சுற்றுச்சூழல் பகுப்பாய்வு வேதியியல் இதழ்

Groundwater contamination is an important issue due to its toxicological effects on ecosystems and impact on public health. In this view, 120 water samples collected from flood affected areas of district Rajanpur, Pakistan were assessed for physical parameters (colour, odour, pH, turbidity and conductivity), minerals (Alkalinity, Na+, K+, Ca+2, Mg+2, Cl-, SO4 -2 and TDS), micronutrients (F-, As, Fe, Mn, Zn) and microbiological organism (total coliform and faecal coliform) to understand its suitability for human consumption and health risk associated. Analysis data revealed that 75 and 57% water samples were contaminated with total coliform and faecal coliform bacteria respectively. Other than this, a number of water samples were having high level of minerals, micronutrients and other chemical constituents. Health risk assessment due to high concentration of Fe, Mn, As and Zn was carried out by calculating chronic daily intake (CDI) and health risk index (HRI) for both adults and children separately. Calculated CDIs and HRIs were found in the order of Mn>As>Zn>Fe and As>Mn>Zn>Fe respectively. Results showed that HRI>1 for As in 46 and 37% water samples for children and adults respectively, posing serious threats to the healthy life of the local community.

Hydroxyl radicals (HO•) formation during the ligand stabilized iron redox cycling was investigated in synthetic media, expended algal growth media (Talaquil) and field collected fresh water. HO• were selectively reacted in situ with terephthalic acid producing hydroxyterephthalic acid, quantified by fluorescence. FeIIIEDTA, photoreactive in dim light, was used as a control to compare how media components influence HO• formation rates. Since HO• is highly reactive, transformation depends on to the number of reactive atoms in a media component. Protoporphyrin IX accelerated HO• formation 20-fold, providing a good model for studying rate accelerating components of algae excretion. The results show that HO• production under usual algal test and natural fresh water conditions differ, the latter being more toxic. They enable more reliably comparison between natural waters and artificial test systems, suggesting more realistic conditions for testing toxicity.

Zeolite samples were collected from Wadkawly in Gadarif region. These samples were characterized with respect chemical properties by AAS, SEM and X-ray Diffraction Analysis (XRD) showed these samples to be composed of Thomsonite zeolite, exclusively. The sample was treated with strong brine solution to ensure that Na-zeolite was generated and used as the stationary ion exchanger phase. Solutions containing 100 ppm of heavy metal ions (Pb2+, Fe3+and Ni2+) were artificially prepared and then processed with Na-zeolite. Excellent extraction was achieved, with final residual concentration of 0.02 ppb, 3.0 ppb and 1.38 ppm for (Pb2+, Fe3+ and Ni2+) respectively and retention time 180 seconds for decreasing concentrations. This gives extraction efficiency of ~ 100%, 99.9%, and 98.6%, for Pb2+, Fe3+ and Ni2+, respectively. The relative efficiency is, therefore: Pb2+ > Fe3+ > Ni2+.

A hydride generation coupled to atomic absorption spectroscopy HGAAS method is presented for the determination of Selenium content in soil samples, alfalfa, animal feed, and water samples. The selenium distribution was studied in various locations in Zawia city. The studied areas were divided to seven different zones. The samples were digested in a mixture of mineral acid (HNO3, HCL, HCLO4 and H2O2). The Selenium element in acidified sample solution was reduced directly by treating it with Sodium borohydride (NaBH4), the metal hydride was introduced to the atomizer of AAS by inert carrier gas (N2, He). The instrument used for the generation of hydride was home built in the analytical lab and a batch method was implemented. The analytical parameters were optimized throughout the analytical procedure to give typical sensitivity (0.0055 pg/g). The Atomic Absorbance profile was recorded for all measured samples; the obtained signal profiles show smooth peaks. The Absorption value at the peak height was used as a basis for the analytical calculations. A calibration curve of standard selenium concentrations against absorbance was plotted and used to determine the selenium concentration in each sample. Soil samples were analysed by (HGAAS) for determination of concentration of selenium results are reported for all the studied zones, some zones did not exceeded the reported critical toxicity values (1.0-5.0 pg/g), but another zones are relativity high (5.6-5.9 pg/g). The Selenium content in alfalfa from different zones are relatively low in the range of (0.7 to2.20 pg/g). Concentrations of selenium in some animal feed samples are relatively low and showing deficiencies (0.62-0.71 pg/ g), but other samples are relatively high and were close to the lower limits for high dose (1.41-1.98 ng/g).

Forest fires are generally consciously or unconsciously the work of man for various reasons. Fires generated by voltaic arc between power lines and the underlying trees do not occur often. These few cases may be only demonstrated by analyzing around the site where the arc may have been generated. Material such as leaves, bark and soil can be analyzed to find the metallic residues from the fused cables. The electrical cables usually composed of aluminum or copper alloys, when involved in an electric arc may spray fused micro-drops of metals, increasing the natural level of such elements. In two cases, the Al and Cu concentrations were increased by between 2.56 to 13.9 times the background levels. Electron microscopy of leaf surfaces has identified some profound alterations produced by the intense heat of the electrical discharge.

The particularly high rate of urbanization in Kinshasa is associated with environmental degradation, such as air pollution. However, little documented information exists on the nature and extent of this pollution. In the present study, Atmospheric samples of ambient air were collected in Kinshasa for 4 months (July to October, 2009) and analyzed for As, Cd, Pb and Ni using ICP - MS. The ranges of heavy metal concentrations for the 24-h ambient air samples in roadside sites (residential sites) were 0.9-6.0 ng/m3 (0.4-2.8 ng/m3), 2.5-5.9 ng/m3 (1.2-3.5 ng/m3), 166.2-1422.5 ng/m3 (72.0-1685.0 ng/m3), 48.7-482.0 ng/m3 (42.0-117.6 ng/m3) for As, Cd, Pb and Ni, respectively. Current 24-h average levels of all of them show higher levels than those measured in Europe. Toxicologically relevant elements reach levels of public health concern. The Efforts should be made to reduce the levels of metal contamination.