北京市平原区裸露地风蚀扬尘排放量

Estimation of dust emissions from bare soil erosion over Beijing plain area

以北京市平原区为研究对象,基于美国国家航空航天局(NASA)的陆地卫星(Landsat系列)遥感资料,设计算法批量提取裸露地信息,并结合通用扬尘排放模型,计算估计北京市平原区的裸露地风蚀扬尘源中PM_(10)、PM_(2.5)的排放系数及年排放量,建立了北京市各区的裸露地风蚀扬尘排放清单.研究表明,1987~2016年间北京市平原区裸露地面积减小了约600km^2;风蚀扬尘最严重的地区为大兴区,其次为通州区;以气候年均值为参数计算获得,2016年北京平原区裸露地由于风蚀扬尘效应产生的PM_(10)年排放量为7591.7t,这一排放量与前人研究估算的北京裸地风蚀扬尘PM_(10)排放量较为接近.在此基础上,进一步引入月和季度尺度气候参数,并对模型进行改进,探讨了逐月和季度累计的扬尘排放结果.进一步的研究表明:北京市平原区裸露地面积具有显著季节变化特征,2月裸露地面积最大,可达4500km^2,8月最小为500km^2;基于月气候参数和季度气候参数结合每月卫星资料反演获得的裸地面积估算,逐月累计的PM_(10)年排放量可达55175t,分季度累计PM_(10)年排放量为39294t.这说明当前常采用的裸地扬尘估算方法,由于扬尘排放模型的气候参数采用年均值,忽视了风蚀过程的季节差异,将会导致裸地风蚀扬尘的极大低估.

Based on the remote sensing data of NASA Landsat satellite,an algorithm was designed to provide insights into the bare soil erosion over the plain area in Beijing.The PM10 and PM2.5 emission factors as well as the annual bareness wind erosion dust emissions were estimated for different districts in Beijing.As a result,the bare soil area of Beijing plain had reduced by about 600km2 between 1987 and 2016.Induced PM10 emissions by the wind erosion in Beijing plain were estimated of about 7591.7 tons in 2016,similar to the results reported by previous studies,with critical wind erosion in Daxing and Tongzhou Districts.However,significant seasonal variation of the bare soil erosion was indicated by further analysis of monthly and seasonal trends of meteorological parameters and bare soil area.The bare soil area data was derived from Landsat image,with a maximum of 4500km2 in February,and a minimum of 500km2 in August.With the improvement of the model,the monthly and quarterly cumulative emissions of PM10 was estimated to be 55175 tons and 39294 tons respectively.It’s suggested that existing bare soil dust estimation method,consisting of analysis of annual variation of meteorological parameters,seemed to neglect the seasonal discrepancies of wind erosion process,leading to a great underestimation of wind erosion dust emissions of bare soil.