Jens Skei

Fjords: Processes and Products

1 Introduction.- 1 Fjords and Their Study.- 1.1 Definition, Distribution, and History.- 1.2 Environmental Setting and Study.- 1.3 The Past, Present, and Future of Fjord Research.- 2 Environmental Setting.- 2.1 Geomorphology.- 2.2 Climate.- 2.3 Oceanographic Characteristics.- 2.4 Sediment Sources and Transport Mechanisms.- 2.5 Fjord History.- 2.6 Characteristic Features of Fjord Coastlines.- 2.7 Summary.- 2 Processes and Products.- 3 The Fluvial-Deltaic Environment.- 3.1 Runoff.- 3.2 Sediment Transport.- 3.3 Paraglacial Sedimentation.- 3.4 Fjord-Head Deltas.- 3.5 Summary.- 4 Circulation and Sediment Dynamics.- 4.1 Fjord Estuarine Circulation.- 4.2 Hypopycnal Sedimentation.- 4.3 Hyperpycnal Flow.- 4.4 Flushing and Deep Water Renewal.- 4.5 Ice Influences.- 4.6 Mixing Processes and the Seafloor Environment.- 4.7 Summary.- 5 Subaqueous Slope Failures.- 5.1 Mass Sediment Properties and Subaqueous Slope Stability.- 5.2 Release Mechanisms.- 5.3 Mass Transport Processes.- 5.4 The Products of Subaqueous Slope Failure.- 5.5 Summary.- 6 Biotic Processes.- 6.1 Pelagic and Littoral Processes.- 6.2 The Fjord Benthic Environment.- 6.3 Summary.- 7 Biogeochemistry.- 7.1 Particulate Sediment.- 7.2 Aerobic Diagenetic Reactions.- 7.3 Anoxic Environments.- 7.4 Summary.- 3 Implications/Applications.- 8 Environmental Problems: Case Histories.- 8.1 Introduction.- 8.2 Agfardlikavsa Fjord, Greenland.- 8.3 Resurrection Bay, Alaska.- 8.4 Port Valdez, Alaska.- 8.5 Howe Sound, British Columbia.- 8.6 Rupert Inlet, British Columbia.- 8.7 Saguenay Fjord, Quebec.- 8.8 Iddefjord, Norway/Sweden.- 8.9 Saudafjord, Southwest Norway.- 8.10 Sorfjord, West Norway.- 8.11 Ranafjord, Northern Norway.- 8.12 Loch Eil, Scotland.- 8.13 By fjord, Sweden.- 8.14 Summary of Impacts in Other Fjords.- 9 Future Fjord Research.- 9.1 Oceanographic Problems and Projects.- 9.2 Biogeochemical Problems and Projects.- 9.3 Biological Problems and Projects.- 9.4 Geological-Related Problems and Projects.- 9.5 Approaches.- References.- Fjord Index.

Partitioning and transport of metals across the O2H2S interface in a permanently anoxic basin: Framvaren Fjord, Norway☆

Abstract The geochemical processes operating on metals in anoxic marine waters influence metal mobility and mode of transport to the sediments in a manner different from that observed in oxic regimes. In order to better understand these processes, dissolved and particulate Mn, Fe, Co, Ni, Cu, Zn, and Cd concentrations were determined in the water column of a permanently anoxic basin, Framvaren Fjord, Norway. Class specific behavior determines the degree to which these metals are involved in the processes of redox cycling at the O 2 H 2 S interface and metal sulfide precipitation in the sulfidic water. Metal sulfide precipitation influences the magnitude of metal enrichment in the sediments. The transition metals, Mn, Fe, and Co, show active involvement in redox cycling, characterized by dissolved maxima just below the O 2 H 2 S interface. Nickel concentrations appear unaffected by processes influencing the profiles of the other metals. The metals, Cu, Zn, and Cd, display a dramatic solubility decrease across the interface, are not involved in redox cycling, and are enriched in the sediments relative to a lithogenic component by factors of 11, 105, and 420, respectively. Ion activity products of the metals and sulfide provide evidence that chemical equilibria with a pure metal sulfide solid phase is not the dominant process controlling dissolved metal concentrations in the sulfide containing waters.

Surface metal enrichment and partitioning of metals in a dated sediment core from a Norwegian fjord

Abstract A 24-cm long sediment core from an oxic fjord basin in Ranafjord, Northern Norway, was sliced in 2 cm sections and analysed for As, Co, Cu, Ni, Hg, Pb, Zn, Mn, Fe, ignition loss and Pb-210. Partitioning of metals between silicate, non-silicate and non-detrital phases was assessed by leaching experiments, in an attempt to understand the mechanisms of surface metal enrichment in sediments. Relative to metal concentrations in sediments deposited in the 19th century, metals in near surface sediments were enriched in the following order: Pb > Mn > Hg > Zn > Cu > As > Fe. Cobalt and Ni showed no enrichment. The non-detrital fraction of Cu, Pb, Mn and Zn was significantly higher in the upper 10 cm than at greater depth in the core. This corresponds to sediments deposited since 1900, when mining activities started in the area. The enrichment of Cu, Pb and Zn is assumed to be mainly a result of mining, while Mn is apparently enriched in the surface due to migration of dissolved Mn and precipitation in the oxic surface layer. Elevated concentrations of As and Fe in the upper 4 cm are presumably due to discharges from a coke plant and an iron works respectively. The excess Hg present in the near surface sediments is tightly bound, either in coal particles or ore dust introduced by local industry, or via long distance transport of atmospheric particles. Calculations of metal flux to the sediments indicate an anthropogenic flux of Zn equal to its natural flux, while the flux of Pb shows a threefold increase above natural input.

Geochemical and sedimentological considerations of a permanently anoxic fjord — Framvaren, south Norway

Abstract Framvaren, a fjord in south Norway, is an example of extreme anoxia, due to the geomorphological features (sill depth ∼ 2 m, basin depth ∼ 180 m). The postglacial history of Framvaren is outlined emphasizing the preservation of environmental changes in the properties of the water and the sediments. High levels of hydrogen sulfide in the water (170–180 ml l −1 or 7–8 mM H 2 S) dense populations of photosynthetic bacteria at the redox boundary (total number ∼ 3 × 10 6 ml −1 ), metal-sulfide formation in the anoxic water (e.g. framboidal pyrite and zinc sulfide) and organic-rich bottom sediments with high metal content (e.g. > 1000 ppm Zn), are typical examples. The rate of sedimentation is estimated in three independent ways suggesting an average, annual flux of ∼ 100 g m −2 yr −1 in the central basin of Framvaren. Fluxes of organic matter and zinc to the sediments are calculated and compared with potential sources.

A stable sulfur and oxygen isotopic investigation of sulfur cycling in an anoxic marine basin, Framvaren Fjord, Norway

Abstract In 1993 we measured the δ34S values of total dissolved sulfide (δ34S∑H2S) and sulfate (δ34SSO4−) and the δ18O of sulfate (δ18OSO4−) from water samples collected across the oxic–anoxic interface and in the deep permanently anoxic waters of the stratified Framvaren fjord in southern Norway. Near the chemocline, variations in the δ34SSO4− and δ18OSO4− values were generally less than 1‰ from ambient seawater values. However, a minimum δ34SSO4− value of +19.7‰ was detected at 20 m depth, which coincided with the depth that sulfide first appeared and may reflect sulfide oxidation. Small increases in δ34SSO4− and δ18OSO4− values 3 m below this depth are consistent with a zone of sulfur disproportionation. The δ34S∑H2S value near the interface at 22 m was −19.8‰, which is 41.2‰ depleted in 34S relative to the sulfate collected at that depth. In close agreement with earlier measurements made at Framvaren in 1982, the δ34SSO4− values collected from the deeper anoxic waters showed a marked 34S enrichment with depth, which corresponded with a decrease in the sulfate concentration. These results are interpreted to be the result of active dissimilatory sulfate reduction. A Rayleigh plot for the sulfate data measured in 1993 provides estimates for the sulfur and oxygen isotope enrichment factors (es and eo, respectively) for sulfate reduction of −41.5‰ and −9.8‰, respectively, with the former value matching closely the observed difference in δ34S between the dissolved sulfide and sulfate near the interface. Our results from 1993, however, contrast with δ34SSO4− and δ34S∑H2S data in the water column made in 1983 by Anderson et al. [Mar. Chem. 23 (1988) 283). We conclude that the results of 1983 may be anomalous, and as a result this may offer additional interpretations than what was previously provided for the origin of reduced inorganic sulfur in the sediments of Framvaren based on their measured δ34S values. We hypothesize that the lower δ34Strs values in the sediments relative to δ34S∑H2S values in the water column could also result from different rates of sulfate reduction, or in shallower sediments just beneath the chemocline, also from disproportionation of S∘, S2O3−, or SO3−. We hypothesize that the observed ratio of 4.4:1 for the measured changes in δ34SSO4− versus δ18OSO4− within the anoxic waters approximates the 4:1 atom ratio of oxygen to sulfur in the residual sulfate as a result of dissimilatory sulfate reduction and reflects little oxygen isotope exchange between intermediates of sulfur metabolism and water either during bacterial sulfate reduction or from sulfide reoxidation processes. Based on comparisons with other studies, we further propose that this lack of isotopic exchange with water, and the subsequent ∼4:1 ratio of δ34SSO4− versus δ18OSO4−, occurs under conditions that promote a unidirectional biochemical reaction for sulfate reduction during which kinetic isotope effects are fully expressed and are consequently reflected in the δ34SSO4− and δ18OSO4− values.

Framvaren: environmental setting

Abstract Framvaren, a permanently anoxic fjord on the southernmost point of Norway, is geomorphologically the result of glaciation and deglaciation. A barrier of glaciofluvial deposit was formed between the open sea and the landlocked water. Due to the isostatic uplift during the deglaciation period, the landlocked water was isolated from the sea and became a meromictic lake. Around 1850, a channel was cut in the barrier and the lake became a fjord with a sill depth of 2.5m and a basin depth of 180 m. The fjord is now permanently anoxic below 18 m depth. The tidal amplitude is close to 10 cm. Only 100 people live in the catchment area of Framvaren, hence it may be considered as a natural pristine laboratory, ideal for study by marine scientists interested in anoxic systems.

Formation of framboidal iron sulfide in the water of a permanently anoxic fjord - Framvaren, South Norway

Abstract Framvaren, a super-anoxic fjord in South Norway, has been the subject of research for six years. As part of the scientific program, the chemistry of iron in the water and the sediments has been investigated. Several particulate iron phases have been observed in the anoxic water, including silicate-bound iron from the source rock of the area, finely dispersed amorphous iron sulfide (which bleeds through 0.4 μm Nuclepore filters) and framboidal iron sulfide in the size range 3–10 μm. Although conclusive mineralogical evidence of framboidal pyrite formation in the water is lacking, several observations support the formation of pyrite at the oxic-anoxic interface where metabolizable organic matter, elemental sulfur and reactive iron are abundant.

Determination of polycyclic aromatic hydrocarbons in sediments and mussels from saudafjord, W. Norway, by glass capillary gas chromatography

Polycyclic aromatic hydrocarbons (PAH) have been determined, by glass capillary gas chromatography, in two species of bivalves (Mytilus edulis and Modiolus modiolus) and sediments of Saudafjorden, Norway. The PAH observed are derived from waste effluents from a ferro alloy smelter. Up to 34 PAH compounds were identified, including some reported to be carcinogenic. The concentrations decreased rapidly with distance from the source and with sediment depth, but could be traced more than 15 km from the source. Relative abundance of various PAH did not change significantly in the mussels collected from the head to the mouth of the fjord. In the sediments, however, phenanthrene increased from minor importance to dominance towards the mouth, whereas the relative content of anthracene and benzo [a]pyrene decreased. The results are compared with observations from other marine localities and discussed in relation to transport processes, biodegradation and chemical transformation in the sediments.

Partitioning and enrichment of trace metals in a sediment core from Framvaren, South Norway

Extremely high concentrations of Cd, Cu, Pb and Zn were recorded in the bottom sediments of the deep basin of Framvaren. The concentrations are comparable with those found in euxinic mid-Cretaceous black shales. The non-detrital phase (HOAc-extraction) constituted an average of 93, 25, 77 and 89% for Cd, Cu, Pb and Zn, respectively, of the total metal concentrations in the upper sediment. The most plausible explanation for the enrichment of metals is metal sulphide precipitation in the super-anoxic water (maximum 8 mmol l−1 total H2S). Metals could also be transferred to the sediments by sinking of organic matter (plankton and bacteria) produced in the euphotic zone. The variation in the concentrations of the non-detrital metal fraction reflects different solubility products of metal sulphide phases and organic matter associations.

Seasonal and vertical variations in the chemical composition of suspended particulate matter in an oxygen-deficient fjord

Chemical analysis of suspended particulate matter in marine waters gives insight into important geochemical processes. Additionally, fjords offer suitable locations to study these processes. The Bunnefjord in south-east Norway was selected for a 1-year study of the vertical and seasonal variations in the particulate matter chemistry. Analysis of particulate Al, Si, P, Fe and Mn on Nuclepore membrane filters by X-ray fluorescence spectrometry elucidates the distribution of various particulate matter phases in the water column. While particulate Al, Si and P are abundant above the halocline due to the influence of river water (Al), diatoms (Si) and organic matter (P), particulate Fe and Mn phases preferentially occur in the lowoxygenated bottom water. The latter is a result of redox reactions at or near the sediment-water interface. The mobility of Mn is particularly well demonstrated, showing a rapid loss of Mn from the sediments when the oxygen concentration in the bottom water dropped below 1 ml l−1. The flux of Mn from the sediments to the water and the conversion of dissolved Mn to a particulate phase was estimated to a minimum of 0·7 μg cm−2 day−1.