Comparative elemental analysis of soil of wheat, corn, rice, and okra cropped field using CF-LIBS

The food chain is responsible for harmful chemical poisoning due to land pollution. Heavy metal contamination of the food chain is regarded as one of the key environmental channels of human exposure leading to possible health risks. The purpose of this study was to investigate the toxic elements of soil samples of different cropped fields of the specific parts on the lower course of the river Indus in district Jamshoro, the southern Sindh province of Pakistan. We report the comparative elemental composition of the Soil at 3 and 6 in. depth of the wheat, rice, corn, and okra cropped field using Laser-Induced Breakdown Spectroscopy (LIBS). Soil plasma is generated using Q-Switched Nd: YAG laser (1064 nm), 5 ns pulse duration, and 10 Hz repetition rate. At laser energy of 25 mJ the estimated irradiance is 7.15 × 1010 W/cm2. In this experimentation we have detected the Fe, Si, Mg, Ca, Al, Ba, Hg, Cr, Ni, Mn, H, Cu, Li, Sr, K, Ti, Na, Pb, V, and C in soil plasma spectra at the depth of 3 in. and 6 in. of wheat, rice, corn, and okra cropped field. We have estimated the electron temperature and electron number density under the assumption of the local thermodynamic equilibrium. We have found electron temperature (Te) corn plasma (3 in. depth) in the range of (13768–7003) K and electron number density (Ne) in the range of (9.01–5.18) × 1016 cm−3. In addition, we have also estimated the weight percentage of the different soil samples using Calibration Free LIBS (CF–LIBS). •The Laser-Induced Breakdown Spectroscopy technique was used for the analysis of soil-cropped plasma.•Recombination rate of soil-cropped plasma.•Detection of heavy metals in soil cropped field.•Soil plasma parameters such as electron temperature and electron number density.•A singly ionic calcium line was used to calculate electron number density.