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Open Access Publications from the University of California

This series is home to publications and data sets from the Center for Environmental Research and Technology at the University of California, Riverside.

Cover page of Impact of aerosols on reservoir inflow: A case study for Big Creek Hydroelectric System in California

Impact of aerosols on reservoir inflow: A case study for Big Creek Hydroelectric System in California

(2018)

© 2018 John Wiley & Sons, Ltd. Accurate and reliable reservoir inflow forecast is instrumental to the efficient operation of the hydroelectric power systems. It has been discovered that natural and anthropogenic aerosols have a great influence on meteorological variables such as temperature, snow water equivalent, and precipitation, which in turn impact the reservoir inflow. Therefore, it is imperative for us to quantify the impact of aerosols on reservoir inflow and to incorporate the aerosol models into future reservoir inflow forecasting models. In this paper, a comprehensive framework was developed to quantify the impact of aerosols on reservoir inflow by integrating the Weather Research and Forecasting model with Chemistry (WRF-Chem) and a dynamic regression model. The statistical dynamic regression model produces forecasts for reservoir inflow based on the meteorological output variables from the WRF-Chem model. The case study was performed on the Florence Lake and Lake Thomas Alva Edison of the Big Creek Hydroelectric Project in the San Joaquin Region. The simulation results show that the presence of aerosols results in a significant reduction of annual reservoir inflow by 4–14%. In the summer, aerosols reduce precipitation, snow water equivalent, and snowmelt that leads to a reduction in inflow by 11–26%. In the spring, aerosols increase temperature and snowmelt which leads to an increase in inflow by 0.6–2%. Aerosols significantly reduce the amount of inflow in the summer when the marginal value of water is extremely high and slightly increase the inflow in the spring when the run-off risk is high. In summary, the presence of aerosols is detrimental to the optimal utilization of hydroelectric power systems.

Cover page of Secondary organic aerosol formation and organic nitrate yield from NO3oxidation of biogenic hydrocarbons

Secondary organic aerosol formation and organic nitrate yield from NO3oxidation of biogenic hydrocarbons

(2014)

© 2014 American Chemical Society. The secondary organic aerosol (SOA) mass yields from NO3oxidation of a series of biogenic volatile organic compounds (BVOCs), consisting of five monoterpenes and one sesquiterpene (α-pinene, β-pinene, Δ-3-carene, limonene, sabinene, and β-caryophyllene), were investigated in a series of continuous flow experiments in a 10 m3indoor Teflon chamber. By making in situ measurements of the nitrate radical and employing a kinetics box model, we generate time-dependent yield curves as a function of reacted BVOC. SOA yields varied dramatically among the different BVOCs, from zero for α-pinene to 38-65% for Δ-3-carene and 86% for β-caryophyllene at mass loading of 10 μg m-3, suggesting that model mechanisms that treat all NO3+ monoterpene reactions equally will lead to errors in predicted SOA depending on each location's mix of BVOC emissions. In most cases, organonitrate is a dominant component of the aerosol produced, but in the case of α-pinene, little organonitrate and no aerosol is formed.

Cover page of Volatilizable biogenic organic compounds (VBOCs) with two dimensional gas chromatography-time of flight mass spectrometry (GC × GC-TOFMS): Sampling methods, VBOC complexity, and chromatographic retention data

Volatilizable biogenic organic compounds (VBOCs) with two dimensional gas chromatography-time of flight mass spectrometry (GC × GC-TOFMS): Sampling methods, VBOC complexity, and chromatographic retention data

(2012)

Two dimensional gas chromatography (GC × GC) with detection by time-of-flight mass spectrometry (TOFMS) was applied in the rapid analysis of air samples containing highly complex mixtures of volatilizable biogenic organic compounds (VBOCs). VBOC analytical methodologies are briefly reviewed, and optimal conditions are discussed for sampling with both adsorption/thermal desorption (ATD) cartridges and solid-phase microextraction (SPME) fibers. Air samples containing VBOC emissions from leaves of two tree species (Cedrus atlantica and Calycolpus moritzianus) were obtained by both ATD and SPME. The optimized gas chromatographic conditions utilized a 45 m, 0.25 mm I.D. low-polarity primary column (DB-VRX, 1.4 μm film) and a 1.5 m, 0.25 mm I.D. polar secondary column (Stabilwax™, 0.25 μm film). Excellent separation was achieved in a 36 min temperature programmed GC × GC chromatogram. Thousands of VBOC peaks were present in the sample chromatograms; hundreds of tentative identifications by NIST mass spectral matching are provided. Very few of the tentatively identified compounds are currently available as authentic standards. Minimum detection limit values for a 5 l ATD sample were 3.5 pptv (10 ng mg-3) for isoprene, methyl vinyl ketone, and methacrolein, and ∼1.5 pptv (∼10 ng mg-3) for monoterpenes and sesquiterpenes. Kovats-type chromatographic retention index values on the primary column and relative retention time values on the secondary column are provided for 21 standard compounds and for 417 tentatively identified VBOCs. 19 of the 21 authentic standard compounds were found in one of the Cedrus atlantica SPME samples. In addition, easily quantifiable levels of at least 13 sesquiterpenes were found in an ATD sample obtained from a branch enclosure of Calycolpus moritzianus. Overall, the results obtained via GC × GC-TOFMS highlight an extreme, and largely uncharacterized diversity of VBOCs, consistent with the hypothesis that sesquiterpenes and other compounds beyond the current list of typically determined VBOC analytes may well be important contributors to global atmospheric levels of organic particulate matter. © Author(s) 2012.

Cover page of Validation Testing for the PM-PEMS Measurement Allowance Program

Validation Testing for the PM-PEMS Measurement Allowance Program

(2010)

The United States Environmental Protection Agency (EPA) and California Air Resources Board (CARB) agencies are implementing a series of regulations that will control emissions, including oxides of nitrogen (NOx) and particulate matter (PM), from diesel engines during “in-use” conditions. The purpose is to ensure the emission standards can be maintained throughout the course of the engine’s useful lifetime. One of the most important regulations with respect to controlling in-use emissions is the Not-To-Exceed (NTE) regulation. This regulation sets limits for pollutants that are emitted during operation in a defined portion of the engine map and specifies the protocols required to make those measurements. Portable Emissions Measurement Systems (PEMS) are critical for the implementation of these in-use regulations. The EPA, CARB, and the Engine Manufacturers Association (EMA) formed a measurement allowance steering committee (MASC) to develop a “measurement allowance” to account for measurement error associated with the use of PEMS for in-use measurements. A comprehensive program was completed for the gas-phase measurement allowance (Miller et al., 2008; Buckingham et al. 2007; Fiest et al. 2007). This report presents the results of the in-use validation portion of the PM measurement allowance program. The MASC approach pursued an experimental program to try to use laboratory measurements and modeling to characterize errors that might be observed with in-use, and then validate those errors with in-use testing. The development of the MA involved a sophisticated Monte Carlo model that considered laboratory measurement errors associated with engine broadcast information, emissions measurements, affects due to ambient conditions, and affects that might be observed due to on-vehicle operating conditions. The in-use validation effort used the same PEMS systems used for the laboratory testing, but under real-world conditions. The idea was that the errors found in-use should be within the bounds of the proposed MA. For this program, comparisons were made between the PM PEMS and UCR’s Mobile Emissions Laboratory (MEL) reference laboratory under in-use on-road driving conditions. The MEL is unique in that it contains a full 1065 compliant constant volume sampling (CVS) system with gravimetric PM measurements, while being fully operational under on-the-road driving conditions. Two PEMS manufacturers were selected for the in-use validation testing, and multiple serial numbers of each of the selected PEMS were included in the in-use testing. Measurements were made from one class 8 heavy-duty diesel vehicle equipped with a original equipment manufacturer (OEM) diesel particulate filter (DPF). A bypass system was designed to simulate a failed DPF while maintaining the functionality of the diesel oxidation catalyst (DOC). The bypass was designed to target an in-use bsPM emission level of 25 mg/hp-h. In-use routes were designed and utilized to exercise the PM PEMS equipment over a range of environmental conditions, and included segments near sea level, in coastal regions, in desert regions, and longer uphill incline segments and segments at elevations up to 4500 ft. Prior to validation testing, the MEL underwent a series of 1065 audits and a cross laboratory correlation with SwRI. All PM PEMS and PM instruments tested showed a negative bias compared to the reference system. The PEMS2 non-regeneration mean bias at the 20 mg/hp-h bsPM emissions was -10 mg/hp-h, and at 30 mg/hp-h the mean bias was -18 mg/hp-h. When the intercept was forced through zero, the mean bias at 20 mg/hp-h went to -15 mg/hp-h. The PEMS3 non-regeneration mean bias at the 20 mg/hp-h bsPM emissions was -1.7 mg/hp-h, and at 30 mg/hp-h the mean bias was -2.2 mg/hp-h. When the intercept was forced through zero, the PEMS3 mean bias went to -1 mg/hp-h at the 20 mg/hp-h level. The other instruments used showed a higher mean bias than PEMS3 and lower mean bias than PEMS2. The proposed bsPM MA is 6 mg/hp-h at the 20 mg/hp-h in-use standard. For these results, the PEMS3 system was within the proposed MA, while the PEMS2 values exceeded the proposed MA. Several issues were discovered during testing, including problems related to testing under in-use conditions, operational issues, and post processing issues. The in-use issues ranged from electrical and mechanical connections, crystal usage from short NTE’s, valve switching, measurement signals, and crystal behaviors. Operational problems occurred during startup, commissioning, and with the systems prior to testing in-use. Typical issues include incorrect system configurations, procedures that don’t work, and issues with the startup software and other recommended practices that didn’t function according to the manual. The post processing issues ranged from data filtering, bsPM differences between processor versions, data identification, and method calculations not being available. In general, PEMS2 had more issues than PEMS3 for each of these categories.

Cover page of PM PEM’s On-Road Investigation – With and Without DPF Equipped Engines

PM PEM’s On-Road Investigation – With and Without DPF Equipped Engines

(2009)

Regulatory agencies are in the process of implementing an in-use testing program for heavy-duty diesel vehicles that will include testing with portable emissions measurement systems (PEMS) under in-use driving conditions. An important aspect of this regulation is the Measurement Allowance program where EPA, CARB, and the Engine Manufacturers Association (EMA) are working together to systematically evaluate various sources of error for gaseous and PM measurements with PEMS in comparison with laboratory measurements. This error is then accounted for in the regulatory standards as a “Measurement Allowance”. A comprehensive program has already been conducted for the gas-phase measurement allowance, with the PM measurement allowance program about to begin. The main objective of this work was to provide preliminary measurements from PM PEMS to assess the accuracy of PM measurements under in-use conditions and provide a basis for the development of the more comprehensive Measurement Allowance program. The MASC utilized the University of California, Riverside (UCR) Bourns College of Engineering – Center for Environmental Research and Technology’s (CE-CERT) Mobile Emissions Laboratory (MEL) to perform the initial in-use PM PEMS evaluation. For this program, PM PEMS were directly compared with the MEL over a series of different onroad driving conditions. Prior to the on-road testing, MEL underwent a 40CFR Part 1065 selfaudit focused on PM sampling. In-use measurements were made from three different Class 8 tractors representing three different engine manufactures. One truck had a 2000 Caterpillar engine without a DPF and the other two were equipped with OEM DPFs, one from Cummins and the other from Volvo. Each of the 2007 vehicles was modified to vary their emission levels using regeneration, ECM recalibrations, and a DPF bypass. The on-road driving courses included segments near sea level, in coastal regions, in desert regions, and on longer uphill inclines. The goal was to test the vehicle at or slightly above the Not-To-Exceed (NTE) threshold to investigate sources of error for the PM instruments at levels where their performance is most critical. The bsPM level varied from 0.1 g/hp-h to 0.0003 g/hp-h over the different vehicles and operating conditions where one vehicle had high EC, one had high OC, and another had a substantial amount of sulfate. In addition to varying composition and bsPM level, one of the vehicles showed a significant reduction in particle size thus challenging the PM PEMS measurement systems. PM measurements in real-time were made with a variety of different PM instruments from manufacturers preparing for the PM Measurement Allowance program, including a Horiba OBSTRPM system, a Sensors SemtechDS PPMD (QCM), and an AVL Photoacoustic MicroSoot Sensor, as well as other commercially available instruments such as a Dekati DMM and TSI Dustrak. These measurements were directly compared with gravimetric PM mass measurements that were collected with the MEL under 1065 compliant sampling conditions. Measurements were made under conditions where NTE events would be expected (e.g., uphill driving segments) and for varying durations to provide a range of mass loadings. The results of this study are expected to be an important component of PM Measurement Allowance program development.

Cover page of Rheological Study of Comingled Biomass and Coal Slurries with HydrothermalPretreatment

Rheological Study of Comingled Biomass and Coal Slurries with HydrothermalPretreatment

(2009)

Gasification of comingled biomass and coal feedstock is an effective means of reducing the net life cycle greenhouse gas emissions in the coal gasification process while maintaining its inherent benefits of abundance and high-energy density. However, feeding a comingled biomass and coal feedstock into a pressurized gasification reactor poses a technical problem. Conventional dry feeding systems, such as lock hoppers and pressurized pneumatic transport, are complex and operationally expensive. A slurry formation of comingled biomass and coal feedstock can be easily fed into the gasification reactor but, in normal conditions, only allows for a small portion of biomass in the mixture. This is a consequence of the hydroscopic and hydrophilic nature of the biomass. The College of Engineering Center for Environmental Research and Technology (CE-CERT) at the University of California, Riverside, has developed a process producing high solid content biomass-water slurry using a hydrothermal pretreatment process. In this paper, the systematic investigation of the rheological properties (e.g., shear rate, shear stress, and viscosity) of coal-water slurries, biomass-water slurries, and comingled biomass and coal-water slurries is reported. The solid particle size distribution in the slurry and the initial solid/water ratio were investigated to determine the impact on shear rate and viscosity. This was determined using a rotational rheometer. The experimental results show that larger particle size offers better pumpability. The presence of a high percentage of biomass in solid form significantly decreases slurry pumpability. It is also shown that the solid loading of the biomass-water slurry can be increased to approximately 35 wt%with viscosity of less than 0.7 Pa 3 s after the pretreatment process. The solid loading increased to approximately 45 wt%when the biomass is comingled with coal.

Cover page of Secondary Organic Aerosol Formation from Primary Aliphatic Amines with Nitrate Radical

Secondary Organic Aerosol Formation from Primary Aliphatic Amines with Nitrate Radical

(2009)

Primary aliphatic amines are an important class of nitrogen containing compounds emitted from automobiles, waste treatment facilities and agricultural animal operations. A series of experiments conducted at the UC-Riverside/CECERT Environmental Chamber is presented in which oxidation of methylamine, ethylamine, propylamine, and butylamine with O3 and NO3 have been investigated. Very little aerosol formation is observed in the presence of O3 only. However, after addition of NO, and by extension NO3, large aerosol mass yields (44% for butylamine) are seen. Aerosol generated was determined to be organic in nature due to the small fraction of NO and NO2 in the total signal (<1% for all amines tested) as detected by an aerosol mass spectrometer (AMS). We propose a reaction mechanism between carbonyl containing species and the parent amine leading to formation of particulate imine products. These findings can have significant impacts on rural communities with elevated nighttime PM loadings, when significant levels of NO3 exist.

Cover page of PM PEM’s Pre-Measurement Allowance – On-Road Evaluation and Investigation

PM PEM’s Pre-Measurement Allowance – On-Road Evaluation and Investigation

(2009)

Regulatory agencies are in the process of implementing an in-use testing program for heavy-duty diesel vehicles that will include testing with portable emissions measurement systems (PEMS) under in-use driving conditions. An important aspect of this regulation is the Measurement Allowance program where EPA, CARB, and the Engine Manufacturers Association (EMA) are working together to systematically evaluate various sources of error for gaseous and PM measurements with PEMS in comparison with laboratory measurements. This error is then accounted for in the regulatory standards as a “Measurement Allowance”. A comprehensive program has already been conducted for the gas-phase measurement allowance, with the PM measurement allowance program about to begin. The main objective of this work was to provide preliminary measurements from PM PEMS to assess the accuracy of PM measurements under in-use conditions and provide a basis for the development of the more comprehensive Measurement Allowance program. The MASC utilized the University of California, Riverside (UCR) Bourns College of Engineering – Center for Environmental Research and Technology’s (CE-CERT) Mobile Emissions Laboratory (MEL) to perform the initial in-use PM PEMS evaluation. For this program, PM PEMS were directly compared with the MEL over a series of different on-road driving conditions. Prior to the on-road testing, MEL underwent a 40CFR Part 1065 self-audit focused on PM sampling. In-use measurements were made from a class 8 truck whose in-use PM emissions levels averaged 0.043 g/hp-h, which is near the 0.03 g/hp-h in-use threshold level. The goal was to test a vehicle at or slightly above the Not-To-Exceed (NTE) threshold to investigate sources of error for the PM instruments at levels where their performance is most critical. The on-road driving courses included segments near sea level, in coastal regions, in desert regions, and on longer uphill inclines. PM measurements in real-time were made with a variety of different PM instruments from manufacturers preparing for the PM Measurement Allowance program, as well as other commercially available instruments such as a Dekati DMM and TSI Dustrak. These measurements were directly compared with gravimetric PM mass measurements that were collected with the MEL under 1065 compliant sampling conditions. Measurements were made under conditions where NTE events would be expected (e.g., uphill driving segments) and for varying durations to provide a range of mass loadings. Comparisons of the performance of the instruments and PM mass measurements from 0.02 to 0.1 g/hp-h are be presented. The results of this study are expected to be an important component of PM Measurement Allowance program development.