Study on the CaCO_3 Content Characteristics in Conterminous Region of Beijing,Tianjin and Hebei

Based on grid(10 km×10 km) investigation and sampling on contiguous region of Beijing,Tianjin and Hebei Province,the contents of CaCO3 in the topsoils were determined using the gas-volumetric method.The spatial distribution of CaCO3 contents in the study area was analyzed by using the GIS Kriging interpolation,as well as overlaying with geomorphological type,average annual precipitation,and soil type maps.The results show: 1) The contents of CaCO3 in the topsoils in the study area range from 10 to 110 g/kg,and are distinctly higher than those of the northeastern region of the United States,which might restrain the activity of heavy metals.2) Very few CaCO3 is partly found in the topsoils of mountain Brown soil and eluvial Cinnamon soils.3) The spatial distribution of CaCO3 contents in the study area is as follows: the most CaCO3 contents exist in the Seashore Saline Soils located on Ziya New River Alluvial Plain in the southeast of the study area,as well as the Carbanate Cinnamon soils and the Aquic Cinnamon soils evolved from mother materials of limestone and eolian loess located on the northwestern Huailai Basin and Piedmont;there are relatively less CaCO3 contents in the Cinnamon soils and eluviated Cinnamon soils developed on the southern piedmont of northern Yan Mountain,as well as the Fluro-aquic soils developed on the alluvial plain of the southeastern Yongding River;the least CaCO3 contents present in the Fluro-aquic soils developed on the central Chaobai River Alluvial Plain,together with the mountain Brown soils and Alpine meadow soils developed on the middle and upper place of the western Taihang Mountain and the northeastern Yan Mountain.4) The geomorphological type plays a primary role in controlling the distribution of CaCO3 contents in the topsoils.Also,the human activities impact strongly on the CaCO3 content in topsoils of the study area.