To determine the concentration of nickel in a given soil sample using atomic absorption spectroscopy AAS , follow these steps:1. Sample collection and preparation: a. Collect a representative soil sample from the area of interest. b. Dry the soil sample in an oven at 105C for 24 hours to remove moisture. c. After cooling, sieve the sample through a 2 mm mesh to remove stones and debris. d. Grind the sieved sample to a fine powder using a mortar and pestle or a ball mill.2. Digestion of the soil sample: a. Weigh approximately 0.5 g of the powdered soil sample and transfer it to a digestion tube or flask. b. Add 10 mL of concentrated nitric acid HNO3 and 2 mL of concentrated hydrochloric acid HCl to the sample. This mixture is also known as aqua regia. c. Heat the digestion tube or flask on a hot plate or in a microwave digestion system until the sample is completely digested. The solution should be clear or slightly colored. d. Allow the digested sample to cool, then filter it through a Whatman filter paper into a 50 mL volumetric flask. e. Rinse the digestion tube or flask with deionized water to ensure complete transfer of the digested sample. Add deionized water to the volumetric flask up to the 50 mL mark. f. Mix the solution thoroughly.3. Calibration of the atomic absorption spectrometer: a. Prepare a series of nickel standard solutions with known concentrations e.g., 0, 1, 2, 5, and 10 ppm using a nickel standard stock solution and deionized water. b. Set up the atomic absorption spectrometer according to the manufacturer's instructions, and select the appropriate wavelength for nickel typically 232.0 nm . c. Aspirate the blank 0 ppm solution into the spectrometer and adjust the absorbance to zero. d. Aspirate each of the standard solutions into the spectrometer and record their absorbance values. e. Plot the absorbance values against the corresponding nickel concentrations to create a calibration curve.4. Sample analysis: a. Aspirate the digested and diluted soil sample solution into the atomic absorption spectrometer. b. Record the absorbance value of the sample.5. Calculation of nickel concentration: a. Use the calibration curve to determine the concentration of nickel in the soil sample solution based on its absorbance value. b. Calculate the concentration of nickel in the original soil sample by considering the dilution factor during sample preparation.6. Report the concentration of nickel in the soil sample in units such as mg/kg or ppm.