Characteristics of metal contamination in paddy soils from three industrial cities in South Korea.

Paddy soil contamination is directly linked to human dietary exposure to toxic chemicals via crop consumption. In Korea, rice paddy fields are often located around industrial complexes, a major anthropogenic source of metals. In this study, rice paddy soils were collected from 50 sites in three industrial cities to investigate the contamination characteristics and ecological risk of metals in the soils. The cities studied and their major industries are as follows: Ulsan (petrochemical, nonferrous, automobile, and shipbuilding), Pohang (iron and steel), and Gwangyang (iron and steel, nonmetallic, and petrochemical). Thirteen metals (Al, As, Ba, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, V, and Zn) were analyzed using inductively coupled plasma-optical emission spectrometry (ICP-OES). The mean concentration of Cd (1.98 mg/kg) exceeded the soil quality guideline of Canada (1.4 mg/kg), whereas concentrations of other metals were under the standards of both Korea and Canada. Generally, levels of metal concentrations decreased with increasing distance from industrial complexes. Among the three cities, Pohang showed high concentrations of Zn (142.2 mg/kg), and Ulsan and Gwangyang showed high concentrations of Cr (33.9 mg/kg) and Ba (126.4 mg/kg), respectively. These contamination patterns were influenced by the different major industries of each city, which was clearly demonstrated by the principal component analysis results. Pollution indices suggested that As, Cd, Pb, and Zn were enriched in the paddy soils via anthropogenic activities. Comprehensive potential ecological risk indices were at considerable levels for most sites, especially because of major contributions from As and Cd, which can pose potential ecological threats.

Assessment of polychlorinated naphthalenes in Korean foods: Levels, profiles, and dietary intake.

Concerns about dioxin-like compounds have increased; however, the monitoring of polychlorinated naphthalenes (PCNs) in food and the assessment of dietary intake remain limited. In this study, various foods were collected from Korean markets and analyzed for PCNs. Fishery products exhibited the highest mean concentration (48.0 pg/g ww) and toxic equivalent (TEQ) (0.0185 pg-TEQ/g ww). Agricultural products were the largest contributors (35.7%) to the total dietary intake of PCNTEQ, followed by livestock products (33.6%), fishery products (20.2%), and processed foods (10.5%). The mean intake of PCNTEQ for the Korean population was 0.901 pg-TEQ/day for males and 0.601 pg-TEQ/day for females. Generally, males and younger groups had higher daily intakes of PCNTEQ, but they did not exceed the tolerable weekly intakes. Nonetheless, it is important to manage potential health risks associated with PCNs and other dioxin-like compounds by identifying major food items contributing to PCN exposure and considering age and gender differences.

Optimization and application of passive air sampling method for gaseous elemental mercury in Ulsan, South Korea.

We compared uptake rates and concentrations of gaseous elemental mercury (GEM) by passive sampling conditions and investigated the spatial distribution of GEM in Ulsan, the largest industrial city in South Korea. For the optimization of sampling conditions, two outer sampling containers (cylindrical polyethylene terephthalate and two stainless steel bowls), two different sulfur contents of the sorbent (16.3% and 26.3%), and three sampling periods (1, 2, and 3 months) were considered. The uptake rates of GEM were not statistically different by the sampling container, but they were increased with the sulfur contents of activated carbon. A sampling condition using two stainless bowls and lower sulfur contents of activated carbon for 2-3 months was preferred with the highest precision of GEM concentrations. With the same method, passive air samples were collected for 3 months in duplicate from 10 sites in Ulsan. The concentrations of GEM ranged from 3.13 to 11.2 ng/m3 (mean 4.65 ng/m3), and the highest concentration was measured at a non-ferrous industrial complex. A zinc smelter in the non-ferrous industrial complex was identified as a major mercury source in Ulsan. This study is the first passive air sampling study investigating the spatial distributions of GEM in different types of industrial areas as well as residential areas of Ulsan.

Isotopic investigation of sources and processes affecting gaseous and particulate bound mercury in the east coast, South Korea.

Understanding sources and processes affecting atmospheric mercury (Hg) are key to enabling targeted Hg managements under the Minamata Convention on Mercury. We employed stable isotopes (δ202Hg, Δ199Hg, Δ201Hg, Δ200Hg, Δ204Hg) and backward air trajectories to characterize sources and processes affecting total gaseous Hg (TGM) and particulate bound Hg (PBM) in a coastal city, South Korea, subjected to atmospheric Hg sources of a local steel manufacturing industry, coastal evasion from the East Sea, and long-distance transport from East Asian countries. Based on the simulated airmasses and the isotopic comparison with TGM characterized from other urban, remote, and coastal sites, TGM evaded from the coastal surface of the East Sea (warm seasons) and from the land surface in high latitude regions (cold seasons) act as important sources relative to local anthropogenic emissions at our study location. Conversely, a significant relationship between Δ199Hg and concentrations of PBM (r2 = 0.39, p < 0.05) and a seasonally uniform Δ199Hg/Δ201Hg slope (1.15), except for summer (0.26), suggest that PBM is generally sourced from local anthropogenic emissions and subjected to Hg2+ photo-reduction on particles. The striking isotopic similarity between our PBM (δ202Hg; -0.86 to 0.49 ‰, Δ199Hg; -0.15 to 1.10 ‰) and those previously characterized along the coastal and offshore regions of the Northwest Pacific (δ202Hg; -0.78 to 1.1 ‰, Δ199Hg; -0.22 to 0.47 ‰) infer that anthropogenically emitted PBM from East Asia and those processed in the coastal atmosphere serves as a regional isotopic end-member. The implementation of air pollution control devices can reduce local PBM, while regional and/or multilateral efforts are required to manage TGM evasion and transport. We also anticipate that the regional isotopic end-member can be used to quantify the relative influence of local anthropogenic Hg emissions and complex processes affecting PBM in East Asia and other coastal regions.

Contamination characteristics of polychlorinated naphthalenes in the agricultural soil of two industrial cities in South Korea.

This study investigates the contamination characteristics of polychlorinated naphthalenes (PCNs) in the rice paddy soils of two industrial cities (Pohang and Ulsan) in South Korea. The paddy soils were collected from 40 sites in the paddy fields near industrial complexes in both cities. The mean concentration of Σ55 PCNs was 145.9 ± 101.7 pg/g and 95.4 ± 41.4 pg/g for the soils in Pohang and Ulsan, respectively. The toxic equivalents (TEQs) of Σ28 PCNs ranged from 0.007 pg-TEQ/g to 0.069 pg-TEQ/g in Pohang, and 0.015 pg-TEQ/g to 0.046 pg-TEQ/g in Ulsan. The PCN profiles were dominated by lower chlorinated homologues such as tetra- and tri-CNs for both cities, which are associated with the historical use of technical products, or more specifically, Halowaxes (HW 1099, 1031, 1013, and 1001). The results of the principal component analysis (PCA) indicate that the historical residues from the technical products contributed to the PCN contamination, but the influence of combustion sources was also observed with a high fraction of combustion-related congeners. Based on this study, we can expect that rice grown in these paddy fields will accumulate PCNs and other combustion-related pollutants, strongly suggesting the necessity for multimedia (e.g., air, soil, water, and rice) monitoring and human exposure assessments of PCNs.