Two lab-scale trickle-bed air biofilters were operated for investigating the difference in performance between a hydrophilic and a hydrophobic volatile organic compound (VOC). Methyl isobutyl ketone (MIBK) and styrene were selected as a model hydrophilic and hydrophobic VOCs, respectively. Effects of loading rates, biofilter re-acclimation, removal profile along biofilter depth, nitrogen consumption, and CO₂ production were compared under three operating conditions, namely, backwashing and two non-use periods (starvation and stagnant). Consistent over 99% removal efficiency up to loading rates of 3.26 kg COD/m³-day was obtained for the MIBK biofilter at 0.76 min empty bed retention time (EBRT) and 1.5 L/d nutrient flow. A similar performance for the styrene biofilter was obtained for loading rates up to 1.9kg COD/m³-day at 2.02 min EBRT and 2.4 L/d nutrient flow. The MIBK biofilter required only an initial acclimation period of 16 days while styrene biofilter required 46 days. Non-use periods can be used as another means of biomass control for both biofilters when the employed loading rate did not exceed 1.27 and 2.17 kg COD/m³-day for styrene and MIBK biofilters, respectively. The re-acclimation of both biofilter was delayed with increase of loading rate. MIBK biofilter re-acclimated in 90 min, while styrene biofilter re-acclimated in more than 600 min. Under similar loading rates, MIBK biofilter utilized less biofilter depth than styrene biofilter. Nitrogen consumption behaviors were apparently different between the two biofilters. Styrene biofilter had higher CO₂ production than MIBK biofilter and its CO₂ production was closely related to the theoretical complete chemical oxidation.

One of the methods to diminish the internal phosphorus (P) loading is inactivation of P by aluminum (Al). After addition of Al to lake water an Al(OH)₃ floc is formed, which settles to the bottom and initially form a lid on the sediment surface. The effects of Chironomus plumosus larvae on sediment nutrient fluxes and P binding-sites in the sediment after addition of Al were tested. C. plumosus larvae were added to sediment cores in which sediment-water fluxes of nutrients were measured four times. After one month, the sediment was sectioned with depth and P fractions were measured by sequential chemical extraction. The chironomids created burrows through the Al layer which caused a significantly increased efflux of P from the Al treated sediment, because the P had only limited contact to the added Al. The chironomids also affected the P fractions in the sediment by their bioturbating activity. Thus, they caused increased Al concentrations in the upper part of the Al treated sediment. This created an enhanced contact between Al and P in the upper 7 cm of the sediment and, as a result, an increased binding of P to Al and a lowered porewater P. The DIP efflux is therefore expected to be lowered after the initial phase. Al had no effects on the nitrogen fluxes, but the chironomids enhanced the [graphic removed] release, and decreased the [graphic removed] release or increased the [graphic removed] uptake by the sediments.

Sediment cores collected in eutrophic subalpine Lake Bled (NW Slovenia) were analyzed sedimentologically in terms of grain size, mineralogy and sedimentation rates, and geochemically in terms of metals and nutrients. Surficial sediment is composed of dark gyttya type clayey silt with 5%-10% of organic matter. The sediment below is fine laminated and composed of homogenous silt and clayey silt: Mineralogically, low-Mg calcite prevails, followed by dolomite, quartz, partially of diatomaceous origin, and feldspar. Clay minerals are composed of muscovite/illite and chlorite. Authigenic minerals are pyrite and 'lake chalk' (low-Mg calcite). Lake sediment is especially polluted by Pb, Zn and P. Higher contents were found in the northwestern and eastern parts due to the particle input by local inflows. Increasing eutrophication and pollution, indicated by Cd, Cu, V, Cr, Co and total N and P enrichment in the top layers of the cores, started almost 100 years B.P., and especially 50 years ago.

A benthic in situ flume and a 1D biogeochemical sediment model to evaluate solute fluxes across the sediment-water interface have been developed. The flume was successfully used to determine oxygen and nutrient fluxes at various locations of the Neckar River in Germany. The experimental results were linked with vertical pore water concentration profiles and independently verified with the model. By combining experimental and model results we assessed the influence of dissolved oxygen concentrations in the water column and the availability of degradable organic matter on sediment oxygen demand. The results and the derived relations can be used to parameterize the sediment module of large scale water quality models, allowing one to assess the influence of sediment-water interactions on various aspects of river water quality. Moreover, the biogeochemical sediment model can help to improve the general understanding of the processes governing solute concentrations and fluxes in sediments and across their interfaces.

Hydrochemistry of an alluvial river was investigated employing the chemometric techniques such as cluster analysis (CA), principal component analysis (PCA), discriminant analysis (DA) and partial least square (PLS) with a view to extract information about the variables responsible for spatial and temporal variations in river hydrochemistry and water quality, the hidden factors explaining the structure of the hydro-chemical database of the river, factors/processes influencing the river hydro-chemistry. Analysis of spearman's correlation coefficient revealed non-significant correlation of the pollution indicator (BOD, COD, SO₄, F, NH₄-N, NO₃-N) variables with season and significant correlation with site, indicating contribution of the site-specific anthropogenic sources in the catchments. Spatial CA clustered the monitoring sites (10nos.) into three groups of relatively non-polluted sites, moderately polluted sites, and highly polluted sites. Temporal CA differentiated among the samples of monsoon and non-monsoon months. PCA rendered considerable data reduction, in terms of eight parameters explaining about 71% of the total variance and evolved six PCs. PCA grouped samples belonging to different seasons and sites distinctly correlating them with natural and anthropogenic variables. Temporal and spatial DA rendered 97 and 92% correct assignations of the samples, respectively, and revealed that temperature, pH, BOD, DO, alkalinity and Ca are the most significant variables to discriminate between the different seasons and account for most of the expected temporal variations in hydrochemistry of the river, whereas, hardness, DO, BOD, COD, Ca and Mg were the most significant discriminating variables in space. Spatial and temporal groupings of the samples were successfully achieved through PLS modeling. PLS showed that the summer season samples are dominated by PO₄, TDS, F, K, COD, BOD, Na, Cl, hardness and alkalinity, whereas, samples of winter season by DO, pH, NH₄-N and coliforms. Furthermore, PLS indicated site-specific dominance of anthropogenic contaminants suggesting for their pollution sources in the corresponding catchments of these sites.

Steady-state models for the prediction of P retention coefficient (R) in lakes were evaluated using data from 93 natural lakes and 119 reservoirs situated in the temperate zone. Most of the already existing models predicted R relatively successfully in lakes while it was seriously under-estimated in reservoirs. A statistical analysis indicated the main causes of differences in R between lakes and reservoirs: (a) distinct relationships between P sedimentation coefficient, depth, and water residence time; (b) existence of significant inflow-outflow P concentration gradients in reservoirs. Two new models of different complexity were developed for estimating R in reservoirs: [graphic removed] , where τ is water residence time (year), was derived from the Vollenweider/Larsen and Mercier model by adding a calibrated parameter accounting for spatial P non-homogeneity in the water body, and is applicable for reservoirs but not lakes, and [graphic removed] , where [Pin] is volume-weighted P concentration in all inputs to the water body (μg l-¹), was obtained by re-calibrating the OECD general equation, and is generally applicable for both lakes and reservoirs. These optimised models yield unbiased estimates over a large range of reservoir types.

In multiphase systems capillary pressures play a significant role on fluid movement and retention. The facility to predict the effect of different thermal remediation strategies requires the knowledge of the effect of temperature on capillary pressure-saturation relationships in the soils. The objective of recent study was (a) to develop a technique for routinely measuring the pressure-saturation curves of soil samples saturated with a nonpolar liquid at different regulated temperatures (b) to build a database using the measured pressure-saturation curves and the physical, chemical properties of the model soils (c) to establish the dependence of nonaqueous phase liquid retention on the soil properties and the temperature. The retention curves (extraction isotherms) with nonaqueous phase liquid were determined using a modified pressure plate extractor. The wetting phase was a non-aromatic hydrocarbon distillation product. Pressure plates were designed and constructed in the laboratory of our department. The temperature was held constant at 20, 40 and 60 [composite function (small circle)]C. Statistical analysis was performed involving selected soil parameters and the measured nonaqueous phase liquid retention data. The results show that knowing some easily measurable soil parameters (bulk density, particle size distribution, humus and lime content) we can estimate the nonaqueous phase liquid retention of the soils. The measured “extraction isotherms” provide essential information about the temperature-dependency of pressure-saturation curves.

This study has been conducted at the University of Connecticut (UCONN) in connection with the USEPA Superfund Innovative Technology Evaluation (SITE) program to evaluate a chemical oxidation technology (sodium persulfate) developed at UCONN. A protocol to assess the efficacy of oxidation technologies has been used. This protocol, which consists of obtaining data from a treatability study, tested two in-situ chemical oxidation technologies that can be used on soil and groundwater at a site in Vernon, Connecticut. Based on the treatability report results and additional field data collected at the site, the design for the field implementation of the chemical oxidation remediation was completed. The results indicate that both sodium persulfate and potassium permanganate were able to effectively degrade the target VOCs (i.e., PCE, TCE and cis-DCE) in groundwater and soil-groundwater matrices. In the sodium persulfate tests (120 hrs), the extent of destruction of target VOCs was 74% for PCE, 86% for TCE and 84% for cis-DCE by Na₂S₂O₈ alone and 68% for PCE, 76% for TCE, and 69% for cis-DCE by Fe(II)-catalyzed Na₂S₂O₈. The results demonstrate the sodium persulfate's ability to degrade PCE, TCE and cis-DCE. It is expected that given sufficient dose and treatment time, a higher destruction rate of the dissolved phase contamination can be achieved. The data also indicates that the catalytic effect of the iron chelate on persulfate chemistry was much less pronounced in the soil-groundwater matrix. This indicates an interaction between the iron chelate solution and the soil, which may have resulted in a lower availability of the chelated iron for catalysis. The study showed that the remediation of the VOCs-contaminated soil and groundwater by in-situ chemical oxidation using sodium persulfate is feasible at the Roosevelt Mills site. As a result, the USEPA SITE program will evaluate this technology at this site.

The process of eutrophication in form of intense plant growth has been observed in some lakes and water streams at the Plitvice Lakes National Park in central Croatia. Here we investigate whether this phenomenon is a consequence of anthropogenic pollution or due to naturally produced organic matter in the lakes. We applied chemical analysis of water at two springs and four lakes (nutrients, dissolved organic carbon (DOC), trace elements) and measurements of surface lake sediments (mineral and organic fraction analyses, trace elements) in four different lakes/five sites. The chemical composition of water does not indicate recent anthropogenic pollution of water because the concentrations of most trace elements are below detection limits. The concentrations of DOC and nutrients are slightly higher in the area of increased eutrophication-plant growth. Also the content of organic matter in the sediment is at the highest level in areas with highest C/N ratio indicating that the organic fraction of this sediment is mainly of terrestrial origin. There is no significant difference among the trace element concentration in the upper segment of all cores, deposited approximately during last 50 years when higher anthropogenic influence is expected due to development and touristic activity, and the lower part of the cores, corresponding to the period approximately 100-200 years before present. The content of trace elements and organic matter in sediments decreases from the uppermost lake downstream. According to our results there is no indication of recent anthropogenic pollution in water and sediment. Higher concentrations of DOC in water as well as phosphorus and some other elements in the lake sediment can be a consequence of input of natural organic matter to the lake water.

¹⁵N-labeling and solid-state ¹³C and ¹⁵N nuclear magnetic resonance (NMR) spectroscopy was applied to study the immobilization of 2,4,6 trinitrotoluene (TNT) into soil organic matter (SOM). Uncontaminated soil from the Ap horizon of a Luvisol was mixed with ¹⁵N-TNT (enrichment: 99 atm%) and laid over an unspiked layer of the same material. The latter covered soil from the Bt horizon. The microcosms were aerobically incubated under laboratory conditions for up to 11 months. After 1 week, within the total microcosm approximately 90% of the added ¹⁵N (¹⁵Nadd) were recovered, mostly in the top layer (87%). After 11 months, this amount decreased to 71%, indicating losses due to denitration or transamination. Within two months, half of ¹⁵Nadd had been immobilized in the residues not extractable with organic solvents and water. The amount of the sequestered ¹⁵Nadd remained fairly constant until the end of the experiment pointing towards a high stability of TNT-SOM associates. Solid-state ¹⁵N NMR revealed their formation by covalent binding, most tentatively as amides. Complete reduction of TNT to triaminotoluene (TAT) was not prerequisite. The most pronounced downwards movement of ¹⁵N-TNT occurred during the first two months. The major part of it, however, experienced quick immobilization, leaving approximately 10% of ¹⁵Nadd recovered in the leachate at the end of the experiment. Calculations indicated contributions of inorganic ¹⁵Nadd. Approximately 25% of its organic ¹⁵Nadd originated from condensed N, suggesting that in soils the transport of partly reduced TNT is in close association with the organic matter of the soil solution to which they are covalently bound.