Guidance for the Performance Evaluation of Three-Dimensional Air Quality Modeling Systems for Particulate Matter and Visibility

ABSTRACT

Guidance for the performance evaluation of three-dimensional air quality modeling systems for particulate matter and visibility is presented. Four levels are considered: operational, diagnostic, mechanistic, and probabilistic evaluations. First, a comprehensive model evaluation should be conducted in at least two distinct geographical locations and for several meteorological episodes. Next, streamlined evaluations can be conducted for other similar applications if the comprehensive evaluation is deemed satisfactory. In all cases, the operational evaluation alone is insufficient, and some diagnostic evaluation must always be carried out. Recommendations are provided for designing field measurement programs that can provide the data needed for such model performance evaluations.     

Modeling of Potential Power Plant Plume Impacts on Dallas-Fort Worth Visibility

ABSTRACT

During wintertime, haze episodes occur in the Dallas-Ft. Worth (DFW) urban area. Such episodes are characterized by substantial light scattering by particles and relatively low absorption, leading to so-called “white haze.” The objective of this work was to assess whether reductions in the emissions of SO₂ from specific coal-fired power plants located over 100 km from DFW could lead to a discernible change in the DFW white haze. To that end, the transport, dispersion, deposition, and chemistry of the plume of a major power plant were simulated using a reactive plume model (ROME). The realism of the plume model simulations was tested by comparing model calculations of plume concentrations with aircraft data of SF₆ tracer concentrations and ozone concentrations. A second-order closure dispersion algorithm was shown to perform better than a first-order closure algorithm and the empirical Pasquill-Gifford-Turner algorithm. For plume impact assessment, three actual scenarios were simulated, two with clear-sky conditions and one with the presence of fog prior to the haze. The largest amount of sulfate formation was obtained for the fog episode. Therefore, a hypothetical scenario was constructed using the meteorological conditions of the fog episode with input data values adjusted to be more conducive to sulfate formation. The results of the simulations suggest that reductions in the power plant emissions lead to less than proportional reductions in sulfate concentrations in DFW for the fog scenario. Calculations of the associated effects on light scattering using Mie theory suggest that reduction in total (plume + ambient) light extinction of less than 13% would be obtained with a 44% reduction in emissions of SO₂ from the modeled power plant.     

Occupant responses in conventional and ABTS seats in high-speed rear sled tests

Objective: This study compared biomechanical responses of a normally seated Hybrid III dummy on conventional and all belts to seat (ABTS) seats in 40.2 km/h (25 mph) rear sled tests. It determined the difference in performance with modern (≥2000 MY) seats compared to older (<2000 MY) seats and ABTS seats.

Methods: The seats were fixed in a sled buck subjected to a 40.2 km/h (25 mph) rear sled test. The pulse was a 15 g double-peak acceleration with 150 ms duration. The 50th percentile Hybrid III was lap–shoulder belted in the FMVSS 208 design position. The testing included 11 <2000 MY, 8 ≥2000 MY, and 7 ABTS seats. The dummy was fully instrumented, including head accelerations, upper and lower neck 6-axis load cells, chest acceleration, thoracic and lumbar spine load cells, and pelvis accelerations. The peak responses were normalized by injury assessment reference values (IARVs) to assess injury risks. Statistical analysis was conducted using Student's t test. High-speed video documented occupant kinematics.

Results: Biomechanical responses were lower with modern (≥2000 MY) seats than older (<2000 MY) designs. The lower neck extension moment was 32.5 ± 9.7% of IARV in modern seats compared to 62.8 ± 31.6% in older seats (P =.01). Overall, there was a 34% reduction in the comparable biomechanical responses with modern seats. Biomechanical responses were lower with modern seats than ABTS seats. The lower neck extension moment was 41.4 ± 7.8% with all MY ABTS seats compared to 32.5 ± 9.7% in modern seats (P =.07). Overall, the ABTS seats had 13% higher biomechanical responses than the modern seats.

Conclusions: Modern (≥2000 MY) design seats have lower biomechanical responses in 40.2 km/h rear sled tests than older (<2000 MY) designs and ABTS designs. The improved performance is consistent with an increase in seat strength combined with improved occupant kinematics through pocketing of the occupant into the seatback, higher and more forward head restraint, and other design changes. The methods and data presented here provide a basis for standardized testing of seats. However, a complete understanding of seat safety requires consideration of out-of-position (OOP) occupants in high-speed impacts and consideration of the much more common, low-speed rear impacts.     

Challenges of soil mixing using catalyzed hydrogen peroxide with rotating dual axis blending technology

Although known to be one of the most effective oxidants for treatment of organic contaminants, catalyzed hydrogen peroxide (CHP) is typically not used for soil mixing applications because of health and safety concerns related to vapor generation and very rapid rates of reaction in open excavations. In likely the first large‐scale in situ CHP soil mixing application, an enhanced CHP, modified Fenton's reagent (MFR), was applied during soil mixing at the Kearsarge Metallurgical Superfund Site in New Hampshire. An innovative rotating dual‐axis blender (DAB) technology was used to safely mix the MFR into low‐plasticity silt and clay soils to remediate residual 1,1,1‐trichloroethane (111TCA); 1,1‐dichloroethene (11DCE); and 1,4‐dioxane (14D). It was expected that the aggressive treatment approach using relatively “greener” hydrogen peroxide (HP) chemistry would effectively treat Site contaminants without significant byproduct impacts to groundwater or the adjacent pond. The remediation program was designed to treat approximately 3,000 cubic yards of residual source area soil in situ by aggressively mixing MFR into the soils. The subsurface interval treated was from 7 to 15 feet below ground surface. To accurately track the soil mixing process and MFR addition, the Site was divided into 109 10‐foot square treatment cells that were precisely located, dosed, and mixed using the DAB equipped with an on‐board GPS system. The use of stabilizing agents along with careful calculation of the peroxide dose helped to ensure vapor‐free conditions in the vicinity of the soil mixing operation. Real‐time sampling and monitoring were critical in identifying any posttreatment exceedences of the cleanup goals. This allowed retreatment and supplemental testing to occur without impacting the soil mixing/in situ chemical oxidation (ISCO) schedule. Posttreatment 24‐hr soil samples were collected from 56 random locations after ensuring that the HP had been completely consumed. The posttreatment test results showed that 111TCA and 11DCE concentrations were reduced to nondetect (ND) or below the cleanup goals of 150 μg/kg for 111TCA and 60 μg/kg for 11DCE. Supplemental posttreatment soil samples, collected six months after treatment, showed 100 percent compliance with the soil treatment goals. Groundwater samples collected one year after the MFR soil mixing treatment program showed either ND or low concentrations for 111TCA, 11DCE, and 14D. Successful stabilization and site restoration was performed after overcoming considerable challenges associated with loss of soil structure, high liquid content, and reduced bearing capacity of the blended soils.     

Changes in structural attributes of plant communities along disturbance gradients in a dry deciduous forest of Western Ghats, India

Changes in tree and understory plant diversity and community composition in two sites at different disturbance levels were studied on the Anaikatty hills, Western Ghats. Systematic sampling using small scale permanent quadrates (50 x 20 m for trees, 5 x 5 m for shrubs/saplings, 1 x 1 m for herbs/seedlings) enumerated 3,376 individuals of trees (106 species), 8,599 of individuals shrubs (122 species) and 16,659 individuals of herbs (145 species). Among the two sites, species richness and diversity were highest for low disturbed stand (98 and 3.9, respectively) compared to high disturbed site (45 and 2.71, respectively). Result of cluster analysis showed that two distinct clusters were formed on the basis of disturbance of the area in concordance with our field observation. A total of 37 species were common to both sites, sixty one species exclusively found in low disturbed site and eight species were pertained to highly disturbed site. Mann-Whitney test based on Monte Carlo approximation at 95% confidence levels indicated that both populations were not entirely different. The clear difference was only observed for average basal area of trees, density of seedlings, number of species, density and diversity for shrubs and number of species and diversity for herb. The species composition were different in two stand i.e., Nothopegia racemosa-Albizia amara-Maba neilghrrensis in low disturbed stand and Albizia amara-Pleiospermium alatum-Bauhinia racemosa in high disturbed stand. The major disturbance factors identification using spearman rank correlation indicated that the disturbance in low disturbed habitats were mostly from past logging followed by cutting and illicit felling and grazing, while in high disturbed habitats, it was human presence, past logging and lopping and fuel wood collection.     

Assessment of organochlorine pesticide residues in Indian flue-cured tobacco with gas chromatography-single quadrupole mass spectrometer

Presence of pesticide residues in tobacco increases health risk of both active and passive smokers, apart from the imminent potential health problems associated with it. Thus, monitoring of pesticide residue is an important issue in terms of formulating stringent policies, enabling global trade and safeguarding the consumer’s safety. In this study, a gas chromatography-single quadrupole mass spectrometry (GC-MS) method based upon quantifier-qualifier ions (m/z) ratio was employed for detecting and assessing ten organochlorine pesticide residues (α-HCH, β-HCH, γ-HCH, δ-HCH, 2,4-DDT, 4,4-DDT, endrin, α-endosulfan, β-endosulfan and endosulfan sulphate) in 152 flue-cured (FC) tobacco leave samples from two major tobacco growing states, Karnataka and Andhra Pradesh, of India. In the majority of samples, pesticide residue levels were below the limit of quantification (LOQ). In few samples, pesticide residues were detected and they found to comply with the guidance residue levels (GRL) specifications of the Cooperation Center for Scientific Research Relative to Tobacco (CORESTA). Detection of the phase out pesticides like DDT/HCH might be due to transfer of persistent residues from the environmental components to the plant. This is the first report on these ten organochlorine pesticide residues in Indian FC tobacco.     

Physiological responses,tolerance, and remediation strategies in plants exposed to metalloids

Environmental Science and Pollution Research - Metalloids are a subset of particular concern to risk assessors and toxicologists because of their well-documented potential hazards to plant system....     

Correction to: Assessment of bioavailable nitrogen and phosphorus content in the sediments of Indian mangroves

Environmental Science and Pollution Research - A Correction to this paper has been published: https://doi.org/10.1007/s11356-021-14155-3