Quantifying toxic contaminants in four major dump sites of Thabo Mofutsanyane district, Eastern Free State

[摘要] The large number of cases of groundwater pollution at landfills and the substantial resourcesspent on remediation suggests that landfill leachate is a significant source of pollutants,especially when considering different kinds o f contaminants in landfill leachates. The longtermeffect of the geological barrier beneath municipal-waste landfills is a critical issue forsoil and groundwater protection. Soil to plant transfer of trace metals is the major pathway ofhuman exposure to metal contaminations. Therefore, the present study was conducted todetermine trace meta l levels such as arsenic (As), cadmium (Cd), chromium (Cr), copper(Cu), manganese (Mn), lead (Pb), mercury (Hg), nickel (Ni), selenium (Se), cobalt (Co) andzinc (Zn) in soil and plant samples collected from four major dumpsites in ThaboMofutsanyane District, Eastern Free State in South Africa. Samples (soil and plants) werecollected from Harrismith, Qwaqwa and Bethlehem from two different landfills. Soil sampleswere collected at a depth of 0-15 cm from each part and pooled to form a composite sample.Plant samples were pulled from the soil together with their roots using an ager. Four aciddigest techniques (HCl, HN03, HCl04 and HF) were used and inductively coupled plasmaoptical emission spectrometry (ICP-OES) determined the concentrations of heavy meta ls.During the four seasons (spring, summer, autumn and winter), the concentration of Zn washigher in summer with value o f 3076.56± 12.02 compared to winter 1733.5 1 ±39.33. Theconcentration of Pb was within the threshold except in Qwaqwa and Bethlehem site A withvalues of 3 15.79±30.26 and 230.82±35.24. Cd concentration fluctuates during the seasons butthe highest value of 6. 15±0.06 was recorded during winter. The level of Mn in all dumpsiteswas very unstable and above the standard permissible limit. The common plants identified inthe dumpsites are Cosmos species, Eragrostis plana, Elusine indica, and were all found tocontain high level of heavy metals. Principal Correlation Analysis (PCA) analysis showedthat Qwaqwa and Harrismith had the highest load of heavy metals and the dendrogramconfirmed the similarity in metal distributions in the dumpsites. This study highlightsenvironmental implications of heavy and trace metals in all dumpsites studied. There was nosignificant difference in the concentration of metals within and outside the dumpsites whichconfirms metals can be distributed above I0 m range. All the trace metals analysed in thisstudy had higher concentrations above the permitted limits set by USEPA and WHO. Thisstudy revealed the levels and impacts of heavy metal concentrations on the dumpsites, as wellas the risks they may pose to near or far surroundings and its attendant health implications.

[发布机构] University of the Free State