A facile digestion protocol for metal analysis in ambient aerosols: Implications to mineral dust characteristics and human health impact

Abstract

Assessment of atmospheric metals produced from natural or anthropogenic sources is a major concern of many researchers worldwide for their source characterization and hazardous health impacts. Currently, many high tier labs, equipped with chemical (microwave digestion system), optical (X-ray fluorescence spectroscopy) or nuclear techniques (instrumental neutron activation analysis) can lead to or produce accurate data of metals rapidly. Owing to low concentration of several metals, large heterogeneity and matrix effect in atmospheric aerosol samples, many a times the chemical digestion followed by quantification approach is widely preferred. However, in South and South-east Asia, the major data set of atmospheric metals is relatively lacking, due to unavailability of rapid digestion technique in many labs. Towards this we report a new and facile analytical protocol for complete digestion of metals in atmospheric aerosols. Finalized protocol for metal digestion in ~ 12 h involves sample treatment with a mixture of HF+HNO3+H2O2+H2O in 1: 4: 1: 6 (v/v) at 150 ºC. This protocol has been successfully applied for complete digestion and quantification of several metals (Al, As, Ca, Cd, Co, Cr, Cu, Fe, Mg, Mn, Ni, Pb, V and Zn) in high-loading ambient PM2.5 (particulate matter of aerodynamic diameter ≤2.5 µm; 95240 µg m-3).Mineral dust composition over IGP (Northern India) looks distinctly different than that over western India (reported previously). Several toxic metals (As, Cd, Cu,Pb, V and Zn) show enrichment factor more than 10, suggesting their significant inputs from anthropogenic sources.Thus, our analytical protocol could facilitate for accurate and rapid analysis of metals pertaining to environmental and toxicological research.