北京市不同功能区土壤黑碳的含量特征及其来源分析

随着城市迅猛发展,城市土壤性质发生显著变化,不同功能区之间呈现明显差异性。为了深入讨论人为影响方式和程度、污染来源的差别对土壤碳库(特别是黑碳)的影响,本研究以北京市为对象,对比研究了城区和郊区不同功能区(公园、居民区、道路绿化带)土壤有机碳(SOC)含量、黑碳(BC)含量以及含量比值(BC/SOC)的特点,并通过BC/SOC指标对土壤受到的人类活动影响方式和程度进行详细讨论。结果显示,北京市城区不同功能区的土壤SOC富集程度不同,且公园和居民区土壤在人为管理下SOC含量趋于平均;而郊区不同功能区的SOC含量值接近,表明其受人为影响较小,更接近于自然土壤。城区不同功能区的土壤BC含量存在较大差异,由大到小是公园(0.60%~2.28%,平均值为1.56%)、道路绿化带(0.12%~2.20%,平均值为0.62%)、居民区(0.11%~1.15%,平均值为0.35%),其中公园内区域性的翻种、施肥使得BC大量聚集,道路绿化带受到来自交通环境的强烈影响;而郊区不同功能区的BC含量值低且接近,代表了区域土壤BC含量背景值。土壤BC/SOC总体介于0.11和0.5之间,且郊区BC/SOC小于城区,指示了化石燃料和生物质的燃烧均是城区和郊区土壤BC物质的来源,但所占比重不同,且城区是郊区土壤黑碳的重要来源。另外,城区个别地区BC/SOC显著偏高,反映了BC/SOC不但指示土壤污染程度,同时与城市化时间、特定的人类活动密切相关。

CONCENTRATION AND SOURCES OF BLACK CARBON IN DIFFERENT FUNCTION ZONES OF BEIJING, CHINA

With the rapid development of city, soil properties in city have changed significantly with significant differences among different function zones. In order to discuss the impact on the soil carbon pool (especially black carbon), from human activities of different ways and at different degrees as well as pollution from different sources, the concentration of black carbon (BC) and organic carbon (SOC), and concentration ratio (BC/SOC) of surface soil in different function zones (parks, residential areas and road green belt) in urban and suburban areas in Beijing are compared in the study, and the influence of human activities of different ways and at different degrees on soil are discussed based on the BC/SOC index. The results show that the enrichment degrees of soil SOC in different function zones in urban areas are different, and the concentration of SOC in soil in parks and residential areas under human management tend to be average; in suburban areas, the concentration of SOC in different function zones are close and much the same as the natural soil, indicating the soil is less influenced by human activities. There are significant differences in the concentration of BC values in soil in different function zones of urban areas, and the descending order is parks (0.60%~2.28%, mean 1.56%), road green belts (0.12%~2.20%, mean 0.62%), residential areas (0.11%~1.15%, mean 0.35%).The regional digging, planting and fertilization made a large number of BC gather in parks and road green belts are strongly impacted by traffic discharge; in suburban areas, the concentration of BC of different function zones are low and close to each other,representing the background concentration of BC in regional soil. The BC/SOC values in soil mainly fall in between 0.11% and 0.5%, and BC/SOC values in suburban area are smaller than that of urban areas, indicating that the burning of fossil fuels and biomass are both sources of BC in soil in the urban and suburban areas but with different proportions, and the urban area is an important source of BC in the suburban area. In addition, BC/SOC values in some places of urban areas are significantly higher, reflecting that BC/SOC value not only indicates the degree of soil pollution but also is closely related to urbanization progress and specific human activities.