Particle number size distribution from 10 to 10,000 nm was measured by a wide-range particle spectrometer (WPS-1000XP) at a downwind site north of downtown Lanzhou, western China, from 25 June to 19 July 2006. We first report the pollution level, diurnal variation of particle concentration in different size ranges and then introduce the characteristics of the particle formation processes, to show that the number concentration of ultrafine particles was lower than the values measured in other urban or suburban areas in previous studies. However, the fraction of ultrafine particles in total aerosol number concentration was found to be much higher. Furthermore, sharp increase of ultrafine particle concentration was frequently observed at noon. An examination of the diurnal pattern suggests that the burst of the ultrafine particles was mainly due to nucleation process. During the 25-day observation, new particle formation (NPF) from homogeneous nucleation was observed during 33% of the study period. The average growth rate of the newly formed particles was 4.4 nm/h, varying from 1.3 to 16.9 nm/h. The needed concentration of condensable vapor was 6.1 × 107 cmfi3, and its source rate was 1.1 × 106 cmfi3 sfi1. Further calculation on the source rate of sulphuric acid vapor indicated that the average participation of sulphuric acid to particle growth rate was 68.3%.
分布式流域水文模型SWAT(Soil and Water Assessment Tool)在土地利用/覆盖变化的水文响应研究领域得到了广泛运用,利用紫坪铺站与沙坝站实测流量数据对模型进行校准与验证。紫坪铺站校准期与验证期的ENS值分别为0.74、0.66,沙坝水文站校准期与验证期的ENS值分别为0.66、0.61。在黑水河下游流域建立三种干旱河谷扩大的情景模式,利用率定好的参数,模拟1978-1987年气象条件下的水文响应特征,结果显示干旱河谷区面积扩大导致径流输出值减小,同时引起蒸散发的增加,径流与蒸散发存在显著的负相关性。
