Ionic Compositions of Sequential Rainfall Samples as Source Signatures of Forest Fire Emissions

Abstract

In this study, two rainfall events following the Antalya forest fires were sampled via a volume-based sequential sampling method. Two and four fractional samples were obtained from the first (S) and the second (M) rainfall events, respectively. pH and the conductivity of the fractional samples were measured at the end of the sampling. Fractional samples were analyzed for water-soluble ions. The water-insoluble particulate matter in the samples were analyzed for their particle size distributions using a particle size analyzer, and the morphologies of the particles were characterized using Scanning Electron Microscopy Energy Dispersive X-ray Spectroscopy (SEM–EDS). Concentrations of F⁻, Br⁻, NO₂⁻, Cl⁻, NO₃⁻, SO₄²⁻, PO₄³⁻, Ca²⁺, Na⁺, Mg²⁺, NH₄⁺, K⁺, Li⁺ were determined by ion chromatography (IC). In the sequential rain samples, the average pH values were observed in the range of 5.37–6.35. 35 and no acid rain event was observed. In the particle size analysis results of rain samples, the highest measured value was 204.732 µm in S-series samples and 56.300 µm in M-series samples. Possible sources and/or source regions of the measured species were estimated using upper atmospheric back trajectory analyses and local wind roses. Markers of forest fires were determined as sulfate, chloride, calcium, ammonium, and potassium ions which were compared with the PM₁₀ and PM_2.5 forest fire emission source profiles reported in the US EPA SPECIATE database. In studies on the determination of air pollution transports; particles are collected on the filter and examined. This can cause many particles to accumulate on the filter and make it difficult to characterize. The use of a SEM device together with a particle size analyzer to characterize and detect particles in rainwater provides more successful results. The collected deposition event is more likely to obtain a single atmospheric particulate matter in samples than samples obtained directly from wet or dry deposition.