Comparison of Two Extraction Methods for Metals from Atmospheric Particulate Matter

Particulate pollution in ambient air of Lahore is a serious problem. Atmospheric particulates concentrations (PM10) were measured at the city centre during February to April 2007, which ranged between 465 and 806 mu g/m(3) with an average of 602 mu g/m(3), about an order of magnitude greater than the World Health Organization guideline value of 50 mu g/m(3). Metal and metalloid components of particles have been shown to be of greater health significance, especially the water soluble species. A number of methods have been used to extract the total and water soluble species. In the present study one method each was evaluated for total and water soluble metals (cadmium, chromium, lead, nickel, and mercury), and metalloid species (antimony and arsenic). Segments from the same filter were used for the two methods. Concentrated acids with microwave digestion were used for total concentrations whereas water soluble species were extracted by shaking for 2 hours in one percent HCl solution. The latter method worked as well as the former for cadmium, lead, and antimony, giving about the same concentrations with good correlations. However, for the remaining elements water soluble concentrations were generally lower than the strong acid extractions, indicating lower bioavailability of such elements. Majority of the values for total as well as water soluble cadmium and lead concentrations exceeded the WHO guideline values whereas for other elements the concentrations in both fractions were within acceptable limits.