The delafossite CuCrO₂ is a promising candidate for the visible light driven catalysis. The NO₂ ⁻ removal by photoelectrochemical process is studied under mild conditions, close to that encountered in the natural environment. CuCrO₂ exhibits a long term chemical stability with a corrosion rate of 0.34 μmol m⁻² year⁻¹ in KCl (0.5 M). A forbidden band of 1.3 eV has been evaluated from the diffuse reflectance spectrum. The flat band potential (-0.07 V SCE) determined from the Mott-Schottky plot is close to the photocurrent onset potential (0 V SCE). Hence, the conduction band is positioned at -1.08 V SCE and thus lies below the NO₂ ⁻ level leading to a feasible reduction upon visible illumination. The conversion occurs in less than ~5 h with a quantum efficiency of ~0.5%. The possibility of identifying the reaction products via the intensity-potential characteristics was explored by using standard solutions. The decrease of the conversion rate over time is attributed to the competitive water reduction. In absence of catalyst, NO₂ ⁻ is oxidized to NO₃ ⁻ in air equilibrated solution and the reaction follows a first order kinetic with a half life of 21 h, NO₃ ⁻ has been identified by iodometry through copper titration.

As part of the Rain In Cumulus over the Ocean Experiment (RICO) and the Puerto Rico Aerosol and Cloud Study (PRACS), cloud water was collected at East Peak (EP) in Puerto Rico. The main objective of this study was to determine the concentrations of water-soluble species (Cl⁻, NO₃ ⁻, SO₄ ²⁻, NH₄ ⁺, Ca²⁺, H⁺, Mg²⁺, K⁺, and Na⁺) in water samples taken from clouds influenced by tropical trade winds. The most abundant inorganic species were Na⁺ (average 465 μeq l⁻¹) and Cl⁻ (434 μeq l⁻¹), followed by Mg²⁺ (105 μeq l⁻¹), SO₄ ²⁻ (61 μeq l⁻¹), and NO₃ ⁻ (25 μeq l⁻¹). High concentrations of nss-SO₄ ² (28 μeq l⁻¹), NO₃ ⁻ (86 μeq l⁻¹), and H⁺ (14.5 μeq l⁻¹) were measured with a shift in air masses origin from the North Atlantic to North American continent, which reflected a strong anthropogenic influence on cloud chemistry at EP. Long-range transport of particles and acid gases seems to be the factor responsible for fluctuations in concentrations and pH of cloud water at East Peak. When under trade wind influences the liquid phase concentrations of all inorganic substances were similar to those found in clouds in other clean maritime environments.

Risk assessment of trace-metal contamination in soils requires predictive models that take into account the interaction of metal ions with other cations (e.g., H⁺ and Ca²⁺) that can change the speciation of trace metals in solution and compete for binding sites on plant roots thus affecting metal uptake and toxicity. Acid-base titrations were used to estimate the types and quantity of cation-binding sites on fresh pea (Pisum sativum L. cv. Lincoln) roots and their binding strength with protons. The roots were found to have three types of cation-binding sites with site densities of 190, 382, and 347 μmolc g⁻¹ (dry weight), respectively. The binding strength with H⁺ was indicated by the equilibrium formation constants (K HLj ). The logK HLj values under different ionic strengths were determined. At zero ionic strength, the logK HLj values are estimated to be 2.5, 5.5, and 8.3, respectively. Complementary experiments were used to validate the titration results. These included an ion exchange experiment, an experiment with HCl extractions, and a KOH neutralization method. Estimates from all four methods were consistent under the experimental conditions. The quantification of the binding capacity and the characteristics of these binding sites will assist in the development of more appropriate solution speciation models that incorporate biotic ligands. The derived parameters will provide the basis on which further development of a biotic ligand model is dependent.

Background, aim, and scope Dissolved organic matter, measured as dissolved organic carbon (DOC), is an important component of aquatic ecosystems and of the global carbon cycle. It is known that changes in DOC quality and quantity are likely to have ecological repercussions. This review has four goals: (1) to discuss potential mechanisms responsible for recent changes in aquatic DOC concentrations; (2) to provide a comprehensive overview of the interactions between DOC, nutrients, and trace metals in mainly boreal environments; (3) to explore the impact of climate change on DOC and the subsequent effects on nutrients and trace metals; and (4) to explore the potential impact of DOC cycling on climate change. Main features We review recent research on the mechanisms responsible for recent changes in aquatic DOC concentrations, DOC interactions with trace metals, N, and P, and on the possible impacts of climate change on DOC in mainly boreal lakes. We then speculate on how climate change may affect DOC export and in-lake processing and how these changes might alter nutrient and metal export and processing. Furthermore, the potential impacts of changing DOC cycling patterns on climate change are examined. Results It has been noted that DOC concentrations in lake and stream waters have increased during the last 30 years across much of Europe and North America. The potential reasons for this increase include increasing atmospheric CO₂ concentration, climate warming, continued N deposition, decreased sulfate deposition, and hydrological changes due to increased precipitation, droughts, and land use changes. Any change in DOC concentrations and properties in lakes and streams will also impact the acid-base chemistry of these waters and, presumably, the biological, chemical, and photochemical reactions taking place. For example, the interaction of trace metals with DOC may be significantly altered by climate change as organically complexed metals such as Cu, Fe, and Al are released during photo-oxidation of DOC. The production and loss of DOC as CO₂ from boreal lakes may also be affected by changing climate. Climate change is unlikely to be uniform spatially with some regions becoming wetter while others become drier. As a result, rates of change in DOC export and concentrations will vary regionally and the changes may be non-linear. Discussion Climate change models predict that higher temperatures are likely to occur over most of the boreal forests in North America, Europe, and Asia over the next century. Climate change is also expected to affect the severity and frequency of storm and drought events. Two general climate scenarios emerge with which to examine possible DOC trends: warmer and wetter or warmer and drier. Increasing temperature and hydrological changes (specifically, runoff) are likely to lead to changes in the quality and quantity of DOC export from terrestrial sources to rivers and lakes as well as changes in DOC processing rates in lakes. This will alter the quality and concentrations of DOC and its constituents as well as its interactions with trace metals and the availability of nutrients. In addition, export rates of nutrients and metals will also change in response to changing runoff. Processing of DOC within lakes may impact climate depending on the extent to which DOC is mineralized to dissolved inorganic carbon (DIC) and evaded to the atmosphere or settles as particulate organic carbon (POC) to bottom sediments and thereby remaining in the lake. The partitioning of DOC between sediments and the atmosphere is a function of pH. Decreased DOC concentrations may also limit the burial of sulfate, as FeS, in lake sediments, thereby contributing acidity to the water by increasing the formation of H₂S. Under a warmer and drier scenario, if lake water levels fall, previously stored organic sediments may be exposed to greater aeration which would lead to greater CO₂ evasion to the atmosphere. The interaction of trace metals with DOC may be significantly altered by climate change. Iron enhances the formation of POC during irradiation of lake water with UV light and therefore may be an important pathway for transfer of allochthonous DOC to the sediments. Therefore, changing Fe/DOC ratios could affect POC formation rates. If climate change results in altered DOC chemistry (e.g., fewer and/or weaker binding sites) more trace metals could be present in their toxic and bioavailable forms. The availability of nutrients may be significantly altered by climate change. Decreased DOC concentrations in lakes may result in increased Fe colloid formation and co-incident loss of adsorbable P from the water column. Conclusions Climate change expressed as changes in runoff and temperature will likely result in changes in aquatic DOC quality and concentration with concomitant effects on trace metals and nutrients. Changes in the quality and concentration of DOC have implications for acid-base chemistry and for the speciation and bioavailability of certain trace metals and nutrients. Moreover, changes in DOC, metals, and nutrients are likely to drive changes in rates of C evasion and storage in lake sediments. Recommendations and perspectives The key controls on allochthonous DOC quality, quantity, and catchment export in response to climate change are still not fully understood. More detailed knowledge of these processes is required so that changes in DOC and its interactions with nutrients and trace metals can be better predicted based on changes caused by changing climate. More studies are needed concerning the effects of trace metals on DOC, the effects of changing DOC quality and quantity on trace metals and nutrients, and how runoff and temperature-related changes in DOC export affect metal and nutrient export to rivers and lakes.

Background, aim, and scope Heavy metals such as lead are well known to cause harmful health effects. Especially children are particularly susceptible to increased levels of lead in their blood. It is also a fact that lead concentration is increasing in the environment due to increased anthropogenic activity. The risk of heavy metal contamination is pronounced in the environment adjacent to large industrial complexes. In a combined case study, the environmental pollution by heavy metals was related to children's health in the vicinity of an industrial area located 4 km south-east from Bucharest about 2 km east from the nearest town--Pantelimon. This site includes companies processing different, nonferrous solid wastes for recovery of heavy metals and producing different nonferrous alloys and lead batteries. In this paper, mainly the results of environmental sampling and analyses are summarized. Materials and methods Water, soil, and atmospheric deposition samples were collected from different locations within 3 km from the industrial area. For comparison, samples were also taken from Bucharest. Water samples were filtered (<0.45 μm), extracted by salpetric acid, and quantified by ICP-OES and ICP-MS. Soil samples were dried, sieved (<2 mm), extracted by aqua regia and analyzed by AAS. In order to quantify the atmospheric deposition, three kinds of permanently open collecting pots were used on nine different sites between August and November 2006. Results At most sampling locations, the heavy metal concentrations in soil decrease with increasing distance to the presumably major source of pollution. Highest heavy metal concentrations were found in 10-20 cm soil depths. There were also decreasing heavy metal concentrations for atmospheric deposition with increasing distance to the industrial site. In surface and groundwater samples, traces of zinc, copper and lead were detected. Discussion The heavy metal concentrations in soil were increased in the study area, mostly under legal action limits in low-concern areas (e.g., 1,000 mg Pb/kg dry soil), but often above action limits for high-concern areas (100 mg Pb/kg dry soil) such as populated areas. The soluble lead concentrations in water samples indicate a need for monitoring and assessing water quality in more detail. The results for atmospheric deposition showed increased dust precipitation and heavy metal loads in the study area compared to Bucharest. However, based on mass flow balance calculations, the actual atmospheric deposition of heavy metals must be much lower than it was in the past decades. Conclusions It was shown that highest lead values in water, soil and atmospheric deposition are rather to be found near the investigated industrial site than at the control sites in Bucharest. Our results correspond very well with results that show that children from Pantelimon have significantly increased lead concentrations in their blood compared to children in Bucharest. The increased lead contamination around the investigated industrial area is likely to have caused the increased exposure for children living in Pantelimon. Recommendations and perspectives In high-concern areas, such as found in populated areas, further measures have to be taken to avoid health risks for people living in these areas. The measures already taken to reduce emissions from the industrial site will help to avoid further increases in heavy metal concentrations. In areas with exceeded action limits, measures have to be taken as required by law. Detailed risk assessments could help to take necessary actions to protect public health in this area. The public should be informed about the potential hazards of eating plants grown in that area. Educational programs for schools, informing children about the contamination, should lead to a better understanding of environmental problems and a more sustainable behavior in the future.

Background, aims, and scope Since toxaphene (polychlorocamphene, polychloropinene, or strobane) mixtures were applied for massive insecticide use in the 1960s to replace the use of DDT, some of their congeners have been found at high latitudes far away from the usage areas. Especially polychlorinated bornanes have demonstrated dominating congeners transported by air up to the Arctic areas. Environmental fate modeling has been applied to monitor this phenomenon using parallel zones of atmosphere around the globe as interconnected environments. These zones, shown in many meteorological maps, however, may not be the best way to configure atmospheric transport in air trajectories. The latter could also be covered by connecting a chain of simple model boxes. We aim to study this alternative approach by modeling the trajectory chain using catchment boxes of our FATEMOD model. Polychlorobornanes analyzed in biota of the Barents Sea offered one case to study this modeling alternative, while toxaphene has been and partly still is used massively at southern East Europe and around rivers flowing to the Aral Sea. Materials and methods Pure model substances of three polychlorobornanes (toxaphene congeners P26, P50, and P62) were synthesized, their environmentally important thermal properties measured by differential scanning calorimetry, as evaluated from literature data, and their temperature dependences estimated by the QSPR programs VPLEST, WATSOLU, and TDLKOW. The evaluated property parameters were used to model their atmospheric long-range transport from toxaphene heavy usage areas in Ukraine and Aral/SyrDarja/AmuDarja region areas, through East Europe and Northern Norway (Finnmarken) to the Barents Sea. The time period used for the emission model was June 1997. Usual weather conditions in June were applied in the model, which was constructed by chaining FATEMOD model boxes of the catchment's areas along assumed maximal air flow trajectories. Analysis of the three chlorobornanes in toxaphene mixtures function as a basis for the estimates of emission levels caused by its usage. High estimate (A) was taken from contents in a Western product chlorocamphene and low estimate (B) from mean contents in Russian polychloroterpene products to achieve modeled water concentrations. Bioaccumulation to analyzed lipid of aquatic biota at the target region was estimated by using statistical calculation for persistent organic pollutants in literature. Results The results from model runs A and B (high and low emission estimate) for levels in sea biota were compared to analysis results of samples taken in August 1997 at Barents Sea. The model results (ng g⁻¹ lw): 4-95 in lipid of planktovores and 7-150 in lipid of piscivores, were in fair agreement with the analysis results from August 1997: 21-31 in Themisto libellula (chatka), 26-42 in Boreocadus saida (Polar cod), and 5-27 in Gadus morhua (cod) liver. Discussion The modeling results indicate that the application of chained simple multimedia catchment boxes on predicted trajectory is a useful method for estimation of volatile airborne persistent chemical exposures to biota in remote areas. For hazard assessment of these pollutants, their properties, especially temperature dependences, must be estimated by a reasonable accuracy. That can be achieved by using measurements in laboratory with pure model compounds and estimation of properties by thermodynamic QSPR methods. The property parameters can be validated by comparing their values at an environmental temperature range with measured or QSPR-estimated values derived by independent methods. The chained box method used for long-range air transport modeling can be more suitable than global parallel zones modeling used earlier, provided that the main airflow trajectories and properties of transported pollutants are predictable enough. Conclusions Long-range air transport modeling of persistent, especially photo-resistant organic compounds using a chain of joint simple boxes of catchment's environments is a feasible method to predict concentrations of pollutants at the target area. This is justified from model results compared with analytical measurements in Barents Sea biota in August 1997: three of six modeled values were high and the other three low compared to the analysis results. The order of magnitude level was similar in both modeled (planktovore and piscivore) and observed (chatka and polar cod) values of lipid samples. The obtained results were too limited to firm validation but are sufficient to justify feasibility of the method, which prompts one to perform more studies on this modeling system. Recommendations and perspectives For assessment of the risk of environmental damages, chemical fate determination is an essential tool for chemical control, e.g., for EU following the REACH rules. The present conclusion of applicability of the chained single-box multimedia modeling can be validated by further studies using analyses of emissions and target biota in various other cases. To achieve useful results, fate models built with databases having automatic steps for most calculations and outputs accessible to all chemical control professionals are essential. Our FATEMOD program catchments at environments and compound properties listed in the database represent a feasible tool for local, regional, and, according our present test results, for global exposure predictions. As an extended use of model, emission estimates can be achieved by reversed modeling from analysis results of samples corresponding to the target area.