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1.
Artificial radionuclides enter the Mediterranean Sea mainly through atmospheric deposition following nuclear weapons tests and the Chernobyl accident, but also through the river discharge of nuclear facility effluents. Previous studies of artificial radionuclides impact of the Mediterranean Sea have focussed on shallow, coastal sediments. However, deep sea sediments have the potential to store and accumulate pollutants, including artificial radionuclides. Deep sea marine sediment cores were collected from Mediterranean Sea abyssal plains (depth > 2000 m) and analysed for 239,240Pu and 137Cs to elucidate the concentrations, inventories and sources of these radionuclides in the deepest areas of the Mediterranean. The activity — depth profiles of 210Pb, together with 14C dating, indicate that sediment mixing redistributes the artificial radionuclides within the first 2.5 cm of the sedimentary column. The excess 210Pb inventory was used to normalize 239,240Pu and 137Cs inventories for variable sediment fluxes. The 239,240Pu/210Pbxs ratio was uniform across the entire sea, with a mean value of 1.24 × 10− 3, indicating homogeneous fallout of 239,240Pu. The 137Cs/210Pbxs ratio showed differences between the eastern (0.049) and western basins (0.030), clearly significant impact of deep sea sediments from the Chernobyl accident. The inventory ratios of 239,240Pu/137Cs were 0.041 and 0.025 in the western and eastern basins respectively, greater than the fallout ratio, 0.021, showing more efficient scavenging of 239,240Pu in the water column and major sedimentation of 137Cs in the eastern basin. Although areas with water depths of > 2000 m constitute around 40% of the entire Mediterranean basin, the sediments in these regions only contained 2.7% of the 239,240Pu and 0.95% of the 137Cs deposited across the Sea in 2000. These data show that the accumulation of artificial radionuclides in deep Mediterranean environments is much lower than predicted by other studies from the analysis of continental shelf sediments.  相似文献   

2.
The 239+240Pu concentrations and 240Pu/239Pu atom ratios were determined by alpha spectrometry and double-focusing SF-ICP-MS for seawater samples obtained in 1984 and 1993 from the Yamato and Tsushima Basins of the Japan Sea in the western North Pacific margin. The total 239+240Pu inventories in the whole water columns were approximately doubled during the period from 1984 to 1993 in the two basins. The increasing rates were estimated to be 5.1 Bq m−2 yr−1 in the Yamato Basin and 4.2 Bq m−2 yr−1 in the Tsushima Basin and they corresponded to ~ 0.02% of the annual 239+240Pu inflow rate into the Japan Sea through the Tsushima Strait. The mean 240Pu/239Pu atom ratios were ~ 0.240 and significantly higher than the mean global fallout ratio of 0.18. Furthermore, there were no temporal or spatial variations of 240Pu/239Pu atom ratios during this period in the Japan Sea. The total 239+240Pu inventories originating from the close-in fallout increased from 17.6 Bq m−2 to 34.6 Bq m−2 in the Yamato Basin and from 20.1 Bq m−2 to 34.6 Bq m−2 in the Tsushima Basin; however, the relative percentage of ~ 40% from the close-in fallout was unchanged during this period. A likely mechanism for the increasing Pu inventory would be the continuous inflow of the Tsushima Current from the western North Pacific, and the removal of Pu from surface waters by scavenging onto the settling particles, followed by regeneration of Pu from the settling particles during the downward transport.  相似文献   

3.
The study of a Posidonia oceanica mat (a peat-like marine sediment) core has provided a record of changes in heavy metal abundances (Fe, Mn, Ni, Cr, Cu, Pb, Cd, Zn, As and Al) since the Mid-Holocene (last 4470 yr) in Portlligat Bay (NW Mediterranean). Metal contents were determined in P. oceanica. Both, the concentration records and the results of principal components analysis showed that metal pollution in the studied bay started ca. 2800 yr BP and steadily increased until present. The increase in Fe, Cu, Pb, Cd, Zn and As concentrations since ca. 2800 yr BP and in particular during Greek (ca. 2680-2465 cal BP) and Roman (ca. 2150-1740 cal BP) times shows an early anthropogenic pollution rise in the bay, which might be associated with large- and short-scale cultural and technological development. In the last ca. 1000 yr the concentrations of heavy metals, mainly derived from anthropogenic activities, have significantly increased (e.g. from ~ 15 to 47 μg g− 1 for Pb, ~ 23 to 95 μg g− 1 for Zn and ~ 8 to 228 μg g− 1 for As). Our study demonstrates for the first time the uniqueness of P. oceanica meadows as long-term archives of abundances, patterns, and trends of heavy metals during the Late Holocene in Mediterranean coastal ecosystems.  相似文献   

4.
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-XXth century to maximum values in the second half of the XXth 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.  相似文献   

5.
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 m3 and 4.5 μg m3 (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 L1, 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 m3 in residential sites was significantly higher than that in field sites (4.1 μg m3). Total depositions were 40 kg N ha1 yr1 for crop field sites and 30 kg N ha1 yr1 for residential sites, in which dry depositions (NO2 and NH3) were 7.6 kg N ha1 yr1 for crop field sites and 1.9 kg N ha1 yr1 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.  相似文献   

6.
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 cm2 d− 1) than from the biocide leaching leisure boat paint (1.1 µg cm2 d− 1). Biocide-free paints did leach considerably more Zn (4.4-8.2 µg cm2 d− 1) than biocide-containing leisure boat paint (3.0 µg cm2 d− 1) and ship paints (0.7-2.0 µg cm2 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.  相似文献   

7.
Soil cores and rainwater were sampled under canopies of Cryptomeria japonica in four montane areas along an atmospheric depositional gradient in Kanto, Japan. Soil cores (30 cm in depth) were divided into 2-cm or 4-cm segments for analysis. Vertical distributions of elemental enrichment ratios in soils were calculated as follows: (X/Al)i/(X/Al)BG (where the numerator and denominator are concentration ratios of element-X and Al in the i- and bottom segments of soil cores, respectively). The upper 14-cm soil layer showed higher levels of Cu, Zn, As, Sb, and Pb than the lower (14-30 cm) soil layer. In the four areas, the average enrichment ratios in the upper 6-cm soil layer were as follows: Pb (4.93) ≥ Sb (4.06) ≥ As (3.04) > Zn (1.71) ≥ Cu (1.56). Exogenous elements (kg/ha) accumulated in the upper 14-cm soil layer were as follows: Zn (26.0) > Pb (12.4) > Cu (4.48) ≥ As (3.43) ≥ Sb (0.49). These rank orders were consistent with those of elements in anthropogenic aerosols and polluted (roadside) air, respectively, indicating that air pollutants probably caused enrichment of these elements in the soil surface layer. Approximately half of the total concentrations of As, Sb, and Pb in the upper 14-cm soil layer were derived from exogenous (anthropogenic) sources. Sb showed the highest enrichment factor in anthropogenic aerosols, and shows similar deposition behavior to NO3, which is a typical acidic air pollutant. There was a strong correlation between Sb and NO3 concentrations in rainfall (e.g., in the throughfall under C. japonica: [NO3] = 21.1 [dissolved Sb], r = 0.938, p < 0.0001, n = 182). Using this correlation, total (cumulative) inputs of NO3 were estimated from the accumulated amounts of exogenous Sb in soils, i.e., 16.7 t/ha at Mt. Kinsyo (most polluted), 8.6 t/ha at Mt. Tsukuba (moderately polluted), and 5.8 t/ha at the Taga mountain system (least polluted). There are no visible ecological effects of these accumulated elements in the Kanto region at present. However, the concentrations of some elements are within a harmful range, according to the Ecological Soil Screening Levels determined by the U.S. Environmental Protection Agency.  相似文献   

8.
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).  相似文献   

9.
Gradients in phosphorus (P) removal and storage were investigated over 6 years using mesocosms (each consisting of three tanks in series) containing submerged aquatic vegetation (SAV) grown on muck and limerock (LR) substrates. Mean inflow total P concentrations (TP) of 32 μg L−1 were reduced to 15 and 17 μg L−1 in the muck and LR mesocosms, respectively. Mesocosm P loading rates (mean = 1.75 g m−2 year−1) varied widely during the study and were not correlated with outflow TP, which instead varied seasonally with lowest monthly mean values in December and January.The mesocosms initially were stocked with Najas guadalupensis, Ceratophyllum demersum, and Chara zeylanica, but became dominated by C. zeylanica. At the end of the study, highest vegetative biomass (1.1 and 1.4 kg m−2 for muck and LR substrates) and tissue P content (1775 and 1160 mg kg−1) occurred in the first tank in series, and lowest biomass (1.0 and 0.2 kg m−2) and tissue P (147 and 120 mg kg−1) in the third tank. Sediment accretion rates (2.5, 1.9 and 0.9 cm yr−1 on muck substrates), accrued sediment TP (378, 309 and 272 mg kg−1), and porewater soluble reactive P (SRP) concentrations (40, 6 and 4 μg L−1) in the first, second and third tanks, respectively, exhibited a similar decreasing spatial trend. Plant tissue calcium (Ca) near mesocosm inflow (19-30% dry weight) and outflow (23-26%) were not significantly different, and sediment Ca was also similar (range of 24 to 28%) among sequential tanks.Well-defined vegetation and sediment enrichment gradients developed in SAV wetlands operated under low TP conditions. While the mesocosm data did not reflect deterioration in treatment performance over 6 years, accumulation of P-enriched sediments near the inflow could eventually compromise hydraulic storage and P removal effectiveness of these shallow systems.  相似文献   

10.
A depth profile of 239Pu and 240Pu specific activities and isotope ratios was determined in an inter-tidal sediment core from the Esk Estuary in the northeastern Irish Sea. The study site has been impacted with plutonium through routine radionuclide discharges from the Sellafield nuclear reprocessing plant in Cumbria, NW England. A pronounced sub-surface maximum of ~ 10 kBq kg-1 was observed for 239 + 240Pu, corresponding to the peak in Pu discharge from Sellafield in 1973, with a decreasing trend with depth down to ~ 0.04 kBq kg-1 in the deeper layers. The depth profile of 239 + 240Pu specific activities together with results from gamma-ray spectrometry for 137Cs and 241Am was compared with reported releases from the Sellafield plant in order to estimate a reliable sediment chronology. The upper layers (1992 onwards) showed higher 239 + 240Pu specific activities than would be expected from the direct input of annual Sellafield discharges, indicating that the main input of Pu is from the time-integrated contaminated mud patch of the northeastern Irish Sea. The 240Pu/239Pu atom ratios ranged from ~ 0.03 in the deepest layers to > 0.20 in the sub-surface layers with an activity-weighted average of 0.181. The decreasing 240Pu/239Pu atom ratio with depth reflects the changing nature of operations at the Sellafield plant from weapons-grade Pu production to reprocessing spent nuclear fuel with higher burn-up times in the late 1950s. In addition, recent annual 240Pu/239Pu atom ratios in winkles collected during 2003-2008 from three stations along the Cumbrian coastline showed no significant spatial or temporal differences with an overall average of 0.204, which supports the hypothesis of diluted Pu input from the contaminated mud patch.  相似文献   

11.
Rhizosphere acidification of faba bean, soybean and maize   总被引:2,自引:0,他引:2  
Interspecific facilitation on phosphorus uptake was observed in faba bean/maize intercropping systems in previous studies. The mechanism behind this, however, remained unknown. Under nitrate supply, the difference in rhizosphere acidification potential was studied by directly measuring pH of the solution and by visualizing and quantifying proton efflux of roots between faba bean (Vicia faba L. cv. Lincan No.5), soybean (Glycine max L. cv. Zhonghuang No. 17) and maize (Zea mays L. cv. Zhongdan No.2) in monoculture and intercrop, supplied without or with 0.2 mmol L− 1 P as KH2PO4. The pH of the nutrient solution grown faba bean was lower than initial pH of 6.0 from day 1 to day 22 under P deficiency, whereas the pH of the solution with maize was declined from day 13 after treatment. Growing soybean increased solution pH irrespective of P supply. Under P deficiency, the proton efflux of faba bean both total (315.25 nmol h− 1 plant− 1) and specific proton efflux (0.47 nmol h− 1 cm− 1) was greater than that those of soybean (21.80 nmol h− 1 plant− 1 and 0.05 nmol h− 1 cm− 1, respectively). Faba bean had much more ability of rhizosphere acidification than soybean and maize. The result can explain partly why faba bean utilizes sparingly soluble P more effectively than soybean and maize do, and has an important implication in understanding the mechanism behind interspecific facilitation on P uptake by intercropped species.  相似文献   

12.
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.  相似文献   

13.
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 αCaH = 9 ± 1 and αCaPb = 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+.  相似文献   

14.
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.  相似文献   

15.
Radionuclides released to the atmosphere during dry weather (e.g. after a nuclear accident) may contaminate vegetable foods and cause exposure to humans via the food chain. To obtain experimental data for an appropriate assessment of this exposure path, dry deposition of radionuclides to leafy vegetables was studied under homogeneous and controlled greenhouse conditions. Gaseous 131I-tracer in predominant elemental form and particulate 134Cs-tracer at about 1 μm diameter were used to identify susceptible vegetable species with regard to contamination by these radionuclides. The persistence was examined by washing the harvested product with water. The vegetables tested were spinach (Spinacia oleracea), butterhead lettuce (Lactuca sativa var. capitata), endive (Cichorium endivia), leaf lettuce (Lactuca sativa var. crispa), curly kale (Brassica oleracea convar. acephala) and white cabbage (Brassica oleracea convar. capitata). The variation of radionuclides deposited onto each vegetable was evaluated statistically using the non-parametric Kruskal-Wallis Test and the U-test of Mann-Whitney. Significant differences in deposited 131I and 134Cs activity concentration were found among the vegetable species.For 131I, the deposition velocity to spinach normalized to the biomass of the vegetation was 0.5-0.9 cm3 g− 1 s− 1 which was the highest among all species. The particulate 134Cs deposition velocity of 0.09 cm3 g− 1 s− 1 was the highest for curly kale, which has rough and structured leaves. The lowest deposition velocity was onto white cabbage: 0.02 cm3 g− 1 s− 1 (iodine) and 0.003 cm3 g− 1 s− 1 (caesium). For all species, the gaseous iodine deposition was significantly higher compared to the particulate caesium deposition. The deposition depends on the sensitive parameters leaf area, stomatal aperture, and plant morphology. Decontamination by washing with water was very limited for iodine but up to a factor of two for caesium.  相似文献   

16.
CeO2 nanoparticles were synthesized hydrothermally and utilized as redox mediator for the fabrication of efficient ethanol chemi-sensor. The developed chemi-sensor showed an excellent performance for electrocatalytic oxidization of ethanol by exhibiting higher sensitivity (0.92 μA?cm− 2?mM− 1) and lower limit of detection (0.124 ± 0.010 mM) with the linear dynamic range of 0.17 mM-0.17 M. CeO2 nanoparticles have been characterized by field emission scanning electron microscopy (FESEM), Energy dispersive spectroscopy (EDS), X-ray powder diffraction (XRD), Raman spectrum, Fourier transform infrared spectroscopy (FTIR), and UV-visible absorption spectrum which revealed that the synthesized CeO2 is an aggregated form of optically active spherical nanoparticles with the range of 15-36 nm (average size of ~ 25 ±10 nm) and possessing well crystalline cubic phase. Additionally, CeO2 performed well as a photo-catalyst by degrading amido black and acridine orange.  相似文献   

17.
Recent researches revealed the exciting application of 210Po in tracing carbon and nitrogen cycling in the coral reef system. In order to quantify the recycling of particulate organic nitrogen (PON), both 210Po and 210Pb were examined at both high and low tides in the Zhubi Coral Reef lagoon, the South China Sea. Unusually, much higher 210Po activities and 210Po/210Pb ratios, in comparison with those found in the open seawater and the lagoon subsurface water, showed additional input of 210Po besides production from in situ210Pb in the lagoon surface water. Statistical analysis identified that the reef flat seawater was the additional 210Po source. Based on a mass balance model, the input rates of 210Po varied from 0.04 Bq m−3 year−1 to 8.41 Bq m−3 year−1. On average, the additional 210Po contributed more than 60% of the total 210Po. The particulate 210Po significantly correlated with the concentrations of PON, indicating that diffusion of 210Po from sediment could be used to quantify the recycling of nitrogen. The average input rate of nitrogen was 16 mmol m−3 year−1, which can support up to 11% of the primary production rate. These results suggested that the unusual behavior of 210Po could provide new insight into the nitrogen recycling in the coral reef system.  相似文献   

18.
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.  相似文献   

19.
Biological ammoniacal-nitrogen (NH4+-N) and organic carbon (TOC) treatment was investigated in replicated mesoscale attached microbial film trickling filters, treating strong and weak strength landfill leachates in batch mode at temperatures of 3, 10, 15 and 30 °C. Comparing leachates, rates of NH4+-N reduction (0.126-0.159 g m− 2 d− 1) were predominantly unaffected by leachate characteristics; there were significant differences in TOC rates (0.072-0.194 g m− 2 d− 1) but no trend relating to leachate strength. Rates of total oxidised nitrogen (TON) accumulation (0.012-0.144 g m− 2 d− 1) were slower for strong leachates. Comparing temperatures, treatment rates varied between 0.029-0.319 g NH4+-N m− 2 d− 1 and 0.033-0.251 g C m− 2 d− 1 generally increasing with rising temperatures; rates at 3 °C were 9 and 13% of those at 30 °C for NH4+-N and TOC respectively. For the weak leachates (NH4+-N < 140 mg l− 1) complete oxidation of NH4+-N was achieved. For the strong leachates (NH4+-N 883-1150 mg l− 1) a biphasic treatment response resulted in NH4+-N removal efficiencies of between 68 and 88% and for one leachate no direct transformation of NH4+-N to TON in bulk leachate. The temporal decoupling of NH4+-N oxidation and TON accumulation in this leachate could not be fully explained by denitrification, volatilisation or anammox, suggesting temporary storage of N within the treatment system. This study demonstrates that passive aeration trickling filters can treat well-buffered high NH4+-N strength landfill leachates under a range of temperatures and that leachate strength has no effect on initial NH4+-N treatment rates. Whether this approach is a practicable option depends on a range of site specific factors.  相似文献   

20.
Watershed mass balances for solutes of atmospheric origin may be complicated by the residence times of water and solutes at various time scales. In two small forested headwater catchments in the Appalachian Mountains of Virginia, USA, mean annual export rates of SO4= differ by a factor of 2, and seasonal variations in SO4= concentrations in atmospheric deposition and stream water are out of phase. These features were investigated by comparing 3H, 35S, δ34S, δ2H, δ18O, δ3He, CFC-12, SF6, and chemical analyses of open deposition, throughfall, stream water, and spring water. The concentrations of SO4= and radioactive 35S were about twice as high in throughfall as in open deposition, but the weighted composite values of 35S/S (11.1 and 12.1 × 10− 15) and δ34S (+ 3.8 and + 4.1‰) were similar. In both streams (Shelter Run, Mill Run), 3H concentrations and δ34S values during high flow were similar to those of modern deposition, δ2H and δ18O values exhibited damped seasonal variations, and 35S/S ratios (0-3 × 10− 15) were low throughout the year, indicating inter-seasonal to inter-annual storage and release of atmospheric SO4= in both watersheds. In the Mill Run watershed, 3H concentrations in stream base flow (10-13 TU) were consistent with relatively young groundwater discharge, most δ34S values were approximately the same as the modern atmospheric deposition values, and the annual export rate of SO4= was equal to or slightly greater than the modern deposition rate. In the Shelter Run watershed, 3H concentrations in stream base flow (1-3 TU) indicate that much of the discharging ground water had been deposited prior to the onset of atmospheric nuclear bomb testing in the 1950s, base flow δ34S values (+ 1.6‰) were significantly lower than the modern deposition values, and the annual export rate of SO4= was less than the modern deposition rate. Concentrations of 3H and 35S in Shelter Run base flow, and of 3H, 3He, CFC-12, SF6, and 35S in a spring discharging to Shelter Run, all were consistent with a bimodal distribution of discharging ground-water ages with approximately 5-20% less than a few years old and 75-95% more than 40 years old. These results provide evidence for 3 important time-scales of SO4= transport through the watersheds: (1) short-term (weekly to monthly) storage and release of dry deposition in the forest canopy between precipitation events; (2) mid-term (seasonal to interannual) cycles in net storage in the near-surface environment, and (3) long-term (decadal to centennial) storage in deep ground water that appears to be related to relatively low SO4= concentrations in spring discharge that dominates Shelter Run base flow. It is possible that the relatively low concentrations and low δ34S values of SO4= in spring discharge and Shelter Run base flow may reflect those of atmospheric deposition before the middle of the 20th century. In addition to storage in soils and biota, variations in ground-water residence times at a wide range of time scales may have important effects on monitoring, modeling, and predicting watershed responses to changing atmospheric deposition in small watersheds.  相似文献   

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