Table 4.5: Freshwater pollution sources, effects and constituents of concern

Pollution type Primary sources Effects1 Constituents of concern2
Other pollutants include Radioactivity, Fluoride, Selenium.
Sources and notes:
1 Principally from Revenga and Mock, 2000. Their compilation from Taylor and Smith, 1997; Shiklomanov, 1997; UNEP/GEMS, 1995
2 From R. Peters, W. Beck, personal communication, 2004.
3 Micro-organic pollutant list now includes a suite of endocrin disrupters, antioxidants, plasticizers, fire retardants, insect repellents, solvents, insecticides, herbicides,
fragrances, food additives, prescription drugs and pharmaceuticals (e.g., birth control, antibiotics, etc.), non-prescription drugs (e.g., caffeine, nicotine and derivatives, stimulants).
1 Organic matter Industrial wastewater and domestic sewage. Depletion of oxygen from the water column as it decomposes, stress or suffocating aquatic life. Biological Oxygen Demand (BOD), Dissolved Organic Carbon (DOC), Dissolved Oxygen (DO)
2 Pathogens and microbial contaminants Domestic sewage, cattle and other livestock, natural sources. Spreads infectious diseases through contaminated drinking water supplies leading to diarrhoeal disease and intestinal parasites, increased childhood mortality in developing countries. Shigella, Salmonella, Cryptosporidium, Fecal coliform (Coliform), Escherichia coli (mammal faeces – E. Coli)
3 Nutrients Principally runoff from agricultural lands and urban areas but also from some industrial discharge. Over-stimulates growth of algae (eutrophication) which then decomposes, robbing water of oxygen and harming aquatic life. High levels of nitrate in drinking water lead to illness in humans. Total N (organic + inorganic), total P (organic + inorganic) For eutrophication: (Dissolved Oxygen, Individual N species (NH4, NO2, NO3, Organic N), Orthophosphate)
4 Salinization  Leached from alkaline soils by over irrigation or by over-pumping coastal aquifers resulting in saltwater intrusion.  Salt build-up in soils which kills crops or reduces yields. Renders freshwater supplies undrinkable.  Electrical conductivity, Chloride (followed, post characterization by full suite of major cations (Ca, Mg), anions
5 Acidification (precipitation or runoff) Sulphur, Nitrogen oxides and particulates from electric power generation, industrial stack and auto/truck emissions (wet and dry deposition). Acid mine drainage from tailings as well as mines. Acidifies lakes and streams which negatively impacts aquatic organisms and leaches heavy metals such as aluminium from soils into water bodies. pH
6 Heavy metals Industries and mining sites. Persists in freshwater environments such as river sediments and wetlands for long periods. Accumulates in the tissues of fish and shellfish. Can be toxic to both aquatic organisms and humans who consume them. Pb, Cd, Zn, Cu, Ni, Cr, Hg, As (particularly groundwater)
7 Toxic organic compounds and micro-organic pollutants.3 Wide variety of sources from industrial sites, automobiles, farmers, home gardeners, municipal wastewaters. A range of toxic effects in aquatic fauna and humans from mild immune suppression to acute poisoning or reproductive failure. PAHs, PCBs, pesticides (lindane, DDT, PCP, Aldrin, Dieldrin, Endrin, Isodrin, hexachlorobenzene)
8 Thermal Fragmentation of rivers by dams and reservoirs slowing water and allowing it to warm. Industry from cooling towers and other end-of-pipe above-ambient temperature discharges Changes in oxygen levels and decomposition rate of organic matter in the water column. May shift the species composition of the receiving water body. Temperature
9 Silt and suspended particles Natural soil erosion, agriculture, road building, deforestation, construction and other land use changes. Reduces water quality for drinking and recreation and degrades aquatic habitats by smothering them with silt, disrupting spawning and interfering with feeding. Total suspended solids, turbidity

Source: UNESCO  The United Nations World Water Development Report 2
Section 2: Changing Natural Systems,
Chapter 4, Part 2. Nature, Variability and Availability, p.141

Related publication:
Water Resources homeWater Resources
Other Figures & Tables on this publication:

Table 4.1: Precipitation distribution into surface water and groundwater components (by climate region)

Table 4.2: Selected large aquifer systems with non-renewables groundwater resources

Table 4.3: Water availability information by country (AQUASTAT, FAO 2005)

Table 4.4: Major principal sources and impacts of sedimentation

Table 4.5: Freshwater pollution sources, effects and constituents of concern

Table 4.6: Spatial and time scales within which pollution occurs and can be remediated

Table 4.7: Potential applications for reclaimed water

Figure 4.1: Global distribution of the world’s water

Figure 4.2: Schematic of the hydrologic cycle components in present-day setting

Figure 4.3: Oxygen-18 content of stream water along the main stem of large rivers

Figure 4.4: Variations in continental river runoff through most of the twentieth century (deviations from average values)

Figure 4.5: Typical hydrographs in accordance with climatic settings

Figure 4.6: Acid rain and its deposition processes

Figure 4.7: Five-year mean of the pH level in rainfall in the eastern regions of Canada and the US

Figure 4.8: Primary sources of groundwater pollution

Map 4.1

Map 4.2

Map 4.3: Groundwater abstraction rate as a percentage of mean recharge

Aral Sea