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971.
972.
973.
Jesús Carrera Juan J. Hidalgo Luit J. Slooten Enric Vázquez-Suñé 《Hydrogeology Journal》2010,18(1):131-145
The inverse problem of seawater intrusion (SWI) is reviewed. It represents a challenge because of both conceptual and computational difficulties and because coastal aquifer models display many singularities: (1) head measurements need to be complemented with density information; (2) salinity concentration data are very sensitive to flow within the borehole. Data problems can be reduced by incorporating the measurement process within model calibration; (3) SWI models are extremely sensitive to aquifer bottom topography; (4) the initial conditions may be far from steady state and depend on the location and type of sea-aquifer connection. Problems with aquifer geometry and initial conditions can be addressed by parameterization, which allows for modification during inversion. The four sets of difficulties can be partly overcome by using tidal response and electrical conductivity data, which are highly informative and provide extensive coverage. Still, SWI inversion is extremely demanding from a computation point of view. Computational improvements are discussed. 相似文献
974.
Edward Castañeda-Moya Robert R. Twilley Victor H. Rivera-Monroy Keqi Zhang Stephen E. DavisIII Michael Ross 《Estuaries and Coasts》2010,33(1):45-58
The distribution of mangrove biomass and forest structure along Shark River estuary in the Florida Coastal Everglades (FCE)
has been correlated with elevated total phosphorus concentration in soils thought to be associated with storm events. The
passage of Hurricane Wilma across Shark River estuary in 2005 allowed us to quantify sediment deposition and nutrient inputs
in FCE mangrove forests associated with this storm event and to evaluate whether these pulsing events are sufficient to regulate
nutrient biogeochemistry in mangrove forests of south Florida. We sampled the spatial pattern of sediment deposits and their
chemical properties in mangrove forests along FCE sites in December 2005 and October 2006. The thickness (0.5 to 4.5 cm) of
hurricane sediment deposits decreased with distance inland at each site. Bulk density, organic matter content, total nitrogen
(N) and phosphorus (P) concentrations, and inorganic and organic P pools of hurricane sediment deposits differed from surface
(0–10 cm) mangrove soils at each site. Vertical accretion resulting from this hurricane event was eight to 17 times greater
than the annual accretion rate (0.30 ± 0.03 cm year−1) averaged over the last 50 years. Total P inputs from storm-derived sediments were equivalent to twice the average surface
soil nutrient P density (0.19 mg cm−3). In contrast, total N inputs contributed 0.8 times the average soil nutrient N density (2.8 mg cm−3). Allochthonous mineral inputs from Hurricane Wilma represent a significant source of sediment to soil vertical accretion
rates and nutrient resources in mangroves of southwestern Everglades. The gradient in total P deposition to mangrove soils
from west to east direction across the FCE associated with this storm event is particularly significant to forest development
due to the P-limited condition of this carbonate ecosystem. This source of P may be an important adaptation of mangrove forests
in the Caribbean region to projected impacts of sea-level rise. 相似文献
975.
Phytoplankton seasonal and interannual variability in the Guadiana upper estuary was analyzed during 1996–2005, a period that
encompassed a climatic controlled reduction in river flow that was superimposed on the construction of a dam. Phytoplankton
seasonal patterns revealed an alternation between a persistent light limitation and episodic nutrient limitation. Phytoplankton
succession, with early spring diatom blooms and summer–early fall cyanobacterial blooms, was apparently driven by changes
in nutrients, water temperature, and turbulence, clearly demonstrating the role of river flow and climate variability. Light
intensity in the mixed layer was a prevalent driver of phytoplankton interannual variability, and the increased turbidity
caused by the Alqueva dam construction was linked to pronounced decreases in chlorophyll a concentration, particularly at the start and end of the phytoplankton growing period. Decreases in annual maximum and average
abundances of diatoms, green algae, and cyanobacteria were also detected. Furthermore, chlorophyll a decreases after dam filling and a decrease in turbidity may point to a shift from light limitation towards a more nutrient-limited
mode in the near future. 相似文献
976.
Contribution of a sewage sludge application to the short-term carbon sequestration across a wide range of agricultural soils 总被引:1,自引:0,他引:1
José Martín Soriano-Disla J. Navarro-Pedreño I. Gómez 《Environmental Earth Sciences》2010,61(8):1613-1619
The atmospheric levels of carbon dioxide (CO2) and other greenhouse gases (GHGs) have increased dramatically since the industrial revolution. The atmospheric enrichment
with CO2 and other GHGs has resulted in multiple negative consequences: such as the increase in the average temperature and the rise
of the sea level. Hence, there is a growing interest in developing feasible methods to reduce the atmospheric levels of these
gases. One of these strategies is to enhance C sequestration through the increase of soil organic carbon (SOC) pool by the
amendment of agricultural soils with sewage sludge. However, there is considerable uncertainty about the effects (positive
or negative) of sewage sludge applications on the SOC pool. Thus, a simple approach developed under laboratory conditions
is presented to discern the effect of a single sewage sludge application of 50 t ha−1 on the short-term SOC pool in 60 contrasting agricultural soils. The role of soil factors in the C sequestration of the recently
added carbon was also studied. The application of sewage sludge supposed a mean increase of 1.7 ± 1.6 g SOC kg−1, with peak increases of up to 3.8 g SOC kg−1 and decreases of up to 4.6 g SOC kg−1. The initial SOC contents conditioned the C sequestration after sewage sludge application, and no other soil property was
related. 相似文献
977.
Roberto Wagner Lourenço Paulo M. Barbosa Landim André Henrique Rosa José Arnaldo F. Roveda Antonio César Germano Martins Leonardo Fernandes Fraceto 《Environmental Earth Sciences》2010,60(3):495-504
Spatial analysis and fuzzy classification techniques were used to estimate the spatial distributions of heavy metals in soil.
The work was applied to soils in a coastal region that is characterized by intense urban occupation and large numbers of different
industries. Concentrations of heavy metals were determined using geostatistical techniques and classes of risk were defined
using fuzzy classification. The resulting prediction mappings identify the locations of high concentrations of Pb, Zn, Ni,
and Cu in topsoils of the study area. The maps show that areas of high pollution of Ni and Cu are located at the northeast,
where there is a predominance of industrial and agricultural activities; Pb and Zn also occur in high concentrations in the
northeast, but the maps also show significant concentrations of Pb and Zn in other areas, mainly in the central and southeastern
parts, where there are urban leisure activities and trade centers. Maps were also prepared showing levels of pollution risk.
These maps show that (1) Cu presents a large pollution risk in the north–northwest, midwest, and southeast sectors, (2) Pb
represents a moderate risk in most areas, (3) Zn generally exhibits low risk, and (4) Ni represents either low risk or no
risk in the studied area. This study shows that combining geostatistics with fuzzy theory can provide results that offer insight
into risk assessment for environmental pollution. 相似文献
978.
J. Dowgiałło 《Environmental Geology》2000,39(5):431-432
979.
980.
C.J. Van Meerbeeck H. Renssen D.M. Roche B. Wohlfarth S.J.P. Bohncke J.A.A. Bos S. Engels K.F. Helmens M.F. Sánchez-Goñi A. Svensson J. Vandenberghe 《Quaternary Science Reviews》2011,30(25-26):3618-3637
15 abrupt warming transitions perturbed glacial climate in Greenland during Marine Isotope Stage 3 (MIS 3, 60–27 ka BP). One hypothesis states that the 8–16 °C warming between Greenland Stadials (GS) and Interstadials (GI) was caused by enhanced heat transport to the North Atlantic region after a resumption of the Atlantic Meridional Overturning Circulation (AMOC) from a weak or shutdown stadial mode. This hypothesis also predicts warming over Europe, a prediction poorly constrained by data due to the paucity of well-dated quantitative temperature records. We therefore use a new evidence from biotic proxies and a climate model simulation to study the characteristics of a GS–GI transition in continental Europe and the link to enhanced AMOC strength. We compare reconstructed climatic and vegetation changes between a stadial and subsequent interstadial – correlated to GS15 and GI14 (~55 ka BP) – with a simulated AMOC resumption using a three-dimensional earth system model setup with early-MIS 3 boundary conditions. Over western Europe (12°W–15°E), we simulate twice the annual precipitation, a 17 °C warmer coldest month, a 8 °C warmer warmest month, 1300 °C-day more growing degree days with baseline 5 °C (GDD5) and potential vegetation allowing tree cover after the transition. However, the combined effect of frequent killing frosts, <20 mm summer precipitation and too few GDD5 after the transition suggest a northern tree limit lying at ~50°N during GI14. With these 3 climatic limiting factors we provide a possible explanation for the absence of forests north of 48°N during MIS 3 interstadials with mild summers. Finally, apart from a large model bias in warmest month surface air temperatures, our simulation is in reasonable agreement with reconstructed climatic and vegetation changes in Europe, thus further supporting the hypothesis. 相似文献