336 research outputs found
Diatom analysis of River Thames foreshore deposits exposed during the excavation of a Roman waterfront site at Pudding Lane, London. Report for the Department of Urban Archaeology, Museum of London
Eighty-seven diatom taxa including marine, brackish, and freshwater forms were identified from foreshore sediments accumulated against pre-AD 100 quay structures exposed during the excavation of an early Roman waterfront site in the city of London. The spectra indicate that the Roman port was probably established close to the tidal head of the river
The acidification of Scottish Lochs and the deprivation of critical sulphur loads from palaeolimnological data
A decade ago very little was known about acid lochs in Scotland. The implicit
assumption was that they were largely free from pollution. In recent years the position
has changed and we now have large bodies of data on the chemistry and biology of
upland lochs (Harriman et al. 1986, Maitland et al. 1987, Battarbee et al. 1988) and
clear evidence for the recent acidification of many sensitive sites (Flower and Battarbee
1983, Battarbee et al. 1985, Flower et al. 1987, Battarbee et al. 1988)
Palaeoecological evidence for the timing and causes of lake acidification in Galloway, South West Scotland
During the contract period sediment cores from six lakes, three with
non-afforested and three with partially afforested catchments, were
analysed to enable lake water acidity (pH) to be reconstructed over
approximately the past 200 years. The sites are all situated on granitic
rocks in the Galloway Hills of S.W. Scotland. The results of diatom
analysis show that five of the six lakes have become considerably more
acid over this time period and that the acidification process is mainly
independent of catchment afforestation effects. {210}^Pb dating of the
sediment shows that there has been little change in sediment accumulation
rates at sites with non-afforested catchments, but there has been significant increases in accumulation rate at afforested sites associated with
erosion caused by pre-planting catchment ploughing. Pollen analysis
indicates that no major vegetation change has occurred at the non-afforested
sites whilst trace metal analysis of L. Enoch (not funded by this contract)
shows elevated levels of Pb, Cu, and Zn 1n the upper, post 1800 sediments.
It is concluded that acid precipitation is the most likely cause of
acidification at these sites
Assessing the impact of diatom dissolution in biasing quantitative salinity reconstructions from saline lake sediments
Royal Society Water Acidification Project (SWAP) Palaeolimnology Programme
In September 1983 the Royal Society launched a 500000 GBP
research programme funded jointly by the Central Electricity
Generating Board and the National Coal Board to investigate
mechanisms of surface water acidification in Norway, Sweden,
and the United Kingdom. The Management Committee of the
programme identified palaeolimnology as a key area of
research and we were invited to submit an integrated
proposal that was aimed not only at tracing acidification
history at important sites but also at evaluating alternative
hypotheses for lake acidification in each of the three
countries. We were also encouraged to use as wide a range
of techniques as possible. The programme approved by the
Management Committee initially in June 1984 and finally in
December 1984 is summarised in the following pages. A number
of projects began on October 1st 1984 and all remaining
projects are scheduled to begin on April 1st 1985. The
programme will be completed by September 1988 when the final
results will be presented at an open discussion meeting
Rural sanitation in the Lough Erne catchment. History and influence on phosphorus loadings
This paper traces historical changes in the disposal of sewage
effluent from the non-sewered population of 3 sub-catchments or Lough
Erne, Ne Ireland, and considers the importance of effluent from these
areas as a source of phosphorus to the lake. A questionnaire survey
approach is used and the data gathered are compared to the results of a
similar survey of a small river catchment in Gloucestershire
Acid Lakes in the Galloway Uplands, South West Scotland: catchments, water quality and sediment characteristics
Reports of diminishing salmonid fisheries and increasing acidity of
lakes and streams in S.W. Scotland have attributed the cause to low pH
precipitation (Wright &Henriksen 1980) and afforestation
effects (Harriman & Morrison 1982). In 1981 we initiated a project with CEGB funding to examine the history of lakewater acidity in both afforested and unafforested catchments
in the Galloway uplands (see frontispiece). Analysis of diatom remains in
lake sediments is used to reconstruct lake pH change over the past 150
years at each site. Sediment chronology is provided by lead-210 dating
(Appleby & Oldfield 1978). Contemporary limnological data on water
quality and diatom communities has been collected over an annual cycle
(1981-82) to aid evaluation of the sedimentary data
Fly-ash particles in lake sediments: extraction and characterisation. Report to the CEGB
Fly-ash particles are produced by high temperature combustion of coal and oil. They are
dispersed widely in the environment, despite the presence of electrostatic precipitators on
coal-fired station chimneys
A review of liming as a technique for protecting salmonid fish populations in acidified surface waters
Liming is a common technique that has been used in many countries to raise the alkalinity
of acidified surface waters and alleviate some of the damaging effects of acidification on
salmonid fish populations.
The most common liming substance used is calcite, a calcium carbonate compound that is
relatively inexpensive, available in different particle sizes and dissolves relatively quickly.
It can be applied directly to streams or lakes or it can be applied to catchment soils. When
applied to catchment soils its effect can be long-lasting but it can cause significant
damage to those catchment plant and animal communities that are naturally adapted to
acidic conditions. When applied directly to surface waters its effect can be immediate but
applications need to be continuous or frequently repeated to counter downstream dilution
and loss.
For streams the most effective method is to use an automatic doser controlled by pHmeasuring sensors upstream and downstream of the doser to enable the exact quantity of
lime needed to be added to the water body. Although effective this is an expensive
method and one that needs to be maintained continuously for several years until the
critical load exceedance has been eliminated. An alternative or complementary method is
partial catchment liming by targeting water sources and selected wetlands to minimise
damage to catchment vegetation.
Liming can be very effective in restoring and protecting salmonid fish populations, but if
over-applied it can lead to unwanted increases in alkalinity and productivity that may
produce symptoms of eutrophication and unwanted changes in the composition of plant
and algal communities downstream
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