A combined model–observation approach to estimate historic gridded fields of PM2.5 mass and species concentrations

This paper introduces a methodology for estimating gridded fields of total and speciated fine particulate matter (PM_2.5) concentrations for time periods and regions not covered by observational data. The methodology is based on performing long-term regional scale meteorological and air quality simulations and then integrating these simulations with available observational data. To illustrate this methodology, we present an application in which year-round simulations with a meteorological model (the National Center for Atmospheric Research/Penn State Mesoscale Model, hereafter referred to as MM5) and a photochemical air quality model (the Community Multiscale Air Quality Model, hereafter referred to as CMAQ) have been performed over the northeastern United States for 1988–2005. Model evaluation results for total PM_2.5 mass and individual species for the time period from 2000 to 2005 show that model performance varies by species, season, and location. Therefore, an approach is developed to adjust CMAQ output with factors based on these three variables. The adjusted model values for total PM_2.5 mass for 2000–2005 are compared against independent measurements not utilized for the adjustment approach. This comparison reveals that the adjusted model values have a lower root mean square error (RMSE) and higher correlation coefficients than the original model values. Furthermore, the PM_2.5 estimates from these adjusted model values are compared against an alternate method for estimating historic PM_2.5 values that is based on PM_2.5/PM₁₀ ratios calculated at co-located monitors. Results reveal that both methods yield estimates of historic PM_2.5 mass that are broadly consistent; however, the adjusted CMAQ values provide greater spatial coverage and information for PM_2.5 species in addition to total PM_2.5 mass. Finally, strengths and limitations of the proposed approach are discussed in the context of potential uses of this method.     

Analysing and mapping spatial and temporal dynamics of urban traffic noise pollution: a case study in Kahramanmaraş, Turkey

This study aimed at quantifying noise pollution from urban traffic in the city of Kahramanmara?, Turkey. A total of 114 measurements for the equivalent noise level (L _Aeq) were made at 38 urban locations classified as “residential areas”, “residential and commercial areas” and “industrial areas” according to the national regulations, during morning, mid-day and evening hours. Our findings tabulated and mapped revealed that mean noise level in “residential and commercial areas” was highest relative to the other land-use types. Minimum and maximum values of noise pollution were recorded during the mid-day and evening hours, regardless of the land-use types. Noise limit values were exceeded at two locations only out of 38 based on the national regulation criteria and at over half of the locations based on the international criteria.     

Numerical Investigation of the Effects of Boundary-Layer Evolution on the Predictions of Ozone and the Efficacy of Emission Control Options in the Northeastern United States

This paper examines the effects of two different planetary boundary-layer (PBL) parameterization schemes – Blackadar and Gayno–Seaman – on the predicted ozone (O₃) concentration fields using the MM5 (Version 3.3) meteorological model and the MODELS-3 photochemical model. The meteorological fields obtained from the two boundary-layer schemes have been used to drive the photochemical model to simulate O₃ concentrations in the northeastern United States for a three-day O₃ episodic period. In addition to large differences in the predicted O₃ levels at individual grid cells, the simulated daily maximum 1-h O₃ concentrations appear at different regions of the modeling domain in these simulations, due to the differences in the vertical exchange formulations in these two PBL schemes. Using process analysis, we compared the differences between the different simulations in terms of the relative importance of chemical and physical processes to O₃ formation and destruction over the diurnal cycle. Finally, examination of the photochemical model's response to reductions in emissions reveals that the choice of equally valid boundary-layer parameterizations can significantly influence the efficacy of emission control strategies.     

Numerical Investigation of Boundary-Layer Evolution and Nocturnal Low-Level Jets: Local versus Non-Local PBL Schemes

Numerical simulations of the evolution of the planetary boundary layer (PBL) and nocturnal low-level jets (LLJ) have been carried out using MM5 (version 3.3) with four-dimensional data assimilation (FDDA) for a high pollution episode in the northeastern United States during July 15–20, 1999. In this paper, we assess the impact of different parameterizations on the PBL evolution with two schemes: the Blackadar PBL, a hybrid local (stable regime) and non-local (convective regime) mixing scheme; and the Gayno–Seaman PBL, a turbulent kinetic energy (TKE)-based eddy diffusion scheme. No FDDA was applied within the PBL to evaluate the ability of the two schemes to reproduce the PBL structure and its temporal variation. The restriction of the application of FDDA to the atmosphere above the PBL or the lowest 8 model levels, whichever is higher, has significantly improved the predicted strength and timing of the LLJ during the night. A systematic analysis of the PBL evolution has been performed for the primary meteorological fields (temperature, specific humidity, horizontal winds) and for the derived parameters such as the PBL height, virtual potential temperature, relative humidity, and cloud cover fraction. There are substantial differences between the PBL structures and evolutions simulated by these two different schemes. The model results were compared with independent observations (that were not used in FDDA) measured by aircraft, RASS and wind profiler, lidar, and tethered balloon platforms during the summer of 1999 as part of the NorthEast Oxidant and Particle Study (NE-OPS). The observations tend to support the non-local mixing mechanism better than the layer-to-layer eddy diffusion in the convective PBL.     

Decomposition of phorate in aqueous solution by ozonation

Phorate (O,O-diethyl S-ethylthiomethyl phosphorodithioate) dissolved in aqueous solution was almost completely decomposed by ozonation to form various species within 10 minutes of reaction time for the experimental conditions examined in this research. The generation rate of sulfate was found to be fairly independent of solution pH value. However, the formation of phosphate and carbonate was more favorable for alkaline solutions where hydroxyl free radical is the primary oxidative species. The reaction rates increased with initial gaseous ozone concentrations, indicating the reaction was mass transfer-controlled within the experimental range of this research. Combining the analytical results by various instruments, including gas chromatograph equipped with an electron ionization detector (GC-EID), high performance liquid chromatography (HPLC), ion chromatography (IC), and total organic carbon (TOC), the temporal sequence of phorate ozonation was proposed in this study. The oxidation of sulfur atoms on the phosphorus-sulfur double bond or carbon-sulfur-carbon bond by ozonation was found to occur at first to form sulfate and various intermediates.     

Photodecomposition of o-cresol by UV-LED/TiO2 process with controlled periodic illumination

This study investigated the effect of controlled periodic illumination on the photonic efficiency and temporal decomposition behavior of o-cresol by UV/TiO2 process in a slurry reactor using light emitting diodes as the light source. Based on the same UV light intensity of 6.7 W m(-2), the calculated photonic efficiencies increased from 1.5% to 6.3% with the decreasing duty cycle from 1.0 to 0.1 possibly ascribed to the decreasing electron-hole recombination. Actually, the calculated photonic efficiency under periodic illumination at sufficiently intermittence was inferior to, but approached, those under continuous illumination at equivalent average UV light intensity. The calculated electric energy per order increased from 32 to 37 k W h m(-3)order(-1) for experiments conducted with the increasing duty cycle from 0.1 to 1.0, and the electric energy consumption decreased significantly due to the lower duty cycle and average UV light intensity. The photocatalytic decomposition of o-cresol with the UV-light emitting diodes light could be well modeled by the Langmuir-Hinshelwood kinetic equation.     

Warning signals confer advantage to prey in competition with predators: bumblebees steal nests from insectivorous birds

Aposematic (warning) signals of prey help predators to recognize the defended distasteful or poisonous prey that should be avoided. The evolution of aposematism in the context of predation has been in the center of modern ecology for a long time. But, the possible roles of aposematic signals in other ecological contexts have been largely ignored. Here we address the role of aposematic signals in competition between prey and predators. Bumblebees use visual and auditory aposematic signals to warn predators about their defenses. For 2 years, we observed competition for nestboxes between chemically defended insects, Bombus ardens (and possibly also Bombus ignitus), and cavity nesting birds (Parus minor and Poecile varius). Bumblebees settled in 16 and 9 % of nestboxes (in 2010 and 2011 breeding seasons, respectively) that contained bird nests at the advanced stage of nest building or at the stage of egg laying. Presence of bumblebees prevented the birds from continuing the breeding activities in the nestboxes, while insects took over the birds’ nests (a form of kleptoparasitism). Playback experiments showed that the warning buzz by bumblebees contributed to the success in ousting the birds from their nests. This demonstrates that aposematic signals may be beneficial also in the context of resource competition.     

Terrestrial Biodiversity Analyses in Dalmatia (Croatia): A Complementary Approach Using Diversity and Rarity

Here we present the methodology used for terrestrial biodiversity analysis and site selection in Phase B of the UNDP/GEF COAST project. The analysis was focused on the problem of biodiversity evaluation in four Croatian counties stretching from sea level to the highest mountain in Croatia. Data on habitats, vascular flora, and fauna (mammals, birds, reptiles, amphibians, butterflies, ground beetles, and underground invertebrates) were collected and analyzed for each of the four counties. Emphasis was given to the richness of endangered species and the rarity of endemic species. Based on the spatial analyses of habitat, fauna, and flora data, four to six areas were selected from each county and ranked according to their biodiversity importance. Overlap between areas important for richness and those important for rarity was highest for data on flora (65.5%) and lowest for data on fauna (16.7%). When different data sets were compared, the lowest overlap was between flora and fauna (17.1%) and largest between fauna and habitats (23.9%). Simultaneous overlap among all three data sets was found in just 6.5% of the overall selected areas. These results suggest that less specific data, with respect to taxa threat status, could better serve as surrogate data in estimating overall biodiversity. In summary, this analysis has demonstrated that Dalmatia is a region with a high overall biodiversity that is important in a broader European context.     

Impact of biogenic emission uncertainties on the simulated response of ozone and fine particulate matter to anthropogenic emission reductions

The role of emissions of volatile organic compounds and nitric oxide from biogenic sources is becoming increasingly important in regulatory air quality modeling as levels of anthropogenic emissions continue to decrease and stricter health-based air quality standards are being adopted. However, considerable uncertainties still exist in the current estimation methodologies for biogenic emissions. The impact of these uncertainties on ozone and fine particulate matter (PM2.5) levels for the eastern United States was studied, focusing on biogenic emissions estimates from two commonly used biogenic emission models, the Model of Emissions of Gases and Aerosols from Nature (MEGAN) and the Biogenic Emissions Inventory System (BEIS). Photochemical grid modeling simulations were performed for two scenarios: one reflecting present day conditions and the other reflecting a hypothetical future year with reductions in emissions of anthropogenic oxides of nitrogen (NOx). For ozone, the use of MEGAN emissions resulted in a higher ozone response to hypothetical anthropogenic NOx emission reductions compared with BEIS. Applying the current U.S. Environmental Protection Agency guidance on regulatory air quality modeling in conjunction with typical maximum ozone concentrations, the differences in estimated future year ozone design values (DVF) stemming from differences in biogenic emissions estimates were on the order of 4 parts per billion (ppb), corresponding to approximately 5% of the daily maximum 8-hr ozone National Ambient Air Quality Standard (NAAQS) of 75 ppb. For PM2.5, the differences were 0.1-0.25 microg/m3 in the summer total organic mass component of DVFs, corresponding to approximately 1-2% of the value of the annual PM2.5 NAAQS of 15 microg/m3. Spatial variations in the ozone and PM2.5 differences also reveal that the impacts of different biogenic emission estimates on ozone and PM2.5 levels are dependent on ambient levels of anthropogenic emissions.     

The scale-free network behavior of ambient volatile organic compounds

A scale-free network model with surface and vertical field measurements was used to identify the connectivity distribution of the scale-free network behavior of ambient volatile organic compounds (VOCs). The results show that the carbon number (C _n ) with the total amount of C _n compounds (P(C _n )) possesses an explicit relationship with the scale-free network behavior. The proportionate coefficient (α) and exponent ( γ) of the scale-free network model with spatial and temporal variations are estimated and discussed. The analytical results demonstrate that although photochemical reactions cause the VOCs fraction variation, they do not alter the fraction of C _n compounds observably. Therefore, the values of α and of γ did not vary with time, but with local regional characteristics. The results indicate that the influence of local VOCs emissions occurs at a height of 100 m, but becomes insufficient at a height of 300 m. Air mass mixing increases with greater height; thus, the influence of regional characteristics at a height of 700 m is low. Finally, a successful empirical model was established to evaluate the distribution of surface VOCs in various regions.