Effects of SO<Subscript>2</Subscript> contamination on rising CO<Subscript>2</Subscript> drops under high pressure

Although the flow dynamics of pure liquid drops in other liquids has been well researched, little attention has been paid to the impacts of impurities. Hence, most of research is not directly applicable to the real world. To address this gap, we conducted numerical experiments simulating the rise of pure and contaminated drops. It was selected to study liquid CO₂ drops contaminated with SO₂ under high pressure because such mixtures mimic potential scenarios in which drops may leak from carbon capture and storage (CCS) facilities or pipelines. First, numerical simulation experiments were performed to validate our method by comparing our results with previous research on pure drops. Second, the validated numerical approach was applied to simulations of contaminated drops to investigate how contaminants affect rising drops. The results show that the SO₂ contamination caused changes in deformation, breakup phenomena, rising velocities, surrounding flow fields and drag coefficients. Most importantly, the contamination resulted in the formation of smaller “child drops”; such breakup is not observed in pure CO₂ drops. The formation of child drops in turn affects the streamlines, patterns and areas of wakes behind the contaminated drops. The addition of contaminants also enhances the dissolution rate, which is affected by the contaminant concentration and by the flow dynamics of the rising drop. Our results would improve understanding the rise of impure CO₂ drops, such as drops potentially leaked by future CCS operations.     

Exposure assessment of particulate matter and blood chromium levels in people living near a cement plant

This study evaluates the effect of air pollution caused by cement plants on nearby residential areas and performs an exposure assessment of particulate matter (PM) and total Cr, Cr⁶⁺, Pb, and Al. Further, the blood Cr levels of residents exposed to PM released by cement plants are also assessed. Nine buildings (eight residential and one elementary school building) close to cement plants were selected for this study, which were located in Pyeongtaek port, in west of Gyeonggi Province, South Korea. A total of 51 suspended particulate samples were collected at a flow rate of 2.0 L/min. Total Cr was more widely detected in residents’ houses and elementary schools. PM levels were higher at distances of 4.1 and 4.8 km than those at closer distances of 2.7 km. This was due to the influence of wind direction. The estimated mean blood level of Cr for the study participants was 3.80 μg/L, which is higher than levels estimated by other studies on Cr blood levels. Therefore, cement plants could cause an increase in total Cr and blood Cr levels in residential areas, and more continuous monitoring is necessary to better understand their impacts.     

Characterization of polycyclic aromatic hydrocarbons in urban stormwater runoff flowing into the tidal Anacostia River, Washington, DC, USA

To investigate the sources, fate, and transport dynamics of PAHs (polycyclic aromatic hydrocarbons) in stormwater runoff that is a leading source of pollution in urban watersheds, storm and base flow samples were collected in six branches along the lower Anacostia River. PAHs in storm flow (1510-12,500 ng/L) were significantly enriched in the particle phase, which accounted for 68-97% of the total PAHs. It suggests that reducing particles in stormwater using post-treatment system would decrease PAHs considerably. The solid-water distribution coefficients (KD) of PAHs in the storm flow samples were up to 340 times higher than predicted values. A greater portion of high molecular weight PAHs and their distribution patterns indicate higher contribution of automobile originated pyrogenic PAHs. Total suspended solids in storm flow had a positive relationship with flow rates and exceeded benchmark level for the protection of aquatic biota in some samples.     

Molecular approaches for the detection and monitoring of microbial communities in bioaerosols: A review

Bioaerosols significantly affect atmospheric processes while they undergo long-range vertical and horizontal transport and influence atmospheric chemistry and physics and climate change. Accumulating evidence suggests that exposure to bioaerosols may cause adverse health effects, including severe disease. Studies of bioaerosols have primarily focused on their chemical composition and largely neglected their biological composition and the negative effects of biological composition on ecosystems and human health. Here, current molecular methods for the identification, quantification, and distribution of bioaerosol agents are reviewed. Modern developments in environmental microbiology technology would be favorable in elucidation of microbial temporal and spatial distribution in the atmosphere at high resolution. In addition, these provide additional supports for growing evidence that microbial diversity or composition in the bioaerosol is an indispensable environmental aspect linking with public health.     

Barnacle suspension-feeding in variable flow

Suspension-feeding behavior of the adult barnacleSemibalanus balanoides (L.), collected at Woods Hole, USA, in 1987 and 1988, was studied in variable conditions of unidirectional and oscillating water flow. Barnacles growing on rocks were placed in a laboratory flume and exposed to precise patterns of water flow created with a specially designed electronic-circuit controlling a motor-driven propeller submersed in the flume. Laser darkfield and brightfield illumination were used to video-record the movement of suspended particles and dye in the flume and barnacle activity. When water was accelerated unidirectionally past feeding barnacles, they consistently changed feeding behavior from actively sweeping their thoracic appendages (cirri) through the water in slow-flow to passively holding cirri into the current in faster flow. The mean water velocity at which this behavioral switch occurred was 3.10 cm s^–1. In slow-flow, each active sweep of the cirri created a feeding vortex that caused suspended particles to swirl into the capture zone of the following sweep. Barnacles in simulated wave-action conditions (oscillatory flow) fed passively, and orientated extended cirri to flow direction. Cirri were rapidly reoriented with the same frequency at which flow direction reversed. Slow-motion analysis of one barnacle feeding in oscillating flow (0.65 Hz) indicated that reversal of the orientation of the cirri began 0.19 s before the water itself started to reverse direction. In additional experiments, barnacles were exposed to a repetitive pattern of accelerating-decelerating flow. During each flow cycle, barnacles switched from active to passive feeding as water accelerated. Repeated exposure of an individual to the same flow-cycle caused a consistent decrease in the water-velocity threshold at which the behavioral switch occurred.     

Occurence of intersexuality in a laboratory culture of the copepod Eurytemora affinis from the Seine estuary (France)

We show in this study that intersexuality can occur in the estuarine copepod Eurytemora affinis, and we reported the presence of three intersexual copepod individuals from a laboratory culture of this species from the Seine estuary conducted at low temperature (7°C). These individuals presented both female and male characteristics. The prosome size and antennules of intersex individuals were similar to those of normal females, but all the other morphological details were more similar to normal males. The appearance of the three intersex individuals in the culture at low temperature coincided with a decrease in food quality due to a feeding with Rhodomonas marina at its stationary phase. This induced a significant decrease in the mean clutch size and skewed sex-ratio in favor of males. The reduction in food quality in addition to low temperature of 7°C (which induced slow development) is suspected to be responsible of the appearance of intersex individuals. This stressful situation seems to propagate to the following two generations at low temperature in contrast to the case of the experiment at higher temperature 20°C where no intersex individual was observed. These results confirmed the role of food quality in sex determination of copepods. Moreover, the role of early developmental stages and also the consequences of stressful conditions throughout different generations were discussed.     

Sensitivity analysis on the ecological bias for Seoul tuberculosis data

In ecological studies, researchers often try to convey the analysis results to individual level based on aggregate data. In order to do this correctly, the possibility of ecological bias should be studied and addressed. One of the key ideas used to address the ecological bias issue is to derive the ecological model from the individual model and to check whether the parameter of interest in the individual model is identifiable in the ecological model. However, the procedure depends on unverifiable assumptions, and we recommend checking how sensitive the results are to these unverifiable assumptions. We analyzed the tuberculosis data that was collected in Seoul in 2005 using a spatial ecological regression model for the aggregate count data with spatial correlation, and found that the deprivation index is likely to have a small positive effect on the occurrence risk of tuberculosis in individual level in Seoul. We considered this finding in various aspects by performing in depth sensitivity analyses. In particular, our findings are shown to be robust to the distribution assumptions for the individual exposure and missing binary covariate across various scenarios.     

Historical trends of trace metals in a sediment core from a contaminated tidal salt marsh in San Francisco Bay

Sedimentation of metals preserves historical records of contaminant input from local and regional sources, and measurement of metals in sediment cores can provide information for reconstruction of historical changes in regional water and sediment quality. Sediment core was collected from Stege Marsh located in central San Francisco Bay (California, USA) to investigate the historical input of trace metals. Aluminum-normalized enrichment factors indicate that inputs from anthropogenic sources were predominant over natural input for Ag, Cu, Pb, and Zn. Among these, lead was the most anthropogenically impacted metal with enrichment factors ranging from 32 to 108. Depth profiles and coefficients of variation show that As, Cd, and Se were also influenced by anthropogenic input. The levels of these anthropogenically impacted metals decline gradually towards the surface due to regulation of the use of leaded gasoline, municipal and industrial wastewater discharge control, and closure of point sources on the upland of Stege Marsh. Although trace metal contamination is expected to be continuously declining, the rates of decline have slowed down. For lead, it is estimated to take 44, 82, and 153 years to decrease to probable effects level (112 μg/g), the San Francisco Bay ambient surface sediment level (43.2 μg/g), and the local baseline levels (5 μg/g), respectively. Some metals in surface sediments (0–6 cm) are still higher than sediment quality guidelines such as the probable effects level. To further facilitate the recovery of sediment quality, more efficient management plans need to be developed and implemented to control trace metals from non-point sources such as stormwater runoff.     

Water Transformation in the Media of Biofilters Controlled by Rhodococcus fascians in Treating an Ethyl Acetate-Contaminated Airstream

Abstract

Biofilters do not provide much water for bacteria to grow. To use them efficiently and properly, it is essential to understand the kinetics of water transformation and to control moisture levels. This study aims to clarify whether the metabolism of microorganisms will improve the water-holding capacity of media or will intensify drying. This experiment was conducted in duplicate, that is, both with and without bacterial inoculation. Both the constant water content mode and the declining water content mode show that microbial growth in a log phase will enhance drying. In contrast, the bacteria growing in a logarithmic decline phase will improve water-holding capacity. Basically, water evaporation can result from the latent heat obtained from microbial respiration or from the physical temperature difference between the unsaturated air and the wet media. Two ways that biofilters can gain water are from water incorporated into bacteria cells and from water obtained from the oxidation of volatile organic compounds (VOCs).