic chemicals, and pathogens are likely to leach into groundwater. On the other hand,intensification of crop production will be responsible for the release of agro-chemicals (i.e., pesticides and fertilizers) into theaquifer. Besides, in the case of irrigated cropping, an additional hazard arises when reclaimed water is used for irrigation becausepersistent wastewater-derived organic contaminants may eventually reach groundwater.