Atmospheric dispersion modeling near a roadway under calm meteorological conditions

Atmospheric pollutant dispersion near sources is typically simulated by Gaussian models because of their efficient compromise between reasonable accuracy and manageable computational time. However, the standard Gaussian dispersion formula applies downwind of a source under advective conditions with a well-defined wind direction and cannot calculate air pollutant concentrations under calm conditions with fluctuating wind direction and/or upwind of the emission source. Attempts have been made to address atmospheric dispersion under such conditions. This work evaluates the performance of standard and modified Gaussian plume models using measurements of NO₂, PM₁₀, PM_2.5, five inorganic ions and seven metals conducted near a freeway in Grenoble, France, during 11–27 September 2011. The formulation for calm conditions significantly improves model performance. However, it appears that atmospheric dispersion due to vehicle-induced turbulence is still underestimated. Furthermore, model performance is poor for particulate species unless road dust resuspension by traffic is explicitly taken into account.     

洋口港航道骤淤的可能性分析

利用“9711”台风浪实测资料,计算了洋口港航道所在海区在“9711”台风浪作用下床沙的悬浮上扬过程,得出洋口港航道不具备骤淤的可能性。     

关于长江口深水航道维护条件与流域来水来沙关系的初步分析

长江口深水航道一、二期工程建成后，航道回淤量得到了控制。分析其原因，长江流域进入河口的泥沙近十多年来明显减少，但河口水体含沙量并未减少。河口下段由于存在明显的泥沙再悬浮过程，泥沙活动总量远大于流域来沙量。因此，在一定时期内，流域来沙减少不会显著改善航道的维护条件。另一方面，河相关系分析和实测地形资料表明，近十多年来长江口内沙洲面积持续减少，分析认为应与流域来沙减少和变细有关。一段时期内，河床演变趋于活跃，增加了泥沙活动，对航道维护有不利影响。     

Bioresuspension and biodeposition: a review

The present literature on biologically mediated fluxes from the benthic nepheloid layer (BNL) across the sediment-water interface into the sediment and vice versa is reviewed. The processes involved are categorised according to direct bioresuspension and biodeposition, i.e. direct interception of the animal with particles, and those effects, which are indirectly created by benthic organisms, e.g., changes of physical properties in the sediments, constructions like tubes and pits and the corresponding changes in hydrodynamic conditions. It is concluded that benthic organisms significantly increase the flux of particles across the interface and that the physically created fluxes are easily modified by a factor of 2 and more.