ZOU Xiaogang1,2, YANG Yan1,2, XU Gang1,2, TIAN Ning1,2, YOU Xianhui1,2, HE Zhili1,2,TIAN Hongming3, ZENG Zhuzhou3
(1. Chongqing Key laboratory of Karst Environment, School of Geographical Science, Southwest University, Chongqing 400715, China;
2. Field Scientific Observation & Research Base of Karst Eco-environments at Nanchuan in Chongqing, Ministry of Land and Resources of China, Chongqing 408435;
3. Harmo Trust Agriculture Development Co., Ltd, Chongqing 409800)
Abstract: Understanding dynamic characteristics of groundwater resources by carrying out the continuous and dynamic high resolution online monitoring is necessary for controlling the rocky desertification in anticlinal karst valleys. Take the Laoquan spring monitoring station in the Longtan karst valley, Youyang County of the Chongqing city, as an example and use methods of PONSEL multichannel automatic date logger, field testing and indoor analysis to study dynamic characteristics of water chemistry at seasonal time scale and in heavy rainfall events of 2017. The sources of hydrochemical components of the Laoquan spring were estimated by the principal component analysis (PCA) for both seasonal time scale and heavy rainfall event. The results showed that: (1) seasonally, pH, conductivity, and concentrations of Ca2+, HCO3- and Mg2+ were lower in the rainy season than in the dry season due to the dilution of rain, while concentrations of K+, Na+, total Mn, Al3+ and total Fe were higher in the rainy season than in the dry season due to the higher soil leaching in the rainy season. The PCA analysis showed that the change of water chemistry are affected mainly by four principal components, whose cumulative contribution rate is up to 85.53%, while the most important two factors are the water- rock interaction and the loss of soil elements; (2) in terms of heavy rainfall events, chemical properties of the spring water in the rocky desertification background responded rapidly to rainfall but variations of water chemistry indexes were obviously different under different vegetation conditions; the water chemistry changes in two typical heavy rainfalls were affected mainly by four principal components, the cumulative contributions are 85.63% and 85.40%, respectively, but the most important two factors were the agricultural activity and the loss of soil elements; (3) concentrations of NO3- and SO42- in the Laoquan spring increased after planting of pepper plants, such sulfuric and nitric may participate in karstification processes and exert important impacts on the water quality of Laoquan. Therefore, the monitor and research on dynamic characteristics of the surface spring in the anticlinal karst ridge-trough is of great practical significance for the efficient utilization and management of water resources in the rocky desertification area.
Key words: rocky desertification; trough valley; karst spring; hydrogeochemistry; Youyang in Chongqing City
EARTH AND ENVIRONMENT Vol.46, No.6, Tot No.326, 2018, Page 524-533
