Mercury content of mussels from the St. Lawrence Estuary and northwestern Gulf of St. Lawrence, Canada

A first survey of the mercury content of intertidal mussels in the St. Lawrence Estuary and part of the Gulf of St. Lawrence shows means values ranging from 0.160 to 0.629 ppm (dry weight). Highest values (grand mean 0.430 ppm) were found in the upper part of the lower estuary, lowest values (grand mean 0.172 ppm) on the north shore of the estuary and Gulf, and intermediate values along the Gaspé Peninsula. The results indicate a decreasing gradient in mercury levels from the mouth of the Saguenay Fjord seaward.     

Evolution de la structure de la couche limite planetaire sur des sites oceaniques et continentaux

We have studied the evolution of the planetary boundary layer using both oceanic and continental stations. This has been possible through the analysis of twice-daily temperature radiosondes at three different oceanic stations (Point A; Point K; and Azores) and also at three continental stations (Berlin, Trappes and Madrid) all situated in the Northern Hemisphere. We have studied the annual evolution of mixing layers and of temperature inversion levels; an annual evolution presenting a minimum in winter and a maximum in summer has been observed in the continental stations; the oceanic stations present a lesser variation and in the opposite sense. As for the elevated inversion layers, their maximum frequency can be observed in summer at the oceanic stations and in winter at the continental stations. We have shown that considering the studied stations, both the level and the frequency of the elevated inversion layers are similar at 00 h and at 12 h; such a result is important because these layers regulate the intensity of the exchanges between the ground and the free atmosphere. Using the equivalent coefficient, we have determined the annual variation of the vertical exchanges between the surface and different altitudes. At the continental stations, the vertical exchanges are more important in summer than they are in winter; the opposite behaviour occurs at the oceanic stations.     

Sulfur in peat-forming systems of the Okefenokee Swamp and Florida Everglades: origins of sulfur in coal

Six sulfur forms were investigated in profiles of freshwater- and marine-derived peat-forming systems of the Okefenokee Swamp, Georgia and Everglades Swamp, Florida. Total sulfur levels of 0.1–10% were found, thus indicating a major incorporation of sulfur in the very early stages of coal formation. The quantities of hydrogen sulfide and elemental sulfur observed appeared to be indicative of whether marine or freshwater conditions prevailed at the site of deposition. Carbon-bonded sulfur accounted for 70% of the total sulfur in the freshwater peat and 50% of the total sulfur in the marine peat. Over 15% of the total sulfur was in pyritic combination in the marine environment, while levels of pyrite in the freshwater peats were an order of magnitude lower. An ester-sulfate fraction represented 25% of the total sulfur in both freshwater and marine peats. The levels of sulfur forms in the peat profiles are compared to those observed in living plants and to various coals; levels of pyrite and organic sulfur in the peat are similar to those found by other investigators in freshwater-derived and marine-derived coals.     

Statistical analyses of the zeolites clinoptilolite and heulandite

Cluster analysis showed that at least five compositional subgroups exist within the heulandite family of zeolites. The two extreme members of these five groups are the traditional heulandites and clinoptilolites. At a coarser level of clustering, two subgroups, clinoptilolite and heulandite, are evident. As shown by discriminant analysis, the most important compositional variable distinguishing all these groups is calcium. From principal components analysis, it was found that the c cell dimensions of the heulandite family of zeolites varies directly with aluminum and inversely with silicon. The a cell dimension and the β angle seem to vary inversely with the iron content. The b cell dimension may vary inversely with iron and aluminum and directly with silicon.     

Generation of homologous porphyrins under simulated geochemical conditions

Crude oils generally contain at least one symmetrical homologous series of porphyrins, which is usually centered at m/e 476 (DPEP) or m/e 478 (etioporphyrin). Simulated geochemical conditions in the present study resulted in decarboxylations and alkylations which ultimately led to the synthesis of homologous porphyrins from a single porphyrin. In several series of closed tube experiments, mesoporphyrin IX dimethylester (MPDME) was mixed with a variety of constituents including benzene, acetic acid, propionic acid, water and clay; the experiments were performed at temperatures between 135°C and 400°C at time intervals up to 80 days. Dealkylation, alkylation, hydrolysis, decarboxylation and metallation products were observed. An unsymmetrical homologous series of porphyrins was produced from MPDME. The dominant mass was m/e 478 (corresponding to a double deoarboxylation). Dealkylation products in multiples of 14 amu below the m/e 478 peak comprised the other members of the series. Cu-MPDME also produced homologous porphyrins. These, however, exhibited symmetry about the dominant members, similar to the symmetry found for the porphyrins of most petroleums and oil shales.     

Dynamics of the Jupiter Trojans with Saturn’s perturbation when the two planets are in migration

In a previous paper (Hou et al. in Celest Mech Dyn Astron 119:119–142, 2014a), the problem of dynamical symmetry between two Jupiter triangular libration points (TLPs) with Saturn’s perturbation in the present configuration of the two planets was studied. A small short-time scale spatial asymmetry exists but gradually disappears with the time going, so the planar stable regions around the two Jupiter TLPs should be dynamically symmetric from a longtime perspective. In this paper, the symmetry problem is studied when the two planets are in migration. Several mechanisms that can cause asymmetries are discussed. Studies show that three important ones are the large short-time scale spatial asymmetry when Jupiter and Saturn are in resonance, the changing orbits of Jupiter and Saturn in the planet migration process, and the chaotic nature of Trojan orbits during the planet migration process. Their joint effects can cause an observable difference to the two Jupiter Trojan swarms. The thermal Yarkovsky effect is also found to be able to cause dynamical differences to the two TLPs, but generally they are too small to be practically observed.     

Estuary/ocean exchange and tidal mixing in a Gulf of Maine Estuary: A Lagrangian modeling study

A Lagrangian particle method embedded within a 2-D finite element code, is used to study the transport and ocean–estuary exchange processes in the well-mixed Great Bay Estuarine System in New Hampshire, USA. The 2-D finite element model, driven by residual, semi-diurnal and diurnal tidal constituents, includes the effects of wetting and drying of estuarine mud flats through the use of a porous medium transport module. The particle method includes tidal advection, plus a random walk model in the horizontal that simulates sub-grid scale turbulent transport processes. Our approach involves instantaneous, massive [O(500,000)] particle releases that enable the quantification of ocean–estuary and inter-bay exchanges in a Markovian framework. The effects of the release time, spring–neap cycle, riverine discharge and diffusion strength on the intra-estuary and estuary–ocean exchange are also investigated.The results show a rather dynamic interaction between the ocean and the estuary with a fraction of the exiting particles being caught up in the Gulf of Maine Coastal Current and swept away. Three somewhat different estimates of estuarine residence time are calculated to provide complementary views of estuary flushing. Maps of residence time versus release location uncover a strong spatial dependency of residence time within the estuary that has very important ramifications for local water quality. Simulations with and without the turbulent random walk show that the combined effect of advective shear and turbulent diffusion is very effective at spreading particles throughout the estuary relatively quickly, even at low (1 m²/s) diffusivity. The results presented here show that a first-order Markov Chain approach has applicability and a high potential for improving our understanding of the mixing processes in estuaries.