大兴安岭北部霍拉盆地多年冻土及寒区环境研究的最新进展

霍拉盆地位于我国高纬度大片连续多年冻土区的北缘.盆地内的冻土具有自中心向边缘厚度变薄、温度升高,至四周山地出现融区等特征,同时又受局地因素如地形地貌、地表覆被、地下水赋存规律及地质构造等影响,冻土分布、厚度及温度的空间格局在遵从普遍规律的基础上又具有差异性.近年来,随着全球气候变暖及人为活动的逐步增强,盆地内冻土及寒区环境变化显著,对矿区转型至关重要的核心景观月牙湖几近干涸.2013年6月、2014年5-7月先后2次对霍拉盆地多年冻土及寒区环境变化进行科学考察并展开初步研究.在盆地内根据不同地貌、地表覆被及人为活动强度布设8个地温观测孔并将进行长期观测,以期分析研究人为活动、植被等局地因子对冻土的影响及未来冻土与寒区环境变化;同时,对干涸的月牙湖底地形、地貌进行了调查并采集湖相沉积物样品,以确定月牙湖的成因并进一步分析湖区气候及环境变迁;对月牙湖畔湖心岛地下冰再次进行勘察,发现厚层地下冰正在逐渐融化;此外,盆地内广泛发育的热喀斯特现象亦表明该区域冻土正在退化.

Recent progress in studying permafrost and cold regions' environment in the Hola basin of north Greater Khingan Mountains

Hola basin, an area belong to Mohe County of Heilongjiang Province, is located in the north Greater Khingan Mountains. The features of permafrost in the basin are that from the centre to the margin, the permafrost depth is becoming thinner, from 100-120 m to 10-20 m, and the mean annual ground temperature is becoming higher, from -2.9 ℃ to 0.5 ℃; talik occurs on the surrounding mountains only. The features are further complicated due to the effect of local geology, geography, coal thickness, groundwater and vegetation, and vary greatly even within a relatively small area. During the last few decades, permafrost and cold regions environment have been remarkably affected by climate warming and increasing of human activities. In view of this, a scientific expedition group from the State Key Laboratory of Frozen Soil Engineering, Chinese Academy of Sciences, had conducted two surveys (June 2013, May to July 2014) and corresponding fieldworks on permafrost environment in the Hola basin. The following result are obtained:Eight boreholes were drilled in the basin; to further analyze the formation mechanisms of lakes and understand the climatic and environmental changes in this area, soil samples were taken from hand-dug pits and wellbores of lake sediments down to 2.5 m. Through geological exploration, it is surmised that the massive ground ice is gradually melting; based on the investigation on the permafrost environment, it is found that a large number of thermokarst lakes are widespread in the Hola basin. Water samples were collected from lakes to analyze environmental isotopes, hydrogen and oxygen-18, and hydrochemistry composition.