Dissolved organic phosphorus speciation in the waters of the Tamar estuary (SW England)

The speciation of dissolved organic phosphorus (DOP) in the temperate Tamar estuary of SW England is described. Eight stations from the riverine to marine end-members were sampled during four seasonal campaigns in 2007 and the DOP pool in the water column and sediment porewater was characterized and quantified using a flow injection manifold after sequential enzymatic hydrolysis. This enabled the enzymatically hydrolysable phosphorus (EHP) fraction and its component labile monoester phosphates, diester phosphates and a phytase-hydrolysable fraction that includes myo-inositol hexakisphosphate (phytic acid), to be determined and compared with the total DOP, dissolved reactive phosphorus (DRP) and total dissolved phosphorus (TDP) pools. The results showed that the DOP pool in the water column varied temporally and spatially within the estuary (1.1-22 μg L⁻¹) and constituted 6-40% of TDP. The EHP fraction of DOP ranged from 1.1-15 μg L⁻¹ and represented a significant and potentially bioavailable phosphorus fraction. Furthermore the spatial profiles of the three components of the EHP pool generally showed non-conservative behavior along the salinity gradient, with apparent internal estuarine sources. Porewater profiles followed broadly similar trends but were notably higher at the marine station throughout the year. In contrast to soil organic phosphorus profiles, the labile monoester phosphate fraction was the largest component, with diester phosphates also prevalent. Phytic acid concentrations were higher in the lower estuary, possibly due to salinity induced desorption processes. The EHP fraction is not commonly determined in aquatic systems due to the lack of a suitable measurement technique and the Tamar results reported here have important implications for phosphorus biogeochemistry, estuarine ecology and the development of efficient strategies for limiting the effects of phosphorus on water quality.     

The Effect of the Great Barrier Reef on the Propagation of the 2007 Solomon Islands Tsunami Recorded in Northeastern Australia

The effect of offshore coral reefs on the impact from a tsunami remains controversial. For example, field surveys after the 2004 Indian Ocean tsunami indicate that the energy of the tsunami was reduced by natural coral reef barriers in Sri Lanka, but there was no indication that coral reefs off Banda Aceh, Indonesia had any effect on the tsunami. In this paper, we investigate whether the Great Barrier Reef (GBR) offshore Queensland, Australia, may have weakened the tsunami impact from the 2007 Solomon Islands earthquake. The fault slip distribution of the 2007 Solomon Islands earthquake was firstly obtained by teleseismic inversion. The tsunami was then propagated to shallow water just offshore the coast by solving the linear shallow water equations using a staggered grid finite-difference method. We used a relatively high resolution (approximately 250 m) bathymetric grid for the region just off the coast containing the reef. The tsunami waveforms recorded at tide gauge stations along the Australian coast were then compared to the results from the tsunami simulation when using both the realistic 250 m resolution bathymetry and with two grids having fictitious bathymetry: One in which the the GBR has been replaced by a smooth interpolation from depths outside the GBR to the coast (the “No GBR” grid), and one in which the GBR has been replaced by a flat plane at a depth equal to the mean water depth of the GBR (the “Average GBR” grid). From the comparison between the synthetic waveforms both with and without the Great Barrier Reef, we found that the Great Barrier Reef significantly weakened the tsunami impact. According to our model, the coral reefs delayed the tsunami arrival time by 5–10 minutes, decreased the amplitude of the first tsunami pulse to half or less, and lengthened the period of the tsunami.     

Do galaxy mergers form elliptical galaxies? A comparison of kinematic and photometric properties

We present near-infrared K -band imaging and spectroscopy of a sample of galaxy mergers, which we use to derive light profile indices, absolute magnitudes and central velocity dispersions. We find that the light distributions of mergers more nearly resemble those of ellipticals than those of bulges, but that the mergers lie well away from the Fundamental Plane defined by the ellipticals. We interpret this as being due to enhancement of the K -band surface brightness of the mergers by a significant population of supergiant stars, and independent evidence for such a population is inferred from measurements of the depth of the 2.3-μm CO absorption feature.     

Geochemical changes during neutralisation of acid mine drainage in a dynamic mountain stream, New Zealand

The Mangatini Stream drains a coal mining area in the mountains of northwestern South Island of New Zealand. Abundant rainfall on pyritic rocks yields acid mine drainage (AMD) to the stream, which flows through a steep gorge at discharges that rapidly increase from <1 to >100 m³/s during frequent rain events. The AMD is treated with finely ground limestone, which is discharged as a slurry at a point in the middle of the gorge. The limestone slurry mixes and reacts with the AMD during flow ∼4 km downstream over ∼12 h. Neutralisation reactions increase stream pH from near 3 (untreated Mangatini Stream water impacted by AMD) to 5–6 in the first 250 m downstream, although mixing is commonly incomplete in this zone. Large stream discharge volumes in rain events dilute the neutralising material input, thus driving the pH back towards 4 downstream of treatment. More complete neutralisation is achieved 4 km downstream, even in major rain events, and pH can rise to >7. Partial neutralisation is sufficient to remove most of the dissolved Fe(III) (typically ∼30 mg/L) from the Mangatini Stream in the first 10 m, and remaining dissolved Fe is essentially all Fe(II), which decreases over time as it oxidises and precipitates. Dissolved Al in the Mangatini Stream (typically ∼50 mg/L) decreases steadily downstream over ∼100 m in the limestone mixing zone. Precipitated Fe and Al form amorphous oxyhydroxides that are transported as suspended solids and deposited on the stream bed with excess limestone in zones of low flow velocity. Dissolved Zn is removed from solution by adsorption to Fe oxyhydroxide when pH reaches ∼5, but dissolved Ni remains in solution despite the neutralisation process. Gypsum precipitation occurs throughout the limestone mixing zone, resulting in at least 30% decrease in dissolved . Minor ettringite forms in the first 100 m, but then probably redissolves. The limestone dosing system is an effective method of neutralising the effects of AMD and removing most dissolved metals in a steep mountain stream with frequent rain events where this dynamic environment places many constraints on treatment options.     

Diagenetic and sedimentary controls on porosity in Lower Carboniferous fine-grained lithologies,Krechba field,Algeria: A petrological study of a caprock to a carbon capture site

Fine-grained siliciclastic lithologies commonly act as sealing caprocks to both petroleum fields and host reservoirs for carbon capture (CO₂ sequestration) projects. Fine-grained lithologies are thus of great importance in controlling fluid flow and storage in the subsurface. However, fine-grained rocks are rarely characterised in terms of primary sedimentary characteristics, diagenesis and how these relate to their flow properties (i.e. sealing or caprock quality). Seventeen samples from Lower Carboniferous estuarine caprock to a gas field (also to be used as a carbon capture site), have been analysed using a range of petrological and petrophysical techniques. The rock unit that represents the caprock to this gas field was found to be predominantly silt grade with porosity values as low as 1.8%. In these rocks, caprock quality (porosity) is controlled by intrinsic and extrinsic factors linked to primary mineralogy and diagenetic processes. Depositional mineralogy was dominated by quartz, detrital mica, detrital clay (likely Fe-rich 7Å clay and illite–smectite) with minor feldspar and oxide phases. Diagenetic processes included compaction, minor feldspar dissolution and kaolinite growth and the more important processes of chlorite, siderite and quartz cementation, as well as the likely transformation of smectite into illite. Caprock quality is controlled by the primary quantity of illite-muscovite in the sediment and also by the localised extent of chlorite and quartz cementation. Deposition in an estuarine environment led to highly heterogeneous distribution of primary and diagenetic minerals, and thus caprock quality, between and within the samples.     

An updated evaluation of the global mean land surface air temperature and surface temperature trends based on CLSAT and CMST

Climate Dynamics - Past versions of global surface temperature (ST) datasets have been shown to have underestimated the recent warming trend over 1998–2012. This study uses a newly updated...     

Frictional effects on trapped shelf waves

This paper revisits models of coastal trapped waves and examines them with the inclusion of friction. In addition we use a numerical method which at least theoretically will have enhanced accuracy. The model has continuous stratification and variable depth. It is linear, quasigeostrophic and hydrostatic, and utilizes perturbation from this fundamental state. The model is applied with both idealized and realistic topography and stratification.Responsible Editior: Phil Dyke