Element Geochemical Characteristics Of Suspended Matters And Sediments In A Small Watershed Of The Central Guizhou Province And Their Weathering Implication

South China has high weathering erosion rate, it is the most abundant area of the surface material from land to ocean. Based on the broad karst area, southwest China has become the important area about geochemistry especially chemical weathering research. Guizhou province is the central karst areas of southwest China; with extensive exposed carbonate, weak ecological system, and human activity intensify its erosion speed. In this paper, we take a small watershed of central Guizhou province as the research object. Based on its water chemical characteristics, we analyzed systematically the geochemical characteristics trace elements and REEs in suspended matters and sediments, discussed control factors and their provenance implications, meanwhile revealed the weathering features in small watershed of karst area.Stoichiometric analysis show ions components mainly come from the weathering process of carbonates, evaporates and silicate. The result showed that89.0%of riverine cations were originated from the carbonate,7.01%from the evaporite and the other3.99%from silicate. Chemistry weathering rate was approximately53.77t/km2·a, CO2consumption flux was14.1×108mol/a, compared with the1980s, it has increased nearly two times; Increased about34.67%with2005.This indicated there were high weathering rate in this area, furthermore gradually increased in recent years, which related to lithology, climate, vegetation coverage and unreasonable human activities.The concentrations of trace elements were different between rivers and lakes, also between suspended and sediment phases. However, the UCC-normalized curve of all the samples were in accordance with the samples of Pingba profile; and all the sample had the trend along with the weathering line, which indicated that suspended matters and sediments were both origin from weathering products of sedimentary rocks in the small watershed of central Guizhou province.Four main factors were extracted from element factor analysis. Factor1of elements combination were∑REE、Y、Zr、Nb、Hf、Ta and U, represented the saprolite source of original rock weathering; factor2of elements combination were Rb、Cs、Tl and Th, represented terrigenous fragmental materials; factor3of elements combination were Co、Ni and Cu, represented the sources from industrial production; factor4of elements combination were Cr and Zn, represented the pollutants of mining industry.Chondrite-normalized curves of REE of rivers and lakes, suspended and sediments were rich in light REE obviously. Due to the influence of coal mine, the distribution patterns of REE in Maiweng river were unusua. All the samples showed positive Gd-anomalies, which was controlled by the source rocks and mineral type, such as protogenous Fe-Mn oxide minerals and apatite. In addition, the human pollutant might make Gd anomaly.NASC-normalized REE distribution patterns were flat approximately to light REE enriched, with slight anomalies for Eu and Ce.∑REE and pH revealed a negative correlation in suspended matters, while a positive correlation in sediments. This indicated suspended matters and sediments had different control factors.This research would lead to a better grasp of hydrological geochemistry research in karst area, and revealed the element characteristics and material conveying status in chemical weathering and physical erosion processes in the small watershed, provide scientific basis for environment situation, governance and economic development for karst ecological fragile regions in China, situation, governance and management.