The aim of this study is to elucidate the osmoregulatory capabilities of the intertidal pulmonate Onchidium tumidium. Our results indicate that O. tumidium could tolerate hyperosmotic stress more effectively than hypoosmotic stress. In 10% seawater (SW), it was capable of maintaining
its plasma hyperosmotic and hyperionic to the external medium. However, it rapidly gained weight in 10% SW, and no restoration
of body weight was observed. In contrast, in 90% SW it was able to recover its body weight partially. In a hyperosmotic medium,
accumulation of intracellular free amino acids (FAA) was responsible for cell volume regulation. The accumulated FAA might
originate from protein catabolism, which occurred in the internal organs (IO). In contrast, the relatively smaller amination:deamination
ratio of glutamate dehydrogenase in the body wall (BW) and IO of specimens exposed to hypoosmotic stress might lead to a higher
rate of amino acid catabolism. This was supported by the greater ammonia contents in the BW and IO of, and higher rate of
ammonia excretion by, specimens exposed to 10% SW.
Received: 11 March 1998 / Accepted: 2 May 1999 相似文献
Release and spreading of permanganate (MnO(4)(-)) in the well-based controlled-release potassium permanganate (KMnO(4)) barrier system (CRP system) was investigated by conducting column release tests, model simulations, soil oxidant demand (SOD) analyses, and pilot-scale flow-tank experiments. A large flow tank (L x W x D=8m x 4m x 3m) was constructed. Pilot-scale CRP pellets (OD x L=0.05 m x1.5m; n=110) were manufactured by mixing approximately 198 kg of KMnO(4) powders with paraffin wax and silica sands in cylindrical moulds. The CRP system (L x W x D=3m x 4m x 1.5m) comprising 110 delivery wells in three discrete barriers was constructed in the flow tank. Natural sands (organic carbon content=0.18%; SOD=3.7-11 g MnO(4)(-)kg(-1)) were used as porous media. Column release tests and model simulations indicated that the CRP system could continuously release MnO(4)(-) over several years, with slowly decreasing release rates of 2.5 kg d(-1) (day one), 109 g d(-1) (day 100), 58 g d(-1) (year one), 22 g d(-1) (year five), and 12 g d(-1) (year 10). Mean MnO(4)(-) concentrations within the CRP system ranged from 0.5 to 6 mg l(-1) during the 42 days of testing period. The continuously releasing MnO(4)(-) was gradually removed by SOD limiting the length of MnO(4)(-) zone in the porous media. These data suggested that the CRP system could create persistent and confined oxidation zone in the subsurface. Through development of advanced tools for describing agent transport and facilitating lateral agent spreading, the CRP system could provide new approach for long-term in situ treatment of contaminant plumes in groundwater. 相似文献
Ambient air quality measurements of 156 species including 39 alkanes, 32 alkenes, 2 alkynes, 24 aromatic hydrocarbons, 43 halocarbons and 16 carbonyls, were carried out for 120 air samples collected at two sampling stations (CW and TW) in 2001 throughout Hong Kong. Spatial variations of volatile organic compounds (VOCs) in the atmosphere were investigated. Levels of most alkanes and alkenes at TW site were higher than that at the CW site, while the BTEX concentrations at the two sites were close. The BTEX ratios at CW and TW were 1.6:10.1:1.0:1.6 and 2.1:10.8:1.0:2.0, respectively. For major halogenated hydrocarbons, the mean concentrations of chloromethane, CFCs 12 and 22 did not show spatial variations at the two sites. However, site-specific differences were observed for trichloroethene and tetrachloroethene. Furthermore, there were no significant differences for carbonyls such as formaldehyde, acetaldehyde and acetone between the two sites. The levels of selected hydrocarbons in winter were 1-5 times that in summer. There were no common seasonal trends for carbonyls in Hong Kong. The ambient level of formaldehyde, the most abundant carbonyl, was higher in summer. However, levels of acetaldehyde, acetone and benzaldehyde in winter were 1.6-3.8 times that in summer. The levels of CFCs 11 and 12, and chloromethane in summer were higher than that in winter. Strong correlation of most hydrocarbons with propene and n-butane suggested that the primary contributors of hydrocarbons were vehicular emissions in Hong Kong. In addition, gasoline evaporation, use of solvents, leakage of liquefied petroleum gas (LPG), natural gas leakage and other industrial emissions, and even biogenic emissions affected the ambient levels of hydrocarbons. The sources of halocarbons were mainly materials used in industrial processes and as solvents. Correlation analysis suggested that photochemical reactions made significant contributions to the ambient levels of carbonyls in summer whereas in winter motor vehicle emissions would be the major sources of the carbonyls. The photochemical reactivity of selected VOCs was estimated in this study. The largest contributors to ozone formation were formaldehyde, toluene, propene, m,p-xylene, acetaldehyde, 1-butene/i-butene, isoprene and n-butane, suggesting that motor vehicles, gasoline evaporation, use of solvents, leakage of LPG, photochemical processes and biogenic emission are sources in the production of ozone. On the other hand, VOCs from vehicles and gasoline evaporation were predominant with respect to reactions with OH radical. 相似文献
Trimethylamine (TMA) is an odorous volatile organic compound emitted by industries. Algal-based biotechnologies have been proven as a feasible alternative for wastewater treatment, although their application to abate polluted air emissions is still scarce. This work comparatively assessed the removal of TMA in a conventional bacterial bubble column bioreactor (BC) and a novel algal-bacterial bubble column photobioreactor (PBC). The PBC exhibited a superior TMA abatement performance compared to the conventional BC. In this sense, the BC reached a removal efficiency (RE) and an elimination capacity (EC) of 78% and 12.1 g TMA m?3 h?1, respectively, while the PBC achieved a RE of 97% and a EC of 16.0 g TMA m?3·h?1 at an empty bed residence time (EBRT) of 2 min and a TMA concentration ~500 mg m?3. The outstanding performance of the PBC allowed to reduce the operating EBRT to 1.5 and 1 min while maintaining high REs of 98 and 94% and ECs of 21.2 and 28.1 g m?3·h?1, respectively. Moreover, the PBC improved the quality of the gas and liquid effluents discharged, showing a net CO2 consumption and decreasing by ~ 30% the total nitrogen concentration in the liquid effluent via biomass assimilation. A high specialization of the bacterial community was observed in the PBC, Mumia and Aquamicrobium sp. being the most abundant genus within the main phyla identified.
Coarse (whole) and finely ground Ambersorb 1500 and coarse and fine coconut charcoal were compared as to their efficiencies in scavenging organic contaminants desorbed from sediment. Aqueous slurries of a test sediment spiked (1 ppm) with p,p′-DDE (DDE), 2,2′,5,5′-tetrachlorobiphenyl (TCB), naphthalene (NAP), or phenanthrene (PHEN), and containing 1% levels of the test carbons were treated by shaking at 35 °C while exposed to clusters of low-density polyethylene membrane (detox spiders). Controls consisted of spiked sediments and detox spiders but no added carbon of any kind and thus represented unimpeded bioavailabilities (to the spiders). After the treatments––agitation periods from 2.5 to 60 h, depending on contaminant hydrophobicity––the exposed detox spiders were analyzed. The fine carbon of either type was more effective than its coarser variant in obstructing contaminant bioavailabilities. The finer variants of both carbons obstructed the bioavailabilities of NAP and PHEN equally well as did the coarser variants of both. Whole Ambersorb 1500 and coarse coconut charcoal were similarly ineffective in intercepting TCB and DDE. Ground Ambersorb 1500 obstructed virtually all bioavailability of all four contaminants and was far more effective than fine coconut charcoal in intercepting DDE and TCB. An additional experiment compared the effectiveness of ground Ambersorb 1500 and fine coconut charcoal in obstructing the bioavailabilities from sediment of a broad array of spiked organochlorine pesticides. The performance of ground Ambersorb 1500 was again found to be superior; the bioavailable levels of each of the 27 pesticides were markedly lower in the presence of ground Ambersorb 1500 than in the presence of fine coconut charcoal. 相似文献
Colonies of Acropora microphthalma (Verrill 1869) were transferred from depths of 2 to 3, 10, 20, and 30 m to UV-transparent and UV-opaque respirometry chambers placed at 1 m depth at Bowl Reef, Great Barrier Reef, in March 1989. Peak rates of photosynthesis in colonies originating at 2 and 10 m were unaffected by solar ultraviolet (UV) radiation at 1 m, whereas photosynthesis showed 30 and 38% inhibition in colonies transferred from 20 and 30 m, respectively. This differential sensitivity of corals to UV radiation was consistent with the five- to tenfold higher concentrations of UV-absorbing, mycosporine-like amino acids (MAAs, putative defenses against UV) in 2- and 10-m colonies compared with 20- and 30-m colonies. Photosynthesis in zooxanthellae freshly isolated from 2- and 10-m corals, however, was inhibited by UV, indicating that the host's tissues, which contain 95% of the total MAAs in corals at these depths, are the first line of defense against solar UV and provide protection to their endosymbiotic algae. The general bathymetric decline in the activities of the antioxidant enzyme superoxide dismutase (SOD) in the host, and SOD, catalase, and ascorbate peroxidase in the zooxanthellae, is related to the decrease in potential for photooxidative stress with increasing depth. 相似文献
Courting male fiddler crabs Uca terpsichores (1 cm carapace width) sometimes build mounds of sand called hoods at the entrances to their burrows. Males wave their single
enlarged claws to attract females to their burrows for mating. It was shown previously that burrows with hoods are more attractive
to females and that females visually orient to these structures. In this study, we test whether males also use their hoods
to find their burrows. We first determined the maximum distance that males can see and find a burrow opening without a hood.
Males were removed from their burrows and placed on the sand at a range of distances from a burrow opening. If they were more
than about 8 cm (seven units of eye-height) away, they were unable find the burrow. In contrast, males that were burrow residents
used a non-visual path map to return to their burrows from much greater distances. To determine if hoods help males find their
burrows when there are errors in their path maps, we moved residents 1–49 cm on sliding platforms producing errors equal to
the distances they were moved. Males with self-made hoods or hood models at their burrows relocated their burrows at significantly
greater distances than did males with unadorned burrows. Hood builders also relocated their burrows faster. Hence, hoods have
two functions: they attract females and they provide a visual cue that males use to find their burrows quickly and reliably
when their path maps fail.
An erratum to this article can be found at 相似文献