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Articles by Masil Khan
Total Records ( 4 ) for Masil Khan
  Masil Khan
  With the intense industrial development and with the indiscriminate use of fertiliser and pesticides, soils in most part of the world have shown elevated levels of metals concentration. There is concern that metals present above certain levels in the soil may affect agricultural production. Furthermore, metals deposition in the soil might be a potential source of their introduction into food chain. Microbial parameters appear to be useful in monitoring soil metal pollution and could provide an early warning of deteriorating soil quality. Microbial activities and processes like soil microbial respiration, microbial biomass C, metabolic quotient (qCO2), biomass N, community structure, N mineralisation, organic matter decomposition and enzymatic activities have been successfully used for studying metals effect on soil quality. This review, however, discussed the effects of soil metal pollution on microbial respiration, biomass carbon and metabolic quotient only. Short- and long-term studies and studies carried out under different environmental conditions were considered. Metals availability and toxicity differs in soil with different physicochemical properties. Effects of metals on microbial activity in soils with contrasting properties were also reviewed.
  Masil Khan , Hammad Naqi Khan and Hania Aslam
  The present study monitored the water quality of Hudiara drain using 72 water samples from three sampling points on a fortnightly basis and analysing for a range of water quality parameters. Large variations were found in almost all water quality indices with most of the lower values being observed during the monsoon season (July to September). Mean dissolved oxygen (DO) was below 1 mg L‾1 at all sampling points. Mean biochemical oxygen demand (BOD, 104-115 mg L‾1) and chemical oxygen demand (COD, 255-276 mg L‾1) values exceeded the Pakistan National Environmental Quality Standards (NEQS) for industrial effluents. Although mean total dissolved solids (TDS) and metal concentrations (Cd, Cr, Cu, Li and Pb) of the drain’s water were below the limits set for industrial effluents (NEQS), concentration of most of these indices (e.g. TDS, Cd and Cu) was above the acceptable limits of irrigation water. Between points, the TDS values were found lower at point 1 and the converse was the case for most of the metals at that point. E. coli were found above 200 MPN 100‾1 ml at all sampling points. The daily contribution of pollution load of Hudiara Drain to the River Ravi in terms of TDS, BOD and COD was 354, 45, 111 tons respectively. Prolonged use of water of the Hudiara drain for irrigation may be harmful to soils due to high TDS. Similarly, long term use of the drain’s water for irrigation may cause accumulation of Cd, Cu and Mn above the limits known to cause soil pollution. With an annual discharge of approximately 180 cusecs, Hudiara drain is one of the main causes of both chemical and biological contamination in the River Ravi. Poor water quality and stress on aquatic life in the River Ravi, especially during low flow may be largely attributed to Hudiara drain.
  Masil Khan
  Soil is home to remarkable diversity of life from microbes to moles and a well-established ecosystem among these different organisms exists. Microorganisms either independently or in association with other organisms are playing very important role in the plant nutrients recycling. Soil metal concentrations above certain limits disrupt this ecosystem and as a result plant nutrient cycling process.
Metal contamination in soils cause proportions of some groups of microorganisms to increase than the others. Compared with bacteria certain groups of fungi are less affected by soil metal pollution. Phospholipid fatty acid (PLFA) measurements in metal contaminated soils show that within bacterial population, metals are more toxic to gram-positive than gram-negative bacteria. Significant reductions in enzymatic activities occur in soils contaminated with metals and generally metals are more toxic to intra-cellular enzyme activities (e.g. dehydrogenase) than extra-cellular activities (e.g. phosphatase). Similarly, enzymes produced by bacteria are more affected by metal contamination than those produced by fungi. Organic matter decomposition and nitrogen mineralisation, which are carried out by various groups of microorganisms can also be affected by increased metal concentrations in the soils.
  Masil Khan and John Scullion
  Three experiments were conducted on a slightly acidic, grassland clay loam amended with sewage sludge contaminated with Cu, Ni and Zn in different combinations (Cu-Ni, Ni-Zn and Cu-Zn). Metals were added to a low metal sludge at two levels, above and below current limits. The effects of these metals on microbial indices were studied over a 7-week laboratory incubation. Zn inputs had few effects on microbial indices. In contrast, Cu and Ni decreased CO2 evolution at one week of incubation and led to an increase later. Biomass C was lower in high Cu and Ni soils whereas biomass N was lower in all three high metal treatments and there was evidence of a shift from bacterial to fungal biomass. Greater CO2 evolution rates in the high metal soils appeared to be a response to increased stress on microorganisms. Zn seemed to be less toxic than Cu and Ni when applied at rates close to EC limits for sludge treated soil (DoE, 1999).
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