Environmental pollution in the Gulf of Guinea--a regional approach     

Scheren PA  Ibe AC  Janssen FJ  Lemmens AM 《Marine pollution bulletin》2002,44(7):633-641

Environmental pollution in the Gulf of Guinea (GOG) coastal zone has caused eutrophication and oxygen depletion in the lagoon systems, particularly around the urban centres, resulting in decreased fish (reproduction) levels and waterborne diseases. A pollution sources assessment was undertaken by six countries in the region as a first step in defining a region-wide Environmental Management Plan. Results show that households produce 90% of solid waste. Industry, however, is responsible for substantial amounts of hazardous waste, specifically the Nigerian petroleum industry. The latter is also responsible for the spilling of large amounts of oil. BOD load from industrial effluents is slightly larger than domestic loads in the industrialised coastal zone. Wastewater treatment systems are either absent or inadequate. Apart from large-scale gas flaring in Nigeria, air pollution, in terms of COx, HC, NOx and SO2 emissions, is contributed mainly by traffic. Particulates, originate mainly from industries and domestic biomass burning.  相似文献   

Environmental history of the south-eastern South Atlantic since the Middle Miocene: evidence from the sedimentological records of ODP Sites 1088 and 1092   总被引：1，自引：0，他引：1  

Bernhard Diekmann  Mareike Fälker†  Gerhard Kuhn† 《Sedimentology》2003,50(3):511-529

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Paleolimnological features of a mega-lake phase in the Makgadikgadi Basin (Kalahari,Botswana) during Marine Isotope Stage 5 inferred from diatoms     

Mareike Schmidt  Markus Fuchs  Andrew C. G. Henderson  Annette Kossler  Melanie J. Leng  Anson W. Mackay  Elisha Shemang  Frank Riedel 《Journal of Paleolimnology》2017,58(3):373-390

The Makgadikgadi–Okavango–Zambezi basin (MOZB) is a structural depression in the south-western branch of the East African Rift System of the northern and middle Kalahari, central southern Africa. In the present day, the mainly dry subbasins of the MOZB are part of a long-lived lacustrine system that has likely existed since Early Pleistocene and from which an extant freshwater fish radiation emerged seeding all major river systems of southern Africa. During hydrologically favourable periods the subbasins were connected as a single mega-lake termed Lake Palaeo-Makgadikgadi. Previous geomorphological studies and OSL dates have provided evidence for repeated mega-lake periods since approximately 300 ka. The environmental and climatic implications of such large scale late Quaternary lake-level fluctuations are controversial, with the duration of mega-lake phases poorly constrained. Here, we present the first evidence for a Marine Isotope Stage (MIS) 5 mega-lake period (about 935–940 m a.s.l.) reconstructed from a diatom-rich, 30-cm-thick lacustrine sediment section, exposed close to a palaeo-shoreline of the Makgadikgadi Basin. Based upon the environmental setting and in comparison with sedimentation rates of other similar lake environments, we tentatively estimated that the highstand lasted approximately 1 ka during MIS 5d–b. The 30-cm section was sampled in 0.5-cm steps. Diatom species diversity ranges from 19 to 30 through the section. The dominant species are Pseudostaurosira brevistriata, Rhopalodia gibberula, Cyclotella meneghiniana and Epithemia sorex. The total of 60 sediment samples provide us with a record at decadal to bi-decadal resolution. Based on diatom assemblages and their oxygen isotope composition (δ¹⁸O) we infer an alkaline and mostly oligohaline lake with shallow water conditions prevailing in MIS 5, and is potentially analogous to a Heinrich event. The climate over southern Africa during MIS 5 has been considered very arid but the hydromorphological context of our sediment section indicates that we captured a mega-lake period providing evidence that short-term excursions to significantly higher humidity existed. A hydrologically more favourable environment during MIS 5 than formerly presumed is in line with the early human occupation of the Kalahari.  相似文献   

Saturn's rings: 3-mm low-inclination observations and derived properties     

Eugene E. Epstein  Michael A. Janssen  Jeffrey N. Cuzzi 《Icarus》1984,58(3):403-411

Recent 3-mm observations of Saturn at low ring inclinations are combined with previous observations of E. E. Epstein, M. A. Janssen, J. N. Cuzzi, W. G. Fogarty, and J. Mottmann (Icarus41, 103–118) to determine a much more precise brightness temperature for Saturn's rings. Allowing for uncertainties in the optical depth and uniformity of the A and B rings and for ambiguities due to the C ring, but assuming the ring brightness to remain approximately constant with inclination, a mean brightness temperature for the A and B rings of 17 ± 4°K was determined. The portion of this brightness attributed to ring particle thermal emission is 11 ± 5°K. The disk temperature of Saturn without the rings would be 156 ± 6°K, relative to B. L. Ulich, J. H. Davis, P. J. Rhodes, and J. M. Hollis' (1980, IEEE Trans. Antennas Propag.AP-28, 367–376) absolutely calibrated disk temperature for Jupiter. Assuming that the ring particles are pure water ice, a simple slab emission model leads to an estimate of typical particle sizes of ≈0.3 m. A multiple-scattering model gives a ring particle effective isotropic single-scattering albedo of 0.85 ± 0.05. This albedo has been compared with theoretical Mie calculations of average albedo for various combinations of particle size distribution and refractive indices. If the maximum particle radius (≈5 m) deduced from Voyager bistatic radar observations (E. A. Marouf, G. L. Tyler, H. A. Zebker, V. R. Eshleman, 1983, Icarus54, 189–211) is correct, our results indicate either (a) a particle distribution between 1 cm and several meters radius of the form r^?s with 3.3 ? s ? 3.6, or (b) a material absorption coefficient between 3 and 10 times lower than that of pure water ice Ih at 85°K, or both. Merely decreasing the density of the ice Ih particles by increasing their porosity will not produce the observed particle albedo. The low ring brightness temperature allows an upper limit on the ring particle silicate content of ≈10% by mass if the rocky material is uniformly distributed; however, there could be considerably more silicate material if it is segregated from the icy material.  相似文献   

Euthecosomatous gastropods (Mollusca: Heterobranchia) from Buton (SE Sulawesi,Indonesia), with notes on species from Viti Levu,Fiji; systematics,biostratigraphy     

Janssen  A.W. 《Geologie en Mijnbouw》1999,78(2):179-189

Geologie en Mijnbouw - Pteropoda (Mollusca, Gastropoda, Euthecosomata) described by Beets (1943, 1950, 1953) from the alleged Late Miocene/Early Pliocene asphaltic deposits of Buton (SE Sulawesi,...  相似文献   

Multiproxy Analyses of Stratigraphy and Palaeoenvironment of the Late Palaeolithic Grabow Floodplain Site,Northern Germany     

Johann Friedrich Tolksdorf  Falko Turner  Knut Kaiser  Eileen Eckmeier  Mareike Stahlschmidt  Rupert A. Housley  Klaus Breest  Stephan Veil 《Geoarchaeology》2013,28(1):50-65

Changing river courses and fluctuations of the water table were some of the most fundamental environmental changes that humans faced during the Late Glacial, particularly as these changes affected areas intensively used for settlement and resource exploitation. Unfortunately, only a few stratigraphies have been documented in the North European plain that show the interaction between river development, vegetation history, and occupation by Late Palaeolithic humans. Here, we present the results of detailed stratigraphical studies (pedology, archaeology, chrono‐, tephra‐, and palynostratigraphy) at the Federmesser site Grabow 15 located in the broad Elbe River valley. The research aimed to produce a model of site formation based on a multiproxy approach, relating the local evidence to the palaeoenvironmental and settlement history of the wider region. After deposition of fluvial sands during the Late Pleniglacial in a braided setting, the river course developed locally toward a meandering system at the transition from the Older Dryas to the Allerød, while periodic flooding led to the deposition of floodplain sediments during the early Allerød. The floodplain was settled by people of the earliest “Federmessergruppen,” who are believed to have chosen this open floodplain area along the river for collecting and processing amber of local origin. Their artifacts became embedded in the aggrading floodplain sediments. In the late Allerød, floodplain sedimentation ceased and a Fluvisol‐type soil developed, indicating a trend toward geomorphic stability. The Fluvisol was then covered by silty floodplain sediments due to a rising water level during the late Younger Dryas resulting in the cessation of human occupation in the area. Subsequent organic‐rich Late Glacial/Holocene sediments preserved the settlement remains to the present.  相似文献   

New Cassini RADAR results for Saturn’s icy satellites     

S.J. Ostro  L.C. Wye  M.A. Janssen  K. Kelleher  R.A. Boehmer  Y. Gim  W.T.K. Johnson  R.D. Lorenz  the Cassini RADAR Team 《Icarus》2010,206(2):498-506

Cassini radar tracks on Saturn’s icy satellites through the end of the Prime Mission in 2008 have increased the number of radar albedo estimates from 10 (Ostro et al., 2006) to 73. The measurements sample diverse subradar locations (and for Dione, Rhea, and Iapetus almost always use beamwidths less than half the target angular diameters), thereby constraining the satellites’ global radar albedo distributions. The echoes result predominantly from volume scattering, and their strength is thus strongly sensitive to ice purity and regolith maturity. The combination of the Cassini data set and Arecibo 13-cm observations of Enceladus, Tethys, Dione, Rhea (Black et al., 2007), and Iapetus (Black et al., 2004) discloses an unexpectedly complex pattern of 13-to-2-cm wavelength dependence. The 13-cm albedos are generally smaller than 2-cm albedos and lack the correlation seen between 2-cm and optical geometric albedos. Enceladus and Iapetus are the most interesting cases. We infer from hemispheric albedo variations that the E-ring has a prominent effect on the 13-cm radar “lightcurve”. The uppermost trailing-side regolith is too fresh for meteoroid bombardment to have developed larger-scale heterogeneities that would be necessary to elevate the 13-cm radar albedo, whereas all of Enceladus is clean and mature enough for the 2-cm albedo to be uniformly high. For, Iapetus, the 2-cm albedo is strongly correlated with optical albedo: low for the optically dark, leading-side material and high for the optically bright, trailing-side material. However, Iapetus’ 13-cm albedo values show no significant albedo dichotomy and are several times lower than 2-cm values, being indistinguishable from the weighted mean of 13-cm albedos for main-belt asteroids, 0.15 ± 0.10. The leading side’s optically dark contaminant must be present to depths of at least one to several decimeters, so 2-cm albedos can mimic the optical dichotomy; however, it does not have to extend any deeper than that. The fact that both hemispheres of Iapetus look Asteroid-like at 13 cm means that coherent backscattering itself is not nearly as effective as it is at 2 cm. Since Iapetus’ entire surface is mature regolith, the wavelength dependence must involve composition, not structure. Either the composition is a function of depth everywhere (with electrical loss much greater at depths greater than a decimeter or two), or the intrinsic electrical loss of some pervasive constituent is much higher at 13 cm than at 2 cm. Ammonia is a candidate for such a contaminant. If ammonia’s electrical properties do not depend on frequency, and if ammonia is globally much less abundant within the upper one or two decimeters than at greater depths, then coherent backscattering would effectively be shut down at 13 cm, explaining the Asteroid-like 13-cm albedo.  相似文献   

Innovating the IPCC review process—the potential of young talent     

Lianne van der Veer  Hans Visser  Arthur Petersen  Peter Janssen 《Climatic change》2014,125(2):137-148

There is significant potential in young talent for enhancing the credibility of the scientific assessments such as the IPCC’s by contributing to quality assurance and quality control. In this essay, we reflect on an experiment that was done by the Dutch government as part of its government review of a contribution to the IPCC’s Fifth Assessment Report (AR5). In an effort to review the entire Working Group II contribution to the AR5 within the official review period for the Second Order Draft (SOD), the PBL Netherlands Environmental Assessment Agency turned to PhD students. This article shows that a systematic review focusing on transparency and errors of a large scientific assessment document using young talented scientists can be successful if certain conditions are met. The reviewers need to have intrinsic motivation to conduct the review. There needs to be a communication plan that fosters engagement and a clear methodology to guide the reviewers through their task. Based on this experiment in review, we reflect on the wider potential for openness and crowdsourcing in scientific assessment processes such as the IPCC’s.  相似文献   

A note on wave-induced set-up by obliquely incident waves     

T.T. Janssen  I.S. Jones 《Coastal Engineering》2011

Water level variations due to obliquely incident, shoaling and breaking waves on a plane sloping beach were discussed recently by Hsu et al. (Coastal Engineering, 53, 865–877, 2006). An inconsistency in this work with respect to the set-down, and its implications to circulation offshore of the breakpoint, was pointed out by Shi and Kirby (Coastal Engineering, 55, 1246 – 1249, 2008). Here we extend that discussion to include the surfzone momentum balance and wave-induced set-up. We discuss some remaining inconsistencies in the approximation of the surfzone momentum balance, derive and present a consistent approximation, and validate the new approximation through numerical comparison to a more exact model.  相似文献   

SOVAP/Picard,a Spaceborne Radiometer to Measure the Total Solar Irradiance     

M. Meftah  S. Dewitte  A. Irbah  A. Chevalier  C. Conscience  D. Crommelynck  E. Janssen  S. Mekaoui 《Solar physics》2014,289(5):1885-1899

The Picard spacecraft was successfully launched on 15 June 2010, into a Sun-synchronous orbit. The mission represents one of the European contributions to solar observations and Essential Climate Variables (ECVs) measurements. The payload is composed of a Solar Diameter Imager and Surface Mapper (SODISM) and two radiometers: SOlar VAriability Picard (SOVAP) and PREcision MOnitor Sensor (PREMOS). SOVAP, a dual side-by-side cavity radiometer, measures the total solar irradiance (TSI). It is the sixth of a series of differential absolute-radiometer-type instruments developed and operated in space by the Royal Meteorological Institute of Belgium. The measurements of SOVAP in the summer of 2010 yielded a TSI value of 1362.1 W?m^?2 with an uncertainty of ±?2.4 W?m^?2 (k=1). During the periods of November 2010 and January 2013, the amplitude of the changes in TSI has been on the order of 0.18 %, corresponding to a range of about 2.4 W?m^?2.  相似文献