High resolution time series of lead and zinc in sediments of Lake Constance

Sediments in Lake Constance have been dated by radiometric methods and lamination counting. Investigations into the concentrations of lead and zinc in the sediments were carried out to get detailed information about environmental history. Maximum concentrations were found at the beginning of the 1960's. The lead maximum contamination occurred 3 years before the zinc maximum and has an unidentified source. The use of coal, leaded gasoline or the remobilization within the sediment could be excluded to result in the lead maximum. The fluctuations in zinc contamination could be explained with increasing and decreasing pollution (industry, coal burning, building of sewage plants). The greatest fluctuations of both metals occur during periods of great change in the economic history of Germany.     

The Flood in the Odra River 1997 – Impact of Suspended Solids on Water Quality

The flood in the Odra river in 1997 has led to considerable additional pollution of the Stettin Lagoon and the Baltic Sea with contaminated suspended solids. For some priority substances, the pollutant entries via suspended solids during the flood period are estimated to be approximately 1/3 of the usual annual load. Among these priority pollutants there are total organic carbon (TOC), nitrogen, and the heavy metals Cu, Pb and Zn. For the concentrations of the priority pollutants in suspended solids accumulation factors from 2 to 4 in the comparison with normal conditions were observed. On the basis of the analysis of sediments sampled after the flood, main sources of the pollutants should be evaluated. As reference area with an industrial background as well as a typical pollutant pattern the region around Glogow/Legnica is proposed.     

The last 40 ka tephrostratigraphic record of Lake Ohrid,Albania and Macedonia: a very distal archive for ash dispersal from Italian volcanoes

A 1075 cm long core (Lz1120) was recovered in the south-eastern part of the Lake Ohrid (Republics of Macedonia and Albania) and sampled for identification of tephra layers. Magnetic susceptibility investigations show rather high magnetic values throughout the core, with peaks unrelated to the occurrence of tephra layers but instead to the relative abundance of detrital magnetic minerals in the sediment. Naked-eye inspection of the core allowed us to identify of two tephra layers, at 896–897 cm and 1070–1075 cm. Laboratory inspection of the grain-size fraction > 125 μm allowed for the identification of a third cryptotephra at 310–315 cm. Major element analyses on glass shards of the tephra layers at 896–897 cm and 1070–1075 cm show a trachytic composition, and indicate a correlation with the regionally dispersed Y-3 and Y-5 tephra layers, dated at ca 30 and 39 cal ka BP. The cryptotephra at 310–315 cm has a mugearitic–benmoreitic composition, and was correlated with the FL eruption of Mt. Etna, dated at 3370 ± 70 cal yr BP. These ages are in agreement with five ¹⁴C AMS measurements carried out on plant remains and macrofossils from the lake sediments at different depths along the core.     

Late Quaternary lake response to climate change and anthropogenic impact: biomarker evidence from Lake Constance sediments

This study used organic matter in oligotrophic Lake Constance (southern Germany) to reconstruct lake environment and to disentangle the multiple factors, such as climate change and human impacts, which influence sedimentation in large lakes. A sediment core from Upper Lake Constance, which represents 16,000 years of Late Glacial and Holocene lake history, was analysed for organic biomarkers, hydrogen index and elements calcium, strontium, and magnesium. Magnetic susceptibility was measured to establish a high-resolution stratigraphic framework for the core and to obtain further information about changes with respect to relative allochthonous versus autochthonous sedimentation. Dinosterol—a biomarker for dinoflagellates—and calcium have low concentrations in Younger Dryas sediments and consistently high concentrations between 10,500 and 7,000 cal. years BP. These variations are attributed to changes in lake productivity, but are not reflected in the proportion of total organic carbon within the sediment. During the Younger Dryas and between 6,000 and 2,800 cal. years BP, concentrations and accumulation rates of land-plant-derived C₂₉-steroids (β-sitosterol, stigmastanol and stigmasterol), in combination with a relatively low HI, indicate periods of enhanced terrigenous input to the lake. For the Younger Dryas, higher runoff can be attributed to a cold climate, leading to decreased vegetation cover and increased erosion. After 6,000 cal. years BP, high terrestrial input may be explained by enhanced precipitation. Biomarker and HI results, in combination with archaeological studies, raise the question as to whether lakeshore settlements affected sedimentation in Upper Lake Constance between 6,000 and 2,800 cal. years BP.     

Recent anthropogenic impact in ancient Lake Ohrid (Macedonia/Albania): a palaeolimnological approach

Ancient lakes, which are important centres of biodiversity and endemism, are threatened by a wide variety of human impacts. To assess environmental impact on ancient Lake Ohrid we have taken short sediment cores from two contrasting site locations, comprising a site of urban pollution and an apparently pristine area. Recent impacts on water quality and ecology were assessed using sediment, geochemical, ostracode, and diatom data derived from analysis of two ²¹⁰Pb-dated sediment cores spanning the period from 1918 to 2009. According to the index of geoaccumulation, sediments were often moderately contaminated with As. Fe and Ni concentrations often exceeded reported maximum limits above which harmful effects on sediment-dwelling organisms are expected. Productivity in the (pristine) south-eastern part of Lake Ohrid (Sveti Naum) is generally lower than in the north, probably due to the strong influence of spring discharge. Low ostracode and diatom concentrations, low abundance of the epilimnetic diatom Cyclotella ocellata, and low values of TOC and TIC indicate a lower productivity from the early 1920s to the late 1980s. Since the mid 1970s, increased relative abundance of C. ocellata and increasing diatom concentration indicate increasing productivity in the south-eastern part. Rising numbers of ostracode valves and higher TIC and TOC contents in both sediment cores indicate an increase in productivity during the late 1980s. A slight increase in productivity near Sveti Naum continued from the early 1990s until 2009, witnessed by rising TC, TIC, and TOC content and a generally high number of ostracode valves and ostracode diversity. The area near the City of Struga (site of urban pollution) is also characterized by rising TOC and TIC contents and, furthermore, by increasing Cu, Fe, Pb, and Zn concentrations since the early 1990s. The recent reduction in the number of ostracode valves and ostracode diversity is probably caused by a higher heavy metal load into the lake. This suggests that living conditions for the endemic species in Lake Ohrid have become less favourable in the northern part of the lake, which might threaten the unique flora and fauna of Lake Ohrid.     

Quaternary coastline evolution of Lake Ohrid (Macedonia/Albania)

Lake Ohrid (between FYR of Macedonia and Albania), situated in an active tectonic region of the Balkanides, is characterized by N ?? S trending active faults. To reconstruct the Holocene shoreline evolution we investigated the coastline using sediment cores and geophysical methods to image sedimentary and tectonic structures. We revealed areas of differing sedimentation regimes. The plains north and south of the lake are dominated by clastic input related to climate variations and uplift/erosion, whereas the steep western and eastern margins are controlled by recent tectonics. Furthermore, no evidence for a much higher lake-level during the Holocene was found in the plains north and south of the lake, except rare temporary floodings. This is supported by mappings of the limestone cliffs around Lake Ohrid, which yielded no evidence for abrasional platforms or notches as indicators for past highstands.     

High-resolution210Pb dating of Lake Constance sediments: Stable lead in Lake Constance

Two sediment cores (BO90/13b and BO90/17b) from Lake Constance were investigated by-spectrometry for²¹⁰Pb,¹³⁴Cs,¹³⁷Cs,²⁴¹Am,²³⁴Th, and other members of the²³⁸U decay chain. The sediments were dated using the constant-flux model for²¹⁰Pb, and accumulation rates were determined. These range from 0.04 to 0.65g/cm ²/yr (BO90/13b) and 0.04 to 0.8g/cm ²/yr (BO90/17b), respectively. The mean accumulation rate amounts to 0.16g/cm ²/yr for both cores. The cores had already been dated by lamination counting and reconstruction of high-water events at the Limnological Institute at Constance, so that a very precise time scale was available. Both ages derived are in agreement within statistical error up to 1900, which means dating with the constant-flux model for²¹⁰Pb was confirmed up to that age. The position of the maxima of bomb cesium and americium confirm the stratigraphic and²¹⁰Pb datings. With²⁴¹Am a further radioactive isotope is available, which can, due to the half-life of²⁴¹Pu (t _1/2=14.4yr) be detected now by-spectrometry and can serve as an additional time indicator, the maximum being dated at 1963. By applying the various time scales, the depth profiles of stable lead and zinc of core BO90/13b were dated. Both heavy metals show a very significant maximum located beneath the layer of the maxima of bomb cesium and americium, showing that these maxima are older than those of the bomb isotopes. It is remarkable in this context that the maximum of zinc concentration occurs a little later than that of stable lead. Similar concentration profiles are observable in core BO90/17b and other, older sediment cores (CS6-CS10) on a transect across the lake. In contrast to a former assumption, the depth profile of stable lead in Lake Constance sediments does not reflect the anthropogenic gasoline lead emissions into the atmosphere for Germany, their maximum being dated at 1971.     

Reviving Ancient Water Tunnels in the Desert-Digging for Gold？

The water shortage in the Middle East is a well-known problem. The introduction of diesel operated pumps for irrigation has caused a severe drop in groundwater levels. At the same time the demand for groundwater is growing to alarming proportions. Alternative ways of groundwater supply and management need to be found to halt social and economical disaster in the future. Why not look at history？ Qanats are subterranean tunnels ancient civilizations built to access groundwater. The technique is a sustainable method of groundwater extraction. Throughout the Middle East some settlements still make use of these ancient systems. In the summer of 2000, a community rehabilitation of a qanat was executed International Center for Areas （ICARDA） and with support from the Agricultural Research in Dry international donors. The renovation served as a pilot community intervention within a participatory action research project aimed at evaluating the use of qanats in Syria. In a second stage of the project, the pilot was scaled up to a nation-wide survey of Syrian qanats in 2001. This resulted in qanat renovations on other sites executed in 2oo2 and 2oo3 with further international support. This paper compares the first pilot renovation with a recent qanat renovation that took place in Qarah, Syria.     

A 40,000-year record of environmental change from ancient Lake Ohrid (Albania and Macedonia)

Lake Ohrid is considered to be of Pliocene origin and is the oldest extant lake in Europe. A 1,075-cm-long sediment core was recovered from the southeastern part of the lake, from a water depth of 105 m. The core was investigated using geophysical, granulometric, biogeochemical, diatom, ostracod, and pollen analyses. Tephrochronology and AMS radiocarbon dating of plant macrofossils reveals that the sediment sequence spans the past ca. 39,500 years and features a hiatus between ca. 14,600 and 9,400 cal. year BP. The Pleistocene sequence indicates relatively stable and cold conditions, with steppe vegetation in the catchment, at least partial winter ice-cover of the lake, and oxygenated bottom waters at the coring site. The Holocene sequence indicates that the catchment vegetation had changed to forest dominated by pine and summer-green oak. Several of the proxies suggest the impact of abrupt climate oscillations such as the 8.2 or 4.0 ka event. The observed changes, however, cannot be related clearly to a change in temperature or humidity. Human impact started about 5,000 cal. year BP and increased significantly during the past 2,400 years. Water column mixing conditions, inflow from subaquatic springs, and human impact are the most important parameters influencing internal lake processes, notably affecting the composition and characteristics of the sediments.     

Constraints on paleowater dissolved loads and on catchment weathering over the past 16 ka from Sr/Sr ratios and Ca/Mg/Sr chemistry of freshwater ostracode tests in sediments of Lake Constance, Central Europe

Sr isotope and Ca/Mg/Sr chemical compositions of freshwater ostracode tests separated from a sediment core represent the last 16 ka of sedimentation in Lake Constance, Central Europe. The chemical evolution of the paleowater's dissolved load of Lake Constance was estimated by correcting the ostracode data for Ca/Mg/Sr fractionation due to biogenic calcification. Since the Late Pleistocene deglaciation, the Ca/Sr molar ratios of paleowaters increased systematically from about 100 (a near marine signature) to about 200. Ca/Mg molar ratios varied in the range of 1–25. The ⁸⁷Sr/⁸⁶Sr ratios indicate Late Pleistocene paleowater compositions of 0.7086–0.7091, significantly more radiogenic than present day waters (0.7085). Sr isotopes and Ca/Mg/Sr chemical data together show that weathering of Mesozoic evaporites consistently dominated the dissolved Sr load (80–90%). Carbonate and silicate weathering were less important (1–10%). Trends of Sr dissolved loads were therefore not related to Mg which was mainly mobilized by carbonate weathering. Biotite weathering was an important source of radiogenic Sr in the paleowaters. The short-term release (duration about 600–800 years) of radiogenic Sr during glacier retreat started 15.2 ka ago and was due to enhanced biotite weathering at the glacier base. Long-term release of radiogenic Sr was due to biotite weathering in glacial soils and silicate rocks, and has gradually declined since the Late Pleistocene/Holocene transition.