To rigorously assess treatment technologies and establish regulatory framework for chromate-contaminated site remediation, it is useful to know the exact chromium speciation in soil matrices. In an earlier study, Thornton, E. C., & Amonette, J. E. (1999). Hydrogen sulfide gas treatment of Cr(VI)-contaminated sediment samples from a plating-waste disposal site - implications for in-situ remediation. Environmental Science & Technology, 33, 4096-4101, reported that some chromate in the bulk particles was not accessible to gaseous reductants or solution-phase extractants, based on XANES studies. We hypothesized that part of this non-extractable chromate may reside in the structure of minerals such as calcium carbonate. To test this hypothesis, a number of calcium carbonate precipitates were prepared in the presence of various concentrations of chromate during the precipitation, which could coprecipitate chromate, or by adding chromate after the precipitation was completed. Hydrochloric acid was used to dissolve calcium carbonate and therefore extract the coprecipitated and surface attached chromate. The results showed that the coprecipitated chromate was non-extractable by hot alkaline solution or phosphate buffer, but could be solubilized by HCl in proportional to the amount of calcium carbonate dissolved. The X-ray diffraction experiments revealed that the coprecipitation of chromate with calcium carbonate had an influence on its crystal structure: The higher the chromate concentration, the greater the ratio of vaterite to calcite.

Increasing environmental concentrations of platinum group metals (PGMs), in particular platinum (Pt), rhodium (Rh) and palladium (Pd), from catalytic converters has been reported worldwide. The impact of these three metals on the uptake and use of essential mineral nutrients was examined using two plant models: the submerged aquatic plant, Elodea canadensis, and the terrestrial emergent plant, Peltandra virginica. Plants were grown for 2 weeks in nutrient solutions with either Pt⁴⁺ at concentrations between 0.05 and 5 mg/L, or a 0.1 mg/L Pt⁴⁺, Rh³⁺, Pd²⁺ mixture. Some treatments received additional Ca²⁺, Zn²⁺, or humic acid (with varying pH) to study how these conditions affected PGM uptake. Metal concentration analyses were conducted using a graphite furnace atomic absorption spectrometer (GFAAS) or an inductively coupled plasma emission spectrometer (ICP). Growth response was assessed through total chlorophyll content. There was significant Pt accumulation in plant tissues, from 55 to 326 times the concentration in nutrient solution. At pH 8, the addition of humic acid doubled Pt accumulation in comparison to the control. Additional exogenous minerals did not significantly affect PGM uptake, nor did the uptake of PGMs interfere with the uptake of Ca, Fe or Cu. Synthesis of chlorophyll in new shoots was not affected by Pt accumulation; however, visible chlorosis was observed in older shoots at 5 ppm Pt. Roadside Daucus carota samples from four heavy traffic locations in Dutchess County (New York) were also assessed for PGM content. Pt, Pd and Rh concentrations averaged 14.6, 10.2, and 0.7 μg/g, respectively.

Sedimentprofiles of the last 4,000-14,000 years are presented from three dimictic lakes in Mecklenburg-Vorpommern (North-eastern Germany). Sedimentological composition, major trace elements and nutrients as well as parameter for core chronology (palynology, ¹⁴C-AMS) were investigated in order to reconstruct the historical development of the lakes during the Holocene. Palynological results reflect different human settlement phases and environmental changes from the late Pleistocene to the Subatlantic. Since the Middle Ages, a permanent settlement in the catchment area resulted in higher sedimentation rates in the three lakes. Variations in sediment composition like organic matter, carbonate and mineral content were caused by different land management techniques and natural changes in the catchment area. The phosphorus accumulation increased in the upper sediment layers, but the highest phosphorus accumulations were not found in the industrial phase, but in older sediments associated with human settlement activities in the catchment area. The heavy metals lead and zinc increase in the uppermost part of all three lakes reflecting the atmospheric anthropogenic input during the last 150-200 years.

On the coastal plains of Finland there are approximately 3,000 km² of acid sulfate soils developed as a result of intensive agricultural drainage of waterlogged sulfide-bearing sediments. The runoff from these soils contains very high amounts of acidity and metals that have severely deteriorated the aquaculture in several downstream rivers and estuaries. Therefore, there is an urgent need to develop and test more environmental friendly ways of draining landscapes underlain with these nasty soils. In this study, over a 3-year monitoring period the effect of excess surface liming, controlled drainage and lime filter drainage of acid sulfate soils on runoff water quality (pH, sulfate, metals) was determined and assessed. The results showed that (1) the liming measures had not prevented severely acidic and metal-rich waters from forming and discharging from the soils, (2) the controlled drainage system might have reduced discharge peaks but its potential effects on the discharged water quality were nondetectable due to its small effect on the groundwater level and naturally inherited heterogeneities, and (3) the spatial and temporal variations identified for the various hydrochemical determinants were not caused by the kind of treatment applied. Therefore, on acid sulfate soil fields, like the one studied here, the short-term hydrochemical effects of the treatments tested are minor (or nonexistent) at least as long as the controlled drainage systems are not technically improved or better maintained.

The hydrolysis of 4-Nitrophenylphosphate (NPP) in the presence of Ferrous and Ferric ions in Oil in water microemulsion media was investigated. The reaction was monitored by measuring the absorbance of the nitrophenolate ion produced in the reaction aliquots with time. The order of effectiveness of the microemulsion system towards the hydrolysis of NPP was found to be cationic > anionic> aqueous in the presence of Ferrous, Ferric and Turnbull's blue at neutral pH. The result of the present investigation enriches our understanding of the possible roles polymetallic ions play in hydrolysis reactions. The reactions mimic the roles of purple acid phosphatases in the hydrolysis of phosphate esters. The application of the above systems for environmental decontamination of organophosphates is also envisoned.

Concentration levels of 11 lower carbonyls were studied at Montelibretti, a semi-rural area near Rome, Italy, over July-September 2005 and February 2006. In both periods the most abundant carbonyls were acetone and formaldehyde, followed by methylglyoxal, acetaldehyde and hexanal. Monthly variation was apparent with maximum values observed in July, when levels at least a factor two higher compared to the successive months were observed. In summer all carbonyls except acetone were reasonably well correlated among themselves and with ozone. In addition very high formaldehyde/benzene concentration ratios were measured in the summer months compared to February. These findings indicated that photochemical reactions should be the major source of carbonyls in summer. Ranking of carbonyls respect to ozone production potential emphasized the predominance of formaldehyde and methylglyoxal, followed at a distance by glyoxal and acetaldehyde.

This study deals with Particle Matter (PM) levels in the metropolitan area of Lisbon and shows that EU directive is exceeded in a systematic way, mainly due to the inner city traffic. Results show that it is important to develop an epidemiological study in Lisbon to find a possible association between PM levels, sources and morbidity. Some important issues related with a monitor's representation of regional, sub-regional, and local air pollution exposures to the population in the metropolitan area are highlighted. PM₂.₅ and PM₁₀ total mass concentration measured in several places located in both centre of Lisbon and the outskirts are quite well correlated, mainly considering that two measuring methodologies (automatic and gravimetric) were used and areas with different classifications (urban and suburban) were analysed. However, the results imply that a source-oriented evaluation of PM health effects needs to take into account the uncertainty associated with spatial representativity of the species measured at a single sampling station. Temporal correlation across sampling stations, within relatively short separation distances, varied considerably for some important elements (Zn, Sb, Cu, As and Br), indicating that the precision of population exposure estimates for specific elements can vary depending on the species.

Fluvial bed sediments are widely used for characterizing anthropogenic contaminant signals in urban watersheds. This study presents the first preliminary examination of sequentially extracted Pb from grain size fractionated bed sediments using the optimized (standardized) BCR procedure. Baseline sediment samples and samples from the vicinity of three storm-sewer outlets in Nuuanu Stream, Honolulu, Hawaii, were examined. The weighted average Pb liberated from four sequentially extracted phases was 144 ± 26 mg/kg (±SD). These Pb concentrations are high compared to 3 mg/kg leached by a 0.5 M HCl solution, and 13 mg/kg from a 4-acid total digestion of baseline sediments. Over a 1.8 km section of stream channel, land use variations and traffic density differences had little impact on the magnitude of Pb in specific phases for each of the six grain size fractions examined. Regardless of grain size or spatial location, Pb in the reducible phase exceeded that in oxidizable, residual and acid extractable phases. Weighted reducible Pb concentrations for three sewer outlet sites ranged from 69 to 92 mg/kg, and this phase typically accounted for 70-80% of all labile Pb. The <63 μm grain size class did not exhibit the highest Pb concentration, instead this was found in either the 125-250 μm or 500-1,000 μm fractions. Examining bed sediment phase associations of Pb over a smaller length dimension (i.e., 40 m) centered around one sewer outlet, indicated higher concentrations at the outlet (180 mg/kg) compared to upstream (132 mg/kg) or downstream (150 mg/kg). The differences were primarily associated with higher Pb concentrations in the reducible and oxidizable phases of the coarse sand fractions (500-2,000 μm) at the outlet. Overall, all data point to a significant anthropogenic signal for Pb in bed sediments in the urbanized section of Nuuanu Stream.

The objective of this study was to check the effect of the use of a physico-chemical treatment on the clogging process of horizontal subsurface flow constructed wetlands by means of dynamic modelling. The hydraulic submodel was based on series as well as parallel branched complete stirred tanks of equal volume. The model was validated with data obtained from 2 identical experimental wetlands, which had a surface area of 0.54 m² and a water depth of 0.30 m, and that were monitored over a period of 5 months. One of the wetlands was fed with settled urban wastewater, whereas the other with the same wastewater, but previously treated with a physico-chemical treatment. In the model, pore volume reduction depends on the growth of bacteria and on solids retained. The effluent concentrations of COD and ammonium in both experimental wetlands were very similar in all the conditions tested, and therefore the physico-chemical treatment did not improve the removal efficiency. The model indicated that after 120 days of operation in some regions of the wetland fed with settled wastewater the porosity decreased in a 17%, whereas in the other wetlands it only decreased as much as 6%. The use of a prior physico-chemical treatment is a good alternative for avoiding an anticipated clogging of subsurface flow constructed wetlands.

The determination of stomatal ozone fluxes is essential to assess the potential damage to plants due to ozone uptake. This parameter is not accessible directly with measurements, but can be deduced through algorithms using observational data. Total ozone fluxes and water vapour fluxes are generally used. Water vapour fluxes give an indication on stomatal aperture, which is the controlling factor of ozone uptake by vegetation. In this work, a series of observations made during the growing season over an onion field are used to show the equivalence of two algorithms found in the literature to derive ozone stomatal fluxes and both based on the similarity between ozone stomatal fluxes and water vapour stomatal fluxes. One of these algorithms uses the Penman-Monteith approach, where the water vapour pressure deficit is calculated using air temperatures; the second calculates, with another formulation, the water vapour deficit from the leaf temperature. The two approaches lead to the same results if applied properly, as shown in this work, both theoretically and numerically.