Geological Oceanography Division, CSIR-National Institute of Oceanography, Dona Paula, Goa-403 004, India.
Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, India.
Environ Sci Process Impacts. 2022 Jan 26;24(1):72-88. doi: 10.1039/d1em00347j.
The marine atmosphere of the Bay of Bengal (BoB) is prone to get impacted by anthropogenic aerosols from the Indo-Gangetic Plain (IGP) and Southeast Asia (SEA), particularly during the northeast monsoon (NEM). In this study, we quantify and characterize carbonaceous aerosols and their absorption properties collected in two cruise campaigns onboard ORV Sindhu Sadhana during the continental outflow period over the BoB. Aerosol samples were classified based on the air mass back trajectory analyses, wherein samples were impacted by the continental air parcel (CAP), marine air parcel (MAP), and mix of both (CAP + MAP). Significant variability in the PM mass concentration (in μg m) is found with a maximum value for MAP samples (75.5 ± 36.4) followed by CAP + MAP (58.5 ± 27.3) and CAP (58.5 ± 27.3). The OC/EC ratio (>2) and diagnostic tracers nss-K/EC (0.2-0.96) and nss-K/OC (0.11-1.32) along with the absorption angstrom exponent (AAE: 4.31-6.02) and MODIS (Moderate Resolution Imaging Spectroradiometer) derived fire counts suggest the dominance of biomass burning emission sources. A positive correlation between OC and EC ( = 0.86, 0.70, and 0.42 for CAP, MAP, and CAP + MAP, respectively) further confirmed the similar emission sources of carbonaceous species. Similarly, a significant correlation between estimated secondary organic carbon (SOC) and water-soluble organic carbon (WSOC; = 0.99, 0.96, and 0.97 for CAP, MAP, and CAP + MAP, respectively) indicate their similar chemical nature as well as dominant contribution of SOC to WSOC. The absorption coefficient () and mass absorption efficiency (MAE) of the soluble fraction were estimated at 365 nm wherein, showed a linear relationship with WSOC and nss-K, signifying the contribution of water soluble brown carbon from biomass burning emissions. The estimated MAE (0.30-0.93 m g), during this study, was consistent with the earlier observations over the BoB, particularly during the continental outflow season.
孟加拉湾（BoB）的海洋大气容易受到来自印度恒河平原（IGP）和东南亚（SEA）的人为气溶胶的影响，特别是在东北季风（NEM）期间。在这项研究中，我们量化并描述了在 BoB 上进行的两次“ORV Sindhu Sadhana”号考察期间，收集到的在大陆流出期间受到影响的碳质气溶胶及其吸收特性。根据大气质量后轨迹分析对气溶胶样本进行分类，其中样本受到大陆气团（CAP）、海洋气团（MAP）和两者混合（CAP + MAP）的影响。PM 质量浓度（μg m）存在显著变化，MAP 样本的最大值为 75.5 ± 36.4μg m，其次是 CAP + MAP（58.5 ± 27.3μg m）和 CAP（58.5 ± 27.3μg m）。OC/EC 比值（>2）和诊断示踪剂 nss-K/EC（0.2-0.96）和 nss-K/OC（0.11-1.32）以及吸收 Angstrom 指数（AAE：4.31-6.02）和 MODIS（中分辨率成像光谱仪）衍生的火灾计数表明，生物质燃烧排放源占主导地位。OC 和 EC 之间存在正相关关系（= 0.86、0.70 和 0.42，分别为 CAP、MAP 和 CAP + MAP），进一步证实了碳质物质的相似排放源。同样，估算的二次有机碳（SOC）和水溶性有机碳（WSOC）之间存在显著相关性（= 0.99、0.96 和 0.97，分别为 CAP、MAP 和 CAP + MAP），表明它们具有相似的化学性质以及 SOC 对 WSOC 的主要贡献。在 365nm 处估计了可溶性部分的吸收系数（）和质量吸收效率（MAE），其中与 WSOC 和 nss-K 呈线性关系，表明来自生物质燃烧排放的水溶性棕色碳的贡献。本研究中估计的 MAE（0.30-0.93 m g）与 BoB 上的早期观测结果一致，特别是在大陆流出季节。
