The complex nonlinear characteristics of atmospheric chemistry necessitate the development of new methods for calculating source–receptor (S–R) relationships for secondary air pollutants. In this study, the monthly characteristics and S–R relationships of anthropogenic total nitrate (i.e., the sum of N from nitric acid, inorganic nitrate, and peroxyacetyl nitrate) in Northeast Asia were simulated and analyzed. The Community Multiscale Air Quality (CMAQ), Fifth-Generation NCAR/Penn State Mesoscale (MM5), and Sparse Matrix Operator Kernel Emissions (SMOKE) models were employed for air quality modeling, meteorological fields, and emissions processing, respectively. The study area encompassed Republic of Korea, Japan, and most of China. Five source/receptor regions were defined to derive the S–R relationships: three in China, one in Republic of Korea, and one in Japan. To produce data for the calculation of the S–R relationship, several experiments were conducted with a 20% reduction in NO_x emission sources. As a result of the S–R relationships, China was rarely impacted by the other two countries. The total depositions in other countries were significantly dominated by China (i.e., 43.5% and 40.7% in Republic of Korea and Japan, respectively, and up to 82.3% in December for Republic of Korea).

The purpose of this study was to evaluate the important priorities of the major environmental and operating factors that affect the removal of nitrogen and phosphorus in the biological nutrients removal (BNR) process with phase separation by multiple regression analysis using the Excel program. Multiple correlation coefficients and coefficients of determination were calculated using the multiple regression analysis function on the Excel program and statistical significance was reviewed through variance analysis. The degree of influence of each independent variable was also determined using the coefficient for each parameter and the p-value of the regression equation. The effect of mixed-liquor temperature on nitrogen removal in the process was found to be the most significant, followed by cycle time, hydraulic retention time (HRT), solids retention time (SRT), and influent carbon-to-nitrogen ratio. The temperature was also the most influential factor affecting phosphorus removal in the process, followed by the cycle time, SRT, HRT, and influent carbon-to-phosphorus ratio. Evaluation of the complex impact of major environmental and operating factors on nutrient removal in the phase-separated BNR process could be performed successfully. It is expected that operators of treatment facilities will be able to easily derive the important priorities of major factors using multiple regression analysis in Excel based on field data without specialized statistical training, and will thereby contribute to the optimal operation of wastewater treatment

PM_2.5 concentrations in major port cities in the Republic of Korea, such as Incheon and Busan, are as serious as those in land-based metropolises, such as Seoul, and fine dust generated in port cities is mainly emitted from ships. To identify the specific substances influencing local air quality, the occurrence and effects of high concentrations of PM_2.5 at the ports of Incheon and Busan were analyzed. To analyze the effects of improving air quality based on the Republic of Korea’s port and ship-related reduction measures, we calculated an emissions forecast for 2025 following the implementation/non-implementation of these measures and analyzed all impacts using the WRF-SMOKE-CMAQ modeling system. The ratio of ionic components constituting PM_2.5 at the ports of Incheon and Busan was generally high in nitrate composition; however, the ratio of sulfate was high on high PM_2.5 concentration days. When implementing measures to reduce emissions related to ports and ships, forecasted PM_2.5 and SO₂ emissions showed substantial decreases in port areas as well as nearby land and sea areas. The associated decrease in the PM_2.5 concentration was highly influential in reducing the concentration of sulfate.