Aa 6800 spectrometer

Soil metal contents were determined by atomic absorption spectrometry (AAS) with a SHIMADZU AA-6800 spectrometer (Shimadzu, Tokyo, Japan) using the aqua regia di-gestion. The entire soil sample was dried, ground to a fine powder, and sieved through a 100 μm sieve [102 (link)]. This was undertaken in order to have a homogeneous soil sample so that the entire soil sample is subjected to the mineralization process and because it is known that grinding increases the specific surface area, i.e., an improvement of the soil/extraction solution contact surface occurs. Three grammes of soil were weighed into a beaker, to which 7 mL of HCl and 21 mL of HNO₃ were added. After 3 h of mineralization, the supernatant was filtered through a 0.45 μm pore size filter into a 100 mL volumetric flask, filled to the mark with distilled water, and then subjected to heavy metal analysis by AAS. Investigations were carried out under constant conditions of temperature, actual air humidity, and ventilation: T = (27 ± 1) °C and RH = (65 ± 2)%, without forced ventilation of ambient air.
In order to determine the degree of soil pollution, the results obtained were compared with the values established in Order 756/1997 [13 ] concerning normal values, alert threshold values, and intervention threshold values (Table 1).

Characterization of the soil samples was carried out in terms of pH, texture, structure and content of metals (Cu, Pb, Cr and Ni). Soil pH was determined in soil/water extract 1/5 (w/v) using a HANNA pH meter. Soil texture was determined by gravimetric method with RETSCH AS 200 sieve and soil structure was determined by Sekera method. Soil metal content was determined by atomic absorption spectrometry (AAS) with a SHIMADZU AA-6800 spectrometer (Shimadzu, Tokyo, Japan) using the aqua regia digestion. The soil samples were dried, grounded to a fine powder and sieved through a 100 μm sieve. Three grams of each sample of soil were weighed into a beaker and 7 mL of HCl and 21 mL of HNO₃ were added. The mixture was then refluxed for 2 h. After cooling to room temperature, the supernatant was filtered and diluted to 100 mL.