Knowledge Resource Center for Ecological Environment in Arid Area
| 中国北方粉尘气溶胶的矿物组成 | |
| 其他题名 | Mineralogical composition of dust aerosol in North China |
| 沈振兴 | |
| 出版年 | 2004 |
| 学位类型 | 博士 |
| 学位授予单位 | 中国科学院地球环境研究所 |
| 中文摘要 | 本文通过对位于中国北方沙漠源区阿克苏、敦煌、榆林、科尔沁和黄土高原沉降区长武共5个样点2001-2002年春季（3－5月）大气气溶胶矿物组成的研究；获得了亚洲粉尘关键区域气溶胶的矿物组成数据，进一步完善了亚洲粉尘的研究系统。根据不同样点大气气溶胶的矿物组成特征和沙漠表土矿物组成调查结果，划分出中国北方沙漠粉尘三个源区，并提取出亚洲粉尘源区辨别的矿物特征指标。分析显示，中国源区粉尘与西北太平洋粉尘气溶胶在粘粒组分的矿物组成上表现出较好的一致性，为西太平洋风成粉尘多来自亚洲粉尘源区提供了矿物组成的进一步证据。并对中国源区粉尘气溶胶的消光系数进行了初步估算。详细的结论如下：1建立了微量气溶胶样品的矿物分析方法。通过反复实验，建立了微量（毫克级）气溶胶样品的前处理方法，包括样品的分离、浓缩和制片。选择了适合微量样品的衍射制片载体（纯单晶硅片）对气溶胶样品进行了X射线衍射分析。实验结果显示，中国北方大气气溶胶主要组成矿物的衍射峰明显可辨，且强度较局。2首次利用漫反射光谱分析法对中国源区气溶胶中铁氧化物矿物进行了测定研究。光谱分析显示，气溶胶的反射光谱一阶导数曲线在435nm和560nm。对针铁矿和赤铁矿具有指示意义，且其一阶导数峰值与样品中铁浓度有很显著的相关性。研究发现，样品中铁浓度与针铁矿和赤铁矿的一阶导数峰值的大小随红色光波段。黄色光波段、橙色光波段的反射率增大而增大，呈正相关；而随紫色光波段。蓝色光波段、绿色光波段的反射率增大而减小，呈负相关。说明粉尘气溶胶中铁氧化物矿物的含量对样品的颜色（取决于样品对不同颜色反射率的高低）有重要的作用，且对可见光范围不同颜色（特别是红色和紫色）的吸收和反射有重要的影响。光谱分析还显示，不同区域亚洲粉尘的铁氧化物组成特征存在差异（通过hm／Gt来反映），亚洲粉尘与北大西洋粉尘的光谱分析结果有可比性，且亚洲粉尘与北大西洋粉尘的铁氧化物组成特征（Hm／Gt值）存在可分辨的差异。3对亚洲粉尘关键区域大气气溶胶的矿物组成特征进行了研究。大气气溶胶的矿物组成分析结果显示，同一样点尘暴粉尘相对\ |
| 英文摘要 | Mineralogical composition of Asian dust was investigated during spring 2001 and 2002 at five sites in North China: Aksu, Dunhuang, Yulin and Horqin, which located on desert regions, and another site Changwu, which located on the Loess Plateau. The Diffuse reflectance spectrometry is useful to identify the iron oxide in mineral dust and to assess their optical properties. Mineral dust at Aksu and Dunhuang are enriched of carbonate, and soil dust at Horqin is enriched of feldspar. Mineralogical composition of soil dust at Changwu on the depositional region is similar as dust at Yulin site, which the mineralogical composition is also different with Aksu, Dunhuang and Horqin site. There are three dust sources were identified based on the mineralogical characteristic of dust aerosols and surface soil samples. C/M (the ratio of calcite and muscovite) was proved to be a good signature for Asian dust derived from different part of Northern China. The data set of mineralogical composition of Asian dust can be used as the parameters for optical properties model. The following are some finding and conclusion. An improved XRD method for low mass (just several mg) atmospheric dust samples was set up. The XRD pattern of the low mass sample shows that peaks of major minerals of soil dust are clear and easy to identify. Diffuse reflectance spectrometry was used to investigate the iron oxide minerals and the reflectance characteristics of aerosol particles. The result shows that first derivatives of the spectra have signals for iron-oxide minerals, hematite and goethite, at 435 nm and 560 nm. First derivative values for hematite and goethite are strongly related to the iron concentration in the samples. The reflectivity of red, yellow and orange bands increased with increasing of iron concentration in the dust samples while the reflectivity of violet, blue and green bands are decreased with increasing of iron concentration. The results suggest that the iron oxide plays an important role in aerosols scattering and absorbing effects. The ratio of first derivatives characteristic values of hematite and goethite, which also reflects the ratio of hematite and goethite, are remarkable different between Asian dust and African dust. It indicates Hm/Gt can be used as a signature for dust from different source areas. 3 Soil dust is enriched of quartz and feldspar during dust storm events (DS), but are enriched of clay minerals during N-DS. The relative proportions of Muscovite and Quartz can reflect the variety of the wind speed and the variety of the aerosols size distribution. Soil dust at Aksu and Dunhuang is enriched of carbonate, and the relative content of calcite is ～10%. Dust at Horqin is enriched of feldspar and lower carbonate, and the relative content of Plagioclase feldspar and calcite are ～15%, ～1%. The relative content of calcite and plagioclase feldspar of eolian dust at Yulin is ～4% and ～7%, which can be discriminate with dust at other sites. Comparing with mineral composition of dust at source areas, soil dust at depositional regions is relative enriched of clay minerals. Lower wind speed during DS and long distance transport is proper to the coarse size particles subsiding. Mineral composition of the < 2 um size fraction of soil dust are similar in different regions, and are also identical with the dust at Northwest Pacific. This proves that Asian dust is the major source of the dust at Northwest Pacific. The fine size particles play an important role in climate forcing for their long atmospheric residence times and long distance transport ability. 4 Three dust sources were identified based on the mineralogical characteristic of soil dust and surface soil samples. Dusts originated from the Western source regions, which can represent by Aksu and Dunhuang, are enriched of carbonate. Dusts at Northeast source areas, which can represent by Horqin, are enriched of feldspar. Dusts at Yulin can represent mineralogical characteristics of Northern source area. C/M (the ratio of calcite and muscovite) was proved to be a good signature for Asian dust derived from different part of Northern China. 5 Incorporated of mineralogical composition into optical properties model, extinction coefficient of clay size particles was calculated. The results show that extinction coefficient of mineral dust increased with increasing of mass concentration when the size distribution is unchanged. But when the mass concentration was unchanged, the extinction coefficient decreased with increasing of mean diameter. It suggests that fine size particle plays an important role in aerosols optical properties. |
| 中文关键词 | 粉尘气溶胶 ; 漫反射光谱分析 ; 矿物组成 ; 源区示踪 ; 光学性质 |
| 英文关键词 | mineral dust iron oxide mineralogical composition source signature optical properties |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源机构 | 中国科学院地球环境研究所 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/286348 |
| 推荐引用方式 GB/T 7714 | 沈振兴. 中国北方粉尘气溶胶的矿物组成[D]. 中国科学院地球环境研究所,2004. |
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