Water pollution from pesticides

Chemical pollution From a qualitative point of view, an important common issue is the excess of chemicals (fertilisers and pesticides) associated with agrarian and livestock farming diffuse sources and the point-source discharge of (treated and untreated) sewage water. Industrial point-source pollution is not addressed as a relevant issue, but it is assumed that industries operate following the legal rules and only the incomplete elimination of industrial chemicals in urban wastewater treatment plants is perceived as a problem. 

Nonylphenol ethoxylates (NPEOs) are extensively used as surfactants in industrial products (see Chap. 1). NPEOs are a mixture of polyethoxylated mono-alkylphenols, predominantly para-substituted, and are used in the manufacturing of paints, detergents, inks, and pesticides [435, 446]. Surfactants are common water pollutants because of their use in aqueous solutions, which are discharged into the environment in the form of wastewater from treatment plants or sludge stored in landfills. Degradation products of alkylphenol polyethoxylates, i. e., nonylphenol (NP), have the potential to be bioaccumulated, thereby becoming toxic to aquatic [447] and soil microorganisms [435,448]. 

The adsorption of ions on iron oxides regulates the mobility of species in various parts of the ecosystem (biota, soils, rivers, lakes, oceans) and thereby their transport betv een these parts. Examples are the uptake of plant nutrients from soil and the movement of pesticides and other pollutants from soils into aquatic systems. In such environments various ions often compete with each other for adsorption sites. Adsorption is the essential precursor of metal substitution (see Chap. 3), dissolution reactions (see Chap. 12) and many interconversions (see Chap. 14). It also has a role in the synthesis of iron oxides and in crystal growth. In industry, adsorption on iron oxides is of relevance to flotation processes, water pollution control and waste and anticorrosion treatments. 

Diazinon is released into water directly from point source discharges, from drift during pesticide applications, and from nonpoint source runoff from agricultural and urban areas. Since diazinon is not a Priority Pollutant under the Clean Water Act, it has not been evaluated extensively in water quality... 

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 a field from which pesticides and fertilizers are carried by rainwater into a river is an example of a nonpoint source. Industrial wastes probably constitute the greatest single pollution problem in soil and water. These contaminants include organic wastes such as solvents, inorganic wastes, such as chromium and many unknown chemicals. Contamination of soil and water results when by-product chemicals are not properly disposed of or conserved. In addition industrial accidents may lead to severe local contamination. For a more in-depth discussion of sources and movements of water pollutants, see Chapter 27. 

The POP pesticides are hydrophobic compounds with low water solubility. However, natural waters play an important role in the transport and transformation of POPs, because similar to air, water is capable of transporting POPs through convection to areas far from application sites, such as (1-HCH found in the Arctic. More importantly, water is essential for humans and all living species and is closely related to their activities. Aquatic mammals are the species most seriously endangered by POP pollution of natural waters. Fish and shellfish are important pathways for POPs to enter the human body through diet. Aquatic ecosystems are very influential on human beings. Therefore, water pollution by pesticides has generated wide concern. 

Luo, X.J., Mai, B.X., Yang, Q.S., Fu, J.M., Sheng, G.Y., Wang, Z.S., 2004. Polycyclic aromatic hydrocarbons (PAHs) and organochlorine pesticides in water columns from the Pearl River and the Macao harbor in the Pearl River Delta in South China. Mar. Pollut. Bull. 48(11-12), 1102-1115. 

Jury, W.A., Focht, D.D., Farmer, W.J. (1987b) Evaluation of pesticide ground water pollution potential from standard indices of soil-chemical adsorption and biodegradation. J. Environ. Qual. 16(4), 422 -28. 

Parmele, L.H. Lemon, E.R. Taylor, A.W. Micrometeorolog-ical measurement of pesticide vapor flux from bare soil and corn under field conditions. Water, Air, Soil Pollut., 1972, 1, 433. 

Because of the high and similar values of the rate constants, it is said that these free radicals react nonselectively with the organic matter present in water, although, as deduced from the above range of values, there are compounds that react with them almost three orders of magnitude faster than others. Among the most common water pollutants, phenols and some pesticides are substances that react rapidly with hydroxyl radicals, whereas some organochlorine compounds are less reactive. 

The environmental protection agencies of most countries have identified agriculture as the largest nonpoint source of surface water pollution. This is a major problem in each country. Pesticides and nitrates from fertilizers are detected in the groundwater in many agricultural regions. Soil erosion is a concern in many countries. Pest resistance to pesticides continues to grow, and the problem of pesticide residues in food has yet to be resolved. All nations are more competitive in international markets than a few years ago. 

Whenever a new well is completed, the abstracted aquifer should be studied in detail, including water table and temperature measurements and complete laboratory analysis of dissolved ions and gases, stable isotopes, and age indicators such as tritium, 14C, and 36Cl. Analysis for suspected pollutants, for example, fertilizers, pesticides, pollutants from local industries, and domestic sewage, should be carried out as well. This wealth of data is needed to provide answers to the questions raised in section 1.4. 

As you investigate the contamination of Prince Edward Island s soils with sodium arsenite from pesticides, investigate the link between the pH and solubility. For example, water polluted with sodium arsenite may be treated with lime (calcium oxide), CaO. 

---