When the toxicity of marine sediment in Hong Kong was evaluated, it was found that the seven sediments collected within Victoria Harbour were severely contaminated with heavy metals, at concentrations many times higher than those in sediments collected from outside the harbour. The highest metal content was recorded in site VS14 (located near the airport runway and the industrialized area), with copper, zinc, lead and chromium values of 3789, 610, 138 and 601 mg kg−1 dry wt, respectively. This site also had the greatest alkaline phosphatase activities (15 fluorescent intensity unit g−1 wet wt), the largest number of total coliforms (910 CFU g−1 wet wt) and sulphate-reducing bacteria (8.5 × 104 cells g−1 wet wt), implying that site VS14 was also contaminated with organic matter and nutrients. Sediment bioassays, Microtox and algal tests, demonstrated that sediment elutriates obtained from site VS14 were of greatest toxicity. The EC10 value in Microtox tests was 17% elutriate, and the 96-h IC50 values using Skeletonema costatum and Dunaliella tertiolecta were 40 and 79% elutriate, respectively. No toxic effects were found in sediment samples collected from the control site outside Victoria Harbour. Significant correlations were found between the results of the algal toxicity test (using S. costatum) and the coliform count and metal content of the sediments. The Microtox test was less sensitive than the algal bioassay, and no sediment elutriate, even from the site mostly contaminated by heavy metals, caused more than 50% inhibition of the light-emitting activity of the bacteria. In this study, S. costatum (the diatom) provided a more sensitive and reliable test species than D. tertiolecta (the flagellate) in differentiating the toxicity of marine sediments. 相似文献
The effect of size and tissue parts as well as site locations on a suite of six anti-oxidative biochemical markers, viz. the enzyme degrading neural transmitters acetylcholinesterase (AChE), the Phase II transforming enzyme glutathione-S-transferase (GST), the anti-oxidative enzymes superoxide dismutase (SOD) and catalase (CAT), the lipid metabolite malondialdehyde (MDA) and the ratio of CAT/MDA, in the bivalve mollusc, Perna viridis, was studied. Field mussels were collected from the piers of University of Science and Technology (UST), Pak Sha Wan or Hebe Haven (PS) and Sai Kung (SK) in Port Shelter, Hong Kong. Statistically, ANOVA showed that the activity of all six biochemical markers were generally tissue dependent, size independent and location dependent. Tukey multi comparison test indicated that the biochemical activities fell into two groups, with SK the highest activity group in most cases. The significance of these findings in relation to long-term coastal water biomonitoring is discussed. 相似文献
The Hawaii Geothermal Project (HGP) was organized in 1972 to locate and utilize geothermal energy resources in Hawaii. A geophysical program was designed to select a site of high potential for a geothermal resource and to develop an understanding of the thermal processes of a basaltic volcano and its associated rift zones.The well was completed in July 1976 and after subsequent clearing was producing at 5800 kg/hr with a well head pressure of 11 kg/cm2 and a temperature of 190°C (equivalent to 3.5 MW of electrical energy).The discharge fluid was only slightly saline despite the termination of the well 1768 m below sea level. The water was nearly depleted in magnesium but contained high concentrations of silica and sulfide. Geochemical thermometers based on the data of Fournier, Rowe, White, Ellis, and Truesdell are in excellent agreement with the measured downhole temperature of 275°C.Stable and radioactive isotope analyses for 14C, 13C and 13O indicate that 66% of the recharge is from local rainfall with a turnover of at least several hundred years. The remaining discharge is derived from sea water (10%) and hydrothermally altered fluids. Analyses for the gases CO2, He and 3He indicate that the fluids have a deep-seated or magmatic source. 相似文献
The relative roles of internal atmospheric dynamics, land surface evaporation and sea surface temperature (SST) forcings
on the coupling between the Asian monsoon (AM) and the Southern Oscillation (SO) are investigated in a series of GCM experiments.
Results confirm previous studies indicating that the characteristic large-scale pattern of the SO is due primarily to SST
anomaly (SSTA) forcing. The AM circulation anomalies are coupled to the SO via a characteristic upper level circulation couplet
over the equatorial central Pacific. This couplet acts as a radiating node for teleconnection signals originating from the
AM region to the extratropics. Generally, a weak AM is associated with warm SST over the eastern equatorial Pacific, concomitant
with the negative phase of the SO, i.e., low (high) surface pressure over Tahiti (Darwin). The reverse holds for strong AM.
Two wavetrains associated with the AM fluctuation have been identified: one arcing over northeastern Asia via the Aleutians
to North American, and another emanating from northwestern Europe, via Siberia to northern India. Internal dynamics appear
to underpin the origin of these wavetrains, which are strongly tempered by SSTA forcing and to a lesser degree by interactive
land processes. Regionally, land-atmosphere interaction seems to have the strongest impact over East Asia/Indochina and the
adjacent oceanic region of the South China Sea. Here, land-atmosphere interaction is responsible for the enhancement of a
subseasonal scale see-saw oscillation in precipitation between land and the adjacent oceans. A local land-atmosphere feedback
mechanism involving strong coupling between the hydrologic and energy cycles is identified. It is suggested that the interaction
among precipitation, moisture convergence and land surface turbulent heat fluxes and radiation processes play key roles in
determining the fast (subseasonal and shorter scales) response of the AM. On these time scales, the occurrences of cool/wet
and hot/dry states associated with the precipitation seesaw appear to be chaotic. However, the preferred occurrence of a given
state and the abrupt transition between states are dependent on the large-scale circulation and radiation forcings induced
by the SO. One of the more provocative findings here is that effects of land-atmosphere interaction do not seem to alter the
basic planetary scale features of the AM-SO system. As a result, the interannual variability of the coupled AM-SO is relatively
small in the absence of anomalous SST forcing. Yet, the local effect of land-atmosphere interaction on AM is quite pronounced
and dependent upon the large-scale forcings related to SO.
Received: 18 November 1997 / Accepted: 07 April 1998 相似文献
Storm surges are cataclysmic natural disasters that occur along the coasts and are usually accompanied by large waves. The effects of coupled storm surges and waves can pose a significant threat to coastal security. Previous laboratory studies on the effects of storm surges and waves on coastal structures have typically utilized steady water levels and constant wave elements. An indoor simulation of the coupled processes of tides and waves is developed by adding a tide generation system to an existing laboratory wave basin to model continuous dynamic tide levels so that tide generation and wave-making occur synchronously in the pool. Specific experimental methods are given, which are applied to further study waves overtopping on artificial sea dikes and coastal flooding evolution under the coupled actions of tides and waves. The results of the overtopping discharge obtained by the test with a dynamic water level are compared with those obtained from steady water level tests and the existing empirical formula. In addition, the impacts of ecological coastal shelterbelts and structures on coastal flood processes and distributions are also investigated. The proposed simulation methods provide a new approach for studying the effects of storm surges and waves on coastal areas. The study also aims to provide a reference for coastal protective engineering.