This study quantifies surface denudation of carbonate rocks by the first application of in-situ cosmogenic36Cl in China. Concentrations of natural Cl and in-situ cosmogenic36Cl in bare carbonates from Guizhou karst areas were measured with isotope dilution by accelerator mass spectrometer. The Cl concentration varied from 16 to 206 ppm. The 36Cl concentrations were in range of (0.8-2.4)106 atom g-1 , resulting in total denudation rates of 20-50 mm ka-1 that averaged over a 104-105 a timescale. The 36Cl-denudation rates showed roughly a negative correlation with the local mean temperature. This preliminary observation may suggest the variations of proportions of chemical weathering and physical erosion in denudation process, depending upon local climatic conditions.
Methyl mercury(CH3Hg+),a neurotoxin,is the most toxic form of mercury that occurs in natural waters[1–4].It is a cause of concern because of increasing worldwide pollution by mercury in both water and atmosphere[3,5].Photodegradation of CH3Hg+is one of the main removal pathways from surface waters,and it has been shown
