Cheng H.,Xi'an Jiaotong University |
Cheng H.,University of Minnesota |
Sinha A.,California State University, Dominguez Hills |
Verheyden S.,Royal Belgian Institute Of Natural Sciences |
And 9 more authors.
Geophysical Research Letters | Year: 2015
The Levant constitutes an important region for assessing linkages between climate and societal changes throughout the course of human history. However, large uncertainties remain in our understanding of the region's hydroclimate variability under varying boundary conditions. Here we present a new high-resolution, precisely dated speleothem oxygen-carbon isotope and Sr/Ca records, spanning the last 20 ka from Jeita Cave, northern Levant. Our record reveals a higher (lower) precipitation-evaporation (P-E) balance during the Last Glacial Maximum and Bølling interstadial (Heinrich stadial 1). The early-middle Holocene is characterized by a trend toward higher P-E state, culminating between ~7 and 6 ka. The middle-late Holocene is characterized by two millennial-length drier periods during 5.3-4.2 and 2.8-1.4 ka. On submillennial time scale, the northern Levant climate variability is dominated by 500 year periodicity. Comparisons with the regional proxy records suggest persistent out-of-phase climate variability between the northern and southern Levant on a wide range of timescales. Key Points High-resolution speleothem record is established in northern Levant in the last 20 ka The Climate variability on various timescales in northern Levant is characterized Climate variations are out of phase between northern and southern Levant © 2015. American Geophysical Union. All Rights Reserved.
Kang Z.Q.,Hubei University |
Kang Z.Q.,Key Laboratory of Karst Dynamics |
Kang Z.Q.,International Research Center on Karst |
Yu F.F.,Hubei University |
And 9 more authors.
Water-Rock Interaction - Proceedings of the 13th International Conference on Water-Rock Interaction, WRI-13 | Year: 2010
The hydrogeological condition of an interfluve area, located in the town of Mengxu, Guangxi, China, is discriminated by using the trace element strontium. The Ca/Sr ratio can be used as an indicator of the karst groundwater runoff conditions. In this case, 3 strong flow zones could be distinguished by the Ca/Sr ratio value of 400. For verification purposes, 9 boreholes and 2 geophysical exploration sections were carried out. The boreholes and geophysical data support the hydrogeochemical results. © 2010 Taylor & Francis Group, London.
Yin J.-J.,Key Laboratory of Karst Dynamics |
Yin J.-J.,Southwest University |
Yin J.-J.,Chinese Academy of Geological Sciences |
Yuan D.-X.,Key Laboratory of Karst Dynamics |
And 17 more authors.
Climate of the Past | Year: 2014
This paper focuses on the climate variability in central China since AD 1300, involving: (1) a well-dated, 1.5-year resolution stalagmite δ18O record from Lianhua Cave, central China (2) links of the δ18O record with regional dry-wet conditions, monsoon intensity, and temperature over eastern China (3) correlations among drought events in the Lianhua record, solar irradiation, and ENSO (El Niño-Southern Oscillation) variation. We present a highly precise, 230Th / U-dated, 1.5-year resolution δ18O record of an aragonite stalagmite (LHD1) collected from Lianhua Cave in the Wuling Mountain area of central China. The comparison of the δ18O record with the local instrumental record and historical documents indicates that (1) the stalagmite δ18O record reveals variations in the summer monsoon intensity and dry-wet conditions in the Wuling Mountain area. (2) A stronger East Asian summer monsoon (EASM) enhances the tropical monsoon trough controlled by ITCZ (Intertropical Convergence Zone), which produces higher spring quarter rainfall and isotopically light monsoonal moisture in the central China. (3) The summer quarter/spring quarter rainfall ratio in central China can be a potential indicator of the EASM strength: a lower ratio corresponds to stronger EASM and higher spring rainfall. The ratio changed from <1 to >1 after 1950, reflecting that the summer quarter rainfall of the study area became dominant under stronger influence of the Northwestern Pacific High. Eastern China temperatures varied with the solar activity, showing higher temperatures under stronger solar irradiation, which produced stronger summer monsoons. During Maunder, Dalton and 1900 sunspot minima, more severe drought events occurred, indicating a weakening of the summer monsoon when solar activity decreased on decadal timescales. On an interannual timescale, dry conditions in the study area prevailed under El Niño conditions, which is also supported by the spectrum analysis. Hence, our record illustrates the linkage of Asian summer monsoon precipitation to solar irradiation and ENSO: wetter conditions in the study area under stronger summer monsoon during warm periods, and vice versa. During cold periods, the Walker Circulation will shift toward the central Pacific under El Niño conditions, resulting in a further weakening of Asian summer monsoons. © 2014 Author(s).
Guo Y.-S.,Southwest University |
Guo Y.-S.,Key Laboratory of Karst Dynamics |
Yu S.,Key Laboratory of Karst Dynamics |
Li Y.-S.,Guilin Environment Monitoring Center |
And 3 more authors.
Huanjing Kexue/Environmental Science | Year: 2016
A total of 396 rainwater samples of Guilin from 2008 to 2011 were collected and analyzed for pH, 44 of which were analyzed for major ions. The analysis of pH values showed the obvious seasonal variation of acid rain in Guilin. The pollution level of summer was lower than those in other seasons, while the pollution levels in winter and spring were the highest. The investigation of fractional acidity(AF) and neutralization factors (NF) indicated that low acid rain pollution level in 2008 was caused by alkali neutralization, especially NH4 + and Ca2+. Studies of the origins of major ions showed that CI- and Na+ were mainly from sea, Ca2+ was mainly from the crustal dust while K+, SO4 2- and NO3 - were mainly originated from anthropogenic source. Finally, the effect of regional transportation on acid rain of Guilin was analyzed and 3 originatons of acid-causing substance were oriented by an air trajectory clustering methodology based on hysplit-4 and a clustering algorithm including (1) Jiangxi, Anhui, Hunan and Hubei, with high population densities, these regions contributed 19% air mass in spring, 26% in summer, 19% in autumn and 36% in winter due to the northeast wind; (2) Pearl River Delta, with airflow from west Pacific passing before arriving Guilin, contributing 19% in spring, 33% in autumn and 36% in winter; (3) Nanning, Liuzhou. All strong acid rain vapor air mass converged in southwest Guilin in spring, and arrived in Guilin passing Naning and Liuzhou. In summer, under the direct control of southwest monsoon, the vapor from Indian Ocean directly arrived in Guilin, accounting for 75%. The southwest airflow passing these cities accounted for 14% in autumn and 63% in winter. © 2016, Science Press. All right reserved.
Jiang Z.-C.,Chinese Academy of Geological Sciences |
Jiang Z.-C.,Key Laboratory of Karst Ecosystem and Treatment of Rocky Desertification |
Luo W.-Q.,Chinese Academy of Geological Sciences |
Luo W.-Q.,Key Laboratory of Karst Ecosystem and Treatment of Rocky Desertification |
And 10 more authors.
Acta Geoscientica Sinica | Year: 2014
A karst ecological research team from the Institute of Karst Geology, Chinese Academy of Geological Sciences in Guilin has been going in for the creative study of the leakage of water and soil in the karst mountain areas of Southwest China since the beginning of the 21th century. A series of progresses in the study of leakage of water and soil were achieved in 2013. The concept, processes and mathematic model of the leakage of water and soil were expounded. By using the site monitoring and advanced isotopic techniques, the team firstly and systemically revealed the quantitative differences and causes of the leakage of water and soil in different geomorphologic positions and different ecological environments of the karst peak cluster depression, built the grade classification standards and the regression model of the soil erosion in the karst areas, created some new water and soil preservation models which combined the biological methods with the engineering and technological rules, and formed the pitaya ecological production industry with good ecological and economic benefits in the karst rocky desertification environment. All these research results can provide technological support and demonstration examples for the treatment of the rocky desertification and the conservation of water and soil in the karst areas of Southwest China.
Zhao L.,Chinese Academy of Geological Sciences |
Zhao L.,Key Laboratory of Karst Dynamics |
Xia R.,Chinese Academy of Geological Sciences |
Yi L.,Chinese Academy of Geological Sciences |
And 6 more authors.
Jilin Daxue Xuebao (Diqiu Kexue Ban)/Journal of Jilin University (Earth Science Edition) | Year: 2015
Analysis of flux recession process is an important method to calculate hydrogeological parameters of karst aquifers. Based on the theoretical method of flux recession analysis, the author took the flux records from Sep. 25th to Oct. 13th, 2013 as samples out of the total 8784 sets of flux data through monitoring the export of underground river per hour throughout the whole year to fit flux recession process by MATLAB; and then the attenuation coefficients of three phases were obtained as 0.6425, 0.0258 and 0.0015 respectively; at last, the ratios of hydraulic conductivity to specific yield were calculated, and the hydrogeological parameters were confirmed by given cranny ratio which was roughly equal to the specific yield. The result shows that the hydraulic conductivity for karst conduit, fissured and bedrock medium in Zhaidi basin were 258.87 m2/d, 3865.98 m2/d, and 40.64 m2/d respectively. With the requisite hydrogeological survey, defined conduit distribution, and runoff distance, the method of flux recession analysis could be used to calculate the conductive capability and specific yield of different media for a karst aquifer. © 2015, Jilin University Press. All right reserved.
Su C.,Chinese Academy of Geological Sciences |
Su C.,Key Laboratory of Karst Dynamics |
Zou S.,Chinese Academy of Geological Sciences |
Zou S.,Key Laboratory of Karst Dynamics |
And 4 more authors.
Carbonates and Evaporites | Year: 2016
In this paper, we study the soil CO2 concentration, soil respiration rate, dissolution rate and soil water content of different ecosystems in Luota, western Hunan Province, China, using the CO2 gas monitoring tube method, alkali absorption method, standard specimen method and drying method. The results show the following: the soil CO2 concentrations of the different depths have the same change trends in the forest and bush ecosystems. In spring, autumn and winter, the trends increase as the soil layer deepens, while in summer they first reduce and then increase as the soil layer deepens. However, the seasonal change dynamics differ slightly, and the soil CO2 concentrations of the forest ecosystem at the different depths and in the different seasons are greater than those of the bush ecosystem. From the perspective of comparing the full-year soil CO2 concentration, the full-year soil CO2 concentrations of the forest ecosystem at the depths of 10, 20 and 40 cm are, respectively, 1.66, 1.59 and 1.90 times those of the bush ecosystem. From the perspective of the soil respiration rates of the different seasons, the seasonal change trends of the forest and bush ecosystems are the same, both being summer > autumn > spring. The soil respiration rates of the forest ecosystem in the different seasons are higher than those of the bush ecosystem, and in spring, summer and autumn the respective soil respiration rates of the forest ecosystem are 2.09, 3.46 and 3.06 times those of the bush ecosystem. At the different depths, the dissolution rates have the same change trends in the forest and bush ecosystems, and the dissolution rates at the depth of 15 cm are both greater than those on the ground. At the same depth, the dissolution rate of the forest ecosystem is greater than that of the bush ecosystem, and the dissolution rates on the ground and at the depth of 15 cm are, respectively, 1.11 and 2.57 times those of the bush ecosystem. The soil water content of the forest ecosystem is 1.07 times of that of the bush ecosystem, and the soil water content stability of the forest ecosystem is higher, indicating that the forest ecosystem has a better karst effect. © 2016 Springer-Verlag Berlin Heidelberg
Jiang G.,Chinese Academy of Geological Sciences |
Jiang G.,Key Laboratory of Karst Dynamics |
Guo F.,Chinese Academy of Geological Sciences |
Guo F.,Key Laboratory of Karst Dynamics |
And 2 more authors.
Jilin Daxue Xuebao (Diqiu Kexue Ban)/Journal of Jilin University (Earth Science Edition) | Year: 2015
Six karst water systems in Southwest China are selected for comparison study, in order to find out the relationship between spring chemographs and their hydrogeological characters. The six karst springs are S31 in Yaji experimental site, Maocun subterranean river, Guancun subterranean river, Chenqi spring, Qingmuguan subterranean river, and Shuifang spring in Jinfo Mt. Some important results are summarized. The repeated chemograph changes in springs were found through continuous auto-monitoring of pH, temperature, specific electrical conductivity (SPC) and other indexes. There are some common differences in chemographs impacted by intrinsic and extrinsic properties of the system. Firstly, recharge from rainfall leads to changes in discharge and water-rock interaction. Secondly, the CO2 recharge with infiltration promotes the karst process. Finally, contaminate leaching from surface also has impact on water chemistry. When the SPC, pH, water temperature, and saturation index of calcite (SIc) decrease after rainfall recharge event, it indicates the occurrence of dilution process. When the SPC together with other indexes show peaks after rainfall recharge, it indicates CO2 effect caused by seepage recharge from epikarst water dissolved with CO2 in soil. When the chemographs are found lagging behind the change of hydrograph, piston flow effect occurs. Eluviation effect occurs when the ions related to human activities increase after rainfall recharge. This can be explained by the contaminant distinctly input from the surface washing, and probably have influence on variation trend of SPC. Chemographs of karst water system tend to have several effects frequently, and the mutual types are different, suggesting that different strong or weak impact on karst water by diffusion or concentration recharge from rainfall recharge, and the difference in runoff pattern and regulation and storage mechanism. In general, karst water system which is dominated by diffusion recharge, usually presents more CO2 effect in chemographs, and less dilution effect. In karst water system with strong karstification, rainfall recharge is controlled by solution fissure and conduits. Their chemographs presents more in dilution effect, while less in CO2 effect. Karst systems dominated by concentration recharge are easily to have piston flow effect. However, the variation of water chemistry is weakened in systems when they have big thickness of vadose zone and high storage capacity of aquifer. ©, 2015, Jilin University Press. All right reserved.