Structural variations in derivatives of the bacteriochlorophylls of Chlorobiaceae: impact of stratigraphic resolution on depth profiles as revealed by methanolysis

Bacteriochlorophylls c and d, recovered from two sedimentary sequences, were converted to bacteriophaeophorbide methyl esters by methanolysis and analysed by atmospheric pressure chemical ionisation liquid chromatography-multistage mass spectrometry (APCI LC-MSⁿ). The distributions in both settings, a moderately consolidated sediment from Kirisjes Pond, Antarctica, and in a finely laminated microbial mat from Les Salines de la Trinitat, Spain, show significant variations within a narrow depth interval. The overall bacteriophaeophorbide c to d ratios in the two sediments are different, as are the ratios of particular C-3¹ diastereoisomers, indicating distinct differences between the bacterial communities that contributed to each sediment. Furthermore, a shift towards more extensive alkylation in homologues within each sediment is consistent either with changing environmental conditions in the depositional environments, or development-related changes in the structure of the bacterial community, leading to increased competition for light or nutrients.     

Geochronology of anthropogenic pollutants in riparian wetland sediments of the Lippe River (Germany)

Anthropogenic pollutants were determined in a dated sediment core, collected from a riparian wetland of the Lippe River (Ruhr district, Germany). The historical trend in heavy metals, polycyclic aromatic hydrocarbons, organochlorines, polychlorinated biphenyls and linear alkylbenzenes as well as more recent contaminants such as industrial additives, organotins, synthetic musks, methyltriclosan and some other compounds were determined for the time period between 1930 and 1986. Emission sources, information on technical production and usage, as well as on the individual pollution pathways, with appropriate environmental stability, were considered in the interpretation of the sediment contamination over the past 50 years.Contaminants were analysed and interpreted according to two different criteria: (a) the origin of the main contaminants as related to mining and industrial activities as well as municipal sewage and agricultural effluents and (b) the pollution history. Due to a significant appearance of formerly missing contaminants in sediments deposited since 1970, we suggest classifying contaminants as either common (predating 1970) or modern (postdating 1970).In summary, the study provided a comprehensive reconstruction of the pollution history of the Lippe River system.     

Pollution history and recovery of a boreal lake exposed to a heavy bleached pulping effluent load

We examined the effects of heavy pulp mill discharges on the Lake Lievestuoreenjärvi ecosystem and the later recovery of diatom and chironomid communities from age-dated short core samples. Beginning in 1927 the lake received a heavy effluent load from a sulphite pulp mill. Except for the recession during the Second World War and the temporary closure of the mill from 1967 to 1971, the industrial load, containing large quantities of nutrients, organic matter and toxic compounds, increased continuously. In the early 1980s, laboratory documents were falsified by the directors of the mill and the systematic illegal effluent overload led to a collapse of the whole lake ecosystem. In 1985, the outdated plant was finally closed down. Based on the assessment of chemical properties and biological remains of the sediment, we distinguished five developmental phases in the ecological state of the lake. In the pre-industrial phase, the pelagic and profundal benthic communities were dominated by species preferring ultraoligotrophic or oligotrophic lakes. Concomitant with the increasing discharge and deposition of chlorine compounds, resin acids, and mercury, as well as strong acidity and hypolimnetic and epilimnetic anoxia, the ecological status changed in a short period from excellent to bad. Finally, in the early 1960s, the majority of the lake was virtually dead and the aquatic life survived only in the uppermost littoral zone. Since 1985, a fast recovery in the water quality has led to a strong, but temporary eutrophy in pelagic communities. The main peak of eutrophication was caused by the invasion of a species new to the lake,Aulacoseira granulata var.angustissima. Later, the pelagic communities shifted towards oligotrophy, but the original, pre-industrial status has not been re-established. The profundal benthic communities have not achieved the pre-industrial structure, but at present indicate mesotrophy.     

Rainfall thresholds for landsliding in the Himalayas of Nepal

Landsliding of the hillslope regolith is an important source of sediment to the fluvial network in the unglaciated portions of the Himalayas of Nepal. These landslides can produce abrupt increases of up to three orders of magnitude in the fluvial sediment load in less than a day. An analysis of 3 years of daily sediment load and daily rainfall data defines a relationship between monsoonal rainfall and the triggering of landslides in the Annapurna region of Nepal. Two distinct rainfall thresholds, a seasonal accumulation and a daily total, must be overcome before landslides are initiated. To explore the geomorphological controls on these thresholds, we develop a slope stability model, driven by daily rainfall data, which accounts for changes in regolith moisture. The pattern of rainfall thresholds predicted by the model is similar to the field data, including the decrease in the daily rainfall threshold as the seasonal rainfall accumulation increases. Results from the model suggest that, for a given hillslope, regolith thickness determines the seasonal rainfall necessary for failure, whereas slope angle controls the daily rainfall required for failure.