Distribution and early life history of <Emphasis Type="Italic">Kaupichthys</Emphasis> leptocephali (family Chlopsidae) in the central Indonesian Seas

Leptocephali of the widely distributed tropical marine eels of the genus Kaupichthys (family Chlopsidae) were collected around Sulawesi Island during a sampling survey in the Indonesian Seas in late September and early October 2002, and the otolith microstructure of 24 of the 59 specimens captured was examined to learn about the larval growth rates and spawning times of these small sized eels. Leptocephali ranging in size from 25 to 60 mm were collected in Makassar Strait and the Celebes Sea, but they were most abundant in the semi-enclosed Tomini Bay of northeast Sulawesi Island. The Kaupichthys leptocephali examined had 39–161 otolith growth increments. Their back-calculated hatching dates indicated that five age groups were present and each group appeared to have been spawned around the full moon of previous months. Average growth rate estimates of the first two age groups were 0.65 and 0.54 mm/day for the 27.4–30.4 and 37.6–45.6 mm age classes. The growth rates of the oldest three age groups (52.0–60.8 mm) appeared to have slowed down after they reached their approximate maximum size. An increase in increment widths at the outer margin of the otoliths of those larger than 53 mm suggested that the process of metamorphosis had begun even though there were few external morphological changes indicating metamorphosis. It is hypothesized that chlopsid leptocephali have an unusually short gut that may not need to move forward during early metamorphosis. The presence of four age classes in Tomini Bay suggests that the Togian Islands region may be productive habitats for Kaupichthys juveniles and adults.     

Effects of sedimentation on the gorgonian <Emphasis Type="Italic">Subergorgia suberosa</Emphasis> (Pallas, 1766)

Effects of oceanic and terrestrial sediment suspensions on the behavioral traits activity, colony expansion, and mucus formation of the gorgonian octocoral Subergorgia suberosa (Pallas, 1766) were studied in the laboratory. Increased sediment concentration significantly changed the logits of activity indices (as colony expansion) and was correlated with decreased activity. For both sources of sediments, the activity index decreased as the concentration of sediment increased. The level of decrease was more significance for terrestrial sediments. The activity index showed no clear time pattern for the control group, but a decrease over time occurred in both sediment treatment groups. Activity change was linearly correlated with exposure time and concentration of terrestrial and ocean sediments. The activity indices of polyps were negatively correlated with the formation of mucus sheets (correlation = −0.536, p = 0.048). For both sources of sediments, the frequency of mucus sheet formation (MSF) increased with sediment concentration. Increases in terrestrial sediment loads resulted in more striking effects. The probability for MSF under different sediment groups at different concentrations over time was modeled by regressions. Frequency of polyp activity is suggested as a suitable biomarker to monitor the effects of sedimentation stress.     

A CFD study of the transport and fate of airborne droplets in a ventilated office: The role of droplet−droplet interactions

• Coulomb and Lennard−Jones forces were considered for droplet interactions. • The net droplet interactions were repulsive. • Repulsive droplet interactions increased the transport of droplets. • Repulsive droplet interactions significantly modified the fate of droplets. Previous studies reported that specially designed ventilation systems provide good air quality and safe environment by removing airborne droplets that contain viruses expelled by infected people. These water droplets can be stable in the environment and remain suspended in air for prolonged periods. Encounters between droplets may occur and droplet interactions should be considered. However, the previous studies focused on other physical phenomena (air flow, drag force, evaporation) for droplet transport and neglected droplet interactions. In this work, we used computational fluid dynamics (CFD) to simulate the transport and fate of airborne droplets expelled by an asymptomatic person and considered droplet interactions. Droplet drag with turbulence for prediction of transport and fate of droplets indicated that the turbulence increased the transport of 1 μm droplets, whereas it decreased the transport of 50 μm droplets. In contrast to only considering drag and turbulence, consideration of droplet interactions tended to increase both the transport and fate. Although the length scale of the office is much larger than the droplet sizes, the droplet interactions, which occurred at the initial stages of release when droplet separation distances were shorter, had a significant effect in droplet fate by considerably manipulating the final locations on surfaces where droplets adhered. Therefore, it is proposed that when an exact prediction of transport and fate is required, especially for high droplet concentrations, the effects of droplet interactions should not be ignored.     

Effects of cyanobacterium Microcystis aeruginosa on the filtration rate and mortality of the freshwater bivalve Corbicula leana

We compared filtering rates (FR) and mortalities between freshwater filter-feeding bivalve Corbicula leana acclimatized (AM) and non-acclimatized (NAM) to an cyanobacterial bloom (mainly Microcystis aeruginosa) over seven days. Both mussel populations were simultaneously stocked into mesocosms constructed in littoral zones of a eutrophic lake at a density of 740 ind. m(-2) for 16 days. NAMs decreased the concentration of chlorophyll-a 50% less than AMs. For the first seven days, the FRs (0.46-0.61) and mortality rate (slope = -30.2, r = -0.95) of NAMs were higher than those of AMs, possibly due to a sudden increase in unselective filtering. From the eighth day NAM mortality decreased rapidly and then stabilized, becoming similar to that of AMs through the end of the experiment. Stocking both AMs and NAMs increased the NH4-N concentration in the water, and the mortality rates of both mussel populations were correlated with NH4-N. In contrast, other nutrients and microcystin concentrations were not significantly associated with mussel mortality. These results indicate that although a sudden introduction of non-acclimatized C. leana may partially control phytoplankton biomass fora short period, previous short-term acclimatization is needed to minimize mussel mortality.     

Evaluation of food waste disposal options by LCC analysis from the perspective of global warming: Jungnang case, South Korea

The costs associated with eight food waste disposal options, dry feeding, wet feeding, composting, anaerobic digestion, co-digestion with sewage sludge, food waste disposer, incineration, and landfilling, were evaluated in the perspective of global warming and energy and/or resource recovery. An expanded system boundary was employed to compare by-products. Life cycle cost was analyzed through the entire disposal process, which included discharge, separate collection, transportation, treatment, and final disposal stages, all of which were included in the system boundary. Costs and benefits were estimated by an avoided impact. Environmental benefits of each system per 1 tonne of food waste management were estimated using carbon prices resulting from CO(2) reduction by avoided impact, as well as the prices of by-products such as animal feed, compost, and electricity. We found that the cost of landfilling was the lowest, followed by co-digestion. The benefits of wet feeding systems were the highest and landfilling the lowest.     

Identification and interpretation of representative ozone distributions in association with the sea breeze from different synoptic winds over the coastal urban area in Korea

To aid the studies of long-term impact assessment of cumulative ozone (O3) exposures, the representative 8-hr O3 pollution patterns have been identified over the Greater Seoul Area (GSA) in Korea. Principal component analysis and two-stage clustering techniques were used to identify the representative O3 patterns, and numerical and observational analyses were also used to interpret the identified horizontal distribution patterns. The results yielded three major O3 distribution patterns, and each of the three patterns was found to have strong correlations with local and synoptic meteorological conditions over the GSA. For example, pattern 1, accounting for 46% of O3 concentration distributions, mostly occurred under relatively weak westerly synoptic winds. The predominant features of this pattern were infrequent high O3 levels but a distinct gradient of O3 concentration from the western coastal area to the eastern inland area that was mainly induced by the local sea breeze. Pattern 2, accounting for 31% of O3 concentration distributions, was found with higher O3 levels in the western coastal area but lower in the eastern inland area. This is due to the modified sea breeze under the relatively stronger easterly opposing synoptic wind, affecting the high O3 occurrence in the western coastal area only. However, pattern 3, accounting for 21% of O3 concentration distributions, showed significantly higher O3 concentrations over the whole GSA mainly due to the retarded and slow-moving sea-breeze front under the weak opposing synoptic flow. Modeling study also indicated that local and synoptic meteorological processes play a major role in determining the high O3 concentration distribution patterns over the GSA.     

DIGITAL SIMULATION OF THE EFFECT OF THERMAL DISCHARGE ON STREAM WATER QUALITY1

A modified transient version of the Streeter-Phelps model along with the energy balance equation is employed to analyze the effects of waste heat discharge from power plants on stream water quality. Analysis is also made to examine the effects of the upstream water quality and stream velocity on the downstream DO concentration level. The resulting coupled nonlinear hyperbolic partial differential equations representing the energy, BOD and DO concentrations are solved by the method of characteristics and simulated on a digital computer. Final numerical results indicate that the allowable quantity of thermal discharge does heavily depend on the upstream quality.     

WATER QUALITY CONTROL BY ARTIFICIAL AERATION OF STREAM RECEIVING THERMAL AND ORGANIC WASTE DISCHARGES1

ABSTRACT: The purpose of this work is to study the installation of artificial aerators for water quality control of a stream which receives thermal and organic waste discharges. The location and numer of diffuser type aerators to be installed along the stream are determined so as to maintain the stream DO content above a certain minimum requirement (4 mg/l or 5 mg/l) for normal aquatic life. Effects of the stream velocity, upstream BOD concentration and rates of thermal and organic waste discharges to the stream are examined.     

ON TAXATION AND FIRMS CHOICE OF WASTE WATER TREATMENT TECHNOLOGY1

ABSTRACT: The interaction between the level of taxation and the firms accruing choice of treatment technology is discussed. It is shown that there is a risk of overtaxation, that is, simply increasing taxation may fail to improve environmental quality but only increase production costs and thus consumer prices.