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首页> 外文期刊>Journal of Asian earth sciences >Seasonal and diurnal variations in dust characteristics on the northern slopes of the Tien Shan - Grain-size, mineralogy, chemical signatures and isotope composition of attached nitrate
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Seasonal and diurnal variations in dust characteristics on the northern slopes of the Tien Shan - Grain-size, mineralogy, chemical signatures and isotope composition of attached nitrate

机译：天山北坡粉尘特征的季节性和昼夜变化-附着硝酸盐的粒度，矿物学，化学特征和同位素组成

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摘要

A dust monitoring program was initiated in the summer of 2010 to (ⅰ) improve the informative value of aeolian components of varved lake sediments in Central Asia for palaeoclimatic interpretations, (ⅱ) evaluate the impact of aeolian influx on modern lakes in the region and (ⅲ) obtain data for a future comparison with dust east of the high mountain belt formed by the Alay, Pamir, Tien Shan and Altai mountains. We collected the coarse (＞2.5 μm) dust fraction on the northern slopes of the Tien Shan 42°40′49.69″N, (74°41′37.36″E, 1740 m asl) using a high-volume slit-impactor at 3-day sampling intervals. We present data on the mineralogical composition, particle-size distribution, soluble salts and nitrate isotope composition of the collected dust. The short-term and seasonal changes in dust concentration and composition are discussed in the context of high temporal resolution measurements of meteorological parameters and particle counts for 31 grain-size bands. Throughout the study period, CaCO_3 was a major dust constituent (average particle frequency 14%). Between July 2010 and October 2012, the average content of soluble salts was 10 wt.%; mole percentages of water-leachable anions were 60% NO_3, 30% SO_4, 10% Cl. Ca was the dominant teachable cation (＞90%). The collected dust comprised (ⅰ) gypsum which forms pedogenically in the topsoils of arid regions and (ⅱ) secondary gypsum originating from the interaction of sulphuric acid aerosols with CaCO_3 in the atmosphere. Variable proportions of (ⅰ) and (ⅱ) and the extent of Ca(NO_3)_2 formation (verified by chemical mass budgets) were documented in the Ca/Sr and Ca/SO_4 ratios of the aqueous leachates. The isotopic compositions of the dust nitrate in the majority of the samples clustered between -10 and +10‰ for δ~(15)N[NO_3] (VSMOW) and +50 and +100‰ for δ~(18)O[NO_3] (Air). The δ~(18)O[NO_3] values of a majority of the collected samples exhibited a weak positive correlation with the NO_3 load of the collected dust (R~2 = 0.148). The time series of the δ~(15)N[NO_3] values varied around a basement level of -6‰, which indicates that NO_x from mobile sources is a major precursor of the dust-NO_3. The distinct, positive departures from these values correlated with increases in the content of soot. We conclude that the related δ~(15)N[NO_3] peaks reflect increased NO_x contributions from coal burning. The possible origin of the dust was evaluated using satellite images and backward trajectory calculations for a few example monitoring intervals. Data synthesis in the context of hemispherical atmospheric circulation models, including the data for 2013, the results from ongoing chemical and isotope analyses of the non-soluble solid residues of the collected materials and the statistical handling of an extended data set will further elucidate the relationships involving atmospheric circulation, atmospheric dust load, dust sources and the characteristics of the study region.
机译：于2010年夏季启动了一项粉尘监测计划，目的是（improve）提高中亚裂谷湖沉积物中的风沙成分对古气候解释的信息价值，（ⅱ）评估风沙涌入对该地区现代湖泊的影响，并（ ⅲ）获取数据，以便将来与由阿拉伊，帕米尔，天山和阿尔泰山脉形成的高山带以东的尘埃进行比较。我们使用3英寸的大体积裂隙冲击器在天山42°40′49.69″ N，（74°41′37.36″ E，1740 m asl）的北坡上收集了粗尘（＞ 2.5μm）。天采样间隔。我们提供有关收集的粉尘的矿物学组成，粒度分布，可溶性盐和硝酸盐同位素组成的数据。在对31个粒度带的气象参数和颗粒计数进行高时间分辨率测量的背景下，讨论了粉尘浓度和成分的短期和季节性变化。在整个研究期间，CaCO_3是主要的粉尘成分（平均颗粒频率为14％）。在2010年7月至2012年10月期间，可溶性盐的平均含量为10 wt。％；可水溶阴离子的摩尔百分数为60％NO_3、30％SO_4、10％Cl。 Ca是主要的可教导阳离子（＞ 90％）。收集到的粉尘包括（ⅰ）在干旱地区表土成土形成的石膏和（ⅱ）源自大气中硫酸气溶胶与CaCO_3相互作用的次生石膏。在水浸出液中Ca / Sr和Ca / SO_4的比值中记录了（ⅰ）和（ⅱ）的可变比例以及Ca（NO_3）_2形成的程度（已通过化学物质预算验证）。大部分样品中硝酸盐尘的同位素组成对于δ〜（15）N [NO_3]（VSMOW）聚集在-10和+ 10‰之间，对于δ〜（18）O [NO_3]聚集在+50和+ 100‰之间]（空气）。大多数收集样品的δ〜（18）O [NO_3]值与收集到的粉尘的NO_3负荷呈弱正相关（R〜2 = 0.148）。 δ〜（15）N [NO_3]值的时间序列在-6‰的基底水平附近变化，这表明来自移动源的NO_x是粉尘NO_3的主要前体。与这些值明显不同的正偏差与烟灰含量的增加有关。我们得出结论，相关的δ〜（15）N [NO_3]峰反映了燃煤对NO_x的贡献增加。使用卫星图像和后向轨迹计算对灰尘的可能来源进行了评估，并给出了一些示例性监视间隔。在半球形大气环流模型中的数据综合，包括2013年的数据，正在进行的对收集材料的非可溶性固体残留物进行化学和同位素分析的结果以及对扩展数据集的统计处理，将进一步阐明这些关系涉及大气环流，大气粉尘负荷，粉尘源和研究区域的特征。

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