Lars Gronen

Heavy metals in river and coast sediments of the Jakarta Bay region (Indonesia) - Geogenic versus anthropogenic sources

Sediment geochemistry of the Jakarta region, a densely populated tropical coast, is studied - with particular focus on rivers discharging to Jakarta Bay. Weathering volcanics in the river catchment area control the composition of major elements, As, Cr and in part Cu. In contrast, Zn, Ni, Pb and partly Cu are affected by anthropogenic sources, mainly in central Jakarta City. The data reflect a high variability of local emission sources, among which metal processing industries, fertilizers or untreated animal waste may be important. In particular, the role of street dusts is emphasized. Locally, heavy metals reach levels considered to have adverse biological effects. River discharge leads to anthropogenic enrichment of heavy metals in the coastal sediments. Element data also show geogenic effects on the composition of the coastal sediments, such as mixing of detrital silicates with biogenic carbonates as well as suspended particulate matter from the ocean.

Novel Approach for Enhanced Scandium and Titanium Leaching Efficiency from Bauxite Residue with Suppressed Silica Gel Formation

The need of light weight alloys for future transportation industry puts Sc and Ti under a sudden demand. While these metals can bring unique and desired properties to alloys, lack of reliable sources brought forth a supply problem which can be solved by valorization of the secondary resources. Bauxite residue (red mud), with considerable Ti and Sc content, is a promising resource for secure supply of these metals. Due to drawbacks of the direct leaching route from bauxite residue, such as silica gel formation and low selectivity towards these valuable metals, a novel leaching process based on oxidative leaching conditions, aiming more efficient and selective leaching but also considering environmental aspects via lower acid consumption, was investigated in this study. Combination of hydrogen peroxide (H2O2) and sulfuric acid (H2SO4) was utilized as the leaching solution, where various acid concentrations, solid-to-liquid ratios, leaching temperatures and times were examined in a comparative manner. Leaching with 2.5 M H2O2: 2.5 M H2SO4 mixture at 90 °C for 30 min was observed to be the best leaching conditions with suppressed silica gel formation and the highest reported leaching efficiency with high S/L ratio for Sc and Ti; 68% and 91%; respectively.

Tl-speciation of aqueous samples – a review of methods and application of IC-ICP-MS/LC-MS procedures for the detection of (CH3)2Tl+ and Tl+ in river water

This study provides an overview on Tl-speciation methods developed in the last years. Most of them require transformation of a species and do not allow direct detection of the species of interest. LC-MS and IC-ICP-MS methods are optimised for direct analysis of the Tl-species Tl+ and (CH3)2Tl+ (dimethylthallium (DMT)) in freshwater on a ng L−1 level. The methods are applied in a study of water from Vicht River in Stolberg (Germany). Tl+ is shown to be at least in part derived from anthropogenic sources among which the industrial sources may be significant. The natural occurrence of DMT is proven, although this Tl-species is temporally variable in abundance and Tl+ predominates.

Cementation and structural diagenesis of fluvio-aeolian Rotliegend sandstones, northern England

Quartz cementation in sandstones is closely linked to grain coating phases and diagenetic alteration. Grain coatings consisting of illite–smectite stained with iron oxides and hydroxides are able to preserve large amounts of porosity by preventing the formation of syntaxial quartz overgrowth cement. The Penrith Sandstone Formation was chosen as an analogue for Rotliegend reservoirs to test the impact of grain coatings on quartz cementation. This adds to an existing model of cementation. Differences of grain coating coverage can be linked to grain size. Extensive grain coatings are present in finer grained laminae in some samples. Coarser grained laminae contain less extensive grain coatings. The analysis of grain coatings based on standard petrographic analyses is combined with high-resolution QEMSCAN® analyses. Structural features include deformation bands of different ages. Diagenetic alterations around faults, recorded by grain coatings, allow the delineation of relative temporal relations, revealing at least two generations of deformation band formation associated with normal faulting. In the Vale of Eden succession one normal faulting event postdates burial diagenetic quartz cementation as is evident by fault focused fluid flow and associated bleaching of iron and absence of quartz overgrowth.