Research Reveals New Method for Tracking Mercury Variations

Abstract

The source-receptor relationship of atmospheric mercury is a critical environmental concern. However, comprehensive evaluations of mercury pollution based on spatially resolved and time-averaged data have not yet been conducted in Korea. In this study, the spatio-temporal variations of total gaseous mercury (TGM) and mercury isotopes were examined using passive air samplers at 30 sites in Ulsan over one year. TGM concentrations ranged from 2.26 ng/m3 to 68.5 ng/m3 with a mean of 6.89 ng/m3. Mean TGM concentrations by season were the highest in summer (9.28 ng/m3), followed by spring (7.31 ng/m3), winter (6.57 ng/m3), and fall (4.41 ng/m3). The highest concentration occurred in a non-ferrous industrial complex (21.9 ng/m3). Seasonal winds significantly influenced gaseous mercury dispersion to surrounding areas. The mean contributions of anthropogenic emissions, surface evasion, and background effects to TGM levels were 73 %, 2 %, and 25 % during summer and 49 %, 12 %, and 39 % during winter, respectively. The results indicate that anthropogenic emissions are the major source of gaseous mercury in the coastal city of Ulsan, particularly during summer when southeasterly winds are prevalent. This study is the first to present spatial and seasonal distribution maps of source contributions to TGM concentrations using mercury isotope analysis and a ternary mixing model.

A research team, led by Professor Sung-Deuk Choi from the Department of Civil, Urban, Earth, and Environmental Engineering at UNIST has developed a novel assessment technique to accurately identify the sources and spatial-temporal distribution of atmospheric mercury.

This groundbreaking technology relies on high-resolution atmospheric monitoring and mercury isotope analysis. By analyzing the ratios of various mercury isotopes, researchers can effectively trace the origins of atmospheric mercury. The technique enhances accuracy by categorizing mercury sources into three distinct groups for analysis.

Using this assessment method, the research team conducted a comprehensive analysis of the atmospheric conditions in Ulsan over the course of one year, collecting samples from 30 different locations. The findings revealed significant seasonal and spatial variations in mercury concentrations, with an average concentration of 9.3 ng/m³ recorded during summer, the highest of any season, and a low of 4.4 ng/m³ during the fall. Intriguingly, the highest concentration-21.9 ng/m³-was measured in a non-ferrous industrial complex, suggesting that this sector is a major contributor to mercury emissions.

The study also highlighted the critical role of seasonal winds in the dispersion of mercury. During the summer and spring, prevailing southeasterly winds facilitated the transport of mercury emitted from coastal industrial sites into the inland areas of Ulsan. In contrast, during the fall and winter, northwesterly winds carried atmospheric mercury toward the East Sea, resulting in lower mercury concentrations. Notably, 73% of the mercury levels in summer were attributed to anthropogenic emissions, predominantly from the non-ferrous metal industry.

The research team is currently conducting long-term analyses in other industrialized regions, which they believe will also help in accurately assessing the contribution of cross-border mercury transport from neighboring countries.

Mercury poses serious health risks, including damage to the brain and kidneys, respiratory diseases, gastrointestinal disorders, elevated blood pressure, and skin rashes. Prolonged exposure can lead to mercury toxicity and Minamata disease, a severe condition linked to mercury poisoning. Due to its low boiling point and vapor pressure, mercury can exist in gaseous form in the atmosphere.

Professor Choi stated, "While the detected mercury concentrations do not exceed the U.S. Environmental Protection Agency's recommended standard of 300 ng/m³, the persistent nature of mercury as a pollutant underscores the importance of ongoing monitoring and management of industrial sites."

The study, featuring In-Gyu Cho from UNIST as the first author and contributions from Professor Sae Yun Kwon of POSTECH, as well as Dr. Jae-Hyun Lim and Dr. Dong-Woon Hwang from the National Institute of Fisheries Science (NIFS), has been supported by the Ulsan Green Environment Center, Korea Institute of Marine Science & Technology Promotion (KIMST), and the National Research Foundation of Korea (NRF). The results of this research have been published in the April 2025 issue of the Journal of Hazardous Materials.

Journal Reference

In-Gyu Cho, Hoin Lee, Sae Yun Kwon, et al, "Isotopic Fractionation of Gaseous Mercury in A Large Industrial City: Spatio-Temporal Variations and Source Apportionment," J. Hazard. Mater., (2025).