Have the bioavailabilities of trace metals to a suite of biomonitors changed over three decades in SW England estuaries historically affected by mining?

Many estuaries of southwest England were heavily contaminated with toxic metals associated with the mining of copper and other metals, particularly between 1850 and 1900. The question remains whether the passage of time has brought remediation to these estuaries. In 2003 and 2006 we revisited sites in 5 metal-contaminated estuaries sampled in the 1970s and 1980s — Restronguet Creek, Gannel, West Looe, East Looe and Tavy. We evaluate changes in metal contamination in sediments and in metal bioavailabilities in sediments and water to local organisms employed as biomonitors. We find that the decline in contamination in these estuaries is complex. Differences in bioavailable contamination in the water column were detectable, as were significant detectable changes in at least some estuaries in bioavailable metal contamination originating from sediments. However, in the 100 years since mining activities declined, bioavailable contamination has not declined to the regional baseline in any estuary affected by the mine wastes. The greatest decline in contamination occurred in the one instance (East Looe) where a previous industrial source of (Ag) contamination was considered. We used the macroalgae Fucus vesiculosus and Ascophyllum nodosum as biomonitors of dissolved metal bioavailabilities and the deposit feeders Nereis diversicolor and Scrobicularia plana as biomonitors of bioavailable metal in sediments. We found no systematic decrease in the atypically high Ag, Cu, Pb and Zn concentrations in the estuarine sediments over a 26 year period. Accumulated metal (Ag, As, Cu, Pb, and Zn) concentrations in the deposit feeders are similarly still atypically high in at least one estuary for each metal, and there is no consistent evidence for general decreases in sediment metal bioavailabilities over time. We conclude that the legacy of mining in sheltered estuaries of southwest England is the ongoing presence of sediments rich in metals bioavailable to deposit feeders, while dissolved metal bioavailabilities from this historical source alone are no longer atypically high.     

The application of regional geochemical reconnaissance surveys in the assessment of water quality and estuarine pollution

Preliminary studies on the application of regional, geochemical reconnaissance data, based on stream sediment sampling, to the assessment of water quality and estuarine pollution are encouraging. The use of the trace metal composition of tributary drainage sediments for the prediction of the upper limits of the trace metal concentration ranges in associated waters has been demonstrated, suggesting that the already available reconnaissance data may be a useful ancillary aid in the location of water monitoring sites in potential problem areas for potable water abstraction. The close association between the trace metal status of estuarine waters and sediments and their respective tributary drainage sediments allows the use of regional geochemical reconnaissance data in the selection of estuaries for aquaculture and other amenities.It must be emphasized that regional geochemical reconnaissance data, although a useful guide to the trace metal status of potable and estuarine waters, does require more detailed follow-up studies in selected areas. This is especially true for temporal studies to establish the seasonal variations in surface drainage systems. The present investigations in the United Kingdom involve areas of fairly well known characteristics and relatively small climatic and environmental scope; the extension of such studies to lesser known areas and regions of greater natural variations could well prove useful.     

Arsenic in stream sediments and waters of South West England

Past mining and smelting of arsenical and associated metalliferous ores in South-west England has led to widespread contamination of soils and surface drainage. The regional distribution of arsenic in both sediments and waters of tributary drainage shows anomalies in those areas underlain by mineralised granites and their metamorphic aureoles. High concentrations of arsenic in waters correspond with high concentrations in associated sediments. Detailed studies in three river systems illustrate the large degree of variation in arsenic values between individual sampling stations but confirm the relationship between sediments and waters. The work provides evidence of the potential use of geochemical reconnaissance surveys to water quality assessment.     

Clay mineral and heavy metal distributions in the lower estuary of Huelva and adjacent Atlantic shelf,SW Spain

The Huelva estuary, on the south-western Spanish Atlantic coast, is an environment strongly polluted by acid mine drainage and industrial effluents. Clay mineralogy, heavy metal and particle-size distribution in estuarine and adjacent shelf sediments have been analyzed in order to identify the sources and transport pathways of the contaminated sediments. The estuarine sediments consist of detrital terrigenous minerals (illite, kaolinite, quartz, feldspars, dolomite and heavy minerals) derived from river catchments and coastal erosion, with biogenic components (calcite and aragonite) and minor authigenic minerals (pyrite and possibly gypsum). Mineral distribution pattern in the estuary-shelf system is controlled by grain-size sediment, physico-chemical conditions of waters and hydrodynamic factors. Important proportions of fine-grained sediments highly enriched in sulphide-associated heavy metals are supplied by the Tinto-Odiel river system. Most of these sediments are trapped when river waters reach the estuary because of flocculation processes during estuarine mixing, thus the estuary acts as a storage basin for metallic pollutants. In terms of public health, this estuary is well above recommended safety guidelines for most metals. Although the shelf sediments show metal concentration levels close to background values, eventually, a metallic plume emerges from the estuary to ocean, and consequently elevated metal concentrations can be locally detected on the inner shelf.     

Changes in the distribution patterns of trace metals in sediments of the mersey estuary in the last decade (1974–1983)

A survey of the trace metal distribution in the sediments of Liverpool Bay, and the Dee and Mersey estuaries in 1972–1974 has been followed by a series of regular monitoring surveys in the Mersey estuary during the last 10 years. Over 15 000 individual observations have been recorded, including measurements of the trace metal content (cadmium, chromium, cobalt, copper, lead, manganese, mercury, nickel and zinc), organic carbon content and particle size distribution. In parallel with the physical and chemical measurements, a limited biological sampling programme has also been carried out.These results are discussed in relation to the spatial and temporal variability detected, and in relation to the potential biological effect of the sedimentary trace metals.     

Critical budget of metal sources and pathways in the Seine River basin (1994-2003) for Cd, Cr, Cu, Hg, Ni, Pb and Zn

River basin metal pollution originates from heavy industries (plating, automobile) and from urban sources (Paris conurbation: 2740 km(2), 9.47 million inhabitants). The natural sources of metal have been found to be limited due to sedimentary nature of this catchment and to the very low river sediment transport (10 t km(-2) y(-1)). Several types of data have been collected to build the metal budget within the whole Seine River basin: field surveys, economical statistics and environmental models. Environmental contamination and related fluxes have been measured on atmospheric fallout, rural streams particles, and Seine River particles upstream and downstream of Paris and at river mouth. Metal pathways and budgets have been set up for (i) a typical cultivated area, (ii) a Paris combined sewer system, (iii) Paris conurbation and (iv) the whole catchment metal retention effect in floodplain and dredged material. Metal fluxes to the estuary have been decomposed into natural, urban domestic and other sources. The latter are within 1-2 orders of magnitude larger than waste water fluxes directly released into rivers according to an industrial census. These fluxes have been further compared to the annual use (1994-2003) of these metals. Metal excess fluxes exported by the river are now a marginal leak of metal inputs to the catchment (i.e. "raw" metals, metals in goods, atmospheric fallout), generally from 0.2 to 5 per thousand. However, due to the very limited dilution power in this basin, the contamination of particles is still relatively high. The Seine River basin is gradually storing metals, mostly in manufactured products used in construction, but also in various waste dumps, industrial soils, agricultural and flood plain soils.     

Rain water leachates of heavy metals in road surface sediments

Samples of street surface and roadside gutter sediments within a separately sewered catchment in N.W. London have been analysed for heavy metal contamination. Particle size distributions are presented and the removal efficiency of metal species demonstrated for various street cleaning procedures. Laboratory sorption and desorption studies are described and solution concentrations are obtained for Pb, Cd and Mn.Solubility curves are typically variable with time with Mn showing the strongest tendency to attain equilibrium. No obvious dependence of metal concentrations on grain size is readily apparent although Cd tends to desorb more rapidly from size fractions greater than 250 μm.     

Intertidal trace metal concentrations in some sediments from the Humber estuary

The trace concentrations of a number of metals including chromium, zinc, lead, vanadium and copper have been determined in intertidal sediments from the south bank of the Humber estuary. The values have been associated with the particle size and organic carbon content of the sediments and the levels of metal concentration are compared generally with levels found elsewhere in estuarine and river sediments. The high values and trends in metal content of the sediments compared with “natural” levels may be ascribed to industrial and domestic effluents discharged into the estuary from a number of outfalls within the area. Methods of analysis to distinguish between natural and effluent metal contents of sediments are discussed.     

Geochemical and microfaunal proxies to assess environmental quality conditions during the recovery process of a heavily polluted estuary: the Bilbao estuary case (N. Spain)

This study explores the eventual environmental improvement of the Bilbao estuary (northern Spain), from 1997 to 2006, in order to assess current estuarine restoration being undertaken as part of a Revitalization Strategic Plan. The monitoring programme is based on spatial and temporal variation in the distributions of both benthic foraminiferal assemblages and heavy metals contained in surficial sediments from the polluted intertidal flats. The overall pattern shows a decreasing metal concentration; however, reversals to this trend are noticed in the middle estuary. From 2000 to 2003, a significant decrease in heavy metal concentration was observed which is most likely related to the implementation in 2001-2002 of the biological treatment at a central wastewater treatment plant. Although the metal concentration decreased by 85% for some elements, these values still remain considerably high. No significant change occurred between 2003 and 2006 in metal concentrations. During the monitoring period the estuary channel presented environmental conditions close to azoic in 3/4 of its watercourse. Only in the year 2006, the two lowermost estuarine samples exhibited an increase in microfaunal densities. These samples were dominated by pollution-resistant estuarine species. The fact that estuarine sediments quality is recovering very slowly seems to be caused mainly by the resuspension of accumulated contaminants in the sediments due to dredging and working activities in the estuary. Thus, local authorities should consider also the clean up of the pollutants stored in the sediments, not seeking only the achievement of the water quality standards, as these polluted sediments can act as source of contamination.     

Toxicity and potential risk assessment of a river polluted by acid mine drainage in the Iberian Pyrite Belt (SW Spain)

Metal contamination from acid mine drainage (AMD) is a serious problem in the southwest of the Iberian Peninsula, where the Iberian Pyrite Belt is located. This zone contains original sulfide reserves of about 1700 Mt distributed among more than 50 massive sulfide deposits. Weathering of these minerals releases to the waters significant quantities of toxic elements, which severely affect the sediments and surface waters of the region. The main goal of this paper is to evaluate the toxicity and the potential risk associated with the mining areas using Microtox test and different factors which assess the degree of contamination of the sediments and waters. For this, a natural stream polluted by AMD-discharge from an abandoned mine has been studied. The results show that elevated concentrations of Cu, As and Zn involve an important potential risk on the aquatic environment, associated both with sediments and waters. Microtox test informs that the sediments are extremely or very toxic, mainly related to concentrations of Fe, As, Cr, Al, Cd, Cu and Zn. Pollution is mainly transferred to the sediments increasing their potential toxicity. A natural creek affected by AMD can store a huge amount of pollution in its sediments while exhibiting a not very low water pH and low water metal concentration.     

Contaminant levels in sediments and asteroids (Asterias rubens L., Echinodermata) from the Belgian coast and Scheldt estuary: polychlorinated biphenyls and heavy metals

The Southern Bight of the North Sea is particularly exposed to anthropogenic contamination, due to heavy urbanisation and industrialisation of its catchment area. The present work focuses on polychlorinated biphenyl (PCB) and metal contamination of the marine environment along and off the Belgian coast. Its objectives were to compare the concentrations of seven PCB congeners and four heavy metals in the sediments (a repository for anthropogenic contaminants) and in the asteroid Asterias rubens (a recognized bioindicator species). Nineteen sampling stations were considered between the mouth of the Scheldt Estuary and the southern limit of the Belgian coast (asteroids were found in 10 out of the 19 stations). PCB and metal concentrations measured in sediments and asteroids were in the range of values reported in previous studies. Stations under direct influence of the Scheldt were the most impacted by the considered contaminants. Metal concentrations varied according to the grain-size fraction considered. In asteroids, PCBs and metals were found to be selectively distributed among body compartments, and pyloric caeca were found to most efficiently discriminate between sampling stations contamination levels. PCB and metal analysis of sediments provided a physicochemical evaluation of the contamination, whereas analysis of asteroids introduced a biological dimension to the approach by taking into account bioavailability of the contaminants.     

Organochlorine Contamination in Sediments of the Inner Thames Estuary

The saltmarsh at Two Tree Island, situated in the Thames estuary, has previously been identified as exhibiting a relatively enhanced degree of contamination with respect to organochlorine insecticides and polychlorinated biphenyls. This survey of sediment samples from mud flats on the north bank of the River Thames, creeks surrounding Canvey Island and from Two Tree Island, indicated that contamination with organochlorine and polychlorinated biphenyls was ubiquitous throughout the inner Thames estuary. Values observed were in agreement with those in other European estuaries, and the degree of contamination at Two Tree Island was considered to reflect the local background. The outfall from Benfleet sewage-treatment works was identified as a possible source of contaminants: however, no other point sources were located. Samples of annelids taken from mud flats by Two Tree Island had accumulated penta- and hexa-chlorinated biphenyls to a greater degree than lower chlorinated cogeners, and demonstrated signs of an ability to metabolize DDT.     

Arsenic speciation in river and estuarine waters from southwest Spain

An arsenic speciation survey was carried out in water samples from the Tinto and Odiel Rivers (southwest of Spain), as well as their common estuary. Both rivers are affected by acid mine drainage (AMD) and represent an input of heavy metals into the estuary, which also suffers from industrial water discharges. Samples were taken in December 2000 and July 2001. The arsenic species considered were arsenite (As(III)), arsenate (As(V)), monomethylarsonic (MMA) and dimethylarsinic (DMA) ions using coupled high-performance liquid chromatography-hydride generation-inductively coupled plasma-mass spectrometry (HPLC-HG-ICP-MS) for their determination. Parameters such as pH, salinity, redox potential and dissolved O2 were also measured. The results revealed that the acid mine drainage originating mainly during winter along the upper part of the Tinto River course causes high inorganic concentrations of dissolved arsenic, up to 600 microg l(-1) of As(III) and 200 microg l(-1) of As(V). In summer, As(III) levels decreased due to the diminution of the input from acid mine drainage and also because of oxidation, with a corresponding increase of As(V) level. Furthermore, the extreme acidic conditions of this river (pH 2.3-2-6) do not allow biological activity sufficient to produce significant concentrations of methylated arsenic species. The arsenic concentrations in the nearby Odiel River were always 5-10 times lower than in the Tinto River, with arsenic levels usually below 100 microg l(-1), dominated by As(V), indicating that it is less affected by acid mine drainage. The highest inorganic arsenic species concentrations were found where the river crosses a mining site, which corresponds to the highest As(III) values. Significant biological activity in this river produced methylated species that were detected along the water-course, with the highest concentrations at the lower course of the river, accounting for up to 53-61% of the total dissolved arsenic. At the common estuary formed by both rivers, only arsenate was detected in most samples at lower concentrations than in the riverine water samples. The tidal cycle showed a similar pattern of dilution of the arsenate when seawater comes into the estuary. Methylated species were not found either in summer or winter, at least at the 0.1 microg l(-1) level, possibly because of the high turbidity of the waters, producing an inhibition of the phytoplankton activity. In addition to the riverine inputs into the common estuary, industrial activity also represents an important source of arsenic as the discharge from a Cu smelter produced the highest arsenate level of all samples in estuary and also the only sample with significant arsenite concentration. Furthermore, the underlying iron-oxide-rich sediments represent an importance source of arsenic into the water column. In three nearby estuaries not affected by industrial activity or acid mine drainage, arsenic levels remained below detection limits.     

Distribution of some trace metals in Lochnagar, a Scottish mountain lake ecosystem and its catchment

Anthropogenic trace metals enter the entire ecosystem of Lochnagar solely through atmospheric deposition. Trace metals, including Hg, have been monitored in atmospheric deposition and lake water, and measured in catchment vegetation, aquatic plants and zooplankton, revealing contamination levels in the ecosystem. Furthermore, 17 sediment cores were taken from different areas of the lake. Hg, Pb, Cd, Zn and Cu were analysed in all the cores, which show that the sediments have been heavily contaminated by these trace metals since the 1860s. The distribution of trace metals in the lake sediments was found to be heterogeneous, with concentrations in the surface sediments varying significantly: 110-250 ng/g, 100-360 microg/g, 39-180 microg/g, 0.3-1.9 microg/g and 8-25 microg/g for Hg, Pb, Zn, Cd and Cu, respectively. Trends in the concentration profiles for different trace metals in the same core are different, as are the trends of the profiles for the same metal in different cores. Hence, a single sediment core cannot represent the pollution history of the whole lake. As the soils and sediments contain a high proportion of plant debris and the debris has a high affinity for Hg, resulting in Hg enrichment. Hg was measured in plant debris (> 63 microm) separated from catchment soils and lake sediments. Plant debris may play an important role in storing and transferring Hg in this ecosystem.     

TAPIR — Finnish national geochemical baseline database

In Finland, a Government Decree on the Assessment of Soil Contamination and Remediation Needs has generated a need for reliable and readily accessible data on geochemical baseline concentrations in Finnish soils. According to the Decree, baseline concentrations, referring both to the natural geological background concentrations and the diffuse anthropogenic input of substances, shall be taken into account in the soil contamination assessment process. This baseline information is provided in a national geochemical baseline database, TAPIR, that is publicly available via the Internet.Geochemical provinces with elevated baseline concentrations were delineated to provide regional geochemical baseline values. The nationwide geochemical datasets were used to divide Finland into geochemical provinces. Several metals (Co, Cr, Cu, Ni, V, and Zn) showed anomalous concentrations in seven regions that were defined as metal provinces. Arsenic did not follow a similar distribution to any other elements, and four arsenic provinces were separately determined. Nationwide geochemical datasets were not available for some other important elements such as Cd and Pb. Although these elements are included in the TAPIR system, their distribution does not necessarily follow the ones pre-defined for metal and arsenic provinces.Regional geochemical baseline values, presented as upper limit of geochemical variation within the region, can be used as trigger values to assess potential soil contamination. Baseline values have also been used to determine upper and lower guideline values that must be taken into account as a tool in basic risk assessment. If regional geochemical baseline values are available, the national guideline values prescribed in the Decree based on ecological risks can be modified accordingly.The national geochemical baseline database provides scientifically sound, easily accessible and generally accepted information on the baseline values, and it can be used in various environmental applications.     

Uranium behaviour in an estuary polluted by mining and industrial effluents: The Ría of Huelva (SW of Spain)

This paper describes a comprehensive study of the behaviour of U in the Ría of Huelva estuary, formed by the Tinto and Odiel rivers. This ecosystem is conditioned by two hydrochemical facts: one connected with the acid mining drainage (AMD) generated in the first section of the river basins, and another one related to the fertilizer industry located at the estuary. AMD gives a singular character to these rivers; low pH and high redox potential that keep high amounts of toxic elements and radionuclides in dissolution. Most of the data for dissolved U in estuaries indicate conservative mixing, but there are examples of non-conservative behaviour attributed to oxidation/reduction processes or solubility variations. In the Ría of Huelva estuary the U shows a non-conservative behaviour due to solubility changes produced by variations in the pH. A complete removal of riverine dissolved U is observed in a pH range of 4–6. At higher pH values, U release from suspended matter, and probably also from sediments into the dissolved phase is found.     

137Cs distribution and geochemistry of Lena River (Siberia) drainage basin lake sediments

The Lena River is the second largest river that discharges into the Arctic Ocean. It is therefore important to determine not only the direct impact its discharge has on the 137Cs concentration of the Arctic, but also the potential its drainage basin has as a 137Cs source. 137Cs surface sediment concentrations and inventory values, which range from 4.97 to 338 Bq kg(-1) and 357 to 1732 Bq m(-2), respectively, were determined for the Lena River drainage basin lake samples, via gamma analysis. The average geochemical and mineralogical composition of a subset of samples was also determined using neutron activation analysis, X-ray diffraction and X-ray fluorescence spectrometry techniques. Results of these geochemical analyses allowed for the identification of key geochemical factors that influence the distribution of 137Cs in the Lena River drainage basin. 137Cs profiles indicate that Lena River drainage basin lacustrine sediments serve as a record of 137Cs fallout. Based on the downcore 137Cs, %illite, %smectite, %Al and %Mn distribution patterns, it was concluded that a small fraction of non-selectively bound 137Cs was remobilized at depth in some cores. Inconsistencies between the actual 137Cs fallout record and the 137Cs profiles determined for the lake sediments were attributed to 137Cs remobilization in subsurface sediments. In addition to establishing the agreement between the global atmospheric fallout record and the downcore 137Cs distribution patterns determined for these sediments, results indicate that 137Cs deposited during periods of maximum atmospheric release was buried and is not susceptible to surface erosion processes. However, mean 137Cs concentrations of the lacustrine surface sediments (125 Bq kg(-1)) are still significantly higher than those of the nearby Lena River estuary (11.22 Bq kg(-1)) and Laptev Sea (6.00 Bq kg(-1)). Our study suggests that the Lena River drainage basin has the potential to serve as a source of 137Cs to the adjacent Arctic Ocean.     

Lead and zinc in the Wallsend Burn, an urban catchment in Tyneside, UK

This paper examines lead and zinc concentrations in topsoils and stream sediments of public access areas in an urban catchment in Tyneside, UK. It examines the extent and severity of metal contamination, explores spatial patterns in relation to urban and industrial development, and makes inferences about potential metal mobility. Total and acetic-acid extractable lead and zinc concentrations, organic content and pH were determined on 121 topsoil and 22 stream sediment samples using standard laboratory procedures. Using the lowest trigger thresholds for total lead and zinc, almost 75% and 91%, respectively, of topsoil samples were classified as contaminated; proportions were rather lower for acetic acid extractable metals. Similarly, approximately 45% and 95% of stream sediment samples were contaminated with lead and zinc, respectively. The spatial distribution of metal concentrations was characterized by a hotspot pattern, with highest values in central and southern parts of the catchment where there is a long urban and industrial history. The potential mobility of zinc is considerably greater than that of lead in both topsoils and stream sediments, and for both metals is slightly higher in the stream sediments than in the topsoils; both of these differences are statistically significant (P < 0.05). The implications of the findings in this paper for assessment and monitoring of metal contaminated areas are explored.     

Les matieres en suspension dans les estuaires

This paper, devoted to the behaviour of suspended matters in estuaries, deals successively with:

- the nature and origin of sediments suspended in some estuaries

- the behaviour of suspended materials: flocculation, falling rate of flakes, shrinkage, rheology, picking up by currents, slides inside the deposits

- the sedimentary movements of floating materials in the estuaries: transport under the influence of the tides, sedimentary materials available in the estuary, influence of the river discharge and of the salinity, ejection of suspended matters out of the estuary,

- volume of the deposits in some estuaries.

     

Stable lead isotopes ratios in major french rivers and estuaries

Lead isotopes ratios have been determined in suspended matter and water samples collected from major rivers and estuaries in France to assess their present level of Pb pollution.Most of the anthropogenic Pb found in the environment comes from Pb alkyls added to petrol. In France most petrol Pb comes from imported Pb ores which mainly have very characteristic Pb isotopes ratios (for example, a low ²⁰⁶Pb/²⁰⁷Pb ratio). Indeed, the ²⁰⁶Pb/²⁰⁷Pb ratio of aerosols sampled in France near a highway and a carpark was found to be very low (1.09-1.11). Despite not being so important with respect to atmospheric and water pollution, anthropogenic Pb produced by the iron, steel and copper production industries has also been considered and a slightly higher ²⁰⁶Pb/²⁰⁷Pb ratio (1.141) has been found from measurements made in the north of France near industrial plants.Conversely, higher ²⁰⁶Pb/²⁰⁷Pb ratios (1.197-1.206) were found in the pre-industrial sediments discharged by the rivers studied. These ratios are considered to be representative of local natural Pb during pre-industrial times.The measured Pb isotopes ratios in the suspended particulate matter compared with the two end-members show that the most polluted river is the Seine, followed by the Rhône and then the Garonne and the Loire. It is shown that anthropogenic Pb pollution is more easily detected when the solid discharge is low, such as in the Seine river. Conversely, a high particulate load can dilute the level of pollution by anthropogenic Pb and in this case Pb isotopes ratios are very similar to the natural level.As far as estuaries are concerned (the Seine estuary was not studied), variations of Pb isotopes ratios are generally observed and are attributed either to natural geochemical processes (Gironde estuary) or to man's influence (Loire and Rhône estuaries).