Department of Civil and Environmental Engineering, National University of Singapore, 117576, Singapore.
Department of Civil and Environmental Engineering, National University of Singapore, 117576, Singapore.
Environ Pollut. 2020 Feb;257:113425. doi: 10.1016/j.envpol.2019.113425. Epub 2019 Oct 19.
Light absorbing carbonaceous aerosols (LACA) consisting of black carbon (BC) and brown carbon (BrC) have received considerable attention because of their climate and health implications, but their sources, characteristics and fates remain unclear in Southeast Asia (SEA). In this study, we investigated spatio-temporal characteristics of LACA, their radiative properties and potential sources in Singapore under different weather conditions. Hourly BC concentrations, measured from May 2017 to March 2018, ranged from 0.31 μg/m to 14.37 μg/m with the mean value being 2.44 ± 1.51 μg/m. High mass concentrations of BC were observed during the south-west monsoon (SWM, 2.60 ± 1.56 μg/m) while relatively low mass concentrations were recorded during the north-east monsoon (NEM, 1.68 ± 0.96 μg/m). There was a shift in the Absorption Ångström exponent (AAE) from 1.1 to 1.4 when the origin of LACA changed from fossil fuel (FF) to biomass burning (BB) combustion. This shift is attributed to the presence of secondary BrC in LACA, derived from transboundary BB emissions during the SWM. Lower AAE values were observed when local traffic emissions were dominant during the NEM. This explanation is supported by measurements of water-soluble organic carbon (WSOC) in LACA and the corresponding AAE values determined at 365 nm using a UV-vis spectrophotometer. The AAE values, indicative of the presence of brown carbon (BrC), showed that photochemically aged LACA contribute to an enhancement in the light absorption of aerosols. In addition, spatio-temporal characteristics of BC in the intra-urban environment of Singapore were investigated across diverse outdoor and indoor microenvironments. High variability of BC was evident across these microenvironments. Several air pollution hotspots with elevated BC concentrations were identified. Overall, the results stress a need to control anthropogenic emissions of BC and BrC in order to mitigate near-term climate change impacts and provide health benefits.
光吸收碳质气溶胶（LACA）由黑碳（BC）和棕色碳（BrC）组成，由于其对气候和健康的影响而受到广泛关注，但它们的来源、特性和命运在东南亚（SEA）仍不清楚。在这项研究中，我们调查了在不同天气条件下新加坡 LACA 的时空特征、其辐射特性和潜在来源。2017 年 5 月至 2018 年 3 月，每小时 BC 浓度的测量范围为 0.31μg/m 至 14.37μg/m，平均值为 2.44±1.51μg/m。在西南季风（SWM）期间，BC 的质量浓度较高（2.60±1.56μg/m），而在东北季风（NEM）期间记录到的质量浓度相对较低（1.68±0.96μg/m）。当 LACA 的来源从化石燃料（FF）转变为生物质燃烧（BB）燃烧时，吸收 Ångström 指数（AAE）从 1.1 变为 1.4。这种转变归因于 LACA 中存在的次生 BrC，这是在 SWM 期间跨界 BB 排放的结果。当 NEM 期间本地交通排放占主导地位时，AAE 值较低。这一解释得到了 LACA 中水溶性有机碳（WSOC）的测量和使用紫外可见分光光度计在 365nm 处确定的相应 AAE 值的支持。AAE 值表明棕色碳（BrC）的存在，表明光化学老化的 LACA 有助于增强气溶胶的光吸收。此外，还研究了新加坡城市内环境中跨不同户外和室内微观环境的 BC 的时空特征。这些微观环境中 BC 的变化很大。确定了几个 BC 浓度升高的空气污染热点。总的来说，研究结果强调需要控制人为排放的 BC 和 BrC，以减轻短期气候变化的影响并带来健康益处。
