Arsenic and major cation hydrogeochemistry of the Central Victorian (Australia) surface waters.
This paper reports on the major cations (Ca, Mg, Na and K) and arsenic (As) compositions of surface waters collected from major creeks, rivers and lakes in Central Victoria (Australia). The surface waters were found to be neutral to alkaline (pH 6.7-9.4), oxidised (average redox potential (Eh) about 130 mV) and showed variable concentrations of dissolved ions (EC, about 51-4386 microS/cm). The concentrations of dissolved major cations in surface waters were found to be in the order of Na>>Mg>Ca>K and in soils the contents of metals followed an order of abundance as: Ca>Mg>>K>Na. While Na was the least abundant in soils, it registered the highest dissolved cation in surface waters. Of the four major cations, the average concentration of Na (98.7 mg/L) was attributed to the weathering of feldspars and atmospheric input. Relatively highly dissolved concentrations of Na and Mg compared with the world average values of rivers reflected the weathering of rock and soil minerals within the catchments. The As soil level is naturally high (linked to lithology) as reflected by high background soil values and mining operations are also considered to be a contributory factor. Under relatively alkaline-oxidative conditions low mobility of dissolved As (average about 7.9 microg/L) was observed in most of the surface waters with a few higher values (> 15 microg/L) around a sewage disposal site and mine tailings. Arsenic in soils is slowly released into water under alkaline and/or lower Eh conditions. The efficient sink of Fe, Al and Mn oxides acts as a barrier against the As release under near neutral-oxidising conditions. High As content (average about 28.3 mg/kg) in soils was found to be associated with Fe-hydroxides as revealed by XRD and SEM analysis. The dissolved As concentration was found to be below the recommended maximum levels for recreational water in all surface waters (lakes and rivers) in the study area. Catchment lithology exerted the fundamental control on surface water chemistry. Sites impacted by mining waste dumps showed a decline in water quality.
Sultan
Khawar
K
School of Science and Engineering, University of Ballarat, Mount Helen, University Drive, Ballarat, Victoria 3353, Australia. khawarsultan@students.ballarat.edu.au
Dowling
Kim
K
D001151:Arsenic / Q000737:chemistry*; D002412:Cations; D008855:Microscopy, Electron, Scanning; D012989:Soil Pollutants / Q000737:chemistry; D014739:Victoria; D014874:Water Pollutants, Chemical / Q000737:chemistry*
D002412:Cations; D012989:Soil Pollutants; D014874:Water Pollutants, Chemical; D001151:Arsenic