Paleoecological investigation of recent lake acidification in the northern Great Lakes states

Paleoecological analyses of sediments from nine northern Great Lakes states (NGLS) lakes reveal small pH changes in seven of these lakes since 1860, four of these being declines. The largest diatom-inferred (DI) pH declines of 0.5 pH units were found in Brown L. and Denton L., Wisconsin. Two other lakes with suspected total alkalinity declines (based on an acidification model and on historical water chemistry, respectively), McNearney L., Michigan, and Camp 12 L., Wisconsin, have not acidified recently according to diatom-inference techniques. Many of the observed trends of increasing pH are coincident with logging; floristic composition of diatom assemblages also changed coincident with fisheries manipulations in some lakes, but these floristic trends did not affect DI pH. Sediment core profiles of Pb, S, and polycyclic aromatic hydrocarbons provide a record of atmospheric deposition of fossil fuel combustion products beginning around the turn of the century; onset is later and accumulation rates are smaller than for other northeastern study regions of the Paleoecological Investigation of Recent Lake Acidification (PIRLA) Project. The response of diatom species to lakewater pH in the NGLS region is very strong and similar to response in other regions. Overall, there is little paleoecological evidence that acidic deposition has caused significant acidification of lakes in the NGLS region.This is the twelfth of a series of papers to be published by this journal which is a contribution of the Paleoecological Investigation of Recent Lake Acidification (PIRLA) project. Drs. D.F. Charles and D.R. Whitehead are guest editors for this series.     

Sources and chronology of fifteen elements in the sediments of lakes affected by metal deposition in a mining area

Sources and chronologies of metal contamination were studied in sediment cores of three lakes of the Rouyn-Noranda mining area (Québec, Canada) affected by atmospheric deposition of anthropogenic contaminants. One of the three lakes also received acid mine drainage. The sediments were dated using ²¹⁰Pb and ¹³⁷Cs and analysed for stable Pb isotope ratios and for total concentrations of 15 elements (Ag, Al, Au, Ca, Cu, Cd, Fe, Hg, Mn, Ni, P, Pb, S, Ti, Zn). Stable lead isotopic signatures helped to determine the quantitative contributions of different industrial Pb sources to our sampling sites. This source apportionment showed the dominant influence of the Rouyn-Noranda copper smelter in airborne Pb emissions for the decades following 1926, when industrialization began in the region. The smelter source had a low ratio of ²⁰⁶Pb/²⁰⁷Pb ranging between 0.90 and 1.05, as typical of the Abitibi Archean sulphides. The relationships between element (metal) sedimentary fluxes and anthropogenic Pb fluxes allowed us to infer the origin of the anthropogenic source. These relationships strongly suggest that the copper smelter was (and may still be) an atmospheric source of Cd, Cu, Pb, Zn, Ag and Hg to the surrounding lakes. Our study indicates that the efforts made by the Rouyn-Noranda copper smelter to reduce airborne emissions of metals have been translated in reduced atmospheric metal loadings to the surrounding lakes.     

Heavy metal concentrations in surficial sediments from Wadi El Natrun saline lakes, Egypt

Heavy metal concentrations of Wadi El Natrun saline lakes were investigated. Pb, Zn, Mn, Cu, Cd, Ni, Fe and Al were measured in surficial sediments. The heavy metal concentrations largely indicate the influence of weathering of terrigenous sources on land. In comparison with the average in sedimentary rocks, the concentrations of the heavy metals studied are higher than the global average sandstone. This is also reflected in the high enrichment factors. The heavy metal concentration in lakes II and III decrease in the order Pb > Zn > Cu, while in lake I the decreasing order is Cu > Zn > Pb. Sediments with microbial mats were found to concentrate heavy metals above background sediment values.     

Stratigraphy of total metals in PIRLA sediment cores

Sediment cores from 30 low-alkalinity lakes in northern New England (NE), New York (NY), the northern Great Lakes States (NGLS) of Minnesota, Michigan, and Wisconsin, and Florida (FL) have been dated by ²¹⁰Pb and analyzed for water and organic content, eight major elements (Al, Ti, Fe, Mn, Ca, Mg, Na, K) plus four trace metals (Pb, Zn, Cu, and V). Variations in the percentages of major elements through time are dominated by long-term independent variations in the abundance of SiO₂, FeO, and to a lesser extent Ca and Al. Additional variations are caused by varying proportions of inorganic matter. Major variations in chemistry are generally unrelated to documented distrubances in the watersheds; most disturbances are minor fires or selective logging.Accelerated accumulation of Pb from atmospheric sources into sediment first occurs in sediment dated between 1800 and 1850 in NY and NE, slightly later in the NGLS region, and about 1900 in FL. Modern accumulation rates in all areas are comparable (ca. 1 to 4 g cm^–2 yr^–1). Accumulation rates of Pb in some lakes have declined significantly from 1975 to 1985. Atmospheric deposition of anthropogenic Zn and Cu is also indicated by generally increasing accumulation rates in sediment cores, but the record is not as clear nor are chemical profiles in all lakes parallel to the trends in atmospheric emissions inferred on the basis of fossil fuel consumption, smelting, and other industrial activities. Inter-lake variations in profiles of Cu and Zn are large. Vanadium accumulation rates increase by the 1940s in NY and NE, but not until the 1950s in the NGLS region. This timing correlates with regional trends in the combustion of fuel oil, a major source of atmospheric V.Acidification of some of the lakes is suggested by decreases in the concentration and accumulation rates of Mn, Ca, and Zn in recent sediment, relative to other elements of catchment origin. The decreases generally occur slightly before the onset of acidification as indicated by diatoms. Increased sediment accumulation rates for Fe may indicate the acidification of watershed soils. The use of the accumulation rate of TiO₂ as an indicator of rates of erosion and for normalization of trace metal accumulation rates is in question for lakes where the flux of TiO₂ from the atmosphere varies and is a significant fraction of the total flux of TiO₂ to the sediment.This is the thirteenth of a series of papers to be published by this journal which is a contribution of the Paleoecological Investigation of Recent Lake Acidification (PIRLA) project. Drs. D. F. Charles and D. R. Whitehead are guest editors for this series.     

Isotope record of anthropogenic lead pollution in lake sediments of Florida, USA

We examined the anthropogenic lead (Pb) burden that accumulated in sediment of lakes in the southeastern USA during the last ~150 years. Mining, smelting, agriculture, and fossil-fuel combustion are known to have contributed to Pb pollution in lakes of other regions. Few studies, however, have examined Pb sequestered in lakes of the southeastern USA, particulary peninsular Florida, which is subject to less continental atmospheric influence than other regions of the eastern USA. We obtained sediment cores from Little Lake Jackson and Little Lake Bonnet in Highlands County, Florida and used Pb isotopes in the records to identify principal sources of Pb contamination. The sediment records showed that changes in Pb concentration and isotope ratios correspond temporally with gasoline consumption in the USA, as well as with changes in lead ores used to produce leaded gasoline. Lead concentrations in the study lakes showed temporal variations that were similar to those found in peat records from east-central Florida. Isotope trends were similar to the mean USA atmospheric Pb deposition record, and to Pb isotope records from Bermuda and Atlantic corals. We modeled the isotopic composition of the anthropogenic Pb in lake sediments and found that the overall trend is controlled by Pb that was released during leaded gasoline combustion. There is, however, additional Pb at each site that comes from sources that are not fully represented by the natural, background Pb. Lead isotope ratios and Pb/arsenic (As) ratios provide evidence that Pb deposition in lakes during the middle 1900s might have been influenced by lead arsenate applications to golf courses, a source that is often ignored in Pb isotope studies. Isotope evidence confirms, however, that following cessation of commercial lead arsenate use in the 1960s, atmospheric alkyl lead was again the primary influence on Pb in sediments of the study lakes.     

The Suitability of a South Pennine (UK) Reservoir as an Archive of Recent Environmental Change

The suitability of a south Pennine reservoir as an archive of recent industrial pollution (Pb deposition) and vegetation change was assessed by comparing the sediment record of Pb and pollen with a local blanket peat profile, and the modelled regional SO₂ deposition since 1840. The pollen-based record of vegetation change from the reservoir sediments was obscured by high inputs of eroded peat from the surrounding catchment. Total fluxes of Pb from the catchment into the reservoir varied between 0.05 and 2.67 kg km⁻² year⁻¹ during a 7 year period of increased peat erosion (1976–1984). The presence of concentration peaks in the Pb profile of the blanket peat may have been caused by changes in sulphide or redox chemistry within the peat profile. Large variations in influxes of Pb to the reservoir occurred during periods of increased peat erosion, suggesting the record of aerial pollution deposition has been obscured by terrestrial inputs. Extensive areas of blanket peat in the south Pennines have been subject to denudation, suggesting reservoirs in the region and other areas of high erosion and sediment flux are unsuitable for producing accurate records of the aerial deposition of pollen rain and Pb pollution. The ecological implications of highly variable fluxes of heavy metal contaminants from extensively eroded blanket bogs to ecosystems downstream are poorly understood.     

Paleoecological investigation of recent lake acidification in the Adirondack Mountains,N.Y.

Paleoecological analysis of the sediment record of 12 Adirondack lakes reveals that the 8 clearwater lakes with current pH < 5.5 and alkalinity < 10 eq l^-1 have acidified recently. The onset of this acidification occurred between 1920 and 1970. Loss of alkalinity, based on quanitative analysis of diatom assemblages, ranged from 2 to 35 eq l^-1. The acidification trends are substantiated by several lines of evidence including stratigraphies of diatom, chrysophyte, chironomid, and cladoceran remains, Ca:Ti and Mn:Ti ratios, sequentially extracted forms of Al, and historical fish data. Acidification trends appear to be continuing in some lakes, despite reductions in atmospheric sulfur loading that began in the early 1970s. The primary cause of the acidification trend is clearly increased atmospheric deposition of strong acids derived from the combustion of fossil fuels. Natural processes and watershed disturbances cannot account for the changes in water chemistry that have occurred, but they may play a role. Sediment core profiles of Pb, Cu, V, Zn, S, polycyclic aromatic hydrocarbons, magnetic particles, and coal and oil soot provide a clear record of increased atmospheric input of materials associated with the combustion of fossil fuels beginning in the late 1800s and early 1900s. The primary evidence for acidification occurs after that period, and the pattern of water chemistry response to increased acid inputs is consistent with current understanding of lake-watershed acidification processes.This is the second of a series of papers to be published by this journal which is a contribution of the Paleoecological Investigation of Recent Lake Acidification (PIRLA) project. Drs. D.F. Charles and D.R. Whitehead are guest editors for this series.     

Mine water-induced gradients in sediment metals and arcellacean assemblages in a boreal freshwater bay (Petkellahti, Finland)

Sediment chemistry and arcellacean community composition were analyzed to study the ecological effects of copper mine-derived acidic and metal-rich waters in a freshwater bay in eastern Finland. To track spatial and temporal changes in the bay, 32 mine-impacted (top) and pre-impact (bottom) samples were analyzed from 16 short sediment cores taken along a transect extending from the pollution source. In addition, short cores from the impacted and reference sites were studied. Recent sediments displayed a geochemical gradient from the inner bay, where mine water is discharged, to the outer bay. Inner bay sites were enriched with C, S, and Fe, whereas Mn was depleted, but has precipitated in the outer bay. Among the heavy metals, Cu, Al, Zn, and Ni concentrations had increased in the inner and mid bay, while Co and Cd concentrations had increased at mid-bay sites. The change from the natural to mine-impacted condition was also seen in faunal gradients. According to ordination and distance measures, the greatest changes in species composition occurred in the inner bay, with fairly small changes in the outer bay. Numerical methods suggested that metals (Cu, Pb, Al, Zn, Cr), redox-sensitive elements (Fe, Mn), organic carbon and nutrients could be related to changes in arcellacean assemblages. Geochemical changes in the impacted core started at ~20 cm with increases in S alternating with peaks in Cr and Mg. Heavy metal concentrations increased markedly at 10 cm, after the active mining period, suggesting the beginning of acid mine drainage. Geochemical changes at ~20 cm were already apparent in the arcellacean assemblages, but the most notable change coincided with the geochemical shift at 10 cm, with signs of decreased pH. Numerical methods suggest that mining-related metals Co, Cu, Zn and Ni co-vary with arcellaceans, but Al appears to behave independently with respect to the species data.     

Sediment Stratigraphy and Heavy Metal Fluxes to Reservoirs in the Southern Pennine Uplands, UK

Reservoir sediments are rarely used as environmental archives because of the potential for sediment disturbance by fluctuating water levels. However, rapid rates of sedimentation, proximity to urban centres and often the existence of management records, may make them potentially important resources for reconstructing recent, anthropogenically-derived environmental change. This project assesses the potential of reservoir sedimentary records for reconstructing past atmospheric and drainage basin fluxes of heavy metals (manganese, iron, nickel, copper, zinc and lead) in the southern Pennines, UK. Five reservoirs were selected on the basis of management history and drainage basin characteristics. Multi-parameter analysis showed sediments to be replicable across the ȁ8accumulating zone’ with reasonably consistent rates of sedimentation. Water level fluctuations were not found to detrimentally affect sediment records in the deepwater area of the reservoirs. In fact, spheroidal carbonaceous particle (SCP) profiles show trends in inputs that closely reflect major changes in industrialisation, indicating the reservoir sediments to be excellent records of particulate inputs. Only lead (Pb) and zinc (Zn) were significantly enriched in the reservoir sediment in comparison to background levels. Manganese (Mn), iron (Fe) and to a limited degree, copper (Cu), appeared to be affected by post-deposition mobility. Preliminary calculations of Pb fluxes indicate that over 80% of the current Pb input to the reservoirs is from Pb deposited onto drainage basin soils in the past, rather than from direct atmospheric deposition or natural background inputs. In Howden reservoir, for example, the total Pb flux to deepwater sediment cores in 2000 was 119 mg m⁻² a⁻¹. Of this, an estimated 99 mg m⁻² a⁻¹ was from anthropogenically-derived Pb, initially deposited onto drainage basin soils and subsequently entering the reservoir via erosion and leaching processes. There is, therefore, no indication that the flux of Pb to the aquatic system is declining in response to reductions in Pb deposition. The ecotoxicological effects of the high and continuing Pb flux to these reservoirs, despite recent decreases in atmospheric deposition, is an area requiring further investigation.     

松嫩平原杜蒙沙地地表物质的地化组成及风化特征

本文分析了杜蒙沙地表土样品各粒级组分（全样、>63 μm、63~30μm、30~11 μm和<11 μm）的常量元素组成。结果表明：杜蒙沙地地表物质化学元素组成以Si、Al为主,与上地壳相比,除Si、Mn和Ti外,Fe、Mg、Ca和P严重亏损,Al和Na中度亏损,K轻微亏损;除Si、Al、Na、K外,Fe、Mg、Ca、Ti、P、Mn的变异系数均很高;常量元素在不同粒级中的变化程度按照Al相似文献   

Past atmospheric Pb deposition in Lake Qinghai,northeastern Tibetan Plateau

Two short sediment cores were recovered from sub-basins of Lake Qinghai, China and were analyzed for concentrations of Pb and 16 other elements to determine historic, regional atmospheric Pb deposition on the Tibetan Plateau. Core chronologies, dating back to the eighteenth century, were established using activities of ²¹⁰Pb and ¹³⁷Cs. The 17 elements were divided into three principal components. Variations in concentrations of PC1 elements (Al, Cr, Cu, Fe, K, Mn, Ni, and Ti) demonstrate different patterns between the two cores, and are attributed to different sediment sources in the two sub-basins. PC2 elements (Ba, Ca, Na, and Sr) may be associated with the degree of catchment weathering and/or water chemistry. Four elements (Pb, Zn, P, and Co) are related to both PC1 and PC2, and reflect a mixture of natural and anthropogenic sources. The PC3 element is Mg in the north sub-basin, and is perhaps related to aragonite precipitation and/or increased farming. Elevated Pb concentrations in uppermost sediments of both cores signify a recent regional/global increase in anthropogenic Pb release into the environment. After subtracting lithogenic Pb, derived from rock weathering and/or dust and normalized to the background immobile element Ti, results suggest that excess, anthropogenic Pb is transferred to the lake and its sediments predominantly via the atmosphere. This anthropogenic atmospheric Pb is comparable in magnitude and displays similar variation patterns in the two cores, reflecting regional atmospheric deposition and local erosion. The average anthropogenic Pb deposition rate in Lake Qinghai since the 1960s has been ~12.2 ± 3.5 mg/m²/a, comparable with atmospheric Pb fluxes reported for sites elsewhere in the northern hemisphere.     

南极菲尔德斯半岛地区与拉斯曼丘陵地区湖泊水化学比较研究

为了解南极淡水生态系统的水化学特征，完成了拉斯曼丘陵地区１３个湖泊和菲尔德斯半岛１０个湖泊以及雪样的调查分析。西南极乔治王岛菲尔德斯半岛和东南极拉斯曼丘陵的气候条件不同，前者属于极地海洋性气候、气温不很低、湿润、风小、夏季较长；后者属于极地大陆性气候、气温低，冬天严寒、干燥、风大，夏季较短。因此，两地区的湖泊地貌、成因、发育、水生生物种群结构以及水化学状态存在较明显的差异，虽然水化学类型均比较单一，但矿化度却相差甚大。本文还对两区饮水水源进行了评价。     

庐山羊角岭红色泥砾泥石流成因质疑——与施雅风、邓养鑫商榷

作者根据庐山羊角岭红色泥砾的岩性特征,从地形和堆积物的宏观和微观特征进行分析研究,得出庐山有第四纪冰川。     

Heavy metal records in the sediments of Nanyihu Lake,China: influencing factors and source identification

In 2008, three short sedimentary cores were collected from Nanyihu Lake in the lower Yangtze River Basin using a gravity corer. Heavy metals, including Pb, Cu, Zn, Cr, Ni, Mn, and major elements, including Al, Fe, K, Na, Mg and Ti, were measured. Radionuclides, including ²¹⁰Pb and ¹³⁷Cs, were analyzed to date the sediments. The significant Mn enrichment in the uppermost sediments of the three cores did not influence the distribution of Pb, Cu, Zn, Cr and Ni. The Pb, Cu, Zn, Cr and Ni contents have increased over the past 30–40 years. The decline of ²⁰⁶Pb/²⁰⁷Pb ratios toward the surface indicated increasing anthropogenic Pb loading to the lake sediments. However, the heavy metal enrichment was low overall because of the high sediment accumulation rates and the low anthropogenic heavy metal flux into the Nanyihu Lake.     

Climatic implications of hydrologic changes in two lake catchments on the central Tibetan Plateau since the last glacial

The numerous and widespread lakes of the Tibetan Plateau (TP) constitute the largest group of alpine lakes on Earth. Some of the lakes are fed mainly by glacier meltwater and others by precipitation and groundwater. Past changes in the environments of these lakes differed because of differences in lake hydrological regimes and the complex pattern of climate change on the TP. Here we present records of scanning XRF, inorganic carbon (IC) concentration n-alkanoic acid average chain length (ACL) and percent aquatic inputs (Paq) in sediment cores from two non-glaciated lakes on the central TP (Dagze Co and Jiang Co), which span the past 19,000 years. We used these measures to investigate past changes in catchment hydrology, climate and environment. Variations in the concentration of Ti and other lithogenic elements at the two sites were influenced mainly by surface runoff, which is supported by the variation of IC, Ca/(Al, Ti, Fe) (reflecting authigenic carbonate precipitation), Rb/Sr (a chemical weathering proxy), and ACL and Paq. We attribute variations in surface runoff to changes in the precipitation/evaporation ratio, caused by the pattern of climate change on the central TP since the late Pleistocene. During the late Pleistocene, stronger runoff (indicated by higher Ti, higher Rb/Sr and Paq, lower IC, Ca/(Al, Ti, Fe) and ACL) likely resulted from lower temperatures. Lower runoff during the Holocene may reflect intensified evaporation caused by higher temperatures. Comparison with records from glaciated lakes in the region reveals opposite trends in catchment hydrology. Overall, our results suggest that since the late Pleistocene the central TP was influenced mainly by the Indian Summer Monsoon.     

Changes in diatom assemblages since pre-industrial times in 40 reference lakes from the Experimental Lakes Area (northwestern Ontario,Canada)

Diatom assemblages in recent versus pre-industrial sediments were examined in 40 relatively undisturbed lakes from the Experimental Lakes Area (ELA). The ELA region of northwestern Ontario receives low amounts of acidic deposition and the lakes have been minimally disturbed by watershed development or other human activities. Consequently, this region represents an important location to detect possible changes in lakes due to climate change. In over half of the lakes, planktonic taxa (especially Discostella stelligera) increased between 10 and 40% since pre-industrial times. Changes in diatom assemblages are consistent with taxa that would benefit from enhanced stratification and a longer ice-free season. We hypothesized that there should be a relationship between stratification and measured chemical and physical characteristics of the study lakes. Multiple correlation analysis was undertaken to see the relationship between planktonic taxa and D. stelligera since pre-industrial times and the physical and chemical characteristics of the study lakes. Lake depth was consistently identified as an important variable. The timing of the increase in planktonic taxa within cores from these lakes will be needed to rule out other possible regional changes that may also be occurring in the ELA region.     

A Holocene record of endogenic iron and manganese precipitation and vegetation history in a lake-fen complex in northwestern Minnesota

Little Shingobee Lake and Fen are part of the extensive network of lakes and wetlands in the Shingobee River headwaters of northwestern Minnesota, designed to study the interactions between surface and ground waters. Prior to about 11.2 cal. ka, most of these lakes and wetlands were interconnected to form glacial Lake Willobee, which apparently formed when a debris flow dammed the Shingobee River. Between 11.2 and 8.5 cal. ka, the level of Lake Willobee fell as a result of breaching of the dam, transforming the deep lake into the existing lakes and wetlands. Analyses of a 9-m core from Little Shingobee Lake (LSL-B), and lacustrine sediments under 3.3 m of peat in a 17-m core from Little Shingobee Fen (LSF-10), show that the dominant components are allogenic clastic material, and endogenic CaCO₃ and organic matter. In both cores almost all of the iron (Fe) and manganese (Mn) are incorporated in endogenic minerals, presumed to be X-ray amorphous oxyhydroxide minerals, that occur in significant quantities throughout the cores; almost no Fe and Mn are contributed from detrital aluminosilicate minerals. This suggests that, for most of the Holocene, the allogenic watershed contributions to lake chemistry were minor compared to the dissolved mineral load. In addition, prior to 3.5 cal. ka, pollen zone boundaries coincide with large changes in lake-sediment mineralogy, indicating that both landscape and climate processes were linked to early- and mid-Holocene lake chemistry. The pollen time series, with sequential domination by spruce, pine, sagebrush-oak, birch-oak and, finally, white pine is typical of the region and reflects the changing location of the prairie-forest transition zone over time. These changes in vegetation had some profound effects on the geochemistry of the lake waters.     

Compositional changes in sediments of subalpine lakes,Uinta Mountains (Utah): evidence for the effects of human activity on atmospheric dust inputs

Sediments in Marshall and Hidden Lakes in the Uinta Mountains of northeastern Utah contain records of atmospheric mineral-dust deposition as revealed by differences in mineralogy and geochemistry of lake sediments relative to Precambrian clastic rocks in the watersheds. In cores spanning more than a thousand years, the largest changes in composition occurred within the past approximately 140 years. Many elements associated with ore deposits (Ag, As, Bi, Cd, Cu, In, Mo, Pb, S, Sb, Sn, and Te) increase in the lake sediments above depths that correspond to about AD 1870. Sources of these metals from mining districts to the west of the Uinta Mountains are suggested by (1) the absence of mining and smelting of these metals in the Uinta Mountains, and (2) lower concentrations of most of these elements in post-settlement sediments of Hidden Lake than in those of Marshall Lake, which is closer to areas of mining and the densely urbanized part of north-central Utah that is termed the Wasatch Front, and (3) correspondence of Pb isotopic compositions in the sediments with isotopic composition of ores likely to have been smelted in the Wasatch Front. A major source of Cu in lake sediments may have been the Bingham Canyon open-pit mine 110 km west of Marshall Lake. Numerous other sources of metals beyond the Wasatch Front are likely, on the basis of the widespread increases of industrial activities in western United States since about AD 1900. In sediment deposited since ca. AD 1945, as estimated using ^239+240Pu activities, increases in concentrations of Mn, Fe, S, and some other redox-sensitive metals may result partly from diagenesis related to changes in redox. However, our results indicate that these elemental increases are also related to atmospheric inputs on the basis of their large increases that are nearly coincident with abrupt increases in silt-sized, titanium-bearing detrital magnetite. Such magnetite is interpreted as a component of atmospheric dust, because it is absent in catchment bedrock. Enrichment of P in sediments deposited after ca. AD 1950 appears to be caused largely by atmospheric inputs, perhaps from agricultural fertilizer along with magnetite-bearing soil.     

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.     

Phytate as a novel phosphorus-specific paleo-indicator in aquatic sediments

A reliable geochemical paleo-indicator for phosphorus remains elusive, despite the importance of understanding historical changes in the nutrient status of aquatic ecosystems. We assessed the potential of phytate (salts of myo-inositol hexakisphosphate) as a novel phosphorus-specific paleo-indicator by measuring its concentrations in dated sediments from an embayment in Helsinki, Finland, with a known 200-year history of trophic changes. Phytate was extracted in a solution containing sodium hydroxide and EDTA and detected by solution ³¹P NMR spectroscopy with spectral deconvolution. Concentrations varied markedly with sediment depth and paralleled previously determined changes in diatom assemblages and geochemical indicators linked to trophic status. In contrast, total sediment phosphorus did not reflect phosphorus inputs to the embayment, presumably due to the mobilization of inorganic phosphate under anoxic conditions during periods of high pollutant loading. Importantly, phytate appeared to be stable in these brackish sediments, in contrast to other organic and inorganic phosphates which declined abruptly with depth. We therefore conclude that phytate represents a potentially important indicator of historical changes in phosphorus inputs to water bodies, although additional studies are required to confirm its stability under conditions likely to be encountered in lakes and coastal ecosystems.