Assessments of infiltration rate and effects on water quality of selected infiltration media for use in storm water run off in Karachi, Pakistan

摘要

Infiltration experiments were undertaken to establish the suitability of soil type in terms of infiltration rates among the various soil, and to investigate the potential effects of the infiltration media on the water quality by the stormwater runoff. In all from thirty three sampling points, five different types of soil have been classified on the basis of composition of sand, silt and gravel and tested on small scale to get a preliminary estimate regarding their suitability as infiltration media. Water quality tests are conducted on stormwater to assess the effects of the medium. Soil samples from various soil types were taken prior to and after infiltration of storm water runoff. The samples were tested for trace metals (Pb, Cu, Cd, and Zn) and for major ions (Ca, Mg, Na and K). The result shows that there is a decline in the concentration of all the metals studied during and after infiltration of stormwater runoff. It suggest that presence of sand, silt and gravel and the absence of clay particles in the effluent is responsible for declining effect of cations as the leaching of soil has not occurred. Therefore the declining effects of cations are significant in all the soil types.