A multi-variate methodology for analyzing pre-existing lake water quality data

Environmental agencies are given the task of monitoring water quality in rivers, lakes, and other bodies of water, for the purpose of comparing the results with regulatory standards. Monitoring follows requirements set by regulations, and data are collected in a systematic way for the intended purpose. Monitoring enables agencies to determine whether water bodies are polluted. Much effort is spent per monitoring event, resulting in hundreds of data points typically used solely for comparison with regulatory standards and then stored for little further use. This paper devises a data analysis methodology that can make use of the pre-existing datasets to extract more useful information on water quality trends, without new sample collection and analysis. In this paper, measured lake water quality data are subjected to statistical analyses including Principal Component Analysis (PCA) to deduce changes in water quality spatially and temporally over several years. It was found that the lake as a whole changed temporally by season, rather than spatially. Storm events caused the greatest shifts in water quality, though the shifts were fairly consistent across sampling stations. This methodology can be applied to similar datasets, especially with the recent emphasis by the U.S. EPA on protection of lakes as water sources. Water quality managers using these techniques may be able to lower their monitoring costs by eliminating redundant water quality parameters found in this analysis.     

Identifying critical failure factors of green supply chain management in China’s SMEs with a hierarchical cause–effect model

Environment, Development and Sustainability - Compared to large companies, the small and medium enterprises (SMEs) in China are more likely to fail in developing green supply chain management...     

Nitrous oxide emission by denitrifying phosphorus removal culture using polyhydroxyalkanoates as carbon source

Nitrous oxide (N₂O) emission has been reported to be enhanced during denitrification when internally-stored compounds are used as carbon sources. However, negligible N₂O emissions have been detected in the few studies where polyhydroxyalkanoates (PHA) were specifically used. This study investigated and compared the potential enhancement of N₂O production, based on utilization of an internally-stored polymer and external carbon (acetate) by a denitrifying phosphorus removal culture. Results indicated that at relatively low chemical oxygen demand-to-nitrogen (COD/N) ratios, more nitrite was reduced to N₂O in the presence of an external carbon source as compared to an internal carbon source (PHA). At relatively higher COD/N ratios, similar N₂O reduction rates were obtained in all cases regardless of the type of carbon source available. N₂O reduction rates were, however, generally higher in the presence of an internal carbon source. Results from the study imply that when the presence of an external carbon source is not sufficient to support denitrification, it is likely competitively utilized by different metabolic pathways of denitrifying polyphosphate accumulating organisms (DPAOs) and other ordinary denitrifiers. This study also reveals that the consumption of PHA is potentially the rate-limiting step for N₂O reduction during denitrification.     

Analysis of the association between air pollution and allergic diseases exposure from nearby sources of ambient air pollution within elementary school zones in four Korean cities

The objectives of this study were to survey elementary school students regarding the environmental conditions of their elementary schools and to assess the relationship between air pollution and allergic disease using the International Study of Asthma and Allergies in Childhood (ISAAC) questionnaire. Therefore, this study was designed as a cross-sectional study. In this study, seven elementary schools were selected and they were classified into three categories. The selection included one school with no traffic-related or other pollutants, three with traffic-related pollutants, and three with traffic-related and other pollutants from industrial and filling station sources. The ISAAC questionnaire survey was given to all of the students except to those in the 1st grade who were presumed to be less likely to be exposed to the school environment than the remainder of the students attending those seven schools. The assessment of allergic disease was conducted on a total of 4,545 students. Three school zones with critical exposure were selected within each school and they were evaluated based on the levels of black carbon (BC), PM₁₀, SO₂, NO₂, and O₃. There was a significant increase in the risks based on the odds ratios of treatment experiences (within 1 year) for allergy-related diseases such as asthma and allergic rhinitis (a) in the school group with traffic-related pollutants and the school group with complex pollutants were 2.12 (1.41–3.19) and 1.59 (1.06–2.37), respectively, in comparison to the school groups with no exposure to pollutants. This was determined based on the odds ratio of symptoms and treatment experiences for allergy-related diseases by group based on the home town zone as a reference. Also, in the case of atopic dermatitis, the odds ratio of treatment experiences (within 1 year) was 1.42 (1.02–1.97), which indicated elevated risks compared to the students in the S1 school. A regression analysis was used to assess the relationship between the substances and the symptomatic experiences within the last year. There were significant increases in the odds ratio of the symptoms associated with allergic rhinitis and the BC and SO₂ in the complex pollution areas. The results of the assessment of the relationship between atopic dermatitis-associated symptoms and O3 showed that the odds ratio increased with statistical significance.     

The generation of internal waves by tidal flow over continental shelf/slope topography

Experiments were performed to investigate the generation of internal waves induced by a barotropic tidal flow over continental shelf/slope topography in a two-layer stratified fluid. The interaction of the barotropic tide with the continental slope resulted in the formation of both linear and nonlinear waveforms, ranging from a linear wave of depression to a highly nonlinear internal bolus. The type of wave response was strongly dependent on the tidal forcing intensity and the position of the density interface relative to the shelf depth. Based on the values of the internal Froude number and the layer depth ratio, we delineate four distinct generation regimes, each with a distinct wave response.     

Effect of temperature on VFA’s and biogas production in anaerobic solubilization of food waste

The effectiveness of methane fermentation treatment used in food waste processing is currently limited by solubilization and acidogenesis. In efforts to improve the treatment process, this study examined the effects of temperature on solubilization and acidogenesis. The solubilization rate of food waste, which was based on suspended solid removal, was 47.5%, 62.2%, 70.0%, 72.7%, 56.1% and 45.9% at 15 °C, 25 °C, 35 °C, 45 °C, 55 °C and 65 °C, respectively. Solubilization rate was accelerated from the middle to late experimental periods under mesophilic (35 °C and 45 °C) conditions. In contrast, overall solubilization rate was significantly lower under thermophilic (55 °C and 65 °C) conditions than under mesophilic conditions, although solubilization occurred rapidly in the early experimental period. The production of biogas was high under mesophilic conditions of 35 °C and 45 °C, at 64.7 and 62.7 mL/g-VS, respectively, while it was scarce under thermophilic conditions. Solubilization of food waste was accelerated under both mesophilic and thermophilic conditions; however, solubilization rate was observed to be particularly high under mesophilic conditions, and a shortening of the hydraulic retention time is expected under thermophilic conditions.     

Transport characteristics of gas phase ozone in unsaturated porous media for in-situ chemical oxidation

Encapsulation technology is being investigated as a method for controlling pH in situ at contaminated groundwater sites where pH may limit remediation of organic contaminants. This study examined the effectiveness of using KH2PO4 buffer encapsulated in a pH-sensitive coating to neutralize pH in laboratory sand columns (1.5-1) under a simulated groundwater flow rate and characterized the pattern of capsule release in the flow-through system. Denitrification was used in the columns to increase the pH of the pore water. Each of three columns was equipped with three miniature mesh wells to allow contact of the buffer with column pore water, but capsules (15 g) were inserted into only one column (amended). The two other columns served as amendment (no buffer) and abiotic (no denitrification) controls. Oxidation-reduction potential, dissolved organic and inorganic carbon, NH4+, NO3- +NO2-, PO(4)3-, and pH were measured in the influent, two side ports, and effluent of the columns over time. Near complete conversion of 80 mg N/1 of nitrate and 152 mg/l of ethanol per day resulted in a mean pH increase from 6.2 to 8.2 in the amendment control column. The amended column maintained the target pH of 7.0 +/- 0.2 for 4 weeks until the capsules began to be depleted, after which time the pH slowly started to increase. The capsules exhibited pulses of buffer release, and were effectively dissolved after 7.5 weeks of operation. Base-neutralizing capacity contributed by the encapsulated buffer over the entire study period, calculated as cation equivalents, was 120 mM compared to 8 mM without buffer. This study demonstrates the potential for this technology to mediate pH changes and provides the framework for future studies in the laboratory and in the field, in which pH is controlled in order to enhance organic contaminant remediation by pH-sensitive systems.     

Key factors in chemical reduction by hydrazine for recovery of precious metals

Most of the commonly used metal waste treatment approaches only allow removal of metals which are ultimately discarded as sludge and do not permit the reuse of the metals, resulting in a waste of raw materials. In this study, the recovery of precious metals of sliver and copper in a synthesized wastewater in batch reactors was investigated using a reduction method by hydrazine as the reducing agent. Recovery of metal ions was greatest at pH > 11. The presence of humic acid did not have negative effects on the recovery process. Varying dissolved oxygen levels in the hydrazine solution did not significantly affect the recovery of both metals while seeding and ageing processes resulted in an increase in the particle size of the solid obtained. Under competitive conditions between Cu2+ and Ag+ ions, the recovery of silver remained the same, while that of copper was enhanced.     

Effect of lanthanum loading on nanosized CeO2-ZnO solid catalysts supported on cordierite for diesel soot oxidation

We report the application of a solid lanthanum–ceria–zinc catalyst in the catalytic regeneration of diesel particulate filters(DPF) in diesel engines.We synthesized a CeO_2–ZnO–La_2O_3(Ce–Zn–La) mixed oxide by a lactic acid-mediated sol–gel method,which efficiently coated cordierite substrates for soot capture and combustion.We studied the effects of La loading on the physicochemical and catalytic properties of Ce–Zn mixed oxide during lowtemperature soot combustion processes.We characterized the synthesized catalysts by X-ray diffraction(XRD),Fourier-transform infrared spectroscopy(FTIR),N2 adsorption,Raman spectroscopy,oxygen storage capacity(OSC),and scanning and transmission electron microscopy(SEM and TEM).Thermogravimetric and differential thermal analysis(TGA/DTA)confirmed that the catalysts effectively reduced the soot oxidation temperature.The ternary Ce–Zn–La mixed oxide catalyst with Ce/Zn/La atomic ratio of 2:1:0.5 had the highest catalytic activity and promoted soot oxidation at temperatures below 390°C.This indicated that the large number of oxygen vacancies in the catalyst structure generated oxygen species at low temperatures.Raman spectroscopy measurements revealed the presence of oxygen vacancies and lattice defects in Ce–Zn–La samples,which were key parameters concerning the stability and redox properties of the prepared catalysts.