Sediments from stormdrain catchments and outlets in Wellington city and sediment traps from Wellington Harbour were sampled
for trace metal content. Samples were analysed for total metal content using XRF and ICP-MS. High values of Pb and Zn were
found in stormdrain catchments and outlets, decreasing to elevated background rock levels in the harbour. Maximum values were
recorded in an inner city stormdrain catchment, with levels of Pb (4605 ppm), Cu (2981 ppm) and Zn (3572 ppm) all higher than
the biological probable effects levels (PEL). Concentrations of As, Cr, Cu, Pb, Ni and Zn concentrations in all harbour sediment
trap samples were below the PEL. The mean values for each harbour sediment trap sample can be used as an accurate historical
baseline in future studies. Stormdrain samples with high trace metal levels were close to industrial and construction sites.
The proximity of these outlets to recreational areas should be of concern to local authorities.
Received: 28 August 1997 · Accepted: 15 December 1997 相似文献
During 1979–2015, the intensity of the Siberian high(SH) in November and December–January(DJ) is frequently shown to have an out-of-phase relationship, which is accompanied by opposite surface air temperature and circulation anomalies.Further analyses indicate that the autumn Arctic sea ice is important for the phase reversal of the SH. There is a significantly positive(negative) correlation between the November(DJ) SH and the September sea ice area(SIA) anomalies. It is suggested that the reduction of autumn SIA induces anomalous upward surface turbulent heat flux(SHF), which can persist into November, especially over the Barents Sea. Consequently, the enhanced eddy energy and wave activity flux are transported to mid and high latitudes. This will then benefit the development of the storm track in northeastern Europe. Conversely, when downward SHF anomalies prevail in DJ, the decreased heat flux and suppressed eddy energy hinder the growth of the storm track during DJ over the Barents Sea and Europe. Through the eddy–mean flow interaction, the strengthened(weakened)storm track activities induce decreased(increased) Ural blockings and accelerated(decelerated) westerlies, which makes the cold air from the Arctic inhibited(transported) over the Siberian area. Therefore, a weaker(stronger) SH in November(DJ) occurs downstream. Moreover, anomalously large snowfall may intensify the SH in DJ rather than in November. The ensemble-mean results from the CMIP5 historical simulations further confirm these connections. The different responses to Arctic sea ice anomalies in early and middle winter set this study apart from earlier ones. 相似文献
The annual cycle of the thickness and temperature of landfast sea ice in the East Siberian Sea has been examined using a one-dimensional thermodynamic model. The model was calibrated for the year Augus... 相似文献
We present a summary of late Paleoproterozoic to Neoproterozoic mafic magmatism in the Siberian craton, including recently published U–Pb and 40Ar–39Ar dates. These new precise ages suggest that at least some of the previously published K–Ar ages of Siberian mafic bodies should be ignored. The time–space geochronological chart, or the ‘barcode’ of mafic magmatic events shows significant differences between northern and southern Siberia. Both are characterized by ∼1900–1700 Ma magmatic events, but then there was an almost 1 Ga mafic magmatic ‘pause’ in south Siberia until ∼800 Ma. Meanwhile there are indications of multiple mafic magmatic events in North Siberia (Anabar shield and Olenek uplift) between ∼1600 and 1000 Ma. A series of magmatic events probably related to the breakup of Rodinia occurred in southern Siberia after ∼800 Ma. So far, there are no indications of late Neoproterozoic mafic magmatism in North Siberia. Ca. 1000–950 Ma mafic sills were reported from Meso- to Neo-Proterozoic sedimentary successions in the Sette-Daban area on the east side of the Siberian craton, but their tectonic setting is debated. Recent Ar–Ar dates of ∼1750 Ma for NW-trending dykes in the Aldan and Anabar shields, together with similar-age NNE-trending Baikal uplift dykes in south-eastern Siberia suggest the existence of a giant radial dyke swarm possibly related to a mantle plume centred in the Vilyui River area. 相似文献
The seasonal sedimentation pattern of diatom valves in Lake Holzmaar was investigated during 1995 by deploying sediment traps at three different lake depths. According to the sedimentation pattern, the major reproduction zone of diatoms was restricted to the upper 6 m of the water body. The population growth started late in April and blooms of Cyclotella cf. comensis Grun., which dominates the plankton diatoms, and Fragilaria crotonensis Kitton were collected in traps during June and September, and July, respectively. During summer, the seasonal sedimentation pattern of each taxon, as collected in the upper traps, was reflected in the concentrations in the lowest trap. However, in May and from September onwards, the community composition in the lowest trap and augmented trapping rates suggest both sediment focusing and resuspension of bottom sediments.The temperature signals as recorded by 18O values of diatom valves should, therefore, reflect integrated temperatures between 0 and 6 m depth. However, temperatures during summer and autumn are expected to be accentuated in the sedimentary record since the isotopic signal is weighted by both the number and the weight-mass of the valves. During summer, the transfer of these signals by the sedimenting diatoms retains the information pattern recorded, while in spring and autumn/winter additional influxes caused by resuspension may somewhat alter those temperature informations. The proxy signals finally stored in the sediments, may, therefore, not precisely represent the successive temperatures currently recorded during 1995 within mid-lake. 相似文献
Sediment traps were deployed in the Gulf of Papua in June–July 1997, to determine fluxes of organic matter and inorganic elements from the photic zone to deeper waters at the base of the continental slope and in the northern Coral Sea. Three stations, ranging from 900 to 1500 m depth, had “shallow” traps at 300 m below the water surface and “deep” traps set 100 m above the bottom. Infiltrex II water samplers collected particulate and dissolved organic matter from the Fly, Purari and Kikori rivers, and near-surface water from the shelf of the Gulf of Papua. Samples were analysed for molecular organic biomarkers to estimate the sources of organic carbon and its cycling processes.Dry weight fluxes from the shallow traps ranged from 115 to 181 mg m−2 day−1 and particulate organic carbon (POC) fluxes ranged from 1.2 to 1.9 mM OC m−2 d−1 with molar organic carbon to particulate nitrogen ratios (C/N) ranging from 6.0 to 6.5. Fluxes in deep traps were likely influenced by both early diagenesis and entrapment of resuspended shelf sediments. Dry weight fluxes in deep traps ranged from 106 to 574 mg m−2 day−1 and POC fluxes ranged from 0.6 to 1.5 mM OC m−2 d−1, with C/N ratios ranging from 8.5 to 10.8. 13C/12C ratios were −20.2‰ to −21.7‰ in all trap samples, indicating that most of the settling POC was “marine-derived”. Shallow traps had δ15N values of 6.3‰ to 7.2‰ while the values in deep traps were 4.9–5.0‰, indicating the N-rich near-surface OC was less degraded than that in the deep traps. The biogenic lipids consisted of hydrocarbon, sterol and fatty acid biomarkers indicative of marine zooplankton, phytoplankton and bacteria. Sterol markers for diatoms and dinoflagellates were abundant in the water samples. Highly branched isoprenoid alkenes, usually attributable to diatoms, were also detected in both water and shallow traps. Traces of C26–C34n-alcohols indicative of land–plant biomarkers, were found in river water samples and in the shallow sediment traps. A large unresolved complex mixture (UCM) of hydrocarbons, and a uniform distribution of n-alkanes, indicative of petroleum hydrocarbons, were also detected in the traps. Hopane and sterane biomarkers detected in the trap oil were characteristic of a marine carbonate source, and the aromatic hydrocarbon composition distinguished at least two different oil signatures.We concluded that mass and POC fluxes were similar to those reported for other continental shelves and marginal oceans in tropical and subtropical regions. There was a dramatic decrease in POC as particles sank, due to zooplankton repackaging and photochemical and bacterial decomposition. Carbon isotopic and biomarker patterns showed most of the POC in the sediment traps was marine-sourced with only traces of terrestrial input. There was a significant flux of petroleum, which may signal the existence of natural petroleum seeps in this region. 相似文献
(1) A new method of sampling stygofauna is presented, along with some data derived from applications in the field. Numerous bores were sampled for fauna, water and bacteria, down to a depth of 7.50 m. Two or 3 unbaited traps were fixed to a central pole within the bore. The traps consist of an inert plastic chamber with holes in the upper parts and gaskets near the bottom and near the lid of each trap. The content of the traps was emptied monthly using a pump.
(2) While the taxonomic composition of the trap samples seemed to be comparable to the surrounding groundwater, estimation of abundances in the traps might differ, with a potential over-estimation in the traps, in particular in sparsely populated aquifers. Detailed comparative studies on the performance of the method are, as yet, lacking.
(3) Trap data of invertebrate communities reflect hydraulic changes, and highest abundances and taxa richness were found near the water table. They decreased rapidly with depth, implying that small-scale stratified sampling is possible.
(4) The technique is cheap, reliable, simple and rapid to use, and allows simultaneous sampling of hydro-chemical, faunal and microbial samples. The method seems to be suitable for a wide range of sub-surface waters, where the water table is shallower than 8 m.
George VI Ice Shelf is the largest ice shelf on the western side of the Antarctic Peninsula and its northern margin marks
the southern most latitudinal limit of recent ice shelf retreat. As part of a project to reconstruct the long-term (Holocene)
history of George VI Ice Shelf we studied two epishelf lakes impounded by the ice shelf at Ablation Point, on the east coast
of Alexander Island. These lakes, Moutonnée and Ablation, are stratified water bodies with a lower marine layer and an upper
freshwater layer. To determine if their sediment records could be used to detect past changes in the presence or absence of
the ice shelf it was necessary to describe their present-day limnology and sedimentology. We measured water column chemistry
and sampled the water column and sediments of the lakes along vertical and horizontal transects. We analysed these samples
for diatoms, stable isotopes (δ18O, δ2H, δ13CDIC, δ13Corg), geochemistry (TOC, TN, C/N ratios) and physical sedimentology (grain-size). This was supplemented by chemical and biological
reference data from the catchments. Results showed that the water columns of both lakes are nutrient limited and deficient
in phytoplankton. Benthic productivity is low and decreases with depth. Comparison of water column chemistry with an earlier
survey shows a net increase in the thickness of the freshwater layer in Moutonnée Lake between 1973 and 2001, which could
indicate that George VI Ice Shelf has thinned during this period. However, a similar trend was not observed in Ablation Lake
(5 km to the north) and an alternative explanation is that the changes are a seasonal phenomena. Data from the surface sediment
transects identified a number of proxies that respond to the present day stratification of the water column including diatom
species composition, stable isotopes and geochemistry, particularly in Moutonnée Lake. Collectively these data have been used
to develop a conceptual model for determining past ice shelf configuration in epishelf lakes. Specifically, periods of past
ice shelf loss, and the removal of the ice dam, would see the present stratified epishelf lake replaced by a marine embayment.
It is suggested that this change would leave a clear signature in the lake sediment record, notably the deposition of an exclusively
marine biological assemblage, increased ice rafted debris and δ13Corg values that are indicative of marine derived organic matter.
These authors contributed equally to this work 相似文献