Critical review of the building downwash algorithms in AERMOD

The only documentation on the building downwash algorithm in AERMOD (American Meteorological Society/U.S. Environmental Protection Agency Regulatory Model), referred to as PRIME (Plume Rise Model Enhancements), is found in the 2000 A&WMA journal article by Schulman, Strimaitis and Scire. Recent field and wind tunnel studies have shown that AERMOD can overpredict concentrations by factors of 2 to 8 for certain building configurations. While a wind tunnel equivalent building dimension study (EBD) can be conducted to approximately correct the overprediction bias, past field and wind tunnel studies indicate that there are notable flaws in the PRIME building downwash theory. A detailed review of the theory supported by CFD (Computational Fluid Dynamics) and wind tunnel simulations of flow over simple rectangular buildings revealed the following serious theoretical flaws: enhanced turbulence in the building wake starting at the wrong longitudinal location; constant enhanced turbulence extending up to the wake height; constant initial enhanced turbulence in the building wake (does not vary with roughness or stability); discontinuities in the streamline calculations; and no method to account for streamlined or porous structures.

Implications: This paper documents theoretical and other problems in PRIME along with CFD simulations and wind tunnel observations that support these findings. Although AERMOD/PRIME may provide accurate and unbiased estimates (within a factor of 2) for some building configurations, a major review and update is needed so that accurate estimates can be obtained for other building configurations where significant overpredictions or underpredictions are common due to downwash effects. This will ensure that regulatory evaluations subject to dispersion modeling requirements can be based on an accurate model. Thus, it is imperative that the downwash theory in PRIME is corrected to improve model performance and ensure that the model better represents reality.     

Value chain for next-generation biofuels: resilience and sustainability of the product life cycle

Multiple factors including climate change, price uncertainties, and geopolitical instability have prompted many industries to investigate the feasibility of replacing traditional petroleum-based fuels with biofuel alternatives. However, to make this transition successful, these new biofuels must be environmentally sustainable and the necessary support infrastructure must be in place to make the production, distribution, and storage of these biofuels technologically feasible and cost effective. Developing a value chain, spanning from feedstock production to distribution to end users, requires garnering buy-in from multiple stakeholders by demonstrating environmental, economic, and social benefits and incentives. Two critical factors are the environmental benefits achieved from the use of the biofuel technology and the degree of resilience of the value chain to emergent conditions to ensure steady supply to consumers. Moreover, different biofuel pathways have different costs, benefits, and risks which must be compared. In this paper, we describe how environmental sustainability can be modeled using life cycle assessment (LCA) and how the resilience of value chain initiatives can be modeled using a scenario-based decision model. We then describe how sustainability and resilience assessments can be integrated in an iterative, anticipatory LCA framework. These assessments can be used as the basis for a business case for various investments, as well as a means for promoting responsible innovations, with the aviation industry used as a case study.     

Public participation in municipal solid waste source-separated collection in Guilin,China: status and influencing factors

Currently, China is facing critical problems regarding the management of municipal solid waste (MSW). The failure of existing pilot programs in implementing MSW source-separated collection highlights the need to analyze the factors significantly influencing public participation in this activity. To this end, a comprehensive analysis of MSW source-separated collection in Guilin, which is representative of wider areas located in inland China and with a GDP around the national average, was conducted. The research consisted of in-person interviews involving a questionnaire and theoretical analyses in terms of public perception, public awareness, public attitude, and willingness to pay. The analytical results identify the status of waste source-separated collection and influencing factors in implementation, and provides exercisable suggestions for decision makers in both China and more generally in industrializing countries to design promotion programs and education campaigns.     

Mass transfer coefficients for volatilization of polychlorinated biphenyls from the Hudson River,New York measured using micrometeorological approaches

Air–water exchange is an important process controlling the fate of many organic chemicals in the environment. Modeling this process is hampered by the lack of direct observations. Thus, the purpose of this work was to derive direct measurements of the mass transfer coefficients for air–water exchange (v_aw) of polychlorinated biphenyls (PCBs) that may be used to check the validity of values derived from tracer gas experiments. v_aw values for PCBs were determined using previously published turbulent fluxes divided by the corresponding dissolved phase concentrations. The median v_aw values for each homolog decreased with increasing molecular weight and ranged from 0.29 for hexachlorobiphenyls to 2.2 m d^?1 for monochlorobiphenyls with a propagated uncertainty of about 70%, lower than in previous studies. Due to relatively low wind speeds and possible sorption of PCBs to colloids, these numbers may be biased low. These field measurements of v_aw differ by as much as a factor of 23 from predictions based on the widely-used Whitman two-film model. Therefore a new formulation for the calculation of v_aw based on field measurements is needed. This study demonstrates that micrometeorological approaches are a viable option for the measurement of v_aw for hydrophobic organics such as PCBs and should be used to generate enough field data on the air–water exchange of hydrophobic organics to allow the development of new predictive models.     

Earthworm ecotoxicological assessments of pesticides used to treat seeds under tropical conditions

Ecotoxicological laboratory tests (lower-tier tests) are fundamental tools for assessing the toxicity of pesticides to soil organisms. In this study, using these tests under tropical conditions, we quantified the impact of the insecticides imidacloprid, fipronil, and thiametoxam, and the fungicides captan and carboxin + thiram, all of which are used in the chemical treatment of crop seeds, on the survival, reproduction, and behavior of Eisenia andrei (Oligochaeta). With the exception of imidacloprid, none of the pesticides tested caused mortality in E. andrei in artificial soils. The LC₅₀ of imidacloprid was estimated as 25.53 mg active ingredient kg^?1 of dry soil. Earthworm reproduction rates were reduced by imidacloprid (EC₅₀ = 4.07 mg kg^?1), fipronil (EC₂₀ = 23.16 mg kg^?1), carboxin + thiram (EC₅₀ = 56.38 mg kg^?1), captan (EC₅₀ = 334.84 mg kg^?1), and thiametoxam (EC₅₀ = 791.99 mg kg^?1). Avoidance behavior was observed in the presence of imidacloprid (AC₅₀ = 0.11 mg kg^?1), captan (AC₅₀ = 33.54 mg kg^?1), carboxin + thiram (AC₅₀ = 60.32 mg kg^?1), and thiametoxam (AC₅₀ = >20 mg kg^?1). Earthworms showed a preference for soils with the insecticide fipronil. Imidacloprid was the most toxic of the substances tested for E. andrei. The avoidance test was the most sensitive test for most pesticides studied, but results varied between pesticides. These results offer new insights on the toxicity of pesticides used to treat seeds in tropical regions. However, they should be complemented with higher-tier tests in order to reduce the uncertainties in risk assessment.     

Removal of sulfamethoxazole and sulfapyridine by carbon nanotubes in fixed-bed columns

Sulfamethoxazole (SMX) and sulfapyridine (SPY), two representative sulfonamide antibiotics, have gained increasing attention because of the ecological risks these substances pose to plants, animals, and humans. This work systematically investigated the removal of SMX and SPY by carbon nanotubes (CNTs) in fixed-bed columns under a broad range of conditions including: CNT incorporation method, solution pH, bed depth, adsorbent dosage, adsorbate initial concentration, and flow rate. Fixed-bed experiments showed that pH is a key factor that affects the adsorption capacity of antibiotics to CNTs. The Bed Depth Service Time model describes well the relationship between service time and bed depth and can be used to design appropriate column parameters. During fixed-bed regeneration, small amounts of SMX (3%) and SPY (9%) were irreversibly bonded to the CNT/sand porous media, thus reducing the column capacity for subsequent reuse from 67.9 to 50.4 mg g^?1 for SMX and from 91.9 to 72.9 mg g^?1 for SPY. The reduced column capacity resulted from the decrease in available adsorption sites and resulting repulsion (i.e., blocking) of incoming antibiotics from those previously adsorbed. Findings from this study demonstrate that fixed-bed columns packed with CNTs can be efficiently used and regenerated to remove antibiotics from water.     

Comparative acute toxicity of two phytosanitary molecules,lambda-cyhalothrin and acetamiprid,on Nile Tilapia (Oreochromis Niloticus) juveniles

Abstract

This study aimed to compare the toxicity for fish of two active ingredients (lambda-cyhalothrin-20?g L^?1, a pyrethroid, and acetamiprid-15?g L^?1, a neonicotinoid) which are components of a commercial insecticide (Acer 35 EC) used in cotton crop in many West African countries. The juveniles of Oreochromis niloticus (4.01?±?0.34?g, mean body weight) were exposed for 96?h to increasing concentrations of active ingredients (lambda-cyhalothrin and acetamiprid) or a mixture similar to Acer 35 EC (composed by 20?g of chemical compound lambda-cyhalothrin and 15?g of acetamiprid dissolved in 1?L of acetone). The experiments were carried out under controlled conditions in aquaria according to OECD Guidelines. During the experiments, the behavioral responses (loss of balance, color change, hyperactivity, etc.) that usually precede death were observed in exposed fish. Mortalities were recorded in each aquarium and the LC₅₀-96h of each chemical was determined. The LC₅₀-96h obtained were respectively 0.1268, 0.0029, 182.9 and 0.5685?ppm for Acer 35 EC, lambda-cyhalothrin, acetamiprid and mixture. All insecticides used in this study had profound impact on Nile tilapia behavior which may confirm the neurotoxicity of each single active compound as well as of their mixture.     

Glutamine synthetase and protease enzyme activities and growth response of ruminal bacterium Prevotella ruminicola strain B14 to nitrogen source and concentration

Abstract

The objective of this study was to determine the effects of varying nitrogen sources and concentrations upon glutamine synthetase and protease activities in Prevotella ruminicola strain B₁4. Based on growth response it appears that ammonium chloride or pepticase limited P. ruminicola becomes nitrogen limited when nitrogen concentration is at 0.5 mM. However, when casein was provided as the sole source of nitrogen P. ruminicola becomes nitrogen limited at 2.5 mM. Glutamine synthetase activity was measured from mid‐log phase cells grown in either nitrogen‐limited or non‐limited conditions. No activity was detectable in the non‐limited treatments. However, in the N‐ limited treatments, pepticase had the highest activity (20.76 units), followed by ammonium chloride (18.72 units) and casein (14.42 units). Protease activity assays indicated that nitrogen‐limited cultures had higher proteolytic activity than non‐limited cultures. Moreover, these activities appeared to follow the same response pattern as the previously observed glutamine synthetase activities. The results of this study indicate that P. ruminicola strain B, 4 protease activity may be influenced by nitrogen concentration such that activity increases when nitrogen availability decreases.     

Impact of long‐term pesticide applications on some soil biological parameters

Abstract

The soil oxidative and anaerobic processes, as well as, the microbial biomass were followed during three years in a cotton farm (Tatuí) where the recommended pesticides have been used for several years, and in an experimental field (São Paulo) treated first time with the same pesticides. The oxidative process was monitored by the dehydrogenase (DHA)‐activity using triphenyltetrazolium chloride (TTC) as substrate. The anaerobic process was followed by the iron‐oxide reduction, and the microbial biomass was estimated by the substrate (glucose)‐indiced respiration. Increases in DHA‐activity and in the microbial biomass occurred only in the farm soil, with concomitant decreases in iron‐reduction. In the experimental field soil, the increases in DHA‐activity were followed only by decreases in iron‐reduction. Soil characteristics were the determining factor for different biological parameters after pesticide inputs. All the pesticides produced at least one clear but transient effect.