哈尔滨沙尘沉降物稀土元素地球化学特征及其物源分析

为了对哈尔滨沙尘天气的物质来源进行追踪, 对哈尔滨沙尘沉降物及其作为潜在源区的科尔沁沙地和松嫩沙地(＜11 μm和11~30 μm粒级组分)进行了稀土元素分布特征的研究.结果表明: 哈尔滨2002年沙尘物质的∑REE为189.67×10-6, 2007年为175.57×10-6, 2008年为174.68×10-6, 2011年为181.35×10-6.沙尘沉降物的REE集中分布在一个很窄的范围, 显示哈尔滨沙尘的来源相当稳定.沙尘沉降物的稀土元素分布模式十分相似, Eu较明显亏损(2002年、2007年以及2008年沙尘的δEu在0.71~0.75之间, 2011年沙尘的δEu值为0.92), Ce弱负异常(δCe值在0.89~0.92之间, 平均值为0.90).沙尘沉降物与潜在源区物质的REE含量、分布模式、特征参数以及δEu-ΣREEs、δEu-(LREE/HREE)和(LREE/HREE)-La_N关系图解均显示哈尔滨沙尘沉降物的REE组成与科尔沁沙地(特别是11~30 μm粒级组分)十分接近, 显示哈尔滨沙尘起源于科尔沁沙地而非松嫩沙地, 科尔沁沙地对哈尔滨沙尘的物质贡献主要体现在11~30 μm粒级组分.哈尔滨沙尘的科尔沁沙地起源的研究结果得到气象资料和气象记录的支持. 

REE Geochemistry for Sand-Dust Fallouts in Harbin,Heilongjiang Province and Provenance Analysis

To determine provenance of sand-dust fallouts in Harbin area, Heilongjiang Province, the sand-dust fallouts in Harbin and two different grain size fractions (< 11 μm and 11-30 μm) of samples from the potential source areas, including Horqin sandy land and Songneng sandy land, are studied for rare earth element (REE) compositions. The results indicate that ΣREE for sand-dust fallouts in 2002 ranges from 179.07×10-6 to 200.92×10-6 with an average value of 189.67×10-6, ΣREE varied ranges from 166.70×10-6 to 184.44×10-6 with an average value of 175.57×10-6 for sand-dust fallouts in 2007, from 166.91×10-6 to 182.45×10-6 with an average value of 174.68×10-6 in 2008, ΣREE in 2011 is 181.35×10-6. The REE distribution for all sand-dust fallouts focuses on very narrow scopes, which displays provenance for sand-dust fallouts in Harbin is very stable. The dust falls show very similar REE distribution patterns and characteristic parameters with distinct negative Eu anomalies (δEu value for dust falls in 2002, 2007, 2008 varied from 0.71 to 0.75, δEu value in 2011 was 0.92) and slightly negative Ce anomalies (δCe value was in the range from 0.89 to 0.92 with an average of 0.90). The relatively large amount of evidence, such as REE values and distribution patterns and characteristic parameters and δEu vs. ΣREEs diagram and δEu vs. (LREE/HREE) diagram and (LREE/HREE) vs. La_N diagram, indicate that REE compositions for dust falls in Harbin are quite similar to those of Horqin sandy land (specially 11-30 μm grain size fractions), showing sand-dust in Harbin stems from Horqin sandy land but not Songneng sandy land, and showing material contribution of Horqin sandy land to dust falls in Harbin is mainly 11-30 μm grain-size fractions. It is confirmed that dust falls in Harbin are from Horqin sandy land by relevant meteorological records and meteorological data.