哈尔滨2002年3月20日沙尘暴沉降物的粒度特征及其意义

哈尔滨2002年3月20日的沙尘沉降物以粉砂(4~63 μm)为主,占71.18%,砂粒组分(>63 μm)占 21.7%,粘土(<4 μm)组分含量最少,仅占7.13%。哈尔滨2002年3月20日沙尘沉降物的粒度是迄今为止有见报道中最粗的。沉降物粒度为多峰态分布,29.16~34.67μm粒级的粗粉砂组成第一主峰,含量约占7.4%,420.45~500 μm粒级的中砂组分组成第二主峰,含量约占1.29%,而0.69~0.82 μm粒级的细粘土组分形成第三主峰,含量约占0.52%。沉降物的平均粒径Mz为28.4 μm,分选系数为1.81,偏态为0.044,峰态为1.494,粉粘比为7.3。粒度特征显示,哈尔滨沙尘沉降物是不同来源沙尘远距离和近距离搬运的混合体,粗颗粒为低空气流搬运的近源物质。哈尔滨沙尘源区的生物状况和生态环境较为恶劣,该地区沙尘暴工作的重点应放在哈尔滨周边沙尘源区的治理上。

Grain Size Characteristic of Sand-dust Sedimentary in Harbin City and Its Implication

The collection and grain size analysis were carried out for sand dust sedimentation in Harbin, 20th March 2002. The result indicated that sand dust sedimentation gave priority to silt (4~8Φ), occupying 71.18%, sand composition (>4Φ) is 21.7% and clay composition (<8Φ)only 7.13% at Harbin. The granularity of sand dust sedimentation was the coarsest in the reports so far. The sedimentation granularity distribution was charactered by multi-peak states, coars sand silt of 4.85-5.10Φ grain grade composed first main peak, occupying about 7.4%, medium sand of 1-1.25Φ grain grade composed second main peak, occupying about 1,29%,and clay composition of 10.25-10.5Φ grain grade composed third main peak, occupying about 0.52%. The average grain diameters of sedimentation (Mz) was 5.14Φ, sorting coefficient, 1.81, Skewness, 0.044, and Kurtosis, 1.494, silt and clay ratios, 7.3. The granularity features shown that sand-dust sedimentation was admixture, derived from different sources both far distance and short distance, and coarse particle was near-sources material that was transmitted by low altitude airflow. The biology status and zoology environment of sand-dust sedimentation source area are relatively inclement. Nudity infield, wasteland and plain, river bed and floodplain fine alluvium, bareness lakes and dust of city earths surface and construction sites, and so on, may be material fountainhead. The keystone of weather projects for preventing sand-dust in Harbin should put to controlling sand-dust fountainhead around Harbin.