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21.
Pedro N. Carvalho Pedro Nuno R. RodriguesRafael Evangelista M. Clara P. BastoM. Teresa S.D. Vasconcelos 《Estuarine, Coastal and Shelf Science》2011
Sediments are depositories of toxic substances such as organochlorine pesticides and there is a global need for their removal in contaminated environments. Studies that combine contaminated sediments and phytoremediation are relatively recent and their number has been increasing. This work aimed to investigate whether salt marsh plants (sea club-rush Scirpus maritimus, sea rush Juncus maritimus and sea purslane Halimione portulacoides) can favor DDT and metabolites remediation in estuarine environment. For this purpose the levels of DDT, DDE and DDD were compared in vegetated and non-vegetated sediments from an estuary in the North of Portugal (in-situ study) and from another in the South of Portugal (ex-situ study). Results obtained both in the in-situ study, involving S. maritimus and J. maritimus, and in the ex-situ study, involving H. portulacoides, indicated that these plants did not have a significant role in DDTs removal and/or degradation. Therefore, it seems that the tested plants cannot influence levels and distribution of DDTs in estuarine areas. 相似文献
22.
Microbes are ubiquitous in groundwater systems, and they play an important role in the redox state of groundwater and especially
on the fate of organic contaminants. In this context, numerical simulations that couple microbial processes to reactive transport
models are becoming more popular. In the present work, we revisit the mathematical ground of microbial redox reactions and
perform a benchmark analysis of the simulation of aerobic benzene degradation in a shallow and oxidizing aquifer. Numerical
results indicate that the two codes tested (one using the finite elements approach and the other using the finite differences
approach) lead to very similar results. In addition, the coupling of heterogeneous geochemical reactions to the benchmarked
example problem provides a solid basis for the understanding of the redox reactions and the changes on the carbon system triggered
by the aerobic degradation of benzene. 相似文献
23.
Aspects of sea-bed structure and benthic-macroinvertebrate species composition, distribution, richness and diversity in coastal waters off eastern Waiheke Island, Hauraki Gulf, are reported. In contrast to the sole historical account of sea-bed community structure from this same region, no widely distributed assemblages of species are recognised throughout it; no two sites share the exact same complement of species; and almost all sites are less than 80% similar in their taxonomic composition, most considerably so. Species richness and diversity are reported to vary with substratum type and depth, and spatially; species occurring within muds are the least diverse and species rich, followed by those of muddy gravels, and then gravels; many taxa prove common to the three substratum types; and dominance of taxa is recognised to decrease with an increase in substratum complexity, from muds to gravels, and species richness. With the exception of invasive marine species, apparent changes in the composition of assemblages throughout this region over the eight-decade period that data span are considered artefacts of the way in which such assemblages were historically defined. We recommend historical accounts of sea-bed community distributions throughout Hauraki Gulf be interpreted with caution, especially when attempting to use such schematic depictions to determine whether changes have occurred in assemblage composition. 相似文献
24.
An assessment and interpretation of the observed warming of West Antarctica in the austral spring 总被引：1，自引：1，他引：0
We synthesize variability and trends in multiple analyses of Antarctic near-surface temperature representing several independent source datasets and spatially complete reconstructions, and place these into the broader context of the behavior of other components of the climate system during the past 30–50?years. Along with an annual-mean trend during the past 50?years of about 0.1°C/decade averaged over Antarctica, there is a distinct seasonality to the trends, with insignificant change (and even some cooling) in austral summer and autumn in East Antarctica, contrasting with warming in austral winter and spring. Apart from the Peninsula, the seasonal warming is largest and most significant in West Antarctica in the austral spring since the late 1970s. Concurrent trends in sea ice are independent evidence of the observed warming over West Antarctic, with the decrease in sea ice area in the Amundsen and Bellingshausen Seas congruent with at least 50% of the inland warming of West Antarctica. Trends in near surface winds and geopotential heights over the high-latitude South Pacific are consistent with a role for atmospheric forcing of the sea ice and air temperature anomalies. Most of the circulation trend projects onto the two Pacific South American (PSA) modes of atmospheric circulation variability, while the Southern Annular Mode lacks a positive trend in spring that would otherwise cause a cooling tendency. The largest circulation trend is associated with the PSA-1 mode, a wave-train extending from the tropics to the high Southern latitudes. The PSA-1 mode is significantly correlated with SSTs in the southwestern tropical and subtropical Pacific. The increased SSTs in this region, together with the observed increase in rainfall, suggest that anomalous deep convection has strengthened or increased the occurrence of the Rossby wave-train associated with PSA-1. This hypothesis is supported by results from two ensembles of SST-forced atmospheric general circulation model simulations. Finally, the implications of the seasonality, timing, and spatial patterns of Antarctic temperature trends with respect to interpreting the relative roles of stratospheric ozone depletion, SSTs and increased atmospheric concentrations of greenhouse gasses are discussed. 相似文献
25.
Conrad S. Chapman Gabriele Capodaglio Clara Turetta Constant M.G. van den Berg 《Marine environmental research》2009,67(1):17-24
Benthic fluxes of copper, copper complexing ligands and thiol compounds in the shallow waters of Venice Lagoon (Italy) were determined using benthic chambers and compared to porewater concentrations to confirm their origin. Benthic copper fluxes were small due to small concentration differences between the porewaters and the overlying water, and the equilibrium concentration was the same at both sites, suggesting that the sediments acted to buffer the copper concentration. Thiol fluxes were ～10 × greater at 50–60 pmol cm?2 h?1, at the two sites. Porewater measurements demonstrated that the sediments were an important source of the thiols to the overlying waters. The overlying waters were found to contain at least two ligands, a strong one, L1 (log K′CuL1 = 14.2) and a weaker one, L2 (log K′CuL2 = 12.5). The concentration of L1 remained relatively constant during the incubation and similar to that of copper, whereas that of L2 was in great excess of copper, its concentration balanced by porewater releases and breakdown, probably due to uptake by microorganisms, similar to that of the thiol compounds. Similarity of the thiol and L2 concentrations and similar complex stability with copper suggest that L2 was dominated by the thiols. The free copper concentration ([Cu´]) in the Lagoon waters was lowered by a factor of 105 as a result of the organic complexation. 相似文献
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27.
Clara Mangili Achim Brauer Birgit Plessen Peter Dulski Andrea Moscariello Rudolf Naumann 《第四纪科学杂志》2010,25(2):135-145
Contamination with detrital matter is a well‐known bias in δ18O records from lake carbonates but quantitative information of this effect is yet lacking. Therefore, we developed a new methodological approach combining isotope analyses with microfacies, X‐ray diffraction and micro‐X‐ray fluorescence data and applied this in a case study for the Piànico interglacial lake record in order to provide a quantitative estimate of the effect of detrital carbonate on stable δ18O and δ13C data. The Piànico record contains a long series of distinct and well‐preserved calcite varves and is correlated to Marine Isotope Stage 11. Intercalated in the varve sequence are detrital layers triggered by surface erosion events. These detrital layers are mainly composed of dolomite, thus reflecting the mineralogical signature of the catchment. Microfacies analyses of a 9350 varve year interval allows the identification of detrital layers down to sub‐millimetre scale and a precise selection of three different types of samples for isotope analyses: (1) pure endogenic calcite varves (five varves per sample) without detrital contamination; (2) individual detrital layers; and (3) ‘mixed’ samples including five calcite varves and up to four thin detrital layers. Detrital samples show the isotopic signature of the catchment dolomite and are up to 5.7‰ enriched in δ18O values with respect to endogenic calcite samples. In mixed samples, the degree of isotopic enrichment is directly related to the amount of detrital contamination; δ18O of bulk carbonates is significantly biased when the detrital component amounts to more than 5% of the sample. It is also shown that samples containing detrital material have an influence on the calculation of the covariance between δ13C and δ18O. Covariance is high (r = 0.76) when the correlation coefficient is calculated on the base of all samples, but absent (r = ?0.43) when samples containing detrital dolomite are excluded. It has been demonstrated that microfacies analysis is a quick tool to avoid or reduce detrital contamination in bulk carbonate samples during sample selection. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
28.
Juan Pablo Corella Achim Brauer Clara Mangili Valentí Rull Teresa Vegas‐Vilarrúbia Mario Morellón Blas L. Valero‐Garcés 《Quaternary Research》2012,78(2):323-332
The karstic Lake Montcortès sedimentary sequence spanning the last 1548 yr constitutes the first continuous, high-resolution, multi-proxy varved record in northern Spain. Sediments consist of biogenic varves composed of calcite, organic matter and detrital laminae and turbidite layers. Calcite layer thickness and internal sub-layering indicate changes in water temperature and seasonality whereas the frequency of detrital layers reflects rainfall variability. Higher temperatures occurred in Lake Montcortès in AD 555–738, 825–875, 1010–1322 and 1874–present. Lower temperatures and prolonged winter conditions were recorded in AD 1446–1598, 1663–1711 and 1759–1819. Extreme and multiple precipitation events dominated in AD 571–593, 848–922, 987–1086, 1168–1196, 1217–1249, 1444–1457, 1728–1741 and 1840–1875, indicating complex hydrological variability in NE Spain since AD 463. The sedimentary record of Lake Montcortès reveals a short-term relation between rainfall variability and the detrital influx, pronounced during extended periods of reduced anthropogenic influences. In pre-industrial times, during warm climate episodes, population and land use increased in the area. After the onset of the industrialization, the relationship between climate and human activities decoupled and population dynamics and landscape modifications were therefore mostly determined by socio‐economic factors. 相似文献
29.
Lindsey Jones Clara Champalle Sabrina Chesterman Laura Cramer Todd A. Crane 《Climate Policy》2013,13(5):551-572
We carry out a structured review of the peer-reviewed literature to assess the factors that constrain and enable the uptake of long-term climate information in a wide range of sectoral investment and planning decisions. Common applications of long-term climate information are shown to relate to urban planning and infrastructure, as well as flood and coastal management. Analysis of the identified literature highlights five categories of constraints: disconnection between users and producers of climate information, limitations of climate information, financial and technical constraints, political economy and institutional constraints and finally psycho-social constraints. Five categories of enablers to the uptake of long-term climate information in decision-making are also identified: collaboration and bridge work, increased accessibility of climate information, improvement in the underlying science, institutional reform and windows of opportunity for building trust.Policy relevanceOur review suggests that stand-alone interventions aimed at promoting the uptake of climate information into decision-making are unlikely to succeed without genuine and sustained relationships between producers and users. We also highlight that not every decision requires consideration of long-term climate information for successful outcomes to be achieved. This is particularly the case in the context of developing countries, where the immediacy of development challenges means that decision makers often prioritize short-term interventions. Care should therefore be taken to ensure that information is targeted towards investments and planning decisions that are relevant to longer-term timescales. 相似文献
30.
Besides the traditional post-separation residential arrangement in which the children live with the mother and have regular contact with the father, new arrangements have emerged and become more widespread in which parents strive for a more equal division of tasks. We used an explanatory mixed methods research design to enhance insight into the life course characteristics of separated parents involved in shared residence arrangements. Survey data derived from the Netherlands Kinship Panel Study (NKPS) and Divorce in the Netherlands 1998 were supplemented with information from in-depth interviews with NKPS respondents. We found that shared residence parents seem to be a typical modern category of separated parents with a specific set of characteristics. The distance between the residences of the ex-partners plays a crucial role in maintaining a shared residence arrangement. Highly educated, dual-career ex-couples, and those with high incomes are also more likely to be involved in a shared residence arrangement. Shared residence arrangements were more likely when the woman had a new partner, but less likely when the man had a new partner. Our findings on gender differences are in line with the idea that involvement in non-traditional residential arrangements is a sign of increased paternal involvement, but decreased maternal involvement, compared with the traditional arrangements. 相似文献