Trace metal distribution in the bed, bank and suspended sediment of the Ravensbourne River and its implication for sediment monitoring in an urban river

Purpose This study aims to identify a suitable sediment compartment for sediment quality monitoring by: (a) studying the concentration of trace metals (Cd, Cu, Ni, Pb and Zn) in the bed, bank and suspended sediment compartments of the Ravensbourne River to establish any differences in trace metal concentrations with compartment; (b) determining the influence of sediment particle size fractions ( 0.05) in the concentrations of metals between the suspended sediment and the < 63 μm bed sediment fraction, but there was a significant difference (p < 0.05) between the suspended sediment and the < 63 μm bank sediment fraction. There were also significant differences between the concentrations of metals in the < 63 μm and the 63 μm–2 mm fractions. Generally, the Ravensbourne River did not comply with the draft UK sediment quality guidelines for the metals analysed. Conclusions This study shows the importance of identifying a suitable sediment compartment to sample for compliance with sediment quality standards. The bed and suspended sediments are the most widely used sediment compartments for sediment monitoring, but collecting sufficient mass of the < 63 μm sediment fraction for monitoring presents a challenge for urban gravel bed rivers like the Ravensbourne River. It seems appropriate to establish individual monitoring regimes for different rivers

The geochemistry and origin of fluids in the carbonate structure of the Hranice Karst with the world\u27s deepest flooded cave of the Hranicka Abyss, Czech Republic

The origin of fluids in the Hranice Karst containing the deepest flooded abyss in the world has been investigated using hydrogeological, hydrogeochemical, and isotopic data. At least a part of the CO2 gas originates in the mantle as indicated by very enriched δ13C(DIC) values and from existing He isotope analyses. The origin of groundwater in the karstic aquifer which is exploited at the Teplice nad Bečvou Spa is meteoric with a recharge area about 200 m above the Bečva River valley as indicated by depleted values of δ2H and δ18O compared to the river water. Based on detectable tritium, the groundwater is from 20 to 50 years old. Water in the Hranicka Abyss and in the Zbrašov Aragonite Caves is a mixture of carbonate aquifer groundwater with the river and/or shallow groundwater comprising variable proportions of both end-members. Water in Death Cave Lake seems to be affected by agriculture contaminated shallow groundwater as indicated by increased nitrate concentration. Inverse geochemical modeling of aquifer geochemistry suggested two scenarios: (1) reaction of Mg-rich calcite with deep hypogenic CO2 (about 30 mmol/l) plus dissolution of trace amounts of halite and sylvite and cation exchange; (2) reaction of Mg-depleted calcite and Mg-silicate (talc) as a source of Mg together with deep CO2. Both scenarios were calibrated using δ13C(DIC) values and gave satisfactory results. A conceptual model of the site has been developed which includes a gravity-driven flow system where meteoric water which has recharged in the surrounding uplands is heated at depth and acquires large amounts of hypogenic CO2, which preferentially dissolves Mg-carbonates along the pre-existing tectonic features. The Miocene transgression followed by the later incision of the Bečva Valley played an important role in groundwater circulation and the origin of fluids

New palaeomagnetic data from the Palaeozoic carbonates of the Moravo-Silesian Zone (Czech Republic): evidence for a timing and origin of the late Variscan remagnetization

Palaeomagnetic studies were carried out in the Devonian–Early Carboniferous carbonates of the Moravo-Silesian Zone — MSZ (Czech Republic) in order to evaluate the timing and origin of late Variscan magnetic over printing. Sampling localities were spread out along the strike of the MSZ from the SW to NE. Previously published thermal maturity data have demonstrated a significant gradient from SW (burial temperatures 150–200gradeC) to NE of the region (250–300gradeC). A late Variscan remagnetization direction (component A), carried by magnetite, was identified in 6 localities. Three phases of the remagnetization in the MSZ might be distinguished which might be assigned to Early to Late Carboniferous, Late Carboniferous and Early Permian. They are coeval with remagnetization events distinguished in Ardennes. A correlation exists between thermal indices and un blocking temperature spectra of component A. Thermal activation nomograms show that component A might be either a thermoviscous or thermochemical remanent magnetization acquired due to a thermal event (deep burial) of 1–10 My duration and stabilized during subsequent uplift. A more ancient component B, identified in the SW part, previously interpreted as primary, is shown to be a synfolding remagnetisation. Itindicates 70grade clockwise rotations before the acquis tion of the component A