What is groundwater? Factors causing pollution and degradation of groundwater

What is groundwater?

"Groundwater is a form of underground water, stored in loose sedimentary rock layers such as sediment, grit, sandstone, in cracks, karst caves under the earth's surface, which can be exploited for activities. human life".

According to distribution depth, groundwater can be divided into surface groundwater and deep aquifer. The common feature of groundwater is the ability to move quickly in the porous soil layers, forming underground flows according to the topography. Surface groundwater usually does not have a layer separating it from the topography. Therefore, the composition and water level vary greatly, depending on the state of the surface water. Surface groundwater is very susceptible to pollution. Deep groundwater is usually located in the porous rock layer separated above and below by impermeable layers. According to spatial distribution, a deep aquifer usually has three functional zones:

• Water intake area.
• Water transfer area.
• Pressurized water extraction area.

The distance between the water collection area and the water exploitation area is usually quite long, from a few tens to several hundred kilometers. Water boreholes in mining areas are often pressurized. This type of groundwater has good quality and stable flow. In areas where carbonate rock is developed, there is often karst groundwater that moves along karst cracks. In coastal dunes, there are often freshwater lenses located above sea level.

Groundwater is the main source of drinking water in many countries.

Groundwater pollution like?

Groundwater is the main source of drinking water in many countries and populations around the world. Therefore, groundwater pollution has a great influence on the quality of human living environment. Factors that pollute and degrade groundwater include:

• Natural factors such as salinity, alum contamination, Fe, Mn and some other metals.
• Artificial agents such as high concentrations of heavy metals, concentrations of NO- , NO-, NH +, PO4 etc. exceed permissible standards, contamination by microorganisms.
• Degradation of groundwater reserves is manifested by reduction of exploitation capacity, lowering of groundwater level, and land subsidence.

How is water contaminated with heavy metals?

Heavy metals with Hg, Cd, Pb, As, Sb, Cr, Cu, Zn, Mn, etc. usually do not participate or participate in the biochemical processes of organisms and often accumulate in the body. they. Therefore, they are elements that are toxic to organisms. Heavy metal contamination of water is common in water basins near industrial zones, big cities and mining areas. Heavy metal pollution manifests itself in high concentrations of heavy metals in water. In some cases, a mass death of fish and aquatic life occurred.

The main cause of heavy metal pollution is the process of pouring into the environment industrial wastewater and toxic wastewater without treatment or unsatisfactory treatment. Water pollution by heavy metals has a negative impact on the living environment of organisms and humans. Heavy metals accumulate along the food chain and penetrate the human body. Contaminated surface water will spread pollutants into groundwater, soil, and other associated environmental components. To limit water pollution, it is necessary to strengthen measures to treat industrial wastewater, and to well manage livestock in a potentially polluted environment such as raising fish and growing vegetables with wastewater.

How is water contaminated with microorganisms?

Sinh vật có mặt trong môi trường nước ở nhiều dạng khác nhau. Bên cạnh các sinh vật có ích có nhiều nhóm sinh vật gây bệnh hoặc truyền bệnh cho người và sinh vật. Trong số này, đáng chú ý là các loại vi khuẩn, siêu vi khuẩn và ký sinh trùng gây bệnh như các loại ký sinh trùng bệnh tả, lỵ, thương hàn, sốt rét, siêu vi khuẩn viêm gan B, siêu vi khuẩn viêm não Nhật bản, giun đỏ, trứng giun v.v.

Sources of biological pollution for the water environment are mainly garbage feces, domestic wastewater, dead organisms, hospital wastewater, etc. To assess water quality from the perspective of biological agent pollution, coliform index is commonly used. This is an indicator that reflects the amount in water of coliform bacteria, which are not usually pathogenic to humans and animals, but represent water contamination by biological agents. To determine the coliform index, people culture samples in special solutions and count them after a certain time. Water pollution is determined according to environmental standard values.

This phenomenon is common in developing and underdeveloped countries in the world. According to a World Bank report in 1992, contaminated water causes diarrheal disease that kills 3 million people and sickens 900 million people every year. There have been five very large numbers of people infected with diseases in the world such as ascariasis 900 million people, schistosomiasis 600 million people. In order to limit the negative impacts of microbial contamination of surface water, it is necessary to study measures to treat wastewater, improve the living environment sanitation of the population, and organize well medical and epidemic activities. plus service.

How is water contaminated by pesticides and chemical fertilizers?

Water pollution by pesticides and chemical fertilizers is a common phenomenon in intensive agricultural areas around the world. In the process of using pesticides and chemical fertilizers, a significant amount of drugs and fertilizers are not received by plants. They will spread and and accumulate in soil, water and agricultural products as fertilizer and pesticide residues.

Other negative effects of pesticide and fertilizer pollution are degradation of environmental quality in agricultural areas such as soil and water eutrophication, soil and water pollution, and biodiversity loss. of rural areas, decrease of natural enemies, increase the resistance of pests and diseases to pesticides.

*Excerpt 200 questions/answers about the environment

Editor: Assoc. Prof. Dr. Truong Manh Tien

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