基于改进灰靶的铁路弃渣场生态环境影响等级评价研究

弃渣场占用土地、破坏植被,易引发滑坡、泥石流和水土流失等自然灾害,对周边生态环境危害极大。近些年来,铁路弃渣场生态环境问题已成为铁路环境评价重点关注的问题之一,鉴于铁路施工自然环境复杂、线路长等特点,通过实地调研及查阅相关文献筛选出 15 项铁路弃渣场生态环境影响评价指标,并以此为基础划分等级标准,采用基于矩估计思想的组合权重确定各指标权重,提出运用改进灰靶模型在没有标准模型的情况下对弃渣场进行等级评价,确定各弃渣场对周边生态环境的影响程度,为后续弃渣场生态修复提供理论基础。以成兰铁路成都至川主寺（黄胜关）段沿线 10 座弃渣场为例进行验证,证明了采用组合权重的改进灰靶模型在此类问题研究中的可行性。     

Effect of ash disposal ponds on groundwater quality at a coal-fired power plant

The impact of fly and bottom ash disposal ponds on groundwater quality was investigated at the coal-fired Columbia Power Plant at Portage, Wis. Groundwater sampling was conducted utilizing a network of piezometers and multilevel wells located at various cross-sections of the ash disposal facility. Analyses were performed for 16 major and minor elements, pH and conductivity. Data for a 3-yr monitoring program established the existence of large B, Na and SO₄ plumes in the groundwater system surrounding the ash disposal area. Substantial amounts of B, Na and SO₄ were present in the plume and portions were discharged into an adjacent wetland as the plumes moved with groundwater flow. The secondary fly ash settling pond was the major source of B and SO₄, while the main source of Na was from previous releases to the aquifer from the use of Na₂CO₃ to condition fly ash to enhance removal of SO₂ from flue gas by electrostatic precipitation. Movement into the groundwater of heavy metals such as Cu and Zn was not observed and their concentrations are likely attenuated in the pond.