Effect of Bag Failure on Baghouse Outlet Loading

One of the most important considerations in baghouse operation is the effect of bag failure on outlet loading. This information would be Of use to equipment manufacturers, users, and regulatory officials. Unfortunately, little information is available in the literature on this aspect of baghouse performance. Equations describing changes in outlet loading resulting from the sudden rupture of one or more bags are developed from first principles. Calculated results from these equations are presented in the form of a chart which can very quickly and simply be used to obtain a numerical value for a revised outlet loading resulting from bag failure(s) for a variety of system conditions. Due to an assumption made in the derivation, the new outlet loading thus obtained represents the maximum increase (worst case conditions) to be expected from the rupture of one or more bags. The following variables are included in the analysis: inlet loading, outlet loading (prior to bag failure), number of bag failures, bag diameter, system pressure drop; and gas temperature.     

Examining the concept of convenient collection: An application to extended producer responsibility and product stewardship frameworks

Increasingly, Extended Producer Responsibility (EPR) and Product Stewardship (PS) frameworks are being adopted as a preferred policy approach to promote cost-effective diversion and recovery of post-consumer solid waste. Because the application of EPR/PS generally requires the creation of a separate and often parallel collection and/or management system, key to increasing the amount of waste recovered is to maximize the convenience of the collection system to maximize consumer participation. Convenient collection is often mandated in EPR/PS laws, however it is not defined. Convenience is a subjective construct rendering it extremely difficult to define. However, based on a dissection of post-consumer collection efforts under a generic EPR/PS system, this paper identifies and examines five categories of convenience – knowledge requirements, proximity to a collection site, opportunity to drop-off materials, the draw of the collection site, and the ease of the process—and the various factors of convenience within each of these categories. By using a simplified multiple criteria decision analysis, this paper proposes a performance matrix of criteria of convenience. Stakeholders can use this matrix to assist in the design, assessment, and/or implementation of a convenient post-consumer collection system under an EPR/PS framework.     

Statistical Issues for Monitoring Ecological and Natural Resources in the United States

The United States funds a number of national monitoring programs to measure the status and trends of ecological and natural resources. Each of these programs has a unique focus; the scientific objectives are different as are the sample designs. However, individuals and committees, all well aware of the cost of ecological monitoring, have called for more effective monitoring programs. The objective of this paper is to summarize existing programs' statistical designs and discuss potential alternatives for improvement in national monitoring. Can we improve the current situation by providing an overall framework for the design or analysis of data from these disparate surveys? First, the paper summarizes the objectives of these surveys, compares and contrasts their survey designs as currently implemented, and determines what variables they collect. Through this process we identify commonalities and issues that impact our ability to combine information across one or more of the surveys. Three potential alternatives are presented, leading to comprehensive monitoring in the United States.     

Impact of different land uses on polycyclic aromatic hydrocarbon contamination in coastal stream sediments

PAHs are ubiquitous environmental pollutants that can cause adverse health and ecological effects. In the present study, we examined the impact of land use on the concentration and composition of PAHs in 28 coastal stream sediments on the Island of Oahu, Hawaii. In densely populated urban areas, the concentration range of total PAHs in the stream sediments affected by mixed residential and industrial activities (RI) are 0.40-9.05 ppm, which is significantly higher than the 0.36-4.21 ppm detected in the stream sediments affected predominantly by urban residential land uses (UR). The stream sediments affected by agricultural activities (AG) reported a concentration range of 0.09-2.14 ppm, which is lower than those of the RI and UR stream sediments. The molecular weight of PAH is a factor, as only high molecular weight (HMW) PAHs were significantly affected by land uses (ANOVA P = 0.009). Correlation analysis showed that only in the UR stream sediments were significant correlations observed between PAH concentration and two anthropogenic indicators: population density (r = 0.57, P = 0.027) and vehicle density (r = 0.55, P = 0.034). The fractional concentrations of PAHs were analyzed by using PCA analysis, which led to the separate clustering of the RI and AG stream sediments and suggest distinct PAH sources between the two land uses. Two PAH source indicators, including Ant/(Ant + Phe) and Fl/(Fl + Py), indicates that PAHs sources in the RI stream sediments are most likely of petroleum origin, while PAHs in the UR and AG stream sediments most likely came from combustion activities. In addition, the concentration and relative potency of carcinogenic PAHs in the coastal stream sediments exhibited similar patterns as the total PAH concentration with respect to land uses.     

An evaluation of the performance of multiple passive diffusion devices for indoor air sampling of VOCs

The United States Environmental Protection Agency is considering recommending longer‐term sampling to achieve more accurate time‐weighted‐average detections for indoor air monitoring of volatile organic chemicals. The purpose of the research presented herein was to compare longer sampling times using passive diffusion samplers to the results from shorter‐term testing periods using sorbent tubes and low‐flow pumps (US EPA Method TO‐17) at great frequency for trichloroethene (TCE) in indoor air. A controlled release of TCE in a large room allowed for over two‐orders‐of‐magnitude daily concentration variability over the course of the two‐week monitoring event. The daily concentration measurements by US EPA Method TO‐17 and the passive diffusion samplers were performed in triplicate and had excellent reproducibility. The results of daily tests were averaged and compared with four passive diffusion devices exposed to indoor air for three, seven, ten, and fourteen days in accordance with ASTM D6196‐02. A specific uptake rate for each of the passive devices at the four different time intervals and the statistical significance of the time‐varying uptake rates were evaluated. The performance of each passive diffusion device was determined using a statistical performance criterion. The average concentration for all of the exposure periods could be reliably predicted using the established uptake rates for two of the four passive devices. © 2009 Wiley Periodicals, Inc.     

Arsenic speciation in arsenic-rich Brazilian soils from gold mining sites under anaerobic incubation

BACKGROUND: Arsenic speciation in environmental samples is essential for studying toxicity, mobility and bio-transformation of As in aquatic and terrestrial environments. Although the inorganic species As(III) and As(V) have been considered dominant in soils and sediments, organisms are able to metabolize inorganic forms of arsenic into organo-arsenic compounds. Arsenosugars and methylated As compounds can be found in terrestrial organisms, but they generally occur only as minor constituents. We investigated the dynamics of arsenic species under anaerobic conditions in soils surrounding gold mining areas from Minas Gerais State, Brazil to elucidate the arsenic biogeochemical cycle and water contamination mechanisms. METHODS: Surface soil samples were collected at those sites, namely Paracatu Formation, Banded Iron Formation and Riacho dos Machados Sequence, and incubated in CaCl2 2.5 mmol L(-1) suspensions under anaerobic conditions for 1, 28, 56 and 112 days. After that, suspensions were centrifuged and supernatants analyzed for soluble As species by IC-ICPMS and HPLC-ICPMS. RESULTS: Easily exchangeable As was mainly arsenite, except when reducible manganese was present. Arsenate was mainly responsible for the increase in soluble arsenic due to the reductive dissolution of either iron or manganese in samples from the Paracatu Formation and Riacho dos Machados Sequence. On the other hand, organic species of As dominated in samples from the Banded Iron Formation during anaerobic incubation. DISCUSSION: Results are contrary to the expectation that, in anaerobic environments, As release due to the reductive dissolution of Fe is followed by As(V) reduction to As(III). The occurrence of organo-arsenic species was also found to be significant to the dynamics of soluble arsenic, mainly in soils from the Banded Iron Formation (BIF), under our experimental conditions. CONCLUSIONS: In general, As(V) and organic As were the dominant species in solution, which is surprising under anaerobic conditions in terrestrial environments. The unexpected occurrence of organic species of As was attributed to enrollment of ternary organic complexes or living organisms such as algae or cyanobacteria. PERSPECTIVES: These findings are believed to be useful for remediation strategies in mine-affected regions, as the organic As species are in general considered to be less toxic than inorganic ones and even As(V) is considered less mobile and toxic than As(III).     

Fate of PCBs, PAHs and their source characteristic ratios during composting and digestion of source-separated organic waste in full-scale plants

Composting and digestion are important waste management strategies. However, the resulting products can contain significant amounts of organic pollutants such as polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs). In this study we followed the concentration changes of PCBs and PAHs during composting and digestion on field-scale for the first time. Concentrations of low-chlorinated PCBs increased during composting (about 30%), whereas a slight decrease was observed for the higher chlorinated congeners (about 10%). Enantiomeric fractions of atropisomeric PCBs were essentially racemic and stable over time. Levels of low-molecular-weight PAHs declined during composting (50-90% reduction), whereas high-molecular-weight compounds were stable. The PCBs and PAHs concentrations did not seem to vary during digestion. Source apportionment by applying characteristic PAH ratios and molecular markers in input material did not give any clear results. Some of these parameters changed considerably during composting. Hence, their diagnostic potential for finished compost must be questioned.     

Emissions and distribution of methyl bromide in field beds applied at two rates and covered with two types of plastic mulches

A field experiment was conducted to compare two plastic mulches and two application rates on surface emissions and subsurface distribution of methyl bromide (MBr) in field beds in Florida. Within 30 minutes after injection of MBr to 30 cm depth, MBr had diffused upward to soil surface in all beds covered with polyethylene film (PE) or virtually impermeable film (VIF) and applied at a high rate (392 kg/ha) and a low rate (196 kg/ha). Due to the highly permeable nature of PE, within 30 minutes after injection, MBr volatilized from the bed surfaces of the two PE-covered beds into the atmosphere. The amount of volatilization was greater for the high rate-treatment bed. On the other hand, volatilization of MBr from the bed surfaces of the two VIF-covered beds were negligible. Volatilization losses occurred from the edges of all the beds covered with PE or VIF and were greater from the high rate-treatment beds. Initial vertical diffusion of MBr in the subsurface of the beds covered with PE or VIF was mainly upward, as large concentrations of MBr were detected from near bed surfaces to 20 cm depth in these beds 30 minutes after injection and little or no MBr was found at 40 cm depth. The two VIF-covered beds exhibited greater MBr concentrations and longer resident times in the root zone (0.5-40 cm depth) than corresponding PE-covered beds. Concentrations of MBr in the root zone of the high rate-treatment beds were 3.6-6.1 times larger than the low rate-treatment beds during the first days after application. In conclusion, VIF promoted retention of MBr in the root zone and, if volatilization loss from bed edges can be blocked, volatilization loss from VIF-covered beds should be negligible.     

Heart rate changes reveal that little blue penguin chicks (Eudyptula minor) can use vocal signatures to discriminate familiar from unfamiliar chicks

Researchers investigating social recognition typically measure only behavioural responses during discrimination tests - physiological changes have been largely ignored. We examined whether little blue penguin chicks (Eudyptula minor) could distinguish siblings from other chicks using auditory cues, by measuring behavioural and heart rate changes during playback experiments. Chicks were exposed to five treatments: the begging calls of siblings, neighbouring chicks and unfamiliar chicks, and two controls (heterospecific begging calls and music). We also determined if chicks developed distinctive begging calls, by using F-ratios to quantify inter- versus intra-individual variability in a range of acoustic parameters, and applying a discriminant-function analysis. Inter-individual variation was greater for pitch than for temporal or amplitude parameters, suggesting that call pitch may be important for individual recognition. The discriminant-function analysis showed each chick's calls were distinctive and could act as a vocal signature. Treatments did not instigate different behavioural responses. However, chick heart rates during playback of sibling calls were significantly higher than those recorded during stranger, but not neighbour, playback. A simple recognition system based on familiarity may allow this plesiomorphic and loosely colonial penguin to gain at least some of the benefits associated with more advanced sibling recognition systems (some highly colonial seabirds discriminate siblings from neighbouring chicks). Heart rate could be a useful measure of social recognition abilities, particularly in species where changes in behaviour are not always evident or are difficult to observe.