Rapid assessment of heavy metal pollution using ion-exchange resin sachets and micro-XRF core-scanning

Abstract

Conventional pollution monitoring strategies for heavy metals are often costly and unpractical. Innovative sampling and analytical approaches are therefore needed to efficiently monitor large areas. This study presents a novel, simple, fast, and inexpensive method to monitor heavy metal pollution that uses cation-exchange resin sachets and the micro-XRF core-scanning technique (XRF-CS). The resin passive samplers act as concentrators of cationic species and can be readily deployed spatially and temporally to record pollution signals. The large number of analytical tasks are then overcome by the fast and non-destructive XRF-CS to precisely assess elemental concentrations. Quantifying element loading involves direct comparison with a set of identically prepared and scanned resin reference standards containing Ca, Ti, Cr, Mn, Ni, Cu, Zn, Pb. The results show that within the test range (from 0–1000 s mg kg −1 ), the calibration lines have excellent regressions (R 2 ≥ 0.97), even at the shortest exposure time (1 s). A pilot field survey of a suspected polluted area in central Taiwan, where 30 resin sachets had been deployed, identified a pollution hot spot in a rapid and economical manner. Therefore, this approach has the potential to become a valuable tool in environmental monitoring and forensics.

A multiple model approach for evaluating the performance of time-lapse capsules in trapping heavy metals from water bodies

“…The concentration of the adsorbed heavy metals on the time-lapse capsules could also be rapidly determined by the nondestructive X-ray uorescence core-scanning (XRF-CS) technique. 3,11 According to the results reported by Huang et al, 3 the concentrations of heavy metals determined by the XRF-CS (the increase on the resin) and the conventional analytical method (the reduction in water) exhibited excellent correlations (R 2 > 0.97) even at a short scanning time (<1 s). By doing so, one could identify the potential hot spots of illegal discharge in situ and then keep deploying more time-lapse capsules upstream until the discharge point of the industry is located.…”

“…The detailed procedure for the preparation of time-lapse capsules can be found in our previous studies. 3,11…”

“…For detecting illegal discharges of wastewater, Huang et al 3 developed ion-exchange resin sachets (referred to as "time-lapse capsules" in this work) to trap metallic ions from the watershed, such as irrigation and drainage channels, throughout a certain period of time (usually >seven days). The time-lapse capsules were manufactured by packing a certain amount of ionexchange resins into a non-woven fabric sachet.…”

Application of Time-Lapse Ion Exchange Resin Sachets (TIERS) for Detecting Illegal Effluent Discharge in Mixed Industrial and Agricultural Areas, Taiwan

“…The Itrax XRF-CS, which is a unique multi-function scanner for core examination, is commonly used for geological research, and it can detect the element profiles of sediment core. Raychaudhuri et al [50] used the Itrax XRF-CS to analyze the exposure time of resins in laboratory and field survey. Their results showed that resin samples can be measured in approximately 20 s and identified pollution hot spots in a rapid way.…”

Establishment of an Automatic Real-Time Monitoring System for Irrigation Water Quality Management

“…In order to overcome this critical issue, several innovative inspection technologies, such as time-lapse capsules [7,8], have been developed and deployed in the field tests for identifying the patterns of the heavy metals from the illegal discharge. Apart from the innovative inspection, the integration of continuous automatic sampling techniques and cloud technologies was imperative to provide the real-time monitoring for identifying the sources of pollution and improving the irrigation water quality management.…”