Behavior of particulate matter during high concentration episodes in Seoul

The behavior of particulate matter (PM) during high-concentration episodes was investigated using monitoring data from Guui station, a comprehensive air monitoring station in Seoul, Korea, from January 2008 to March 2010. Five non-Asian dust (ND) episodes and two Asian dust (AD) episodes of high PM concentrations were selected for the study. During the ND episode, primary air pollutants accumulated due to low wind speeds, and PM_2.5 increased along with most other air pollutants. Particles larger than PM_2.5 were also high since these particles were generated by vehicular traffic rather than wind erosion. During strong AD episodes, PM_10–2.5 primarily increased and gaseous primary air pollutants decreased under high wind speeds. However, even during the AD episode, PM_2.5 and gaseous primary air pollutants increased when the effects of AD were weak and wind speeds were low. This study corroborates that accumulation of air pollutants due to a drop in surface wind speed plays an important role in short-term high-concentration occurrences. However, low wind speeds could not be directly linked to local emissions because a significant portion of accumulated air pollutants resulted from long-range transport.     

Group-level organizational citizenship behavior: Effects of demographic faultlines and conflict in small work groups

Organizational scholars have recently shifted their attention to examining organizational citizenship behavior (OCB) as a group-level phenomenon. Adopting the input-mediator-outcome model of group performance, we examined antecedents and intermediate processes that predict group-level OCB (GOCB) in small work groups. The results, based on data from 62 work groups representing a variety of industries, revealed that demographic faultlines based on relation-oriented attributes (gender, age, and race) and a task-related attribute (tenure) had differentiated relationships with task and relationship conflict, which mediated the relationships between faultlines and group outcomes (GOCB and group performance). Both task and relationship conflict were negative predictors of group performance. However, task conflict increased GOCB, whereas relationship conflict decreased it. The present study offers evidence of the relationship between demographic faultlines and various group processes and outcome variables in natural work groups. Copyright © 2009 John Wiley & Sons, Ltd.     

Cooperative prey capture by young subsocial spiders: II. Behavioral mechanism

Subsocial spiders demonstrate an intermediate stage in the evolution of permanent sociality. Cooperative hunting is an important attribute of their sociality, but has not been documented in subsocial arthropods. After cannibalizing their mother, young of the subsocial spider Amaurobius ferox (Araneae, Amaurobiidae) remain together for several instars and feed communally. We monitored the collective prey capture behavior of the spiderlings. All the clutches showed collective capturing sequence (latency–orientation–moving–touching–seizing–feeding) toward the prey that was 10 times more massive than each individual. The first three individuals that exhibited attacking behavior were responsible for 90% of the total number of attacks, while 68% of the individuals within the group never exhibited attacks during the first 10 min following the introduction of prey into the communal web. First arriving individuals at the prey most often seized the antennae and legs of the prey, which probably facilitate access to the prey for subsequent individuals. The spiderlings that arrived later occupied more likely the abdomen and thorax, which contain more nutrition than the extremities occupied earlier. The individual apportionment of collective hunting behavior suggests a coordinated teamwork among individuals.     

Pilot-scale aerated submerged biofilm reactor for organics removal and nitrification at cold temperatures.

This research describes pilot-scale experiments for efficient removal of dissolved organic and nitrogen compounds in domestic wastewater using aerated submerged biofilm (ASBF) reactors. These reactors could enhance the performance of shallow wastewater treatment lagoons through the addition of specially designed structures. The structures are designed to encourage the growth of a nitrifying bacterial biofilm on a submerged surface. They also force the direct contact of rising air bubbles against the submerged biofilm. This direct gas-phase contact is postulated to increase the oxygen transfer rate into the biofilm and increase the microclimate mixing of water, nutrients, and waste products into and out of the biofilm. This research investigated the efficiency of dissolved organic matter and ammonia-nitrogen removals. Specifically, the effects of cold temperatures on the dissolved organic matter and ammonia-nitrogen performance of the ASBF pilot plant (see Figure 1) was investigated for the batch system. Over a period of 3.5 months, a total of 11 batch runs were performed. By the fourth run, the biofilm had matured to the point that it consumed all the ammonia in 40 hours. On the ninth run, the air supply was left off as a control run. This time, the ammonia was barely consumed, with the level dropping from 24 to 18 mg/L in 40 hours. By the middle of December, the average water temperature during the runs had dropped to approximately 6 degrees C and, at one point, was as low as 3.3 degrees C. The biofilm continued to perform even at these low temperatures, reducing ammonia levels from approximately 25 mg/L to basically zero within 40 to 48 hours.     

Effect of mixing ratio on sewage sludge and septage co-digestion

Journal of Material Cycles and Waste Management - Septage, which is made up of liquid and solid materials pumped from septic tanks, can be a potential co-digestion resource for sewage sludge. This...     

Effects of climatic factors on the prevalence of influenza virus infection in Cheonan,Korea

Environmental Science and Pollution Research - Big data can be used to correlate diseases and climatic factors. The prevalence of influenza (flu) virus, accounting for a large proportion of...     

A Framework to Develop Nationwide Flooding Extents Using Climate Models and Assess Forecast Potential for Flood Resilience

The methods used to simulate flood inundation extents can be significantly improved by high‐resolution spatial data captured over a large area. This paper presents a hydraulic analysis methodology and framework to estimate national‐level floodplain changes likely to be generated by climate change. The hydraulic analysis was performed using existing published Federal Emergency Management Agency 100‐year floodplains and estimated 100‐ and 10‐year return period peak flow discharges. The discharges were estimated using climate variables from global climate models for two future growth scenarios: Representative Concentration Pathways 2.6 and 8.5. River channel dimensions were developed based on existing regional United States Geological Survey publications relating bankfull discharges with channel characteristics. Mathematic relationships for channel bankfull topwidth, depth, and side slope to contributing drainage area measured at model cross sections were developed. The proposed framework can be utilized at a national level to identify critical areas for flood risk assessment. Existing hydraulic models at these “hot spots” could be repurposed for near–real‐time flood forecasting operations. Revitalizing these models for use in simulating flood scenarios in near–real time through the use of meteorological forecasts could provide useful information for first responders of flood emergencies.     

PCDD/DF in leachates from Korean MSW landfills

We analyzed levels of PCDD/DF in leachate liquid and solid from five Korean municipal solid waste landfills to investigate the relationship between PCDD/DF and dissolved organic carbon and suspended solids in raw leachate. The concentrations of PCDD/DF ranged from 173.2 to 1329.4 pg/l and 4.1 to 46.22 pg-TEQ/l. The range of PCDD/DF was 123.2-1161.3 pg/l in leachate solid and 50.0-383.3 pg/l in leachate liquid. Our results indicated that PCDD/DF in solid play a major role in determining their concentration levels, and the distribution of isomers in solid was almost the same as in liquid leachate. In addition, highly chlorinated PCDD/DF, such as HpCDD/DF and OCDD/DF, accounted for more than 70% of all isomers. Levels of PCDD/DF in liquid were strongly correlated with dissolved organic carbon concentrations, which increase the leachability (R2 = 0.92 in Korean leachate) of PCDD/DF from contaminant sources. Despite this high linearity between dissolved organic carbon and dissolved PCDD/DF, we observed no strong relationship between dissolved organic carbon and solid phase PCDD/DF (R2 = 0.001). Dissolved organic carbon scarcely affects dissolved PCDD/DF to be combined with solids. As a result, it is not appropriate for incinerated ash to be dumped with municipal solid wastes, as they have a large potential to result in high levels of organic matter, and therefore PCDD/DF, in leachate.     

Influence of a municipal solid waste incinerator on ambient air and soil PCDD/Fs levels

To examine the influence of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) emissions from a municipal solid waste incinerator (MSWI) on the environment, we measured the levels of PCDD/Fs in ambient air and soil samples collected near a MSWI in Bucheon, Korea. The PCDD/Fs concentrations in the ambient air samples ranged from 0.22 to 1.16 pg I-TEQm(-3) (13.39-75.16 pg m(-3)), with an average of 0.66 pg I-TEQ m(-3) (35.62 pg m(-3)). The soil samples contained between 1.25 and 74.98 pg I-TEQ g(-1) (38.15-3,303.33 pg g(-1)), with an average of 19.06 pg I-TEQ g(-1) (1,077.11 pg g(-1)). These levels were higher than those previously reported by other investigators in a number of surveys. The furan homologues predominated in the air samples and some soil samples, and the soil PCDD/Fs levels decreased with increasing distance from the MSWI. Comparison of the homologue patterns and a multivariate statistical analysis showed that PCDD/Fs emission from the MSWI directly affected the pattern of PCDD/Fs in air, while the PCDD/Fs patterns in soil differed according to the location relative to the MSWI, roads, and construction sites. These results collectively indicate that the MSWI was the major PCDD/Fs emission source in this area, but that unidentified combustion sources and vehicles might influence the environment to some extent.