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Metal Concentrations and Source Apportionment of PM2.5 in Chiang Rai and Bangkok, Thailand during a Biomass Burning Season
ACS Earth and Space Chemistry ( IF 3.4 ) Pub Date : 2020-06-19 , DOI: 10.1021/acsearthspacechem.0c00140
Jariya Kayee 1 , Penjai Sompongchaiyakul 1, 2 , Nivedita Sanwlani 3 , Sujaree Bureekul 1, 2 , Xianfeng Wang 3, 4 , Reshmi Das 4, 5
Affiliation  

One of the persistent environmental problems in the provinces of northern Thailand is severe air pollution during the dry season because of open vegetation burning by farmers for land clearance purpose. Aerosol optical depth and Ångström exponent data from MODIS-Terra satellite indicated that from mid-March to April, 2019, entire Thailand was covered with a high concentration of fine-sized aerosols. Trace metal concentrations of PM2.5 collected from Chiang Rai in northern Thailand and Bangkok in southern Thailand between January and April 2019 were analyzed. Average concentrations of crustal metals such as Al, Ca, and Fe are higher in Chiang Rai compared to that in Bangkok. The Fe/Al ratio in Chiang Rai decreases from 1.65 during the onset of haze to 0.87 during the peak haze approaching a crustal ratio of 0.48. In contrast, Bangkok has higher Na, Mg, and Zn with an average Na/Mg ratio of 6.07 indicative of a sea spray (Na/Mg ∼ 8) origin. Principal component analysis identifies three possible sources in Chiang Rai: (1) crustal dust and biomass burning, (2) industrial source, and (3) refuse incineration mixed with road dust; and for Bangkok (1) natural background, industrial emissions, and coal combustion, (2) traffic emission, and (3) sea spray. The ranges of Pb isotope ratios in the bulk fraction of PM2.5 in Chiang Rai (206Pb/207Pb = 1.1445–1.1657 and 208Pb/207Pb = 2.4244–2.4468) and Bangkok (206Pb/207Pb = 1.1343–1.1685 and 208Pb/207Pb = 2.4138–2.4450) are not significantly different. However, in a time series plot, 206Pb/207Pb ratios in Chiang Rai follow PM2.5 during the peak burning season and correlate well with the Al/Pb (r2 = 0.61) ratios, indicating that at least part of the Pb is derived from crustal dust during peak fire. Using a binary mixing model, the most radiogenic Pb isotopes in Chiang Rai during the peak haze can be explained by ∼5 to 30% mixing of crustal dust with ∼35–40% biomass burning generated aerosols with the background. From the trace metal systematics and Pb isotope ratios, it is evident that (1) during the biomass burning season, trace metals from Chiang Rai are not transported down south to Bangkok and (2) in addition to metals released from biomass burning, the raging fire remobilizes crustal dust that forms an important source of Pb and other trace metals in the Chiang Rai aerosol.

中文翻译:

生物质燃烧季节泰国清莱和曼谷的PM 2.5的金属浓度和来源分摊

泰国北部各省持续存在的环境问题之一是干旱季节的严重空气污染,这是由于农民为了清除土地目的而燃烧开放的植被。来自MODIS-Terra卫星的气溶胶光学深度和Ångström指数数据表明,从2019年3月中至2019年4月,整个泰国都覆盖着高浓度的细颗粒气溶胶。痕量金属PM 2.5浓度分析了2019年1月至2019年4月从泰国北部清莱和泰国南部曼谷收集的数据。与曼谷相比,清莱的地壳金属(例如铝,钙和铁)的平均浓度更高。清莱的铁铝比从雾霾开始时的1.65降低到雾霾高峰时的0.87,接近地壳比0.48。相比之下,曼谷的Na,Mg和Zn含量更高,平均Na / Mg比为6.07,表明有海浪(Na / Mg〜8)起源。主成分分析确定了清莱的三种可能来源:(1)地壳粉尘和生物质燃烧;(2)工业来源;(3)垃圾焚烧与道路粉尘混合;对于曼谷(1)自然背景,工业排放和煤炭燃烧,(2)交通排放,以及(3)海浪。2.5清莱(206 PB / 207 PB = 1.1445-1.1657和208的Pb / 207 PB = 2.4244-2.4468)和曼谷(206 PB / 207 PB = 1.1343-1.1685和208的Pb / 207 PB = 2.4138-2.4450)不明显不同。然而,在时间序列图中,清莱的206 Pb / 207 Pb比率在燃烧高峰期遵循PM 2.5,并且与Al / Pb(r 2= 0.61)的比率,表明至少有一部分Pb是在峰值火灾期间从地壳尘埃中提取的。使用二元混合模型,清雾高峰期清莱中放射性最高的Pb同位素可以解释为地壳粉尘约5%至30%与生物质燃烧约35-40%产生的气溶胶为背景。从痕量金属系统和铅同位素比率来看,很明显(1)在生物质燃烧季节,来自清莱的痕量金属没有向下运输到曼谷南部(2)除了生物质燃烧释放的金属之外,大火使地壳尘埃带走,地壳尘埃是清莱气雾剂中铅和其他微量金属的重要来源。
更新日期:2020-07-16
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