Tracking the sources and fate of nitrate pollution by combining hydrochemical and isotopic data with a statistical approach     

Christiaens  Louis  Orban  Philippe  Brouyère  Serge  Goderniaux  Pascal 《Hydrogeology Journal》2023,31(5):1271-1289

This study contributes to identifying and spatializing the different types of nitrate sources by combining hydrogeochemical and isotopic data with principal component analysis (PCA) and t-distributed stochastic neighbor embedding (t-SNE) multicriteria statistical methods. The methodology is applied to the strategic Mons Basin chalk aquifer (Belgium). The results are based on a whole dataset containing 72 water samples with analyses of the hydrogeochemical parameters (temperature, pH, electrical conductivity (EC), redox potential, dissolved O₂), alkalinity, total organic carbon (TOC), silica (SiO₂), major and minor ions (NO₃^–, NH⁴⁺, Ca²⁺, dissolved Fe and Mn, K⁺, Mg²⁺, Na⁺, Sr²⁺, Cl^–, F^–, SO₄^–_, B) and multiple stable isotope ratios (δ¹¹B, δ¹⁵N–NO₃^–, δ¹⁸O–NO₃^–). Compared to classical PCA, the recently developed t-SNE method, which considers nonlinear relationships between variables and preserves local-scale similarities in a low-dimensional space, showed much better performance in discriminating different groups of samples and related zones in the aquifer. t-SNE results combined with isotope ratios highlighted four zones in the aquifer (grouped as A–D) and the presence of denitrification fronts. Group A presents a manure signature (δ¹⁵N–NO₃^– – mean (μ) +12.78‰, standard deviation (σ) 6.48‰; δ¹¹B – μ 29.96‰, σ 6.91‰). Group B exhibits both manure and inorganic fertilizer signatures (δ¹⁵N–NO₃^– – μ 6.27‰, σ 2.55‰; δ¹¹B – μ 15.86‰, σ 9.69‰). Group C shows a contamination by sewage (δ¹⁵N–NO₃^– – μ 12.67‰, σ 5.60‰; δ¹¹B – μ 9.97‰, σ 7.08‰). Group D presents a mixed signature (δ¹⁵N–NO₃^– – μ 9.25‰, σ 2.94‰; δ¹¹B – μ 20.00‰, σ 6.70‰).

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Shifting zonal patterns of the southern boreal forest in eastern Canada associated with changing fire regime during the Holocene     

Guillaume de Lafontaine  Serge Payette 《Quaternary Science Reviews》2011,30(7-8):867-875

This research aims at uncovering the stand-scale Holocene fire history of balsam fir forest stands from two bioclimatic zones of the boreal forest and assessing the existence of a sub-continental shift in past fire activity that could have triggered a change in the Holocene zonal pattern. In eastern Canada, the extant closed-crown boreal forest corresponds to two ecological regions separated along 49°N, the northern black spruce zone and the southern balsam fir zone. We sampled balsam fir stands from the southern fir zone (n = 7) and among the northernmost patches of fir forest located far beyond the fir zone boundary, into the spruce zone (n = 6). Macrofossil analysis of charcoal in mineral soils was used to reconstruct both the stand-scale and regional Holocene fire histories. Data were interpreted in the context of published palaeoecological evidence. Stands of the balsam fir zone were submitted to recurrent fire disturbances between c. 9000 and 5000 cal. yr B.P. Local fire histories suggested that four sites within the fir zone escaped fire during the Holocene. Such fire protected sites allowed the continuous maintenance of the balsam fir forest in the southern boreal landscape. Stands of the spruce zone have been affected by recurrent fires from 5000 cal. yr B.P. to present. Local fire histories indicated that no site escaped fire in this zone. Published palaeoecological data suggested that balsam fir migrated to its current northern limit sometime between 7300 and 6200 cal. yr B.P. A change of the fire regime 5000 years ago caused the regional decline of an historical northern balsam fir forest and its replacement by black spruce forest. The consequence was a sub-continental reshuffling of the fir and spruce zones within the closed-crown boreal forest. The macrofossil analysis of charcoal in mineral soils was instrumental to the reconstruction of stand-scale Holocene fire history at sites where no other in situ fire proxies were available.  相似文献   

A conceptual framework for the integral management of marine protected areas     

Celia Ojeda-Martínez  Francisca Giménez Casalduero  Just T. Bayle-Sempere  Carmen Barbera Cebrián  Carlos Valle  Jose Luis Sanchez-Lizaso  Aitor Forcada  Pablo Sanchez-Jerez  Pablo Martín-Sosa  Jesús M. Falcón  Fuensanta Salas  Mariagrazia Graziano  Renato Chemello  Ben Stobart  Pedro Cartagena  Angel Pérez-Ruzafa  Fréderic Vandeperre  Elisabeth Rochel  Serge Planes  Alberto Brito 《Ocean & Coastal Management》2009,52(2):89-101

A general conceptual framework for the management of marine protected areas (MPAs) was developed. The driver-pressure-state-impacts-response (DPSIR) framework was used to determine the elements affecting MPAs. The developed evaluation framework helped to select an appropriate suite of indicators to support an ecosystem approach, an assessment of the MPAs functioning and policy decisions. Gaps derived from the management and policy responses in the MPAs were also outlined. It was concluded that the DPSIR framework can help to simplify the complexity of MPA management. This document is a tool for policy makers, scientists and general public on the relevance of indicators to monitor changes and MPAs management.  相似文献   

Vertical distribution of dissolved aluminium in the mediterranean sea     

Serge Caschetto  Roland Wollast 《Marine Chemistry》1979,7(2):141-155

The vertical distribution of dissolved aluminium in the Mediterranean Sea offshore of Corsica has been followed during a period of high biological activity (April–September). In May and August, the concentration of dissolved aluminium is at a relatively low (1.5 μg Al1^?1) and rather constant value in the surface waters, while exhibiting minimum values of about 0.5 and 0.8 μg Al1^?1 in April and September. It increases under the seasonal thermocline to a depth of 150–500 m. The bottom waters are characterized by a constant and relatively high value of 4 μg Al1^?1.The observed concentrations of dissolved aluminium are not compatible with a precipitation-dissolution mechanism of clay minerals.The general distribution pattern and the seasonal changes of dissolved aluminium exhibit strong analogies with those of dissolved silica and nitrogen, suggesting a pre-dominant role of biological activity. It is not possible at this stage to attribute the aluminium uptake in the photic zone solely to the activity of diatoms, as suggested earlier.  相似文献   

Role of suspended sediments on the distribution of PCB in the Seine Estuary (France)     

Alain Abarnou  Jacques Avoine  Jean Paul Dupont  Robert Lafite  Serge Simon 《Continental Shelf Research》1987,7(11-12)

PCB (polychlorinated biphenyls) contamination and its relationship to SPM (suspended particulate material) have been studied in the Seine Estuary, which is heavily polluted by these persistent and hydrophobic man-made chemicals. Two sampling cruises have been performed during different freshwater discharge conditions. PCB and SPM concentrations, as well as grain-size distributions in the particulate material have been determined. Water samples have been collected at fixed positions during a tidal cycle, and along transects within the estuary.PCB concentrations vary from 2 ng 1⁻¹ in the marine zone to 250 ng 1⁻¹ within the estuary, and reach 1.3 × 10³ ng 1⁻¹ in the turbidity maximum zone. During a tidal cycle, low PCB concentrations are observed at high water, and are in the same range in February as in July. High PCB contamination is observed at low water, but PCB concentrations are about five times higher in February. SPM and PCB variations are well correlated in both periods of observations. Higher PCB contamination during February is explained by higher SPM inputs, mainly due to particles of riverine origin. The transport of PCB within the estuary depends on the quantity and the grainsize composition of suspended material, which varies according to freshwater discharge and tidal amplitude.  相似文献   

Downstream migration of juvenile European sturgeonAcipenser sturio L. in the Gironde estuary     

Eric Rochard  Mario Lepage  Pierre Dumont  Serge Tremblay  Christine Gazeau 《Estuaries and Coasts》2001,24(1):108-115

The European sturgeon (Acipenser sturio) is an endangered diadromous fish species that spawns in the rivers in late spring and early summer. The juveniles spend their first years in the brackish waters (5‰ to 25‰) of the estuary zone before moving out to sea. This study describes the downstream migration pattern of juvenile sturgeon, belonging to the 1994 cohort, the only one born naturally in the Gironde basin, France since the end of the 1980s. During October 1994 to December 1996 the inland section of the Gironde estuary was sampled monthly by trawl (n=818 tows) and all European sturgeon caught (n=381) were marked and released. The first sturgeon of the 1994 cohort (TL=27 cm) were caught in early March 1995 in the zones furthest upstream. During their second fall of life, juveniles gradually acclimatized, and spread over a wide range of salinity conditions. A first incursion into marine water was also observed (at least for a few fish) by the end of the second winter. During this second period, sturgeon showed preference for two particular zones situated at 18 and 38 km, respectively, from the mouth of the estuary. These zones, belonging to two different salinity sectors of the estuary, did not appear to be any different to their neighbors with regards to depth and type of substrate. There were no significant size differences among estuarine zones. Seasonal movements of sturgeon seem to be motivated by a search for warmer temperatures. After a period of early acclimatization of 15 months, juvenile European sturgeon appear to be highly tolerant of salinity variations.  相似文献   

From oblique subduction to intra-continental transpression: Structures of the southern Kermadec-Hikurangi margin from multibeam bathymetry,side-scan sonar and seismic reflection     

Jean-Yves Collot  Jean Delteil  Keith B. Lewis  Bryan Davy  Geoffroy Lamarche  Jean-Christophe Audru  Phil Barnes  Franck Chanier  Eric Chaumillon  Serge Lallemand  Bernard Mercier de Lepinay  Alan Orpin  Bernard Pelletier  Marc Sosson  Bertrand Toussaint  Chris Uruski 《Marine Geophysical Researches》1996,18(2-4):357-381

The southern Kermadec-Hikurangi convergent margin, east of New Zealand, accommodates the oblique subduction of the oceanic Hikurangi Plateau at rates of 4–5 cm/yr. Swath bathymetry and sidescan data, together with seismic reflection and geopotential data obtained during the GEODYNZ-SUD cruise, showed major changes in tectonic style along the margin. The changes reflect the size and abundance of seamounts on the subducting plateau, the presence and thickness of trench-fill turbidites, and the change to increasing obliquity and intracontinental transpression towards the south. In this paper, we provide evidence that faulting with a significant strike-slip component is widespread along the entire 1000 km margin. Subduction of the northeastern scrap of the Hikurangi Plateau is marked by an offset in the Kermadec Trench and adjacent margin, and by a major NW-trending tear fault in the scarp. To the south, the southern Kermadec Trench is devoid of turbidite fill and the adjacent margin is characterized by an up to 1200 m high scarp that locally separates apparent clockwise rotated blocks on the upper slope from strike-slip faults and mass wasting on the lower slope. The northern Hikurangi Trough has at least 1 km of trench-fill but its adjacent margin is characterized by tectonic erosion. The toe of the margin is indented by 10–25 km for more than 200 km, and this is inferred to be the result of repeated impacts of the large seamounts that are abundant on the northern Hikurangi Plateau. The two most recent impacts have left major indentations in the margin. The central Hikurangi margin is characterized by development of a wide accretionary wedge on the lower slope, and by transpression of presubduction passive margin sediments on the upper slope. Shortening across the wedge together with a component of strike-slip motion on the upper slope supports an interpretation of some strain partitioning. The southern Hikurangi margin is a narrow, mainly compressive belt along a very oblique, apparently locked subduction zone.  相似文献   

Photochemincal processes involving nitrite in surface water samples     

Claudio Minero  Serge Chiron  Gianpaolo Falletti  Valter Maurino  Ezio Pelizzetti  Roberto Ajassa  Maria Eugenia Carlotti  Davide Vione 《Aquatic Sciences - Research Across Boundaries》2007,69(1):71-85

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Holocene occurrence of Lophodermium piceae, a black spruce needle endophyte and possible paleoindicator of boreal forest health     

J.P. Paul Jasinski  Serge Payette 《Quaternary Research》2007,67(1):50-56

Holocene occurrences of conifer needle endophytes have not previously been reported. We report the fossil remains of Lophodermium piceae (Fckl.) Hoehn., a fungal endophyte of black spruce (Picea mariana (Mill.) B.S.P.) needles, in macrofossils dating back to 8000 cal yr BP. Spruce budworm head capsules and L. piceae remains were found preceding charcoal layers delineating the transformation of four spruce−moss forest sites to spruce−lichen woodland. As L. piceae is found solely on senescent needles, its increased presence during these transformation periods likely indicates that the forests were in decline due to the spruce budworm (Choristoneura fumiferana (Clem.)) when they burned. Future paleoecological studies incorporating needle fungi observations could be used to investigate the historical occurrence of tree disease and the role of fungi in forest health and decline.  相似文献   

News from the AAS     

Jacqueline Mitton 《Astronomy& Geophysics》2003,44(2):2.18-2.19

Jacqueline Mitton reports on science highlights from the 201st meeting of the American Astronomical Society.  相似文献