不同类型建筑垃圾堆场大气降尘中水溶性离子污染特征

为了解建筑垃圾长期堆放产生的扬尘对大气的影响，选择北京市两个拆迁建筑垃圾堆放场，于2019年夏季、秋季进行降尘连续采样.共收集拆迁原地堆放有效降尘样品11个，异地集中堆放有效降尘样品11个，利用离子色谱法对大气降尘中水溶性离子组分及质量浓度进行分析.结果表明：阳离子中质量浓度最高的是Ca²⁺，其次是K⁺，NH₄⁺浓度最低；阴离子中质量浓度最高的是SO₄^2-，其次是Cl^-，NO₃^-最低，降尘样品呈碱性.建筑垃圾拆迁原地堆放场地Ca²⁺、Mg²⁺、SO₄^2-、Cl^-、Na⁺、NH₄⁺平均浓度高于异地集中堆放场地对应各离子浓度.拆迁原地堆放场地中Ca²⁺、SO₄^2-、Na⁺、Cl^-受局地风向影响较大，空间分布情况与风向扩散趋势大致相同；异地集中堆放场地各离子浓度高值区域分布较原地堆放远，Ca²⁺、K⁺、SO₄^2-、Cl^-、Mg²⁺这5种离子空间分布与次主导风向较为相符.同时，两个场地水溶性离子平均浓度与距建筑垃圾堆放地的距离有一定的关系，采样点在距堆放中心200 m范围之内离子平均浓度最大，总体来说，距离堆放中心近的采样点位离子浓度高于距离较远的采样点位离子浓度.

Pollution characteristics of water-soluble ions in atmospheric dustfall of different types of construction waste dumps

In order to understand the impact of the fugitive dust collected from long-term stacking construction waste, we selected two typical demolition construction waste dumps in Beijing and conducted dust fall sampling in the summer and autumn of 2019. A total of 11 effective dust samples stacked in-situ demolition were collected, and 11 effective dust samples densely stacked in different places were collected. The components and mass concentrations of the water-soluble ions in the samples were analyzed by using the ion chromatography. Our results showed that the highest mass concentrations of cation was Ca²⁺, followed by K⁺, and the lowest was NH₄⁺. The highest mass concentrations of anions was SO₄^2-, followed by Cl^-, and the lowest was NO₃^-. All collected samples were alkaline. The concentrations of Ca²⁺, Mg²⁺, SO₄^2-, Cl^-, Na⁺ and NH₄⁺ in the site of construction waste in-situ stacking demolition were higher than those in the site of centralized stacking in different places. Ca²⁺, SO₄^2-, Na⁺, Cl^- in the in-situ stacking demolition site were greatly affected by wind direction, and the spatial distribution were roughly the same as the wind diffusion direction. The high values of the ions concentration in the centralized stacking in different place were distributed more discretely than that of the in-situ stacking demolition, and the spatial distribution of the five ions of Ca²⁺, K⁺, SO₄^2-, Cl^-, and Mg²⁺ were more consistent with the sub-dominant wind direction. We also found that there was a clear relationship between the average concentration of the water-soluble ions and the distance from the construction waste dumping site. The average ion concentration was the largest within 200 meters from the stacking center. In general, the ion concentration at the sampling point closer to the stacking center was higher than the ion concentration at the farther sampling point.