The present study outlines the mechanism and brings out the chemistry involved in winter haze formation characterized by reduced visibility and severe respiratory problems especially in rural areas. It deals with the study of aerosol chemical composition and meteorological parameters in two consecutive winter seasons (2015/16 and 2016/17). Elevated PM_2.5 mass concentrations were recorded (average = 231.5 ± 12.9 and 257.1 ± 21.9 μg m⁻³ in 2015/16 and 2016/17, respectively) during haze (polluted) days which was more than twice the PM concentrations during non-haze days (average = 101.6 ± 20.2 and 110.2 ± 25.4 μg m⁻³ in 2015/16 and 2016/17, respectively). During non-haze period, the contribution of carbonaceous aerosols (CAs) and secondary inorganic aerosols (SIAs) was 40% and 29% of PM_2.5 but when haze formed both CAs and SIAs increased. During haze (polluted) episodes, high OC/EC ratios (>3.0) indicated secondary organic aerosol formation and high NH₄⁺/SO₄²⁻ molar ratios (>2.0) indicated the formation of (NH₄)₂SO₄ and NH₄HSO₄ as major NH₄⁺ salts. The results obtained with E-AIM Model simulations showed good agreement with measured values. E Aim Model IV was used to estimate liquid water content (LWC) and formation of inorganic salts. LWC (863 μg m⁻³; in situ hydrogen ion concentration, [H⁺]_ins = 1.2 nmol m⁻³, and pH: 2.76) was high during haze (polluted) days as compared to non-haze days (750 μg m⁻³; [H⁺] _ins = 2.4 nmol m⁻³, and pH:1.89) indicating enhanced hygroscopic growth of the ionic solids during haze (polluted) as compared to non-haze period. These results further corroborate the occurrence and predominance of heterogeneous reactions (under highly hygroscopic conditions) during haze (polluted) days in contrast to non-haze days when gas-phase as well as heterogeneous reactions both may occur.

本研究概述了机理，并揭示了以冬季能见度降低和严重的呼吸问题为特征的冬季霾形成所涉及的化学物质，特别是在农村地区。它研究了连续两个冬季（2015/16和2016/17）的气溶胶化学成分和气象参数。雾霾（污染）日记录到的PM _2.5浓度升高（平均分别在2015/16和2016/17年分别为231.5±12.9和257.1±21.9μgm ^-3），是非雾霾期间PM浓度的两倍以上天（平均值= 101.6±20.2和110.2±25.4μgm ^-3分别在2015/16和2016/17）。在非雾霾时期，碳质气溶胶（CAs）和次生无机气溶胶（SIA）的贡献占PM _2.5的40％和29％，但当雾霾形成时，CA和SIA均增加。在雾霾（污染）事件中，高OC / EC比（> 3.0）表示二次有机气溶胶形成，高NH ₄ ⁺ / SO ₄ ^2-摩尔比（> 2.0）表示（NH ₄）₂ SO ₄和NH的形成₄ HSO ₄作为主要NH ₄ ⁺盐。通过E-AIM模型仿真获得的结果与测量值显示出良好的一致性。E目的模型IV用于估算液态水含量（LWC）和无机盐的形成。与阴霾天（污染）相比，阴霾天（污染）天的LWC（863μgm ^-3；原位氢离子浓度，[H ⁺ ] _ins  =  1.2 nmol m ^-3，pH：2.76）高。⁻³ ; [H ⁺ ] _ins  =  2.4 nmol m ^-3和pH：1.89）表示，与非雾霾时期相比，雾霾（受污染）期间离子固体的吸湿性增强。这些结果进一步证实了在雾霾（污染）日中非均相反应（在高度吸湿条件下）的发生和占优势，与气相和非均相反应均可能发生的非雾霾日相反。