Sources of Water and Soil Pollutants
Surface water can be contaminated by point or nonpoint sources. An effluent pipe from an industrial plant or a sewage-treatment plant is an example of a point source. On the other hand, a field from which fertilizers and pesticides are drained by rainwater into a river is an example of a nonpoint source, as referred in chapter 2.
Industrial wastes (e.g. food processing wastes, wastes from paper mills, etc.) probably constitute the greatest single pollution problem in soil and water. These contaminants include organic wastes such as solvents, inorganic wastes (e.g. chromium), and many unknown chemicals (e.g. non-degradable chemicals). Contamination of soil and water results when by-product chemicals are not properly disposed of or conserved. Additionally, industrial accidents may lead to severe local contamination.
Domestic and municipal wastes (e.g. personal hygiene and cosmetic products such as fragrances, etc., solid hospital wastes), both from sewage and from disposal of chemicals, are another major source of chemical pollutants. At the turn of the twentieth century, municipal wastes received no treatment and were discharged directly into rivers or oceans. Even today, many older treatment plants do not provide sufficient treatment, especially plants in which both storm water - carries solid and liquid items - and sewage are combined. In addition to organic matter, fertilizers, pesticides, detergents, and metals are significant pollutants discharged from urban areas.
Contamination of water and soil also results from the use of pesticides and fertilizers. Persistent pesticides applied directly to the soil have the potential to move from the soil into the water and therefore enter the food chain from both soil and water. In a similar way, fertilizers leach out of the soil or runoff during rain events and flow into the natural water systems. In this way, the agricultural processes contribute to water and soil pollution.
Ordinary landfills are another source of chemical substances that enter the soil. Moreover, contamination of water and soil can result from fallout from atmospheric pollution (e.g., through acid rain (as explained in unit 3)). For example, toxic fumes from the regulated landfills contain chemicals that can fall back to the earth in the form of acid rain and can damage the soil profile.
Oceans are crossed by shipping routes bustling with tankers, container ships and bulk carriers, transporting more than 90% of global trade, including oils and many hazardous chemicals (HNS). The constant growth in the volume of chemicals that are transported by sea increases the risk of accidental spills. Pollution from petroleum compounds has been a major concern since the mid-1960s. In 1967, the first major accident involving an oil tanker occurred. The TorreyCanyon ran onto rocks in the English Channel, spilling oil that washed onto the shores of England and France. For example, it is estimated that at least 10,000 serious oil spills occur in the United States each year. Furthermore, flushing of oil tankers plays a major role in marine pollution. Other sources, such as offshore petroleum refineries that cause oil leakage and improper disposal of used oil by private car owners and small garages, also contribute to oil pollution.
Figure 1 - Oil tankers spills: Amoco Cadiz, France, 1978 (Left) and Torrey Canyon, UK, 1967 (Right).
Sources: http://www.marineinsight.com/misc/marine-safety/the-gruesome-amoco-cadiz-oil-spill-incident/
http://www.edpashipping.com/marpol.php
http://www.itopf.com/knowledge-resources/data-statistics/statistics/
Information on previous spill incidents at sea (around the world) involving HNS can be found in an online database elaborated in the framework of the project ARCOPOLplus and respective article:
A document entitled "Marine litter - trash that kills" is provided to understand the problem of marine debris:
