Morphological and chemical composition characteristics of summertime atmospheric particles collected at Tokchok Island,Korea

Determination of the chemical compositions of atmospheric single particles in the Yellow Sea region is critical for evaluating the environmental impact caused by air pollutants emitted from mainland China and the Korean peninsula. After ambient aerosol particles were collected by the Dekati PM10 cascade impactor on July 17–23, 2007 at Tokchok Island (approximately 50 km west of the Korean coast nearby Seoul), Korea, overall 2000 particles (on stage 2 and 3 with cut-off diameters of 2.5–10 μm and 1.0–2.5 μm, respectively) in 10 samples were determined by using low-Z particle electron probe X-ray microanalysis. X-ray spectral and secondary electron image (SEI) data showed that soil-derived and sea-salt particles which had reacted or were mixed with SO₂ and NO_x (or their acidic products) outnumbered the primary and “genuine” ones (59.2% vs. 19.2% in the stage 2 fraction and 41.3% vs. 9.9% in the stage 3 fraction). Moreover, particles containing nitrate in the secondary soil-derived species greatly outnumbered those containing sulfate. Organic particles, mainly consisting of marine biogenic species, were more abundant in the stage 2 fraction than in the stage 3 fraction (11.6% vs. 5.1%). Their relative abundance was greater than the sum of carbon-rich, K-containing, Fe-containing, and fly ash particles, which exhibited low frequencies in all the samples. In addition, many droplets rich in C, N, O, and S were observed. They tended to be small, exhibiting a dark round shape on SEI, and generally included 8–20 at.% C, 0–12 at.% N, 60–80 at.% O, and 4–10 at.% S (sometimes with <3 at.% Mg and Na). They were attributed to be a mixture of carbonaceous matter, H₂SO₄, and NH₄HSO₄/(NH₄)₂SO₄, mostly from the reaction of atmospheric SO₂ with NH₃ under high relative humidity. The analysis of the relationship between the aerosol particle compositions and 72-h backward air-mass trajectories suggests that ambient aerosols at Tokchok Island are strongly affected not only by seawater from the Yellow Sea but also by anthropogenic pollutants emitted from China and the Seoul–Incheon metropolis, resulting in the dominance of complex secondary aerosol particles.     

Aerosol chemistry and the effect of aerosol water content on visibility impairment and radiative forcing in Guangzhou during the 2006 Pearl River Delta campaign

Optical and chemical aerosol measurements were obtained from 2 to 31 July 2006 at an urban site in the metropolitan area of Guangzhou (China) as part of the Program of Regional Integrated Experiment of Air Quality over Pearl River Delta (PRIDE-PRD2006) to investigate aerosol chemistry and the effect of aerosol water content on visibility impairment and radiative forcing. During the PRIDE-PRD2006 campaign, the average contributions of ammonium sulfate, organic mass by carbon (OMC), elemental carbon (EC), and sea salt (SS) to total PM_2.5 mass were measured to be 36.5%, 5.7%, 27.1%, 7.8%, and 3.7%, respectively. Compared with the clean marine period, (NH₄)₂SO₄, NH₄NO₃, and OMC were all greatly enhanced (by up to 430%) during local haze periods via the accumulation of a secondary aerosol component. The OMC dominance increased when high levels of biomass burning influenced the measurement site while (NH₄)₂SO₄ and OMC did when both biomass burning and industrial emissions influenced it. The effect of aerosol water content on the total light-extinction coefficient was estimated to be 34.2%, of which 25.8% was due to aerosol water in (NH₄)₂SO₄, 5.1% that in NH₄NO₃, and 3.3% that in SS. The average mass-scattering efficiency (MSE) of PM₁₀ particles was determined to be 2.2 ± 0.6 and 4.6 ± 1.7 m² g⁻¹ under dry (RH < 40%) and ambient conditions, respectively. The average single-scattering albedo (SSA) was 0.80 ± 0.08 and 0.90 ± 0.04 under dry and ambient conditions, respectively. Not only are the extinction and scattering coefficients greatly enhanced by aerosol water content, but MSE and SSA are also highly sensitive. It can be concluded that sulfate and carbonaceous aerosol, as well as aerosol water content, play important roles in the processes that determine visibility impairment and radiative forcing in the ambient atmosphere of the Guangzhou urban area.     

Indoor air quality investigation according to age of the school buildings in Korea

Since the majority of schools are housed in buildings dating from the 1960s and 1970s, a comprehensive construction and renovation program of school buildings has been carried out to improve the educational conditions in Korea. However, classrooms and computer rooms, with pressed wood desks, chairs and furnishings, as well as construction materials, might have negative effects on the indoor air quality. Furthermore, most schools have naturally ventilated classrooms. The purpose of this study was to characterize the concentrations of different indoor air pollutants within Korean schools and to compare their indoor levels within schools according to the age of school buildings. Indoor and outdoor air samples of carbon monoxide (CO), carbon dioxide (CO(2)), particulate matter (PM(10)), total microbial count (TBC), total volatile organic compounds (TVOCs) and formaldehyde (HCHO) were obtained during summer, autumn and winter from three sites; a classroom, a laboratory and a computer classroom at 55 different schools. The selection of the schools was based on the number of years since the schools had been constructed. The problems causing indoor air pollution at the schools were chemicals emitted by building materials or furnishings, and insufficient ventilation rates. The I/O ratio for HCHO was 6.32 during the autumn, and the indoor HCHO concentrations (mean = 0.16 ppm) in schools constructed within 1 year were significantly higher than the Korean Indoor Air Standard, indicating that schools have indoor sources of HCHO. Therefore, increasing the ventilation rate by means of a mechanical system and the use of low-emission furnishings can play key roles in improving the indoor air quality within schools.     

Industrial experience of process identification and set-point decision algorithm in a full-scale treatment plant

This paper presents industrial experience of process identification, monitoring, and control in a full-scale wastewater treatment plant. The objectives of this study were (1) to apply and compare different process-identification methods of proportional-integral-derivative (PID) autotuning for stable dissolved oxygen (DO) control, (2) to implement a process monitoring method that estimates the respiration rate simultaneously during the process-identification step, and (3) to propose a simple set-point decision algorithm for determining the appropriate set point of the DO controller for optimal operation of the aeration basin. The proposed method was evaluated in the industrial wastewater treatment facility of an iron- and steel-making plant. Among the process-identification methods, the control signal of the controller's set-point change was best for identifying low-frequency information and enhancing the robustness to low-frequency disturbances. Combined automatic control and set-point decision method reduced the total electricity consumption by 5% and the electricity cost by 15% compared to the fixed gain PID controller, when considering only the surface aerators. Moreover, as a result of improved control performance, the fluctuation of effluent quality decreased and overall effluent water quality was better.     

Simulating Direct and Indirect Damages to Commercial Fisheries from Marine Sand Mining: A Case Study in Korea

Rapid growth in marine sand mining for construction and other uses poses environmental challenges to coastal nations virtually worldwide. Yet the development of management policies, such as a system of fees imposed on operators for damage caused by mining, has been frustrated by a lack of studies to support such measures. Adapting a Beverton-Holt bioeconomic model, this paper attempts to contribute to the estimation of external costs to commercial fisheries due to marine mining. Using the major mining area of Ongjin in Korea as a case study, we estimate economic losses in use value of commercial fisheries through the time to recovery of the injured resource stocks. Present value of lost catch over a 1-year period from mining to resource recovery is estimated at $38,851 for a single “prototype” mining site. Estimated cumulative damages due to recurring mining for 5 and 10 years are $1.5 million and $2.2 million, respectively, at 20 mining sites. Sensitivity analyses are used to examine the effects of alternative assumptions to assess the many sources of uncertainty. Using a form of meta-analysis, dose-response information is used to assess the excess mortality the mining sediment plume has on eggs and larvae and, ultimately, on the value of lost catch ($841). Also addressed is the importance of specifying the appropriate “premining” conditions against which to assess environmental losses at the mining site. Damages estimated with premining fish populations are $23,066 higher than is the case using postmining conditions. Overall, the illustrative results suggest the variety of complex conditions which influence damage to fisheries from mining and which can benefit from further study to improve management guidelines. An erratum to this article can be found at     

Effects of sudden changes in salinity on endogenous rhythms of the spotted sea bass Lateolabrax sp.

The endogenous rhythm of oxygen consumption in juvenile spotted sea bass (Lateolabrax sp.) was measured to test the effects of sudden changes in salinity on the metabolic activity. Mean oxygen consumption rates of this euryhaline fish decreased by 13.5 to 16.0% and 25.3 to 36.4% when they were transferred from 31.5 to 15‰ seawater and to fresh water (0‰), respectively. The maximum rate of oxygen consumption was observed between 18:00 and 19:00 hrs local time, 1 to 2 h before sunset, even though they were kept in constant darkness. The peaks of oxygen consumption occurred in 23.2- and 23.3-h intervals, which correspond with a circadian rhythm, as revealed by maximum entropy spectral analysis. A markedly weakened rhythm in oxygen consumption occurred from 8 to 10 d after onset of the experiments. This study indicates that spotted sea bass can withstand sudden drops in salinity from 31.5‰ to fresh water, and yet maintain a regular though somewhat dampened endogenous rhythm of oxygen consumption. Received: 16 June 1997 / Accepted: 3 February 1998     

Effects of humic acid on phytodegradation of petroleum hydrocarbons in soil simultaneously contaminated with heavy metals

Effects of humic acid on phytoremediation of petroleum hydrocarbons in soil simultaneously contaminated with heavy metals were evaluated.     

Characterization of controlled-release KMnO4 (CRP) barrier system for groundwater remediation: a pilot-scale flow-tank study

Release and spreading of permanganate (MnO(4)(-)) in the well-based controlled-release potassium permanganate (KMnO(4)) barrier system (CRP system) was investigated by conducting column release tests, model simulations, soil oxidant demand (SOD) analyses, and pilot-scale flow-tank experiments. A large flow tank (L x W x D=8m x 4m x 3m) was constructed. Pilot-scale CRP pellets (OD x L=0.05 m x1.5m; n=110) were manufactured by mixing approximately 198 kg of KMnO(4) powders with paraffin wax and silica sands in cylindrical moulds. The CRP system (L x W x D=3m x 4m x 1.5m) comprising 110 delivery wells in three discrete barriers was constructed in the flow tank. Natural sands (organic carbon content=0.18%; SOD=3.7-11 g MnO(4)(-)kg(-1)) were used as porous media. Column release tests and model simulations indicated that the CRP system could continuously release MnO(4)(-) over several years, with slowly decreasing release rates of 2.5 kg d(-1) (day one), 109 g d(-1) (day 100), 58 g d(-1) (year one), 22 g d(-1) (year five), and 12 g d(-1) (year 10). Mean MnO(4)(-) concentrations within the CRP system ranged from 0.5 to 6 mg l(-1) during the 42 days of testing period. The continuously releasing MnO(4)(-) was gradually removed by SOD limiting the length of MnO(4)(-) zone in the porous media. These data suggested that the CRP system could create persistent and confined oxidation zone in the subsurface. Through development of advanced tools for describing agent transport and facilitating lateral agent spreading, the CRP system could provide new approach for long-term in situ treatment of contaminant plumes in groundwater.     

Impacts of microbial redox conditions on the phase distribution of pyrene in soil-water systems

Variations in the soil/sediment organic matter (SOM)-hydrophobic organic contaminant (HOC) bindings upon microbially mediated redox conditions were examined. While the extractability of pyrene associated with soil declined after its biodegradation began during aerobic incubation, its variations were almost constant (±3.0-4.4%) during anoxic/anaerobic incubations. The dissolved organic matter released from the soil incubated under highly reduced conditions became more humified and aromatic, had a higher average molecular weight, and was more polydispersed compared to that obtained from oxic incubation, similar to the SOM alterations in the early stage of diagenesis (humification). The concentrations of pyrene in the aqueous phase increased significantly during the soil incubations under highly reduced conditions due to its favorable interaction with the altered DOM. Our results suggest that the microbially mediated redox conditions have significant impacts on SOM and should be considered for the transport, fate, bioavailability, and exposure risk of HOCs in the geo-environments.