Changes in topography and vegetation near gaps in a protective foredune

Data gathered on a foredune on a nourished beach reveal the relationships between topography and plant communities at gaps in the dune crest. Sand inundation at gaps allows plants in some portions of the dune to rejuvenate to earlier successional stages, while an increase in richness occurs in other portions. Ammophila breviligulata can create an initial dune ridge, colonize new areas of bare sand within the dune field, facilitate growth of other species, and provide a natural alternative to fencing in managing gaps. Foredune mobility can be considered a positive factor if beach width and dune volume provide adequate protection.     

The distribution of suspended particles in the Southern Beaufort Sea

The Mackenzie River estuary serves as an avenue for suspended particles to pass seaward. The horizontal distribution of surface suspended particles is compartible with the distribution of low-salinity surface waters. The water structure in the shelf area is highly stratified in summer due to a thin upper layer of low-salinity which has a high concentration of suspended particles. The concentration of suspended particles decreases with depth, but near the bottom a turbid layer had often been observed. It is likely that bottom current energy high enough to erode and maintain in suspension the bottom sediments below 15m in diameter does occur over this shelf area.     

Seasonal and Interannual Variability in the Distribution of Surface Nutrients and Dissolved Inorganic Carbon in the Northern North Pacific: Influence of El Niño

The seasonal and interannual changes in surface nutrients, dissolved inorganic carbon (DIC) and total alkalinity (TA) were recorded in the North Pacific (30–54°N) from 1995 to 2001. This study focuses on the region north of the subarctic boundary (∼40°N) where there was extensive monthly coverage of surface properties. The nutrient cycles showed large interannual variations in the eastern and western subarctic gyres. In the Alaska Gyre the seasonal depletion of nitrate (ΔNO₃) increased from 8–14 μmol kg⁻¹ in 1995–1999 to 21.5 μmol kg⁻¹ in 2000. In the western subarctic the shifts were similar in amplitude but more frequent. The large ΔNO₃ levels were associated with high silicate depletions, indicating enhanced diatom production. The seasonal DIC:NO₃ drawdown ratios were elevated in the eastern and central subarctic due to calcification. In the western subarctic and the central Bering Sea calcification was significant only during 1997 and/or 1998, two El Ni?o years. Regional C/N stoichiometric molar ratios of 5.7 to 7.0 (>40°N) were determined based on the years with negligible or no calcification. The annual new production (NP_a) based on ΔNO₃ and these C/N ratios showed large interannual variations. NP_a was usually higher in the western than in the eastern subarctic. However, values of 84 gC m⁻²yr⁻¹ were found in the Alaska Gyre in 2000 which is similar to that in the most productive provinces of the northern North Pacific. There were also large increases in NP_a around the Alaska Peninsula in 1997 and 1998. Finally, the net removal of carbon by the biological pump was estimated as 0.72 Gt C yr⁻¹ in the North Pacific (>30°N). This revised version was published online in August 2006 with corrections to the Cover Date.     

Novel technology in pollutant removal at source and bioremediation

Sewage disposal is a major environmental issue in both developed and developing countries and removal of pollutants such as organic matter, nutrients, heavy metals and persistent organic compounds is required to protect the environment. Novel biological systems using constructed mangrove wetland and immobilized microalgal beads have been developed as alternative systems for treating different types of sewage and pollution at source. The feasibility and efficiency of constructed mangrove wetland to remove organic matter and nutrients from primary settled municipal sewage were demonstrated through a series of greenhouse experiments and a pilot-scale field trial. The treatment efficiency of constructed mangrove wetland was comparable to, or higher than, the conventional constructed wetland. An immobilized microalgal system was developed to remove toxic persistent pollutants from industrial wastewater. Pollutant-resistant microalgal species were selected for culture in domestic wastewater. The harvested biomass was immobilized in alginate beads. Bench-scale experiments showed the algal beads were effective in removing industrial pollutants such as heavy metals (e.g. Cu, Zn, Ni, Cr, etc.), organometallic compounds (e.g. tributyltin, TBT), and persistent organic compounds (e.g. polycyclic aromatic hydrocarbons, PAHs) through biosorption and biodegradation. The adsorbed metals could be recovered by desorption process, and the beads could be used repeatedly for many adsorption–desorption cycles.     

Potential risks to freshwater resources as a result of leakage from CO<Subscript>2</Subscript> geological storage: a batch-reaction experiment

In assessing the feasibility of widespread deployment of CO₂ geological storage, it is prudent to first assess potential consequences of an error or accident that could lead to CO₂ leakage into groundwater resources above a sequestration interval. Information about the sensitivity of the groundwater system to introduction of CO₂ is needed in order to design groundwater monitoring program. A laboratory-batch experiment was conducted to explore the range of CO₂ impact on groundwater quality of a spectrum of representative aquifers, in the Gulf Coast region, USA. Results show that CO₂ elevated concentrations of many cations within hours or days. Two types of cations were recognized according to their concentration trends. Type I cations—Ca, Mg, Si, K, Sr, Mn, Ba, Co, B, Zn—rapidly increased following initial CO₂ flux and reached stable concentrations before the end of the experiment. Type II cations—Fe, Al, Mo, U, V, As, Cr, Cs, Rb, Ni and Cu—increased at the start of CO₂ flux, but declined, in most cases, to levels lower than pre-CO₂ concentrations. Dissolution of dolomite and calcite caused the largest increase in concentrations for Ca, Mg, Mn, Ba and Sr. Cation release rates decreased linearly as pH increased during mineral buffering. Experiment results suggest that carbonate minerals are the dominant contributor of changes in groundwater quality. Risk assessments of potential degradation of groundwater and monitoring strategies should focus on these fast-reacting minerals. Mobilization risk of Type II cations, however, may be self-mitigated because adsorption occurs when pH rebounds.