Identification and quantification of contributions to karst groundwater using a triple stable isotope labeling and mass balance model.

Although karst groundwater systems provide critical ecosystem services in many regions worldwide, anthropogenic contamination has seriously degraded groundwater quality. Properly elucidating geochemical processes, quantifying contributions of natural and anthropogenic end members, and then protecting karst aquifer systems remain challenging from scientific and engineering aspects. To identify the hydrochemical processes and quantifying contributions of end members (especially, contamination end members), 49 samples were collected from cave waters (CW), artesian springs (AS), and gravity springs (GS) in a karst watershed in Guiyang, China. With increased anthropogenic contamination, the CW, AS, and GS characterized by a Ca-Mg-SO42--HCO3- composition often had pH and SO42- concentrations exceeding USEPA secondary drinking water standards. That is attributed to the influence of water-rock interaction, rainfall, and anthropogenic sources (mainly, sewage and fertilizers), in agreement with the compositions of δ34SSO4, δ18OSO4, and 87Sr/86Sr as well as the results of principal component analysis and correlation coefficients. Based on an end-member mixing model, contributions of rainfall and anthropogenic sources were 47% and 33% of GS, 52% and 41% of CW, and 58% and 35% of AS, respectively. It suggests that the karst groundwater quality is predominantly controlled by rainfall and anthropogenic sources (especially, land use). Results may be applied to properly evaluate the impacts of natural and anthropogenic sources on karst aquifers, coupled with actions to efficiently control potential contamination end members.

Transcranial Sonographic Alterations of Substantia Nigra and Third Ventricle in Parkinson's Disease with or without Dementia.

BACKGROUND: Numerous studies have demonstrated that patients with Parkinson's disease (PD) have a higher prevalence of substantia nigra (SN) hyperechogenicity compared with controls. Our aim was to explore the neuroimaging characteristics of transcranial sonography (TCS) of patients with PD and those with PD with dementia (PDD). The correlation between the echogenicity of the SN and clinical symptoms in Chinese patients with PDD was also assessed. METHODS: The ratios of SN hyperechogenicity (SN+), maximum sizes of SN+, and widths of third ventricle (TV) were measured using TCS for all the recruited patients. Data were analyzed using one-way analysis of variance, rank-sum test, Chi-square test, and receiver-operating characteristic (ROC) curve analysis. RESULTS: The final statistical analysis included 46 PDD patients, 52 PD patients, and 40 controls. There were no significant differences in ratios of SN+ and maximum sizes of SN+ between PDD and PD groups (P > 0.05). TV widths were significantly larger in PDD group (7.1 ± 1.9 mm) than in PD group (6.0 ± 2.0 mm) and controls (5.9 ± 1.5 mm, P < 0.05); however, the ratios of enlarged TV did not differ among the three groups (P = 0.059). When cutoff value was set at 6.8 mm, the TV width had a relatively high sensitivity and specificity in discriminating between PDD and PD groups (P = 0.030) and between PDD group and controls (P = 0.003), based on ROC curve analysis. In PDD patients, SN+ was more frequently detected in akinetic-rigid subgroup, and patients with SN+ showed significantly higher Hoehn and Yahr stage and Nonmotor Symptoms Questionnaire scores (P < 0.05). CONCLUSIONS: Compared to Chinese patients with PD, patients with PDD had a wider TV, altered SN sonographic features, and more severe clinical symptoms. Our findings suggest that TCS can be used to assess brain atrophy in PD and may be useful in discriminating between PD with and without dementia.

[Study on geochemical susceptivity of groundwater system in representative karstic regions].

We investigated geochemical susceptivity of groundwater in representative karst groundwater system. The results indicated that Ca2+ and Mg2+, correlative the average values of geochemical susceptivity index (GSI) were 0.73 and 0.19; HCO3- and SO4(2-), interrelated the average values of geochemical susceptivity index were 0.92 and 0.37, are the principal cations and anions in karstic groundwater system, respectively. And the major elements are obviously characterized by the geochemical susceptivity. The rank order of geochemical susceptivity for major elements in study region is HCO3- > Ca2+ > SO4(2+) > Mg2+ > Cl- > Na+ > NO3- > K+. The susceptive regions of groundwater system were zoned by the geochemical susceptivity index of HCO3- (GSI(HCO3-)), which classified as GSI(HCO3-) < 0.5 is low-susceptivity zone, 0.5 < GSI(HCO3-) < 1 is moderate-susceptivity zone and GSI(HCO3-) > 1 is high-susceptivity zone, respectively. The groundwater systems in high-susceptivity zone may become as a collected and genetic room for pollutants. Furthermore, both continual or active exchange and mutual recharge between surface water and groundwater in high-susceptivity zones might induce intersectant pollution and serious cycle.