Ionic exchange in groundwater hydrochemical evolution. Study case: the drainage basin of El Pescado creek (Buenos Aires province,Argentina)

The phreatic aquifer beneath the Pampean plain, in eastern central Argentina, constitutes a relevant source of water supply in the area. The objective of this work was to assess the significance of the cation exchange processes in the hydrochemical evolution of this aquifer, based on a study case located in the middle and upper basin of the El Pescado creek. Results indicate that Ca²⁺/Na⁺ exchange is the main process determining the evolution of groundwater from the recharge areas (Ca–HCO₃) towards the local discharge areas (Na–HCO₃), as well as representing a source of Na⁺ contribution to the water in the aquifer. This hydrochemical characteristic is central to the identification of local discharge areas within a plain environment which extends regionally. The ion exchange capacity of these discharge areas has environmental importance, due to its influence on groundwater quality and potential groundwater uses. These results may be applied to any aquifer sharing similar hydrogeological characteristics.     

Determination of the removal efficiency of a vortex-type facility as a best management practice using the dynamic event mean concentration: a case study of a bridge in Yong-In city in Korea

Thus far, the removal efficiency of non-point-pollution source removal facilities has been evaluated for individual rainfall events. However, as the removal efficiency for part of a single rainfall event has not been evaluated, adapting the removal facilities for these concentrations is imprecise. Of 18 rainfall events, the removal efficiency of a vortex-type facility as a BMP (Best Management Practice), a non-point-pollution source removal method, was assessed in this study in four assessment techniques and analyzed. In addition, the efficiency was assessed for the concentration using dynamic EMC (Event Mean Concentration). At a higher concentration, the efficiency becomes higher in terms of the TSS, COD, and TP results. In the case of TP, the concentration range of 0~2 mg/L showed the highest efficiency. In the case of Zn, low efficiency was shown in a concentration range of 0.2∼0.6 mg/L.     

Effect of rainfall characteristics on removal efficiency evaluation in vegetative filter strips

The efficiency of a facility to remove non-point source pollution is likely to fluctuate according to conditions such as facility type and rainfall events; therefore, it is required to use a proper method to estimate removal efficiency. This study was conducted to estimate the efficiency of a facility with vegetative filter strips to remove pollutants by using methods previously used for the estimation of removal efficiency and compensate for weaknesses of the known methods. Other ways were presented to estimate an efficiency by which rainfall events were classified according to meteorological condition and amount of rainfall. Rainfall of frequency and summation of load as rainfall of frequency, where the frequencies per rainfall class were considered in efficiency ratio and summation of loads, respectively, seemed to have higher removal efficiencies than those estimated with the previous methods. Although it rained at the basin site, often in small quantity (below 10 mm), the rainfall events of below 10 mm were less frequent, during the monitored rainfall events, which accordingly resulted in low removal efficiencies. However, if the frequencies per rainfall class were considered, overall removal efficiencies of VFS might be increased because the removal efficiencies of the rainfall class under 10?mm was higher than other rainfall classes. Therefore, it is desirable to take into account such factors as effects of rainfall when it comes to measuring the removal efficiency of a non-point source pollutant of a factor, because those facilities are likely to be influenced by meteorological conditions including rainfall characteristics.     

Selenium and heavy metals content in some Mediterranean soils

The study of metal contents in industrial, agricultural or/and polluted soils compared with natural or unpolluted soils is currently necessary to obtain reference values and to assess soil contamination. Nonetheless, very few works published appear in international journals on elements like Se, Li and Sr in Spanish soils. This study determines the total levels of Se, Li, Sr, As, Cd, Co, Cr, Cu, Ni, Pb, V, Zn, Fe, Mn and Ba in 14 natural (unpolluted) soils (Gypsisols, Leptosols, Arenosols and Acrisols), 14 agricultural soils (Anthrosols, Fluvisols and Luvisols), and 4 industrial–urban affected-surface soil horizons (Anthrosols and Fluvisols) of Eastern Spain. The geochemical baseline concentrations (GBC) and reference values (RV) have been established, and the relationships among elements and also between soil properties and elemental concentrations have been analysed. The RV obtained in this study were (mg kg⁻¹): Se 2.68, Li 115, Sr 298, Cd 0.97, Co 35, Cr 217, Cu 46, Ni 50, Pb 137, V 120, Zn 246, Fe 124,472, Mn 2691, and Ba 743. The RV for Se and Li were used as a preliminary approach to assess soil contamination in Spanish soils. The results confirm human impact on Sr, As, Cd, Cr, Cu, Ni, Pb and Zn soil concentrations, but evidence no deviation from natural Se, Li, Co, V, Fe, Mn and Ba concentrations. The results obtained from the statistical analysis reveal significant correlations between some elements and clay and soil organic matter (SOM) contents, indicating that metal concentrations are controlled by soil composition. One particularly interesting finding is the high correlation coefficients obtained between SOM and Se, Cd, Cr, V, Fe, and Mn, and between clay and Cd, Zn, V, Fe and Mn. Once again, these facts confirm the role of SOM and clay minerals in soil functions and that soil is an ecosystem element responsible for maintaining environmental quality.     

Leveraging similarity analysis to understand variability in movement behavior

The increasingly large volume of trajectories of moving entities obtained through GPS and cellphone tracking, telemetry, and other location-aware technologies motivates researchers to understand the implicit patterns hidden in movement trajectories and understand how movement is influenced by the environmental context. Trajectory similarity serves as an important tool in computational movement analysis and as the foundation of revealing those patterns. However, there are various trajectory similarity measures, each of which has its own strengths and weaknesses. In this article, we present a hierarchical clustering framework that integrates five commonly used similarity measures, including Fréchet distance, dynamic time warping, Hausdorff distance, longest common subsequence, and normalized weighted edit distance, a special kind of edit distance for movement analysis. The framework aims at clustering similar patterns and identifying variability in movement. The optimal number of clusters are first obtained. Then, the clusters are characterized by environmental variables to explore the associations between variability in movement and the environmental conditions. We evaluate the proposed framework using 15 years of tracking data of turkey vultures, tracked at 1- to 3-h sampling intervals, during their fall and spring migration seasons. The results suggest that, at 5% significance level, turkey vultures select their movement paths intentionally and those selections appear to be related to certain environmental context variables, including thermal uplift, vegetation state (observed indirectly through Normalized Difference Vegetation Index), temperature, precipitation, tailwind, and crosswind. And interestingly, there exist preferential differences among individuals. Although the preference of the same turkey vulture is not strictly consistent over different years, each individual tends to preserve a more similar preference over different years, compared with the preferences of other turkey vultures.