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- Title
Spatial evaluation of precipitation patterns in the catchment area of Malir River during monsoon spells of 2019 through geospatial techniques.
- Authors
Haider, Syed Wasi; Kazmi, Syed Jamil Hasan; Arsalan, Muhammad; Naseem, Shahid; Kanwal, Humaira
- Abstract
The composition of the atmosphere can be predicted through air quality and rainfall chemical constituents. Hence, a detailed screening of chemical variables was carried out on 24 September 2019 around the Malir River basin in Karachi, a megapolis near the Arabian sea. Sporadic precipitation distribution patterns were observed that influence the agrarian as well as the local environment with considerable pollution. Precipitation chemistry being influenced by imprints of long-range transported pollutants, as a result, anthropogenic and natural emission varies its composition site by site. Precipitation samples were analysed for ionic species and pH, TDS/EC, turbidity and ORP/Eh. The ions occurred in alkaline solvent both in the catchment and residential zones, but spatial precipitation patterns showed acidic pH in high elevation zones of the catchment. Aerodynamics observed through air mass trajectories provide a mixed composition in collected wet deposition samples. Sea spray input is evident by the results of ionic ratios (Cl−/Na+ = 1.807), enrichment factors (EFsoil for Cl− = 708.9), sea sprays as sea salt fraction (SSF = 98.45%) with (Cl−) ion dominant followed by (Na+) > (Ca2+) > (HCO3−) > (SO42−) > (K+) > (Mg2+) > (NO3−) > (PO43−) > (H+) expressed in micro equivalent per litre. Physical parameters like pH show a mean of 6.19 ± 0.30 with a range 5.64–6.66 whilst chemical parameters responsible for acidification of precipitation like NO3− and SO42− show a mean value of 26.24 ± 25.55 and 152.83 ± 154.58 with a range 4.89–118.39 and 20.80–790.40, respectively. Geological influence in precipitation samples through wind action showed an increase in K+, Ca2+ and Mg2+ ions as well as from both anthropogenic and natural sources by means of terrestrial dust from surroundings near sampling sites. Acidic compounds are affected by alkaline species as natural acidic precipitation occurs initially in the whole study area. Percentage of anions (52%) is slightly higher than cations (48%) in the overall studied environment due to anthropogenic impact. It is concluded from the present study that pristine areas have acidic rainfall while urban sprawl have shown alkaline precipitation.
- Publication
Arabian Journal of Geosciences, 2022, Vol 15, Issue 17, p1
- ISSN
1866-7511
- Publication type
Article
- DOI
10.1007/s12517-022-10574-9