Formation of a ternary neptunyl(V) biscarbonato inner-sphere sorption complex inhibits calcite growth rate

Neptunyl, Np(V)O(2)(+), along with the other actinyl ions U(VI)O(2)(2+) and Pu(V,VI)O(2)((+,2+)), is considered to be highly mobile in the geosphere, while interaction with mineral surfaces (inner- or outer-sphere adsorption, ion-exchange, and coprecipitation/structural incorporation) may retard its migration. Detailed information about the exact interaction mechanisms including the structure and stoichiometry of the adsorption complexes is crucial to predict the retention behavior in diverse geochemical environments. Here, we investigated the structure of the neptunyl adsorption complex at the calcite-water interface at pH 8.3 in equilibrium with air by means of low-temperature (15K) EXAFS spectroscopy at the Np-L(III) edge. The coordination environment of neptunyl consists of two axial oxygen atoms at 1.87(±0.01)?, and an equatorial oxygen shell of six atoms at 2.51(±0.01)?. Two oxygen backscatterers at 3.50(±0.04)? along with calcium backscatterers at 3.95(±0.03)? suggest that neptunyl is linked to the calcite surface through two monodentate bonds towards carbonate groups of the calcite surface. Two additional carbon backscatterers at 2.94(±0.02)? are attributed to two carbonate ions in bidentate coordination. This structural environment is conclusively interpreted as a ternary surface complex, where a neptunyl biscarbonato complex sorbs through two monodentate carbonate bonds to steps at the calcite (104) face, while the two bidentately coordinated carbonate groups point away from the surface. This structural information is further supported by Mixed Flow Reactor (MFR) experiments. They show a significant decrease of the calcite growth rate in the presence of neptunyl(V), in line with blockage of the most active crystal growth sites, step and kink sites, by adsorption of neptunyl. Formation of this sorption complex constitutes an important retention mechanism for neptunyl in calcite-rich environments.     

Simultaneous analysis of free and sulfo-conjugated steroid estrogens in artificial urine solution and agricultural soils by high-performance liquid chromatography

A simple and robust analytical method was developed to simultaneously detect and quantify 17β-estradiol (E2), estrone (E1), 17β-estradiol-3-sulphate (E2-3S), and estrone-3-sulphate (E1-3S) in aqueous solutions (calcium chloride and artificial urine solutions) and agricultural soils using high performance liquid chromatography and UV detection. The standards for all four compounds were linear in the range of 0.01 to 1.0 μg mL(-1) (n = 6) and 1.0 to 20 μg mL(-1) (n = 6), respectively, with correlation coefficients > 0.999. The on-column limits of detection at an injection volume of 50 μL and S/N (signal: noise) ratio of 3 were: 9.0 ng mL(-1), 10 ng mL(-1), 5.0 ng mL(-1), and 7.0 ng mL(-1) for E2-3S, E1-3S, E2 and E1, respectively. The limit of detection and quantification in artificial urine solution and CaCl(2) solution was 1.0 ng mL(-1) for all four compounds. Method detection limits for the compounds in the 3 soils ranged from 2 to 2.4 ng g(-1) (E2-3S and E1-3S), and 1.0 to 2.9 ng g(-1) (E2 and E1), respectively.     

The global impact of ozone on agricultural crop yields under current and future air quality legislation

In this paper we evaluate the global impact of surface ozone on four types of agricultural crop. The study is based on modelled global hourly ozone fields for the year 2000 and 2030, using the global 1°×1° 2-way nested atmospheric chemical transport model (TM5). Projections for the year 2030 are based on the relatively optimistic “current legislation (CLE) scenario”, i.e. assuming that currently approved air quality legislation will be fully implemented by the year 2030, without a further development of new abatement policies. For both runs, the relative yield loss due to ozone damage is evaluated based on two different indices (accumulated concentration above a 40 ppbV threshold and seasonal mean daytime ozone concentration respectively) on a global, regional and national scale. The cumulative metric appears to be far less robust than the seasonal mean, while the seasonal mean shows satisfactory agreement with measurements in Europe, the US, China and Southern India and South-East Asia.Present day global relative yield losses are estimated to range between 7% and 12% for wheat, between 6% and 16% for soybean, between 3% and 4% for rice, and between 3% and 5% for maize (range resulting from different metrics used). Taking into account possible biases in our assessment, introduced through the global application of “western” crop exposure–response functions, and through model performance in reproducing ozone-exposure metrics, our estimates may be considered as being conservative.Under the 2030 CLE scenario, the global situation is expected to deteriorate mainly for wheat (additional 2–6% loss globally) and rice (additional 1–2% loss globally). India, for which no mitigation measures have been assumed by 2030, accounts for 50% of these global increase in crop yield loss. On a regional-scale, significant reductions in crop losses by CLE-2030 are only predicted in Europe (soybean) and China (wheat).Translating these assumed yield losses into total global economic damage for the four crops considered, using world market prices for the year 2000, we estimate an economic loss in the range $14–$26 billion. About 40% of this damage is occurring in China and India. Considering the recent upward trends in food prices, the ozone-induced damage to crops is expected to offset a significant portion of the GDP growth rate, especially in countries with an economy based on agricultural production.     

Polybrominated diphenyl ether (PBDE) levels in dust from previously owned automobiles at United States dealerships

The levels of BDE-28, BDE-47, BDE-99, BDE-100, BDE-153, BDE-154, BDE-183, and BDE-209 were determined in the dust sampled from 60 automobiles that were available for resale at U.S. dealerships. The dominant congener in automobile dust was BDE-209 comprising 95% of the total PBDE levels with a median level of 48.1 µg g^? 1. Statistical analysis of the vehicle attributes indicates that the BDE-209 levels are different (p < 0.05) with respect to groupings by vehicle model year, vehicle manufacturer, and the country of manufacture. Vehicle dust samples contained the characteristic profile of the PBDE congeners that comprise the PentaBDE formulation. While DecaBDE use is banned in Maine and Washington and is targeted for restriction in the near future by six U.S. states, vehicles and airplanes are exempt from the ban. It is anticipated that the human exposure potential to PBDEs from automobile dust ingestion will continue for an indefinite future period in the U.S. population.     

Education and advice contribute to increased density of broadleaved conservation trees, but not saplings, in young forest in Sweden

The effectiveness of different conservation policies is debated, but the policies are rarely evaluated quantitatively. A voluntary or 'soft' policy based mainly on education provides information about ecosystems and effects of land use, to encourage conservation action. Swedish forestry relies mainly on soft policy, with substantial resources for education and advice to more than 200,000 forest owners, while legal regulation is weak. Increased retention of broadleaved trees at clear-cutting, with environmental benefits in the conifer-dominated forestry, is important in the policy. We used the Swedish National Forest Inventory to analyse this policy for young forests in southern Sweden. Between 1983-1987 and 1998-2002 the policy had no positive effect on saplings (1.3m tall to 4.9 cm dbh) of birch, oak, beech and other species that mostly decreased in density, due to planting of conifers and browsing by ungulates. However, broadleaved conservation trees (>or=15 cm dbh) increased in density, e.g. to about one oak and six birches per ha in young coniferous forest in 1998-2002. The relative increase in density was higher for large (>or=20 cm dbh) than for small trees (15-20 cm dbh). The density of conservation trees was higher on forestland of high than of low productivity. Thus, the soft conservation policy did not influence regeneration of saplings in this type of forestry system, but large broadleaved trees were increasingly saved at 'clear-cuttings'. Advice and educational programmes probably contributed to this result. A continued increase in conservation trees at harvest may require economical support to forest owners.     

Urban–rural differences in atmospheric mercury speciation

Measurements of gaseous elemental mercury (GEM), particulate mercury (Hg_p), and reactive gaseous mercury (RGM) were concurrently recorded at an urban site in Detroit and a rural site in Dexter, both in Michigan for the calendar year 2004. Their average concentrations (±standard deviation) for the urban area were 2.5 ± 1.4 ng m^?3, 18.1 ± 61.0 pg m^?3, and 15.5 ± 54.9 pg m^?3, respectively, while their rural counterparts were 1.6 ± 0.6 ng m^?3, 6.1 ± 5.5 pg m^?3, and 3.8 ± 6.6 pg m^?3, respectively. The medians of urban-to-rural ratios of Hg concentrations indicate approximately 1-fold, 2-fold, and 3-fold gradients between Detroit and Dexter for GEM, Hg_p, and RGM, respectively. The urban–rural differences in Hg also varied considerably on different temporal scales and with wind flow patterns, which was most evident in RGM. Our results show that while Hg at both sites was impacted by regional sources, meteorological conditions, and photochemical transformations, the extent of variations in the observed urban-to-rural gradients, particularly in RGM, cannot be fully accounted for by these processes. Both analyses of the annual data and case studies indicate that the more variable and episodic nature of Hg, particularly RGM, seen in Detroit compared with Dexter, was the result of direct impact from local anthropogenic sources.     

Hydroxyl radical (OH) yields from the ozonolysis of both double bonds for five monoterpenes

A new method has been applied to determine OH-radical yields from the ozonolysis of both double bonds from five selected, atmospherically relevant monoterpenes, namely terpinolene, α-phellandrene, limonene, α-terpinene and γ-terpinene. While OH-yields for the faster reacting double bond agreed with previous literature values, the yields from the second double bond were determined for the first time and are as follows: limonene 7–10%, terpinolene 39–48%, α-phellandrene 8–11% and α-terpinene 12–14%. Only for γ-terpinene the rate coefficient for the reaction of ozone with the two double bonds was too similar in order to distinguish the OH-yield with this method. In all cases the yield from the second double bond was significantly lower than the first. The reasons for this difference are discussed in terms of the Criegee-intermediate reactions, in particular the number of abstractable H-atoms and the number of possible hydroperoxide products.     

CO2 capture for refineries,a practical approach

This paper evaluates the opportunities and associated costs for post-combustion capture at a world-scale complex refinery. It is concluded that it is technically feasible to apply post-combustion capture at such a refinery. The costs for capture and sequestration from a gasifier are calculated to be lowest at about 30 Euro per ton; this process currently already produces a concentrated CO₂ stream. Next, the CO₂ source most suited for capture appears to be a combined stack, but there are a number of other sources that may be targeted at comparable costs. In total these sources may form about 40% of the overall refinery emissions. Our evaluations show the costs of capture from such sources based on available amine technology will be in the range of 90–120 Euro per ton, which is about 3–4 times higher than the current carbon trading values. The capture of CO₂ from a large amount of smaller CO₂ sources will bring along even much higher costs. A high-level study of the CO₂ emissions profile of a number of Shell refineries shows that, typically, up to 50% of the emitted CO₂ may be captured at similar costs. About 10–20% of concentrated CO₂ associated with hydrogen manufacturing may be captured at lower costs. The remainder of emitted dilute CO₂ will bring along significantly higher costs. Based on this study, it is concluded for the justification of the implementation of post-combustion capture at refineries, either a significant increase in carbon trading values, mandatory regulations, or a major technological break-through is required.