Particulate n-alkanes are major constituents of organic aerosols (OA). Being primary in origin, chemically stable and thus long-lived, n-alkanes retains source signatures and along with diagnostic parameters have extensively been used to identify source(s) of OA. Systematic, yearlong study was carried out in the Dhauladhar region of North-Western Himalaya (NWH) to investigate dynamics in the composition and concentration of aerosol-associated n-alkanes. PM₁₀ samples were collected for 24 h, once every week, at an urban mid-altitude location (Dharamshala) and a rural low-altitude site (Pohara). Particulate bound n-alkanes were identified and quantified using thermal desorption gas chromatography mass spectrometry (TD-GCMS). Annual mean concentrations of total n-alkanes (TNA) were 211 ± 99 ng m⁻³ and 223 ± 83 ng m⁻³, while mass fractions of TNA in PM₁₀ were 4410 ± 1759 ppm and 3622 ± 1243 ppm at Dharamshala and Pohara, respectively. At both sites, a slight dominance of odd carbon-numbered n-alkanes was noticed. The TNA concentration and associated diagnostic parameters indicated unique source profiles at rural and urban locations. Significant seasonal variations were attributed to the contrasting land-use settings and meteorological variations. Influence of petrogenic contributions at urban location and predominance of biogenic contributions at rural location were observed in spring and autumn seasons. Preliminary insights on sources of organic aerosols are presented here. The diagnostic parameters allowed apportionment of biogenic and petrogenic sources. Biogenic emissions from agricultural practices viz. harvesting and threshing were predominant in the rural settings, while tourism-led anthropogenic contributions significantly add to petrogenic contributions in urban environment of the NWH region.

中文翻译：

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喜马拉雅西北部Dhauladhar地区上与气溶胶相关的正构烷烃：来源和过程的季节性变化。

颗粒正构烷烃是有机气溶胶（OA）的主要成分。作为主要来源，化学稳定，因此使用寿命长的正构烷烃具有来源特征，并且与诊断参数一起已广泛用于鉴定OA的来源。为期一年的系统研究在喜马拉雅西北部（NWH）的Dhauladhar地区进行，以调查与气溶胶相关的正构烷烃的组成和浓度的动态变化。每周一次在市区中海拔地区（达兰萨拉）和农村低海拔地区（Pohara）收集PM ₁₀样品，持续24小时。使用热脱附气相色谱质谱法（TD-GCMS）对结合的正构烷烃进行了鉴定和定量。总正构烷烃（TNA）的年平均浓度为211±99 ng m ^-3和223±83 ng m ^-3，而PM ₁₀中TNA的质量分数Dharamshala和Pohara分别为4410±1759 ppm和3622±1243 ppm。在两个站点上，都发现了奇数的碳数正构烷烃。TNA浓度和相关的诊断参数显示了农村和城市地区的独特来源概况。明显的季节变化是由于土地利用环境和气象变化形成对比。在春季和秋季，观察到城市地区的成因贡献的影响和农村地区的主要成因贡献。本文介绍了有关有机气溶胶来源的初步见解。诊断参数允许分配生物源和岩石源。农业实践中的生物源排放。在农村地区，收割和脱粒居多