Comparison of ultrasonic, hotplate and microwave assisted digestion methods for the assessment of metals in agricultural soil: Environmental contamination and human health risk

Abstract

Abstract This study presents the comparison of microwave assisted, hotplate and ultrasonic digestion methods for the analysis of metals in agricultural soils prior to ICP-OES determination. The percentage recoveries for all methods were within the acceptable range of 70–120% indicating that they can all be used for accurate determination of the target metals. However, hotplate can be recommended as it does not use too high pressure and temperature which can degrade analytes and it is easily accessible. On the hand, microwave require expensive instrument and thus its accessibility may be limited in other laboratories while ultrasonic is susceptible to underestimation of sample concentration due to incomplete digestion especially for complex samples as it uses lower temperatures. The metal concentrations obtained ranged from 0.60–256.4 mg/kg, however, all the metals were below the maximum permissible limits in soil except for Cr. The contamination factor and geo-accumulation index showed that the soil samples were mainly contaminated with Cu. The human health risk assessed indicated that dermal contact was the major exposure pathway in adults and children and children were more susceptible to non-carcinogenic risks. Although metal contamination in this study was not severe, consideration and monitoring of potential pollution hazards and human health risks in the future around these agricultural soils are required.