An overview of toxicant identification in sediments and dredged materials

The identification of toxicants affecting aquatic benthic systems is critical to sound assessment and management of our nation's waterways. Identification of toxicants can be useful in designing effective sediment remediation plans and reasonable options for sediment disposal. Knowledge of which contaminants affect benthic systems allows managers to link pollution to specific dischargers and prevent further release of toxicant(s). In addition, identification of major causes of toxicity in sediments may guide programs such as those developing environmental sediment guidelines and registering pesticides, while knowledge of the causes of toxicity which drive ecological changes such as shifts in benthic community structure would be useful in performing ecological risk assessments. To this end, the US Environmental Protection Agency has developed tools (toxicity identification and evaluation (TIE) methods) that allow investigators to characterize and identify chemicals causing acute toxicity in sediments and dredged materials. To date, most sediment TIEs have been performed on interstitial waters. Preliminary evidence from the use of interstitial water TIEs reveals certain patterns in causes of sediment toxicity. First, among all sediments tested, there is no one predominant cause of toxicity; metals, organics, and ammonia play approximately equal roles in causing toxicity. Second, within a single sediment there are multiple causes of toxicity detected; not just one chemical class is active. Third, the role of ammonia is very prominent in these interstitial waters. Finally, if sediments are divided into marine or freshwater, TIEs perforMed on interstitial waters from freshwater sediments indicate a variety of toxicants in fairly equal proportions, while TIEs performed on interstitial waters from marine sediments have identified only ammonia and organics as toxicants, with metals playing a minor role. Preliminary evidence from whole sediment TIEs indicates that organic compounds play a major role in the toxicity of marine sediments, with almost no evidence for either metal or ammonia toxicity. However, interpretation of these results may be skewed because only a small number of interstitial water (n = 13) and whole sediment (n = 5) TIEs have been completed. These trends may change as more data are collected.     

The relation between rigorous and Helmert’s definitions of orthometric heights

Following our earlier definition of the rigorous orthometric height [J Geod 79(1-3):82–92 (2005)] we present the derivation and calculation of the differences between this and the Helmert orthometric height, which is embedded in the vertical datums used in numerous countries. By way of comparison, we also consider Mader and Niethammer’s refinements to the Helmert orthometric height. For a profile across the Canadian Rocky Mountains (maximum height of ~2,800 m), the rigorous correction to Helmert’s height reaches ~13 cm, whereas the Mader and Niethammer corrections only reach ~3 cm. The discrepancy is due mostly to the rigorous correction’s consideration of the geoid-generated gravity disturbance. We also point out that several of the terms derived here are the same as those used in regional gravimetric geoid models, thus simplifying their implementation. This will enable those who currently use Helmert orthometric heights to upgrade them to a more rigorous height system based on the Earth’s gravity field and one that is more compatible with a regional geoid model.     

Explicit formula for the geoid-quasigeoid separation

The explicit formula for the geoid-to-quasigeoid correction is derived in this paper. On comparing the geoidal height and height anomaly, this correction is found to be a function of the mean value of gravity disturbance along the plumbline within the topography. To evaluate the mean gravity disturbance, the gravity field of the Earth is decomposed into components generated by masses within the geoid, topography and atmosphere. Newton’s integration is then used for the computation of topography-and atmosphere-generated components of the mean gravity, while the combined solution for the downward continuation of gravity anomalies and Stokes’ boundary-value problem is utilized in computing the component of mean gravity disturbance generated by mass irregularities within the geoid. On application of this explicit formulism a theoretical accuracy of a few millimetres can be achieved in evaluation of the geoid-to-quasigeoid correction. However, the real accuracy could be lower due to deficiencies within the numerical methods and to errors within the input data (digital terrain and density models and gravity observations).     

Doppler radar observation, CG lightning activity and aerial survey of a multiple downburst in southern Germany on 23 March 2001

Two downburst events from one thunderstorm are investigated, which occurred on 23 March 2001, in Germany's climatologic annual minimum of downburst activity. Observations by two Doppler radars are combined with hail reports, ground lightning detection and an aerial survey conducted after the event. The downburst-producing storm had formed at a synoptic convergence line within the warm sector of a cyclone. It had a remarkably high propagation speed of up to 31 m s^− 1 corresponding to the mid-tropospheric flow. Thus, by superposition with the storm motion, even two weak downbursts were sufficient to cause the observed damage of F1 and F2 intensity, respectively. While in its late stages, the storm was dynamically characterized by lower- and mid-tropospheric divergence; at about the time of the first downburst, a mesocyclonic vortex signature was verified. Aside from mid-tropospheric dry air entrainment, a thermodynamic explanation for the triggering of the two downbursts by melting of small hail according to recent findings by Atlas et al. [Atlas, D., Ulbrich, C.W., Williams, C.R., 2004. Physical origin of a wet microburst: observations and theory. J. Atmos. Sci. 61, 1186–1196] appears probable. Despite the lack of warnings to the public, the storm's potential for hail and strong straight-line winds was detected by the German weather service radar software CONRAD more than a half hour before the downbursts occurred.     

Relative influence of vegetation on urban energy budgets and surface temperatures

Two deterministic models were combined: one for canopy leaf energy budgets and one for street canyon energy budgets. The effects of street parks and roof gardens in contrast to non-vegetated city blocks were examined by the use of four typical urban morphologies, which were exposed latitudinally to summer and winter simulations. A variety of increases and decreases in shortwave radiation, net radiation, sensible heat flux, and system reradiation resulted. These changes appear to represent the generalized limits of the possible responses to the addition of vegetation to non-vegetated city blocks.     

Response of rocks to impact loading by bars with pointed ends

SummaryResponse of Rocks to Impact Loading by Bars with Pointed Ends An experimental investigation was undertaken to study the response of three rocks — shale, limestone and diorite — to dynamic loading modelling hammer drilling. A long transmission rod subjected to pendulum impact at its distal end transmitted stress waves to six different heads whose tips consisted of 60°, 90°, and 120° cones or wedges in initial contact with the rock surface. Force and linear penetration histories monitored near the interface were found to be in good agreement with predicted values based on strain measurements at the center and distal end of the transmission bar and use of a one-dimensional theory of elastic wave propagation. The dynamic indentation measurements were also found to be in good agreement witha posteriori determination of the crater depth.Effects of multiple wave reflections and repeated impact on the contact force and rock deformation were determined as a function of the input energy. It was found that an optimum value of this energy exists for most efficient penetration for each of the heads utilized. Dynamic force-penetration curves were compared with corresponding static values obtained from an Instron testing machine. The force history resulting from the impact of a commercial pick-ax suspended in a pendulum arrangement was measured for both the conical and wedge-shaped tips of the device.

---

ZusammenfassungDas Verhalten von Gesteinen unter stoartiger Belastung mittels gespitzter Stäbe Es wurde eine experimentelle Untersuchung des Verhaltens dreier Gesteine, nämlich grüner Tonschiefer, Kalkstein und Diorit, unter stoßartiger Belastung, die als Modell der Wirkung eines Bohrhammers dienen soll, durchgeführt. Ein langer Stab war vorne mit einer Spitze in Keil- oder Kegelform mit einem Öffnungswinkel von 60°, 90° oder 120° versehen, welche bei Versuchsbeginn gerade die Probe berührte. Am anderen Ende wurde der Stab von einem fallenden Pendel getroffen. Der zeitliche Verlauf der Kraft und der Eindringung, die in der Nähe der Spitze des Stabes gemessen wurde, stimmte gut mit jenen Werten überein, die auf Grund von Dehnungsmessungen in der Mitte und am Stoßpunkt mittels einer eindimensionalen Theorie der Wellenfortpflanzung errechnet wurden. Die dynamischen Tiefenmessungen des Kraters ergaben auch eine gute Übereinstimmung mit den Werten, die nach dem Experiment bestimmt wurden.Die Wirkung von mehreren Wellenreflexionen und wiederholtem Stoß auf die Kontaktkraft und die Gesteinsdeformation wurde als Funktion der Anfangsenergie bestimmt. Es zeigte sich, daß es für jede verwendete Spitzenform einen optimalen Energiebetrag gibt, bei dem die günstigste Eindringung erfolgt. Dynamische Kraft-Eindringungskurven werden verglichen mit den entsprechenden statischen Werten, die mittels einer Instron-Testapparatur gemessen wurden. Überdies wurde der Kraftverlauf an Keil- und Kegelende einer Spitzhacke, die als Pendel auf eine Steinprobe aufschlug, gemessen.

---

RésuméReponses de certaines roches aux chocs exercés par des barres à extremités pointues Des expériences ont èté entreprises pour étudier la reponse de trois roches — schiste vert, calcaire, diorite — aux percussions exercées par un modèle de marteau perforateur. Un pendule ballistique heurte l'extremité libre d'une longue barre, à travers laquelle des ondes de contrainte se propagent et atteignent à l'autre extrémité une tête constitutée suivant les cas par une cône ou un dièdre d'angle 60°, 90° ou 120°, en contact avec la roche à l'instant initial. Les résultats obtenus en ce qui concerne l'évolution de la rorce et l'évolution de la pénétration lineaire sont en bon accord avec les valeurs prédites par le théorie unidimensionelle de la propagation des ondes élastiques, à partir des constrainte mesurées au centre et à l'extremité libre de la barre. Les mesures de la pénétration pendant l'experiénce sont également en bon accord avec la détermination à postériori de la profondeur des cratères.L'effet des réflexions multiples des ondes et l'effet de la répétition des impacts sur la force de contact et sur la déformation de la roche sont déterminés en fonction de l'énergie d'impact. Pour chacune des têtes utilisées on a trouvé qu'il existe une énergie optimale, c'est à dire une energie permettant d'obtenir la meilleure pénétration. Les courbes représentant la pénétration dynamique en fonction de la force sont comparées aux courbes correspondant en cas statique, obtenus par une machine d'Instron. L'évolution de la force résultant de l'impact d'une pioche ordinaire a èté mesurée pour des têtes constituées soit par des cônes soit par des dièdres.

---

---

With 27 Figures     

Die fazielle und paläogeographische Entwicklung der infrakambrischen bis ordovizischen Sedimente im Mittleren Antiatlas um Agdz (S-Marokko)

Zusammenfassung Die Entwicklung des Adoudounien (Infrakambrium) und Géorgien (Unterkambrium) ist im Mittleren Antiatlas durch einen Wechsel von marinen und kontinentalen Sedimenten gekennzeichnet. Wildbachablagerungen an der Basis und an den Beckenrändern werden von marin-marginalen stromatolithischen Karbonaten abgelöst. Ignimbrite belegen wiederholte terrestrische Sedimentation.Mit fluviatilen Sanden und wiederum Stromatolithen und lagunären Karbonaten (mit ersten Trilobiten!) setzt ein zweiter transgressiver Großzyklus ein, der an der Wende Infra-/Unter-Kambrium einen ersten Höhepunkt erreicht. Durch regressive Kleinzyklen charakterisierte Abfolgen leiten zu Sandsteinen über, die als Ablagerungen eines Deltas gedeutet werden.Vom Mittelkambrium bis Ordovizium dominiert marine Schelfsedimentation.

---

The formations of Adoudounien (Infra Cambrian) and Géorgien (Lower Cambrian) of the middle Anti-Atlas are characterized by an alternation of marine and continental sediments. Torrent conglomerates at the base and the margins of the basin took turns to marine-marginal stromatolitic carbonates. Ignimbrites prove repeated terrestrial sedimentation.A second transgressiv megasequence begins with fluviatil sands and goes on with stromatolites and lagoon carbonates (first Trilobites). This transgression reachs his first culmination at the Infra-/Lower-Cambrian boundary. Typical regressiv cycles form a transition to sandstones, which are interpreted as sediments of a delta.Marine shelf environment dominates from Middle Cambrian to Ordovician beds.

---

Résumé Dans le moyen Anti-Atlas, l'évolution de l'Adoudounien et du Géorgien est caractérisée par un changement des sédiments marins et continentaux. Les dépôts des torrents à la base et dans la bordure du bassin font place à des carbonates marins marginaux stromatolithiques. Les ignimbrites marquent le retour fréquent à la sédimentation terrestre.Une deuxième mégaséquence transgressive débute avec des sables fluviatiles, des stromatolithes et des carbonates lagunaires (premiers trilobites). La transgression atteint une première phase culminante à la transition de l'Adoudounien au Géorgien. Des séquences caractérisées par de petits cycles régressifs conduisent à des grès qui pourraient être interpré tés comme des sédiments deltaïques.A partir du Cambrien moyen jusqu'à l'Ordovicien prédomine un milieu de plate-forme externe.

---

Adoudounien — — Géorgien — — . — — . , - , , . , , . .

     

Geothermal gas equilibria

Comparison of theoretical and analytical equilibrium constants based on the reactions CH₄ + 2H₂O = CO₂ + 4H₂, 2NH₃ = N₂ + 3H₂ and iron(II)-aluminium-silicate + 2H₂S = FeS₂ + H₂ + aluminium-silicate, shows that the composition of fluids discharged from geothermal areas in New Zealand (Wairakei, Kawerau, Broadlands) reflects close to complete attainment of chemical equilibrium within the system H₂O, CO₂, H₂S, NH₃, H₂, N₂ and CH₄. Under conditions prevailing in explored geothermal systems in New Zealand, the minerals graphite (elemental carbon), anhydrite, pyrrhotite, magnetite do not appear to take part in the overall equilibrium system. The three physical parameters required to evaluate geothermal gas reactions are temperature, pressure and vapor-liquid ratios within the gas equilibration zone.