Environmental records of carbonaceous fly-ash particles from fossil-fuel combustion

Analysis of fly-ash particles in lake sediments has become increasingly important in studies of environmental pollution and lake acidification history. Most fly-ash studies have concerned black spheroidal carbonaceous particles (SCP)(>5 m) produced from oil and coal combustion. This review paper provides a summary of this technique and its application, and focusses on our investigations in Sweden between 1979 and 1993. It consists of five parts: i) preparation and analysis methods, ii) historical trends in atmospheric deposition, iii) geographical surveys of atmospheric deposition, iv) sediment dating, and v) studies of sedimentation processes in lakes. Methods for preparation and analyses of SCP have been developed and applied to investigations using sediment, soil and snow samples. Stratigraphic trends of SCP concentrations in lake-sediment cores reflect the consumption history of fossil fuels. A characteristic temporal SCP pattern, with a marked concentration increase beginning after the 1940's and a peak in the early 1970's, has been recognized in most Swedish lakes and elsewhere in Europe. A survey of SCP concentrations in surface sediments of >100 lakes covering Sweden demonstrated that polluted areas in southern Sweden had >100 times higher SCP concentrations than clean areas in the north. The spatial distribution of SCP over Sweden is similar to the deposition pattern of long-range transported airborne pollutants, such as excess sulphate monitored by network stations. SCP also accumulate in soils, and soil analyses can be used for determining the integrated historical deposition of SCP at the local or regional scale. Finally, SCP have been used for indirect dating of sediment cores and as a marker to assess sediment distribution patterns within lake basins.     

A method for the extraction of carbonaceous particles from lake sediment

The methods found in the literature for the extraction of carbonaceous particles from lake sediment are discussed. The technique used by Griffin & Goldberg (1975) on Lake Michigan sediments was improved by modifying the procedure to halve the extraction time and reduce the risk of fragmentation. This method was then applied to a sediment core taken from Loch Tinker in Western Scotland, which had previously been analysed using the Renberg & Wik method. Although the basic trends for both methods are the same, the new method is found to be more sensitive to low particle numbers and more accurate, due to a more efficient extraction and a higher magnification for microscope counting.     

A method for the selective removal of inorganic ash particles from lake sediments

Inorganic ash particles are formed by the fusing of inorganic material present during the high temperature combustion of fossil fuels. As they accumulate in lake sediments, they record the history of atmospheric contamination produced from such sources. A technique has been developed for concentrating these particles from lake sediments involving the stepwise removal of unwanted components of the sediment, including organic material and biogenic silica.When applied to a sediment core taken from Loch Tinker, central Scotland, a particle concentration profile, very similar to that of the carbonaceous particle profile (the other component of fossil-fuel combustion ash) is produced. The concentration of the inorganic ash spheres in the sediment is approximately an order of magnitude higher than the carbonaceous particles and there appears to be a continuous pre-industrial background value. This seems to imply a similar source (i.e. coal combustion rather than oil) for both inorganic ash and carbonaceous particles. This method has also been used with success on peat cores.     

Four thousand years of atmospheric lead pollution in northern Europe: a summary from Swedish lake sediments

This paper presents a large palaeolimnological study of the pre-industrial and industrial history of atmospheric lead pollution deposition in Sweden. Both lead concentrations and ²⁰⁶Pb/²⁰⁷Pb ratios have been analysed in 31 lakes covering most of Sweden, plus one lake in north-west Russia. Four of the lakes have varved (annually-laminated) sediments. Isotope analysis is a sensitive and effective method to distinguish pollution lead from natural catchment lead and to detect early pollution influence, because the ²⁰⁶Pb/²⁰⁷Pb ratio in unpolluted background sediments in Sweden was > 1.3, while that of lead from pollution, derived from ores and coal, was < 1.2. The sediments show a consistent picture of past temporal changes in atmospheric lead pollution. These changes include: the first traces of pollution 3,500-3,000 yrs ago; a pollution peak in Greek-Roman Times (about 0 AD); lower lead fall-out between 400 and 900 AD; a significant and permanent increase in atmospheric lead fall-out from about 1000 AD; an increase with the Industrial revolution; a major increase following World War II; the maximum peak in the 1970s; and decreasing fall-out over the last decades. The four varved sediments provide high-resolution records of atmospheric pollution. They reveal pollution peaks about 1200 and 1530 AD which match the history of metal production in Europe. According to the varve records the lead pollution level in the late 1990s had decreased beneath the level of the 1530s. The pollution level 1200 AD was about 35% of the 1980s, when lead pollution was still near its all time high. About 50% of the total accumulated atmospheric lead pollution deposition through time was deposited in the pre-industrial period. The sediments also show a consistent picture of the geographic distribution of atmospheric lead deposition over time, with higher deposition in south Sweden and declining levels to the north, which supports the hypothesis that the main sources of pre-industrial atmospheric lead pollution in Sweden were cultural areas in mainland Europe and Great Britain.     

A procedure for preparing large sets of diatom slides from sediment cores

A procedure is described for making diatom microscopy slides from large numbers of sediment samples, simultaneously. The method uses small sediment samples, small test tubes, small amounts of hydrogen peroxide, no decantings, no centrifuging, and it requires no washing-up of glassware. It is, therefore, fast, cheap, gentle to the diatoms and needs little fume cupboard space.     

Radiometric dating of recent lake sediments from a highly eroded area in semiarid Tanzania

Semiarid regions are vulnerable environments with a series of important and often discussed problems such as land degradation, water scarcity and desertification. These regions are dynamic and respond quickly to climatic and environmental changes. Unlike lakes in temperate zones, lakes in semiarid regions are yet poorly utilized as climatic and environmental indicators. In this study aquatic deposits are used to uncover the environmental history of a severely degraded area in central Tanzania. The ²¹⁰Pb and ¹³⁷Cs chronologies date a 360 cm long sediment sequence to 155 years. The sediments show that lake Haubi basin changed from a seasonally waterlogged depression to a lake at the turn of the century. Calculated sedimentation rates show that the catchment of the lake has been subject to varied and enhanced soil erosion during the last 155 years.     

A microwave digestion technique for the extraction of fossil diatoms from coastal lake and swamp sediments

This study provides an introduction to a microwave digestion technique for the extraction of fossil diatoms from sediments. The microwave technique is compared with the standard diatom extraction technique of Battarbee (Diatom analysis. In: Berglund B.E. (ed.), Handbook of Holocene Palaeoecology and Palaeohydrology. John Wiley and Sons) that uses a combination of dilute hydrochloric acid and hydrogen peroxide and the advantages and disadvantages of their use are discussed. The results suggest that the microwave technique is fast, inexpensive and most importantly produces replicable fossil diatom assemblage data. Small samples sizes are used (0.3 g) for the microwave method thus lower quantities of chemicals are required (6 ml), which significantly decreases the cost of sample processing. Our results show that the microwave digestion technique is a viable alternative that will produce similar results within a shorter period of time.     

Environmental changes during modern period from the record of Gaoyou Lake sediments, Jiangsu

Based on analysis of parameters of cores taken from Gaoyou Lake, including magnetic susceptibility, grain-size characteristics and sedimentary rate, environmental changes during the modern period were examined with the assistance of historical records and Gaoyou Lake water level materials. It is concluded that during the modern period a higher value of magnetic susceptibility and a lower sediment grain size coincided with a wet climate, while a lower value of magnetic susceptibility and a higher grain size were related with a dry climate. The results indicate that the climate in the 123 years period from 1880 to 2003AD can be divided into four stages: two low water level stages (1880–1915AD, 1948–1981AD) and two high water level stages (1915–1948AD, 1981–2003AD). It appears that the regional cli-mate generally underwent a dry–wet–dry–wet pattern in 30-year cycles. At present, it is at the end of a wet period, so the regional climate is expected to become dry in the near future. This conclusion corresponds with the climate records in the historical literature of the Gaoyou area, and it also matches with the climatic changes in North Jiangsu area.     

近现代高邮湖沉积记录的环境变化

1 Introduction Gaoyou Lake is the third largest lake in Jiangsu Province. It lies in central Jiangsu Province, lower reaches of the Huaihe River, and west of the Jing–Hang (Beijing–Hangzhou) Grand Canal. Previous research on environmental changes of the…     

Environmental changes during modern period from the record of Gaoyou Lake sediments,Jiangsu

Based on analysis of parameters of cores taken from Gaoyou Lake, including magnetic susceptibility, grain-size characteristics and sedimentary rate, environmental changes during the modern period were examined with the assistance of historical records and Gaoyou Lake water level materials. It is concluded that during the modern period a higher value of magnetic susceptibility and a lower sediment grain size coincided with a wet climate, while a lower value of magnetic susceptibility and a higher grain size were related with a dry climate. The results indicate that the climate in the 123 years period from 1880 to 2003AD can be divided into four stages： two low water level stages （1880-1915AD, 1948-1981AD） and two high water level stages （1915-1948AD, 1981-2003AD）. It appears that the regional climate generally underwent a dry-wet-dry-wet pattern in 30-year cycles. At present, it is at the end of a wet period, so the regional climate is expected to become dry in the near future. This conclusion corresponds with the climate records in the historical literature of the Gaoyou area, and it also matches with the climatic changes in North Jiangsu area.     

贵州麦岗水库沉积物的矿物磁性特征及其土壤侵蚀意义

对取自贵州西南部紫云县麦岗水库的沉积物柱芯MG1-1进行了包括SIRM、ARM、χlf、χfd、IRM-20mT和IRM-100mT等磁性参数的矿物磁性测量,并计算了ARM/SIRM、HIRM和IRM-100mT/SIRM。根据沉积物的这些矿物磁性特征,并结合137Cs、粒度、TOC、C/N分析结果,推测了麦岗水库流域在1960～2007年(47年)间的土壤侵蚀变化情况。研究表明:麦岗水库流域的土壤侵蚀强度变化虽然存在一些波动,但整体上呈现由强到弱到强再到弱的变化过程。结合降水资料和土地利用/土地覆被变化情况,探讨了影响土壤侵蚀变化的主要原因。结果表明,降水量对流域土壤侵蚀变化的影响不大,而人类活动,特别是土地利用的变化可能是引起流域土壤侵蚀变化的主要原因。     

Climate change inferred from aeolian sediments in a lake shore environment in the central Tibetan Plateau during recent centuries

Studies of the past climate variation on the Tibetan Plateau(TP) are currently limited in number and low in density and temporal resolution. We investigated the climate condition from about 400 years before present(B.P.) in the central TP at the shore of Co(means "lake") Nag using aeolian sediments. A 2.7-m sand profile with 57 sediment samples and six optically stimulated luminescence(OSL) samples were studied through grain-size analysis, geochemical elements and parameters, and depositional rate estimation. A previous assumption was verified that sand deposition at the shore of Lake Co Nag originated from hills to the east. Two significant wet periods between 90–140 and about 380 years B.P. were indicated by the variation of element profiles and sediment depositional rates. Aeolian activity is sensitive to variations from different seasonal changing patterns of climate factors in the study area, and aeolian sediments respond differently to climate conditions during the cold little ice age(LIA) and the warm 20 th century. Present day dry seasons of winter and spring might be much warmer and drier compared to seasons of 400 years ago although summer precipitation has increased, resulting in significantly more aeolian activity and higher depositional rate(about 6 times compared to 380–240 years ago) of sandy sediments. Aeolian problems like blown-sand deposition and desertification may be worse in a projected warming future in the central TP as well as other cold and high altitude regions. Our results suggest an agreement with environmental evolution during the little ice age and the 20 th century in a broader scale on the TP.     

New palaeomagnetic result from Vendian red sediments in Cisbaikalia and the problem of the relationship of Siberia and Laurentia in the Vendian

A palaeomagnetic study of Vendian red sediments from the Lena River section on the western margin of Lake Baikal in the region of Cisbaikalia (54°N, 108°E) has isolated a stable remanence with direction D = 296.3°, I = −27.7° (high-temperature component) and a corresponding pole of 2.7°S, 168.2°E. The primary nature of this remanence is confirmed from a positive fold test, dual polarities and the presence of detrital haematite. This result, together with all late Precambrian–Early Cambrian palaeomagnetic data from Siberia, indicates that Siberia occupied low latitudes during that time. It has been proposed on the basis of palaeomagnetic data that Laurentia occupied high latitudes during the Vendian, so it would appear that there cannot have been any Laurentia–Siberia connection at that time. A review of Vendian to Cambrian Laurentian palaeomagnetic data shows that such an interpretation is ambiguous. An alternative interpretation places Laurentia in low latitudes and confirms the Laurentia–Siberia fit of Hoffman (1991 ) and Pelechaty (1996 ). However, the lack of Late Vendian palaeomagnetic data for Siberia still allows the possibility that it could have occupied high latitudes during that time.     

A high resolution proxy-climate record from an arctic lake with annually-laminated sediments on Devon Island, Nunavut, Canada

Sediments from a 3 ha lake (75 °34.34N, 89 °18.55W) from the coastal region of northern Devon Island, Nunavut, Canada, contain discrete laminations in the deepest part of the basin. The laminations are varves as indicated by the correspondence between counts and thickness measurements of the couplets and ²¹⁰Pb dating. A 14 cm core representing 150 years of sedimentation contained laminated couplets consisting of a lighter inorganic layer with a higher percentage of calcium and magnesium, alternating with fine darker bands, typically more cohesive, and comprising higher proportions of silica and carbon. A reddish oxidation zone with higher iron and aluminum frequently separates the laminations. The dark layer represents a biogenic component deposited in summer and is made cohesive by bacterial filaments among the other particles. The light inorganic layer represents clastic deposition from allochthonous sources. Deposition rates were relatively consistent through the core with an increase in varve thickness in the 1950s. Diatom concentrations in the sediments increased by two orders of magnitude in this century, with major increases in the 1920s and 1950s. The increase in varve thickness and diatom abundance coincides with an increase in summer melt percentage in an ice core from the Devon Island Ice Cap (Koerner, 1977). The relatively high sedimentation rate (0.15 cm yr^-1) coupled with the consistency of deposition makes this lake a significant indicator for recent climate changes of the Canadian Arctic Archipelago.