Transport of Trace Metals by the Rainwater Runoff in the Urban Catchment of Guwahati, India - Management of Natural Resources in a Changing Environment - page 216

Fig. 1 Sampling location of Guwahati

and Zn were analysed by Atomic Absorption Spectrometer (PerkinElmer AAnalyst
200) using three standards calibration curve.

Results and Discussion

Acidity-Basicity of the Runoff

The pH of the runoff samples ranges from 4.6 to 7.9, where J19 sample showed the
minimum and Z5 showed the maximum values. The variation patterns of the pH
were different for each of the seven locations and these are presented in Fig. 2 .
pH had different diurnal trends from one event to another. In location J, the pH
was in the range of 4.6-7.6 with a mean value 6.5. The pH decreased diurnally in
four of the seven events namely I, III, IV and VI, but in two of the events, II and V,
there was an increasing trend and lastly in the event VII no specifi c trend was
observed. Three of the runoff samples (J3, J19 and J20) had pH less than the pH of
natural rainwater (i.e. 5.6) and this might be due to contamination from the soil over
which the runoff was fl owing. Intrusion of nitrates and sulphates from the soil in the
form of acids was possible. The rest of the runoff samples possessed pH greater than