Precipitation Chemistry of the Rivers State University of Science and Technology (RSUST) campus Air Shed, Port Harcourt, Nigeria

Abstract

Event precipitation study was carried out at three sites (the Institute of Pollution Studies Laboratory ambient environment, Eagle Island and Stadium Road environs) with the following parameters analyzed pH, Conductivity, Turbidity, Cl , S04 , N03 , Alkalinity, NH4 + using World Meteorological Organization protocols and Standard Methods for water and wastewater protocol (WMO, 1988 and APHA, 1995). The rain water pH was 6.46 obtained at only one station. Oxidation Reduction Potential (ORP) ranged from +29 to +126 mV for campus, +65 to +70 mV for Stadium Road and +126.0 mV for Eagle Island Station. The temperature ranged from 24.6 29.6 0 C across all stations. The Conductivity varied from 3.83 – 29.4 μS/cm on Campus, 5.2 – 22.2 μS/cm at Stadium road and 10.95 μS/cm at Eagle Island. Salinity ranged from <0.01 – 0.01 ‰ at all sites except Eagle Island where levels were not detected. Total dissolved solids ranged from 1.63 – 18.7 mg/l on Campus, 2.6 – 13.9 mg/l at Stadium Road and 6.34 mg/l at Eagle Island. Dissolved Oxygen ranged from 5.7 – 7.3 mg/l within the campus air shed, while at Stadium air basin, it was 6.5 mg/l. There was no data for Eagle Island. The Chloride values ranged from not detectable (<1.0) to 1.4 mg/l on campus, not detectable in Eagle Island and Stadium road environs. Sulphate and Phosphates were not detected being less than 1.0 mg/l and 0.05 mg/l respectively. Nitrate levels varied from 0.23 – 1.1 mg/l on Campus air basin whereas Stadium Road and Eagle Island had 0.31 and 0.41 mg/l respectively. Ammonia concentration ranged from <0.02 – 0.90 mg/l in campus air basin whereas Stadium Road and Eagle Island had 0.21 and 0.09 mg/l respectively. Total Hardness ranged from <0.2 – 5.8 mg/l on campus air basin, while it was <0.2 mg/l in Eagle Island. Alkalinity ranged from 8.0 – 12.0 mg/l on Campus air basin while at Eagle Island, it was 12.0 mg/l. Calcium concentration varied from <0.08 – 1.2 mg/l in campus air basin while in others; it was less than 0.08 mg/l. Magnesium ranged from <0.05 0.7 mg/l and less than < 0.05 mg/l in the other two air basins. Correlation Analysis showed strong and positive relationships between Total Alkalinity and Nitrate, Chloride and Nitrate, Nitrate and Calcium, Nitrate and Magnesium. pH only correlated negatively with Oxidation Reduction Potential (ORP). Apart from Nitrate, Ammonium ion and Total Alkalinity, all the other ions had either a negative or positive correlation with Temperature. Ammonia did not correlate with any ion. The results from the precipitation studies showed that the rain water quality on Campus is Alkaline (pH 6.46). The study did not show any contribution from anthropogenic sources as sulphates were not detected. The results of the rain event samples showed that natural sources (soil minerals) are the main contributors to rain chemistry. The study is significant in that it has provided information on the state of the chemical composition of rainfall, the pH status of rain water and the need for further study.