Evaluation of low wind modeling approaches for two tall-stack databases

The performance of the AERMOD air dispersion model under low wind speed conditions, especially for applications with only one level of meteorological data and no direct turbulence measurements or vertical temperature gradient observations, is the focus of this study. The analysis documented in this paper addresses evaluations for low wind conditions involving tall stack releases for which multiple years of concurrent emissions, meteorological data, and monitoring data are available. AERMOD was tested on two field-study databases involving several SO₂ monitors and hourly emissions data that had sub-hourly meteorological data (e.g., 10-min averages) available using several technical options: default mode, with various low wind speed beta options, and using the available sub-hourly meteorological data. These field study databases included (1) Mercer County, a North Dakota database featuring five SO₂ monitors within 10 km of the Dakota Gasification Company’s plant and the Antelope Valley Station power plant in an area of both flat and elevated terrain, and (2) a flat-terrain setting database with four SO₂ monitors within 6 km of the Gibson Generating Station in southwest Indiana. Both sites featured regionally representative 10-m meteorological databases, with no significant terrain obstacles between the meteorological site and the emission sources. The low wind beta options show improvement in model performance helping to reduce some of the overprediction biases currently present in AERMOD when run with regulatory default options. The overall findings with the low wind speed testing on these tall stack field-study databases indicate that AERMOD low wind speed options have a minor effect for flat terrain locations, but can have a significant effect for elevated terrain locations. The performance of AERMOD using low wind speed options leads to improved consistency of meteorological conditions associated with the highest observed and predicted concentration events. The available sub-hourly modeling results using the Sub-Hourly AERMOD Run Procedure (SHARP) are relatively unbiased and show that this alternative approach should be seriously considered to address situations dominated by low-wind meander conditions.

Implications: AERMOD was evaluated with two tall stack databases (in North Dakota and Indiana) in areas of both flat and elevated terrain. AERMOD cases included the regulatory default mode, low wind speed beta options, and use of the Sub-Hourly AERMOD Run Procedure (SHARP). The low wind beta options show improvement in model performance (especially in higher terrain areas), helping to reduce some of the overprediction biases currently present in regulatory default AERMOD. The SHARP results are relatively unbiased and show that this approach should be seriously considered to address situations dominated by low-wind meander conditions.     

Laboratory Characterization of Modified Tapered Element Oscillating Microbalance Samplers

Abstract

Laboratory tests with generated aerosols were conducted to test the efficacy of two recent design modifications to the well-established tapered element oscillating microbalance (TEOM) continuous particulate matter (PM) mass monitor. The two systems tested were the sample equilibration system-equipped TEOM monitor operating at 30 °C, which uses a Nafion dryer as part of the sample inlet, and the differential TEOM monitor, which adds a switched electrostatic precipitator and uses a self-referencing algorithm to determine “true PM mass.” Test aerosols included ammonium sulfate, ammonium nitrate, sodium chloride, copper (II) sulfate, and mixed aerosols. Aerosols were generated with an atomizer or a vibrating orifice generator and were equilibrated in a 450-L slow flow chamber before being sampled. Relative humidity in the chamber was varied between 10 and 90%, and step changes in humidity were executed while generating aerosol to test the response of the instruments. The sample equilibration system-equipped TEOM monitor does reduce, but not totally eliminate, the sensitivity of the TEOM mass monitor to changes in humidity. The differential TEOM monitor gives every indication of being a very robust technique for the continuous real-time measurement of ambient aerosol mass, even in the presence of semi-volatile particles and condensable gases.     

Short and medium chain length chlorinated paraffins in UK human milk fat

Chlorinated paraffins (also called polychlorinated n-alkanes -- PCAs) are a class of industrial chemicals comprising chlorinated straight chain hydrocarbons. They have a wide range of applications and are now found in a range of environmental compartments. We analysed a total of 25 human milk-fat samples, donated by 18 individuals from the urban London and more rural Lancaster areas in the UK, for short chain PCAs (C(10)-C(13) sPCAs) and medium chain PCAs (C(14)-C(17) mPCAs), using gas chromatography-ECNI high-resolution mass spectrometry. Our study confirms that trace quantities of PCAs can reach human milk-fat. sPCAs were detected in all but four samples, while mPCAs were detected in all samples. The median sPCA concentration was 180 ng/g fat (range of 49 to 820 ng/g fat -- detected values only) and the median mPCA concentration was 21 ng/g fat (range of 6.2 to 320 ng/g fat). No differences were noted in ranges of observed values for either sPCAs or mPCAs between samples from London and Lancaster. Most samples also exhibited similar patterns of sPCAs and mPCAs. One sample exhibited a different pattern for sPCAs and mPCAs, an observation that may be related to differences in exposure or biological factors for this individual.     

Passive acoustic monitoring of the decline of Mexico's critically endangered vaquita

The vaquita (Phocoena sinus) is the world's most endangered marine mammal with approximately 245 individuals remaining in 2008. This species of porpoise is endemic to the northern Gulf of California, Mexico, and historically the population has declined because of unsustainable bycatch in gillnets. An illegal gillnet fishery for an endangered fish, the totoaba (Totoaba macdonaldi), has recently resurged throughout the vaquita's range. The secretive but lucrative wildlife trade with China for totoaba swim bladders has probably increased vaquita bycatch mortality by an unknown amount. Precise population monitoring by visual surveys is difficult because vaquitas are inherently hard to see and have now become so rare that sighting rates are very low. However, their echolocation clicks can be identified readily on specialized acoustic detectors. Acoustic detections on an array of 46 moored detectors indicated vaquita acoustic activity declined by 80% between 2011 and 2015 in the central part of the species’ range. Statistical models estimated an annual rate of decline of 34% (95% Bayesian credible interval –48% to –21%). Based on results from 2011 to 2014, the government of Mexico enacted and is enforcing an emergency 2‐year ban on gillnets throughout the species’ range to prevent extinction, at a cost of US$74 million to compensate fishers. Developing precise acoustic monitoring methods proved critical to exposing the severity of vaquitas’ decline and emphasizes the need for continual monitoring to effectively manage critically endangered species.     

Increase in remediation processes of oil‐contaminated soils

A study was conducted in the region of the Lena River, in northeast Russia, where oil‐contaminated soil remediation is compromised due to the reduced natural attenuation mechanisms in northern eco‐systems. The goal of the study was to analyze the effectiveness of different biological methods for remediating the permafrost soil cover contaminated with high concentrations of oil. For the remediation of the areas with approximately similar levels of contamination (in the range of 10 to 14 grams per kilogram [g/kg] of soil) different biological remediation schemes were applied: site 1: sowing plant seeds of meadow clover grass; site 2: introducing a consortium of hydrocarbon oxidizing microorganisms (HOM); and, site 3: introducing the same consortium of HOM with simultaneously sowing grass mixture. The third scheme, applied for the first time, led to the most favorable results, which might be explained by the synergistic effect based on the principle of positive inverse development.     

Selective separation of virgin and post-consumer polymers (PET and PVC) by flotation method

More and more polymer wastes are generated by industry and householders today. Recycling is an important process to reduce the amount of waste resulting from human activities. Currently, recycling technologies use relatively homogeneous polymers because hand-sorting waste is costly. Many promising technologies are being investigated for separating mixed thermoplastics, but they are still uneconomical and unreliable. At present, most waste polymers cause serious environmental problems. Burning polymers for recycling is not practiced since poisonous gases are released during the burning process. Particularly, polyvinyl chloride (PVC) materials among waste polymers generate hazardous HCl gas, dioxins containing Cl, etc., which lead to air pollution and shorten the life of the incinerator. In addition, they make other polymers difficult to recycle.Both polyethylene terephthalate (PET) and PVC have densities of 1.30–1.35 g/cm³ and cannot be separated using conventional gravity separation techniques. For this reason, polymer recycling needs new techniques. Among these techniques, froth flotation, which is also used in mineral processing, can be useful because of its low cost and simplicity.The main objective of this research is to recycle PET and PVC selectively from post-consumer polymer wastes and virgin polymers by using froth flotation. According to the results, all PVC particles were floated with 98.8% efficiency in virgin polymer separation while PET particles were obtained with 99.7% purity and 57.0% efficiency in post-consumer polymer separation.     

Photobiological production of hydrogen by the waste water treatment with anaerobic photosynthetic Purple bacteria

In this paper selected references about experience gained with photosynthetic bacteria in anaerobic process for either water treatment or hydrogen production are given. In particular experimental data about the hydrogen evolution rate, hydrogen yield and substrate efficiency in relationship to the nutrient conditions as well as about the behavior of some different species are presented. The limiting role of the nitrogen source is being discussed.     

Treatment of cork boiling wastewater using chemical oxidation and biodegradation

Three cultures were enriched from cork boiling wastewater using tannic acid as the selective carbon substrate, at 25 degrees C and pH 7.2, 25 degrees C and pH 4.7 and 50 degrees C and pH 4.7. The enrichment culture obtained at neutral pH was composed of five culturable isolates, whereas from each acidic enrichment two bacterial strains were isolated. Mesophilic isolates were Gram negative bacteria belonging to the genera Klebsiella, Pseudomonas, Stenotrophomonas and Burkholderia. Thermophilic isolates were members of the genus Bacillus. Despite the capability of the enrichment cultures to use tannic acid as single carbon and energy source, those cultures were unable to reduce the total polyphenols or the total organic carbon content of cork boiling wastewater. In order to increase the bioavailability of the organic carbon in cork boiling wastewater, biodegradation was preceded by Fenton oxidation. It was demonstrated that the combined process, using small amounts of Fenton reagents and biodegradative inoculum added almost simultaneously to cork boiling wastewater, leads to TOC reductions of more than 90%.     

The Climate Value of Cycling

The reduction of CO₂ emissions constitutes one of the largest challenges of the current era. Sustainable transportation, and especially cycling, can contribute to the mitigation of CO₂ emissions since cycling possesses an intrinsic zero‐emission value. Few studies have been conducted that appraise the CO₂ reduction potential of cycling. Opportunity costs enable the estimation of avoided CO₂ emissions resulting from bicycle trips. The methodology developed in this research allows the attribution of a climate value to cycling by substituting bicycle trips with their most likely alternative transportation modes and calculating the resulting additional CO₂ emissions. The methodology uses data on the current modal shares of cycling mobility, the competition of cycling with other transportation modes, and CO₂ emission factors to calculate the climate value of cycling. When it is assumed that the avoided CO₂ emissions of cycling mobility could be traded on financial carbon markets, the climate value of cycling represents a monetary value. Application of the methodology to the case of Bogotá, Colombia — a city with a current bicycle modal share of 3.3% on a total of 10 million daily trips — results in a climate value of cycling of 55,115 tons of CO₂ per year, corresponding to an economic value of between 1 and 7 million US dollars when traded on the carbon market.     

Approximate bilateral symmetry in evaporation-induced polycrystalline structures from droplets of wheat grain leakages and fluctuating asymmetry as quality indicator

The present paper reports on an observation that dendrite-like polycrystalline structures from evaporating droplets of wheat grain leakages exhibit bilateral symmetry. The exactness of this symmetry, measured by means of fluctuating asymmetry, varies depending on the cultivar and stress factor influence, and seems to correspond to the seed germination rate. In the bodies of plants, animals, and humans, the exactness of bilateral symmetry is known to reflect the environmental conditions of an organism’s growth, its health, and its success in sexual selection. In polycrystalline structures, formed under the same conditions, the symmetry exactness depends on the properties of the crystallizing solution such as the composition and viscosity; however, it has never been associated with sample quality. We hypothesize here that, as in living nature, the exactness of approximate bilateral symmetry might be considered a quality indicator also in crystallographic methods applied to food quality analysis.