Monitoring of rainwater quality in Kandy and Peradeniya, Sri Lanka.

The composition of atmospheric deposition is a measure of air quality, an important aspect of the health of the ecosystem. Consequently, continuous monitoring of atmospheric deposition is crucial to obtain remedial measures to avoid undesirable aspects that would affect living things. In this context, the objective of this study was to determine the rainwater quality at selected locations in Kandy and Peradeniya area of Sri Lanka, namely, Kandy, Polgolla, and University of Peradeniya (UOP), and to identify possible correlations between quality parameters through statistical means. Forty (40) rainwater samples from the UOP site and seven (07) samples each from the Kandy and Polgolla sites were collected from 18 May 2020 to 28 April 2021. The volume-weighted average (VWA) pH values of UOP, Kandy, and Polgolla sites were determined to be 7.44, 7.19, and 7.19, respectively, and moreover, acid rain (pH < 5.6) occurrences were not detected during the sampling period. The VWA values of rainfall, conductivity, salinity, TDS, and hardness at the UOP site were 40.12 mm, 51.93 µS cm-1, 0.0300 ppt, 26.59 mg L-1, and 13.55 mg L-1, respectively. The corresponding values of the Kandy site were 16.52 mm, 64.04 µS cm-1, 0.0361 ppt, 30.80 mg L-1, and 19.49 mg L-1, respectively; and those of the Polgolla site were 33.10 mm, 53.90 µS cm-1, 0.0310 ppt, 25.76 mg L-1, and 19.31 mg L-1, respectively. The VWA values of conductivity, salinity, and TDS were the highest at the Kandy site. Further, the VWA values of hardness at Kandy and Polgolla sites were approximately equal, probably due to the spring of Ca2+ and Mg2+ particulates from the dolomite quarry located in Digana area. The most prominent anion was identified as Cl- in bulk deposition at all three sites, while NO3- showed the lowest concentration of all sites. Moreover, very strong significant positive correlations were identified between conductivity-TDS, conductivity-salinity, conductivity-hardness, TDS-hardness, TDS-salinity, salinity-hardness, SO42--Cl-, and NO3--Cl- according to the relevant Pearson correlation coefficients. It is thus concluded that the pollutants come from the same sources, either natural or anthropogenic.

Chemical characteristics of wet precipitation at Peradeniya in Sri Lanka.

The purpose of this research was to study chemical characteristics of precipitation in Peradeniya (Latitude 6.973701, Longitude 79.915256), Kandy District in Sri Lanka. This study was conducted during 2012 to 2014, and wet precipitation was analyzed for pH, conductivity, Na+, NH4+, K+, Mg2+, Ca2+, F-, Cl-, NO3-, SO42-, Pb, Cu, Mn, Al, Zn, and Fe for a total of 125 samples. Less than 2% events of acidic precipitation were recorded, and the VWA of the major ionic species present in precipitation samples were in the order of Ca2+ > Na+ > Cl- > NH4+ > SO42- > K+ > NO3- > Mg2+. Neutralization of acidity of precipitation is much more related to CaCO3 than NH3, and the presence of high content of Ca2+ strongly supports this fact. When considering marine contribution, SO42-/Na+, Ca2+/Na+, Mg2+/Na+, and K+/Na+ ratios are higher than the reference value suggesting that contribution of sources other than marine. Concentration of Zn is the highest while that of Mn is the lowest. Principal component analysis identified probable sources for major ionic and elemental sources as both natural and anthropogenic sources such as vehicular emission due to heavy traffic, waste incineration, bio mass burning, brass industry, and construction.

Atmospheric chemical composition of bulk deposition at two geographically distinct locations in Sri Lanka.

This study presented the research work carried out for the investigation of chemical composition of bulk precipitation in two geographically and economically distinct areas, namely Gampaha and Kandy Districts. This study was conducted from 2013 to 2014 at three sampling stations in each District. The bulk precipitation was analyzed for pH, conductivity, Na+, NH4+, K+, Mg2+, Ca2+, F-, Cl-, NO3-, SO42-, Pb, Cu, Mn, Al, Zn and Fe for a total of 375 samples. Only 8% events of acidic precipitation were recorded in Gampaha District when compared with 3% in Kandy District. The volume weighted average concentrations of the major ionic species present in precipitation samples were in the order of Na+ > Ca2+ > Cl- > NH4+ > SO42- > Mg2+ > NO3- > K+ > F- in the Gampaha stations, while the order was NH4+ > Ca2+ > Na+ > Cl- > SO42- > Mg2+ > NO3- > K+ > F- in Kandy District. Neutralization of acidity of precipitation is much more related to CaCO3 than NH3, and high content of Ca2+ ions present in both Districts strongly supports this fact. When considering marine contribution, SO42-/Na+, Ca2+/Na+ and Mg2+/Na+ ratios are higher than the reference value suggesting contribution of sources other than marine. Depositions of both Districts show that the concentration of Al is the highest while that of Mn is the lowest. Principal component analysis suggests that influencing human activities on chemical composition of rain water depends on thermal power plant, oil refinery, heavy traffic and waste incineration in the study area.

Sodium hydroxide modified rice husk for enhanced removal of copper ions.

Although rice husk (RH) is a readily available, natural, heavy metal adsorbent, adsorption capacity in its natural form is insufficient for certain heavy metal ions. In this context, the study is based on enhancement of the adsorption capacity of RH for Cu(II). NaOH modified rice husk (SRH) shows higher extent of removal for Cu(II) ions than that of heated rice husk (HRH) and HNO3 modified rice husk (NRH). The extent of removal of SRH is increased with the concentration of NaOH, and the optimum NaOH concentration is 0.2 mol dm-3, used to modify rice husk for further studies. The surface area of SRH is 215 m2 g-1, which is twice as much as that of HRH according to previous studies. The sorption of Cu(II) on SRH obeys the Langmuir adsorption model, leading to the maximum adsorption capacity of 1.19 × 104 mg kg-1. Kinetics studies show that the interaction of Cu(II) with SRH obeys pseudo second order kinetics. The X-ray fluorescence spectroscopy confirms the adsorption of Cu(II) on SRH, while desorption studies confirm that Cu(II) adsorbed on SRH does not leach it back to water under normal conditions.