基于市政污泥的拓展型绿色屋顶基质的固碳潜力研究

Carbon sequestration potential on mixed sewage sludge as substrate on extensive green roofs

为提高固体废弃物资源化利用率,探索绿色屋顶基质的固碳能力,推广绿色屋顶的应用,研究选择混合污泥土(污泥与自然土等体积混合)和本地自然土作为绿色屋顶的种植基质,分别修建20 cm、25 cm和30 cm三个不同厚度的绿色屋顶,进行了一年的对比试验。结果表明:混合污泥土平均总碳含量较高,为(44.33±7.12)g·kg–1,平均总有机碳(36.02±6.03)g·kg–1高于自然土的总有机碳(19.64±4.3)g·kg–1。混合污泥土TC与TOC含量随土层深度的增加降低规律不明显,而自然土比较明显。混合污泥土的碳密度(13.15 kg·m–2)是本地自然土(8.58 kg·m–2)的1.53倍,一年的固碳量混合污泥土(3.81 kg·m–2)与自然土(3.89 kg·m–2)相当,两者的固碳能力都处于较高水平。可见混合污泥土是一种潜力较大的绿色屋顶种植基质。若将成都市34 km2没有绿化的屋顶面积的50%选择混合污泥土作为绿色屋顶基质进行推广应用,成都绿色屋顶基质每年将增加固碳6.48×107 kg,相当于每年减少CO2排放量2.38×108 kg,利用市政污泥2.125×106 m3(2.231×106 t),这将对成都市固体废弃物资源化利用和成都"世界现代田园城市"的建设起十分积极的作用。

Local-natural soil（LNS） and mixed-sewage-sludge soil（MSSS, equivalent volume of sewage sludge and LNS）, were selected to establish extensive green roof with three substrate depth of 20 cm, 25 cm and 30 cm from July 2012 to June 2013 in this study, in order to improve the reuse rate of solid waste, to investigate the carbon sequestration potential of green substrates and to expand the application of green roof. The results show that total carbon（TC） content of MSSS was（44.33 ± 7.12） g·kg–1 and total organic carbon（TOC） content of MSSS was（36.02 ± 6.03） g·kg–1 with a higher level than TOC content of LNS（19.64 ± 4.3） g·kg–1. It＇s found that TC and TOC content of MSSS was not obviously decreased with the increasing green roof substrate depth, while TC and TOC content of LNS significantly decreased with the increasing green roof substrate depth. Carbon density of MSSS（13.15 kg·m–2） was 1.53 times than LNS（8.58 kg·m–2）, while carbon sequestration of LNS（3.89 kg·m–2） was very close to that of MSSS（3.81 kg·m–2） in the one-year experiment. Both MSSS and LNS were in a high level of carbon sequestration. It＇s evident that MSSS should be considered as a kind of high potential green roof substrate. If 50 % of the none-greening roof areas（34 km2） will be applied in green roofs using MSSS as its substrate in Chengdu City, green roofs will sequestrate carbon 3.24×10^7 kg·a–1, equivalently reduce CO2 emission 1.19×10^8 kg·yr–1 and reuse sewage sludge 2.125×10^6 m3（2.231×10^6 t）, which will make a great contribution to improving the resource utilization of solid waste in Chengdu City and the construction of Chengdu World-class Modern Garden City.