Radon concentrations in groundwater in Busan measured with a liquid scintillation counter method

In this paper, we present the first measurement of radon concentrations in drinking groundwater from private and public deep-bored wells located in the south-eastern area of Korea. The measurements were carried out on 439 samples by using a liquid scintillation method. The results show that the radon concentrations of the samples range from 0 to about 300 Bq l(-1). We find that Sasang ward shows the highest median value of radon concentration among 13 different wards, while Jung ward has the lowest. We find that the radon concentrations are highly dependent on the type of geological rock aquifers.     

Demonstration of a high throughput on-board hydrogen generation reactor system using aluminum coil as fuel for a vehicle

A novel on-board hydrogen generation concept using Al coil with NaOH was investigated. The reaction rate was successfully controlled by introducing a pumping system for the NaOH solution. The time for the flow to develop fully was mainly dependent on the solution temperature, and the fastest start time recorded was 60 sec at a solution temperature of 70°C. The maximum H₂ generation rate was 200 L min^–1 with a prototype design of the on-board hydrogen generation system 1/8 times the size of a full-size reactor. The H₂ generation process coupled with the solution pumping system was simulated with three-dimensional fluid dynamic software, and the calculated H₂ flow and temperature rise of the system were validated with experimental data.     

An evaluation of indoor and outdoor biological particulate matter

The incidences of allergies, allergic diseases and asthma are increasing world wide. Global climate change is likely to impact plants and animals, as well as microorganisms. The World Health Organization, U.S. Environmental Protection Agency, U.S. Department of Agriculture, U.S. Department of Health and Human Services, and the Intergovernmental Panel on Climate Change cite increased allergic reactions due to climate change as a growing concern. Monitoring of indoor and ambient particulate matter (PM) and the characterization of the content for biological aerosol concentrations has not been extensively performed. Samples from urban and rural North Carolina (NC), and Denver (CO), were collected and analyzed as the goal of this research. A study of PM₁₀ (<10 μm in aerodynamic diameter) and PM_2.5 (<2.5 μm in aerodynamic diameter) fractions of ambient bioaerosols was undertaken for a six month period to evaluate the potential for long-term concentrations. These airborne bioaerosols can induce irritational, allergic, infectious, and chemical responses in exposed individuals. Three separate sites were monitored, samples were collected and analyzed for mass and biological content (endotoxins, (1,3)-β-d-glucan and protein). Concentrations of these bioaerosols were reported as a function of PM size fraction, mass and volume of air sampled. The results indicated that higher concentrations of biologicals were present in PM₁₀ than were present in PM_2.5, except when near-roadway conditions existed. This study provides the characterization of ambient bioaerosol concentrations in a variety of areas and conditions.     

Warning signals confer advantage to prey in competition with predators: bumblebees steal nests from insectivorous birds

Aposematic (warning) signals of prey help predators to recognize the defended distasteful or poisonous prey that should be avoided. The evolution of aposematism in the context of predation has been in the center of modern ecology for a long time. But, the possible roles of aposematic signals in other ecological contexts have been largely ignored. Here we address the role of aposematic signals in competition between prey and predators. Bumblebees use visual and auditory aposematic signals to warn predators about their defenses. For 2 years, we observed competition for nestboxes between chemically defended insects, Bombus ardens (and possibly also Bombus ignitus), and cavity nesting birds (Parus minor and Poecile varius). Bumblebees settled in 16 and 9 % of nestboxes (in 2010 and 2011 breeding seasons, respectively) that contained bird nests at the advanced stage of nest building or at the stage of egg laying. Presence of bumblebees prevented the birds from continuing the breeding activities in the nestboxes, while insects took over the birds’ nests (a form of kleptoparasitism). Playback experiments showed that the warning buzz by bumblebees contributed to the success in ousting the birds from their nests. This demonstrates that aposematic signals may be beneficial also in the context of resource competition.     

As(III) adsorption onto Fe-impregnated food waste biochar: experimental investigation,modeling, and optimization using response surface methodology

Biochar derived from food waste was modified with Fe to enhance its adsorption capacity for As(III), which is the most toxic form of As. The synthesis of Fe-impregnated food waste biochar (Fe-FWB) was optimized using response surface methodology (RSM), and the pyrolysis time (1.0, 2.5, and 4.0 h), temperature (300, 450, and 600 °C), and Fe concentration (0.1, 0.3, and 0.5 M) were set as independent variables. The pyrolysis temperature and Fe concentration significantly influenced the As(III) removal, but the effect of pyrolysis time was insignificant. The optimum conditions for the synthesis of Fe-FWB were 1 h and 300 °C with a 0.42-M Fe concentration. Both physical and chemical properties of the optimized Fe-FWB were studied. They were also used for kinetic, equilibrium, thermodynamic, pH, and competing anion studies. Kinetic adsorption experiments demonstrated that the pseudo-second-order model had a superior fit for As(III) adsorption than the pseudo-first-order model. The maximum adsorption capacity derived from the Langmuir model was 119.5 mg/g, which surpassed that of other adsorbents published in the literature. Maximum As(III) adsorption occurred at an elevated pH in the range from 3 to 11 owing to the presence of As(III) as H₂AsO₃^? above a pH of 9.2. A slight reduction in As(III) adsorption was observed in the existence of bicarbonate, hydrogen phosphate, nitrate, and sulfate even at a high concentration of 10 mM. This study demonstrates that aqueous solutions can be treated using Fe-FWB, which is an affordable and readily available resource for As(III) removal.

     

The effect of estimated PAR uncertainties on the physiological processes of biosphere models

Photosynthetically active radiation (PAR) energy reaching on the vegetated surface is a key determinant of plant physiological processes. Most of biosphere or crop models use the ratio of PAR to incoming solar radiation (R_s), PAR/R_s, to convert R_s into PAR in order to reduce weather data-input requirements. Several existing models simply specify a constant ratio, PAR/R_s = 0.5. However, some field experiments have reported that the ratio PAR/R_s may not be constant. Previous empirical equations of PAR/R_s were derived based on the data of monthly or daily timescales collected from only a few measurement sites, hence they may not be appropriate to be used in current global biosphere models usually with hourly simulation time steps. Here, we represent the exponential correlation between PAR/R_s and sky clearness index (0-1) using hourly data from 54 Ameriflux measurement sites. It is found that PAR/R_s increases up to 0.6 in cloudy conditions when the clearness index (CI) is below ∼0.2, whereas it is nearly constant at ∼0.42 when CI is above 0.2. When the identified empirical equation is used in the model simulation, it results in −4 to 2% difference in the stomatal conductance compared to that using the constant ratio PAR/R_s = 0.5.     

Effect of sequentially combining methanol and acetic acid on the performance of biological nitrogen and phosphorus removal

A sequentially combined carbon (SCC) source using methanol and acetic acid was investigated for biological nitrogen and phosphorus removal in a wastewater treatment process consisting of an anoxic zone, an oxic zone and a final settling tank. The anoxic zone was divided into two separate anoxic zones to feed methanol in the first anoxic zone and acetic acid in the second anoxic zone. Methanol and acetic acid, each as the sole carbon source, were also tested for comparison. The use of SCC was superior in nitrogen removal with all combined COD ratios of methanol/acetic acid tested, yielding 95.8-97% efficiency (less than 1 mg N/l in the final effluent). The highest phosphorus removal of above 92% (final effluent concentration of 0.12 mg P/l) was achieved when only acetic acid was used at a quantity equivalent to 50 mg COD/l. However, when SCC was used, the acetic acid dosage of 50 mg COD/l could be reduced down to 20 mg COD/l when 30 mg COD/l was replaced by methanol; this resulted in a final effluent phosphorus concentration of 0.6 mg P/l. Additional benefits of SCC included the excellent sludge settling properties compared to the use of methanol or acetic acid alone.     

Effects of a dynamic membrane formed with polyethylene glycol on the ultrafiltration of natural organic matter

The formation of a dynamic membrane (DM) was investigated using polyethylene glycol (PEG) (molecular weight of 35000 g/mol, concentration of 1 g/L). Two natural organic matters (NOM), Dongbok Lake NOM (DLNOM) and Suwannee River NOM (SRNOM) were used in the ultrafiltration experiments along with PEG. To evaluate the effects of the DM with PEG on ultrafiltration, various transport experiments were conducted, and the analyses of the NOM in the membrane feed and permeate were performed using high performance size exclusion chromatography, and the effective pore size distribution (effective PSD) and effective molecular weight cut off (effective MWCO) were determined. The advantages of DM formed with PEG can be summarized as follows: (1) PEG interferes with NOM transmission through the ultrafiltration membrane pores by increasing the retention coefficient of NOM in UF membranes, and (2) low removal of NOM by the DM is affected by external factors, such as pressure increases during UF membrane filtration, which decreases the effective PSD and effective MWCO of UF membranes. However, a disadvantage of the DM with PEG was severe flux decline; thus, one must be mindful of both the positive and negative influences of the DM when optimizing the UF performance of the membrane.     

WATER MANAGEMENT AND N,P LOSSES FROM PADDY FIELDS IN SOUTHERN KOREA1

ABSTRACT: Assessment and control of nutrient losses from paddy fields is important to protect water quality of lakes and streams in Korea. A four‐year field study was carried out to investigate water management practices and losses of nitrogen (N) and phosphorus (P) in rice paddy irrigation fields in southern Korea. The amount and water quality of rainfall, irrigation, surface drainage, and infiltration were measured and analyzed to estimate inputs and losses of N and P. The observed irrigation amount surpassed consumptive use, and approximately 52 to 69 percent of inflow (precipitation plus irrigation) was lost to surface drainage. Field data showed that significant amounts of irrigation water and rainfall were not effectively used for rice paddy culture. Water quality data indicated that drainage from paddy fields could degrade the recipient water environment. The nutrient balance indicated that significant amounts of nutrients (29.5 percent of total N and 8.6 percent of total P compared to input) were lost through surface drainage. Furthermore, up to half the nutrient losses occurred during nonstorm periods. The study results indicate that inadequate water management influences N and P losses during both storm and nonstorm periods. Proper water management is required to reduce nutrient losses through surface drainage from paddy fields; this includes such measures as minimum irrigation, effective use of rainfall, adoption of proper drainage outlet structures, and minimized forced surface drainage.