Short-Term Biochemical Impacts in <i>Cyphoderus javanus</i> Borner (Collembola) as Potential Biomarkers of Fly Ash and Heavy Metal Pollution in Tropical Lateritic Soil

Abstract

The detritivorous soil microarthropods are ideal models for environmental health assessment, but only scant information is available on their biomarker potentials against xenobiotics in the tropical edaphic conditions. This microcosm study has estimated short-term biochemical changes with respect to tissue nutrient levels and digestive enzyme activities in a near cosmopolitan Collembola Cyphoderus javanus Borner exposed to coal fly ash amended lateritic cropland soil (5% and 20% w/w i.e. 50 or 200 t•ha − 1 ), and cadmium sulphate (200 mg/kg soil)/lead acetate (200 mg/kg soil) treated sterile river sand. The levels of total tissue carbohydrates, proteins, free amino acids, and lipids decrease within 7 days in the specimens of fly ash (P < 0.001) and heavy metals treated sets. The α-amylase, cellulase and protease activities are also down regulated by fly ash and heavy metals (P < 0.05). It is also observed the enzyme: protein ratios increase in fly ash treated sets and decrease in lead and cadmium treated specimens. Specimens in treated sets accumulate high levels of lead and cadmium within 15 days, which decrease subsequently probably due to elimination through frequent moulting. These short-term biochemical effects in Collembola have applied importance in C. javanus, as biomarkers for quick ecotoxicological assessments in the tropical agricultural soils.The overload of anthropogenic waste materials can produce long-term ecological hazards in soil ecosystems. However, this serious problem is often overlooked, and emphasis is given on the permissible levels of harmful chemicals in the environment to safeguard life and welfare of humans, higher animals and crop plants. On the other hand, accumulation of xenobiotics in soil is deleterious to a wide range of organisms and their ecological functions. Major sources of soil pollution are the overburdens of mines, industrial wastes, urban waste, sewage sludge, inorganic fertilizers and synthetic pesticides. An example is fly ash, a solid waste generated by coal-fired thermal power plants all over the world. In India, fly ash is used in agricultural fields for soil conditioning, nutrient enrichment, and promotion of crop growth and yield. It is a ferro-alumino-silicate mineral occurring as fine particles and is mostly alkaline in reaction. On an average 95% -99% of fly ash is comprised of oxides of silica, aluminium, iron, calcium, potassium, etc, and the remainder is formed of many elements including toxic heavy metals [1]. The concentration of toxic metals like cadmium, zinc, and lead in fly ash can be as high as 130 mg•kg −1 , 3500 mg•kg −1 , and 5000 mg•kg −1 , respectively [2]. Some trace elements are required for the growth of plants and animals, but heavy metals like mercury, cadmium, lead, etc. are not necessary for the growth and development of organisms. Both essential and non-essential heavy metals in high quantities and long exposure periods can be detrimental to soil flora and fauna [3]. Cadmium is an extremely toxic element due to its great solubility in wat...