硝酸盐矿物是自然界溶解度最大的盐类矿物之一,是极端干旱气候条件下从卤水中蒸发析出的产物,在新疆罗布泊等地出现了多处硝酸盐富集区.目前,新疆的硝酸盐矿层主要发现于全新统,反映出该地区在晚更新世末一全新世时期出现了极端干旱气候条件.根据沉积物地球化学分析,发现罗布泊等硝酸盐富集区出现有硝酸盐矿物沉积,其孔隙和晶间卤水的硝酸根含量很高,同时,沉积物也富含Fe、Ti、Cr、Mn、Cu等重金属元素.为此,将这些重金属元素作为催化剂,设计了4组光化学反应试验,通过野外实地与室内模拟金属催化一光化学反应试验产生了硝酸根离子.因此,本研究认为,干旱区的硝酸根离子的来源与金属的催化-光化学反应有密切的关系,提出了Ti等金属催化-光化学反应是新疆干旱区内硝酸盐形成的主要机制.%There are several nitrates-enriched areas in the arid region of Xinjiang. These nitrates are formed from brine by evaporation. The nitrate-bearing beds were mainly discovered in Hollocene strata. Studies show that nitrate minerals occur in nitrate-bearing sediments, that brine strata are enriched with nitrate radical, and that Fe, Ti, Cr, Mn, Cu and some other elements are also relatively abundant in the sediments. To probe into the relationship between metals and nitrate radical formation, the authors designed four experiments in which, TiO_2, Cr_2O_3,CuO and Fe_2O_3 act as catalysts. Field and indoor photochemical reaction experiments show that the TiO_2 and Cr_2O_3-catalyst reactions produce relatively high content of nitrate radical, and the TiO_2-catalyst reaction has the best effect in all reactions. Other mechanisms, such as biogenie and atmospheric mechanisms, are unsuitable for nitrate formation in the arid region. It is thus held that the TiO_2-catalyst reaction may be the main mechanism for the formation of nitrates in Xinjiang.
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