Fungal colonization on stoneworks. Interaction fungi-powdered stone samples

The microbial activity plays an important role in the biodegradative processes implied in stonework decay. In natural environments it is not possible to separate the damage produced by microorganisms from damage caused by physical and chemical agents. In vitro assays carried out with microbes isolated from weathered stones are required in order to understand the biological mechanisms involved in stone deterioration. We have described, as commented in the text, how fungal colonization observed on scaglia may be the result of the fine grain size of rock, whereas inhibition of growth on marble may depend on the surface characteristics of calcite grains after grinding. The extent of microbial growth clearly depends on the quantity of cations released in solution. However, fungal growth may, in turn, induce a decrease in pH, thus promoting mineral chemical attack. These observation points to selective action of fungal species in promoting weathering well evidenced by the presence of different extents of cations released in suspension from the same sample. Detailed studies are in progress in order to go into this question.

Extraction of spiked metals from contaminated coastal sediments: a comparison of different methods

Various extraction methods have been developed to assess metal bioavailability from sediments. In this study, we compared the extraction of Cd, Cr, and Zn from contaminated sediments using different extractants (normal seawater, acidic seawater of pH = 5. seawater with 1% sodium dodecyl sulfate [SDS], and gut digestive fluids collected in vitro from deposit-feeding peanut worm Sipunculus nudus) coupled with concurrent metal speciation measurements. The influences of sediment aging on metal extraction were also examined using radiotracer-spiked techniques. Sediments aging up to 100 d did not significantly affect the partitioning of spiked Cd and Cr in different geochemical phases, but the spiked Zn was partitioned more into the reducible fraction and less into the carbonate phase with increasing sediment aging. There was a major difference in the partitioning into different geochemical phases between the spiked metals and the native metals within the 100-d sediment aging. The difference between the spiked and native Cd and Zn extraction using gut juices was somewhat smaller than the strong geochemical contrast. Metals bound with the anoxic sediments were hardly extracted by different extractants. There was a significant relationship between the extraction of spiked Cd and its distribution in the exchangeable phase (positive correlation) or in the reducible phase (negative correlation). For Cr and Zn, extraction was not correlated with their partitioning in any of the geochemical phases. Further, extraction of all three metals by digestive gut fluids was not correlated with the concentrations of simultaneously extractable metals (SEM), nor with the difference between SEM and acid volatile sulfide (AVS). Our study suggests that there were large differences in extraction among metals using different extractants and only Cd extraction was significantly related to its geochemical speciation in sediments.

Steady flow to a well near a stream with a leaky bed

We present an explicit analytic solution for steady, two-dimensional ground water flow to a well near a leaky streambed that penetrates the aquifer partially. Leakage from the stream is approximated as occurring along the centerline of the stream. The problem domain is infinite and pumping on one side of the stream induces flow on the other side. The solution includes the effects of uniform flow in the far field and a sloping hydraulic head in the stream. We use the solution to investigate the interaction between ground water and surface water in the stream, the effects of pumping on the opposite side of the stream, and the effects of the leaky streambed on the capture zone envelope of the well. We develop a relationship between parameters such that the pumping well will not capture water from the stream, or from the opposite side of the stream. When the discharge of the well is large enough to capture water from the stream, the shape of the capture zone envelope depends on flow conditions on the side of the stream opposite the well.

Major and trace elements of selected pedons in the USA

Few studies of soil geochemistry over large geographic areas exist, especially studies encompassing data from major pedogenic horizons that evaluate both native concentrations of elements and anthropogenically contaminated soils. In this study, pedons (n = 486) were analyzed for trace (Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb, Zn) and major (Al, Ca, Fe, K, Mg, Na, P, Si, Ti, Zr) elements, as well as other soil properties. The objectives were to (i) determine the concentration range of selected elements in a variety of U.S. soils with and without known anthropogenic additions, (ii) illustrate the association of elemental source and content by assessing trace elemental content for several selected pedons, and (iii) evaluate relationships among and between elements and other soil properties. Trace element concentrations in the non-anthropogenic dataset (NAD) were in the order Mn > (Zn, Cr, Ni, Cu) > (Pb, Co) > (Cd, Hg), with greatest mean total concentrations for the Andisol order. Geometric means by horizon indicate that trace elements are concentrated in surface and/or B horizons over C horizons. Median values for trace elements are significantly higher in surface horizons of the anthropogenic dataset (AD) over the NAD. Total Al, Fe, cation exchange capacity (CEC), organic C, pH, and clay exhibit significant correlations (0.56, 0.74, 0.50, 0.31, 0.16, and 0.30, respectively) with total trace element concentrations of all horizons of the NAD. Manganese shows the best inter-element correlation (0.33) with these associated total concentrations. Total Fe has one of the strongest relationships, explaining 55 and 30% of the variation in total trace element concentrations for all horizons in the NAD and AD, respectively.

Statistical prediction of terrestrial gamma radiation dose rate based on geological features and soil types in Kota Tinggi district, Malaysia

A statistical prediction of terrestrial gamma radiation dose rate has been performed, covering the Kota Tinggi district of Peninsular Malaysia. The prediction has been based on geological features and soil types. The purpose of this study is to provide a methodology to statistically predict the gamma radiation dose rate with minimum surveying in an area. Results of statistical predictions using the hypothesis test were compared with the actual dose rate obtained by measurements.

Correct use of the contact angle in the evaluation of the protective action induced from polymer coating on the stone

The control of the protective efficacy obtained on the stone by treatments with polymers is commonly performed through the measure of the static contact angle as it is described by the norm UNI 10921. However this approach does not allow an easy interpretation of the results, because of the porosity and of the heterogeneity of the stone surface, which represent an obstacle to the analysis. Moreover the commonest interpretation of this technique can often bring to important errors. The measure of the static contact angle substantially corresponds to the measure of the so-called "advancing" contact angle and it allows only to verify if on the surface a hydrophobic material is present; unfortunately it cannot determine if the stone is effectively protected. Vice versa, both, the measure of the "true" equilibrium contact angle obtained through a new technique called VIECA, and the measure of the receding contact angle give more coherent parameters which better correlate with the data of absorption of water by capillarity. The equilibrium contact angle corresponds to an "average" description of the surface, the receding angle corresponds, by excess, to the condition of maximum penetration of the liquid by capillarity. From the knowledge of the equilibrium angle of the protective polymer and from the measure of the advancing and receding angles of the protected stone, it is certainly possible to determine what is the minimum polymer quantity to obtain an almost homogeneous stone protection.

Diagnostics and conservation of a gres work by Zauli placed in the Bucci park of Faenza

Glazed more or less degraded ceramic works, made by the sculpture artist Carlo Zauli from Faenza, were studied. One of them, placed outside in the Bucci park, showed a lot of fractures, lacunas and biological decay. Therefore, a diagnostic study, a preliminary in situ restoration and a monitoring for over two years were carried out in order to verify the stability of the work.

Origin and Migration of the Alpine Iceman

The Alpine Iceman provides a unique window into the Neolithic-Copper Age of Europe. We compared the radiogenic (strontium and lead) and stable (oxygen and carbon) isotope composition of the Iceman's teeth and bones, as well as 40Ar/39Ar mica ages from his intestine, to local geology and hydrology, and we inferred his habitat and range from childhood to adult life. The Iceman's origin can be restricted to a few valleys within approximately 60 kilometers south(east) of the discovery site. His migration during adulthood is indicated by contrasting isotopic compositions of enamel, bones, and intestinal content. This demonstrates that the Alpine valleys of central Europe were permanently inhabited during the terminal Neolithic.

Branched aliphatic alkanes with quaternary substituted carbon atoms in modern and ancient geologic samples

A pseudohomologous series of branched aliphatic alkanes with a quaternary substituted carbon atom (BAQCs, specifically 2,2-dimethylalkanes and 3,3- and 5,5-diethylalkanes) were identified in warm (65 degrees C) deep-sea hydrothermal waters and Late Cretaceous black shales. 5,5-Diethylalkanes were also observed in modern and Holocene marine shelf sediments and in shales spanning the last 800 million years of the geological record. The carbon number distribution of BAQCs indicates a biological origin. These compounds were observed but not identified in previous studies of 2.0 billion- to 2.2 billion-year-old metasediments and were commonly misidentified in other sediment samples, indicating that BAQCs are widespread in the geological record. The source organisms of BAQCs are unknown, but their paleobiogeographic distribution suggests that they have an affinity for sulfides and might be nonphotosynthetic sulfide oxidizers.

Probable extirpation of a breeding colony of Short-tailed Albatross (Phoebastria albatrus) on Bermuda by Pleistocene sea-level rise

Albatrosses (Diomedeidae) do not occur in the North Atlantic Ocean today except as vagrants, although five species were present in the early Pliocene. No fossil breeding sites of albatrosses were known previously. The timing of extinction of albatrosses in the North Atlantic was likewise unknown. Deposits that formed near present-day sea level along the southeastern shore of Bermuda contain remains of a former breeding colony and include intact eggshells and bones of embryos, juveniles, and adults of Short-tailed Albatross (Phoebastria albatrus), a critically endangered species now confined to a few islets in the northwestern Pacific Ocean. These deposits are correlated with the middle Pleistocene Lower Town Hill Formation, which at other sites have a radiometric age of 405,000 years ago. This equates with the marine isotope stage 11 interglacial, which culminated in a rise in sea-level to >+20 m. Bones of a juvenile Short-tailed Albatross were also found in beach deposits at +21.3 m from this same interglacial. We interpret the extirpation of albatrosses on Bermuda as probably resulting from lack of nesting sites protected from storm surges over the little emergent land that remained at the height of the marine isotope stage 11 sea level rise.

Landform classification for land use planning in developed areas: an example in Segovia Province (central Spain)

Landform-based physiographic maps, also called land systems inventories, have been widely and successfully used in undeveloped/rural areas in several locations, such as Australia, the western United States, Canada, and the British ex-colonies. This paper presents a case study of their application in a developed semi-urban/suburban area (Segovia, Spain) for land use planning purposes. The paper focuses in the information transfer process, showing how land use decision-makers, such as governments, planners, town managers, etc., can use the information developed from these maps to assist them. The paper also addresses several issues important to the development and use of this information, such as the goals of modern physiography, the types of landform-based mapping products, the problem of data management in developed areas, and the distinctions among data, interpretations, and decisions.

Baseline nitrate concentration in groundwater of the Chalk in south Dorset, UK

Determining the degree of nitrate pollution in Chalk groundwater is difficult without a clear understanding of concentrations naturally present. In the UK, a general shortage of long-term records of nitrate concentrations in Chalk groundwater prevents a full quantification of baseline concentrations. This paper presents late nineteenth and early twentieth century data on nitrate concentrations in Chalk groundwater in south Dorset, UK and compares them with corresponding data for the last 25 years. The nitrate record is instructive in (1) providing an insight into the baseline nitrate concentration of groundwater; (2) defining the level of nitrate pollution in potable supplies from the Chalk aquifer; and (3) identifying the long-term variations in local nitrate concentrations. Over a period exceeding 100 years mean nitrate concentrations increased from 1.04 mg NO3-Nl(-1) to 6.37 mg NO3-Nl(-1). Anthropogenic modification of the local groundwater composition is not evident in the early nitrate record. Nitrate data throughout this early period reflect natural background concentrations of approximately 1 mg NO3-Nl(-1). Intensified fertilizer use and increased livestock numbers are suggested as the fundamental cause of the rise in nitrate concentrations. The implications of the nitrate record for regional hydrogeological processes are discussed.

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.

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.

Magnetic response of soils and vegetation to heavy metal pollution--a case study

Fast and cost-effective detection of industrial pollution can significantly promote its ecological, economic, and social assessment. A magnetometric method, used for qualitative determination of anthropogenic contamination, meets these requirements but needs further development in more quantitative terms. It could be used successfully in numerous cases when the heavy metals coexist with strongly magnetic iron oxide particles in the source dust. We present an integrated magnetic and geochemical study that examines the utility of magnetometric techniques for rapid, qualitative detection of metallic pollutants in soils and vegetation. The new aspect of our approach, in comparison with previously published articles on this subject, is the combined investigation (magnetic and geochemical) of both soils and vegetation, thus using an additional medium for employing the magnetometry as a pollution proxy at a site. The study area is a small (approximately 3 km2) region in the suburbs of Sofia (Bulgaria), with the main pollution source being a metallurgical factory. Soil samples have been taken from the topmost 20 cm from private gardens, located at different distances from the factory. Vegetation samples were taken from ryegrass (both leaves and roots) and leaves from two kinds of deciduous trees (maple and acacia). The results show that both vegetation and soils are characterized by enhanced magnetic properties, compared to background material, which is due to the presence of magnetite particles of anthropogenic origin accompanying heavy metal emissions. SEM images and microprobe analyses reveal the presence of a significant amount of particles, containing heavy metals (including iron) in vegetation samples taken close to the main pollution source. Correlation analyses show a statistically significant link (correlation coefficients ranging from 0.6 to 0.7) between magnetic susceptibility and the main heavy metals (Cu, Zn, Pb) in soil samples, indicating that the magnetic susceptibility can provide a proxy method for identifying the relative contribution of industrial pollution in soils and vegetation, that is reliable, inexpensive, and less time-consuming than standard chemical analyses.

Pyroclastic fluoride in ground waters in some parts of Tadpatri Taluk, Anantapur district, Andhra Pradesh

Fluorosis is a disease affecting the teeth and bones and caused by excessive ingestion of fluoride through drinking water. Fluoride concentration in ground water samples of the study area varies from 1.2 to 2.1 ppm., which is much above the permissible limit. The probable source of fluoride in ground water is fluoride bearing minerals like apatite, micas and clay minerals etc., present in the country rocks like shales and pyroclastic materials of the study area. The sample survey is carried out to know the incidence of fluorosis in this area which reveals that more than 43% of the inhabitants are affected by dental fluorosis and 0.4% by skeletal fluorosis.

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.

Dissolution of entrapped DNAPLs in variable aperture fractures: experimental data and empirical model

An appreciation of the dissolution from entrapped nonaqueous phase liquids (NAPLs) in fractures is essential as we attempt to understand and predict the fate of NAPLs present in fractured rock systems. Eight long-term dissolution experiments using 1,1,1-trichloroethane and trichloroethylene were conducted in two laboratory-scale dolomitic limestone variable aperture fractures under various conditions. Between 560 and 2600 fracture volumes of water were passed through the fractures resulting in the removal of 10-60% of the initial mass trapped. The effluent concentration profiles revealed three distinct and characteristic stages of dissolution: an initial pseudosteady stage, a transient stage, and a tailing stage. On average, 8% of the initial volume of NAPL present was removed during the initial pseudosteady stage. Data from the dissolution experiments were used in conjunction with statistical techniques to develop a continuous empirical model describing the initial pseudosteady and transient stages of dissolution. The model was used to successfully replicate effluent concentration data from two separate and independent dissolution experiments. The experimental results provide an indication of the expected dissolution behavior of entrapped NAPLs, while the developed model is a useful tool for characterizing mass transfer rates in variable aperture fractures.

Biofilm hydrous manganese oxyhydroxides and metal dynamics in acid rock drainage

Biofilms in shallow, tailings-associated acid rock drainage (ARD) accumulated metals from May to September, indicating scavenging is stable within these biological solids over seasonal time frames. Results indicate a doubling (Mn, Cr) to over a 6-fold increase (Ni, Co) in biofilm metal concentrations. Biofilm oxygen and pH gradients measured over diel time scales with microelectrodes were observed to be both spatially and temporally variable, indicating that biofilms are highly dynamic geochemical environments. Biofilm metal retention and affinities were element specific indicating different processes control their sequestration. Metals were specifically scavenged by the organic constituents of the biofilm itself (Ni, Co) and associated biominerals of amorphous Mn oxyhydroxides (HMO; Ni, Co, and Cr). Results are consistent with sorption and coprecipitation processes controlling Ni and Co biofilm association, while Cr dynamics appear linked to those of Mn through redox processes. Biofilm HMO concentrations increased seasonally but showed significant diel fluctuations, indicating that both formation and dissolution processes occurred over rapid time scales in these biofilms. Biofilm HMO concentrations increased nocturnally but decreased during daylight hours to late afternoon minima. Under the geochemical conditions of the streams, observed HMO formation rates can only be explained by microbial catalysis. These results are the first to quantitatively examine microbial biofilm metal dynamics using microscale, geochemical techniques at both diel and seasonal time scales. They provide strong evidence for the significant role that microbial activity can play in metal geochemistry in natural environments.

A biogeochemical cycle for aluminium?

The elaboration of biogeochemical cycles for elements which are known to be essential for life has enabled a broad appreciation of the homeostatic mechanisms which underlie element essentiality. In particular they can be used effectively to identify any part played by human activities in element cycling and to predict how such activities might impact upon the lithospheric and biospheric availability of an element in the future. The same criteria were the driving force behind the construction of a biogeochemical cycle for aluminium, a non-essential element which is a known ecotoxicant and a suspected health risk in humans. The purpose of this exercise was to examine the concept of a biogeochemical cycle for aluminium and not to review the biogeochemistry of this element. The cycle as presented is rudimentary and qualitative though, even in this nascent form, it is informative and predictive and, for these reasons alone, it is deserving of future quantification. A fully fledged biogeochemical cycle for aluminium should explain the biospheric abundance of this element and whether we should expect its (continued) active involvement in biochemical evolution.

Estimating deep recharge rates beneath an interlobate moraine using temperature logs

The Sandilands area of southeastern Manitoba contains an interlobate moraine that is a major ground water recharge area. Underlying the highly permeable sediments of the moraine are up to 100 m of till and the subcrop of the Winnipeg Formation, which contains a major sandstone aquifer. Ground water flow within the till is examined using high-resolution temperature profiles and solutions to the differential equation for heat flow in porous media. These analyses indicate that recharge to the sandstone aquifer is occurring at a rate of approximately 2 x 10(-8) m/sec beneath the moraine, which is in agreement with recharge rates determined by conventional ground water hydraulics (10(-7) to 10(-10)(m/sec) and another study using multiple environmental tracers (1 x 10(-9) to 6 X 10(-9) m/sec). The use of temperature to determine ground water flux is not limited by half-lives as many environmental tracers are, and this allows for cost-effective estimation of recharge and discharge rates over longer periods.

Ground water/surface water interaction in a fractured rock aquifer

In a recent field study of ground water/surface water interaction between a bedrock stream and an underlying fractured rock aquifer, it was determined that the majority of ground water discharge occurred through sparsely located vertical fractures. In this paper, the dominant mechanisms governing ground water/surface water exchange in such an environment are investigated using a numerical model. The study was conducted using several conceptual models based on the field study results. Although the field results provided the motivation for the modeling study, it was not intended to match modeling and field results directly. In addition, the extent of capture zones for discharging or recharging fractures was explored. The results of this study are intended to provide a better understanding of contaminant migration in the vicinity of bedrock streams. Based on the numerical results, the rate of ground water discharge (or recharge) was found to depend on the aperture size of the discharging feature, and on the distribution of hydraulic head with depth within the fracture network. It was determined that the extent of both the capture zone and reverse capture zone for an individual fracture can be extremely large, and will be determined by the height of the stream stage, the fracture apertures of the network, and the hydraulic-head distribution within the network. Because both the stream stage and the hydraulic-head distribution are transient, the size of the capture zone and/or the reverse capture zone for an individual fracture may change significantly over time. As a result, the migration path for contaminants within the fracture network and between the surface and subsurface will also vary significantly with time.

Biogeochemistry and isotope geochemistry of a landfill leachate plume

The biogeochemical processes were identified which improved the leachate composition in the flow direction of a landfill leachate plume (Banisveld, The Netherlands). Groundwater observation wells were placed at specific locations after delineating the leachate plume using geophysical tests to map subsurface conductivity. Redox processes were determined using the distribution of solid and soluble redox species, hydrogen concentrations, concentration of dissolved gases (N(2), Ar, and CH(4)), and stable isotopes (delta15N-NO(3), delta34S-SO(4), delta13C-CH(4), delta2H-CH(4), and delta13C of dissolved organic and inorganic carbon (DOC and DIC, respectively)). The combined application of these techniques improved the redox interpretation considerably. Dissolved organic carbon (DOC) decreased downstream in association with increasing delta13C-DOC values confirming the occurrence of degradation. Degradation of DOC was coupled to iron reduction inside the plume, while denitrification could be an important redox process at the top fringe of the plume. Stable carbon and hydrogen isotope signatures of methane indicated that methane was formed inside the landfill and not in the plume. Total gas pressure exceeded hydrostatic pressure in the plume, and methane seems subject to degassing. Quantitative proof for DOC degradation under iron-reducing conditions could only be obtained if the geochemical processes cation exchange and precipitation of carbonate minerals (siderite and calcite) were considered and incorporated in an inverse geochemical model of the plume. Simulation of delta13C-DIC confirmed that precipitation of carbonate minerals happened.