The direct spectrophotometric analysis of aqueous nitrates is a simple analytical procedure but prone to interferences. A twelve-month study of the Preakness Brook in Wayne Township, New Jersey demonstrated that two wavelength, three wavelength, and second derivative calculation methods provide very different results from the same ultraviolet absorption spectrum. On average, the two wavelength and second derivative methods yielded the same concentration at each sample point over the entire study period. These methods provided concentration results closest to those obtained by ion chromatography and significantly lower than the three wavelength computation method. The degree of variation between the different computation methods was not consistent as it rose with increasing absorbances at wavelengths associated with interfering compounds. This variation was especially pronounced between May and August.

This paper presents an improved version of a general, process-based mass-balance model (LakeMab/LEEDS) for phosphorus in entire lakes (the ecosystem scale). The focus in this work is set on the boundary conditions, i.e., the domain of the model, and critical tests to reveal those boundary conditions using data from a wide limnological range. The basic structure of the model, and many key equations have been presented and motivated before, but this work presents several new developments. The LakeMab-model is based on ordinary differential equations regulating inflow, outflow and internal fluxes and the temporal resolution is one month to reflect seasonal variations. The model consists of four compartments: surface water, deep water, sediment on accumulation areas and sediment on areas of erosion and transportation. The separation between the surface-water layer and the deep-water layer is not done from water temperature data, but from sedimentological criteria (from the theoretical wave base, which regulates where wind/wave-induced resuspension of fine sediments occurs). There are algorithms for processes regulating internal fluxes and internal loading, e.g., sedimentation, resuspension, diffusion, mixing and burial. Critical model tests were made using data from 41 lakes of very different character and the results show that the model could predict mean monthly TP-concentrations in water very well (generally within the uncertainty bands given by the empirical data). The model is even easier to apply than the well-known OECD and Vollenweider models due to more easily accessed driving variables.

A lysimeter study was performed to monitor effects of elevated ozone on juvenile trees of Fagus sylvatica L. as well as on the plant-soil system. During a fumigation period over almost three growing seasons, parameters related to plant growth, phenological development and physiology as well as soil functions were studied. The data analyses identified elevated ozone to delay leaf phenology at early and to accelerate it at late developmental stages, to reduce growth, some leaf nutrients (Ca, K) as well as some soluble phenolics (hydroxycinnamic acid derivatives, total flavonol glycosides). No or very weak ozone effects were found in mobile carbon pools of leaves (starch, sucrose), and other phenolic compounds (flavans). Altered gene expression related to stress and carbon cycling corresponded well with findings from leaf phenology and chemical composition analyses indicating earlier senescence and oxidative stress in leaves under elevated ozone. Conversely in the soil system, no effects of ozone were detected on soil enzyme activities, rates of litter degradation and lysimeter water balances. Despite the fact that the three reported years 2003-2005 were climatically very contrasting including a hot and dry as well as an extremely wet summer, and also mild as well as cold winters, the influence of ozone on a number of plant parameters is remarkably consistent, further underlining the phytotoxic potential of elevated tropospheric ozone levels.

In this paper a three-step procedure is proposed to deal with ecological data, usually very complex in their treatment. The three steps – exploratory, confirmatory, and modelling phases – reflect the different methodological approaches necessary in each phase of the study. To illustrate the methodology, a case study is proposed, concerning the suitability of plants as pollution bioindicators. Samples of differently aged Pinus pinea L. needles were collected throughout 1 year in three different locations, whose human disturbance was known to be different. In the samples some morphological and functional parameters were measured, whose relation with the stress was already known. The exploratory analysis suggested pollution with human origin, the needle’s age, and the environmental conditions as the main factors of influence of damage. The confirmatory analysis confirmed both site and age as main factors and occasionally the sampling date. On this basis, some models were estimated separately for each site: models that best described the damage as function of age resulted non-linear and some of them with seasonal fluctuations. As a result, whereas the models described well enough the pollution temporal variation, the difference of pollution in the sites was best described by the different values of the models parameters in the different sites. In short, different pollution conditions are described better by the damage trend than by the individual measures. The three-step procedure resulted of high utility in outlining the most interesting relations to investigate through the modelling, the opportunity to model the indicators variation along time separately for each site, and to introduce the seasonal variation in some models.

The sorption behavior of sodium dodecylbenzene sulfonate (SDBS), an anionic surfactant, on marine sediments was systematically investigated. The experimental results showed that 100 min was required for the adsorption equilibrium. For the sediments treated by HCl and H₂O, sorption behavior of SDBS was fit with linear isotherm very well over the concentration range studied at 298 K. The sorption occurred primarily due to partition function of hydrophobic chains into organic carbon of sediments. Sorption of SDBS on H₂O₂-treated sediments was satisfactorily fit with Freundlich isotherm model and mainly through surface function of clay minerals in the sediment. The sorption was favorably influenced by the increased salinity, deceased pH and decreased temperature of seawater.

A fungal strain possibly capable of removing hexavalent chromium was to be isolated from industrial effluent from a leather factory located in the city of Guadalajara, state of Jalisco, Mexico. The strain was identified as Trichoderma inhamatum by the D1/D2 domain sequence of the 28S rDNA gene. Batch cultures of T. inhamatum in media containing initial Cr(VI) concentrations from 0.83 to 2.43 mM Cr(VI) were prepared. Experimental results suggest that the fungus is capable of transforming hexavalent chromium to trivalent chromium; a transformation of a highly toxic contaminant to a low toxic form. The specific and volumetric rates of Cr(VI) reduction by T. inhamatum cultures decreased as the initial Cr(VI) concentration increased. The fungus exhibited a remarkable capacity to tolerate and completely reduce Cr(VI) concentrations up to 2.43 mM. These results indicate that the T. inhamatum fungal strain may have potential applications in bioremediation of Cr(VI)-contaminated wastewaters.

The purpose of this study was to determine the degree of PAH contamination and the association of PAHs with metals in urban soil samples from Sevilla (Spain). Fifteen polycyclic aromatic hydrocarbons-PAHs (naphthalene, acenaphthene, fluorene, phenanthrene, anthracene, fluoranthene, pyrene, benzo[a]anthracene, chrysene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, dibenzo[a,h]anthracene, benzo[g,h,i]perylene, indeno[1,2,3-c,d]pyrene) and seven metals (Cd, Cr, Cu, Mn, Ni, Pb, Zn) have been evaluated in representative urban soil samples. Forty-one top soils (0-10 cm) under different land use (garden, roadside, riverbank and agricultural allotment) were selected. PAHs from soil samples were extracted by sonication using dichloromethane. The simultaneous quantification of 15 different PAH compounds were carried out by HPLC using multiple wavelength shift in the fluorescence detector. For qualitative analysis a photo diode-array detector was used. Metal (pseudo-total) analysis was carried out by digestion of the soils with aqua regia in microwave oven. The mean concentration of each PAH in urban soils of Sevilla showed a wide range, they are not considered highly contaminated. The results of the sum of 15 PAHs in Sevilla soils are in the range 89.5-4004.2 μg kg-¹, but there seems not to be a correlation between the concentration of PAHs and the land use. Of the 15 PAHs examined, phenanthrene, fluoranthene and pyrene were present at the highest concentrations, being the sum of these PAHs about 40% of the total content. Although metal content were not especially high in most soils, there are significant hints of moderate pollution in some particular spots. Such spots are mainly related with some gardens within the historic quarters of the city. The associations among metals and PAHs content in the soil samples was checked by principal components analysis (PCA). The largest values both for 'urban' metals (Pb, Cu and Zn) and for PAHs were mainly found in sites close to the historic quarters of the city in which a heavy traffic of motor vehicles is suffered from years.

This paper deals with field measurements and hydraulic, oxygen transport and geochemical speciation modeling undertaken to evaluate the performance of a sand-bentonite test cover overlying a 20% sloping waste rock platform. A pit run (gravelly sand) layer protected the sand-bentonite layer. The study site was the Whistle Mine near Capreol, Ontario, Canada. The purpose of the study was to evaluate a number of test covers and select a final cover for the decommissioning of 7 million tonnes of acid-generating waste rock at the site. The sand-bentonite test plot and a control plot consisting of waste rock without cover were monitored over 3 years for water content, suction, soil temperature, gaseous oxygen concentrations, and water percolation. Air temperature, rainfall, snow pack and potential evaporation were also monitored. Finite element modeling showed very good agreement between modeled and measured cumulative precipitation, daily potential evaporation and cumulative evaporation, and to a lesser extent, the cumulative water percolation through the test cover. Due to construction difficulties in the field, the back of the waste rock platform was not covered with the test cover. This resulted in oxygen ingress from the back side of the waste rock. Oxygen transport modeling showed that if the entire waste rock pile had been covered, the daily oxygen flux would have been reduced by 90% to only 0.003 g/m²/day. Such low oxygen flux would minimize sulphide oxidation and hence acid generation in the waste rock. Aqueous equilibrium speciation modeling suggested that the concentrations of sulphate [graphic removed] , iron (Fe), and aluminum (Al) in percolate water in contact with waste rock were controlled by secondary minerals such as gypsum, alunite, and ferrihydrite.

Inorganic nitrogen deposition and leaching in stream water were monitored from January, 2001 to December, 2004 in a subtropical evergreen mixed forest in central-south China. The seasonal concentration and flux of inorganic nitrogen in bulk precipitation and stream water, seasonal mean net retention of nitrogen and net flux of H⁺ transformed by nitrogen were estimated and quantified in Shaoshan forest. The research results show that the correlation coefficient of fluxes between bulk precipitation and stream water is significant, with a coefficient 0.916 at the 0.01 level. Mean fluxes of inorganic nitrogen input are 2.62 g m⁻² a⁻¹ and 0.516 g m⁻² a⁻¹ in form of bulk precipitation and dry deposition respectively, and output in stream water is around 0.22 g m⁻² a⁻¹, which indicates that most of nitrogen input is reserved in the forest. Net retention of nitrogen reaches 2.916 g m⁻² a⁻¹, just higher than other study plots over the world. Along with the translating of nitrogen ( [graphic removed] and [graphic removed] ), H⁺ is imported to the forest ecosystem at the same time. At our study plots, net flux of H⁺ transformed by nitrogen is about 73.57 mmol m⁻² a⁻¹. The positive value suggests that Shaoshan forest is still a finer buffering system to nitrogen deposition and it is far from nitrogen saturation in spite of the high nitrogen deposition.

The competing ligand exchange method was used to investigate the competitive binding of Ni(II) by Al(III) and Fe(III) in model aqueous solutions and freshwaters. Graphite furnace atomic absorption spectrometry and adsorptive cathodic stripping voltammetry were used to monitor the rate of uptake of the Ni by Chelex 100 chelating resin and dimethylglyoxime as the competing ligands, respectively. The results have revealed that Ni(II)-humate complexes were more labile in presence of the mixture of Al(III) and Fe(III), compared to the lability of the Ni(II)-humate complexes when only one of the two, Al(III) or Fe(III), was present. The environmental significance of this work is that in model solutions simulating freshwater containing humic substances and the target trace metal Ni(II) and cations, Al(III) and Fe(III), the competitive binding of Ni(II), Al(III) and Fe(III) by humic substances makes Ni(II)-humate complexes labile, releasing free Ni²⁺-aqua complex, which reported to be toxic.