不同粒级组分碳酸盐与碳同位素分布特征及其对风尘物源的指示意义  

Distributional Characteristics of Carbonate and Carbon Isotopic Compositions in Different Grain-size Fractions and Their Implications for Dust Provenance

作　　者：谢远云[1] 康春国[2] 孟杰[1] 郭令芬[1] 何葵[1] 

机构地区：[1]哈尔滨师范大学地理科学学院,哈尔滨150025 [2]哈尔滨学院地理系,哈尔滨150086

出　　处：《沉积学报》2013年第3期468-477,共10页Acta Sedimentologica Sinica

基　　金：国家自然科学基金项目(批准号:41072259);黑龙江省自然科学基金项目(G201027)资助

摘　　要：在科尔沁沙地采集沙地表土样品16组,松嫩平原杜蒙沙地样品15组,同期还收集了城市道路表土样品10组,对各组样品进行粒度分级(全样、>63μm、63～30μm、30～11μm和<11μm),分别测定碳酸盐含量和碳同位素组成。结果显示,不同区域不同性质样品各粒级组分碳酸盐含量的变化幅度不同,科尔沁沙地最小(0.8%),其次为杜蒙沙地(1.9%),道路表土最大(2.7%)。大部分杜蒙沙地样品(66.7%)和小部分科尔沁沙地样品(37.5%)以及全部道路表土样品的碳酸盐含量随粒度变细而增大,且变化模式各不相同。碳酸盐含量随粒度变细而增高是非匀速的,先是增幅较大(>63μm→63～30μm→30～11μm),后增幅较小(30～11μm→<11μm)。沙地样品碳酸盐含量与粒度的关系并不限于随粒度变细而增大这一种,风成砂和经历过强烈成壤作用改造的沙地样品中的碳酸盐含量与粒度的关系皆表现为随粒度变细而减小,沉积物中碳酸盐含量随粒径变细而增高是否是一种普遍规律还需要更多区域的更多样品来检验。大部分沙地样品和道路表土样品不同粒级组分的碳酸盐δ13C值变化范围较小(<1.8‰),并表现出随粒度变细而趋于偏正的特征,但变化幅度很小。杜蒙沙地和科尔沁沙地碳酸盐含量的地区差异性极不明显,且各粒级组分碳酸盐含量的变化幅度大大超过了杜蒙沙地与科尔沁沙地的碳酸盐差异值,不能作为区分杜蒙沙地和科尔沁沙地风尘源区的示踪指标;而科尔沁沙地和杜蒙沙地碳酸盐δ13C组成存在明显差异(在63～30μm粒级组分表现最为明显),且不同粒级组分碳酸盐δ13C值差别较小,说明它是一个比碳酸盐含量更好的风尘源区示踪指标,但是不同粒级组分碳酸盐δ13C组成的差异会随离中国西部沙漠沙地风尘源区距离的加大或者风尘物质成壤作用的增强而变大,增加其风尘源区示踪的复杂性。Carbonate and its carbon isotopes have the potential for distinguishing dust provenance, and but the differ- ences for carbonate and carbon isotopes in different grain-size fractions significantly affect accuracy for identifying dust provenance. Therefore, the study for distribution characteristic of carbonate and carbon isotopes in different giain-size fractions is theory base of dust provenance trace with use of carbonate and carbon isotopes. Samples of sandy land have be collected from horqin sandy land and dumeng sandy land in songnen plain, at one time, samples also are col- lected from city road loose bare soils. These samples are separated into five different grain size fractions, i. e. bulk sample, 〉 63 μm, 63 - 30 μm, 30 - 11 μm, and 〈 11 μm. Then, carbonate volume and carbon isotopic composi- tions of these samples are measured, respectively. The results show that the varied range of carbonate volume of differ- ent grain size fractions in horqin sandy land and dumeng sandy land are fairly minor, although carbonate volume of most samples raise with decreasing grain size, but relations between carbonate volume and grain size are not only a re- lations that carbonate volume becomes high with decreasing grain size, but also have other much complex relations. The carbonate volume of all road loose bare soils increases with decreasing grain size, and might be caused by join of fine grain-sized pollutants such as construction dust. The carbonate volumes of full fractions are similar to that of the 〉 63 μm fraction. It is believed that the carbonate volume of eolian sand and sand-land samples undergoing transform of violent pedogenesis decreases with decreasing size of sample panicles. The varied scopes of carbon isotopic compo-sitions of different grain size fractions of most samples in dumeng sandy land and road loose bare soils and all samples in Horqin sandy land are fairly minor, and express the characteristics of increase with decreasing grain size, but the varied changes are very slight. The c

关 键 词：碳酸盐 碳酸盐碳同位素 分粒级组分 科尔沁沙地 杜蒙沙地 风尘物源示踪 

分 类 号：P534.63[天文地球—第四纪地质学]