High PM_2.5 (particulate matter with an aerodynamic diameter 2.5 μm or less) concentrations are known to cause severe chronic cardiovascular and respiratory diseases. The present study assesses the dithiothreitol (DTT)-based oxidative potential (OP) measured on PM_2.5 filters extracted with a mixture of water and methanol. PM_2.5 samples were collected during paddy-residue burning that occurs every year in the northwest Indo-Gangetic Plain (IGP) during October–November. The entire study period was classified into four categories: pre-intense burning, Diwali, intense burning, and post-intense burning. On average, the PM_2.5 mass concentrations were 154 ± 59, 340 ± 74, 271 ± 122, and 156 ± 19 μg m^–3; volume-normalized OP (OP_V) values were 7.6 ± 2.8, 9.4 ± 1.1, 14 ± 5.1, and 12 ± 1.9 nmol DTT min^–1 m^–3; and mass-normalized OP (OP_M) values were 51 ± 18, 29 ± 7, 55 ± 12, and 78 ± 9 pmol DTT min^–1 μg^–1 during pre-intense burning, Diwali, intense burning, and post-intense burning periods, respectively. The intense burning period was associated with a relatively high mass fraction of organic aerosols compared to Diwali that was associated with a relatively higher fraction of inorganic aerosols. It likely caused higher OP_V during the intense burning period compared to Diwali, which highlights the role of chemical composition in PM_2.5 OP. The observed OP_V value during the intense burning period is the globally highest reported value (average 14 nmol DTT min^–1 m^–3). Biomass burning markers, such as organic carbon/elemental carbon (OC/EC) and K⁺/EC, correlated significantly with OP_V during the intense burning period, attesting the effect of burning emissions on the observed OP. The relationship of OP_OC (ratio of OP_V and OC mass concentration) with specific brown carbon chromophores during the post-intense burning period indicates the plausible link between atmospheric aging of redox-active organic aerosols and their optical properties. Development of a mitigation strategy for such high DTT-active PM_2.5 is important to avoid a wide array of possible health effects on the inhabitants of the study and downwind regions.

中文翻译：

---

西北印度恒河平原大规模稻田燃烧产生的大气 PM2.5 具有显着的高氧化潜力

众所周知，高 PM _2.5（空气动力学直径小于等于 2.5 微米的颗粒物）浓度会导致严重的慢性心血管和呼吸系统疾病。本研究评估了在用水和甲醇的混合物提取的PM _2.5过滤器上测量的基于二硫苏糖醇 (DTT) 的氧化电位 (OP) 。PM _2.5样本是在每年 10 月至 11 月期间在西北印度恒河平原 (IGP) 发生的稻谷残渣燃烧过程中收集的。整个研究期间分为四类：前强烈燃烧、排灯节、强烈燃烧和后强烈燃烧。平均而言，PM _2.5质量浓度为 154 ± 59、340 ± 74、271 ± 122 和 156 ± 19 μg m ^–3; 体积标准化 OP (OP _V ) 值为 7.6 ± 2.8、9.4 ± 1.1、14 ± 5.1 和 12 ± 1.9 nmol DTT min ^–1 m ^–3；和质量归一化 OP (OP _M ) 值分别为 51 ± 18、29 ± 7、55 ± 12 和 78 ± 9 pmol DTT min ^–1 μg ^–1在强烈燃烧前、排灯节、强烈燃烧和后强烈燃烧期间燃烧期，分别。与排灯节相比，强烈燃烧期与有机气溶胶的质量分数相对较高有关，排灯节与无机气溶胶的比例相对较高。与排灯节相比，它可能在强烈燃烧期间导致更高的 OP _V，这突出了化学成分在 PM _{2.5 中的作用}操作。在强烈燃烧期间观察到的 OP _V值是全球最高的报告值（平均 14 nmol DTT min ^–1 m ^–3）。生物质燃烧标志物，如有机碳/元素碳 (OC/EC) 和 K ⁺ /EC，在强烈燃烧期间与 OP _V显着相关，证明了燃烧排放对观察到的 OP 的影响。OP _OC的关系（OP _V的比值和 OC 质量浓度）在后期强烈燃烧期间具有特定的棕色碳发色团，表明氧化还原活性有机气溶胶的大气老化与其光学特性之间可能存在联系。为这种高 DTT 活性 PM _2.5制定缓解策略对于避免对研究和顺风地区居民的各种可能的健康影响非常重要。