城市生活垃圾露天焚烧PM2.5及其组分排放特征

利用稀释采样系统,针对桶内燃烧和自然堆积两种常见露天焚烧方式,分别对橡塑类、纸类和木竹类这3种组分生活垃圾露天焚烧PM_(2.5)排放特征进行实测,计算PM_(2.5)、OC、EC、水溶性离子和无机元素排放因子.结果表明,木竹类生活垃圾PM_(2.5)排放因子(7.44±0.76)g·kg~(-1)最高,纸类PM_(2.5)排放因子(2.72±0.52)g·kg~(-1)最低.桶内燃烧的条件会造成更多污染物排放.在不同的燃烧方式下,橡塑类和纸类生活垃圾在桶内燃烧的条件下PM_(2.5)排放因子是自然堆积燃烧的2.5~3.5倍.PM_(2.5)中OC和EC为主要组成成分,PM_(2.5)组分构成占比约为46.6%~67.2%.不同垃圾组分OC/EC比率差异较大,但该比率受焚烧条件影响较小,有助于解析不同组分垃圾焚烧排放贡献.水溶性离子中NH+4离子、Cl-离子含量最高,在PM_(2.5)中所占比例范围分别为2.28%~6.35%和1.04%~14.31%.无机元素中Ca、K、Fe和Ba元素排放因子较高.重金属元素中Zn元素排放因子最高,Cu、Cr、Sb和Pb等元素也有一定富集.Zn元素含量主要由燃烧方式决定,桶内燃烧大约是自然堆积燃烧的20倍左右.

Emission Characteristics and Chemical Components of PM2.5 from Open Burning of Municipal Solid Waste

Source emission measurements were employed to investigate open burning of municipal solid waste (MSW). Both barrel and natural pile-up burning of MSW were investigated using a self-designed dilution sampling system. PM_2.5 was collected for three types of waste, including rubber and plastic, paper, and wood and bamboo. Then, components in the samples were analyzed and emission factors of PM_2.5, organic carbon (OC), elemental carbon (EC), water-soluble ions and inorganic elements were calculated. The PM_2.5 emission factor was highest for wood and bamboo, and lowest for paper, and was calculated to be (7.44±0.76) g·kg^-1 and (2.72±0.52) g·kg^-1, respectively. Barrel burning resulted in much higher pollutant emissions. The PM_2.5 emission factor for barrel burning was 2.5-3.5 times that of natural pile-up burning. OC and EC were the main components of PM_2.5, with a proportion of 46.6%-67.2%. MSW composition had a greater effect on the OC/EC ratios than burning mode. The ratios could be helpful in the analysis of the emission contributions of different MSW components. The proportions of NH₄⁺ and Cl^- were the highest in water-soluble ions, accounting for 2.28%-6.35% and 1.04%-14.31%, respectively. Among inorganic elements, Ca, K, Fe, and Ba showed high emission factors. The emission factor of Zn was the highest among heavy metals, and other elements such as Cu, Cr, Sb, and Pb were also enriched. Zn emission was mainly determined by the burning mode; emissions from barrel combustion were approximately 20 times more than that of natural pile-up burning.