Massive atmospheric nitrate accumulation in a continental interior desert, northwestern China
Massive atmospheric nitrate accumulation in a continental interior desert, northwestern China
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中国西北部大陆内陆沙漠大气中大量硝酸盐积累
DOI：
10.1130/g32953.1
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发表时间：
2012-07-01
期刊：
影响因子：
5.8
通讯作者：
Zhang, Cheng
中科院分区：
文献类型：
--
作者：
Qin, Yan;Li, Yanhe;Zhang, Cheng
由于硝酸盐矿物的高溶解度，大规模的硝酸盐矿床在地球表面是罕见的。在极古老的（至1400万年）和极度干旱的沙漠，如智利北方的阿塔卡马沙漠，或南极洲的麦克默多干谷。在这两个地区的硝酸盐已被确定为源自大气氧化的氮氧化物。本文报道了中国西北部吐鲁番-哈密地区一种新型的块状大气硝酸盐存款，其资源量与阿塔卡马矿床相当。该存款的特点是：（1）位于大陆中心;（2）年龄年轻（3）一般富集在近地表而非深部;（4）干旱区氮和三重氧同位素组成的空间变异性很大，N-15的变化范围为0.7ppm ~ 27.6ppm，Δ O-18从千分之30.2到千分之46.7，Δ O-17从千分之5.9到千分之20.7。吐鲁番-哈密硝酸盐存款氮和三重氧同位素组成接近于莫哈韦沙漠（美国西南部）和阿塔卡马沙漠，表明（1）地球低中纬度（即，非极地地点）一直接受具有类似氮和三氧同位素组成的大气硝酸盐沉积;（2）硝酸盐沉积的局部或区域同位素差异可归因于沉积后过程，即干旱和相关微生物活动的差异。
Large-scale nitrate deposits are rare on Earth's surface due to the high solubility of nitrate minerals. Exceptions are found in extremely old (to 14 m.y.) and hyperarid deserts such as the Atacama Desert in northern Chile, or the McMurdo Dry Valleys in Antarctica. The nitrate in both of these regions has been determined to originate from atmospheric oxidation of NOx. Here we report a new type of massive atmospheric nitrate deposit, with resources equivalent to the Atacama deposits, in the Turpan-Hami area, northwestern China. This deposit is characterized by (1) a location in the center of a large continent; (2) young age (Pleistocene); (3) general enrichment near the surface rather than at depth; and (4) high spatial variability in the nitrogen and triple oxygen isotope composition within this arid region, the delta N-15 ranging from 0.7 parts per thousand to 27.6 parts per thousand, delta O-18 from 30.2 parts per thousand to 46.7 parts per thousand, and Delta O-17 from 5.9 parts per thousand to 20.7 parts per thousand. The Turpan-Hami nitrate deposit nitrogen and triple oxygen isotope composition is closely between those of the Mojave Desert (southwestern United States) and the Atacama Desert, suggesting that (1) Earth's low-middle latitudes (i.e., non-polar sites) have been receiving atmospheric nitrate deposition of similar nitrogen and triple oxygen isotope composition; and (2) local or regional isotope differences in nitrate deposits can be attributed to postdepositional processes, namely the difference in aridity and associated microbial activities.