Comparison of Real-Time Instruments Used To Monitor Airborne Particulate Matter

ABSTRACT

Measurements collected using five real-time continuous airborne particle monitors were compared to measurements made using reference filter-based samplers at Bakers-field, 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 μm (PM_2.5) 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 ~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 PM_2.5 monitoring network in central California for the range of winter conditions and aerosol composition encountered during the study.     

Biodegradable Chitosan-g-Poly(methacrylamide) Microspheres for Controlled Release of Hypertensive Drug

Chitosan-g-poly(methacrylamide) (CS-g-PMAAm) was synthesized by redox polymerization. The synthesized graft copolymers were used to prepare microspheres (MS) by water/oil (W/O) emulsion technique and cross-linked with glutaraldehyde (GA). Developed microspheres were encapsulated using enalapril maleate (ENAM) as a model drug (hypertension) and characterized by fourier transform infrared spectroscopy, differential scanning calorimetry and scanning electron microscopy. The physico-chemical properties of the microspheres were studied by calculating drug entrapment efficiency, and drug release kinetics. % of encapsulation efficiency (% EE) increased with increase in drug loading and methacrylamide (MAAm) content. The minimum % EE (65.2 ± 1.6) was observed in case of microsphere containing 40 % MAAm, 5 % ENAM and 10 mL glutaraldehyde. The release profiles indicate that formulation containing highest (10 mL) crosslinking agent microspheres has the slow release.     

Toxicity of carbaryl, diquat dibromide, and fluoranthene, individually and in mixture, to larval grass shrimp, Palaemonetes pugio

This study examined the toxicity of two pesticides (carbaryl and diquat dibromide) and one polycyclic aromatic hydrocarbon (fluoranthene), both singly and in mixture, to grass shrimp larvae (Palaemonetes pugio). These three chemicals are all present in coastal environments and can easily enter estuarine ecosystems. Fluoranthene was the most toxic chemical with a 96-h LC50 value of 32.45 microg/L, followed by carbaryl (43.02 microg/L) and diquat dibromide (1624 microg/L). In the chemical mixture tests, the binary carbaryl/diquat dibromide mixture and the ternary carbaryl/diquat dibromide/fluoranthene mixture had additive results.     

Process plant safety information repository and support for safety applications

The consideration of safety of processing plants from design to operation involves many tasks. Different techniques and tools have been developed to assist in carry out those tasks. With the advances in computing technologies, both in hardware and software, there is the opportunity to bring together the vast amount of engineering, hazard and risk data and handle them in an efficient way to manage and improve safety throughout the life time of a plant. This paper proposes keeping such data in a process plant safety information repository which can be easily accessed by different safety-related tools to enhance the efficiency of safety identification and analysis tasks.     

Observations of Dust-Storms in China, Mongolia and Associated Dust Falls in Korea in Spring 2003

A joint monitoring of dust-storms that occurred in East Asia from March until May 2003 has been carried. Our discussions include dust-storm observations in the source areas of China and Mongolia, and measurements with satellites and ground monitors in central Korea. Differences were found in the definition and measurement of dust-storms. Over the source area of Mongolia there were 6 dusty days in March, 18 days in April, and 10 dusty days in May. In Inner Mongolia of northern China there were 4 dust-storms with 14 dusty days observed over the three months. In central Korea, a sink area, there were 4 cases of weak dust-storm and 17 dusty days in the spring of 2003. The highest PM10 value was 607 μgm⁻³ and PM 2.3 was 149 μgm⁻³, respectively. These observations identify the growing need for further universal observation practices and dust-storm reporting in future. Observations indicated that snow covered the central part of the Gobi Desert, near the boundary of China and Mongolia, from December until mid-March. This is in contrast to other years when the Gobi was relatively wet, producing unfavourable conditions for the formation of intense dust-storms. In addition, the very strong winds associated with intense cyclones and anticyclones were not apparent and the systems shifted northward during the spring. As a result, the frequency and intensity of observed dust-storms in 2003 in this region were very low. This confirms that there is variability in the frequency of dust-storm formation due to the current process of desertification and climate change.     

Environmental Conditions of Dust Events in Northern China during 2000–2001

To investigate the large-scale environmental conditions of duststorms occurring in Northern China, a synoptic situation of tendust events in Northern China during 2000–2001 was composed andits dynamic features were identified. The composite synoptic situation showed that the occurrence of the ten dust events was associated with the eastward movement of a strong cold high fromMongolia, and the development of a cyclone in Northeast China, which caused the pressure gradient to intensify considerably in Northern China. The upper level circulation revealed that a 500 hPa trough developed rapidly above Northern China, and diagnosis showed that composite ascending motion was pronouncedabove the Siberian district. The change of vertical motion in themiddle and low troposphere above Mongolia was also related to theoccurrence of the ten dust events. When the descendingcurrent, 12 hr before the occurrence, was completely replacedby the ascending current, the instable atmospheric stratificationof the lower troposphere enabled dry dust to be transported from the surface to high altitudes toward Northern China.     

Drought Resilience of the California Central Valley Surface‐Ground‐Water‐Conveyance System1

Abstract: A series of drought simulations were performed for the California Central Valley using computer applications developed by the California Department of Water Resources and historical datasets representing a range of droughts from mild to severe for time periods lasting up to 60 years. Land use, agricultural cropping patterns, and water demand were held fixed at the 2003 level and water supply was decreased by amounts ranging between 25 and 50%, representing light to severe drought types. Impacts were examined for four hydrologic subbasins, the Sacramento Basin, the San Joaquin Basin, the Tulare Basin, and the Eastside Drainage. Results suggest the greatest impacts are in the San Joaquin and Tulare Basins, regions that are heavily irrigated and are presently overdrafted in most years. Regional surface water diversions decrease by as much as 70%. Stream‐to‐aquifer flows and aquifer storage declines were proportional to drought severity. Most significant was the decline in ground water head for the severe drought cases, where results suggest that under these scenarios the water table is unlikely to recover within the 30‐year model‐simulated future. However, the overall response to such droughts is not as severe as anticipated and the Sacramento Basin may act as ground‐water insurance to sustain California during extended dry periods.     

Applying Zonation Methods and Tabu Search to Improve the Ground‐Water Modeling1

Abstract: An optimization procedure combining zonation methods with the Tabu Search method is proposed to identify the spatial distribution of hydraulic conductivity field. Three zonation methods, Voronoi diagram (VD), multiplicatively weighted Voronoi diagram (MWVD), and pattern zonation are adopted for the parameterization purposes. With the consideration of the homogeneity and the heterogeneity, there are four spatial distributions of hydraulic conductivity designed to test whether the parameter structure can be successfully identified. The fitting residual error is first considered to determine an adequate number of zones without over parameterization. Then, the parameter uncertainty is evaluated the decision of the number of zones. The results indicate that the MWVD performs better than other two methods because the MWVD has better flexibility in describing the zonal boundaries with small number of decision variables.