Kwang-Seol Seok

Emission characteristics of particulate matter and heavy metals from small incinerators and boilers

The characteristics of particulate matter (PM) emission such as the estimation of emission factors, size distributions and of heavy metal emission from small-size incinerators and boilers have been investigated. In PM-10 emission, a fine mode was found in the formation of sub-micron PM by growth of nucleated aerosol of metal vapor, having a bimodal particle size distribution in overall size range. The emission ratios of PM-10 to TPM (total PM) from boilers and incinerators ranged from 29% to 62% and 10% to 84%, respectively, which resulted in more and larger sized PM emission due to poorer combustion from solid waste incinerators than boilers. The targeted metals were copper, cadmium, manganese, chromium, magnesium, lead, zinc and copper, and their contents in bottom ash, fly ash and dust (PM) were compared. More volatile metals such as cadmium, lead and zinc showed higher enrichment in PM emitted through stack than bottom ashes. Cadmium, copper, lead and zinc on the fine PM under 2.5 μm accounted for approximately 90% of the total mass of each metal in PM-10. The effects of chlorine concentration and temperature on such metals emission were also observed due to their volatility changes.

A national discharge load of perfluoroalkyl acids derived from industrial wastewater treatment plants in Korea

Levels of 11 perfluoroalkyl acids (PFAAs), including perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS), were measured in wastewater (influent and effluent) and sludge samples collected from 25 industrial wastewater treatment plants (I-WWTPs) in five industrial sectors (chemicals, electronics, metals, paper, and textiles) in South Korea. The highest ∑11PFAAs concentrations were detected in the influent and effluent from the paper (median: 411ng/L) and textile (median: 106ng/L) industries, and PFOA and PFOS were the predominant PFAAs (49-66%) in wastewater. Exceptionally high levels of PFAAs were detected in the sludge associated with the electronics (median: 91.0ng/g) and chemical (median: 81.5ng/g) industries with PFOS being the predominant PFAA. The discharge loads of 11 PFAAs from I-WWTP were calculated that total discharge loads for the five industries were 0.146ton/yr. The textile industry had the highest discharge load with 0.055ton/yr (PFOA: 0.039ton/yr, PFOS: 0.010ton/yr). Municipal wastewater contributed more to the overall discharge of PFAAs (0.489ton/yr) due to the very small industrial wastewater discharge compared to municipal wastewater discharge, but the contribution of PFAAs from I-WWTPs cannot be ignored.

Significance of metabolite extraction method for evaluating sulfamethazine toxicity in adult zebrafish using metabolomics.

Recently, environmental metabolomics has been introduced as a next generation environmental toxicity method which helps in evaluating toxicity of bioactive compounds to non-target organisms. In general, efficient metabolite extraction from target cells is one of the keys to success to better understand the effects of toxic substances to organisms. In this regard, the aim of this study is (1) to compare two sample extraction methods in terms of abundance and quality of metabolites and (2) investigate how this could lead to difference in data interpretation using pathway analysis. For this purpose, the antibiotic sulfamethazine and zebrafish (Danio rerio) were selected as model toxic substance and target organism, respectively. The zebrafish was exposed to four different sulfamethazine concentrations (0, 10, 30, and 50mg/L) for 72h. Metabolites were extracted using two different methods (Bligh and Dyer and solid-phase extraction). A total of 13,538 and 12,469 features were detected using quadrupole time-of-flight liquid chromatography mass spectrometry (QTOF LC-MS). Of these metabolites, 4278 (Bligh and Dyer) and 332 (solid phase extraction) were found to be significant after false discovery rate adjustment at a significance threshold of 0.01. Metlin and KEGG pathway analysis showed comprehensive information from fish samples extracted using Bligh and Dyer compared to solid phase extraction. This study shows that proper selection of sample extraction method is critically important for interpreting and analyzing the toxicity data of organisms when metabolomics is applied.

Sub-lethal pharmaceutical hazard tracking in adult zebrafish using untargeted LC-MS environmental metabolomics

Antibiotics in the aquatic environment are dispersed through anthropogenic activities at low concentrations. Despite their sub lethal concentration, these biologically active compounds may still have adverse effects to non-target species. This study examined the response of adult zebrafish to 0.1mg/L concentration of clarithromycin, florfenicol, sulfamethazine, and their mixture using environmental metabolomics. Embryo and larvae of the fish were also used to assess fish embryo acute toxicity and behavior tests respectively. The fish embryo toxicity test did not show any inhibition of growth and development of the embryos after 96h of exposure to the antibiotics. Changes in swimming activity were seen in 5-dpf larvae which is believed to be correlated with the length of exposure to the compounds. Meanwhile, environmental metabolomics revealed diverse metabolites and pathways that were affected after 72h of exposure of the adult fish to sub-lethal concentration of the compounds. We found that even at low concentration of the antibiotics, behavioral and metabolic effects were still observed despite the lack of visible morphological changes. Further studies involving other aquatic organisms and bioactive compounds are encouraged to strengthen the findings presented in this novel research.

Tracking lead contamination sources of sediments in Lake Andong using lead isotopes

The objective of this study was to identify Pb pollution sources of sediments in Lake Andong. We analysed Pb isotopes in sediments from Lake Andong, soils and mining tails from the watershed as well as sludges and wastewater from zinc smelting facilities which exists in upper stream of Lake Andong. The Pb isotope ratios ( 207 Pb/ 206 Pb and 208 Pb/ 206 Pb) for sediments are 0.827±0.004 and 2.041±0.015, which showed similar values with those of mining tails, 0.815±0.002 and 2.016±0.006, respectively. The isotopic ratio values of soils existed in the range of 0.756~0.881 and 1.872~2.187. In imported zinc ores, the isotopic ratio values existed in the range of 0.816~0.956 (mean 0.832) and 2.029~2.219 (mean 2.059). These values were similar to those in zinc and lead concentrate originated from Canada and South America. Additionally, isotopic ratio values for sludge and wastewater were 17.515±0.155, 15.537±0.018, and 37.357±0.173, respectively. The Pb isotopic ratio of sediments showed binary combination patterns with soil and mining tails, which were similar to those for Korean Pb ore.

Distribution of heavy metals and mercury in sediment from the lake An-dong

In this study, mercury, methylmercury and heavy metals in sediment from the lake Andong were analyzed, along with the estimation of mercury flux between sediments and water in the lake Andong. Average mercury concentrations in sediments sampled in 2009~2011 were 155.0±71.9 ng/g, 211±62 ng/g and 198±6.88 ng/g, respectively. The average methylmercury concentration were 1.85±1.09 ng/g (2009) and 3.49±1.79 ng/g (2011), and %methylmercury, the fraction of methylmercury in total mercury were 1.17±0.39% and 1.77±0.94%, respectively. Heavy metal (Zn, Cd, Pb, Cu) concentrations of the sediments exceeded ERL (Effect Range Low) level of US NOAA (National Oceanic and Atmospheric Administration)s sediment quality criteria. Estimated mercury sedimentation flux was found to be 83.7 ng/㎠·yr and mercury diffusion flux was estimated as 1.24 ng/㎠·yr.

Characterizing isotopic compositions of TC-C, NO3 − -N, and NH 4 + -N in PM 2.5 in South Korea: Impact of China's winter heating

The origin of PM2.5 has long been the subject of debate and stable isotopic tools have been applied to decipher. In this study, weekly PM2.5 samples were simultaneously collected at an urban (Seoul) and rural (Baengnyeong Island) site in Korea from January 2014 through February 2016. The seasonal variation of isotopic species showed significant seasonal differences with sinusoidal variation. The isotopic results implied that isotope species from Baengnyeong were mostly originated from coal combustion during Chinas winter heating seasons, whereas in summer, the isotopic patterns observed that were more likely to be from marine. In Seoul, coal combustion related isotopic patterns increased during Chinas winter heating period while vehicle related isotopic patterns were dominated whole seasons by default. Therefore, aerosol formation was originated from long-range transported coal combustion-related NOx by vehicle-related NH3 in Seoul. δN-NH4+ in Seoul showed highly enriched 15N compositions in all seasons, indicating that NH3 from vehicle emission is the important source of NH4+ in PM2.5 in Seoul. In addition, Baengnyeong should be consistently considered as a key region for observing the changes of isotopic features depend on the contribution of individual emissions to the atmospheric as a result of the reduction of coal consumption in China.

Enrichment of PCDDs/PCDFs in peripheral utilities of the municipal solid waste incineration facility

This study was performed to suggest the improvements through measuring the amounts of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs), re-synthesized in peripheral utilities (PUs) of a commercial-scale municipal solid waste incineration facility (MSWIF) where a few research results existed. The PUs examined in this study consisted of air pre-heaters (APHs) and gas/gas re-heater (GGRH) and kerosene-fired duct burner for selective catalytic reduction (SCR) process. PCDDs/PCDFs in flue gas were simultaneously measured at the inlet and outlet of PUs. Flue gas was cooled down from 380 °C to 249 °C by exchanging the heat with fresh air in APHs, and then heated up to 383 °C by GGRH and duct burner from 164 °C at the outlet of bag filter. The results showed that PCDDs/PCDFs were 3-4 times higher within this temperature range of PUs. In comparison of PCDDs/PCDFs concentrations at the inlet with those at the outlet of PUs, particulate-phase PCDDs/PCDFs were about 9.5-10 times enriched while gaseous-phase ones were decreased by about 33-41%. The PCDDs/PCDFs re-synthesized in the PUs, where PCDDs were relatively higher than PCDFs, showed somewhat different patterns compared to those formed at incinerators and emitted at stack. Through the investigations for PUs, we conclude that the PUs used in MSWIFs was a potential source for de novo synthesis of PCDDs/PCDFs.