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1.
Methane fluxes were measured from three exposed tundra sites and four snowpack sites on the Fildes Peninsula in the maritime Antarctic in the summertime of 2002. The average fluxes at two normal tundra sites were −15.3 μg m −2 h −1 and −14.3 μg m −2 h −1, respectively. The fluxes from tundra site with fresh penguin dropping addition showed positive values with the average of 36.1 μg m −2 h −1, suggesting that the deposition of fresh droppings greatly enhanced CH 4 emissions from the poor Antarctic tundra during penguin breeding periods. The summertime variation in CH 4 flux was correlated with surface ground temperature and the precipitation. The correlation between the flux and PT 0, which is the product of the precipitation and surface ground temperature, was quite strong. The diurnal cycle of CH 4 flux from the tundra soils was not obtained due to local fluky weather conditions. The fluxes through four snowpack sites were also obtained by the vertical CH 4 concentration gradient and their average fluxes were −46.5 μg m −2 h −1, −28.2 μg m −2 h −1, −46.4 μg m −2 h −1 and −17.9 μg m −2 h −1, respectively, indicating that tundra soils under snowpack also consume atmospheric CH 4 in the maritime Antarctic; therefore these fluxes could constitute an important part of the annual CH 4 budget for Antarctic tundra ecosystem. 相似文献
2.
This study surveyed isoprene emission from 42 indigenous and exotic tropical trees in subtropic Okinawa, Japan. Of the 42 trees studied, 4 emitted isoprene at a rate in excess of 20 μg g −1 h −1, and 28 showed the rates of 1–10 μg g −1 h −1. The remainder emitted less than 1 μg g −1 h −1. The majority of trees in this study may therefore fall within the lower emitting species. However, species in Moraceae that is indigenous in Okinawa emitted isoprene at relatively higher rates with an average of 14.2 μg g −1 h −1. The highest emission rate of 107.1 μg g −1 h −1 for Ficus virgata yielded the area basis rate of 47.4 nmol m −2 s −1, which is almost equivalent to the rate of high emitting species. Furthermore, a linear relationship between light intensity and isoprene emission was noted with Ficus virgata up to 1700 μmol m −2 s −1. These findings may show the potential importance of subtropical areas as sources of isoprene to the atmosphere. 相似文献
3.
An investigation was conducted to estimate mercury emission to the atmosphere from different environmental surfaces and to assess its contribution to the local mercury budget in Chongqing, China. Mercury flux was measured using dynamic flux chamber (DFC) at six soil sites of three different areas (mercury polluted area, farmland and woodland) and four water surfaces from August 2003 to April 2004. The mercury emission fluxes were 3.5 ± 1.2–8.4 ± 2.5 ng m −2 h −1 for three shaded forest sites, 85.8 ± 32.4 ng m −2 h −1 for farming field, 12.3 ± 9.8–733.8 ± 255 ng m −2 h −1 for grassland sites, and 5.9 ± 12.6–618.6 ± 339 ng m −2 h −1 for water surfaces. Mercury exchange fluxes were generally higher from air/water surfaces than from air/soil surfaces. The mercury negative fluxes were found in tow soil sites at overcast days (mean = −6.4 ± 1.5 ng m −2 h −1). The diurnal and seasonal variations of mercury flux were observed in all sites. The mercury emission responded positively to the solar radiation, but negatively to the relative humidity. The mercury flux from air/soil surfaces was significantly correlated with soil temperature, which was well described by an Arrhenius-type expression with activation energy of 31.1 kcal mol −1. The annual mercury emission to the atmosphere from land surface is about 1.787 t of mercury in Chongqing. 相似文献
4.
Atmospheric Hg transfer to the forest soil through litterfall was investigated in a primary rainforest at Ilha Grande (Southeast Brazil) from January to December 1997. Litter mass deposition reached 10.0 t ha −1 y −1, with leaves composing 50–84% of the total litter mass. Concentrations of Hg in the total fallen litter varied from 20 to 244 ng g −1, with higher concentrations during the dry season, between June and August (225 ± 17 ng g −1), and lower concentrations during the rainy season (99 ± 54 ng g −1). This seasonal variability was reflected in the Hg flux through litterfall, which corresponded to a Hg input to the forest floor of 122 μg m −2 y −1, with average Hg deposition of 16.5 ± 1.5 μg m −2 month −1 during and just after the dry season (June–September) and 7.0 ± 3.6 μg m −2 month −1 in the rest of the year. The variability in meteorological conditions (determining atmospheric Hg availability to foliar scavenging) may explain the pulsed pattern of Hg deposition, since litterfall temporal variability was generally unrelated with such deposition, except by a peak in litterfall production in September. Comparisons with regional data on Hg atmospheric deposition show that litterfall promotes Hg deposition at Ilha Grande two to three orders of magnitude higher than open rainfall deposition in non-industrialized areas and approximately two times higher than open rainfall deposition in industrialized areas in Rio de Janeiro State. The observed input suggests that atmospheric Hg transfer through litterfall may explain a larger fraction of the total Hg input to forest soils in Southeast Brazil than those recorded at higher latitudes. 相似文献
5.
The purpose of our study was to test the hypothesis that dissolved gaseous mercury (DGM) production and evasion is directly proportional to the loading rate of inorganic mercury [Hg(II)] to aquatic ecosystems. We simulated different rates of atmospheric mercury deposition in 10-m diameter mesocosms in a boreal lake by adding multiple additions of Hg(II) enriched with a stable mercury isotope ( 202Hg). We measured DGM concentrations in surface waters and estimated evasion rates using the thin-film gas exchange model and mass transfer coefficients derived from sulfur hexafluoride (SF 6) additions. The additions of Hg(II) stimulated DGM production, indicating that newly added Hg(II) was highly reactive. Concentrations of DGM derived from the experimental Hg(II) additions (“spike DGM”) were directly proportional to the rate of Hg(II) loading to the mesocosms. Spike DGM concentrations averaged 0.15, 0.48 and 0.94 ng l −1 in mesocosms loaded at 7.1, 14.2, and 35.5 μg Hg m −2 yr −1, respectively. The evasion rates of spike DGM from these mesocosms averaged 4.2, 17.2, and 22.3 ng m −2 h −1, respectively. The percentage of Hg(II) added to the mesocosms that was lost to the atmosphere was substantial (33–59% over 8 weeks) and was unrelated to the rate of Hg(II) loading. We conclude that changes in atmospheric mercury deposition to aquatic ecosystems will not change the relative proportion of mercury recycled to the atmosphere. 相似文献
6.
Determination of triazines herbicides (atrazine and simazine) by high performance liquid chromatography (HPLC) in samples of trophic chain were worked out. Determination limits of 0.5 μg g −1 for atrazine, 0.8 μg g −1 for simazine with pesticides recovery of 70–77% in trophic chain samples were obtained. The content of simazine in soils was in range 1.72–57.89 μg g −1, in grass 5–88 μg g −1, in milk 2.32–15.29 μg g −1, in cereals 10.98–387 μg g −1, in eggs 30.14–59.48 μg g −1, for fruits: 2.45–6.19 μg g −1. The content of atrazine in soils was in range 0.69–19.59 μg g −1, in grass 7.85–23.85 μg g −1, in cereals 1.88–43.08 μg g −1. Cadmium, lead and zinc were determined by inductively coupled plasma atomic emission spectrometry (ICP-AES) in the same samples as atrazine and simazine. Determination limits for cadmium 5 × 10 −3 μg g −1, for lead 1 × 10 −2 μg g −1, and for zinc 0.2 × 10 −3 μg g −1, were obtained. The content of cadmium in soil was in range 0.13–5.89 μg g −1, in grass 114–627.72 × 10 −3 μg g −1, in milk 8.88–61.88 × 10 −3 μg g −1, in cereals 0.20–0.31 μg g −1, in eggs 0.11–0.15 μg g −1, in fruits 0.23–0.59 μg g −1. The content of lead in soils was in range 0.57–151.50 μg g −1, in grass 0.16–136.57 μg g −1, in milk 1.16–3.74 μg g −1, in cereals 1.05–5.47 μg g −1, in eggs 5.79–55.87 μg g −1, in fruits 21.00–87.36 μg g −1. Zinc content in soil was in range 9.15–424.5 μg g −1, in grass 35.20–55.87 μg g −1, in milk 20.00–34.38 μg g −1, in cereals 14.94–28.78 μg g −1, in eggs 15.67–32.01 μg g −1, in fruits 14.94–18.88 μg g −1. Described below extraction and mineralization methods for particular trophic chains allowed to determine of atrazine, simazine, cadmium, lead and zinc with good repeatability and precision. Emphasis was focused on liquid–liquid extraction and solid-phase extraction of atrazine and simazine from analysed materials, as well as, on monitoring the content of herbicides and metals in soil and along trophic chain. Higher concentration of pesticides in samples from west region of Poland in comparison to that of east region is likely related to common applying them in Western Europe in relation to East Europe. The content of metals strongly depends on samples origin (industry area, vicinity of motorways). 相似文献
7.
The nitrous oxide emissions were measured at three tundra sites and one snowpack on the Fildes Peninsula in the maritime Antarctic in the summertime of 2002. The average fluxes at two normal tundra sites were 1.1 ± 2.2 and 0.6 ± 1.7 μg N 2O m −2 h −1, respectively. The average flux from tundra soil site with penguin dropping addition was 3.7 ± 2.0 μg N 2O m −2 h −1, 3–6 times those from the normal tundra soils, suggesting that the deposition of fresh droppings enhanced N 2O emissions during penguin breeding period. The summer precipitation had an important effect on N 2O emissions; the flux decreased when heavy precipitation occurred. The diurnal cycle of the N 2O fluxes from Antarctic tundra soils was not obtained due to local fluky weather conditions. The N 2O fluxes through four snowpack sites were obtained by the vertical N 2O concentration gradient and their average fluxes were 0.94, 1.36, 0.81 and 0.85 μg N 2O m −2 h −1, respectively. The tundra soils under snowpack emitted N 2O in the maritime Antarctic and increased local atmospheric N 2O concentrations; therefore these fluxes could constitute an important part of the annual N 2O budget for Antarctic tundra ecosystem. 相似文献
8.
Wetland loss along the Louisiana Gulf coast and excessive nitrate loading into the Gulf of Mexico are interrelated environmental problems. Nitrate removal by soil denitrification activity was studied in a ponded freshwater marsh receiving diverted Mississippi River water for the purpose of reversing or slowing wetland loss. Labeled 15N-nitrate was applied at 3.8 g N m −2 into four replicate study plots after removing above ground vegetation. Nitrogen gas (N 2) and nitrous oxide (N 2O) emissions from the plots were determined by isotope ratio mass spectrometry (IRMS). Nitrous oxide emissions were also compared with the results determined by gas chromatograph (GC). Results showed that it took 2 weeks to remove the added nitrate with N 2O emission occurring over a period of 4 d. The apparent denitrification dynamics were assumed to follow the Michaelis–Menten equation. The maximum denitrification rate and Km value were determined as 12.6 mg N m −2 h −1, and 6.5 mg N l −1, respectively. Therefore the maximum capacity for nitrate removal by the marsh soil would be equivalent to 110 g N m −2 yr −1, with more than 30% of nitrogen gas evolved as N 2O. For typical nitrate concentrations in Mississippi River water of about 1 mg N l −1, nitrate would be removed at a rate of 14.7 g N m −2 yr −1 with N 2O emission about 1.5%. A denitrification dynamic model showed that the efficiency of nitrate removal would largely depend on the water discharge rate into the ponded wetland. Higher discharge rate will result in less retention time for the water in the marsh where nitrate is denitrified. 相似文献
9.
Cold season (winter and thaw) CH 4, CO 2 and N 2O fluxes from freshwater marshes (47°35′N, 133°31′E, Northeast China) were measured, using the static chamber method. The mean CH 4 and CO 2 fluxes from Carex lasiocarpa (Cl) were 0.5 ± 0.19 and 6.23 ± 1.36 mg C m −2 h −1, respectively, and those from Deyeuxia angustifoli (Da) were 0.18 ± 0.15 and 5.22 ± 2.48 mg C m −2 h −1, respectively in winter. There was no significant difference between Cl and Da ( p > 0.05). The contributions of winter CH 4 fluxes were about 5.5% and 3% in the Cl and Da, respectively. Marshes are an important potential N 2O sink in winter season in northeast China. During thaw, the CH 4 and CO 2 emissions rapidly increased, 4.5–6 times of winter emissions. Wetland became a source of N 2O. Cold season gases flux from northern wetlands play an important role in the seasonal gas exchange. 相似文献
10.
The fluorescence spectroscopic behavior of bromadiolone (anticoagulant rodenticide), a substituted 4-hydroxycoumarin derivative, was investigated in water and in organized media like micelles and cyclodextrins. A detailed study on various photophysical parameters like fluorescence intensity ( IF), quantum yield ( ), lifetime ( τ) and steady state fluorescence anisotropy ( r) of bromadiolone in aqueous and in organized media was carried out. Bromadiolone in aqueous solution was observed to be in an aggregated state, thereby showing weak emission due to self-quenching. Marked enhancement of fluorescence intensity was observed in organized media like micelles and β-cyclodextrin. A preliminary investigation has been done to find out whether this enhancement of fluorescence can be used to develop a sensitive analytical method for determination of bromadialone in aqueous media. A linear relationship between the fluorescence intensity and concentration of bromadiolone was observed in the range of 0.15–7.9 μg ml −1 in cetyltrimethylammonium bromide (CTAB) and 0.5–26.4 μg ml −1 in β-cyclodextrin medium. The lower detection limit was found to be 37 ng ml −1 in presence of CTAB and 23 ng ml −1 in β-cyclodextrin. Comparison with 4-hydroxycoumarin, an unsubstituted analogue, was made. 相似文献
11.
The present work focuses on the fate of two cancerostatic platinum compounds (CPC), cisplatin and carboplatin, as well as of two inorganic platinum compounds, [PtCl 4] 2− and [PtCl 6] 2− in biological wastewater treatment. Laboratory experiments modelling adsorption of these compounds onto activated sludge showed promising specific adsorption coefficients KD and KOC and Freundlich adsorption isotherms. However, the adsorption properties of the investigated substances were differing significantly. Adsorption decreased following the order cisplatin > [PtCl 6] 2− > [PtCl 4] 2− > carboplatin. Log KD-values were ranging from 2.5 to 4.3 , log KOC from 3.0 to 4.7. A pilot membrane bioreactor system (MBR) was installed in a hospital in Vienna and fed with wastewater from the oncologic in-patient treatment ward to investigate CPC-adsorption in a sewage treatment plant. During three monitoring periods Pt-concentrations were measured in the influent (3–250 μg l−1 Pt) and the effluent (2–150 μg l−1 Pt) of the treatment plant using ICP-MS. The monitoring periods (duration 30 d) revealed elimination efficiencies between 51% and 63% based on averaged weekly input–output budgets. The derived log KD-values and log KOC-values ranged from 2.4 to 4.8 and from 2.8 to 5.3, respectively. Species analysis using HPLC-ICP-MS proofed that mainly carboplatin was present as intact drug in the influent and – due to low log KD – in the effluent of the MBR. 相似文献
12.
The estrogenic pollutants 4- tert-octylphenol (OP), 4-nonylphenol (NP) and bisphenol A (BPA) were determined in surface water samples from the Haihe River, Tianjin, China. The analytes were extracted and concentrated from 300 ml acidified water samples by liquid–liquid extractions using dichloromethane, derivatized with trifluoroacetic anhydride, and quantified by gas chromatography–mass spectrometry (GC–MS) with selected ion monitoring (SIM). Among the samples collected from 14 sampling sites, only one sample was found to have a relatively high concentration of BPA (8.30 μg l −1) and NP (0.55 μg l −1). The concentrations of OP, NP and BPA in the other samples were in the range of 18.0–20.2, 106–296 and 19.1–106 ng l −1, respectively. Recoveries for OP, NP and BPA in the spiked water samples were all over 80%. 相似文献
13.
The concentrations of total gaseous mercury (TGM) and its relevant environmental parameters were measured at a highly industrialized area in the Ban Wall industrial complex (BWIC) in An San city, Korea from March to May 2005. The mean concentrations of Hg measured during the entire study period were computed to be 6.32 ± 8.56 ng m −3 (range of 2.32–181 ng m −3; N = 1160). Due to the effects of strong man-made activities, the significantly high Hg concentration levels (e.g., at or above 10 ng m −3) comprised about 7.5% of all data with the mean of 21.8 ± 26.3 ng m −3 ( N = 87). By separating the data into daytime and nighttime periods, the Hg values exhibited a notable daytime enhancement possibly due to strong man-made activities during working hours. The results of the correlation analysis indicated the possible relationship between the Hg concentration and the temperature as well as several pollutant species (e.g., NO 2 and NO x). Evaluation of the Hg data in relation with the air mass transport pattern confirms that the Hg concentration levels in this industrial area are affected most eminently by local, rather than distant, pollution sources. 相似文献
14.
The absolute contents and relative distributions of organic aerosols [ n-alkanes, n-alkanoic and n-alkenoic acids, n-alkan-2-ones and polycyclic aromatic hydrocarbons (PAH)] were determined in torched gases emitted during the crude oil extraction and in the free atmosphere of the Hassi-Messaoud city (Algeria). Monocarboxylic acids, both saturated and monounsaturated (from 9802 to 20 057 ng m −3), accounted for the major fraction of the total particulate organic matter identified both in torch exhaust and atmospheric particulate. n-Alkanes were also abundant both in the direct emission (from 460 to 632 ng m −3) and city atmosphere (462 ng m −3) and displayed a peculiar fingerprint characterised by the presence of a set of branched congeners around even carbon-numbered homologues and a strong even-to-odd predominance along the whole carbon number range (C 16–C 34). Whilst n-alkan-2-ones were absent in the city and poor in smokes emitted from the torches (from 31 to 42 ng m −3), PAH were present at low extents in all sites (from 18 to 65 ng m −3). The incomplete thermal combustion of torched crude oil was very likely the main source of these particle-bound organic constituents in the city and its surrounding region. 相似文献
15.
Chemical and toxicological profiles were assessed in surface sediments (fraction <63 μm) from the southern North Sea. In extracts of freeze-dried samples, polybrominated biphenyl (PBB), Irgarol 1051 and phthalate concentrations were below the respective detection limits (except di(2-ethylhexyl)phthalate, which was between 170 and 3300 μg kg −1 dry weight (dw)). Hexabromocyclododecane (HBCD) concentrations were between 0.8 and 6.9 μg kg −1 dw, with highest concentrations at river mouths. Polybrominated diphenylethers (PBDE) concentrations were 0.4–0.6 μg kg −1 dw, decabromodiphenylether (BDE209) 1–32 μg kg −1 dw. The ratio BDE209/PCB153 was used as a tracer for recent emissions, and pointed towards a BDE209 source in the Western Scheldt’s upper estuary. PCBs and PAHs were between 0.19–4.7 and 2.6–200 μg kg −1 dw respectively and generally had highest concentrations at near-shore locations and river mouths. Responses in the Microtox broad-spectrum and the Mutatox genotoxicity assays were generally low, with near-shore locations giving higher responses. The umu-C genotoxicity and the ER-CALUX assay for estrogenicity showed no response, with the exception of one near-shore location (IJmuiden outer harbour, ER-CALUX). Highest dioxin-like toxicity (DR-CALUX) was found at near-shore locations, in the outflow of the Rhine/Meuse estuary including a dumping site of harbour sludge. At the Oyster Grounds, DR-CALUX responses appeared to be linked to the occurrence of larger PAHs (4–6 rings). A new, non-destructive clean up procedure resulted in significantly higher DR-CALUX responses than the current protocol. The Dutch legislation on disposal of harbour sludge at sea, dictates the use of the conventional clean up procedure. Our results therefore indicate that probably more dioxin-like toxicity associated with harbour sludge is disposed off at sea than assumed. 相似文献
16.
Air aerosol samples for TSP (total suspended particulate), coarse particulate (particle matter with aerodynamical diameter 2.5–10 μm, PM 2.5–10), fine particulate (particle matter with aerodynamical diameter <2.5 μm, PM 2.5) and metallic elements were collected during March 2004 to January 2005 at TH (Taichung Harbor) in central Taiwan. The seasonal variation average concentration of TSP (total suspended particulate), coarse particulate (particle matter with aerodynamical diameter 2.5–10 μm, PM 2.5–10) and fine particulate (particle matter with aerodynamical diameter <2.5 μm, PM 2.5) were in the range 132–171.1 μg m −3 and 43–49.5 μg m −3, respectively. Seasonal variation of metallic elements Cu, Mn, Zn and Fe in the TSP (total suspended particulate) shows that higher concentration was observed during spring. Seasonal variation of metallic elements Pb, Cr and Mg in the TSP (total suspended particulate) shows that higher concentration was observed during winter. The average metallic element TSP (total suspended particulate) concentration order was Fe > Zn > Mg > Cu > Cr > Mn > Pb in spring. In addition, at the TH sampling site, the average concentration variation of TSP (total suspended particulate) displayed the following order: spring > winter > autumn > summer. However, the average concentration variation of coarse particulate (particle matter with aerodynamical diameter 2.5–10 μm, PM 2.5–10) displayed the following order: spring > winter > summer > autumn. Finally, the average concentration variations of fine particulate (particle matter with aerodynamical diameter <2.5 μm, PM 2.5) were in the following order: winter > spring > summer > autumn at the TH sample site. 相似文献
17.
The residues from the extraction of lead/zinc (Pb/Zn) ores of most Pb/Zn mines are permanently stored in tailings ponds, which require revegetation to reduce their environmental impact. This can only be done if the main constraints on plant establishment are evaluated. This can readily be done by field and greenhouse studies. To test this, the properties of different tailings from Lechang Pb/Zn mine located at the north of Guangdong Province in southern China have been studied. Physical and chemical properties including concentrations of metals (Pb, Zn, Cd and Cu) in the tailings and soils collected from different sites have been measured. The results showed that tailings contain low nitrogen (0.016–0.075%), low-organic matter (0.58–1.78%), high salt (3.55–13.85 dS/m), and high total and diethylene–tetramine–pentaacetic acid (DTPA)-extractable metal concentrations (total: 1019–1642 μg g−1 Pb, 3078–6773 μg g−1 Zn, 8–23 μg g−1 Cd, and 85–192 μg g−1 Cu; DTPA-extractable: 59–178 μg g−1 Pb, 21–200 μg g−1 Zn, 0.30–1.5 μg g−1 Cd, and 4.3–12 μg g−1 Cu). Aqueous extracts of tailings/soils (10%, 20% and 30%, w/v) from different sites were prepared for testing their effects on seed germination and root elongation of a vegetable crop Brassica chinensis and a grass species Cynodon dactylon. It was found that root elongation provided a better evaluation of toxicity than seed germination. The ranking of toxicity using root elongation was: high-sulfur tailings>tailingdam>sparsely vegetated tailings>densely vegetated tailings>mountain soil for both plants. This order was consistent with DTPA-extractable Pb contents in the tailings and soils. B. chinensis seedlings were then grown in the mixtures of different proportions of tailings and farm soil for 4 weeks, and the results (dry weights of seedlings) were in line with the root elongation test. All these demonstrated that heavy metal toxicity, especially available Pb, low content of nutrient, and poor physical structure were major constraints on plant establishment and colonization on the Pb/Zn mine tailings. 相似文献
18.
In this paper, we present two years of seasonal nitric oxide (NO), ammonia (NH 3), and nitrous oxide (N 2O) trace gas fluxes measured in a recovering riparian zone with cattle excluded and adjacent riparian zone grazed by cattle. In the recovering riparian zone, average NO, NH 3, and N 2O fluxes were 5.8, 2.0, and 76.7 ng N m −2 s −1 (1.83, 0.63, and 24.19 kg N ha −1 y −1), respectively. Fluxes in the grazed riparian zone were larger, especially for NO and NH 3, measuring 9.1, 4.3, and 77.6 ng N m −2 s −1 (2.87, 1.35, and 24.50 kg N ha −1 y −1) for NO, NH 3, and N 2O, respectively. On average, N 2O accounted for greater than 85% of total trace gas flux in both the recovering and grazed riparian zones, though N 2O fluxes were highly variable temporally. In the recovering riparian zone, variability in seasonal average fluxes was explained by variability in soil nitrogen (N) concentrations. Nitric oxide flux was positively correlated with soil ammonium (NH 4+) concentration, while N 2O flux was positively correlated with soil nitrate (NO 3−) concentration. Ammonia flux was positively correlated with the ratio of NH 4+ to NO 3−. In the grazed riparian zone, average NH 3 and N 2O fluxes were not correlated with soil temperature, N concentrations, or moisture. This was likely due to high variability in soil microsite conditions related to cattle effects such as compaction and N input. Nitric oxide flux in the grazed riparian zone was positively correlated with soil temperature and NO 3− concentration. Restoration appeared to significantly affect NO flux, which increased ≈600% during the first year following restoration and decreased during the second year to levels encountered at the onset of restoration. By comparing the ratio of total trace gas flux to soil N concentration, we show that the restored riparian zone is likely more efficient than the grazed riparian zone at diverting upper-soil N from the receiving stream to the atmosphere. This is likely due to the recovery of microbiological communities following changes in soil physical characteristics. 相似文献
19.
The combined electrochemical oxidation-solar-light/immobilized TiO 2 film process was conducted to degrade an azo dye, Reactive Black 5 (RB5). The toxicity was also monitored by the Vibrio fischeri light inhibition test. The electrochemical oxidation rapidly decolorized RB5 (55, 110 μM) with a supporting electrolyte of 2 g l −1 NaCl at current density 277 A m −2 and pH 4. However, TOC mineralization and A 310 removal were low. Additionally, the treated solution showed high biotoxicity. RB5 at 110 μM significantly retarded the de-colorization efficiency by using the solar-light/immobilized TiO 2 film process. The combined electrochemical oxidation-solar-light/immobilized TiO 2 process effectively increased the removal of color, A 310, and TOC. The toxicity was also significantly reduced after 3 h of solar irradiation. The results indicated that the low-cost combined process is a potential technique for rapid treatment of RB5. 相似文献
20.
Methane flux from rice varieties grown under two identical soils of Assam were monitored. In the first experiment, variety Jaya and GRT was grown in sandy loam soil of Lower Brahmaputra Valley Zone of Assam and the second experiment was conducted with variety Jyotiprasad and Bishnuprasad in sandy to sandy loam soils of Upper Brahmaputra Valley Zones of Assam. Methane flux recorded from variety Jyotiprasad and GRT was higher compared to variety Bishnuprasad and Jaya. The seasonal integrated flux recorded was 10.76 g m −2, 9.98 g m −2, 9.74 g m −2 and 11.31 g m −2 for variety GRT, Jaya, Bishnuprasad and Jyotiprasad, respectively. All the varieties exhibited two methane peaks one at maximum tillering stage and other at panicle initiation stage of the crop. Crop growth parameters such as leaf number, number of tillers and leaf area index (LAI) showed strong positive relationship with total methane flux. In both the experiments it was calculated that CH 4 emission was substantially influenced by crop phenology and growth. This study emphasise the relationship of different growth parameters with methane emission. 相似文献
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