中国西部河谷型城市土壤与灰尘粒级组分分布特征

Spatial distribution of particle fractionations of dust and soil in the valley-city of northwest China

通过采集兰州市和延安市主城区的土壤灰尘样品,测量了其粒径组成,界定了土壤和灰尘不同粒径的空间分布,分析了环境影响。结果表明:兰州市和延安市城市土壤灰尘粒径组成有明显的分布特征,主要集中在小于100μm的部分,整体粒径分布情况为:粉黏粒(<50μm)>极细砂(50~100μm)>细砂(100~250μm)>中砂(250~500μm)>粗砂(500~1000μm)。其中兰州市小于100μm灰尘颗粒物粒径所占比例(69.17%)大于延安市(53.49%),极易在外动力条件下再次扬起成为扬尘污染的潜在污染源。从2个城市土壤和灰尘<PM10粒径组分空间分布特征来看,同粒度的上风向城市土壤是同粒度下风向的城市灰尘的潜在来源,工业活动对土壤小粒径组分的影响可能更大,频繁的人类活动对灰尘小粒径组分的影响可能更大。

Both Lanzhou and Yan’an are valley cities in northwest China that are critical for the petrochemical industry and energy and have frequent dusty weather.The fine particles and dust in the soil easily enter the atmosphere and cause haze pollution.However,basic data,such as urban soil characteristics and dust particle size in this area are lacking.This study collected soil and dust samples in the main urban area of Lanzhou and Yan’an.The particle size composition was measured using a laser particle size analyzer.The environmental effects were analyzed through spatial distribution and particle size of soil and dust.We provide scientific data and a theoretical basis for the urban environmental protection in Lanzhou and Yan’an.The results show that the principal size fractions of soil and dust in Lanzhou and Yan’an were no more than 100μm.The overall grain size distribution trend decreased as silty clay(<50μm)>impalpable sand(50-100μm)>fine sand(100-250μm)>medium sand(250-500μm)>coarse medium sand(500-1000μm).The proportion of dust particle size less than 100μm in Lanzhou is 69.17%,which was larger than in Yan’an(53.49%).The results indicate that the fractionation in dust of less than 100μm was easy to increase under an external power condition and become the potential source of pollution and human health risk.The results of spatial distributions of PM1,PM2.5,and PM10 in soil and dust showed that the same size of urban soil in the upper wind direction was a source of urban dust under the same size wind direction.Furthermore,industrial activities significantly influence small-sized soils,and frequent human activities significantly influence small-sized dust.Correlation analysis was conducted using Spass 21 software on a proportion of different particle levels between soil dust in Lanzhou and Yan’an,respectively.A significant correlation exists between different soil and dust particle levels in Lanzhou,with a correlation coefficient of r=0.967,which is a strong correlation.A significant correlation also exists between soil and dust in Yan’an,with r=0.767,indicating that soil fine particles might partly contribute to dust.