Pb and stable lead content in fungi: Its transfer from soil

The uptake and transfer of natural radionuclides, other than ⁴⁰K, from soil to mushrooms has been somewhat overlooked in the literature. Their contribution to the dose due to the consumption of mushrooms was considered negligible. But the contribution of ²¹⁰Pb in areas unaffected by any recent radioactive fallout has been found to be significant, up to 35% of the annual dose commitment in Spain. More than 30 species of mushrooms were analyzed, and the ²¹⁰Pb detected was in the range of 0.75-202 Bq/kg d.w. A slight difference was observed between species with different nutritional mechanisms (saprophytes ≥ mycorrhizae). The ²¹⁰Pb content was correlated with the stable lead content, but not with its predecessor in the uranium radioactive series, ²²⁶Ra. This suggested that ²¹⁰Pb was taken up from the soil by the same pathway as stable lead. The bioavailability of ²¹⁰Pb in soil was determined by means of a sequential extraction procedure (NH₄OAc, 1M HCl, 6M HCl, and residue). About 30% of the ²¹⁰Pb present in the soil was available for transfer to mushrooms, more than other natural radionuclides in the same ecosystem. Lycoperdon perlatum, Hebeloma cylindrosporum, and Amanita curtipes presented the highest values of the available transfer factor, ATF. As reflected in their ATF values, the transfer from soil to mushroom of some natural and anthropogenic radionuclides was in the following order:

^228,230,232Th ≈ ⁴⁰K ≥ ¹³⁷Cs ≥ ^234,238U ≈ ²²⁶Ra ≥ ⁹⁰Sr ≥ ²¹⁰Pb ≈ ^239 + 240Pu ≈ ²⁴¹Am.     

Air pollution and meteorological processes in the growing dryland city of Urumqi (Xinjiang, China)

Seven years (2000-2006) of monthly PM₁₀ (particulate matter, d ≤ 10 μm), SO₂, and NO₂ concentrations are reported for Urumqi, the capital of Xinjiang in NW China. Considerably high mean annual concentrations have been observed, which ranged between 150 and 240 μg m^− 3 (PM₁₀), 31 and 50 μg m^− 3 (NO₂), and 49 and 160 μg m^− 3 (SO₂). The shapes of seasonal variation of all pollutants were remarkably similar; however, winter/summer ratios of concentrations were quite different for PM₁₀ (2-3) and NO₂ (≈ 4) compared to SO₂ (up to 30). Very high consumption rates of fossil fuels for energy generation and domestic heating are mainly responsible for high annual pollution levels, as well as the (very) high winter/summer ratios. Detailed analysis of the 2000-2006 records of Urumqi's meteorological data resulted in inter-annual and seasonal frequency distributions of (a) (surface) inversion events, (b) heights of surface inversions, (c) stability classes of Urumqi's boundary layer, and (d) the “Air Stagnation Index (ASI)”. Urumqi's boundary layer is shown to be characterized by high mean annual and seasonal frequencies of (surface) inversions and by the dominance of stable dispersion classes. A further outcome of the meteorological analysis is the proof of Urumqi's strong diurnal wind system, which might have particularly contributed to the stabilization of the nocturnal boundary layer. Annual and seasonal variations of pollutant's concentrations are discussed in the context of occurrences of inversions, boundary layer, stability classes, and ASI. The trend of Urumqi's air pollution indicates a strong increase of mean annual concentrations 2000-2003, followed by a slight increase during 2003-2006. These are in strong contrast to (a) the growth of Urumqi's fleet of motor vehicles and (b) to the growing number of stable regimes of Urumqi's boundary layer climate during same period. It is concluded that the (regional and) local administrative technical countermeasures have efficiently lowered Urumqi's air pollution levels.     

Sediment reworking rates in deep sediments of the Mediterranean Sea

Different pelagic areas of the Mediterranean Sea have been investigated in order to quantify physical and biological mixing processes in deep sea sediments. Herein, results of eleven sediment cores sampled at different deep areas (> 2000 m) of the Western and Eastern Mediterranean Sea are presented.²¹⁰Pb_xs and ¹³⁷Cs vertical profiles, together with ¹⁴C dating, are used to identify the main processes characterising the different areas and, finally, controlling mixing depths (SML) and bioturbation coefficients (D_b). Radionuclide vertical profiles and inventories indicate that bioturbation processes are the dominant processes responsible for sediment reworking in deep sea environments.Results show significant differences in sediment mixing depths and bioturbation coefficients among areas of the Mediterranean Sea characterised by different trophic regimes. In particular, in the Oran Rise area, where the Almeria-Oran Front induces frequent phytoplankton blooms, we calculate the highest values of sediment mixing layers (13 cm) and bioturbation coefficients (0.187 cm² yr⁻¹), and the highest values of ²¹⁰Pb_xs and ¹³⁷Cs inventories. Intermediate values of SML and D_b (~ 6 cm and ~ 0.040 cm² yr⁻¹, respectively) characterise the mesothrophic Algero-Balearic basin, while in the Southern Tyrrhenian Sea mixing parameters (SML of 3 cm and D_b of 0.011 cm² yr⁻¹) are similar to those calculated for the oligotrophic Eastern Mediterranean (SML of 2 cm and D_b of ~ 0.005 cm² yr⁻¹).     

Nitrate and fluoride contamination in groundwater of an intensively managed agroecosystem: A functional relationship

A study was conducted to assess the potential of nitrate-nitrogen (NO₃-N) and fluoride (F) contamination in drinking groundwater as a function of lithology, soil characteristics and agricultural activities in an intensively cultivated district in India. Two hundred and fifty two groundwater samples were collected at different depths from various types of wells and analyzed for pH, electrical conductivity (EC), NO₃-N load and F content. Database on lithology, soil properties, predominant cropping systems, fertilizer and pesticide uses were also recorded for the district. The NO₃-N load in groundwater samples were low ranging from 0.12 to 6.58 μg mL^− 1 with only 8.7% of them contained greater than 3.0 μg mL^− 1 well below the 10 μg mL^− 1, the threshold limit fixed by WHO for drinking purpose. Samples from the habitational areas showed higher NO₃-N content over the agricultural fields. The content decreased with increasing depth of wells (r = − 0.25, P ≤ 0.01) and increased with increasing rate of nitrogenous fertilizer application (r = 0.90, P ≤ 0.01) and was higher in areas where shallow- rather than deep-rooted crops (r = − 0.28, P = ≤ 0.01, with average root depth) are grown. The NO₃-N load also decreased with increasing bulk density (r = − 0.73, P ≤ 0.01) and clay content (r = − 0.51, P ≤ 0.01) but increased with increasing hydraulic conductivity (r = 0.68, P ≤ 0.01), organic C (r = 0.78, P ≤ 0.01) and potential plant available N (r = 0.82, P ≤ 0.01) of soils. Fluoride content in groundwater was also low (0.02 to 1.15 μg mL^− 1) with only 4.0% of them exceeding 1.0 μg mL^− 1 posing a potential threat of fluorosis. On average, its content varied little spatially and along depth of sampling aquifers indicating little occurrence of F containing rocks/minerals in the geology of the district. The content showed a significant positive correlation (r = 0.234, P = ≤ 0.01) with the amount of phosphatic fertilizer (single super phosphate) used for agriculture. Results thus indicated that the groundwater of the study area is presently safe for drinking purpose but some anthropogenic activities associated with intensive cultivation had a positive influence on its loading with NO₃-N and F.     

Atmospheric NH3 and NO2 concentration and nitrogen deposition in an agricultural catchment of Eastern China

To assess the atmospheric environmental impacts of anthropogenic reactive nitrogen in the fast-developing Eastern China region, we measured atmospheric concentrations of nitrogen dioxide (NO₂) and ammonia (NH₃) as well as the wet deposition of inorganic nitrogen (NO₃⁻ and NH₄⁺) and dissolved organic nitrogen (DON) levels in a typical agricultural catchment in Jiangsu Province, China, from October 2007 to September 2008_. The annual average gaseous concentrations of NO₂ and NH₃ were 42.2 μg m⁻³ and 4.5 μg m⁻³ (0 °C, 760 mm Hg), respectively, whereas those of NO₃⁻, NH₄⁺, and DON in the rainwater within the study catchment were 1.3, 1.3, and 0.5 mg N L⁻¹, respectively. No clear difference in gaseous NO₂ concentrations and nitrogen concentrations in collected rainwater was found between the crop field and residential sites, but the average NH₃ concentration of 5.4 μg m⁻³ in residential sites was significantly higher than that in field sites (4.1 μg m⁻³). Total depositions were 40 kg N ha⁻¹ yr⁻¹ for crop field sites and 30 kg N ha⁻¹ yr⁻¹ for residential sites, in which dry depositions (NO₂ and NH₃) were 7.6 kg N ha⁻¹ yr⁻¹ for crop field sites and 1.9 kg N ha⁻¹ yr⁻¹ for residential sites. The DON in the rainwater accounted for 16% of the total wet nitrogen deposition. Oxidized N (NO₃⁻ in the precipitation and gaseous NO₂) was the dominant form of nitrogen deposition in the studied region, indicating that reactive forms of nitrogen created from urban areas contribute greatly to N deposition in the rural area evaluated in this study.     

The effects of Aphis fabae infestation on the antioxidant response and heavy metal content in field grown Philadelphus coronarius plants

The purpose of this study was to explore a possible relationship between the soil availability of metals and their concentrations in various parts of Philadelphuscoronarius plants. Moreover, the possible impact of an aphid infestation on the contamination and antioxidant response of plants from the urban environment of Kraków and the reference rural area of Zagaje Stradowskie (southern Poland) was analyzed. The contents of the glutathione, proline, non-protein − SH groups, antioxidants, and phosphorous and the levels of guaiacol peroxidase and catalase activity in leaves and shoots either infested or not by the aphid Aphis fabae Scop., were measured. The potential bioavailability of metals (Cd; Cu; Ni; Pb; Zn) in the soil and their concentrations in P. coronarius plants originating from both sites were compared.The antioxidant responses were generally elevated in the plants in the polluted area. Such reactions were additionally changed by aphid infestation. Generally, the concentrations of metals in the HNO₃ and CaCl₂ extractants of the soils from two layers at the 0-20 and 20-40 cm depths from the polluted area were higher than in those from the reference area. Such differences were found for nickel and lead (in all examined extractants), zinc (in soil extractants from the layer at 20-40 cm) and cadmium (in HNO₃ extractants). Significant positive relationships between the lead concentrations in the soil and in the plants were found. In the parts of plants from the polluted area, higher concentrations of Pb and Zn (leaves and shoots) and Cd (shoots) were recorded. The shoots and leaves of plants infested with aphids had higher concentrations of Zn but lower Pb. Moreover, their leaves had higher contaminations of Cu and Ni. In conclusion, aphids affected not only the antioxidant response of the plants but also their contamination with metals, especially contamination of the leaves.     

Multiple site study of recent atmospheric metal (Pb, Zn and Cu) deposition in the NW Iberian Peninsula using peat cores

In order to estimate atmospheric metal deposition in Southern Europe since the beginning of the Industrial Period (~ 1850 AD), concentration profiles of Pb, Zn and Cu were determined in four ²¹⁰Pb-dated peat cores from ombrotrophic bogs in Serra do Xistral (Galicia, NW Iberian Peninsula). Maximum metal concentrations varied by a factor of 1.8 for Pb and Zn (70 to 128 μg g⁻¹ and 128 to 231 μg g⁻¹, respectively) and 3.5 for Cu (11 to 37 μg g⁻¹). The cumulative metal inventories of each core varied by a factor of 3 for all analysed metals (132 to 329 μg cm⁻² for Pb, 198 to 625 μg cm⁻² for Zn and 22 to 69 μg cm⁻² for Cu), suggesting differences in net accumulation rates among peatlands. Although results suggest that mean deposition rates vary within the studied area, the enhanced ²¹⁰Pb accumulation and the interpretation of the inventory ratios (²¹⁰Pb/Pb, Zn/Pb and Cu/Pb) in two bogs indicated that either a record perturbation or post-depositional redistribution effects must be considered. After correction, Pb, Zn and Cu profiles showed increasing concentrations and atmospheric fluxes since the mid-XX^th century to maximum values in the second half of the XX^th century. For Pb, maximum fluxes were observed in 1955-1962 and ranged from 16 to 22 mg m⁻² yr⁻¹ (mean of 18 ± 1 mg m⁻² yr⁻¹), two orders of magnitude higher than in the pre-industrial period. Peaks in Pb fluxes in Serra do Xistral before the period of maximum consumption of leaded petrol in Europe (1970s-1980s) suggest the dominance of local pollutant sources in the area (i.e. coal mining and burning). More recent peaks were observed for Zn and Cu, with fluxes ranging from 32 to 52 mg m⁻² yr⁻¹ in 1989-1996, and from 4 to 9 mg m⁻² yr⁻¹ in 1994-2001, respectively. Our results underline the importance of multi-core studies to assess both the integrity and reliability of peat records, and the degree of homogeneity in bog accumulation. We show the usefulness of using the excess ²¹⁰Pb inventory to distinguish between differential metal deposition, accumulation or anomalous peat records.     

Investigating the potential role of ammonia in ion chemistry of fine particulate matter formation for an urban environment

To investigate the potential role of ammonia in ion chemistry of PM_2.5 aerosol, measurements of PM_2.5 (particulate matter having aerodynamic diameter < 2.5 µm) along with its ionic speciation and gaseous pollutants (sulfur dioxide (SO₂), nitrogen oxides (NO_x), ammonia (NH₃) and nitric acid (HNO₃)) were undertaken in two seasons (summer and winter) of 2007-2008 at four sampling sites in Kanpur, an urban-industrial city in the Ganga basin, India. Mean concentrations of water-soluble ions were observed in the following order (i) summer: SO₄²⁻ (26.3 µg m^− 3) > NO₃⁻ (16.8) > NH₄⁺ (15.1) > Ca²⁺ (4.1) > Na⁺ (2.4) > K⁺ (2.1 µg m^− 3) and (ii) winter: SO₄²⁻ (28.9 µg m^− 3) > NO₃⁻ (23.0) > NH₄⁺ (16.4) > Ca²⁺(3.4) > K⁺(3.3) > Na⁺ (3.2 µg m^− 3). The mean molar ratio of NH₄⁺ to SO₄²⁻ was 2.8 ± 0.6 (mostly >2), indicated abundance of NH₃ to neutralize H₂SO₄. The excess of NH₄⁺ was inferred to be associated with NO₃⁻ and Cl⁻. Higher sulfur conversion ratio (F_s: 58%) than nitrogen conversion ratio (F_n: 39%) indicated that SO₄²⁻ was the preferred secondary species to NO₃⁻. The charge balance for the ion chemistry of PM_2.5 revealed that compounds formed from ammonia as precursor are (NH₄)₂SO₄, NH₄NO₃ and NH₄Cl. This study conclusively established that while there are higher contributions of NH₄⁺, SO₄²⁻ to PM_2.5 in summer but for nitrates (in particulate phase), it is the winter season, which is critical because of low temperatures that drives the reaction between ammonia and HNO₃ in forward direction for enhanced nitrate formation. In summary, inorganic secondary aerosol formation accounted for 30% mass of PM_2.5 and any particulate control strategy should include optimal control of primary precursor gases including ammonia.     

Plant tolerance to diesel minimizes its impact on soil microbial characteristics during rhizoremediation of diesel-contaminated soils

Soil contamination due to petroleum-derived products is an important environmental problem. We assessed the impacts of diesel oil on plants (Trifolium repens and Lolium perenne) and soil microbial community characteristics within the context of the rhizoremediation of contaminated soils. For this purpose, a diesel fuel spill on a grassland soil was simulated under pot conditions at a dose of 12,000 mg diesel kg^− 1 DW soil. Thirty days after diesel addition, T. repens (white clover) and L. perenne (perennial ryegrass) were sown in the pots and grown under greenhouse conditions (temperature 25/18 °C day/night, relative humidity 60/80% day/night and a photosynthetic photon flux density of 400 μmol photon m^− 2 s^− 1) for 5 months. A parallel set of unplanted pots was also included. Concentrations of n-alkanes in soil were determined as an indicator of diesel degradation. Seedling germination, plant growth, maximal photochemical efficiency of photosystem II (F_v/F_m), pigment composition and lipophylic antioxidant content were determined to assess the impacts of diesel on the studied plants. Soil microbial community characteristics, such as enzyme and community-level physiological profiles, were also determined and used to calculate the soil quality index (SQI). The presence of plants had a stimulatory effect on soil microbial activity. L. perenne was far more tolerant to diesel contamination than T. repens. Diesel contamination affected soil microbial characteristics, although its impact was less pronounced in the rhizosphere of L. perenne. Rhizoremediation with T. repens and L. perenne resulted in a similar reduction of total n-alkanes concentration. However, values of the soil microbial parameters and the SQI showed that the more tolerant species (L. perenne) was able to better maintain its rhizosphere characteristics when growing in diesel-contaminated soil, suggesting a better soil health. We concluded that plant tolerance is of crucial importance for the recovery of soil health during rhizoremediation of contaminated soils.     

(210)Po and (210)Pb in the tissues of the deep-sea hydrothermal vent mussel Bathymodiolus azoricus from the Menez Gwen field (Mid-Atlantic Ridge)

The hydrothermal deep-sea vent fauna is naturally exposed to a highly specific environment enriched in potentially toxic species such as sulfides, metals and natural radionuclides due to the convective seawater circulation inside the oceanic crust and its interaction with basaltic or ultramafic host rocks. However, data on radionuclides in biota from such environment are very limited. An investigation was carried out on tissue partitioning of ²¹⁰Po and ²¹⁰Pb, two natural radionuclides within the ²³⁸U decay chain, in Bathymodiolus azoricus specimens from the Mid-Atlantic Ridge (Menez Gwen field). These two elements showed different distributions with high ²¹⁰Pb levels in gills and high ²¹⁰Po levels in both gills and especially in the remaining parts of the body tissue (including the digestive gland). Various factors that may explain such partitioning are discussed. However, ²¹⁰Po levels encountered in B. azoricus were not exceptionally high, leading to weighted internal dose rate in the range 3 to 4 μGy h^− 1. These levels are slightly higher than levels characterizing coastal mussels (~ 1 μGy h^− 1).     

Effect of COD/SO4ratio and Fe(II) under the variable hydraulic retention time (HRT) on fermentative hydrogen production

The effect of chemical oxygen demand/sulfate (COD/SO₄²⁻) ratio on fermentative hydrogen production using enriched mixed microflora has been studied. The chemostat system maintained with a substrate (glucose) concentration of 15 g COD L⁻¹ exhibited stable H₂ production at inlet sulfate concentrations of 0-20 g L⁻¹ during 282 days. The tested COD/SO₄²⁻ ratios ranged from 150 to 0.75 (with control) at pH 5.5 with hydraulic retention time (HRT) of 24, 12 and 6 h. The hydrogen production at HRT 6 h and pH 5.5 was not influenced by decreasing the COD/SO₄²⁻ ratio from 150 to 15 (with control) followed by noticeable increase at COD/SO₄²⁻ ratios of 5 and 3, but it was slightly decreased when the COD/SO₄²⁻ ratio further decreased to 1.5 and 0.75. These results indicate that high sulfate concentrations (up to 20,000 mg L⁻¹) would not interfere with hydrogen production under the investigated experimental conditions. Maximum hydrogen production was 2.95, 4.60 and 9.40 L day⁻¹ with hydrogen yields of 2.0, 1.8 and 1.6 mol H₂ mol⁻¹ glucose at HRTs of 24, 12 and 6 h, respectively. The volatile fatty acid (VFA) fraction produced during the reaction was in the order of butyrate > acetate > ethanol > propionate in all experiments. Fluorescence In Situ Hybridization (FISH) analysis indicated the presence of Clostridium spp., Clostridium butyricum, Clostridium perfringens and Ruminococcus flavefaciens as hydrogen producing bacteria (HPB) and absence of sulfate reducing bacteria (SRB) in our study.     

Effects of wood ash fertilization on forest floor greenhouse gas emissions and tree growth in nutrient poor drained peatland forests

Wood ash (3.1, 3.3 or 6.6 tonnes dry weight ha^− 1) was used to fertilize two drained and forested peatland sites in southern Sweden. The sites were chosen to represent the Swedish peatlands that are most suitable for ash fertilization, with respect to stand growth response. The fluxes of carbon dioxide (CO₂), methane (CH₄) and nitrous oxide (N₂O) from the forest floor, measured using opaque static chambers, were monitored at both sites during 2004 and 2005 and at one of the sites during the period 1 October 2007-1 October 2008. No significant (p > 0.05) changes in forest floor greenhouse gas exchange were detected. The annual emissions of CO₂ from the sites varied between 6.4 and 15.4 tonnes ha^− 1, while the CH₄ fluxes varied between 1.9 and 12.5 kg ha^− 1. The emissions of N₂O were negligible. Ash fertilization increased soil pH at a depth of 0-0.05 m by up to 0.9 units (p < 0.01) at one site, 5 years after application, and by 0.4 units (p < 0.05) at the other site, 4 years after application. Over the first 5 years after fertilization, the mean annual tree stand basal area increment was significantly larger (p < 0.05) at the highest ash dose plots compared with control plots (0.64 m² ha^− 1 year^− 1 and 0.52 m² ha^− 1 year^− 1, respectively). The stand biomass, which was calculated using tree biomass functions, was not significantly affected by the ash treatment. The groundwater levels during the 2008 growing season were lower in the high ash dose plots than in the corresponding control plots (p < 0.05), indicating increased evapotranspiration as a result of increased tree growth. The larger basal area increment and the lowered groundwater levels in the high ash dose plots suggest that fertilization promoted tree growth, while not affecting greenhouse gas emissions.     

Whole lake selective withdrawal experiment to control harmful cyanobacteria in an urban impoundment

Different environmental conditions support optimal growth by Aphanizomenon and Microcystis in Ford Lake, Michigan, USA, based on weekly species biovolume and water chemistry measurements from June through October 2005-2007. Experimental withdrawal of hypolimnetic water through the outlet dam was conducted in 2006, with 2005 and 2007 acting as control years, to test theory regarding management of nuisance and toxic cyanobacteria. The dynamics of Aphanizomenon and Microcystis blooms in Ford Lake appear to be driven largely by NO₃⁻ concentrations, with higher levels shifting the advantage to Microcystis (P < 0.0001). Aphanizomenon was most successful with a mean TN:TP ratio (mol:mol) of 48.3:1, whereas Microcystis thrived with a mean ratio of 70.1:1. Withdrawal of hypolimnetic water successfully destabilized the water column and led to higher levels of NO₃⁻ and the near elimination of the Aphanizomenon bloom in 2006 (P < 0.0001). Selective withdrawal did not reduce Microcystis biovolume or microcystin toxicity. Microcystis biovolume and NO₃⁻ levels were positively correlated with microcystin toxin (P = 0.01) and jointly accounted for 30.5% of the variability in the data. Selective withdrawal may be a viable management option for improving water quality under certain circumstances. To fully address the problem of nuisance and toxic algal blooms in Ford Lake, however, an integrated approach is required that targets cyanobacteria biovolume dynamics as well as conditions suited for toxin production.     

Effect of pest controlling neem and mata-raton leaf extracts on greenhouse gas emissions from urea-amended soil cultivated with beans: A greenhouse experiment

In a previous laboratory experiment, extracts of neem (Azadirachta indica A. Juss.) and Gliricidia sepium Jacquin, locally known as mata-raton, used to control pests on crops, inhibited emissions of CO₂ from a urea-amended soil, but not nitrification and N₂O emissions. We investigated if these extracts when applied to beans (Phaseolus vulgaris L.) affected their development, soil characteristics and emissions of carbon dioxide (CO₂) and nitrous oxide (N₂O) in a greenhouse environment. Untreated beans and beans planted with lambda-cyhalothrin, a commercial insecticide, served as controls. After 117 days, shoots of plants cultivated in soil amended with urea or treated with lambda-cyhalothrin, or extracts of neem or G. sepium were significantly higher than when cultivated in the unamended soil, while the roots were significantly longer when plants were amended with urea or treated with leaf extracts of neem or G. sepium than when treated with lambda-cyhalothrin. The number of pods, fresh and dry pod weight and seed yield was significantly higher when bean plants were treated with leaf extracts of neem or G. sepium treatments than when left untreated and unfertilized. The number of seeds was similar for the different treatments. The number of nodules was lower in plants fertilized with urea, treated with leaf extracts of neem or G. sepium, or with lambda-cyhalothrin compared to the unfertilized plants. The concentrations of NH₄⁺, NO₂⁻ and NO₃⁻ decreased significantly over time with the lowest concentrations generally found at harvest. Treatment had no significant effect on the concentrations of NH₄⁺ and NO₂⁻, but the concentration of NO₃⁻ was significantly lower in the unfertilized soil compared to the other treatments. It was found that applying extracts of neem or G. sepium leaves to beans favored their development when compared to untreated plants, but had no significant effect on nitrification in soil.     

The effects of phytophagous insects on water and soil nutrient concentrations and fluxes through forest stands of the Level II monitoring network in the UK

The effects of insect defoliators on throughfall and soil nutrient fluxes were studied in coniferous and deciduous stands at five UK intensive monitoring plots (1998 to 2008). Links were found between the dissolved organic carbon (DOC), nitrogen (N) and potassium (K) fluxes through the forest system to biological activity within the canopy. Underlying soil type determined the leaching or accumulation of these elements. Under oak, monitored at two sites, frass from caterpillars of Tortrix viridana and Operophtera brumata added direct deposition of ~ 16 kg ha⁻¹extra N during defoliation. Peaks of nitrate (NO₃-N) flux between 5 and 9 kg ha⁻¹ (×5 usual winter values) were recorded in consecutive years in shallow soil waters. Synchronous rises in deep soil NO₃-N fluxes at the Grizedale sandy site indicate downward flushing, not seen at the clay site. Under three Sitka spruce stands, generation of honeydew (DOC) was attributed to two aphid species (Elatobium abietinum and Cinara pilicornis) with distinctive feeding strategies. Throughfall DOC showed mean annual fluxes (6 seasons) ~ 45-60 kg ha⁻¹ compared with rainfall values of 14-22 kg ha⁻¹. Increases of total N in throughfall and NO₃-N fluxes in shallow soil solution were detected — soil water fluxes reached  8 kg ha⁻¹ in Llyn Brianne, ~ 25 kg ha⁻¹ in Tummel, and ~ 40 kg NO₃-N ha⁻¹ in Coalburn. At Tummel, on sandy soil, NO₃-N leaching showed increased concentration at depth, attributed to microbiological activity within the soil. By contrast, at Coalburn and Llyn Brianne, sites on peaty gleys, soil water NO₃-N was retained mostly within the humus layer. Soil type is thus key to predicting N movement and retention patterns. These long term analyses show important direct and indirect effects of phytophagous insects in forest ecosystems, on above and below ground processes affecting tree growth, soil condition, vegetation and water quality.     

Application of the Nernst-Planck approach to lead ion exchange in Ca-loaded Pelvetia canaliculata

Ca-loaded Pelvetia canaliculata biomass was used to remove Pb²⁺ in aqueous solution from batch and continuous systems. The physicochemical characterization of algae Pelvetia particles by potentiometric titration and FTIR analysis has shown a gel structure with two major binding groups - carboxylic (2.8 mmol g⁻¹) and hydroxyl (0.8 mmol g⁻¹), with an affinity constant distribution for hydrogen ions well described by a Quasi-Gaussian distribution. Equilibrium adsorption (pH 3 and 5) and desorption (eluents: HNO₃ and CaCl₂) experiments were performed, showing that the biosorption mechanism was attributed to ion exchange among calcium, lead and hydrogen ions with stoichiometry 1:1 (Ca:Pb) and 1:2 (Ca:H and Pb:H). The uptake capacity of lead ions decreased with pH, suggesting that there is a competition between H⁺ and Pb²⁺ for the same binding sites. A mass action law for the ternary mixture was able to predict the equilibrium data, with the selectivity constants α_Ca^H = 9 ± 1 and α_Ca^Pb = 44 ± 5, revealing a higher affinity of the biomass towards lead ions. Adsorption (initial solution pH 4.5 and 2.5) and desorption (0.3 M HNO₃) kinetics were performed in batch and continuous systems. A mass transfer model using the Nernst-Planck approximation for the ionic flux of each counter-ion was used for the prediction of the ions profiles in batch systems and packed bed columns. The intraparticle effective diffusion constants were determined as 3.73 × 10⁻⁷ cm² s⁻¹ for H⁺, 7.56 × 10⁻⁸ cm² s⁻¹ for Pb²⁺ and 6.37 × 10⁻⁸ cm² s⁻¹ for Ca²⁺.     

Temporal variation of nitro-polycyclic aromatic hydrocarbons in PM10 and PM2.5 collected in Northern Mexico City

With the aim to determine the presence of individual nitro-PAH contained in particles in the atmosphere of Mexico City, a monitoring campaign for particulate matter (PM₁₀ and PM_2.5) was carried out in Northern Mexico City, from April 2006 to February 2007. The PM₁₀ annual median concentration was 65.2 μg m^− 3 associated to 7.6 μg m^− 3 of solvent-extractable organic matter (SEOM) corresponding to 11.4% of the PM₁₀ concentration and 38.6 μg m^− 3 with 5.9 μg m^− 3 SEOM corresponding to 15.2% for PM_2.5. PM concentration and SEOM varied with the season and the particle size. The quantification of nitro-polycyclic aromatic hydrocarbons (nitro-PAH) was developed through the standards addition method under two schemes: reference standard with and without matrix, the former giving the best results. The recovery percentages varied with the extraction method within the 52 to 97% range depending on each nitro-PAH. The determination of the latter was effected with and without sample purification, also termed fractioning, giving similar results. 8 nitro-PAH were quantified, and their sum ranged from 111 to 819 pg m^− 3 for PM₁₀ and from 58 to 383 pg m^− 3 for PM_2.5, depending on the season. The greatest concentration was for 9-Nitroanthracene in PM₁₀ and PM_2.5, detected during the cold-dry season, with a median (10th-90th percentiles) concentration in 235 pg m^− 3 (66-449 pg m^− 3) for PM₁₀ and 73 pg m^− 3 (18-117 pg m^− 3) for PM_2.5. The correlation among mass concentrations of the nitro-PAH and criteria pollutants was statistically significant for some nitro-PAH with PM₁₀, SEOM in PM₁₀, SEOM in PM_2.5, NO_X, NO₂ and CO, suggesting either sources, primary or secondary origin. The measured concentrations of nitro-PAH were higher than those reported in other countries, but lower than those from Chinese cities. Knowledge of nitro-PAH atmospheric concentrations can aid during the surveillance of diseases (cardiovascular and cancer risk) associated with these exposures.     

Development of a TiO2 modified optical fiber electrode and its incorporation into a photoelectrochemical reactor for wastewater treatment

Electrochemical advanced oxidation processes (EAOPs) are used to chemically burn non biodegradable complex organic compounds that are present in polluted effluents. A common approach involves the use of TiO₂ semiconductor substrates as either photocatalytic or photoelectrocatalytic materials in reactors that produce a powerful oxidant (hydroxyl radical) that reacts with pollutant species. In this context, the purpose of this work is to develop a new TiO₂ based photoanode using an optic fiber support. The novel arrangement of a TiO₂ layer positioned on top of a surface modified optical fiber substrate, allowed the construction of a photoelectrochemical reactor that works on the basis of an internally illuminated approach. In this way, a semi-conductive optical fiber modified surface was prepared using 30 μm thickness SnO₂:Sb films on which the photoactive TiO₂ layer was electrophoretically deposited. UV light transmission experiments were conducted to evaluate the transmittance along the optical fiber covered with SnO₂:Sb and TiO₂ showing that 43% of UV light reached the optical fiber tip. With different illumination configurations (external or internal), it was possible to get an increase in the amount of photo-generated H₂O₂ close to 50% as compared to different types of TiO₂ films. Finally, the electro-Fenton photoelectrocatalytic Oxidation process studied in this work was able to achieve total color removal of Azo orange II dye (15 mg L⁻¹) and a 57% removal of total organic carbon (TOC) within 60 min of degradation time.     

Influence of soil properties on trace element availability and plant accumulation in a Mediterranean salt marsh polluted by mining wastes: implications for phytomanagement

The aims of this study were to determine the factors which control metal and As phytoavailability in the different microenvironments (Sand Dunes, Salt Flat, Dry River and Shrubs) present at a Mediterranean salt marsh polluted by mining wastes. We performed a field study following a plot sampling survey. The analyses of soil parameters (pH, electrical conductivity (EC), organic carbon contents, etc.), total metal and As concentrations and their phytoavailability assessed with EDTA were related to each microenvironment and the corresponding plant species uptake. The averages of pH and EC were slightly alkaline (pH ≈ 7.5) and saline (≈ 2.2 to 17.1 dS m⁻¹) respectively. The soil samples from the Salt Flat subzone showed the highest metal concentrations (e.g. 51 mg kg⁻¹ Cd, 11,600 mg kg⁻¹ Pb) while for As, the highest concentrations occurred in the Dry River (380 mg kg⁻¹ As). The total metal and EDTA-extractable concentrations occurred as it follows: Salt Flat > Dry River > Degraded Dunes > Shrubs. In relation to plant metal and As accumulation, the highest root concentrations were obtained in the species from the Salt Flat subzone: ~ 17 mg kg⁻¹ As, ~ 620 mg kg⁻¹ Pb, for both, Juncus maritimus and Arthrocnemum macrostachyum. However the highest metal and As shoot concentrations occurred in species from the Sand Dunes: ~ 23 mg kg⁻¹ As ~ 270 mg kg⁻¹ Pb for Dittrichia viscosa; ~ 23 mg kg⁻¹ As, ~ 390 mg kg⁻¹ Zn for Crucianella maritima. The occurrence of edaphic gradients including salinity and texture determined the vegetation distribution. However, it cannot be concluded that there was a disturbance due to metal(loid)s soil concentrations in terms of vegetation composition except in the Degraded Dunes and Dry River. The higher EDTA-extractable concentrations were coincidental with the most saline soils but this did not result in higher metal(loid)s plant accumulation.     

Comparison of toxicity and release rates of Cu and Zn from anti-fouling paints leached in natural and artificial brackish seawater

Biocide-containing anti-fouling paints are regulated and approved according to the added active ingredients, such as Cu. Biocide-free paints are considered to be less environmentally damaging and do not need an approval. Zn, a common ingredient in paints with the potential of causing adverse effects has received only minor attention. Laboratory experiments were conducted in artificial brackish seawater (ASW) and natural brackish seawater (NSW) to quantify release rates of Cu and Zn from biocide-containing and biocide-free labeled eroding anti-fouling paints used on commercial vessels as well as leisure boats. In addition, organisms from three trophic levels, the crustacean Nitocra spinipes, the macroalga Ceramium tenuicorne and the bacteria Vibrio fischeri, were exposed to Cu and Zn to determine the toxicity of these metals. The release rate of Cu in NSW was higher from the paints for professional use (3.2-3.6 µg cm⁻² d^− 1) than from the biocide leaching leisure boat paint (1.1 µg cm⁻² d^− 1). Biocide-free paints did leach considerably more Zn (4.4-8.2 µg cm⁻² d^− 1) than biocide-containing leisure boat paint (3.0 µg cm⁻² d^− 1) and ship paints (0.7-2.0 µg cm⁻² d^− 1). In ASW the release rates of both metals were notably higher than in NSW for most tested paints. The macroalga was the most sensitive species to both Cu (EC₅₀ = 6.4 µg l^− 1) and Zn (EC₅₀ = 25 µg l^− 1) compared to the crustacean (Cu, LC₅₀ = 2000 µg l^− 1 Zn, LC₅₀ = 890 µg l^− 1), and the bacteria (Cu, EC₅₀ = 800 µg l^− 1 and Zn, EC₅₀ = 2000 µg l^− 1). The results suggest that the amounts of Zn and Cu leached from anti-fouling paints may attain toxic concentrations in areas with high boat density. To fully account for potential ecological risk associated with anti-fouling paints, Zn as well as active ingredients should be considered in the regulatory process.