Nutrient Distributions In An Estuary - Evidence Of Chemical Precipitation Of Dissolved Silicate And Phosphate

Continuous autoanalytical recordings of the axial distributions of dissolved nitrate, silicate and phosphate in the influent freshwater and saline waters of the Tamar Estuary, south-west England have been obtained. Short-term variability in the distributions was assessed by repetitive profiling at approximately 3-h intervals on a single day and seasonal comparisons were obtained from ten surveys carried out between June 1977 and August 1978. Whereas nitrate is always essentially conserved throughout the upper estuary, the silicate- and phosphate-salinity relationships consistently indicate a non-biological removal of these nutrients within the low (0–10%) salinity range. Attempts to quantify precisely the degree of removal and to correlate this with changes in environmental properties (pH, turbidity, chlorophyll fluorescence, salinity, freshwater composition) were mainly inconclusive due to short-term fluctuations in the riverine concentrations of silicate and phosphate advected into the reactive region and to the rapid changes in turbidity brought about by tidally-induced resuspension and deposition of bottom sediment.

Detection and impacts of leakage from sub-seafloor deep geological carbon dioxide storage

Fossil fuel power generation and other industrial emissions of carbon dioxide are a threat to global climate1, yet many economies will remain reliant on these technologies for several decades2. Carbon dioxide capture and storage (CCS) in deep geological formations provides an effective option to remove these emissions from the climate system3. In many regions storage reservoirs are located offshore4, 5, over a kilometre or more below societally important shelf seas6. Therefore, concerns about the possibility of leakage7, 8 and potential environmental impacts, along with economics, have contributed to delaying development of operational CCS. Here we investigate the detectability and environmental impact of leakage from a controlled sub-seabed release of CO2. We show that the biological impact and footprint of this small leak analogue (<1 tonne CO2 d−1) is confined to a few tens of metres. Migration of CO2 through the shallow seabed is influenced by near-surface sediment structure, and by dissolution and re-precipitation of calcium carbonate naturally present in sediments. Results reported here advance the understanding of environmental sensitivity to leakage and identify appropriate monitoring strategies for full-scale carbon storage operations.

Detection and impacts of leakage from sub-seafloor deep geological carbon dioxide storage

Fossil fuel power generation and other industrial emissions of carbon dioxide are a threat to global climate1, yet many economies will remain reliant on these technologies for several decades2. Carbon dioxide capture and storage (CCS) in deep geological formations provides an effective option to remove these emissions from the climate system3. In many regions storage reservoirs are located offshore4, 5, over a kilometre or more below societally important shelf seas6. Therefore, concerns about the possibility of leakage7, 8 and potential environmental impacts, along with economics, have contributed to delaying development of operational CCS. Here we investigate the detectability and environmental impact of leakage from a controlled sub-seabed release of CO2. We show that the biological impact and footprint of this small leak analogue (<1 tonne CO2 d−1) is confined to a few tens of metres. Migration of CO2 through the shallow seabed is influenced by near-surface sediment structure, and by dissolution and re-precipitation of calcium carbonate naturally present in sediments. Results reported here advance the understanding of environmental sensitivity to leakage and identify appropriate monitoring strategies for full-scale carbon storage operations.

Algal Calcification and Silicification

The algae represent major producers of calcium carbonate and silica among the world's biota. Calcification involves the precipitation of CaCO3 from Ca2+ and CO32− ions. Algal calcification by coccolithophores may account for up to half of global oceanic CaCO3 production. Silicification, the transformation of silicic acid into skeletal material, occurs in a few algal groups. The abundant diatoms represent the major silicifiers, playing a key role in marine silica cycling. Fossilised diatomaceous deposits have long been exploited for building and filling materials. Biomineralisation of calcium and silicon require homeostatic ion controls that are well characterised for Ca2+ and H+ in coccolithophores. Calcification occurs in an alkalinised vesicle, while silicification requires an acidic pH. Research on silicification remains focused upon cell wall development. Initiation and development of structures that are mineralised intracellularly requires initiation and regulation by organic components within the vesicles. Low-temperature, low-pressure biogenic formation of silica and calcite has potential for biotechnological application in novel industrial processes.

Algal Calcification and Silicification

The algae represent major producers of calcium carbonate and silica among the world's biota. Calcification involves the precipitation of CaCO3 from Ca2+ and CO32− ions. Algal calcification by coccolithophores may account for up to half of global oceanic CaCO3 production. Silicification, the transformation of silicic acid into skeletal material, occurs in a few algal groups. The abundant diatoms represent the major silicifiers, playing a key role in marine silica cycling. Fossilised diatomaceous deposits have long been exploited for building and filling materials. Biomineralisation of calcium and silicon require homeostatic ion controls that are well characterised for Ca2+ and H+ in coccolithophores. Calcification occurs in an alkalinised vesicle, while silicification requires an acidic pH. Research on silicification remains focused upon cell wall development. Initiation and development of structures that are mineralised intracellularly requires initiation and regulation by organic components within the vesicles. Low-temperature, low-pressure biogenic formation of silica and calcite has potential for biotechnological application in novel industrial processes.