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At least 883 records · Page 49Linked to original sources
PubMed2001

Late Holocene rainforest disturbance in French Guiana.

Palm swamp forest sediments collected in French Guiana provide new data about late Holocene rainforest. Two cores were collected in 'Les Nouragues' ecological station (4 degrees 05'N, 52 degrees 40'W). The lithology shows two different types of sediment, organic peat in the upper part and oxidized clay with low organic content and lacking pollen in the lower part, both separated by a gravel horizon. Radiocarbon dates show that this gravel horizon could have been deposited between 4500 and 3000yrBP. Pollen analysis carried out on the organic sediments record rainforest disturbances between ca 1520-1380 and 1060-860cal yrBP suggested by the presence of the pioneer tree species Cecropia together with other shade intolerant genera. Cecropia is recorded for a period that lasts between 660 and 320 years. This abnormal duration for presence of a pioneer species in rainforest is explained by brief and repeated changes in the composition of the canopy asssociated to perturbations of the palm swamp.

Journal Article↗
PubMed2000

Evaluation of Holocene pollen records from the Romanian Plain.

This study is a critical review of pollen analyses carried out on Holocene sequences from 15 sites in and near the Romanian Plain. Three sites come from natural sediments, 10 sites are from anthropogenic deposits and two are from both anthropogenic and natural settings. The general reconstruction is of a steppe-forest-steppe vegetation through the Holocene. The nature of the deposits, however, casts doubts on this reconstruction. Deposits of archaeological sites generally yield pollen spectra that are influenced by human activities and thus unsuitable for vegetation reconstructions. Loess deposits are also unfavorable for pollen preservation because of high pH and porosity. Consequently, pollen spectra from loess deposits are strongly biased by selective pollen destruction. Research and experiments carried out by several authors suggest that spectra dominated by Asteraceae, Poaceae, Chenopodiaceae or Pinus pollen in soils and loess are a result of selective pollen destruction, especially if low pollen concentrations, progressive pollen deterioration or high frequencies of deteriorated or unidentifiable pollen are evidenced. The fact that pollen records from the Romanian Plain come from loess, alkaline peat or archaeological sites reduces their reliability for reconstructions of vegetation. The vegetation history of similar regions in Hungary, Bulgaria and Turkey suggests that early Holocene steppe vegetation was gradually replaced by forest or forest-steppe vegetation in the late Holocene. Records from lake sediments are required to find out whether the Holocene vegetation history of the Romanian Plain was similar.

Journal Article↗
PubMed2001

Aggregation rates of natural particle populations.

In this paper an experimental approach of aggregation in natural suspensions is presented. The suspensions are organic-matter-rich waters sampled in a brook which drains peat areas. The aggregation was conducted on raw samples in three different experiments lasting from 2 to 8 days. The particle size distribution (PSD) in the 0.5-10 microm size range was followed with a laser sizer and appeared to be almost constant along the whole experiment duration. Nevertheless, the volume of particles larger than 10 microm increased steadily, showing that aggregation occured. This appeared to be the consequence of a steady-state aggregation which allowed the removal of the whole particle set within a day. The use of an aggregation model adapted to calculations on PSD allowed estimation of the aggregation efficiency for such suspensions.

Chemical Precipitation↗
PubMed2001

Laboratory column studies for evaluating a barrier system for providing oxygen and substrate for TCE biodegradation.

The industrial solvent trichloroethylene (TCE) is among the most ubiquitous chlorinated compounds found in groundwater contamination. The objective of this study was to develop a biobarrier system containing oxygen-organic releasing material to enhance the aerobic cometabolism of TCE in situ. The oxygen-organic material, which contains calcium peroxide and peat, is able to release oxygen and primary substrates continuously upon contact with water. Batch experiments were conducted to design and identify the components of the oxygen-organic releasing material, and evaluate the oxygen and organic substrate (presented as COD equivalent) release from the designed oxygen-organic material. The observed oxygen and chemical oxygen demand (COD) release rates were approximately 0.0246 and 0.052 mg/d/g of material, respectively. A laboratory-scale column experiment was then conducted to evaluate the feasibility of this proposed system for the bioremediation of TCE-contaminated groundwater. This system was performed using a series of continuous-flow glass columns including a soil column, an oxygen-organic material column, followed by two consecutive soil columns. Aerobic acclimated sludges were inoculated in all three soil columns to provide microbial consortia for TCE biodegradation. Simulated TCE-contaminated groundwater with a flow rate of 0.25 l/day was pumped into this system. Effluent samples from each column were analyzed for TCE and other indicating parameters (e.g., pH, dissolved oxygen). Results show that the decreases in TCE concentrations were observed over a 4-month operating period. Up to 99% of TCE removal efficiency was obtained in this passive system. Results indicate that the continuously released oxygen and organic substrates from the oxygen-organic materials enhanced TCE biotransformation. Thus, the biobarrier treatment scheme has the potential to be developed into an environmentally and economically acceptable remediation technology.

Biodegradation, Environmental↗
PubMed2002

Partitioning and bioaccumulation of cadmium in artificial sediment systems: application of a stable isotope tracer technique.

The utility of stable isotope tracers for investigating the relationship between cadmium (Cd) partitioning in artificial sediment-water systems and Cd accumulation in a benthic detritivore (Asellus racovitzai, Isopoda) was explored. In the laboratory, Cd isotopes were applied to synthetic sediment and isotope concentrations were measured in sediment, overlying water and exposed asellids over a 10-day period. Isotope ratios measured in sediment and water were compared to ratios measured in asellids to determine whether Cd partitioning could predict metal bioaccumulation. Two different parameters which might affect Cd partitioning between the sediment and overlying water compartments were investigated: the chemical form in which Cd was added to systems, and the organic matter content of the sediment. To test the effect of chemical form on Cd partitioning, three isotopes of cadmium were individually applied to formulated sediment in varying combinations of 113Cd(NO3)2, 112Cd-humic acid (HA) 114CdSO4. The results demonstrated that chemical form did not influence partitioning, as the Cd isotope that was applied to sediment in the nitrate form exhibited similar partitioning between sediment and overlying water as the isotope that was applied in the sulfate or HA form. However, Cd isotope concentrations in overlying water were strongly related to the pattern of isotope accumulation in asellids suggesting that overlying water concentrations determined Cd bioaccumulation. In contrast, when the organic matter content of sediment was increased through the addition of Sphagnum peat moss, total Cd concentrations in overlying water and tissue were low, and there was no relationship between Cd-isotope concentrations in tissue and water. These results indicate that Cd accumulation occurred primarily from water, and factors that increase metal partitioning to sediment, such as increased sediment organic matter content, decrease Cd accumulation in asellids. The stable isotope tracer method described herein appears to be a useful technique for investigating the relationship between metal partitioning and bioaccumulation in simple sediment systems, but could also be extended to more complex systems, and used with different metals that have multiple stable isotopes.

Animals↗
PubMed2003

Peatlands: a major sink of naturally formed organic chlorine.

It is a little known fact that many chlorinated organic compounds occur naturally and that some are also indispensable to life on earth. Here, we show that chlorination of organic compounds during humification processes in peat is widespread in nature. Globally this process has led to the accumulation of approximately 280-1000 million tons of organically bound chlorine in peatlands during the postglacial period.

Chlorine↗
PubMed2003

Competition between alga (Pseudokirchneriella subcapitata), humic substances and EDTA for Cd and Zn control in the algal assay procedure (AAP) medium.

The chemical speciation of trace metals in natural waters has important implications for their biogeochemical behavior. Trace metals are present in natural waters as dissolved species and associated with colloids and particles. The complexation of one trace metal (Cd and Zn at 200 and 390 microg/l respectively) with a green alga Pseudokirchneriella subcapitata in colloid-free algal culture medium and in presence of colloidal humic substances (HS) is presented. The influence of the nature of colloids was also addressed using three "standard" HS: fulvic acid (FA) and, soil (SHA) and peat humic acids (PHA). The chemical speciation model, MINTEQA2, was used to simulate the influence of pH and standardized culture medium on metal association with humic substances. The model was successfully modified to consider the differences in the metal complexation with fulvic (FA) and humic acids (HA). The deviations of concentrations of metals associated with HS between experimental results and model predictions were within a factor of approximately 2. The results of speciation model highlight the influence of the experimental conditions (pH, EDTA) used for alga bioassay on the behavior of Cd and Zn. The computed speciation suggests working with a pH buffered/EDTA-free mixture to avoid undesirable competition effects. The behavior of Cd and Zn in solution is more strongly influenced by HS than by alga. Metal-HS associations depend on metal and humic substance nature and concentration. Cd is complexed to a higher extent than Zn, in particular at larger HS concentration, and the complexation strength is in the order FA<HA.

Benzopyrans↗
PubMed2003

Influence of humic substances on the toxic effects of cadmium and zinc to the green alga Pseudokirchneriella subcapitata.

A method combining (1 h) algal photosynthesis inhibition tests and tangential-flow ultrafiltration (TFF) technique (cut-off 1 kDa) was used to determine the effect of humic substances (HS) on acute metal toxicity to Pseudokirchneriella subcapitata. Three "standard" HS (soil and peat humic acids and Suwannee River fulvic acids) at two concentrations (1 and 5 mg/l) and two metals (Zn at 390 microg/l and Cd at 200 microg/l) were studied. Toxicity of Cd and Zn to P. subcapitata was significantly (p<0.05) reduced in the presence of humic acids (HA) but not in the presence of Suwannee River fulvic acids (SRFA). Metal partitioning between colloidal (1 microm-1 kDa) and truly dissolved (<1 kDa) fractions was found to match a decrease of metal toxicity in the presence of HA, but not in the presence of SRFA. The results suggested that HA reduced Cd and Zn toxicity in two different ways: (1) HA decrease the amount of free metal ions. Metal-HA complexes are high molecular weight, relatively stable with regard to metal-exchange reactions and consequently the metals were less bioavailable. (2) HA adsorbed onto algal surfaces, shielded the cells from free Cd and Zn ions. Several possible explanations can be postulated to account for the observed SRFA results: (1) Cd- and Zn-SRFA complexes are thought to be labile (i.e. undergo rapid dissociation); (2) SRFA coagulated, presumably during equilibration, and that coagulation altered metal complexing behavior of SRFA; (3) FA has a lower ability to adsorb on cell membranes at pH>7.

Cadmium↗
PubMed2000

Synthetic zeolites as amendments for sewage sludge-based compost.

The effects of incorporating a synthetic zeolite (Zeolite P) in a range of concentrations (0.1-1.0 w:w) into an experimental horticultural compost, derived from sewage sludge, have been investigated. The impact of zeolite treatment on time-related changes of the labile zinc, copper, iron and manganese pools within the compost was compared to lime incorporation (5% w:w) and to a proprietary unamended peat-based compost. Addition of 0.5% and 1.0% zeolite significantly reduced labile zinc over a 90 day period. The highest zeolite treatment was more effective than liming; 0.5% zeolite was as effective as lime. Plant growth trials measuring transfer of metals to ryegrass (Lolium perenne L. cv Elka) in successive harvests demonstrated that both 1.0% zeolite and 5% lime treatment caused significant reduction in total metal transfer from soil-plant over a 116 day growth period. It is concluded that the use of synthetic zeolite as an amendment for compost of this type significantly reduces potential for soil metal mobility and soil-plant transfer.

Lolium↗
PubMed2000

Electrochemical degradation of humic acid.

The treatment of natural water for drinking water production goes through the degradation of humic substances. In this study, humic acid, extracted from a peat area located at the margins of the Mogi Guaçu River at São Paulo State, Brazil, was used to perform electro-oxidation essays in order to evaluate the possibilities of electrochemical methods in the degradation of humic substances. The working electrodes were dimensionally stable anodes (DSA) type with the following compositions: Ti/Ir0.3Ti0.7O2; Ti/Ru0.3Ti0.7O2; and Ti/Ir0.2Ru0.2Ti0.6O2. The electrolyses were performed by using a solution composed of an electrolyte support (0.1 mol l(-1) KCL) and 30 mg l-1 of the humic acid. Samples were taken during the electrolyses and analysed by the pH, transmittance, UV-vis spectra and chromatography. The results show that the Ti/Ru0.3Ti0.7O2 electrode presents the best performance considering the elimination of most of the electro-oxidation products after approximately 2 h of electrolysis at 40 mA cm(-2).

Electrochemistry↗
PubMed2001

Effect of ditching operations on stream-water chemistry in a boreal forested catchment.

The effects of ditching of boreal forest land on stream-water quality and quantity was assessed by comparing, over a 4-year-period, the physicochemical properties of the water in two small streams (western Finland), one whose catchment was ditched for forestry halfway through the sampling period and another nearby (control) stream whose catchment was not ditched ('paired catchment method'). While the artificial drainage did not have any significant effect on the hydrograph, it resulted in an increase in the aquatic concentrations of Mn, Ca, Mg, suspended material and alkalinity, a decrease in the concentrations of TOC and H3O+, while for Al and Fe there was a change in control mechanisms. The concentration and control changes after ditching are related to changes in hydrological pathways and to the exposure of both organic (peat) and inorganic (mineral soil) layers on the ditch slopes.

Forestry↗
PubMed2001

Partitioning and speciation of chromium, copper, and arsenic in CCA-contaminated soils: influence of soil composition.

This study focused on the influence of soil composition and physicochemical characteristics on the retention and partitioning of Cu, Cr and As in nine chromated copper arsenate (CCA) artificially contaminated soils. A statistical mixture design was used to set up the number of soils and their respective composition. Sequential extraction and modified solvent extraction were used to assess Cu and Cr partitioning and As speciation [As(III) or As(V)]. It was found that peat had a strong influence on CEC (232 meq/100 g), on buffer capacity and on Cu and Cr retention, whereas kaolinite's contribution to the CEC was minor (38 meq/100 g). Average metal retention in mineral soils was low (58% for Cu and 23% for Cr) but increased dramatically in highly organic soils (96% for Cu and 78% for Cr). However, both organic and mineral soils demonstrated a very high sorption of added As (71-81%). Levels of Cu and Cr in a soluble or exchangeable form (F1) in highly organic soils were very low, whereas the levels strongly bound to organic matter were much higher. Conversely, in mineral soils, 47% of Cu and 18% of Cr were found in F1. As a result, Cr and Cu in moderately and highly organic contaminated soils were present in less mobile and less bioavailable forms, whereas in mineral soils, the labile fraction was higher. The modified method used for selective determination of mineral As species in CCA-contaminated soils was found to be quantitative and reliable. Results revealed that arsenic was principally in the pentavalent state. Nevertheless, in organic soils, arsenite was found in significant proportions (average value of 29% in highly organic soils). This indicates that some reduction of arsenate to arsenite occurred since the original species in CCA is As(V).

Arsenates↗
PubMed2002

Recovery from acidification in the Tillingbourne catchment, southern England: catchment description and preliminary results.

Measurements of acid deposition and streamwater chemistry made in 1979-1982 and 1999-2000 are compared for a small, acid-sensitive catchment in Southeast England. The location, geology, soils, vegetation and hydrology of the catchment are described. The catchment is located on an acidic cretaceous sandstone with a low permeability clay sub-stratum. Soils are predominantly podzol and gley, with some mesotrophic peat. The catchment is forested. Mean volume-weighted concentrations in precipitation have changed approximately in proportion to emission changes. SO4(2-) has declined by 61%, H+ by 75%, both NO- and NH4+ by 37% and Cl- by 26%. Changes in wet deposition are greater, sulfate deposition declined by 69%, non-marine SO4(2-) by 73%, H+ deposition by 75%, NO3- and NH4+ by 50% and Cl- by 41%. Sulfate deposition in throughfall, a surrogate for total deposition measurement, has declined by 82% and non-marine SO4(2-) by 86%. Some of these changes are due to alterations in the tree cover and location of the collectors. In 1979-1982, the flux of NO3- and NH4+ in throughfall was less than in rainfall, 7.5 compared with 11.3 kg N ha(-1) year(-1), showing that N uptake by the canopy was greater than dry deposition of these species. However, in 1999-2000, the throughfall flux of N was greater than rainfall, 19.6 compared to 5.7 kg N ha year(-1), indicating that canopy uptake is not occurring to the same extent. Surface water was sampled at the same locations in the catchment during the two periods. At the catchment exit, mean pH increased, from 3.93 to 4.21 mg l(-1), and SO4(2-) declined from 20.2 to 16.7 mg l(-1) (18%). The decrease in SO4(2-) is much less than the reduction in deposition, suggesting that the predicted recovery is being delayed by release of sulfur from the soil. In contrast, NO3- concentrations in the catchment waters increased from 0.22 to 0.52 mg N l(-1) (133%) despite the reduction in N deposition. NH4+ concentrations were low during both study periods. It is concluded that recovery from acidification is probably occurring, but is possibly being delayed by desorption of soil S. The catchment is also showing signs of increasing N saturation, despite a reduction in N inputs.

Absorption↗
PubMed2002

Historical changes in lead concentrations in tree-rings of sycamore, oak and Scots pine in north-west England.

Lead concentrations in tree rings of sycamore (Acer pseudoplatanus L.), oak (Quercus robur L.) and Scots pine (Pinus sylvestris L.) sampled at a parkland in north-west England were measured in wood formed since the mid-1800s. Concentrations of Pb in Scots pine and oak peaked in wood formed between 1900 and 1940, most likely because of Pb accumulation in heartwood, indicating that oak and Scots pine are unsuitable for monitoring temporal changes in Pb deposition at the study site. In contrast, Pb concentrations in sycamore, a species that has similar heartwood and sapwood chemistry, were relatively constant in wood formed between the mid-1800s and 1950. Lead concentrations decreased steadily in sycamore tree rings formed after the 1950s, and decreased more abruptly in wood formed after 1985. This sharp decrease in wood Pb cannot be due to decreases in soil Pb concentration. Stable Pb isotope analysis was used to further investigate Pb patterns in sycamore wood. Excess 206Pb/207Pb ratios in tree-rings of sycamore were relatively constant, approximately 1.17, in wood formed prior to the 1930s, but decreased steadily thereafter reaching a minimum value of approximately 1.16 in wood formed between 1975 and 1985 after which time 206Pb/207Pb ratios increased. This pattern is consistent with changes in Pb isotope ratios measured in peat, sediment and aerosol samples in the UK. However, the magnitude of the decrease in 206Pb/207Pb (largely due to gasoline Pb) is considerably lower than in other studies and our estimates indicate that less than 20% of the total Pb in sycamore wood measured since the mid-1800s is derived from gasoline emissions. A more likely explanation for the pattern of Pb observed in sycamore tree rings is that soil Pb accumulates within rings of the diffuse porous wood over a number of years. Such uptake patterns would result in lower Pb concentrations in the outer (more recently formed) tree rings, which coincide with recent reductions in Pb deposition in the UK. Overall, this study indicates that tree ring chemistry is unsuitable for monitoring historical changes in Pb deposition at the study site.

Air Pollutants↗
PubMed2002

A chemical and mineralogical reconstruction of Zn-smelter emissions in the Kempen region (Belgium), based on organic pool sediment cores.

The atmospheric pollution history of a former Belgian Zn-smelter complex is preserved in organic sediments of a nearby peat bog pool. The stratigraphy of trace metals, Pb-isotope ratios and mineralogy indicate extreme heavy metal pollution in recent sediments. In the pollutant trend, extremes coincide with maxima in 20th century metal production, minima during major war conflicts and the final shutdown of the smelter. Peak pollution concentrations measure up to 4.7 wt.% Zn, 1.1 wt.% Pb and 0.1 wt.% Cd, which correspond to calculated atmospheric deposition rates of 9.0, 1.6 and 0.16 g m(-2) yr(-1), respectively. 206Pb/207Pb isotope ratios show higher values in the polluted interval (1.135-1.162) relative to local geogenic values deeper down-core (1.194-1.215). Within the polluted interval, three significantly different 208Pb/206Pb plateaus are recognized and suggested to indicate changes in the origins of processed ores. Microprobe analyses on sediment thin sections show extensive in situ FeS2 and ZnS precipitation, which suggests that anoxic processes are responsible for the immobilization of the atmospheric metal inputs. The occurrence of oxidized smelter dusts in an independent surface soil sample indicates a rapid diagenetic transformation of metal oxides into sulfides. Morphology and chemical characteristics allow the distinction between smelter related and diagenetic mineral deposits, and give evidence for dust from open-air ore repositories, as well as smelter operation without dust filters.

Air Pollutants↗
PubMed2002

Sequential extraction of sulfide-rich tailings remediated by the application of till cover, Kristineberg mine, northern Sweden.

A sequential extraction has been carried out on sulfide-rich mine tailings. The purpose was to investigate how elements released by oxidation are secondarily retained in the tailings and the possible consequences of the remediation. After investigating the solid tailings, seven samples were chosen for sequential extractions. Two samples were oxidised, situated just above the oxidation front; two samples from just below the former oxidation front with increased concentrations of several elements; two unoxidised samples were from an intermediate depth, and the deepest sample was from the tailings-peat boundary at the bottom of the impoundment. Five phases were extracted: adsorbed/exchangeable/carbonate; labile organics; amorphous Fe-oxyhydroxides/Mn-oxides; crystalline Fe-oxides; and organics/sulfides. The addition from dried porewater to the extracted fractions has been calculated and considered as minor. In the oxidised tailings, the sulfide fraction still dominates for elements such as Fe, S, Cd, Co, Cu, Hg and Zn, although the concentrations are low compared to the unoxidised tailings. Generally, the second most important fraction is the adsorbed/exchangeable/carbonate fraction. Below the oxidation front, the sulfide content of the tailings sharply increases. In the secondary enrichment zone, the total element concentrations increase compared with the deeper unoxidised samples, mainly due to secondary retention. For some elements, secondary retention is greater than the total amount extracted for the deeper unoxidised samples. In the secondary enrichment zone the adsorbed/exchangeable/carbonate fraction represents approximately 20 wt.% or more for Cd, Co, Mn, Ni and Zn. The amorphous iron oxyhydroxide or the crystalline iron oxide fractions are less important at this level, although for As, Ba and Cu the amorphous iron oxyhydroxide fraction represents up to 20 wt.%. At the lower border of the enrichment zone, the total concentration for most metals is lower, but the importance of the adsorbed/exchangeable/carbonate fraction is further enhanced for Cd, Cu, Ni and Zn. These elements have 35-60 wt.% of the total amount from this fraction. For As, Cd, Cu, Ni and Pb, the secondary fractions extracted (extractions A-D) represent between 60 and 80 wt.% of the total content. At greater depth in the impoundment the relative importance of the adsorbed/exchangeable/carbonate fraction decreases, whilst the importance of amorphous iron oxyhydroxide and crystalline iron oxide fractions increases. The adsorbed/exchangeable/carbonate fraction is the most easily remobilised fraction. A raised groundwater table previously situated below the enrichment zone may result in the release of secondarily retained metals.

Adsorption↗
PubMed2003

Polycyclic aromatic hydrocarbons (PAHs) in bottom sediments of the Kara Sea shelf, Gulf of Ob and Yenisei Bay.

PAH concentration and distribution has been examined in surface sediments samples from the Kara Sea, Russia. The study includes 13 samples from the South-eastern Kara Sea shelf, one sample from the south-western part of the sea, 4 samples from the Baydaratskaya Bay, 5 samples from the Gulf of Ob and 4 samples from the Yenisei Bay, collected in August-September 1993-1994. Cluster analysis and principal component analysis (PCA) were used to identify common patterns and possible sources of PAHs. The total PAH concentration (sum of two- to six-ring aromatic hydrocarbons) in the Kara Sea sediments was generally lower than in the Barents Sea sediments and comparable to the levels in the Pechora and White seas. Two- and three-ring aromatic hydrocarbons predominated in Kara Sea sediments, which indicate a relatively stronger petrogenic origin than that in the adjacent seas. The highest total PAH concentrations within the Kara Sea were found in sediments from the Yenisei Bay and in the South-western part of the Kara Sea in the Eastern Novaya Zemlya Trough. The PAHs of the Yenisei Bay sediments were dominated by perylene and PAHs of petrogenic origin, but had also a strong indication of PAHs of pyrogenic origin. The dominating PAH group in the South-western part of the Kara Sea were four- to six-ring aromatic hydrocarbons, indicating pyrogenic origin. Perylene levels were high in all the Kara Sea samples, and highest levels were found in areas of strong terrigenous influence. The most probable source is decaying peat products being transported to the Kara Sea by both large and small rivers.

Biological Availability↗
PubMed2003

Monitoring change in hydrological systems.

Monitoring is the process by which we keep the behaviour of the environment in view, providing essential information on how systems are changing and how fast, and allows us to learn to adjust what we are doing to get the best out of the system. This paper reviews the ways in which long-term study of the natural environment can be achieved. Three hydrological examples are then presented: nitrate leaching in a small agricultural catchment in south west England; the impact of drought on the peat-covered headwaters of the River Tees in northern England; and the impact of clear-felling on forest hydrology and nutrient export in the southern Appalachians. Monitoring programmes, if well designed and properly maintained, can provide important evidence of environmental change, revealing unexpected patterns and stimulating experimental research. The existence of long, reliable data sets considerably increases our ability to make informed decisions about the way in which we manage our river catchments.

Agriculture↗