Materials and methods
A total of 15 soil samples were collected from of the industrial complex surrounding area. Another two samples
of references were also collected from an area 10 kilometres away from the industrial complex. Soil samples were
collected from the surface of the soil (0-20 cm deep) and preserved by using the methods of soil analysis [16]. The
region was stratified into regularized grid cells of 0.1 *0.1 km, within each a sampling location was chosen
randomly. From each sampling points, five Soil samples were gathered and mixed properly to obtain a composite
sample mixture. The soil sampling spots were cleared of debris before sampling. Each composite soil samples were
placed in cellophane bags [17], labelled and was taken to the laboratory for pre-treatment and analysis. The
sampling tools were washed with soap and rinsed with distilled water after each sampling.
In the laboratory, bulk soil samples were spread on trays and were air dried at ambient conditions for two weeks.
The samples were then grounded by mortar and pestle, sieved through a 2 mm mesh, and oven-dried at 50ƕ C for
about 48 hours. The samples were then stored in polyethylene bags and re-homogenized before being used. The soil
samples were digested using the 11466, ISO standard method (the aqua regia digestion method) [ISO 11466]. 3 g of
soil was placed in a 100 ml round bottom flask with 21 ml of concentrated HCl (35%) and 7 ml concentrated HNO3
164 Abdolhossein Parizanganeh et al. / Procedia Environmental Sciences 2 (2010) 162–166
(65%). The solution was kept at room temperature overnight before a water condenser was attached and the solution
heated to boiling for 2 hours. 25 ml of water was added down the condenser before filtration of the mixture through
using a Whatman (No. 42) filter. The filtered residue was rinsed twice with 5ml of water and the solution was made
up to 100ml. All solutions were prepared with Milli-Q deionised water. The above procedure was also used to obtain
a blank and control samples and all samples were blank-corrected Concentrations of Pb, Zn, and Cd in the digested
samples was determined using Atomic absorption spectrometry (Varian, Germany). The pH and EC (solid: distilled
water=1:5) of the soil samples were also measured by with pH and EC meters (Metrohm, Germany).
4. Data processi