Characteristics of water-soluble ions and carbon in fine and coarse particles collected near an open burning site

This study investigates the chemical characteristics of particles that were collected from the open burning of wax apple agricultural waste, and evaluates the impact of such burning on regional air quality. The water-soluble ions, elemental carbon (EC), and organic carbon (OC) in fine (Dp ≤ 2.5 μm) and coarse (2.5 < Dp ≤ 10 μm) particles were collected using a micro-orifice uniform deposition impactor (MOUDI) and two Dichot samplers. The average PM2.5/PM10 ratio during open burning (0.90) was higher than those both before and after burning (0.57 and 0.55, respectively). The particle distributions before and during burning were bi-modal and uni-modal, respectively. During the open burning, the OC or K+ content markedly increased; however, that of secondary aerosol ( NH 4 + , NO 3 − and SO 4 2 − ) decreased. The Na+/Cl− molar ratios of fine particles before, after, and during the open burning 0.40, 0.18, and 0.24, respectively; however, the corresponding (Na+ + K+)/Cl− molar ratios were 0.74, 0.99, and 0.39, respectively. OC, K+ and Cl− were quite abundant in the open burning of agricultural waste (wax apple), and the OC/Na+, K+/Na+, and Cl−/Na+ (mass) ratios in fine particles (318, 10.2, and 10.5, respectively) may be used as reference indexes associated with the open burning of wax apple waste.