湖南大龙洞流域不同岩性不同土地利用类型条件下碳酸盐岩试片的溶蚀速率

摘要

选择湖南大龙洞流域寒武系中统熬溪组上段(∈2a3)白云岩、寒武系上统比条组下段(∈3b1)和奥陶系中统牯牛潭组(O2g)灰岩进行野外溶蚀试验,并测试林地和草地类型土壤剖面20 cm、50 cm深度土壤CO2浓度和有机质含量,以探讨林地、草地土地利用类型条件下试片溶蚀速率的差异特征.结果表明:(1)O2g、∈3b1和∈2a3 3种试片溶蚀速率在林地和草地土下20 cm、50 cm深度差异明显,∈3b1g灰岩林地土下20 cm试片的溶蚀速率最大,达357.93 mg/(m2·d)；(2)试片溶蚀速率受岩性影响明显,CaO 含量高,溶蚀速率大,O2g、∈3b1灰岩中CaO 含量分别为35.38％、47.45％,较∈2a3白云岩的含量32.64％高,因而其溶蚀速率也较∈2a3的大；(3)埋放于林地土壤的试片其溶蚀速率大于草地,表明土地类型对溶蚀速率有较大的影响,植被从草地向林地的正向演替有利于岩溶作用的进行.%In order to discuss the differences of corrosion rates between the forcstland and the grassland, tablets made of the Aoxi group dolomite(∈2a3) and the Bitiao group limestone(∈3b1) as well as the Guniutan group limestone(O2g)are used to test the soil CO2 concentration and organic content at 20 cm and 50 cm deep on soil profile in the Dalongdong basin, Hunan. It is concluded that, (1) the corrosion rates among the three tablets are quite different both under the forestland and the grassland at 20 cm and 50 cm deep on the soil profile with the ∈3b1 tablet the largest; (2) corrosion rates are affected obviously by lithology, the higher the CaO content the larger the corrosion rate, so the fewest the ∈2a3 tablet in CaO content(32. 64 %), the smallest the corrosion rate of the ∈2a3 tablet; (3) the corrosion rate is larger under forestland than that under grassland, which proving the land type is of effect on corrosion rate. It will be benefit to karstification if the vegetation successes consequently towards forest from grass.