Phosphorus emission from open burning of major crop residues in China

Biomass burning has been recognized as an important primary source of atmospheric phosphorus (P), but the measurements of P from biomass burning particles are lacking. In this work, emission factors of different P forms, including total P (TP), total dissolved P (TDP), dissolved inorganic P (DIP) and dissolved organic P (DOP), in emission particles from four types of crop residues burning were measured in a number of chamber experiments. Based on the measured emission factors and the amount of crop residue burned, a high-resolution (0.25° × 0.25°) emission inventory of P for China during 2011-2015 was firstly developed. The emission factors of TP, DIP and DOP were 0.23, 0.06 and 0.13 g/kg, 0.57, 0.17 and 0.27 g/kg, 0.52, 0.15 and 0.27 g/kg, 0.43, 0.13 and 0.25 g/kg for wheat, corn, soybean and rice straw burning, respectively. The total emissions of TP, TDP, DIP, and DOP from the four types of crop straw open burning were 72.0 × 10³ ± 6.7 × 10³ Tons, 56.3 × 10³ ± 5.5 × 10³, 20.9 × 10³ ± 2.0 × 10³ and 35.4 × 10⁴ ± 3.4 × 10³ Tons, respectively. TDP dominated the TP fraction, indicating that biomass burning was the important source of bioavailable P. The high P emission areas were mainly distributed in the Northeast and North China Plain, where were the main grain production areas in China, while P emission in economically developed areas such as Beijing and Shanghai and western areas such as Tibet and Qinghai was lower. Affected by the harvesting periods of crops, high P emissions peaked in March, April, June and October. The results herein can provide a dataset for modeling research in calculating the contribution of biomass burning sources to atmospheric P; therefore reduce uncertainties in estimating atmospheric P deposition.