Recent paleorecords document rising mercury contamination in Lake Tanganyika

Recent Lake Tanganyika Hg deposition records were derived using ¹⁴C and excess ²¹⁰Pb geochronometers in sediment cores collected from two contrasting depositional environments: the Kalya Platform, located mid-lake and more removed from watershed impacts, and the Nyasanga/Kahama River delta region, located close to the lake’s shoreline north of Kigoma. At the Kalya Platform area, pre-industrial Hg concentrations are 23 ± 0.2 ng/g, increasing to 74 ng/g in modern surface sediment, and the Hg accumulation rate has increased from 1.0 to 7.2 μg/m²/a from pre-industrial to present, which overall represents a 6-fold increase in Hg concentration and accumulation. At the Nyasanga/Kahama delta region, pre-industrial Hg concentrations are 20 ± 3 ng/g, increasing to 46 ng/g in surface sediment. Mercury accumulation rate has increased from 30 to 70 μg/m²/a at this site, representing a 2–3-fold increase in Hg concentration and accumulation. There is a lack of correlation between charcoal abundance and Hg accumulation rate in the sediment cores, demonstrating that local biomass burning has little relationship with the observed Hg concentration or Hg accumulation rates. Examined using a sediment focusing-corrected mass accumulation rate approach, the cores have similar anthropogenic atmospheric Hg deposition profiles, suggesting that after accounting for background sediment concentrations the source of accumulating Hg is predominantly atmospheric in origin. In summary, the data document an increase of Hg flux to the Lake Tanganyika ecosystem that is consistent with increasing watershed sediment delivery with background-level Hg contamination, and regional as well as global increases in atmospheric Hg deposition.     

Attachment to the residential neighbourhood: a framework for analysis

There is an abundance of literature on attachment to the residential neighbourhood and satisfaction with it. Efforts to explain variation in such attachment emphasise the relevance of population characteristics to the neglect of factors affecting attachment which are external to the neighbourhood's population. This article suggests a wide framework for analysis. The suggestion is made that a hierarchy of neighbourhood contexts could be used in order to reach a more complete explanation and understanding of attachment and variation in it to the residential neighbourhood.     

Gallium and germanium in the metal and silicates of L- and LL-chondrites

Concentrations of Ga and Ge in the metal of 31 L-, 8 LL- and 2 H-chondrites, and in the silicates of 12 L- and LL-chondrites have been determined by spectrophotometric methods. The ranges of Ga contents in the metal of L- and LL-chondrites are 1.1–36.9 ppm and 1.0–34.1 ppm, respectively. The Ge content in the metal is positively correlated with Ga and ranges from 89.1–160 ppm, and 126–308 ppm for L- and LL-chondrites, respectively. The Ga content in the silicates of L-chondrites varies from 4.0 to 8.9 ppm.The Ga and Ge contents in the metal are clearly lower in unequilibrated than in equilibrated L- and LL-group chondrites. Unequilibrated (type 3 and 4) and equilibrated (type 5 and 6) chondrites are well separated in the plots of Ga vs Ge in the metal and the L- and LL-groups are also well resolved. The Ga and Ge in the metal are well correlated with petrologic grade. This suggests that Ga and Ge variations in the metal are related to thermal metamorphism. There is evidence of an enrichment of Ga in the metal due to shock-reheating.     

Direct observations of bipolar outflow from HM sagittae

We observed HM Sagittae with theMulti-Element Radio Linked Interferometer Network (MERLIN) at 6 cm and 18cm. We find non-thermal bipolar outflow in the eastwest direction, associated with optical emission lines, and thermal ridges to the north and south associated with the UV nebulosity detected by the HST.     

New merlin observations of OH/IR stars: OH357.31-1.33 and OH0.9+1.3

We present recent radio interferometer measurements of the OH 1612 MHz maser emission from the OH/IR sources OH0.9+1.3 and OH357.31 obtained with the enhanced MERLIN. Some preliminary results are briefly discussed. These results are part of an on-going observational campaign to obtain the best radio maps of bright OH/IR stars with MERLIN, VLA and VLBA, in order to understand the nature and dynamics of their circumstellar matter and evolution.