Microbiological characteristics in a zero-valent iron reactive barrier

Zero-valent iron (Fe⁰)-based permeable reactive barriertreatment has been generating great interest for passivegroundwater remediation, yet few studies have paid particularattention to the microbial activity and characteristics withinand in the vicinity of the Fe⁰-barrier matrix. The presentstudy was undertaken to evaluate the microbial population andcommunity composition in the reducing zone of influence byFe⁰ corrosion in the barrier at the Oak Ridge Y-12 Plantsite. Both phospholipid fatty acids and DNA analyses were usedto determine the total microbial population and microbialfunctional groups, including sulfate-reducing bacteria,denitrifying bacteria, and methanogens, in groundwater andsoil/iron core samples. A diverse microbial community wasidentified in the strongly reducing Fe⁰ environment despitea relatively high pH condition within the Fe⁰ barrier (up topH 10). In comparison with those found in the backgroundsoil/groundwater samples, the enhanced microbial populationranged from 1 to 3 orders of magnitude and appeared to increase from upgradient of the barrier to downgradient soil. Inaddition, microbial community composition appeared to change overtime, and the bacterial types of microorganismsincreased consistently as the barrier aged. DNA analysisindicated the presence of sulfate-reducing and denitrifyingbacteria in the barrier and its surrounding soil. However, theactivity of methanogens was found to be relatively low,presumably as a result of the competition by sulfate/metal-reducing bacteria and denitrifying bacteria because of the unlimited availability of sulfate and nitrate in the site groundwater. Results of this study provide evidenceof a diverse microbial population within and in the vicinity ofthe iron barrier, although the important roles of microbial activity, either beneficially or detrimentally, on the longevityand enduring efficiency of the Fe⁰ barriers are yet to be evaluated.     

From proposal to decision: Suggestions for tightening up the “NEPA process”

Although the process of documenting compliance with NEPA (the National Environmental Policy Act) requires no drastic revisions, it can be managed more rigorously. Suggestions for revision can be grouped under five major steps: 1) getting a complete proposal from the applicant; 2) getting the decision-making process onto the right decision-making path; 3) modifying the applicant's proposal 4) going down a shorter path through the EA/FONSI (environmental assessment and finding of no significant impact) or through categorical exclusion review; and 5) going down the longer path through the EIS. Step 2 is perhaps the most critical, because there a decision must be made whether to write an EA/FONSI or an EIS, on the basis of whether the proposal would “significantly affect … the … environment.” In the past, this decision has not always been made promptly or rigorously. Accordingly, we suggest that the agency responsible for NEPA compliance should develop a system (a “black box”), consisting of a core group of specialists working with an interdisciplinary team, using sophisticated techniques for modeling impacts and directing both their research and their writing according to the concept of significance. By determining more efficiently and reliably whether the impacts of a proposal would be significant, such an approach would improve management of the total process.     

Quantitative PCR analysis of house dust can reveal abnormal mold conditions

Indoor mold concentrations were measured in the dust of moldy homes (MH) and reference homes (RH) by quantitative PCR (QPCR) assays for 82 species or related groups of species (assay groups). About 70% of the species and groups were never or only rarely detected. The ratios (MH geometric mean : RH geometric mean) for 6 commonly detected species (Aspergillus ochraceus, A. penicillioides, A. unguis, A. versicolor, Eurotium group, and Cladosporium sphaerospermum) were >1 (Group I). Logistic regression analysis of the sum of the logs of the concentrations of Group I species resulted in a 95% probability for separating MH from RH. These results suggest that it may be possible to evaluate whether a home has an abnormal mold condition by quantifying a limited number of mold species in a dust sample. Also, four common species of Aspergillus were quantified by standard culturing procedures and their concentrations compared to QPCR results. Culturing underestimated the concentrations of these four species by 2 to 3 orders of magnitude compared to QPCR.     

Evaluation of forest nutrition based on large-scale foliar surveys: are nutrition profiles the way of the future?

This paper introduces the use of nutrition profiles as a first step in the development of a concept that is suitable for evaluating forest nutrition on the basis of large-scale foliar surveys. Nutrition profiles of a tree or stand were defined as the nutrient status, which accounts for all element concentrations, contents and interactions between two or more elements. Therefore a nutrition profile overcomes the shortcomings associated with the commonly used concepts for evaluating forest nutrition. Nutrition profiles can be calculated by means of a neural network, i.e. a self-organizing map, and an agglomerative clustering algorithm with pruning. As an example, nutrition profiles were calculated to describe the temporal variation in the mineral composition of Scots pine and Norway spruce needles in Finland between 1987 and 2000. The temporal trends in the frequency distribution of the nutrition profiles of Scots pine indicated that, between 1987 and 2000, the N, S, P, K, Ca, Mg and Al decreased, whereas the needle mass (NM) increased or remained unchanged. As there were no temporal trends in the frequency distribution of the nutrition profiles of Norway spruce, the mineral composition of the needles of Norway spruce needles subsequently did not change. Interpretation of the (lack of) temporal trends was outside the scope of this example. However, nutrition profiles prove to be a new and better concept for the evaluation of the mineral composition of large-scale surveys only when a biological interpretation of the nutrition profiles can be provided.     

Competitive Retention of Lead and Cadmium on an Agricultural Soil

Lead and cadmium contamination of an agricultural soil has been studied using batch and column experiments. Thermodynamics of theretention phenomena may be represented by a Langmuir isotherm foran aqueous metal concentration up to 100 mg L^-1. First order kinetics with respect to the solid phase yield good predictabilityfor both batch and column experiments. Kinetics and thermodynamics of lead retention predominate over those ofcadmium. As a consequence, lead is preferentially retainedand can even displace sorbed cadmium. In the event of anspill involving both metals, cadmium would move further inthe soil and its aqueous concentration downstream could beeven higher than that of the influent solution, increasingpotential risks. A two-region model has been used to fit all the experimental results. Satisfactory predictions for column experiments are obtained with parameters which are consistent with those obtained for the batch experiments, for which sorption is described by a Langmuir isotherm including competitive retention.     

Higher Plants As Bioindicators Of Sulphur Dioxide Emissions In Urban Environments

The evaluation of certain vascular plants that grow in the city of Madrid as biomonitors of SO₂ air pollution in urban environments has been carried out. Total concentration of sulphur in leaves of the chosen higher plants as well as other parameters in close relation to this contaminant (visible injury symptoms, chlorophyll a- and b-content and peroxidase activity) have been determined in order to study the spatial distribution and temporal changes in SO₂ deposition. Results obtained show that coniferous species such as Pinus pinea, were more sensitive to SO₂ atmospheric concentration than leafy species as Quercux ilex subspecies ballota and, in the same way, bush species, such asPyracantha coccinea and Nerium oleander, were more sensitive than wooded species, such as Cedrus deodaraandPinus pinea, respectively. There is a higher accumulation of sulphur in vegetable species located near highways and dense traffic incidence roads and near areas with high density of population. The minimum values for accumulation of SO₂ were registered in winter and spring seasons (from January to April) due to the vegetative stop; while maximum values are obtained during the summer season (from June to September), due to the stoma opening. The highest increments in sulphur concentration, calculated as the difference between two consecutive months, are obtained in May and June for all considered species except forCedrus deodara and Pyracantha coccinea, both species have few seasonal changes during the whole year. Some species are more sensitive to natural washing than others, showing a decrease in sulphur concentration after rainfall periods.     

The study of age influence on human bone lead metabolism by using a simplified model and X-ray fluorescence data

Long term lead metabolism in the human body has never been fully understood due to the lack of human data in this area. The technological improvement of bone lead measurement systems has made bone lead data of substantial populations available. In this study, a set of X-ray fluorescence bone lead data was used to test Leggett's lead metabolism model (R. W. Leggett, Environ. Health Perspect., 1993a, 101, 598-616), especially the model of metabolism in bone. The data set includes the bone lead concentration of 539 occupationally exposed workers, of whom 327 were measured twice in five years. The bone lead concentrations of both cortical bone (tibia) and trabecular bone (calcaneus) were obtained by Cd-109 gamma-ray induced XRF measurement. The histories of blood lead concentration for these workers were used to regulate the input file of the model. The results show that the bone lead concentrations predicted by Leggett's model greatly underestimate the measured values, especially for older workers. This data set was then organized into five age groups. A new simplified model was applied to estimate the lead transfer rates between blood and lead compartments for these age groups. The original transfer rates and the new transfer rates are compared, and the differences are discussed. When the transfer rates derived from measured bone lead data were put into the input file of the model to replace the existing parameters, the predicted values were much closer to the measured values for both cortical bone and trabecular bone.     

Forest Area in Costa Rica: A Comparative Study of Tropical Forest Cover Estimates over Time

Forest area figures, at a given point in time and for a given region of interest, differ considerably, affecting the calculation of deforestation rates and thus confuse the political and scientific discussion on the state and change of the resource forest. This article discusses the variation of published forest cover figures, using Costa Rica as an example. A list of published figures on the forest cover of Costa Rica from 1940 onwards is analyzed. Reasons for the differences are hypothesized and discussed. These differences are mainly in the definition of forest and forest classes included, in the type of the studies conducted (mapping and/or sampling), in the precision of the estimates, and in the information sources used. It is concluded that part of the problem is inherent in the nature of the resource `forest'. Quality and completeness of the presentation of the forest cover estimates are a clue to their correct understanding and interpretation. The latter point being especially relevant, as forest cover data have both a technical-scientific and a political meaning and are used as relevant arguments in many discussions. In the example of Costa Rica, a general downward trend is observed up to about 1985/1990, whereas after that forest area figures are on the average at a markedly higher level. Some hypotheses for this change in the trend are discussed.     

Chromium speciation and fractionation in ground and surface waters in the vicinity of chromite ore processing residue disposal sites

Chromium concentrations of up to 91 mg l(-1) were found by ICP-OES for ground water from nine boreholes at four landfill sites in an area of S.E. Glasgow/S. Lanarkshire where high-lime chromite ore processing residue (COPR) from a local chemical works had been deposited from 1830 to 1968. Surface water concentrations of up to 6.7 mg l(-1) in a local tributary stream fell to 0.11 mg l(-1) in the River Clyde. Two independent techniques of complexation/colorimetry and speciated isotope dilution mass spectrometry (SIDMS) showed that Cr was predominantly (>90%) in hexavalent form (CrVI) as CrO4(2-), as anticipated at the high pH (7.5-12.5) of the sites. Some differences between the implied and directly determined concentrations of dissolved CrIII, however, appeared related to the total organic carbon (TOC) content. This was most significant for the ground water from one borehole that had the highest TOC concentration of 300 mg l(-1) and at which < 3% of Cr was in the form of CrVI. Subsequent ultrafiltration produced significant decreases in Cr concentration with decreasing size fractions, e.g. <0.45 microm, < 100 kDa, <30 kDa and < 1 kDa by the tangential-flow method. As this appeared related more to concentrations of humic substances than of TOC per se, horizontal bed gel electrophoresis of freeze-dried ultrafilter retentates was carried out to further characterise the CrIII-organic complex. This showed for the main Cr-containing fraction, 100 kDa-0.45 microm, that the Cr was associated with a dark brown band characteristic of organic (humic) matter. Comparison of gel electrophoresis and FTIR results for ultrafilter retentates of ground water from this borehole with those for a borehole at another site where CrVI predominated suggested the influence of carboxylate groups, both in reducing CrVI and in forming soluble CrIII-humic complexes. The implications of this for remediation strategies (especially those based on the addition of organic matter) designed to reduce highly mobile and carcinogenic Cr(VI)O4(2-) to the much less harmful CrIII as insoluble Cr(OH)3 are discussed.