Raghu Betha

2013 Southeast Asian Smoke Haze: Fractionation of Particulate-Bound Elements and Associated Health Risk

Recurring biomass burning-induced smoke haze is a serious regional air pollution problem in Southeast Asia (SEA). The June 2013 haze episode was one of the worst air pollution events in SEA. Size segregated particulate samples (2.5-1.0 μm; 1.0-0.5 μm; 0.5- 0.2 μm; and <0.2 μm) were collected during the June 2013 haze episode. PM2.5 concentrations were elevated (up to 329 μg/m(3)) during the haze episode, compared to those during the nonhaze period (11-21 μg/m(3)). Chemical fractionation of particulate-bound trace elements (B, Ca, K, Fe, Al, Ni, Zn, Mg, Se, Cu, Cr, As, Mn, Pb, Co, and Cd) was done using sequential extraction procedures. There was a 10-fold increase in the concentration of K, an inorganic tracer of biomass burning. A major fraction (>60%) of the elements was present in oxidizable and residual fractions while the bioavailable (exchangeable) fraction accounted for up to 20% for most of the elements except K and Mn. Deposition of inhaled potentially toxic trace elements in various regions of the human respiratory system was estimated using a Multiple-Path Particle Dosimetry model. The particle depositions in the respiratory system tend to be more severe during hazy days than those during nonhazy days. A prolonged exposure to finer particles can thus cause adverse health outcomes during hazy days. Health risk estimates revealed that the excessive lifetime carcinogenic risk to individuals exposed to biomass burning-impacted aerosols (18 ± 1 × 10(-6)) increased significantly (P < 0.05) compared to those who exposed to urban air (12 ± 2 × 10(-6)).

Emissions of particulate-bound elements from biodiesel and ultra low sulfur diesel: size distribution and risk assessment.

Use of waste cooking oil derived biodiesel (WCOB) as an alternative fuel in diesel engines has increased significantly in recent years. The impact of WCOB on particulate emissions from diesel engines needs to be investigated thoroughly. This study was conducted to make a comparative evaluation and size-differentiated speciation of the particulate bound elements from ultra low sulfur diesel (ULSD) and WCOB and a blend of both of the fuels (B50). Particle mass and their elemental size distributions ranging from 0.01-5.6 μm were measured. It was observed that more ultrafine particles (UFPs, <100 nm) were emitted when the engine was fueled with WCOB. Fifteen particulate-bound elements such as K, Al, Mg, Co, Cr, Cu, Fe, Mn, Cd, Ni, As, Ba, Pb, Zn and Sr were investigated and reported in this study. Potential health risk associated with these particulate bound elements upon inhalation was also evaluated based on dose-response assessments for both adults and children. The findings indicate that the exposure to PM of the B100 exhaust is relatively more hazardous and may pose adverse health effects compared to that of ULSD. Also, investigations on human health risk due to exposure to UFPs indicate that UFPs contribute a major fraction (>70%) of the total estimated health risk.

A study of diurnal variations of PM2.5 acidity and related chemical species using a new thermodynamic equilibrium model.

Aerosol acidity is one of the most important parameters that can influence atmospheric visibility, climate change and human health. Based on continuous field measurements of inorganic aerosol species and their thermodynamic modeling on a time resolution of 1h, this study has investigated the acidic properties of PM2.5 and their relation with the formation of secondary inorganic aerosols (SIA). The study was conducted by taking into account the prevailing ambient temperature (T) and relative humidity (RH) in a tropical urban atmosphere. The in-situ aerosol pH (pH(IS)) on a 12h basis ranged from -0.20 to 1.46 during daytime with an average value of 0.48 and 0.23 to 1.53 during nighttime with an average value of 0.72. These diurnal variations suggest that the daytime aerosol was more acidic than that caused by the nighttime aerosol. The hourly values of pH(IS) showed a reverse trend as compared to that of in-situ aerosol acidity ([H(+)]Ins). The pH(IS) had its maximum values at 3:00 and at 20:00 and its minimum during 11:00 to 12:00. Correlation analyses revealed that the molar concentration ratio of ammonium to sulfate (R(N/S)), equivalent concentration ratio of cations to anions (RC/A), T and RH can be used as independent variables for prediction of pH(IS). A multi-linear regression model consisting of RN/S, RC/A, T and RH was developed to estimate aerosol pH(IS).

Particulate Emissions from a Stationary Engine Fueled with Ultra-Low-Sulfur Diesel and Waste-Cooking-Oil-Derived Biodiesel

ABSTRACT Stationary diesel engines, especially diesel generators, are increasingly being used in both developing countries and developed countries because of increased power demand. Emissions from such engines can have adverse effects on the environment and public health. In this study, particulate emissions from a domestic stationary diesel generator running on ultra-low-sulfur diesel (ULSD) and biodiesel derived from waste cooking oil were characterized for different load conditions. Results indicated a reduction in particulate matter (PM) mass and number emissions while switching diesel to biodiesel. With increase in engine load, it was observed that particle mass increased, although total particle counts decreased for all the fuels. The reduction in total number concentration at higher loads was, however, dependent on percentage of biodiesel in the diesel-biodiesel blend. For pure biodiesel (B100), the reduction in PM emissions for full load compared to idle mode was around 9%, whereas for ULSD the reduction was 26%. A large fraction of ultrafine particles (UFPs) was found in the emissions from biodiesel compared to ULSD. Nearly 90% of total particle concentration in biodiesel emissions comprised ultrafine particles. Particle peak diameter shifted from a smaller to a lower diameter with increase in biodiesel percentage in the fuel mixture. IMPLICATIONS There has been an increased usage of stationary diesel engines, especially backup power generators to meet the growing energy demand. Biodiesel derived from waste cooking oil has received increasing attention as an alternative fuel. However, data are only sparsely available in the literature on particulate emissions from stationary engines, fueled with blends of diesel and biodiesel. This study provides insights into the influence of waste-cooking-oil-derived biodiesel on engine performance and the particulate emissions from a stationary engine. The results of the study form a scientific basis to evaluate the impact of biodiesel emissions on the environment and human health.

Emission characteristics of ultrafine particles and volatile organic compounds in a commercial printing center.

ABSTRACT Laser printers are one of the common indoor equipment in schools, offices, and various other places. Laser printers have recently been identified as a potential source of indoor air pollution. This study examines the characteristics of ultrafine particles (UFPs, diameter <100 nm) and volatile organic compounds (VOCs) emitted from laser printers housed in a commercial printing center. The results indicated that apart from the printer type, the age of printers, and the number of pages printed, the characteristics of UFPs emitted from printers also depend on indoor ventilation conditions. It was found that at reduced ventilation rates of indoor air, there was a rise in the number concentration of UFPs in the printing center. Interestingly, the contribution of UFPs to the total number of submicrometer-sized particles was observed to be higher at a sampling point far away from the printer than the one in the immediate vicinity of the printer. Black carbon (BC) measurements showed a good correlation (r S = 0.82) with particles in the size range of 100–560 nm than those with diameters less than 100 nm (r S = 0.33 for 50–100 nm, and r S = −0.19 for 5.6–50 nm particles). Measurements of VOCs in the printing center showed high levels of m-, o-, and p-xylene, styrene, and ethylbenzenes during peak hours of printing. Although toluene was found in higher levels, its concentration decreased during peak hours compared to those during nonoperating hours of the printing center. IMPLICATIONS This study reports the emission of ultrafine particles (UFPs) and volatile organic compounds (VOCs) from laser printers in a commercial printing center. It was found that the number concentration of UFPs released was not only influenced by the printer-related parameters, but also by indoor ventilation conditions. The fraction of UFPs was high at lower air change rate and at distances away from printers, presumably due to the formation of new particles. The results imply that laser printers equipped with particle traps and high ventilation rates in the commercial printing center are needed to reduce the exposure of occupants to UFPs and thus the associated health risk.

More unsaturated, cooking-type hydrocarbon-like organic aerosol particle emissions from renewable diesel compared to ultra low sulfur diesel in at-sea operations of a research vessel

ABSTRACT The aerosol particle emissions from R/V Robert Gordon Sproul were measured during two 5-day research cruises (29 September–3 October 2014; 4–7 and 26–28 September 2015) at four engine speeds (1600 rpm, 1300 rpm, 1000 rpm, and 700 rpm) to characterize the emissions under different engine conditions for ultra low sulfur diesel (ULSD) and hydrogenation derived renewable diesel (HDRD) fuels. Organic aerosol composition and mass distribution were measured on the aft deck of the vessel directly behind the exhaust stack to intercept the ship plume. The ship emissions for both fuels were composed of alkane-like compounds (H/C = 1.94 ± 0.003, O/C = 0.04 ± 0.001, CnH2n) with mass spectral fragmentation patterns consistent with hydrocarbon-like organic aerosol (HOA). Single-particle mass spectra from emissions for both fuels showed two distinct HOA compositions, with one HOA type containing more saturated alkane fragments (CnH2n+1) and the other HOA type containing more monounsaturated fragments (CnH2n−1). The particles dominated by the CnH2n−1 fragment series are similar to mass spectra previously associated with cooking emissions. More cooking-type organic particles were observed in the ship emissions for HDRD than for ULSD (45% and 38%, respectively). Changes in the plume aerosol composition due to photochemical aging in the atmosphere were also characterized. The higher fraction of alkene or aromatic (CnH2n−m, m ≥ 3) fragments in aged compared to fresh plume emissions suggest that some of the semivolatile alkane-like components partition back to the vapor phase as dilution increases, while alkene or aromatic hydrocarbons contribute more mass to the particle phase due to continuing photochemical oxidation and subsequent condensation from the vapor phase. Copyright

Hydroxyl radical formation and soluble trace metal content in particulate matter from renewable diesel and ultra low sulfur diesel in at-sea operations of a research vessel

ABSTRACT Reactive oxygen species, including hydroxyl radicals generated by particles, play a role in both aerosol aging and PM2.5 mediated health effects. We assess the impacts of switching marine vessels from conventional diesel to renewable fuel on the ability of particles to generate hydroxyl radical when extracted in a simulated lung lining fluid or in water at pH 3.5, for samples of engine emissions from a research vessel when operating on ultra-low sulfur diesel (ULSD) and hydrogenation-derived renewable diesel (HDRD). Samples were collected during dedicated cruises in 2014 and 2015, including aged samples collected by re-intercepting the ship plume. After normalizing to particle mass, particles generated from HDRD combustion had slightly to significantly (5–50%) higher OH generation activity than those from ULSD, a difference that was statistically significant for some permutations of year/fuel/engine speed. Water soluble trace metal concentrations and fuel metal concentrations were similar, and compared to urban Los Angeles samples lower in soluble iron and manganese, but similar for most other trace metals. Because PM mass emissions were higher for HDRD, normalizing to fuel increased this difference. Freshly emitted PM had lower activity than the “plume chase” samples, and samples collected on the ship had lower activity than the urban reference. The differences in OH production correlated reasonably well with redox-active transition metals, most strongly with soluble manganese, with roles for vanadium and likely copper and iron. The results also suggest that atmospheric processing of fresh combustion particles rapidly increases metal solubility, which in turn increases OH production. Copyright

Lower NOx but higher particle and black carbon emissions from renewable diesel compared to ultra low sulfur diesel in at-sea operations of a research vessel

ABSTRACT Gas and particle emissions from R/V Robert Gordon Sproul were measured for ultra low sulfur diesel (ULSD) and hydrogenation derived renewable diesel (HDRD) during dedicated aerosol measurement cruises in 2014 (29 September–3 October) and 2015 (4–7 and 26–28 September). CO, CO2, and NOX were measured directly from the starboard stack from the 2-stroke, small bore, high speed engine, while number and mass size distributions for both particles and black carbon (BC) were measured by intercepting the ship plume. Measurements at constant engine speeds (1600 rpm, 1300 rpm, 1000 rpm, and 700 rpm) had emission factors of CO () and NOX that were lower by 20% and 13%, respectively, for HDRD compared to ULSD at 700 rpm. However, at 1600 rpm, and were within one standard deviation for both ULSD (: 4.0 ± 0.1 g [kg-fuel]−1; : 51 ± 0.8 g [kg-fuel]−1) and HDRD (: 3.9 ± 0.2 g [kg-fuel]−1; : 51 ± 2 g [kg-fuel]−1). HDRD emission factors of particle number and mass concentrations were higher than ULSD by 46% to 107% and 36% to 150%, respectively, at 1600, 1300, and 1000 rpm, but the differences were smaller than the cycle-to-cycle variability at 700 rpm. BC mass emission factors were nearly 200% larger for 700, 1000, and 1300 rpm for HDRD compared to ULSD, but the mass differences were smaller than cycle-to-cycle variability at 1600 rpm. BC mass size distributions showed that the peak diameter of the BC mass mode for ULSD (∼120 nm) is about 20 nm larger than for HDRD (∼100 nm), even though the particle mass and number size distributions are quite similar. Copyright

Physico-Chemical Characteristics of Particulate Emissions from Diesel Engines Fuelled with Waste Cooking Oil Derived Biodiesel and Ultra Low Sulphur Diesel

A ground breaking invention in 1893 by Rudolf Diesel (Diesel Engine – named after him) made a mark in the world of internal combustion engines; his engine was the first one to prove that fuel could be ignited without a spark. Since this invention, diesel engines have been widely used in various applications such as automobiles, agriculture, ships, electricity generators, construction equipment etc., all over the world. Diesel engines were proved to be very efficient in terms of delivering the required energy levels for their use at very low operating and maintenance costs when compared to gasoline engines. However, diesel en‐ gines now pose a serious threat to human health and adversely impact the urban air quality (Sydbom et al., 2001). Diesel engine exhaust contains a host of harmful substances including airborne particulate matter (PM), carbon soot, toxic metals, polycyclic aromatic hydrocar‐ bons (PAHs), nitrogen oxides which induce ozone formation, carbon monoxide, carbon di‐ oxide, volatile organic compounds and other compounds such as formaldehyde and acrolein (EPA, 2002). Of these pollutants, PM from diesel exhaust is of great concern because of a number of reasons: (1) Diesel engines are known to be the largest source of PM from motor vehicles. Two thirds of PM emitted from mobile sources are from diesel vehicles (EPA, 2002); (2) Human exposure to diesel exhaust particles (DEP) is high as these particles are emitted at ground level unlike that of smoke stacks. United Stated of Environmental Pro‐ tection Agency (USEPA) reported that 83% of people living in the USA are exposed to con‐ centrated diesel emissions from sources such as highways, heavy industries, construction

Substantial Seasonal Contribution of Observed Biogenic Sulfate Particles to Cloud Condensation Nuclei

Biogenic sources contribute to cloud condensation nuclei (CCN) in the clean marine atmosphere, but few measurements exist to constrain climate model simulations of their importance. The chemical composition of individual atmospheric aerosol particles showed two types of sulfate-containing particles in clean marine air masses in addition to mass-based Estimated Salt particles. Both types of sulfate particles lack combustion tracers and correlate, for some conditions, to atmospheric or seawater dimethyl sulfide (DMS) concentrations, which means their source was largely biogenic. The first type is identified as New Sulfate because their large sulfate mass fraction (63% sulfate) and association with entrainment conditions means they could have formed by nucleation in the free troposphere. The second type is Added Sulfate particles (38% sulfate), because they are preexisting particles onto which additional sulfate condensed. New Sulfate particles accounted for 31% (7 cm−3) and 33% (36 cm−3) CCN at 0.1% supersaturation in late-autumn and late-spring, respectively, whereas sea spray provided 55% (13 cm−3) in late-autumn but only 4% (4 cm−3) in late-spring. Our results show a clear seasonal difference in the marine CCN budget, which illustrates how important phytoplankton-produced DMS emissions are for CCN in the North Atlantic.