Application of ion-exchange resin sachets and XRF-CS in heavy metal pollution sources monitoring

For the past decades, scientists have endeavored to develop efficient and suitable approaches to monitor heavy-metal pollution through technological development. Conventional monitoring methods for heavy metals are still complicated, relatively expensive, and time-consuming. This research aims to develop an innovative heavy-metal monitor, the novel approach of ion-exchange resin sachets combined with X-ray fluorescence core scanner (XRF-CS), to achieve an efficient way to effectively monitor vast areas for contamination. The resin sachets, which have a large capacity to quickly take up heavy metals, were deployed in the river weekly to capture heavy metals and then analyzed using the non-destructive, fast, and cost-efficient Itrax XRF core scanner. Two four-week sampling sessions, performed during the dry and wet periods, respectively, were conducted in northeastern Taiwan, where the environment was contaminated by a copper smelter and coal mine activities in the late twentieth century. The results suggest that ion-exchange resins are useful as long-term monitors of heavy metals in a low pollution-level settings (metal concentration <1 mg/L), and that XRF core scanner data truly reflect metal pollution concentrations as measured by inductively coupled plasma-optical emission spectrometry (ICP-OES). This approach allows us to pinpoint pollution sources along the studied river. Especially, Zn, Ni, Mn, Fe, Cu, Ca, and Sr could be detected near pollution sources, where cps values were 1.8 to 3430.6 times higher than in unpolluted areas. Zn shows the largest difference between polluted and non-polluted areas, with the cps values of the samples in polluted areas 3528 times higher than their non-polluted counterparts. Ni, Mn, Fe, Cu, Ca, and Sr’s cps values were 1.8, 29.2, 46.1, 2.4, 6.2, and 5.9 times higher, respectively, than the corresponding counts measured in non-polluted areas. In addition, our results demonstrate that the intensity of precipitation influences the amount of metal adsorption in the resins; resins showed less adsorption in the dry period, and cps values slightly dropped to 81 to 84 percent of the wet period. In summary, ion-exchange resins are a sensitive tool that can be applied in pollution monitoring at various pollution levels due to their high performance in adsorbing heavy metals. Consequently, ion-exchange resin sachets in combination with XRF core scanner analysis is a cost-effective way to monitor large areas of potentially polluted aquatic systems quickly.