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1.
Pollution history and recovery of a boreal lake exposed to a heavy bleached pulping effluent load 总被引：4，自引：0，他引：4
Juhani Hynynen Arja Palomäki Jarmo J. Meriläinen Allan Witick Keijo Mäntykoski 《Journal of Paleolimnology》2004,32(4):351-374
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 In 1985, the outdated plant was finally closed down.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. 相似文献
2.
Jarmo J. Meriläinen Juhani Hynynen Arja Palomäki Keijo Mäntykoski Allan Witick 《Journal of Paleolimnology》2003,30(4):387-406
Sedimentary diatom frustules and chironomid remains, in addition to the chemical stratigraphy of 32 elements and organic pollutants such as resin acids, PCB, DDT and its metabolites, were studied from core samples taken from Lake Jyväsjärvi in Central Finland (64° 14 N, 25° 47 E). The sediment profile covered over 200 years, with the oldest samples representing a period of very low human interference. The town of Jyväskylä was established on the lake shore in 1837, and the lake received untreated municipal wastewater from the town up until, 1977. A paper mill started operations in 1872 and began discharging effluent into Lake Jyväsjärvi. In recent years this effluent loading has been reduced. Based on the biological and chemical properties of the sediment strata, five developmental phases were distinguished and named as follows: (1) a pre-industrial phase (approximately up until the 1860s); (2) a phase of early changes in the lake ecosystem (from the 1870s to ca. 1940s); (3) a phase of increasing eutrophication (from ca. 1950 to ca. 1965); (4) a phase of severe pollution (from ca. 1966 to the early-1990s); and (5) a phase of recovery, which proceeded more quickly during the late-1990s following long-term hypolimnetic aeration. It was estimated that the ecological status of the lake changed from good to moderate during the second phase. Due to the poor chemical status of the lake (including increased concentrations of harmful substances) and the pronounced changes in diatom and chironomid communities, the ecological status from 1950 to the early-1990s was classified as bad. The present ecological status, after a slow recovery of about 20 years, can be classified as moderate/poor. Chemical analysis of the sediment revealed that some elements (C, N, P, S, Ba, Cd, Cu, Fe, Pb, Ni and Zn) followed the known history of municipal waste water discharge into the lake, but Hg, Cr and persistent organic pollutants had different stratigraphies, and therefore mainly originated from other sources. Pronounced changes in profundal benthic communities (chironomids) started about 80 years later than those in diatoms, but later changes in chironomid assemblages were greater than those in diatoms. 相似文献
3.
Reliability testing, namely receiver autonomous integrity monitoring (RAIM), consists of statistical testing of least-squares residuals of observations, e.g., on an epoch-by-epoch basis aiming towards reliable navigation fault detection and exclusion (FDE). In this paper, classic RAIM and FDE methods are extended with testing of range-rate residuals to find inconsistent velocity solutions in order to contribute to the reliability of the system with special focus on degraded signal environments. Reliability enhancement efforts discussed include a Backward-FDE scheme based on statistical outlier detection and an iteratively reweighted robust estimation technique, a modified Danish method. In addition, measurement weighting assigned to code and Doppler observations is assessed in the paper in order to allow fitting a priori variance models to the estimation processes. The schemes discussed are also suitable in terms of computational convenience for a combined GPS/Galileo system. The objective of this paper is to assess position and velocity reliability testing and enhancement in urban and indoor conditions and to analyze the navigation accuracy conditions with high sensitivity GPS (HSGPS) tests. The results show the necessity of weighted estimation and FDE for reliability enhancement in degraded signal-environment navigation. 相似文献
4.
Olavi Sandman Jarmo Meriläinen Heikki Simola Juhani Hynynen Jaana Lahtinen Virpi Marttila Pasi Reinikainen 《Journal of Paleolimnology》2000,24(3):317-329
A short-core paleolimnological investigation was carried out to acquire knowledge of the recent history of Lake Pihlajavesi, Saimaa Lake complex, and define its natural state before cultural disturbances. In the natural state, with negligible human interference, the basin was oligotrophic and oxygen-rich. The bioproductivity in the littoral zone was low and the profundal benthic quality was good according to Wiederholm's Benthic Quality Index.Based on diatom analyses, no significant changes have taken place in the phytoplankton communities during the past decades. Sedimentary chironomid communities reveal, however, slight changes on profundal life in the Pihlajavedenselkä basin, near the main pollution sources, whereas there were no significant changes in the outer basin. Three stages could be distinguished in the pollution history of Pihlajavedenselkä: (1) 'The natural state' up until the 1960s, (2) 'the period of increasing loading' during the 1960s and 1970s, and (3) 'the recovery of the basin' during the past two decades.Untreated municipal waste water from the town of Savonlinna was partly responsible for the commencement of eutrophication in the Pihlajavedenselkä basin in the 1960s. The paper and pulp industry in Varkaus, some 40 kilometres upstream from Lake Pihlajanvesi, has also increased eutrophication, especially during the worst period of water quality in the 1960s and 1970s. More effective waste water purification has markedly reduced effluent loading and led to a general recovery of the area. Neverthless the effects of slight nutrient loading can still be seen, especially in littoral bioproductivity.Our paleolimnological data indicate that the present ecosystem will offer living conditions for the endemic Saimaa ringed seal population that are similar to those that existed prior to human disturbances. 相似文献
5.
Energetic Particle Fluxes during the Bastille Day Solar Eruption 总被引：2，自引：0，他引：2
We report on our observations of solar energetic particle fluxes of p, He, C, O, Ne, Mg, Si, and Fe ions measured by the Energetic and Relativistic Nucleon and Electron (ERNE) experiment associated
with the Bastille Day solar flare and coronal mass ejection (CME) on 14 July 2000. We observed two clear maxima of the Fe/O
ratio at the energies 8.5–15 MeV nucl−1. The first Fe/O maximum occurred ∼ 3 hours after the beginning of the particle event, and the second maximum ∼ 22 hours after
the first one at the arrival of the shock associated with the Bastille Day eruption. We also observed a change in the energy
spectrum of oxygen concurrent with a change in the direction of the interplanetary magnetic field at the start of the second
enhancement of the Fe/O ratio. We propose an interpretation of the particle event where observed interplanetary particle fluxes
are associated with two different particle sources near the Sun and in interplanetary space. We suggest that heavy ions observed
during the first period of the Fe/O enhancement were released when a coronal shock reached a magnetic foot point connected
to 1 AU. The second maximum of Fe/O occurred when spacecraft encountered Fe-rich material stored in magnetic field flux tubes
early in the event and was possibly reaccelerated by the interplanetary shock. 相似文献
6.
Jarmo J. Meriläinen Juhani Hynynen Arja Palomäki Pasi Reinikainen Anssi Teppo Kaj Granberg 《Journal of Paleolimnology》2000,24(3):251-270
The recent environmental history of Lake Lappajärvi in western Finland (63°00 N, 23°30 E, area 149 km2), a humic, brown water lake with an average phosphorus content of ca. 20 g l–1, was studied from short core sediment samples taken from the two main basins of the lake. Based on the stratigraphy of diatoms and chironomids and the sediment quality it was possible to distinguish four developmental stages during the past century: (1) a pre-industrial stage covering the time up to about 1935; (2) a stage of increasing nutrient loading (ca. 1936–1960); (3) a stage of pronounced erosion from lake level regulation and extensive ditching of the catchment area (ca. 1960–1970); and (4) a meso-eutrophic stage from ca. 1970 onwards.Acidophilous Aulacoseira distans coll. and other species typical of dystrophic, nutrient-poor lakes characterized the diatom assemblages during the first stage, and the profundal zoobenthic assemblages, characterized by Heterotrissocladius subpilosus and Micropsectra, indicated good hypolimnetic oxygen conditions and a low sedimentation of organic matter (approx. less than 50 g m–2 a–1). The increased loading rapidly led to changes both in diatoms and chironomids (e.g., to an early extinction of H. subpilosus in the 1950s). The process finally led to eutrophication with a successive proliferation of diatom species such as Asterionella formosa followed by Aulacoseira ambigua, Fragilaria crotonensis, and finally Melosira varians. The relative proportion of alkaliphilous species reached a maximum in the final stage and the original profundal chironomid fauna was replaced by Chironomus anthracinus gr. and C. plumosus which are typical of profundal areas suffering from temporal oxygen deficit. It is notable that the considerable decrease in waste water loading from the point sources (80–86% ) during the past two decades has not led to a recovery in the lake. This highlights the importance of diffuse loading from agriculture, forestry and other human activities even to this comparatively large lake. 相似文献
7.
The lead pollution history, based on the accumulation rate of total Pb and ratio of stable isotopes (206Pb/207Pb), was studied in the annually laminated sediment of a small lake in Finland (62°20′ N; 25°41′ E). The sediment chronology
based on varve counting provided a unique opportunity to explore and date signals of Pb emissions, including the ancient metallurgical
activities of the Roman Empire at the beginning of the Current Era. Changes in the ratio of stable isotopes gave a pronounced
signal of the atmospheric Pb fallout in AD 32–392, although this was not distinguishable in the accumulation rate of total
Pb, as it was observed in previous work. Calculated accumulations of the ancient pollution Pb were low, the highest values
being 0.2–0.3 mg m2 a−1 in AD 144–392, corresponding 14–21% of the accumulation of total Pb. The accumulation of pollution Pb collapsed in the fifth
century and remained at or close to the background level up to the eleventh century. After this, the accumulation rate of
pollution Pb began to increase and reached 1.2 mg m2 a−1 in AD 1420–1439, corresponding to 44% of the total Pb accumulation. During five centuries, from AD 1420–1895, the average
accumulation of pollution Pb was 2.6 mg m2 a−1, the variation being from 0.8 to 4.8 mg m2 a−1. The accumulation of Pb started to increase exponentially in the early twentieth century, and the highest accumulations of
pollution Pb (11–22 mg m2 a−1, corresponding 50–76% of the annual accumulation of total Pb) were dated to AD 1926–1985. The banning of the use of leaded
fuel has led to a pronounced decrease in the accumulation of pollution Pb since the 1980s, and the present accumulation rate
represents the level that prevailed 80–120 years ago. 相似文献
8.
Jarmo J. Meriläinen Virve Kustula Allan Witick Eeva Haltia-Hovi Timo Saarinen 《Journal of Paleolimnology》2010,44(2):531-545
In order to assess the importance of different pollution sources for the increase in element concentration and accumulation, historical changes in selected elements were studied in the annually laminated sediment of Lake Korttajärvi in Central Finland (62°20′N; 25°41′E). The sediment chronology based on varve counting (256 BC to AD 2005) provided a unique opportunity to explore and date signals of metal emissions, including the ancient metallurgical activities of the Roman Empire at the beginning of the Current Era. Records of this kind are mostly lacking in Finland and northernmost Europe. The stratigraphic sequence of element concentrations did not reflect any major changes in the lake, but changes in element accumulation rates provided distinct pollution signals caused by airborne fallout, catchment erosion, and to some extent municipal wastewater loading. The maximum bulk sedimentation recorded in the twentieth century was 11-fold and organic sedimentation 4-fold higher than the mean background sedimentation rate (256 BC to AD 1019). The increase in the accumulation rates of the majority of the elements, such as Cd, Sn, Pb, Si, Ni, B, Cu, Zn, Sr, Na, K, Sb, Ca, Cr, U and Mg, in descending order, was at least equal to that of bulk sedimentation or much greater, especially for Cd, Sn, and Pb. Changes in the accumulation of Co, Fe, Mn, Mo and As were small and mainly followed those of organic sedimentation. The earliest pollution signals were those of Pb recorded in AD 1055–1141. A weak signal of Pb pollution from the Roman Era was detected in metal concentrations, but this could not be confirmed by the accumulation rate data for Pb. 相似文献
9.
Numerical orbit integrations have been conducted to characterize the types of trajectories in the one-dimensional Newtonian
three-body problem with equal masses and negative energy. Essentially three different types of motions were found to exist.
They may be classified according to the duration of the bound three-body state. There are zero-lifetime predictable trajectories,
finite lifetime apparently chaotic orbits, and infinite lifetime quasi-periodic motions. The quasi-periodic orbits are confined
to the neighbourhood of Schubart's stable periodic orbit. For all other trajectories the final state is of the type binary
+ single particle in both directions of time. The boundaries of the different orbit-type regions seem to be sharp. We present
statistical results for the binding energies and for the duration of the bound three-body state. Properties of individual
orbits are also summarized in the form of various graphical maps in a two-dimensional grid of parameters defining the orbit.
Supported by the Academy of Finland. 相似文献
10.
The one-dimensional Newtonian three-body problem is known to have stable (quasi-)periodic orbits when the masses are equal. The existence and size of the stable region is discussed here in the case where the three masses are arbitrary. We consider only the stability of the periodic (generalized) Schubart's (1956) orbit. If this orbit is linearly stable it is almost always surrounded by a region of stable quasi-periodic orbits and the size and shape of this stable region depends on the masses. The three-dimensional linear stability of the periodic orbits is also determined. Final results show that the region of stability has a complicated shape and some of the stable regions in the mass-plane are quite narrow. The non-linear three-dimensional stability is studied independently by extensive numerical integrations and the results are found to be in agreement with the linear stability analysis. The boundaries of stable region in the mass-plane are given in terms of polynomial approximations. The results are compared with a similar work by Héenon (1977).We thank the referee for pointing out this reference to us. 相似文献