An Automatic-Vertical Profile Monitoring System for Fresh-Saline Water Zones in Coastal Aquifer.

Coastal aquifers are complex systems governed by fresh-saline water interactions and ocean tidal effects. The vertical electrical conductivity (EC) and temperature (T) are general indicators for detecting the fresh-saline water interface (FSI) and sea water intrusion in groundwater wells located in coastal aquifers. In this method brief, we developed a cost-effective Arduino-based automatic-vertical profile monitoring system (A-VPMS) to continuously record vertical EC and T in groundwater wells, with the aim of testing its effectiveness in spatiotemporal monitoring of the FSI in a coastal aquifer located in eastern Korea. By analyzing the high-density EC and T data obtained by the A-VPMS, we evaluated the characteristics of the FSI, such as depth and spatial distribution. Our established EC and T data collection method using the A-VPMS proved to be efficient and reliable, providing an excellent tool for fine-scale temporal and spatial understanding of sea water intrusion. The results of this study demonstrate the potential of the A-VPMS for continuous monitoring of the FSI in coastal aquifers, which is crucial for sustainable management of groundwater resources.

Recent pollution and source identification of metal(loid)s in a sediment core from Gunsan Reservoir, South Korea.

We assessed the contributions of Cu smelting and Asian dust influx to metal(loid) pollution over the last century based on metal(loid) concentrations, Pb isotope ratios, and 210Pb dating of sediments from Gunsan Reservoir, South Korea. During the pre-industrial period (1827-1936), heavy metal pollutants were predominantly geogenic. Local smelting activity was dominant between 1936 and 2008. Between 1936 and 1971, Cu and Pb contamination was not significant, with contributions from smelting activities accounting for < 6.2% of the measured concentrations. In contrast, anthropogenic Cu and Pb inputs increased between 1971 and 2008 due to intense smelting activity. Based on the similar 206Pb/207Pb ratios of the reservoir sediments and smelter bottom ash, anthropogenic contributions reached 95% during 1987-1995. In comparison, the sediments deposited between 2008 and 2018 were characterized by a higher Zn and Cd geoaccumulation index and enrichment factor values and less-radiogenic Pb signals than the regional geogenic Pb signal. These trends are attributed to the long-range transport of pollutants from China, the contribution of which gradually increased from 11.0% in 2008 to 19.2% in 2018. Our results show that reservoir sediments are valuable archives for reconstructing metal(loid) contamination histories and changes in pollution sources over time.

Groundwater Impacts from the M5.8 Earthquake in Korea as Determined by Integrated Monitoring Systems.

This paper describes the impacts of the M5.8(5.1) Gyeongju earthquakes on groundwater levels using data obtained from a unique coastal monitoring well. The monitoring strategy integrates conventional water level monitoring with periodic, continuous measurements of temperature and electrical conductivity (EC) within the water column of the well. Another important component of the monitoring system is a new instrument, the InterfacEGG, which is capable of dynamically tracking the freshwater-saltwater interface. Although the system was set up to monitor seawater intrusion related to over-pumping, as well as rainfall and tidal effects, it recorded impacts associated with a large earthquake and aftershocks approximately 241 km away. Seismic energies associated with the M5.8(5.1) Gyeongju earthquakes induced groundwater flows to the monitoring well through fractures and joints in the crystalline basement rocks. Temperature and EC logging data showed that the EC vertical profile declined from an average of approximately 5300 to 4800 µS/cm following the earthquakes. The temperature profile showed a trend toward lower temperatures as the depth increased, a feature not commonly observed in previous studies. Data from the InterfacEGG suggested that the rise in EC was not due to the saltwater intrusion, but from the tendency for brackish water entering the borehole to induce convective mixing at deeper depths as the seismic waves travel through the well-aquifer system. The increase in groundwater levels was caused by pulse of colder, less brackish water flowing into the well because of the earthquake. This behavior reflects an enhancement in rock permeability by removing precipitates and colloidal particles from clogged fractures, which improve the hydraulic connection with a nearby unit with a higher hydraulic head. This study suggests there is value added with a more aggressive monitoring strategy.

Stump rotation in a nerve autograft by 2 factors: cross-connection and difference in diameter.

The aim of this study was to determine the influence of stump rotation (fascicular cross-connection) on nerve autograft functional recovery. Thirty rat sciatic nerves were transected and repaired by autograft. The rats were divided into 3 groups according to the number of stump rotations of the autograft: (1) plain graft (PG-g, with no change in fascicular orientation, no difference in diameter), (2) graft rotation (GR-g, with no change in fascicular orientation, and diameter difference between fascicles), (3) stump rotation (SR-g, with cross-connection and diameter difference between fascicles). Relative gastrocnemius muscle weight and nerve fiber count were examined as anatomic recovery indices, and autotomy score (ATS) and toe-out angle as functional recovery indices. The results showed that SR-g had a significantly low functional recovery compared with PG-g and GR-g. However, there was no difference found in the anatomic recovery. These findings suggest that the stump rotation in nerve autograft had no effect on neural regeneration and muscle reinnervation; however, it had a negative effect on functional recovery. Because GR-g was similar to PG-g rather than SR-g in functional recovery, the diameter difference between fascicles appears to have had little effect on the functional recovery. The results of this study suggest that a novel approach to ATS interpretation is needed. It is recommended that (1) ATS 2 be considered the onset of autotomy instead of ATS 1; and (2) the frequency of "ATS 2 and above" should be considered for the comparison of the autotomy rather than the mean ATS.