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Lan J.-C.,Southwest University | Lan J.-C.,Field Scientific Observation and Research Base of Karst Eco environments at Nanchuan in Chongqing | Sun Y.-C.,Southwest University | Shi Y.,Southwest University | And 4 more authors.
Huanjing Kexue/Environmental Science | Year: 2014

Surface soil (0-20 cm) from various agricultural sites in Laolongdong underground river basin was collected to determine the concentrations, compositional profiles, and sources of 16 priority polycyclic aromatic hydrocarbons (PAHs). PAHs were measured by GC/MC. The total concentrations of PAH16 ranged from 277-3 301 ng·g-1, with a mean of 752.6 ng·g-1±635.5 ng·g-1, and 57%, 29% and 14% of soil samples were slightly, moderately and heavily polluted by PAHs, respectively. The PAH compositional profiles were dominated by 2, 3 ring compounds, which accounted for 28.72%-72.68%(a mean of 48.20%) of the total PAHs, while 4 ring and 5, 6 ring PAHs accounted for an average of 7.77% and 34.03%, respectively. Soil organic matter(SOM) was found to be significantly correlated with the 16 PAHs and total PAHs. However, pH value was slightly correlated with the 16 PAHs and total PAHs. Isomer pair ratios and Principal component analysis (PCA) suggested vehicles, coal, petroleum and biomass combustion as the main sources of PAHs, and another major source was petroleum. Source

Sun Y.,Southwest University | Sun Y.,Chinese Academy of Geological Sciences | Sun Y.,Field Scientific Observation and Research Base of Karst Eco environments at Nanchuan in Chongqing | Liang Z.,Southwest University | And 5 more authors.
Chemosphere | Year: 2016

The thin surface soil layer and karst features in karst terrains lead to poor filtration, poor pre-purification and rapid infiltration, so that karst groundwater systems are particularly vulnerable to contamination. Due to its extensive use in past, gamma-hexachlorocyclohexane (γ-HCH) is ubiquitous in various environmental compartments of China, even though it has been prohibited since 1984. However, very little is known about its movement and behavior in special karst system. In this study, a dynamic fugacity model was established for γ-HCH in epikarst system via dividing the karst soil into multiple layers coupled with the physical-chemical properties of γ-HCH. The simulated results in soil profile were in good agreement with the measured values of γ-HCH. The modeled results predict that only 18 g γ-HCH will be left in the studied area in 2020, which is only 0.4% of the largest reserves in 1983, and about 99.99% of γ-HCH will remains in soil. The concentrations of γ-HCH in air, plant and 0-20 cm layer soil in the studied area descended quickly after HCHs was prohibited in 1984, while its concentration in soil layer deeper than 20 cm (deeper soil) increased continuously till 1997. The dominant transfer process of γ-HCH between the adjacent compartments in the studied area was from 0-20 cm layer to the deeper soil. Sensitivity analysis results showed that emission rate, infiltration coefficient, total organic carbon of soil, degradation rate in soil, compartment area and volume were the top six influential parameters for predicting γ-HCH concentration. © 2015 Elsevier Ltd. Source

Liu W.,Southwest University | Liu W.,Field Scientific Observation and Research Base of Karst Eco environments at Nanchuan in Chongqing | Liu W.,Chinese Academy of Geological Sciences | Zhang Q.,Chinese Academy of Geological Sciences | And 2 more authors.
Shengtai Xuebao/ Acta Ecologica Sinica | Year: 2014

Many studies showed that the carbon sink resulted from karst process is fast and stable, which compose the very important part of "Missing carbon sink". Different land-use patterns can affect the karst process by influence the soil properties. Commonly, with the land-use change from forest land to cultivated field the soil organic matter will reduce, the stability of soil structure get worse, the soil moisture retaining quality get down and the quantity of soil microbiology will diminish, all the above would affect the karst process. This study took 6 different land-use patterns(Tilled land (code: Ha), Paddy field (St), Reforested land (Tu), Abandoned Land(Hu), Mixed Woodland with Chinese fir-bamboo(Sz) and Bamboo land(Zh)) with the same geological backgrounds but different human influence intensity in Qingmuguan karst valley as a case study to determine the influence factors on karst processes. Standard limestone tablets were buried in the field to test the dissolution process rate. HOBO automatic weather station was located in the roof of local people's house to get the precipitation and temperature data. CO2 content in different soil layers were tested by Gas-Tec CO2 tester. Soil samples in different layers were taken back to laboratory to detect the pH value, the organic matter, soil moisture content, and soil bulk density. The dissolution data from tablets showed that, firstly, the mean dissolution mass per unit area of different land-use patterns in different layers in Summer were 3.87 times than in Winter. The max mean dissolution mass changed from -80cm layer in Summer to -20--50cm layers in Winter. Secondly, the mean dissolution mass in these two land-use patterns Ha and St with strong human influence intensity (Abbr. HII) was higher than that inTu and Hu in which the HII get weaker, while that in Sz and Zh which had the weakest HII with the lowest mean dissolution mass. Also, the range between them was higher in summer with strong HII than that in winter. Afteranalyzing the temperature(T), precipitation (P) and the soil physicochemical properties data, we can find that, there was a positive correlation between the change of dissolution mass with seasons and T, P which were the most important factors affecting the former. The soil CO2 content can only play an important role on dissolution in summer which has more precipitation, and these two factors can react each other enough to form more carbonic acid so more carbonate tablets can be dissoluted. There was a negative correlation between soil organic matter and soil pH, and these two factors affected the dissolution jointly. They can influence dissolution greatest only in surface layer with high organic matter and low pH, while less in deeper layers. The influence of soil texture determined by soil bulk density and soil porosity on dissolution was bidirectional. The clay with good moisture retaining quality but bad permeability was benefit for the dissolution in winter for there was less precipitation that time, but bad in summer for there was no so much water pass through the soil, Hu was a good example of this. However, there was an oppose process in sandy soil with good permeability but bad moisture retaining quality, corresponded more dissolution in summer and less in winter, there was a good example of tilled land also. Additionally, the use of farmyard manure and chemical fertilizer which include NO- 3 and SO2 4 - can promote the dissolution process too. Above all, the results of this study can provide consultation for evaluate karst carbon sink more scientifically and accurately. Source

Lan J.-C.,Southwest University | Lan J.-C.,Field Scientific Observation and Research Base of Karst Eco environments at Nanchuan in Chongqing | Sun Y.-C.,Southwest University | Sun Y.-C.,Chinese Academy of Geological Sciences | And 7 more authors.
Huanjing Kexue/Environmental Science | Year: 2014

Water samples in Laolongdong underground river catchment were collected to determine the concentration, compositional profiles, and evaluate ecological risk of 16 priority polycyclic aromatic hydrocarbons (PAHs). PAHs were measured by GC/MS. The total concentrations of 16 PAH ranged from 81.5-8 019 ng·L-1 in underground river, 288.7-15 200 ng·L-1 in karst springs, and 128.4-2 442 ng·L-1 in surface water. Affected by waste water from Huangjueya town, concentrations of PAHs in underground river were higher than those in surface water and waste water from sinkhole. The PAHs profiles were dominated by 3 ring PAHs. There were differences of monthly variations of PAHs contents in the water,due to waste water,season and different characteristics of PAH. Surface water and waste water from sinkhole played an important role on contamination in the river. The levels of ecological risk were generally moderately polluted and heavily polluted according to all detected PAH compounds in the water. Source

Yang P.-H.,Southwest University | Yang P.-H.,The Karst Dynamics Laboratory | Yang P.-H.,Field Scientific Observation and Research Base of Karst Eco environments at Nanchuan in Chongqing | Lu B.-Q.,Nanjiang Hydrogeological and Engineering Geology Brigade | And 4 more authors.
Huanjing Kexue/Environmental Science | Year: 2014

The two-year hydrologic process, hydrochemistry, and a portion of δD, δ18O of both the surface water at the inlet and the groundwater at the outlet, were investigated to identify the spatial and temporal variations of hydrogeochemistry in the Qingmuguan karst groundwater system. Research results show that there are wet and dry periods in the groundwater system owing to the striking influence of seasonal rainfall. The evolution of the chemical compositions in the groundwater is significantly influenced by the water and rock interaction, anthropogenic activities and rainwater dilution. The variations of the chemical compositions in the groundwater exhibit obvious spatiality and temporality. The δD and δ18O of the surface water beneath the local Meteoric Water Line of Chonqing indicate that the surface water is strongly evaporated. Furthermore, the δD and δ18O of the surface water are more positive in the dry period than in the wet period, showing a distinct seasonal effect. The δD and δ18O of the groundwater are quite stable and much negative compared with those of the surface water, which suggests that the rainwater recharge the groundwater via two pathways, one directly through sinkholes and the other via the vadose zone. Source

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