CO and NO2 pollution in a long two-way traffic road tunnel: investigation of NO2/NOx ratio and modelling of NO2 concentration

The CO, NO and NO2 concentrations, visibility and air flow velocity were measured using continuous analysers in a long Norwegian road tunnel (7.5 km) with traffic in both directions in April 1994 and 1995. The traffic density was monitored at the same time. The NO2 concentration exceeded Norwegian air quality limits for road tunnels 17% of the time in 1994. The traffic through the tunnel decreased from 1994 to 1995, and the mean NO2 concentration was reduced from 0.73 to 0.22 ppm. The ventilation fan control, based on the CO concentration only, was unsatisfactory and the air flow was sometimes low for hours. Models for NO2 concentration based on CO concentration and absolute air flow velocity were developed and tested. The NO2/NOx ratio showed an increase for NOx levels above 2 ppm; a likely explanation for this phenomenon is NO oxidation by O2. Exposure to high NO2 concentrations may represent a health risk for people with respiratory and cardiac diseases. In long road tunnels with two-way traffic, this study indicates that ventilation fan control based on CO concentration should be adjusted for changes in vehicle CO emission and should be supplemented by air flow monitoring to limit the NO2 concentration.     

Partitioning of mercury onto suspended sediments in estuaries

Radiochemical partitioning experiments using 203Hg have been undertaken with mixtures of river, seawater and sediment samples taken from three geochemically contrasting UK estuaries: the Plym, Beaulieu and Mersey. Species of dissolved Hg were determined using reversed-phase C18 chelating columns and particulate species were determined by sequential leaching with 1 M NH4OAc and 1 M HCl. Mercury had a high particle reactivity with partition coefficients, KDs, ranging from 10(4) to 5 x 10(5) ml g(-1), depending on salinity, the chemical composition of the end-member waters, and on the physico-chemical characteristics of the sediment. Dissolved organic matter present in the waters (humic substances and/or anthropogenic compounds) was found to be the main factor governing the forms of dissolved Hg and their reactivity. From the spiked 203Hg, up to 95% of the dissolved metal was retained on the C18 columns for the Mersey waters, whereas this fraction was < 60% in the Plym and Beaulieu waters. Quasi-irreversible adsorption of Hg onto particles from each estuary was observed over a time-scale of a few hours and < 20% of total particulate Hg was released by the sequential leach. In this paper, physico-chemical processes are proposed to explain the estuarine behaviour of Hg and the results are discussed in terms of Hg availability in estuarine systems.     

Chemical monitoring and evaluation of the water quality of the Douro River at the Crestuma-Lever dam

Water taken from the Crestuma-Lever dam on the Douro River was evaluated considering the Portuguese Decree-law no. 236/98 of 1st August, 1998. This paper presents the metrological characteristics, validation of analytical methodologies and the data obtained from seasonal samplings. The test parameters selected are: temperature, pH, chloride, conductivity, carbon dioxide, alkalinity, hardness, oxidability, dissolved oxygen, BOD5, total suspended solids, sulfide, phosphate, silica, ammonium, nitrite, nitrate, sulfate, sodium, potassium, calcium, magnesium, iron, manganese, copper and zinc. From data analysis we can conclude that the water presented the following characteristics: a pH situated in the neutral zone; a median mineralization; a medium hardness; well oxygenated water; and a carbonate hardness exclusively due to bicarbonates. The temperature, pH, dissolved oxygen, ammonia, chlorides, sulfates, copper, zinc and BOD5 were compared with the legal limits presented in annexes XXI and I of Decree-law 236/98. The results relating to total hardness, nitrites, calcium, magnesium, sodium, potassium, aluminium, sulfides and oxidability were compared with the legal values in annex VI as there are no limits relating to these parameters in annexes XXI and I.     

SI-traceable certification of Cu, Cr, Cd and Pb in sediment and fly ash candidate reference materials

Many fields in environmental analytical chemistry deal with very low limits and thresholds as set by governmental legislations or transnational regulations. The need for the accuracy, comparability and traceability of analytical measurements in environmental analytical chemistry has significantly increased and total uncertainties are even asked for by accreditation bodies of environmental laboratories. This paper addresses achieving these goals to guarantee accuracy, quality control, quality assurance or validation of a method by means of certified reference materials. The assessment of analytical results in certified reference materials must be as accurate as possible and every single step has to be fully evaluated. This paper presents the SI-traceable certification of Cu, Cr, Cd and Pb contents in geological and environmentally relevant matrices (three sediments and one fly ash sample). Certification was achieved using isotope dilution (ID) ICPMS as a primary method of measurement. In order to reduce significantly the number of analytical steps and intermediate samples a multiple spiking approach was developed. The full methodology is documented and total uncertainty budgets are calculated for all certified values. A non-element specific sample digestion process was optimised. All wet chemical digestion methods examined resulted in a more or less pronounced amount of precipitate. It is demonstrated that these precipitates originate mainly from secondary formation of fluorides (essentially CaF2) and that their formation takes place after isotopic equilibration. The contribution to the total uncertainty of the final values resulting from the formation of such precipitates was in general < 0.1% for all investigated elements. Other sources of uncertainty scrutinised included the moisture content determination, procedural blank determination, cross-contamination from the different spike materials, correction for spectral interferences, instrumental background and deadtime effects, as well as the use of either certified values or IUPAC data in the IDMS equation. The average elemental content in the sediment samples was 30-130 micrograms g-1 for Pb, 0.5-3 micrograms g-1 for Cd and 50-70 micrograms g-1 for Cu. Cr was measured in one sample and was about 60 micrograms g-1. The concentrations in the fly ash sample were up to 2 orders of magnitude higher. Expanded uncertainty for the investigated elements was about 3% (coverae factor k = 2) except for Cr, (measured by high resolution ICPMS), for which the expanded uncertainty was about 7% (k = 2).     

Improvement of the BCR three step sequential extraction procedure prior to the certification of new sediment and soil reference materials

The Standards, Measurements and Testing Programme (formerly BCR) of the European Commission proposed a three-step sequential extraction procedure for sediment analysis, following extensive expert consultations and two interlaboratory studies. This scheme was recently used to certify the extractable trace element contents of a sediment reference material (CRM 601). Although this procedure offers a means to ensure the comparability of data in this field, some difficulties concerning the interlaboratory reproducibility still remain, and a new project is currently being conducted to determine the causes of poor reproducibility in the extraction scheme. The final objective of the project is the certification of new sediment and soil reference materials for their extractable contents of Cd, Cr, Cu, Ni, Pb and Zn. This paper presents the results of a small-scale interlaboratory study, which aimed to test a revised version of the extraction schemes by comparing the original and the modified protocols using the CRM 601 sample. This work offers an improvement to the BCR sequential extraction procedure through intercomparison exercises. This improved procedure will allow the obtaining of CRMs to validate analytical data in the analysis of soils and sediments, and it will also facilitate comparability of data in the European Union.     

Characterization of microbial communities from coastal waters using microarrays

Molecular methods, including DNA probes, were used to identify and enumerate pathogenic Vibrio species in the Chesapeake Bay; our data indicated that Vibrio vulnificus exhibits seasonal fluctuations in number. Our work included a characterization of total microbial communities from the Bay; development of microarrays that identify and quantify the diversity of those communities; and observation of temporal changes in those communities. To identify members of the microbial community, we amplified the 16S rDNA gene from community DNA isolated from a biofilm sample collected from the Chesapeake Bay in February, 2000. The resultant 75 sequences were 95% or more similar to 7 species including two recently described Shewanella species, baltica and frigidimarina, that have not been previously isolated from the Chesapeake. When the genera of bacteria from biofilm after culturing are compared to those detected by subcloning amplified 16S fragments from community DNA, the cultured sample exhibited a strong bias. In oysters collected in February, the most common bacteria were previously unknown. Based on our 16S findings, we are developing microarrays to detect these and other microbial species in these estuarine communities. The microarrays will detect each species using four distinct loci, with the multiple loci serving as an internal control. The accuracy of the microarray will be measured using sentinel species such as Aeromonas species, Escherichia coli, and Vibrio vulnificus. Using microarrays, it should be possible to determine the annual fluctuations of bacterial species (culturable and non-culturable, pathogenic and non-pathogenic). The data may be applied to understanding patterns of environmental change; assessing the health of the Bay; and evaluating the risk of human illness associated with exposure to and ingestion of water and shellfish.     

Sediment quality in the Douro river estuary based on trace metal contents, macrobenthic community and elutriate sediment toxicity test (ESTT)

The aim of this study was to evaluate the sediment quality in the mesotidal Douro River estuarine environment, in order to identify areas where sediment contamination could cause ecosystem degradation. Samples were obtained in five locations and sediment characterised for grain size, total organic matter, total-recoverable metals (Al, Fe, Cu, Pb, Cr, Ni, Cd, Zn and Mn), as well as acid volatile sulfide (AVS) and simultaneously extracted metals (SEM). In situ effects were evaluated by examining the macrobenthic community structure. An elutriate sediment toxicity test (ESTT) was used to estimate the amount of metals and nutrients that could be exchanged with the water column through resuspension, and its positive or negative effects on the growth of the micro-alga Emiliania huxleyi in a 10 day test. Anthropogenic metal contamination was identified at the north bank of the Douro estuary, with deleterious effects on the macrobenthic community, namely decrease in number of species and diversity. This contamination could possibly also be toxic for water column organisms, in case of resuspension, as shown by the ESTT. Sediments from the salt marsh at the south bank showed an impoverished macrobenthic community and elutriate toxicity, which appeared to be due to anaerobic conditions. This study clearly shows the usefulness of the ESST approach to assess the biological effect of resuspension of estuarine sediments.     

Assessment of Metal Contamination in Doñana National Park (Spain) using Crayfish (Procamburus Clarkii)

Water quality assessment in the Aznalcollar area was attempted using multivariate methods based on heavy metal concentrations in red swamp crayfish (Procamburus clarkii). Trace levels of four heavy metals, copper (Cu), zinc (Zn), cadmium (Cd) and lead (Pb), were detected in crayfish from eleven different stations. Principal component analysis (PCA) highlighted a gradient of contamination between the sampling stations. Cluster analysis (CA) distinguished three groups of stations. Discriminant analysis also differentiated three groups. The group centroids of the first discriminant function were used to devise an index that varies according to the source of the crayfish. These standardized values are proposed for use as a water quality index. The ability of this index to successfully predict environmental quality was proved with random samples.     

Risk assessment of water pollutants

The sources of toxic xenobiotics and different factors such as ecological diversity, differences in comparative anatomy, physiology and biochemistry, food chain variation, interrelationship within species and life span, etc., are considered during risk assessment of pollutants, and their impact on aquatic ecotoxicology is identified. A fugacity and multimedia compartment model is suggested, based on toxicodynamic (toxicity of the chemical) and toxicokinetic (metabolism of the chemical) considerations to predict and screen the behaviour of pollutants quantitatively in the aquatic environment. The significance of the risk analysis approach in anticipatory actions and regulation of pollution levels is discussed.     

Monitoring the condition of the Canadian forest environment: The relevance of the concept of ‘ecological indicators’

The Canadian forest environment is characterized by high spatial and temporal variability, especially in the west. Our forests vary according to climate, landform, and surficial geology, and according to the type, intensity, extent of, and the time since the last disturbance. Most Canadian forests have had a history of repeated acute, episodic disturbance from fire, insects, wind, diseases and/or logging, with a frequency of disturbance varying from a few decades to many centuries. These sources of variability have resulted in a complex and continually changing mosaic of forest conditions and stages of successional development.Monitoring the quality of this dynamic forested landscape mosaic is extremely difficult, and in most cases the concept of a relatively simple index of forest ecosystem quality or condition (i.e. an ecological indicator) is probably inappropriate. Such ecological indicators are better suited for monitoring chronic anthropogenically induced disturbances that are continuous in their effect (e.g. acid rain, heavy metal pollution, air pollution, and the greenhouse effect) in ecosystems that, in the absence of such chronic disturbance, exhibit very slow directional change (e.g. lakes, higher order streams and rivers). Monitoring the effects of a chronic anthropogenic disturbance to forest ecosystems to determine if it is resulting in a sustained, directional alteration of environmental quality will require a definition of the expected pattern of episodic disturbance and recovery therefrom (i.e. patterns of secondary succession in the absence of the chronic disturbance). Only when we have such a temporal fingerprint of forest ecosystem condition for normal patterns of disturbance and recovery can we determine if the ecosystem condition is being degraded by chronic human-induced alteration of the environment. Thus, degradation is assessed in terms of deviations from the expected temporal pattern of conditions rather than in terms of an instantaneous assessment of any particular condition. The concept of ecological rotation (the time for a given ecosystem to recover from a given disturbance back to some defined successional condition) is useful in the definition of these temporal fingerprints. This requires information on the intensity of disturbance, the frequency of disturbance, and the rate of successional recovery. Only when all three of these are known or estimated can statements be made as to whether the ecosystem is in a longterm sustainable condition or not.The somewhat overwhelming complexity of this task has led forest ecologists to use ecosystem-level computer simulation models. Appropriately structured and calibrated models of this type can provide predictions of the overall temporal patterns of ecosystem structure and functions that can be expected to accompany a given frequency and character of episodic disturbance. Such models can also be used to examine the long-term consequences of chronic disturbances such as acid rain and climatic change. Predictive ecosystem-level models should be used in conjunction with some method of stratifying the inherent spatial biophysical variability of the forest environment, such as the biogeoclimatic classification system of British Columbia.