Multi-pollutant emissions from the burning of major agricultural residues in China and the related health-economic effects
Abstract. Multi-pollutants in smoke particulate matter (SPM) were identified and quantified for the biomass burning of five major agricultural residues (wheat, rice, corn, cotton, and soybean straw) in China by an aerosol chamber system combined with various measurement techniques. The primary emission factors (EFs) for PM1. 0 and PM2. 5 are 3.04–12.64 and 3.25–15.16 g kg−1. Organic carbon (OC), elemental carbon (EC), water-soluble inorganics (WSIs), water-soluble organic acids (WSOAs), water-soluble amine salts (WSAs), trace mineral elements (THMs), polycyclic aromatic hydrocarbons (PAHs), and phenols in smoke PM1. 0/PM2. 5 are 1.34–6.04/1.54–7.42, 0.58–2.08/0.61–2.18, 0.51–3.52/0.52–3.81, 0.13–0.64/0.14–0.77, (4.39–85.72/4.51–104.79) × 10−3, (11.8-51.1/14.0-131.6) × 10−3, (1.1–4.0/1.8–8.3) × 10−3, and (7.7–23.5/9.7–41.5) × 10−3 g kg−1, respectively. Black carbon (BC) mainly exists in PM1. 0; heavy-metal-bearing particles favour residing in the range of smoke PM1. 0−2. 5, which is also confirmed by individual particle analysis.
With respect to the five scenarios of burning activities, the average emissions and overall propagation of uncertainties at the 95 % confidence interval (CI) of SPM from agricultural open burning in China in 2012 were estimated to be 1005.7 (−24.6, 33.7 %), 901.4 (−24.4, 33.5 %), 432.4 (−24.2, 33.5 %), 134.2 (−24., 34.0 %), 249.8 (−25.4, 34.9 %), 25.1 (−33.3, 41.4 %), 5.8 (−30.1, 38.5 %), 8.7 (−26.6, 35.6 %), 0.5 (−26.0, 34.9 %), and 2.7 (−26.1, 35.1 %) Gg for PM2. 5, PM1. 0, OC, EC, WSI, WSOA, WSA, THM, PAHs, and phenols , respectively. The emissions were further spatio-temporally characterized using a geographic information system (GIS) in different regions in the summer and autumn post-harvest periods. It was found that less than 25 % of the total emissions were released during the summer harvest, which was mainly contributed by the North Plain and the centre of China, especially Henan, Shandong, and Anhui, which are the top three provinces regarding smoke particle emissions.
Flux concentrations of primarily emitted smoke PM2. 5 that were calculated using the box-model method based on five versions of emission inventories all exceed the carcinogenic-risk permissible exposure limits (PEL). The health impacts and health-related economic losses from the smoke PM2. 5 short-term exposure were assessed. The results show that China suffered from 7836 cases (95,% CI: 3232, 12362) of premature mortality and 7 267 237 cases (95 % CI: 2 961 487, 1 130 784) of chronic bronchitis in 2012, which led to losses of USD 8822.4 million (95 % CI: 3574.4, 13 034.2) or 0.1 % of the total GDP. We suggest that the percentage of open-burnt crop straw in the post-harvest period should be cut down by over 97 % to ensure a reduction in carcinogenicity risk, especially in the North Plain and the northeast, where the emissions should decrease at least by 94 % to meet the PEL. With such emission control, over 92 % of the mortality and morbidity attributed to agricultural fire smoke PM2. 5 can be avoided in China.
