The Characteristics of Tropospheric Ozone Seasonality Observed from Ozone Soundings at Pohang, Korea

This paper presents the first analysis of vertical ozone sounding measurements over Pohang, Korea. The main focus is to analyze the seasonal variation of vertical ozone profiles and determine the mechanisms controlling ozone seasonality. The maxima ozone at the surface and in the free troposphere are observed in May and June, respectively. In comparison with the ozone seasonality at Oki (near sea level) and Happo (altitude of 1840 m) in Japan, which are located at the same latitude as of Pohang, we have found that the time of the ozone maximum at the Japanese sites is always a month earlier than at Pohang. Analysis of the wind flow at the surface shows that the wind shifts from westerly to southerly in May over Japan, but in June over Pohang. However, this wind shift above boundary layer occurs a month later. This wind shift results in significantly smaller amounts of ozone because the southerly wind brings clean wet tropical air. It has been suggested that the spring ozone maximum in the lower troposphere is due to polluted air transported from China. However, an enhanced ozone amount over the free troposphere in June appears to have a different origin. A tongue-like structure in the time-height cross-section of ozone concentrations, which starts from the stratosphere and extends to the middle troposphere, suggests that the ozone enhancement occurs due to a gradual migration of ozone from the stratosphere. The high frequency of dry air with elevated ozone concentrations in the upper troposphere in June suggests that the air is transported from the stratosphere. HYSPLIT trajectory analysis supports the hypothesis that enhanced ozone in the free troposphere is not likely due to transport from sources of anthropogenic activity.     

Assessment of Wastewater Reuse Effects on Nutrient Loads from Paddy Field Using Field-Scale Water Quality Model

CREAMS-PADDY, a modified version of the field-scale CREAMS model, simulates the hydrologic, sediment, and nutrient cycles in paddy fields. The CREAMS-PADDY model was applied to estimate the effects of using wastewater for irrigation on nutrient loads from paddy fields in Republic of Korea. The model was calibrated and validated using data from two rice paddy fields. The coefficient of determination between observed and simulated total nitrogen and total phosphorus were 0.92 and 0.57, respectively, for the calibration period and 0.84 and 0.73 for the validation period. Simulations showed that when using wastewater for irrigation, the total nitrogen loads increased by 210% and total phosphorus by 1,270% when compared with conventional water irrigation. The total nitrogen and total phosphorus concentration in the ponded water increased by 254 and 534%, respectively, when compared with conventional water irrigation. The effect of reducing N and P fertilizer application rates by 10, 30, and 50% on nutrient loads exiting a paddy field were also simulated using the validated CREAMS-PADDY model. These simulations indicated that total phosphorus loads from the paddy were reduced only slightly by reducing the fertilizer, while total nitrogen loads were reduced by as much as 8.8, 16.6, and 24.4% when N ferlitizer rates were reduced by 10, 30, and 50%, respectively. An erratum to this article can be found at     

Release of arsenic (As) and lead (Pb) from quicklime-sulfate stabilized/solidified soils under diffusion-controlled conditions

A quicklime-sulfate-based stabilization/ solidification (S/S) process for arsenic (As) and lead (Pb) immobilization was evaluated under “semi-dynamic” leaching conditions. In order to simulate aggressive leaching conditions the semi-dynamic leaching tests was modified by using 0.014 N of acetic solution instead of distilled water. Kaolinite-sand and montmorillonite-sand soil samples were artificially contaminated with As and Pb, compacted and cured for 28 days. The semi-dynamic leaching tests were then conducted for 90 days. The effectiveness of the S/S treatment was evaluated by assessing the cumulative release of As and Pb as well as by determining the diffusion coefficients (D _eff) and leachability indices (LX). The release of As and Pb was greatly reduced by quicklime-sulfate treatment as compared to untreated samples. Moreover, the quicklime-sulfate treatment was more effective than the quicklime-only treatment in reducing both As and Pb release. The controlling leaching mechanisms were determined using a diffusion theory model. Upon S/S treatment, As and Pb release was diffusion controlled. The LX of all the treated samples were greater than nine, suggesting that S/S treated samples were suitable for “controlled utilization”.     

OUTLIER DETECTION IN TOTAL PHOSPHORUS CONCENTRATION DATA FROM SOUTH FLORIDA RAINFALL1

ABSTRACT: Atmospheric deposition can be a significant source of phosphorus to South Florida's aquatic system. Deposition samples are often contaminated to varying degrees by bird droppings or other foreign materials. This study attempted to use statistical and other methods to detect and remove the outliers in the rain-borne total phosphorus concentration data. Some outliers in the data were identified using field notes derived from visual inspection of the samples. Outlier detection statistics based on a simple linear regression were then used for additional data screening. As a result of these analyses, about 35 percent of the observed values were identified as outlying data which needed to be removed prior to further data analyses. Based on detected outliers in the data from 15 monitoring sites, a lumped cutoff value of 130 4mUg/L was determined. This lumped cutoff value may be useful for further quality control and analyses of the data from the region.     

Outlier detection in phosphorus dry deposition rates measured in South Florida

Dry atmospheric deposition contributes a significant amount of phosphorus to the Everglades of South Florida. Measurement of this deposition is problematic, because samples often are contaminated to varying degrees by bird droppings and other foreign materials. This study attempted to detect and remove the outliers in phosphorus (P) flux rates measured from dry deposition samples. Visual inspection of the samples, recorded in field notes, found that 30.1% of the samples contained animal droppings and frogs. Some of the samples with droppings and frogs (2.3%) had P values greater than 884 μg P m⁻² d⁻¹ (a value twice the standard deviation of the raw data mean), and were removed from further analysis. Outlier detection statistics based on a linear regression were then used for additional data screening. Eight stations in the network of 19 were removed because high contamination precluded the use of the regression model. Of the remaining samples, 15.7% were identified through the regression procedure as contaminated and were removed. The 11 station mean for P dry deposition was 85.8±79.0 μg P m⁻² d⁻¹, prior to the regression analysis, and 74.8±75.1 μg P m⁻² d⁻¹ after removal.     

Food waste impact on municipal solid waste angle of internal friction

The impact of food waste content on the municipal solid waste (MSW) friction angle was studied. Using reconstituted fresh MSW specimens with different food waste content (0%, 40%, 58%, and 80%), 48 small-scale (100-mm-diameter) direct shear tests and 12 large-scale (430 mm × 430 mm) direct shear tests were performed. A stress-controlled large-scale direct shear test device allowing approximately 170-mm sample horizontal displacement was designed and used. At both testing scales, the mobilized internal friction angle of MSW decreased considerably as food waste content increased. As food waste content increased from 0% to 40% and from 40% to 80%, the mobilized internal friction angles (estimated using the mobilized peak (ultimate) shear strengths of the small-scale direct shear tests) decreased from 39° to 31° and from 31° to 7°, respectively, while those of large-scale tests decreased from 36° to 26° and from 26° to 15°, respectively. Most friction angle measurements produced in this study fell within the range of those previously reported for MSW.     

Predicting Debris Yield From Burned Watersheds: Comparison of Statistical and Artificial Neural Network Models1

Abstract: Alluvial fans in southern California are continuously being developed for residential, industrial, commercial, and agricultural purposes. Development and alteration of alluvial fans often require consideration of mud and debris flows from burned mountain watersheds. Accurate prediction of sediment (hyper‐concentrated sediment or debris) yield is essential for the design, operation, and maintenance of debris basins to safeguard properly the general population. This paper presents results based on a statistical model and Artificial Neural Network (ANN) models. The models predict sediment yield caused by storms following wildfire events in burned mountainous watersheds. Both sediment yield prediction models have been developed for use in relatively small watersheds (50‐800 ha) in the greater Los Angeles area. The statistical model was developed using multiple regression analysis on sediment yield data collected from 1938 to 1983. Following the multiple regression analysis, a method for multi‐sequence sediment yield prediction under burned watershed conditions was developed. The statistical model was then calibrated based on 17 years of sediment yield, fire, and precipitation data collected between 1984 and 2000. The present study also evaluated ANN models created to predict the sediment yields. The training of the ANN models utilized single storm event data generated for the 17‐year period between 1984 and 2000 as the training input data. Training patterns and neural network architectures were varied to further study the ANN performance. Results from these models were compared with the available field data obtained from several debris basins within Los Angeles County. Both predictive models were then applied for hind‐casting the sediment prediction of several post 2000 events. Both the statistical and ANN models yield remarkably consistent results when compared with the measured field data. The results show that these models are very useful tools for predicting sediment yield sequences. The results can be used for scheduling cleanout operation of debris basins. It can be of great help in the planning of emergency response for burned areas to minimize the damage to properties and lives.     

Highly siliceous MCM-48 from rice husk ash for CO2 adsorption

Mesoporous MCM-48 silica was synthesized using a cationic-neutral surfactant mixture as the structure-directing template and rice husk ash (RHA) as the silica source. The MCM-48 samples were characterized by X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), N₂ physisorption and SEM. X-ray diffraction pattern of the resulting MCM-48 revealed typical pattern of cubic Ia3d mesophase. BET results showed the MCM-48 to have a surface area of 1024 m²/g and FT-IR revealed a silanol functional group at about 3460 cm⁻¹. Breakthrough experiments in the presence of MCM-48 were also carried out to test the material's CO₂ adsorption capacity. The breakthrough time for CO₂ was found to decrease as the temperature increased from 298 K to 348 K. The steep slopes observed shows the CO₂ adsorption occurred very quickly, with only a minimal mass transfer effect and very fast kinetics. In addition, amine grafted MCM-48, APTS-MCM-48 (RHA), was prepared with the 3-aminopropyltriethoxysilane (APTS) to investigate the effect of amine functional group in CO₂ separation. An order of magnitude higher CO₂ adsorption capacity was obtained in the presence of APTS-MCM-48 (RHA) compared to that with MCM-48 (RHA). These results suggest that MCM-48 synthesized from rice husk ash could be usefully applied for CO₂ removal.