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Summary: Groundwater is nearly the sole source for freshwater supply on Jeju volcanic island because there are no perennial streams and rivers. Rain harvesting and subsequent artificial recharging have been conducted to meet growing freshwater demand in the island. We performed sequential samplings of harvested rainwater prior to the artificial injection in summer of 2008 at an artificial recharge site of western Jeju. Field measurements and chemical analyses of 313 rainwater samples revealed that there was a variation in chemical composition but the Na+K+SO4 +Cl type was dominant. Predominance of Na and Cl was likely to be from sea salts while substantial amount of SO4, NO3 , and NH4 is attributed to anthropogenic air pollution. The enrichment factors of SO4, HCO3, K, Mg, and Ca suggested that their non-marine contribution ranges from 75.4% to 99.98%. However, the sea salt contributed substantially to Cl concentration up to 73.5%. Most of the rainwater parameters generally decreased with time and they were generally stabilized after 20min, which is an effect of the first flush and thus some diversion (rerouting) is required for suitable artificial injection of the harvest rainwater in this study area. [ABSTRACT FROM AUTHOR]

Microplastic (MPs) contamination in groundwater has received massive attention since plastic waste has been released directly into the environment. This study investigates MPs contamination in groundwater on the Jeju volcanic Island, Korea. To the best of our knowledge, this is the first study to identify MPs in groundwater from volcanic islands. A total of 21 sites were sampled for groundwater wells and springs in July and September (2021). Sampling was performed without cross-contamination through quality assurance and quality control. The results showed that MPs abundance ranged from 0.006 to 0.192 particles/L in groundwater samples. Additionally, MPs were detected in deep groundwater wells where the groundwater level was 143 m below ground surface. Eight MPs polymer types, including polypropylene, polyethylene, polyethylene terephthalate, polyvinyl chloride, polystyrene, polyamide, acrylonitrile butadiene styrene, and polyurethane, were detected using Micro-Fourier Transform Infrared Spectroscopy (μ-FT-IR). Most of the detected MPs size ranged from 20 to 100 μm, accounting for 95% of the total. Fragments and fiber shaped MPs were detected, with the majority of them being fragmented in groundwater samples. The concentrations of MPs and major ions in groundwater showed a positive correlation. A negative correlation was observed between MPs concentration and topographic elevation (r = −0.59, p = 0.01). The source of MPs contamination is most likely attributed to agricultural activities, such as plastic mulching and greenhouses, which account for most of the land use in the study area. In this study, MPs entered the aquifer through the soil at the surface and seeped through cracks in fractured rock on basalt with sealed groundwater wells. This study takes 500 L of samples to prevent sample bias, reveal plastic contamination in groundwater, and indicating the characteristics and sources of contaminated plastics. [Display omitted] • Most MPs detected in groundwater were smaller than 50 μm. • Eight polymers were identified, with PP and PE being dominant types in groundwater. • Predominant shapes of MPs in groundwater were fragments. • MPs abundance and groundwater levels have a negative correlation. [ABSTRACT FROM AUTHOR]