Emission of organic carbon, elemental carbon and water-soluble ions from crop straw burning under flaming and smoldering conditions

•Emissions from crop straw burning were measured on flaming and smoldering conditions.•The compositions of TC, OC, EC and WSIs in smoke had been analyzed.•Diagnostic ratios between OC, EC and WSIs were measured and compared on different conditions.•The results might be useful to distinguish crop straw burning from other sources pollution.