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Colin Neal

Publications and source records attributed to Colin Neal.

At least 19 recordsLinked to original sources
PubMed2006

Chlorophyll-a in the rivers of eastern England.

Chlorophyll-a concentration variations are described for two major river basins in England, the Humber and the Thames and related to catchment characteristics and nutrient concentrations across a range of rural, agricultural and urban/industrial settings. For all the rivers there are strong seasonal variations, with concentrations peaking in the spring and summer time when biological activity is at its highest. However, there are large variations in the magnitude of the seasonal effects across the rivers. For the spring-summer low-flow periods, average concentrations of chlorophyll-a correlate with soluble reactive phosphorus (SRP). Chlorophyll-a is also correlated with particulate nitrogen (PN), organic carbon (POC) and suspended sediments. However, the strongest relationships are with catchment area and flow, where two straight line relationships are observed. The results indicate the importance of residence times for determining planktonic growth within the rivers. This is also indicated by the lack of chlorophyll-a response to lowering of SRP concentrations in several of the rivers in the area due to phosphorus stripping of effluents at major sewage treatment works. A key control on chlorophyll-a concentration may be the input of canal and reservoir waters during the growing period: this too relates to issues of residence times. However, there may well be a complex series of factors influencing residence time across the catchments due to features such as inhomogeneous flow within the catchments, a fractal distribution of stream channels that leads to a distribution of residence times and differences in planktonic inoculation sources. Industrial pollution on the Aire and Calder seems to have affected the relationship of chlorophyll-a with PN and POC. The results are discussed in relation to the Water Framework Directive.

Agriculture↗
PubMed2006

Nitrate concentrations in river waters of the upper Thames and its tributaries.

The spatial and temporal patterns of in-stream nitrate concentrations for the upper Thames and selected tributaries are described in relation to point and diffuse sources for these rural catchments. The rivers associated with catchments dominated by permeable (Cretaceous Chalk) bedrock show a smaller range in nitrate concentrations than those associated with clay and mixed sedimentary bedrock of lower permeability. The differences reflect the contrasting nature of water storage within the catchments and the influence of point and diffuse sources of nitrate. Nitrate concentrations often increase in a gradual way as a function of flow for the rivers draining the permeable catchments, although there is usually a minor dip in nitrate concentrations at low to intermediate flow due to (1) within-river uptake of nitrate during the spring and the summer when biological activity is particularly high and (2) a seasonal fall in the water table and a change in preferential flow-pathway in the Chalk. There is also a decrease in the average nitrate concentration downstream for the Kennet where average concentrations decrease from around 35 to 25 mg NO(3) l(-1). For the lower permeability catchments, when point source inputs are not of major significance, nitrate concentrations in the rivers increase strongly with increasing flow and level off and in some cases then decline at higher flows. When point source inputs are important, the initial increase in nitrate concentrations do not always occur and there can even be an initial dilution, since the dilution of point sources of nitrate will be lowest under low-flow conditions. For the only two tributaries of the Thames which we have monitored for over 5 years (the Pang and the Kennet), nitrate concentrations have increased over time. For the main stem of the Thames, which was also monitored for over 5 years, there is no clear increase over time. As the Pang and the Kennet river water is mainly supplied from the Chalk, the increasing nitrate concentrations over time clearly reflect increasing nitrate concentrations within the groundwater. It primarily reflects long-term trends for agricultural fertilizer inputs and significant aquifer storage and long water residence times. The results are discussed in terms of hydrogeochemical processes and the Water Framework Directive and are compared with data from other eastern UK rivers. The importance of diffuse sources of nitrate contamination is highlighted. On a flow weighted basis, the average diffuse component of nitrate is around 95% for the Thames Basin rivers draining Chalk and for the corresponding rivers draining less permeable strata, there is a more significant but not major point source component (at least in terms of flux); the average diffuse component is 79% in this case. These data fit well with earlier assessments of agricultural sources to UK surface waters. Under baseflow conditions the diffuse sources remain dominant for the Chalk fed Thames Basin rivers, but point sources can be dominant for the low permeability cases. On a proportionate basis, the Thames Basin rivers are similar to the rural rivers of the Tweed and Humber Basins in terms of percentage diffuse components although the lower intensity agriculture occurring for the rivers monitored means that the average nitrate concentrations are lower for the rural rivers of central and northern England and the borders with Scotland: the Humber and Tweed.

Agriculture↗
PubMed2005

The water quality of the River Thame in the Thames Basin of south/south-eastern England.

The water quality of the River Thame, a tributary of the River Thames in the Thames basin, is described in relation to point and diffuse contaminant inputs and runoff from permeable and impermeable bedrock geology with their own characteristic water quality. The data is examined to see if the market town of Aylesbury in the upper part of the catchment influences water quality. Previous studies highlighted the influence of Aylesbury sewage treatment works (STW) on soluble reactive phosphorus (SRP) concentrations in the river before and after phosphorus (P) stripping at the STW. Variations in water quality along the river are described and the study indicates that, apart from SRP, water quality determinants seem to be relatively unaffected by Aylesbury. The Thame water quality is compared with other catchment typologies and it is very similar to that of the main stem of the Thames even though the Thames is mainly Chalk groundwater fed. Differences in water quality largely link to the amount of STW effluent within the rivers and to the endmember compositions of the groundwater and near surface water sources.

Anions↗
PubMed2005

River water quality of the River Cherwell: an agricultural clay-dominated catchment in the upper Thames Basin, southeastern England.

The water quality of the River Cherwell and a tributary of it, the Ray, are described in terms of point and diffuse sources of pollution, for this rural area of the upper Thames Basin. Point sources of pollution dominate at the critical ecological low flow periods of high biological activity. Although the surface geology is predominantly clay, base flow is partly supplied from springs in underlying carbonate-bearing strata, which influences the water quality particularly with regards to calcium and alkalinity. The hydrogeochemistry of the river is outlined and the overall importance of urban point sources even in what would normally be considered to be rural catchments is stressed in relation to the European Unions Water Framework Directive. Issues of phosphorus stripping at sewage treatment works are also considered: such stripping on the Cherwell has reduced phosphorus concentrations by about a factor of two, but this is insufficient for the needs of the Water Framework Directive.

Agriculture↗
PubMed2005

Sewage-effluent phosphorus: a greater risk to river eutrophication than agricultural phosphorus?

Phosphorus (P) concentrations from water quality monitoring at 54 UK river sites across seven major lowland catchment systems are examined in relation to eutrophication risk and to the relative importance of point and diffuse sources. The over-riding evidence indicates that point (effluent) rather than diffuse (agricultural) sources of phosphorus provide the most significant risk for river eutrophication, even in rural areas with high agricultural phosphorus losses. Traditionally, the relative importance of point and diffuse sources has been assessed from annual P flux budgets, which are often dominated by diffuse inputs in storm runoff from intensively managed agricultural land. However, the ecological risk associated with nuisance algal growth in rivers is largely linked to soluble reactive phosphorus (SRP) concentrations during times of ecological sensitivity (spring/summer low-flow periods), when biological activity is at its highest. The relationships between SRP and total phosphorus (TP; total dissolved P+suspended particulate P) concentrations within UK rivers are evaluated in relation to flow and boron (B; a tracer of sewage effluent). SRP is the dominant P fraction (average 67% of TP) in all of the rivers monitored, with higher percentages at low flows. In most of the rivers the highest SRP concentrations occur under low-flow conditions and SRP concentrations are diluted as flows increase, which is indicative of point, rather than diffuse, sources. Strong positive correlations between SRP and B (also TP and B) across all the 54 river monitoring sites also confirm the primary importance of point source controls of phosphorus concentrations in these rivers, particularly during spring and summer low flows, which are times of greatest eutrophication risk. Particulate phosphorus (PP) may form a significant proportion of the phosphorus load to rivers, particularly during winter storm events, but this is of questionable relevance for river eutrophication. Although some of the agriculturally derived PP is retained as sediment on the river bed, in most cases this bed sediment showed potential for removal of SRP from the overlying river water during spring and summer low flows. Thus, bed sediments may well be helping to reduce SRP concentrations within the river at times of eutrophication risk. These findings have important implications for targeting environmental management controls for phosphorus more efficiently, in relation to the European Union Water Framework Directive requirements to maintain/improve the ecological quality of impacted lowland rivers. For the UK rivers examined here, our results demonstrate that an important starting point for reducing phosphorus concentrations to the levels approaching those required for ecological improvement, is to obtain better control over point source inputs, particularly small point sources discharging to ecologically sensitive rural/agricultural tributaries.

Agriculture↗
PubMed2005

Nutrient hydrochemistry for a groundwater-dominated catchment: the Hampshire Avon, UK.

The patterns in nitrate and phosphorus sources, loads and concentrations in a groundwater-dominated lowland catchment, the Hampshire Avon, are examined and water quality signatures are used to identify a typology of headwater stream types. The major separations in water quality are linked to geology and groundwater chemistry as modified by the impacts of point source sewage effluents. The water quality of the major tributaries and the main stem of the River Avon are linked to the relative contributions of these source types, the impact of further direct effluent inputs to the main channel and in-stream processing. The tributaries and main stem of the Avon act as net sinks for total reactive phosphorus (TRP). Low concentrations of TRP were found in the Chalk groundwater and the groundwater system acts as an efficient buffer, removing and retaining TRP from water draining from the catchment surface into the aquifer. Thermodynamic analysis of calcium carbonate (CaCO3) solubility controls indicates that this natural 'self-cleansing mechanism' system within the groundwater may be directly linked to CaCO3-P co-precipitation within the aquifer matrix.

Calcium Carbonate↗
PubMed2005

Phosphorus concentrations in the River Dun, the Kennet and Avon Canal and the River Kennet, southern England.

Variations in phosphorus (P) concentrations in an agriculturally impacted river draining a Chalk aquifer and an associated canal in the west of the Thames Basin, southern England are examined and linked to agricultural and sewage sources and within river/canal process controls. The study area comprises the River Dun, the adjacent River Kennet and the Kennet and Avon (K&A) Canal. Large seasonal variations are observed for soluble reactive phosphorus (SRP) and dissolved silicon (Si) with low concentrations in the spring and summer times when biological activity is high. The K&A Canal shows the largest SRP and Si concentration declines. This reflects high biological activity coupled with higher temperatures and higher water residence times. The extent of SRP removal is examined in relation to organic (uptake/release with phytoplankton growth/decay) and, to a lesser extent, inorganic (SRP coprecipitation with calcite) mechanisms. Boron (B) is used as a tracer of sewage sources. Agricultural inputs of both dissolved and particulate P (PP) can be important particularly under conditions where the catchment is wet and near surface/overland flow is important: sewage treatment works effluent and septic tank discharges to groundwater also probably provide a major component of the SRP occurring within the water column. The canal, and to a lesser extent the river, acts as sink for P in sewage effluent sources due to the high biological activity especially during the spring and summer. The aquifer probably acts as a major sink for agricultural and septic tank inputs of P.

Agriculture↗
PubMed2005

The water quality of the River Carnon, west Cornwall, November 1992 to March 1994: the impacts of Wheal Jane discharges.

In January 1992, there was a major pollutant event for the River Carnon and downstream with its confluence to the River Fal and the Fal estuary in the west Cornwall. This incident was associated with the discharge of several million gallons of highly polluted water from the abandoned Wheal Jane tin mine that also extracted Ag, Cu and Zn ore. Later that year, the Centre for Ecology and Hydrology (CEH; then Institute of Hydrology) Wallingford undertook daily monitoring of the River Carnon for a range of major, minor and trace elements to assess the nature and the dynamics of the pollutant discharges. These data cover an 18-month period when there remained major water-quality problems after the initial phase of surface water contamination. Here, a summary is provided of the water quality found, as a backdrop to set against subsequent remediation. Two types of water-quality determinant grouping were observed. The first type comprises the determinants B, Cs, Ca, Li, K, Na, SO4, Rb and Sr, and their concentrations are positively correlated with each other but inversely correlated with flow. This type of water-quality determinant shows variations in concentration that broadly link to the normal hydrogeochemical processes within the catchment, with limited confounding issues associated with mine drainage. The second type of water-quality determinant comprises Al, Be, Cd, Ce, Co, Cu, Fe, La, Pb, Pr, Nd, Ni, Si, Sb, U, Y and Zn, and concentrations for all this group are positively correlated. The determinants in this second group all have concentrations that are negatively correlated with pH. This group links primarily to pollutant mine discharge. The water-quality variations in the River Carnon are described in relation to these two distinct hydrogeochemical groupings.

Alum Compounds↗
PubMed2003

Land Ocean Interaction: processes, functioning and environmental management: a UK perspective.

The hydrochemical and physical functioning of UK river basins, estuaries and coastal waters through to the open sea are outlined in relation to British environmental research over the last ten or more years. An overview of a considerable body of published work is presented in the context of current findings and future research challenges. This is linked to this special issue of Science of the Total Environment 'Land Ocean Interaction: processes, functioning and environmental management: a UK perspective' for which this contribution provides a conclusion.

Ecosystem↗
PubMed2003

Water quality fluxes for eastern UK rivers entering the North Sea: a summary of information from the Land Ocean Interaction Study (LOIS).

Over the past decade a major initiative examined the chemical flux transfers from eastern UK Rivers to the North Sea as part of an ambitious community research programme, the Land Ocean Interaction Study (LOIS). In this paper, a compilation of data on flux and flux per unit area for five major river basins, the Tweed, the Wear, the Humber, the Great Ouse and the Thames is presented based on an extensive riverine monitoring programme within the LOIS. The compilation includes details on the fluxes of major, minor and trace elements as well as the nutrients and sediments. In the process, the flux inputs are related to the major tributary sources for these basins and compared with earlier studies based on complementary information for eastern UK Rivers entering the North Sea collected within the Harmonized Monitoring Scheme. The significance of the southern Humber Rivers to pollution fluxes to the North Sea is highlighted in relation to the predominance of urban and industrial sources.

Journal Article↗
PubMed2003

Land-ocean interaction: processes, functioning and environmental management from a UK perspective: an introduction.

This paper provides a foreword to a special edition of Science of the Total Environment concerned with land-ocean interaction from a UK perspective as linked to processes, functioning and environmental management. The volume structure is presented together with an outline of the nature of the individual papers. The areas covered are: (1) freshwater chemistry, (2) riverine sedimentology, (3) tidal river, estuarine and coastal chemistry, (4) estuarine and coastal sediments and (5) shelf-sea-ocean linkages. The foreword provides as an introductory link to the broader perspectives of contemporary UK research in this area, which comes in a conclusions paper at the end of the volume.

Conservation of Natural Resources↗
PubMed2003

Soluble reactive phosphorus levels in rainfall, cloud water, throughfall, stemflow, soil waters, stream waters and groundwaters for the Upper River Severn area, Plynlimon, mid Wales.

Soluble reactive phosphorus (SRP) data are presented for rainfall, cloud water, soil waters, stream waters and groundwaters at the Plynlimon catchments in mid Wales to examine the hydrochemical functioning of inorganic phosphorus for an acidic and acid sensitive area characteristic of much of the UK uplands. In general, stream water concentrations are low compared to lowland areas. Average concentrations of SRP in rainfall and cloud water (0.3 and 0.9 microM l(-1), respectively) are higher than in stream water with wider ranges in concentration (0-19.3 and 0-20.9 microM l(-1), respectively). Throughfall and stemflow is enriched in SRP compared to rain and cloud water by a factor of approximately twofold and sixfold, respectively: the average concentrations and ranges are 0.73 and 0-6.61 microM l(-1) for throughfall and 2.12 and 0-18.61 microM l(-1) for stemflow. Soil water SRP concentrations measured in the surface layers of representative areas of podzol and gley soils, are further enriched with respect to inputs. Average concentrations and ranges for the L/F and Oh horizons in the podzols are 3.1 microM l(-1) (range: 0.03-17.2 microM l(-1)) and 0.75 microM l(-1) (range: 0.03-2.64 microM l(-1)), respectively. Correspondingly, the average values and ranges for the L/F and Oh horizons in the gley are 2 microM l(-1) (range: 0.03-16.65 microM l(-1)) and 0.4 microM l(-1) (range: 0.03-8.61 microM l(-1)). SRP concentrations in stream and ground water are lower than in atmospheric inputs and surface soil waters and show marked spatial variability. This variability is linked to three catchment features. (1) For streams draining podzolic soils, most of the SRP is retained by the catchment. For this situation, stream and ground waters have average concentrations of approximately 0.05 microM l(-1) with a range of 0-1.47 microM l(-1). There is no clear stream or groundwater SRP response to felling despite a large release of SRP from felling debris (brash) and the forest floor (L/F horizon) with average post-felling concentrations of 11.02 microM l(-1) (0.40-155.0 microM l(-1)) and 23.60 microM l(-1) (0.26-172.23 microM l(-1)), respectively. (2) For forested catchments with gley soils, stream water SRP concentrations are more variable with, in one case, much higher concentrations than for the podzol counterparts (range in average 0.05-0.46 microM l(-1)). (3) For the streams draining gley soils, felling results in a mixed SRP response. At the local scale (ditch drainage), there is a marked enrichment in SRP concentration (average concentrations increase from 0.05 to 1.31 microM l(-1), with a peak concentration of 4.0 microM l(-1)). This response is consistent with the observed mobilisation of SRP from brash and forest floor material (post-felling mean concentrations of 9.39 and 11.94 microM l(-1), respectively). However, stream water concentrations are an order of magnitude lower than observed in the soil waters implying considerable immobilisation of SRP between the soils and the stream. At the larger catchment scale, no discernable enrichment in SRP is observed following felling. The results are related to input-output budgets and the findings interpreted in terms of the dominant hydrogeochemical processes operative and environmental management issues.

Environmental Monitoring↗
PubMed2003

Nitrogen in rainfall, cloud water, throughfall, stemflow, stream water and groundwater for the Plynlimon catchments of mid-Wales.

An extensive study of acidic and acid sensitive moorland and forested catchments in mid-Wales is used to show the water quality functioning with respect to nitrate and ammonium. For this, long-term records of rainfall, cloud water, throughfall, stemflow and stream water (up to 18 years of weekly data) are combined with shorter duration information on stream water associated with small tributary sources and drainage ditches, ground water from a network of exploratory boreholes and paired control and felled catchments. The ratio of nitrate to ammonium is about one in rainfall, cloud water, throughfall and stemflow but the concentrations are much lower in rainfall (approximately 25 microM l(-1)) than in cloud water (approximately 300 microM l(-1)) while throughfall and stemflow are intermediate (approximately 80 microM l(-1)). Within the streams draining moorland and forested areas, nitrate concentrations are close to the mean value in rainfall while ammonium concentrations are often over an order of magnitude lower in the stream than in rainfall and are typically only about a fifth that of nitrate. With felling, stream water nitrate concentrations increase for podzolic soils but show a variable response for gley soils. For the streams draining forested podzols, the concentrations of nitrate can be up to an order of magnitude higher for the first few years after felling compared to than pre-fell values but in later years, concentrations decline to pre-fell and even lower levels. Felling for the podzolic soils barely leads to any changes in ammonium concentration. For the gley soils, felling results in an order of magnitude increase in nitrate and ammonium for a small drainage ditch, but the pulse barely reaches the main stream channel. Rather, within-catchment and within-stream processes not only take up the nitrate and ammonium fluxes generated, but in the case of nitrate, concentrations with- and post-felling are lower than pre-felling concentrations. Groundwater concentrations of nitrate for the moorland and forested catchments are slightly lower than for the streams while for ammonium the reverse is the case: ammonium concentrations in groundwater are about a tenth those of nitrate. With felling, groundwater nitrate concentrations show sporadic increases. For two boreholes, these increases occur during wet periods when groundwater levels are at their shallowest; for one other borehole, there is a gradual and sustained increase over several years. The results are explained in relation to the dominant hydrogeochemical processes operative.

Environmental Monitoring↗
PubMed2003

Dissolved beryllium in rainfall, stream and shallow groundwaters in the Upper River Severn catchments, Plynlimon, mid Wales.

This paper examines the temporal changes in dissolved beryllium in deposition (rainfall and cloud water), stream water and groundwater for the upper River Severn catchments at Plynlimon in mid-Wales. There are two main themes to the study. Firstly, time series records are examined to see if anomalous behaviour occurred during 1996, when remarkably high concentrations were unexpectedly observed in the UK lowland rivers (Neal, Sci Total Environ, 2003). The results show (a) Beryllium concentrations in rainfall and stream water remained low throughout the period (mean 0.02 and 0.07 microg l(-1) in rainfall and stream water, respectively) and were often less than the lowest quotable value for a single determination (0.05 microg l(-1)). (b) Beryllium concentrations in the streams declined between 1983 and 1996 from a mean of approximately 0.07 to a mean of 0.04 microg l(-1). This was followed by a brief increase in the autumn of 1995 (up to values of approx. 0.2 microg l(-1) and a more sustained increase to approximately 0.12 microg l(-1) from 1997 to the end of monitoring late in 1998. (c) Rainfall concentrations of Beryllium were indistinguishable from zero throughout most of the monitoring period although concentrations increased late in the study in line with patterns observed in the stream when concentrations averaged approximately 0.08 microg l(-1). (d) Beryllium concentrations are much lower than observed in the UK lowlands where concentrations as high as 29 microg l(-1) were recorded. For the exceptionally high values occurring in the lowlands, there was the potential for environmental damage to aquatic organisms such as fish at levels greater than approximately 1 microg l(-1). There are no potential problems for the upper River Severn. Secondly, while Neal et al., [J Hydrol, 136 (1992) 33-49] provided information on the hydrogeochemistry of beryllium in the upper River Severn using available information at that time (rainfall, cloud water, stemflow, throughfall and stream water), there was no information available on groundwater chemistry. Since the publication of Neal et al. [J Hydrol, 136 (1992) 33-49], such information is now available and this paper makes up this shortfall. The results show that beryllium concentrations in groundwater are typically approximately 2-3 times higher than those found within the streams (mean 0.14 microg l(-1), range 0.06-1.56 microg l(-1)). This feature probably reflects the increased leaching of beryllium from the bedrock. The findings presented in this study combined with the earlier information of Neal et al. [J Hydrol, 136 (1992) 33-49] are used to provide an overview on dissolved beryllium for the upper River Severn, the most complete and extensive record for the UK.

Animals↗
PubMed2003

Dissolved and acid available particulate beryllium in eastern UK surface waters.

The concentrations of beryllium (Be) in surface waters are presented for major water quality surveys of eastern UK rivers, based on extensive work within a major environmental programme, the Land Ocean Interaction Study (LOIS). Two measurements were made, one for dissolved Be (i.e. the fraction that can pass through 0.45-microm membrane filters) the other for acid available total Be (dissolved Be plus the fraction of particulate Be that can be leached by a 1% v/v concentrated nitric acid solution). Dissolved Be concentrations are generally less than 1 microg l(-1) with a mean of approximately 0.02 microg l(-1), but higher values occur across the eastern UK rivers between 16th October and 7th November 1995 under neutral to alkaline conditions where Be would not be expected to be mobile. The higher values vary from river to river and there is a marked increase from north to south with particularly high concentrations (up to 29 microg l(-1)) for the industrial and urban impacted rivers of the southern Humber basin. The results show a major increase in dissolved Be at a time of exceptional drought conditions and climate instability, which seems to be linked to industrial/urban catchment systems. The average dissolved Be flux is 0.22 gha(-1) year(-1) with a range in mean across the sites of 0.08-0.45 gha(-1) year(-1). Without the period of enhanced Be concentrations, the Be flux through the period would have been approximately 40% less. There is no clear distinction between the dissolved Be flux for the rural and urban/industrial catchment systems. Acid available particulate Be (AAPBe) concentrations are low across the eastern UK rivers, they range between 0 and 1.33 microg l(-1) with a mean of 0.02 microg l(-1) and the highest concentrations occur for the industrial/urban rivers (approximately twice the levels occurring within the rural rivers). The AAPBe concentrations are linearly correlated with the concentrations of suspended sediment, particulate organic carbon, particulate nitrogen, particulate phosphorus, and the AAP for several transition metals (Al, Co, Cr, Fe, Mn, Ni and Y), and the lanthanides. This reflects the nature of the catchment sources of particulate material (soil erosion and pollutant sources) and the hydrogeochemistry of Be with the high potential for hydrolysis and hydrogen bonding due to its small atomic size and high surface charge density. The acid available particulate flux averages approximately 0.42 gha(-1) year(-1) with a range in mean across the sites of 0.14-1.2 gha(-1) year(-1). The highest flux occurs for a river with a flood plain contaminated by spoil from historic mining of lead-zinc deposits, but there is no clear separation between the rural and the industrial/urban impacted catchments. The results indicate a potential and most unexpected dissolved Be stress to lowland aquatic environments, a stress that might well increase over time for the UK given the increasing climate instability within the country. The findings are linked to other information on Be in surface waters for other UK surface waters, including previously unpublished data, to allow a broader perspective for UK riverine environments. Information is provided on Be levels in acidic upland streams in mid Wales (upper River Severn), other eastern UK rivers (collected towards the end of the LOIS initiative) and drainage waters from a disused tin wine in Cornwall (Wheal Jane Mine).

Journal Article↗
PubMed2003

Fluoride in UK rivers.

Fluoride concentrations in eastern UK rivers (the Humber, Tweed, Wear, Great Ouse and Thames) are described based on information collected within the Land-Ocean Interaction Study (LOIS) and by the Environment Agency (EA) of England and Wales. The results show varied fluoride concentrations across the region, with a range from <0.01 to >10 mg l(-1); and mean, median and range in mean concentrations of 0.30, 0.21 and 0.05-3.38 mg l(-1) (excluding one outlier point), respectively. Within the main rivers and tributaries, the mean fluoride concentration varied from approximately 0.5 to over 2 mg l(-1) and the highest values occurred within the Don basin (Don, Dearne and Rother) and parts of the Trent basin (upper Tame and mid-upper Derbyshire Derwent) in highly industrialised and urbanised areas (Sheffield and Rotherham in the Don basin; Birmingham and Derby on the Trent). For localised inputs to the rivers, fluoride concentrations were slightly higher, and considerably higher in one outlier case. Correspondingly, the other rivers examined typically had mean fluoride concentrations between approximately 0.2 and 0.5 mg l(-1), but fluoride concentrations were lower in the headwater areas. As there is much less information on fluoride levels in upland areas, extensive data collected as part of an acid waters survey are used to show that fluoride concentrations are generally less than 0.1 mg l(-1) for the upland UK. The data are summarised in terms of both fluoride concentrations and flux, and the values are cross-referenced to other determinands collected within LOIS. The high positive correlation with boron and negative correlation with flow show the importance of point source (sewage) inputs of fluoride, while strong positive correlations between fluoride and barium indicate the relative importance of vein mineralisation in the bedrock in supplying fluoride to the waters of the Yorkshire Ouse and its tributaries. There seems to be some process that limits the fluoride concentrations within the more contaminated rivers, and this is indicated by a negative upper bound between fluoride and calcium. The waters are undersaturated with respect to fluorite and oversaturated with respect to calcium fluoro-phosphates. This upper bound may reflect either physical controls, such as the availability and size of point and diffuse sources for fluoride coupled to mixing of these sources with rain and soil runoff of low concentration, or solubility controls for a pure or mixed-phase mineral that cannot be specified here.

Journal Article↗
PubMed2002

Modelling long-term stream acidification in the chemically heterogeneous Upper Severn catchment, Mid-Wales.

A two-box version of the long-term acidification model MAGIC is applied to the Upper Severn catchment, Mid-Wales. Comparison between modelled output and the observed stream- and groundwater chemistry points to the limitations of modelling, due to the inherent complexity and variability in the catchment hydrology, soils, geology and chemistry. The MAGIC model is used to produce long-term hind- and forecast predictions of average stream-, soil- and groundwater chemistry, and to simulate long-term changes in sulfate and nitrate deposition, in line with current proposals of reduction. Changes in flow-routing pathways between soil- and groundwater are simulated and the long-term effects on streamwater quality noted. The use of a long-term acidification model enabled the simulation of streamwater quality under these different case scenarios. However, the modelled output is insensitive to depositional and flow routing changes, indicating that catchment processes are not being represented to a sufficient degree. Changes in simulated output as a result of increased acidic deposition are not statistically significant, lying within the variance of long-term observed data. Simulated changes in flow routing suggest a lack of model sensitivity, in terms of the effect on stream chemistry. The need for large amounts of measured data to ensure correct model representation of the hydrology, chemistry and the heterogeneous/variable nature of upland catchments is outlined. It is vital that these long-term data are available to ensure that problems do not arise due to over-reliance by catchment managers on potentially unreliable modelled output.

Acid Rain↗