Comparison of trip average in-vehicle and exterior CO determinations by continuous and grab sampling using an electrochemical sensing method

In air quality monitoring studies, continuous sampling is capable of reflecting real time variation of gas levels, however, with a margin of uncertainty related to the response time of the sensor and to the speed of concentration fluctuation. In contrast, grab sampling allows the determination of average gas concentration over the whole sampling period eliminating thus the uncertainties associated with the continuous method. As studies of in-vehicle carbon monoxide (CO) exposure often show rapidly fluctuating CO levels and are increasingly using the continuous electrochemical sensing method, the present activity aims at validating the suitability of the latter method for this monitoring task. For this purpose, an electrochemical CO sensing monitor was used to continuously monitor CO level inside and outside of a vehicle moving in an urban area, and to analyze the content of concomitantly taken grab samples. Trip-average CO levels measured using the two testing methods were compared. For CO levels higher than the instrument detection limit (1 ppm), the observed percent difference between continuous and grab sampling results varied within a fairly acceptable range (0.6–15.4%). The regression of continuous sampling data against grab sampling data revealed an average error of 6.9%, indicating the suitability of the continuous electrochemical method for monitoring in-vehicle and exterior average CO concentration under typical urban traffic conditions.     

Aerobic biodegradability of methyldiethanolamine (MDEA) used in natural gas sweetening plants in batch tests and continuous flow experiments

Mixtures of different amines including tertiary amines (methyldiethanolamine, MDEA) are commonly used for the removal of CO₂ from gas mixtures or in gas sweetening processes for the extraction of CO₂ and H₂S. The absorber solutions used can be released into the industrial waste water due to continuous substitution of degraded MDEA, periodically cleaning processes or an accidental spill. In this study, the aerobic biodegradability of MDEA was investigated in a standardised batch test and a continuous flow experiment (40 l/d). The results of the batch test indicated that the MDEA-solution was non-biodegradable during the test period of 28 days, whereas the continuous flow experiments showed biodegradation of more than 96% based on TOC-measurements. This was probably due to the adaptation of the microorganisms to this particular waste water contamination during continuous flow experiment.     

Site-specific water quality guidelines: 2. Development of a water quality regulation framework for pulse exposures of mine water discharges at a uranium mine in northern Australia

The Ranger Uranium Mine, in northern Australia, is monitored by the Supervising Scientist Division (SSD) of the Australian Government to ensure that it does not impact on the highly valued aquatic ecosystems of Kakadu National Park. In 2010, the SSD adopted the continuous monitoring of electrical conductivity (EC) and turbidity, in combination with event-triggered automated grab samples, as its primary water quality monitoring method. The continuous monitoring of EC has shown that mine discharges typically occur over short-term ‘pulse’ durations of minutes to hours. Given that magnesium (Mg) is the most likely mine-derived solute to approach or exceed the applicable water quality limit value, the focus has been on developing a pulse exposure assessment framework for Mg, as represented by its proxy EC, which is tracked by the continuous monitoring system. This study presents a possible ecotoxicologically derived Mg pulse exposure limit and trigger regulation framework for Magela and Gulungul Creeks and an assessment of historic continuous monitoring EC data from these creeks. This framework demonstrates potential to supersede the current EC guideline and associated trigger levels, which are statistically derived from historic grab sample data.     

Continuous Emission Monitoring: Objectives and Requirements

Regulations were recently proposed by the Environmental Protection Agency which, when promulgated, will require existing and new sources within certain specified source categories to install, operate, and maintain continuous emission monitoring systems. Major comments received on these proposed regulations are discussed as are the overall benefits that can be derived from the utilization of continuous emission monitoring systems.     

Free-air fumigation of mature trees. A novel system for controlled ozone enrichment in grown-up beech and spruce canopies

A novel system for continuous and controlled free-air fumigation of mature tree canopies with ozone is described. Ozone generated from oxygen is diluted with air in a pressurized tank and conducted into the canopies by a system of 100 PTFE tubes hanging down from a grid fixed above the crowns. With 45 calibrated outlets per tube providing a constant flow of 0.3 l/min each, a total volume of about 10*10*15 m3 comprising 5 beech and 5 spruce canopies is fumigated. The spatial ozone distribution in the fumigated volume as well as surrounding reference tree canopies is controlled by continuous measuring instruments installed at 4 levels and a dense array of passive samplers. The system will later be used for CO2 fumigation as well. Results of the first year of continuous operation, with 2 * ambient ozone levels having been achieved, are reported.     

Field Measurements of Particulate Matter Emissions,Carbon Monoxide,and Exhaust Opacity from Heavy-Duty Diesel Vehicles

ABSTRACT

Diesel particulate matter (PM) is a significant contributor to ambient air PM₁₀ and PM_2.5 particulate levels. In addition, recent literature argues that submicron diesel PM is a pulmonary health hazard. There is difficulty in attributing PM emissions to specific operating modes of a diesel engine, although it is acknowledged that PM production rises dramatically with load and that high PM emissions occur during rapid load increases on turbocharged engines. Snap-acceleration tests generally identify PM associated with rapid transient operating conditions, but not with high load. To quantify the origin of PM during transient engine operation, continuous opacity measurements have been made using a Wager 650CP full flow exhaust opacity meter. Opacity measurements were taken while the vehicles were operated over transient driving cycles on a chassis dynamometer using the West Virginia University (WVU) Transportable Heavy Duty Vehicle Emissions Testing Laboratories. Data were gathered from Detroit Diesel, Cummins, Caterpillar, and Navistar heavy-duty (HD) diesel engines. Driving cycles used were the Central Business District (CBD) cycle, the WVU 5-Peak Truck cycle, the WVU 5-Mile route, and the New York City Bus (NYCB) cycle. Continuous opacity measurements, integrated over the entire driving cycle, were compared to total integrated PM mass. In addition, the truck was subjected to repeat snap-acceleration tests, and PM was collected for a composite of these snap-acceleration tests. Additional data were obtained from a fleet of 1996 New Flyer buses in Flint, MI, equipped with electronically controlled Detroit Diesel Series 50 engines. Again, continuous opacity, regulated gaseous emissions, and PM were measured. The relationship between continuous carbon monoxide (CO) emissions and continuous opacity was noted. In identifying the level of PM emissions in transient diesel engine operation, it is suggested that CO emissions may prove to be a useful indicator and may be used to apportion total PM on a continuous basis over a transient cycle. The projected continuous PM data will prove valuable in future mobile source inventory prediction.     

Evaluation of Continuous Performance Monitoring Techniques for Hazardous Waste Incinerators

This paper discusses monitoring the waste destruction efficiency of hazardous waste incinerators. The particular problem is to ensure that incinerators do not release, without detection, significant quantities of waste as a result of operating fluctuations or equipment degradation. To detect these conditions, continuous, automated, and real-time source monitoring is required. Detection of degraded performance by monitoring and measuring waste compounds directly is not presently possible on a continuous basis. An alternative is to use commercially available continuous monitors to measure combustion intermediates (e.g., CO or hydrocarbons) and thereby infer waste destruction efficiency. Required, however, is a correlation between the emission of intermediates and the emission of waste. In this paper, the response of a number of these continuous monitors is compared with waste destruction efficiency measurements from a laboratory scale, liquid-spray incinerator operated on fuel oil doped with model waste compounds: benzene, chlorobenzene, acrylonitrile, and chloroform. Total hydrocarbon and CH₄ measurements are found to vary with waste emission in a nearly linear manner; however, a substantial increase in CO emission occurs before a significant amount of waste is released. These results suggest that CO may serve as an indicator of the approach of waste release, while total hydrocarbons may provide an indicator of immediate waste release.     

连续/间歇曝气改良一体化氧化沟处理生活污水对比试验研究

为了提高改良一体化氧化沟(MIOD)的除磷效率和降低运行能耗,分别对连续曝气和间歇曝气(曝气1 h/停曝1 h)2种运行方式下系统处理生活污水的效果进行了对比试验研究.结果表明:(1)连续曝气运行方式下系统对COD、NH3-N、TP的去除率分别为85.28％、91.14％、73.09％；间歇曝气运行方式下系统对COD、...     

Acute and chronic toxicity of triphenyltin hydroxide to fathead minnows (Pimephales promelas) following brief or continuous exposure

Fathead minnow larvae (Pimephales promelas) were exposed to triphenyltin hydroxide (TPTH) during brief (single pulse) or continuous exposure in 96-h and 30-day toxicity tests. The continuous exposure 96-h LC(50) value was 7.1 microg litre(-1). Brief exposures for 12 to 72-h gave 96-h LC(50) values that ranged from 61.8 to 6.0 microg litre(-1), respectively. The continuous exposure 30-day chronic effect concentration, based upon reduced growth, was 0.23 microg litre. Survival was significantly reduced at 2.0 microg litre(-1). Brief exposures for 24, 48, and 72-h in 30-day tests significantly reduced survival and growth at 13.0, 13.0 and 60.0 microg litre(-1) respectively. It is suggested that both toxicant concentration and exposure duration are important factors to consider in the risk assessment of potential pesticide hazards in the environment.     

Mitigating Global Warming Potentials of Methane and Nitrous Oxide Gases from Rice Paddies under different irrigation regimes

A field experiment was conducted in Bangladesh Agricultural University Farm to investigate the mitigating effects of soil amendments such as calcium carbide, calcium silicate, phosphogypsum, and biochar with urea fertilizer on global warming potentials (GWPs) of methane (CH₄) and nitrous oxide (N₂O) gases during rice cultivation under continuous and intermittent irrigations. Among the amendments phosphogypsum and silicate fertilizer, being potential source of electron acceptors, decreased maximum level of seasonal CH₄ flux by 25–27 % and 32–38 % in continuous and intermittent irrigations, respectively. Biochar and calcium carbide amendments, acting as nitrification inhibitors, decreased N₂O emissions by 36–40 % and 26–30 % under continuous and intermittent irrigations, respectively. The total GWP of CH₄ and N₂O gases were decreased by 7–27 % and 6–34 % with calcium carbide, phosphogypsum, and silicate fertilizer amendments under continuous and intermittent irrigations, respectively. However, biochar amendments increased overall GWP of CH₄ and N₂O gases.     

Comparison of real-time instruments used to monitor airborne particulate matter

Measurements collected using five real-time continuous airborne particle monitors were compared to measurements made using reference filter-based samplers at Bakersfield, CA, between December 2, 1998, and January 31, 1999. The purpose of this analysis was to evaluate the suitability of each instrument for use in a real-time continuous monitoring network designed to measure the mass of airborne particles with an aerodynamic diam less than 2.5 microns (PM2.5) under wintertime conditions in the southern San Joaquin Valley. Measurements of airborne particulate mass made with a beta attenuation monitor (BAM), an integrating nephelometer, and a continuous aerosol mass monitor (CAMM) were found to correlate well with reference measurements made with a filter-based sampler. A Dusttrak aerosol sampler overestimated airborne particle concentrations by a factor of approximately 3 throughout the study. Measurements of airborne particulate matter made with a tapered element oscillating microbalance (TEOM) were found to be lower than the reference filter-based measurements by an amount approximately equal to the concentration of NH4NO3 observed to be present in the airborne particles. The performance of the Dusttrak sampler and the integrating nephelometer was affected by the size distribution of airborne particulate matter. The performance of the BAM, the integrating nephelometer, the CAMM, the Dusttrak sampler, and the TEOM was not strongly affected by temperature, relative humidity, wind speed, or wind direction within the range of conditions encountered in the current study. Based on instrument performance, the BAM, the integrating nephelometer, and the CAMM appear to be suitable candidates for deployment in a real-time continuous PM2.5 monitoring network in central California for the range of winter conditions and aerosol composition encountered during the study.     

畜禽沼液中抗生素和激素的微波处理

通过间歇处理和连续处理实验，探讨微波技术对沼液中四环素类抗生素和激素喹乙醇去除的效果。结果表明，沼液在微波间歇处理中，最优反应时间为40min。此条件下沼液中喹乙醇、土霉素、四环素和金霉素的去除率分别达到26％、49％、48％和70％；微波可显著提高可生化性，BOD5／COD值达到0．37。微波一好氧处理系统中COD与氨氮的去除率分别达到91％和93％，明显优于单独好氧处理。沼液微波连续处理中，最优HRT为90min，此时喹乙醇、土霉素、四环素和金霉素的去除率分别达到24％、45％、50％和74％；BOD5／COD值达到0．34。微波．好氧处理系统中COD与氨氮的去除率均为90％，优于单独好氧处理效果。     

Certification of a long-term sampling system for PCDFs and PCDDs in the flue gas from industrial facilities

AMESA (adsorption method for sampling of dioxins) is a fully automatic system for long term monitoring of dioxin emissions from industrial processes based on the adsorption method. The system has been tested and undergoing a certification procedure according to the German guidelines for certification of systems for continuous monitoring of special substances. The certification covered parameters such as disposability of the system, reproducibility of the results and comparability of the sampling method with German and European standard methods. Furthermore break through, blanks and sample storability were investigated. The results prove that AMESA is a state of the art sampling system for continuous monitoring of dioxin/furan emissions.     

Ambient ozone (O3) in three Class I wilderness areas in the northeastern USA: measurements with Ogawa passive samplers

Ambient ozone (O(3)) was measured in two Class I wilderness areas, one within the White Mountain National Forest in north central New Hampshire (NH) and one within the Green Mountain National Forest in southwestern Vermont (VT), for six weeks between 5 July and 16 August 1994, using Ogawa passive nitrite-coated filter samplers and a one week exposure period each time. Results for 7-day mean ambient O(3) concentrations from the passive samplers were compared to results from a co-located continuous ultraviolet photometric O(3) analyzer both in NH and VT. Although the size of the data set was small, agreement through simple linear regression between mean 7-day O(3) concentrations determined by the continuous monitors, and those obtained from the passive samplers was generally very good (adjusted R(2) = 0.759; p = 0.0003). Overall, excluding the one outlier value, any observed differences in the results obtained by the two methods when comparing co-located passive samplers to the continuous monitor within a given study location, appeared to be solely due to experimental error.     

Measurement of ammonia emissions using various techniques in a comparative tunnel study

A field-based intercomparison study for ammonia measurements was conducted using seven analytical methods. It included sulphuric acid impinger, citric acid denuder, differential optical absorption spectroscopy (DOAS), Fourier transform infrared spectroscopy (FTIR), photoacoustic spectroscopy (PAS), and continuous aqueous extraction followed by measurement of conductivity (Airrmonia). Measurements were done at the entrance and the exit of the Gubrist highway tunnel near Zurich, Switzerland. For DOAS, FTIR, PAS and Airrmonia, 24 hour means were calculated based on a time resolution of 10 minutes. At the tunnel exit, all 24 hour averages were within 13%, and the continuous data of the time-resolved methods agreed well. At the tunnel entrance, a slightly reduced method comparison included four methods, and daily mean values agreed within 23%. Ammonia emission factors, based on 4 weeks of continuous measurements with the Airrmonia, were 31 ± 4 mg km^-1 for light-duty vehicles and 14 ± 7 mg km^-1 for heavy-duty vehicles.     

定电位电解二氧化硫传感器特性研究

选用了3SF定电位电解型传感器作为二氧化硫连续在线监测探头。通过对该传感器各项特性指标的研究表明：该传感器在0～2500mg／m^3测量范围内,输出信号线性相关系数为0．9989,零点漂移为0．64％F．S．,相对准确度最大偏差为28mg／m^3,响应时间为30s,以上特性符合国家HJ／T76—2001标准中对二氧化硫传感器的各项指标要求,试验研究表明该传感器可用于二氧化硫连续在线监测。     

Continuous Monitoring for Sulfur Dioxide at A Utility Boiler Equipped with a Limestone Scrubber

The results of a 30-day sulfur dioxide monitoring program conducted at a utility boiler equipped with a limestone scrubber are presented. Program objectives were twofold: to demonstrate the reliable use of continuous monitoring equipment for determining scrubber performance and to support the proposed New Source Performance Standards (NSPS) published in the September 19, 1978, Federal Register. In general, continuous monitoring equipment is reliable as a source surveillance method. Results of the data collected indicate that the test site monitored was capable of performing under the guidelines of the proposed NSPS, and were incorporated in the final NSPS promulgated on June 11, 1979.     

Continuous hydrodynamic mixing weakens the dominance of Microcystis: evidences from microcosm and lab experiments

Environmental Science and Pollution Research - Hydrodynamic mixing is one of the important environment factors in determining phytoplankton community compositions. Here the influences of continuous...     

Substrate loading rates conducive to nitritation in entrapped cell reactors: performance and microbial community structure

Environmental Science and Pollution Research - This study aimed to elucidate the boundaries of ammonia and organic loading rates that allow for nitritation in continuous flow...