典型岩溶槽谷区土壤CO2浓度变化对隧道建设的响应——以重庆市中梁山岩溶槽谷为例

Change in soil CO2 concentration due to tunnel construction in a typical karst valley: A case study of Zhongliang Mountain, Chongqing City

为了解重庆市中梁山岩溶槽谷区隧道建设对土壤CO2浓度变化特征的影响,于2017年12月1日至2018年11月25日对中梁山岩溶槽谷区的隧道影响区和非隧道影响区典型的白蜡树林(FC)和于2017年3月22日-2018年1月18日对耕地(CU)、灌丛(SH)、竹林(BA)下土壤CO2浓度及其相关的环境因子进行研究,探讨了隧道影响和非隧道影响的岩溶区土壤CO2浓度变化规律及其影响因子。研究表明:隧道影响区(A区)土壤CO2浓度低于非隧道影响区(B区),A区A-CU、A-SH、A-BA和A-FC土壤CO2浓度的平均值分别为4479.26、6053.10、8152.70 mg/m3和17162.47 mg/m3,B区B-CU、B-SH、B-BA和B-FC分别为6244.67、6647.01、9422.94 mg/m3和18396.09 mg/m3。但隧道影响区和非隧道影响区的土壤CO2浓度具有相同的垂直和季节变化趋势,在垂直方向上,土壤CO2浓度随土壤深度的增加而增加,在季节变化上,雨季(夏季和秋季)土壤CO2浓度大于旱季(冬季和春季)。经相关分析发现土壤温度是影响土壤CO2浓度变化的主控因子,土壤CO2浓度随土壤温度的升高而升高,降水较多时土壤含水率过高,会抑制土壤CO2的生产,同时,土壤理化性质也对土壤CO2浓度具有一定的影响。隧道影响区土壤CO2浓度的变化受外界环境变化的影响大。

To understand the effect of tunnel construction in a karst ridge-trough area(Zhongliang Mountain, Beibei District, Chongqing) on the characteristics of the soil CO2 concentration, we analyzed the soil CO2 concentration and environmental factors of Fraxinus chinensis(FC) at 0-20 cm and 20-40 cm in tunnel affected and non-tunnel affected areas from December 1, 2017 to November 25, 2018. In addition, the soil CO2 concentration and its related environmental factors under cultivated land(CU), shrub(SH), and bamboo forest(BA) were studied from March 22, 2017 to January 18, 2018 to discuss the variation of the soil CO2 concentration in karst areas affected and not affected by the tunnel. The results showed that(1) the average values for the soil CO2 concentrations of A-CU, A-SH, A-BA, and A-FC in area A(tunnel affected area) were 4479.26 mg/m3, 6053.10 mg/m3, 8152.70 mg/m3, and 17162.47 mg/m3, respectively, and those of B-CU, B-SH, B-BA, and B-FC in area B(non-tunnel affected area) were 6244.67 mg/m3, 6647.01 mg/m3, 9422.94 mg/m3, and 18396.09 mg/m3, respectively. The soil CO2 concentration in the tunnel affected area was lower than that in the non-tunnel affected area.(2) However, the soil CO2 concentration in the tunnel affected and non-tunnel affected areas had the same vertical and seasonal variation trends: in the vertical change, the soil CO2 concentration increased with increase in soil depth, and in the seasonal change, the soil CO2 concentration in the rainy season(summer and autumn) was greater than that in the dry season(winter and spring).(3) Correlation analysis showed that the soil temperature was the main controlling factor affecting the soil CO2 concentration. Additionally, the soil CO2 concentration increased with the soil temperature, except during the rainy season, where the soil moisture inhibited the production of CO2 in the soil. Moreover, the soil physical and chemical properties could also affect the soil CO2 concentration.(4) Finally, the changes in the soil CO2 concentration in the tunnel affected areas were more susceptible to changes in the external environment.