Environmental pollution: the case of Xenobiotics


Xenobiotics are chemical substances that are foreign to the biological system. They include naturally occurring compounds, drugs, and environmental agents (Mondofacto online medical dictionary at www.mondofacto.com).The classes of xenobiotics include: pesticides, polyaromatic hydrocarbons (PAHs), polychlorinated aromatics, solvents, hydrocarbons, and others (surfactants, silicones, and plastics).

Xenobiotics levels in soils are generally low (less than 100 ppm) unless they are concentrated by application as in the case of pesticides, by spills or by waste disposal. They can occur in soils in solid, dissolved and gaseous phases and all undergo microbial and abiotic (chemical) transformations (Logan, 2000).
Photo source: www.cleanwaterfund.com


Pesticides are the most important xenobiotic pollutants because of their widespread use in agriculture. In many developing countries, unregulated use of pesticides by poor farmers contributes not only to environmental pollution but to health problems as well.

In the soil, pesticides can be temporarily fixed through adsorption by soil particles. The persistence or decomposition of pesticides in the soil is influenced by soil moisture, organic matter content, redox potential, soil acidity, soil temperature, texture, adsorption potential and clay minerals (Schactschabel et al., 1998; Sonon and Schwab, 2004).

References

Logan, T.J. 2000. Soils and environmental quality. In: Handbook of Soil Science (M.E. Sumner, ed.). CRC Press, Boca Raton, pp: G155-G169.

Schactschabel P., H.P. Blume, G. Brümmer, K.H. Hartge and U. Schwertmann. 1998. Lehrbuch der Bodenkunde (14th ed.). Ferdinand Enke Verlag, Stuttgart.

Sonon, L.S. and P.A. Scwab. 2004. Transport and persistence of nitrate, atrazine and alachlor in large intact soil columns under two levels of moisture contents. Soil Science 169: 541-553.


Comments

Post a Comment

Popular posts from this blog

Tropical soils: some important aspects of these less understood soils

Image
Tropical regions occur between the Tropic of Cancer and the Tropic of Capricorn. The tropics include approximately 40% of the land surface and is the largest ecozone of the earth. According to Köppen (1931), the tropics are characterized by an annual mean air temperature above 18°C through­out the whole year. The largest climatic variation is introduced by the variability of precipita­tion, reaching from nearly 0 mm in the Saharan and Atacama Desert to 11,700 mm on Mt. Waialeala in Hawaii (Eswaran et al., 1992). An Afisol (Luvisol) soil derived from mudstone in Eastern Samar, Philippines According to Uehara and Gillman  (1981), "t ropical soils" is a common name used to identify any soil that occurs in the tropics. They noted that like most common names, the term lacks precision, but it is more readily understood by a larger audience than are the scientific names. In contrast, Sanchez (1976) argued against the use of the term "tropical soils" since it does not accur
Read more

The causes of the Guinsaugon landslide

Image
On 17 February 2006, a catastrophic landslide buried the village of Guinsaugon, the second largest village of St. Bernard town (Southern Leyte, Philippines) killing more than a thousand residents and displacing approximately 19,000 people. The landslide originated on an approximately 800 m high escarpment produced by the Philippine Fault that bisects Leyte and the major islands of the Philippines. In a recent article which synthesized the papers presented during an international conference in Leyte 2008 and published in the international journal Bulletin of Engineering Geology and the Environment, Guthrie and co-workers (2009) arrived at the following conclusions: "The approximately 15 million m3 landslide was a result of progressive failures and tectonic weakening in a region made especially vulnerable by the inter-reaction of geological/tectonic, climatic and cultural factors. In southern Leyte, geology and tectonics (including historical seismicity, the progressive disintegr
Read more