The present study is conducted in the scenario of the tannery waste hazards in Kasur district of Pakistan where the tannery industry is considered as major cause of groundwater quality deterioration, Area focused in t...The present study is conducted in the scenario of the tannery waste hazards in Kasur district of Pakistan where the tannery industry is considered as major cause of groundwater quality deterioration, Area focused in this research constitutes the surroundings of the effluent carrying drains near tannery units. This study includes soil explorations, groundwater monitoring and wastewater analysis in the research area so as to find out the contamination extent of chromium in subsurface. Initial groundwater monitoring exhibited chromium concentrations as high as 90 mg/L in the tannery area. Even groundwater sampling from monitoring wells installed in the adjacent areas of effluent carrying drains, showed concentrations up to 10.4 mg/L. Wastewater analysis of all the drains in the research area has evidenced potential risk of contaminant seepage into soil and groundwater as level of chromium in wastewater samples has reported to be immensely high and varies from 68 mg/L to 2,152 mg/L. However the 30 soil samples collected from two soil bores did not show any significant results as the maximum values obtained for hexavalent chromium for leaching and retained in soil are 0.02 mg/L and 8.1 mg/kg, respectively. These low concentrations of soil samples suggest that the soil contamination may not be a main environmental issue in the areas adjacent to the effluent carrying drains, The research concludes as possibility of direct interference of the tannery wastewater with groundwater through damaged structures and sewers.展开更多
Dissolved organic nitrogen （DON） in soils has recently gained increasing interest because it may be both a direct N source for plants and the dominant available N form in nutrient-poor soils, however, its prevalence...Dissolved organic nitrogen （DON） in soils has recently gained increasing interest because it may be both a direct N source for plants and the dominant available N form in nutrient-poor soils, however, its prevalence in Mediterranean ecosystems remains unclear. The aims of this study were to i） estimate soil DON in a wide set of Mediterranean ecosystems and compare this levels with those for other ecosystems; ii） describe temporal changes in DON and dissolved inorganic nitrogen （DIN） forms （NH＋ and NO3）, and characterize spatial heterogeneity within plant communities; and iii） study the relative proportion of soil DON and DIN forms as a test of Schimel and Bennett＇s hypothesis that the prevalence of different N forms follows a gradient of nutrient availability. The study was carried out in eleven plant communities chosen to represent a wide spectrum of Mediterranean vegetation types, ranging from early to late successional status. DON concentrations in the studied Mediterranean plant communities （0-18.2 mg N kg-1） were consistently lower than those found in the literature for other ecosystems. We found high temporal and spatial variability in soil DON for all plant communities. As predicted by the Schimel and Bennett model for nutrient-poor ecosystems, DON dominance over ammonium and nitrate was observed for most plant communities in winter and spring soil samples. However, mineral-N dominated over DON in summer and autumn. Thus, soil water content may have an important effect on DON versus mineral N dominance in Mediterranean ecosystems展开更多
文摘The present study is conducted in the scenario of the tannery waste hazards in Kasur district of Pakistan where the tannery industry is considered as major cause of groundwater quality deterioration, Area focused in this research constitutes the surroundings of the effluent carrying drains near tannery units. This study includes soil explorations, groundwater monitoring and wastewater analysis in the research area so as to find out the contamination extent of chromium in subsurface. Initial groundwater monitoring exhibited chromium concentrations as high as 90 mg/L in the tannery area. Even groundwater sampling from monitoring wells installed in the adjacent areas of effluent carrying drains, showed concentrations up to 10.4 mg/L. Wastewater analysis of all the drains in the research area has evidenced potential risk of contaminant seepage into soil and groundwater as level of chromium in wastewater samples has reported to be immensely high and varies from 68 mg/L to 2,152 mg/L. However the 30 soil samples collected from two soil bores did not show any significant results as the maximum values obtained for hexavalent chromium for leaching and retained in soil are 0.02 mg/L and 8.1 mg/kg, respectively. These low concentrations of soil samples suggest that the soil contamination may not be a main environmental issue in the areas adjacent to the effluent carrying drains, The research concludes as possibility of direct interference of the tannery wastewater with groundwater through damaged structures and sewers.
基金Supported by the Ministerio Espanol de Ciencia e Innovacio'n of the Spanish government (Nos.REN2003-08620-C02-01 and CGL2006-13665-C02-01)
文摘Dissolved organic nitrogen （DON） in soils has recently gained increasing interest because it may be both a direct N source for plants and the dominant available N form in nutrient-poor soils, however, its prevalence in Mediterranean ecosystems remains unclear. The aims of this study were to i） estimate soil DON in a wide set of Mediterranean ecosystems and compare this levels with those for other ecosystems; ii） describe temporal changes in DON and dissolved inorganic nitrogen （DIN） forms （NH＋ and NO3）, and characterize spatial heterogeneity within plant communities; and iii） study the relative proportion of soil DON and DIN forms as a test of Schimel and Bennett＇s hypothesis that the prevalence of different N forms follows a gradient of nutrient availability. The study was carried out in eleven plant communities chosen to represent a wide spectrum of Mediterranean vegetation types, ranging from early to late successional status. DON concentrations in the studied Mediterranean plant communities （0-18.2 mg N kg-1） were consistently lower than those found in the literature for other ecosystems. We found high temporal and spatial variability in soil DON for all plant communities. As predicted by the Schimel and Bennett model for nutrient-poor ecosystems, DON dominance over ammonium and nitrate was observed for most plant communities in winter and spring soil samples. However, mineral-N dominated over DON in summer and autumn. Thus, soil water content may have an important effect on DON versus mineral N dominance in Mediterranean ecosystems
