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1.
This paper reports on cork boiling and bleaching wastewaters treatment by solar photocatalytic processes, TiO2/UV and Fe2+/H2O2/UV (TiO2-only for bleaching wastewater), in a pilot plant with compound parabolic collectors. The photo-Fenton reaction (k = 0.12 L/kJUV, r0 = 59.4 mg/kJUV) is much more efficient that TiO2 photocatalysis and TiO2 + S2O82− (k = 0.0024 L/kJUV, r0 = 1.36 mg/kJUV), leading to 94% mineralization of the bleaching wastewater after 31.5 kJUV/L, consuming 77.1 mM of H2O2 (3.0 mmol/kJUV) and using 20 mg/L of iron. For the cork boiling wastewater, after a slow initial reaction rate, the DOC degradation curve shows a first-order kinetics behaviour (k = 0.015 L/kJUV, r0 = 20.8 mg/kJUV) until 173 kJUV/L (≈300 mg C/L). According to the average oxidation state (AOS), toxicity profiles, respirometry and kinetic results obtained in two solar CPCs plants, the optimal energy dose estimated for phototreatment to reach a biodegradable effluent is 15 kJUV/L and 114 kJUV/L, consuming 33 mM and 151 mM of H2OT:/PGN/ELSEVIER/WR/web/00007490/2, achieving almost 49% and 48% mineralization of the wastewaters, respectively for the cork bleaching and boiling wastewaters. 相似文献
2.
M. Samer C. LoebsinM. Fiedler C. AmmonW. Berg P. SanftlebenR. Brunsch 《Energy and Buildings》2011,43(12):3718-3728
Experiments were performed to study the airflow rates (AFRs) in a naturally ventilated building through four summer seasons and three winter seasons. The AFRs were determined using heat balance (HB), tracer gas technique (TGT) and CO2-balance as averages of the values of all experiments carried out through the different seasons. The statistical analyses were correlation analysis, regression model and t-test. Continuous measurements of gaseous concentrations (NH3, CH4, CO2 and N2O) and temperatures inside and outside the building were performed. The HB showed slightly acceptable results through summer seasons and unsatisfactory results through winter seasons. The CO2-balance showed unexpected high differences to the other methods in some cases. The TGT showed reliable results compared to HB and CO2-balance. The AFRs, subject to TGT, were 0.12 m3 s−1 m−2, 1.15 m3 s−1 cow−1, 0.88 m3 s−1 LU−1, 56 h−1, 395 m3 s−1 and 470 kg s−1 through summer seasons, and 0.08 m3 s−1 m−2, 0.83 m3 s−1 cow−1, 0.64 m3 s−1 LU−1 39 h−1, 275 m3 s−1 and 328 kg s−1 through winter seasons. The AFRs are not independent values, rather they were estimated for specific reference values, which are: area, cow and LU as well as rates. The emission rates through summer seasons, subject to TGT, were 9.4, 40, 3538 and 2.3 g h−1 cow−1; and through winter seasons were 4.8, 19, 2332 and 2.6 g h−1 cow−1, for NH3, CH4, CO2 and N2O, respectively. 相似文献
3.
Lomonte C Doronila A Gregory D Baker AJ Kolev SD 《The Science of the total environment》2011,409(13):2685-2692
Mercury contaminated stockpiles of biosolids (8.4 mg kg− 1 Hg) from Melbourne Water's Western Treatment Plant (MW-WTP) were investigated to evaluate the possibility of their Hg chelate-assisted phytoextraction. The effects of ammonium thiosulphate (NH4)2S2O3, cysteine (Cys), nitrilotriacetic acid (NTA), and potassium iodide (KI) were studied to mobilize Hg and to increase its uptake in plant shoots. Three plant species were selected for this study, one herbaceous and two grasses: Atriplex codonocarpa, Austrodanthonia caespitosa and Vetiveria zizanioides. KI proved to be the best candidate for Hg phytostabilization in biosolids because it facilitated the concentration of this metal mainly in roots. (NH4)2S2O3 was shown to be the most effective chelating agent among those tested for Hg phytoextraction as it allowed the highest translocation of Hg into the above-ground tissues of the selected plant species. The phytoextraction conditions using A. caespitosa as the best performing plant species were optimized at an (NH4)2S2O3 concentration of 27 mmol kg− 1 and contact time with biosolids of seven day. Monitoring of the Hg concentration in biosolids and in leachate water during a 9-day treatment revealed that the biosolids Hg concentration decreased significantly after the first day of treatment and then it decreased only slightly with time reaching a value of 5.6 mg kg− 1 Hg at the end of the 9-day period. From the corresponding results obtained for the leachate water, it was suggested that a relatively large fraction of Hg (0.7 mg kg− 1 Hg) was promptly mobilized and consequently the plants were able to take up the metal and translocate it into shoots. 相似文献
4.
Investigating the potential role of ammonia in ion chemistry of fine particulate matter formation for an urban environment 总被引:3,自引:0,他引:3
To investigate the potential role of ammonia in ion chemistry of PM2.5 aerosol, measurements of PM2.5 (particulate matter having aerodynamic diameter < 2.5 µm) along with its ionic speciation and gaseous pollutants (sulfur dioxide (SO2), nitrogen oxides (NOx), 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 (Fs: 58%) than nitrogen conversion ratio (Fn: 39%) indicated that SO42− was the preferred secondary species to NO3−. The charge balance for the ion chemistry of PM2.5 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 PM2.5 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 PM2.5 and any particulate control strategy should include optimal control of primary precursor gases including ammonia. 相似文献
5.
Struvite crystallisation and recovery using a stainless steel structure as a seed material 总被引:1,自引:0,他引:1
A metallic system acting as a seed substrate has been designed and developed in order to assess its efficiency in recovering phosphorus as struvite. The device, consisting of two concentric stainless steel meshes, was immerged in the upper section of a pilot crystallisation reactor fed with synthetic liquors (MgCl2·6H2O, NH4H2PO4,) for 2 h. Apart from soluble PO4-P removals which remained in the range 79-80% with or without application of the metallic system, it was found that under the specific operating conditions tested the meshes were capable of accumulating struvite at a rate of 7.6 gm−2 h−1, hence reducing significantly the amount of fine particles remaining in solution from 302.2 to 12 mg L−1 when compared to trials without mesh. 相似文献
6.
Nitrate and fluoride contamination in groundwater of an intensively managed agroecosystem: A functional relationship 总被引:3,自引:0,他引:3
Manik Chandra Kundu Biswapati Mandal Gora Chand Hazra 《The Science of the total environment》2009,407(8):2771-2782
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. 相似文献
7.
Enhanced nitrogen and phosphorus removal from eutrophic lake water by Ipomoea aquatica with low-energy ion implantation 总被引:1,自引:0,他引:1
Ipomoea aquatica with low-energy N+ ion implantation was used for the removal of both nitrogen and phosphorus from the eutrophic Chaohu Lake, China. The biomass growth, nitrate reductase and peroxidase activities of the implanted I. aquatica were found to be higher than those of I. aquatica without ion implantation. Higher NO3-N and PO4-P removal efficiencies were obtained for the I. aquatica irradiation at 25 keV, 3.9 × 1016 N+ ions/cm2 and 20 keV 5.2 × 1016 N+ ions/cm2, respectively (p < 0.05). Moreover, the nitrogen and phosphorus contents in the plant biomass with ion implantation were also greater than those of the controls. I. aquatica with ion implantation was directly responsible for 51-68% N removal and 54-71% P removal in the three experiments. The results further confirm that the ion implantation could enhance the growth potential of I. aquatica in real eutrophic water and increase its nutrient removal efficiency. Thus, the low-energy ion implantation for aquatic plants could be considered as an approach for in situ phytoremediation and bioremediation of eutrophic waters. 相似文献
8.
Phosphate removal in agro-industry: Pilot- and full-scale operational considerations of struvite crystallization 总被引:1,自引:0,他引:1
Wim Moerman Marta Carballa Andy Vandekerckhove Dirk Derycke Willy Verstraete 《Water research》2009,43(7):1887-1892
Pilot-scale struvite crystallization tests using anaerobic effluent from potato processing industries were performed at three different plants. Two plants (P1 & P2) showed high phosphate removal efficiencies, 89 ± 3% and 75 ± 8%, resulting in final effluent levels of 12 ± 3 mg PO43−-P L−1 and 11 ± 3 mg PO43−-P L−1, respectively. In contrast, poor phosphate removal (19 ± 8%) was obtained at the third location (P3). Further investigations at P3 showed the negative effect of high Ca2+/PO43−-P molar ratio (ca. 1.25 ± 0.11) on struvite formation. A full-scale struvite plant treating anaerobic effluent from a dairy industry showed the same Ca2+ interference. A shift in the influent Ca2+/PO43−-P molar ratio from 2.69 to 1.36 resulted in average total phosphorus removal of 78 ± 7%, corresponding with effluent levels of 14 ± 4 mg Ptotal L−1 (9 ± 3 mg PO43−-P L−1). Under these conditions high quality spherical struvite crystals of 2-6 mm were produced. 相似文献
9.
The atmospheric fluxes of N2O, CH4 and CO2 from the soil in four mangrove swamps in Shenzhen and Hong Kong, South China were investigated in the summer of 2008. The fluxes ranged from 0.14 to 23.83 μmol m−2 h−1, 11.9 to 5168.6 μmol m−2 h−1 and 0.69 to 20.56 mmol m−2 h−1 for N2O, CH4 and CO2, respectively. Futian mangrove swamp in Shenzhen had the highest greenhouse gas fluxes, followed by Mai Po mangrove in Hong Kong. Sha Kong Tsuen and Yung Shue O mangroves in Hong Kong had similar, low fluxes. The differences in both N2O and CH4 fluxes among different tidal positions, the landward, seaward and bare mudflat, in each swamp were insignificant. The N2O and CO2 fluxes were positively correlated with the soil organic carbon, total nitrogen, total phosphate, total iron and NH4+-N contents, as well as the soil porosity. However, only soil NH4+-N concentration had significant effects on CH4 fluxes. 相似文献
10.
Fluctuation analysis-based risk assessment for respiratory virus activity and air pollution associated asthma incidence 总被引:1,自引:0,他引:1
Asthma is a growing epidemic worldwide. Exacerbations of asthma have been associated with bacterial and viral respiratory tract infections and air pollution. We correlated the asthma admission rates with fluctuations in respiratory virus activity and traffic-related air pollution, namely particulate matter with an aerodynamic diameter ≤ 10 μm (PM10), nitrogen dioxide (NO2), carbon monoxide (CO), sulfur dioxide (SO2), and ozone (O3). A probabilistic risk assessment framework was developed based on a detrended fluctuation analysis to predict future respiratory virus and air pollutant associated asthma incidence. Results indicated a strong association between asthma admission rate and influenza (r = 0.80, p < 0.05) and SO2 level (r = 0.73, p < 0.05) in Taiwan in the period 2001-2008. No significant correlation was found for asthma admission and PM10, O3, NO2, and CO. The proposed fluctuation analysis provides a simple correlation exponent describing the complex interactions of respiratory viruses and air pollutants with asthma. This study revealed that there was a 95% probability of having exceeded 2987 asthma admissions per 100,000 population. It was unlikely (30% probability) that the asthma admission rate exceeded 3492 per 100,000 population. The probability of asthma admission risk can be limited to below 50% by keeping the correlation exponent of influenza to below 0.9. We concluded that fluctuation analysis based risk assessment provides a novel predictor of asthma incidence. 相似文献
11.
Mary Ann Rempel Hector DeHaro Yinsheng Wang 《The Science of the total environment》2009,407(7):2209-2215
Oxidative compounds have been demonstrated to decrease the fertilization capability and viability of offspring of treated spermatozoa. As estrogen and its hydroxylated metabolites readily undergo redox cycling, this study was undertaken to determine if estrogens and other oxidants could damage DNA and impair sperm function. Sperm was preexposed to either 17β-estradiol (E2), 4-hydroxyestradiol (4OHE2) or the oxidant t-butyl hydroperoxide (t-BOOH), and allowed to fertilize untreated eggs. The fertilization rates and development of the larvae were assessed, as well as the amount of 8-oxodeoxyguanosine (8-oxodG) as an indication of oxidative DNA damage. All compounds caused significant decreases in fertilization and increases in pathological abnormalities in offspring, with 4OHE2 being the most toxic. Treatment with 4OHE2 caused a significant increase of 8-oxodG, but E2 failed to show any effect. Pathological abnormalities were significantly correlated (r2 = 0.44, p ≤ 0.05) with 8-oxodG levels in sperm treated with t-BOOH and 4OHE2, but not E2. 8-OxodG levels also were somewhat weakly correlated with impaired fertilization in 4OHE2-treated sperm (r2 = 0.33, p ≤ 0.05). The results indicate that biotransformation of E2 to 4OHE2 enhances oxidative damage of DNA in sperm, which can reduce fertilization and impair embryonic development, but other mechanisms of action may also contribute to these effects. 相似文献
12.
Jeongwon Kang Byung Cheol Cho Chang-Bok Lee 《The Science of the total environment》2010,408(11):2369-509
Atmospheric deposition of different types of aerosols over the southern East Sea has received little attention in terms of seawater biogeochemistry. We investigated the concentrations of water-soluble ions (NO3−, NH4+ and nss-SO42−) in the aerosols associated with air mass transport patterns arriving at the east coast of Korea, adjacent to the southern East Sea, in order to determine source regions affecting chemical composition of aerosols and to assess the atmospheric pathway as a significant controlling mechanism of the biogeochemistry in this marginal sea. Concentrations of certain elements (Al, Na, Ca, V, Zn and Pb) together with the water-soluble ions were measured in the aerosol samples (n = 34) collected during the period March 2002-February 2003. The geometric mean concentrations of the water-soluble ions were NO3− 2.98 (0.56-16.22), NH4+ 1.42 (0.37-6.73) and nss-SO42− 2.47 (0.17-17.35) μg m− 3. The backward trajectories revealed that air masses passing slowly over eastern China contributed more to increases in the concentrations of water-soluble ions than those associated with fast-moving northwesterly and maritime winds. Therefore, the correlation between the NH4+ and NO3+ concentrations increased, suggesting that gas-phase NH3 and HNO3 was forming fine-mode NH4NO3. The atmospheric N input accounted for ∼ 10% of new production over the southern East Sea on an annual scale, while it accounted for over ∼ 25% of new production during the water column stratification seasons (summer and early fall). 相似文献
13.
A number of environmental factors have been shown to influence the dynamics of Hg in aquatic ecosystems. Here we investigate the influence of fish size, pH, dissolved organic carbon (DOC), and the availability of potential methylation sites (floodplain forests and hydromorphic soils) on the concentration of total Hg in two carnivorous fishes: Cichla spp. and Hoplias malabaricus in the Negro River, Brazil. Fish and water samples for chemical analysis were collected from 33 sites in the Negro basin. The percentage of alluvial floodplains and hydromorphic soils (potential methylation sites) in the drainage basin upstream from each sampling point was estimated from radar imagery and existing soil maps with GIS. The average of Hg concentrations were 0.337 ppm (SD = 0.244) in Cichla spp. and 0.350 ppm (SD = 0.250) in H. malabaricus. Although the study area was geographically isolated from most major anthropogenic Hg sources, over 18% of Cichla spp. and 29% of H. malabaricus had Hg concentrations above 0.5 ppm, indicating naturally high background levels of Hg. Hg concentrations increased with size in both Cichla spp. (r2 = 0.664, p = 0.000) and H. malabaricus (r2 = 0.299, p = 0.000). Hg concentrations in H. malabaricus also increased with percent floodable area (p = 0.006), pH (p = 0.000) and DOC (0,063). In Cichla spp, Hg increased only in relation to percent floodable area (p = 0.000). Hydromorphic soils did not influence fish Hg. 相似文献
14.
Aromatic amines such as aniline and its derivatives are an important class of environmental water pollutants. A method based on capillary zone electrophoresis with amperometric detection (CZE-AD) at carbon disk electrode was developed for the determination of aromatic amines in water samples. The effects of working potential, pH and concentration of running buffer, separation voltage and injection time were investigated. Under the optimum conditions, 2,3-diaminonaphthalene, aniline, o-phenylenediamine and p-chloroaniline could be separated in 0.16 mol/L Na2HPO4-citric acid buffer (pH 4.6) within 23 min. The detection limits of them were 1.0 × 10−7, 3.3 × 10−8, 5.0 × 10−8, and 1.3 × 10−7 mol/L (S/N = 3), respectively. The method can be applied directly for the determination of aromatic amines in real water samples with satisfactory results. 相似文献
15.
The degradation of 15 emerging contaminants (ECs) at low concentrations in simulated and real effluent of municipal wastewater treatment plant with photo-Fenton at unchanged pH and Fe = 5 mg L−1 in a pilot-scale solar CPC reactor was studied. The degradation of those 15 compounds (Acetaminophen, Antipyrine, Atrazine, Caffeine, Carbamazepine, Diclofenac, Flumequine, Hydroxybiphenyl, Ibuprofen, Isoproturon, Ketorolac, Ofloxacin, Progesterone, Sulfamethoxazole and Triclosan), each with an initial concentration of 100 μg L−1, was found to depend on the presence of CO32− and HCO3− (hydroxyl radicals scavengers) and on the type of water (simulated water, simulated effluent wastewater and real effluent wastewater), but is relatively independent of pH, the type of acid used for release of hydroxyl radicals scavengers and the initial H2O2 concentration used. Toxicity tests with Vibrio fisheri showed that degradation of the compounds in real effluent wastewater led to toxicity increase. 相似文献
16.
Comparison of the microbiological and chemical characterization of harvested rainwater and reservoir water as alternative water resources 总被引:1,自引:0,他引:1
Rainwater harvesting (RWH) offers considerable potential as an alternative water supply. In this study, all of the harvested rainwater samples met the requirements for grey water but not for drinking water. In terms of microbiological parameters, total coliform (TC) and Escherichia coli (EC) were measured in 91.6% and 72%, respectively, of harvested rainwater samples at levels exceeding the guidelines for drinking water, consistent with rainfall events. In the case of the reservoir water samples, TC and EC were detected in 94.4% and 85.2%, respectively, of the samples at levels exceeding the guidelines for drinking water. Both indicators gradually increased in summer and fall. The highest median values of both TC and EC were detected during the fall. Chemical parameters such as common anions and major cations as well as metal ions in harvested rainwater were within the acceptable ranges for drinking water. By contrast, Al shows a notable increase to over 200 μg L− 1 in the spring due to the intense periodic dust storms that can pass over the Gobi Desert in northern China. In terms of statistical analysis, the harvested rainwater quality showed that TC and EC exhibit high positive correlations with NO3− (ρTC = 0.786 and ρEC = 0.42) and PO4− (ρTC = 0.646 and ρEC = 0.653), which originally derive from catchment contamination, but strong negative correlations with Cl− (ρTC = − 0.688 and ρEC = − 0.484) and Na+ (ρTC = − 0.469 and ρEC = − 0.418), which originate from seawater. 相似文献
17.
D.R. Smith 《The Science of the total environment》2009,407(12):3883-3889
The intensive agricultural systems in the Midwestern United States can enrich surface waters with nutrients. Agricultural drainage ditches serve as the first and second order streams throughout much of this region, as well as other highly productive agricultural areas in humid regions throughout the world. This project was conducted to evaluate in-stream processing of soluble P (SP) in agricultural drainage ditches. Soluble P injection studies were conducted at seven sites along three drainage ditches (298 to 4300 ha drainage area), and one site on a third-order stream that receives the discharge from the agricultural ditches (19,000 ha drainage area) by increasing the SP concentration in the ditch water by approximately 0.25 mg L− 1. Sediments collected from smaller watersheds contained greater amounts of Mehlich 3 and exchangeable P (ExP), silt and clay size particles, and organic matter. Phosphorus uptake lengths (Snet) ranged from 40 to 1900 m, and SP uptake rates (U) ranged from 0.4 to 52 mg m− 2 h− 1. Phosphorus Snet was correlated with ditch geomorphological (i.e. width) and sediment properties (i.e. organic matter, ExP, and equilibrium P concentration; r2 = 1.00, P < 0.001), indirect drainage in the watershed (r2 = 0.92, P < 0.001), and the amount of small grains, forest, urban area, alfalfa and corn (r2 = 1.00, P < 0.0001). Agricultural drainage ditches actively process nutrients and could potentially be managed to optimize this processing to minimize SP export from these landscapes. 相似文献
18.
Nitrifier characteristics in submerged membrane bioreactors under different sludge retention times 总被引:3,自引:0,他引:3
Tao Yu 《Water research》2010,44(9):2823-2830
Three submerged membrane bioreactors (MBRs) were operated continuously for 230 days by feeding with synthetic inorganic wastewater (NH4+-N, 100 mg L−1) under different solids retention times (SRTs. M30d, 30 days; M90d, 90 days; Minfinite, no sludge purge) to examine the influence of SRT on nitrification performance and microbial characteristics. All the reactors could oxidize NH4+-N to NO3−-N effectively without accumulation of NO2−-N. M30d with the shortest SRT showed significantly higher specific ammonium oxidizing rate (SAOR, 0.22 kg NH4+-N kg−1 MLSS day−1) and specific nitrate forming rate (SNFR, 0.13 kg NO3−-N kg−1 MLSS day−1) than the other two MBRs (0.12-0.14 kg NO3−-N kg−1 MLSS day−1 and 0.042-0.068 kg NO3−-N kg−1 MLSS day−1, respectively). Short SRT led to low extracellular polymeric substances (EPS) concentration and long operating cycle. The nitrite oxidizing bacteria (NOB) ratios by both the fluorescence in situ hybridization (FISH) (3.6% for M30d and 2.1-2.2% for M90d and Minfinite) and MPN (1.4 × 107 cells g−1 MLSS for M30d and 6.2 × 105 and 2.7 × 104 cells g−1 MLSS for M90d and Minfinite) analyses showed that M30d favored the accumulation of NOB, which was in accordance with the SNFR result. However, the ammonia oxidizing bacteria (AOB) ratios (3.5%, 3.2% and 4.9% for M30d, M90d and Minfinite) were not in accordance with the SAOR result. PCR-DGGE, clone library and FISH results showed that the fast-growing Nitrosomonas and Nitrobacter sp. were the dominant AOB and NOB, respectively for M30d, while considerable slow-growing Nitrosospira and Nitrospira sp. existed in Minfinite, which might be an important reason why Minfinite had a low SAOR and SNFR. 相似文献
19.
R. Brad Mills Tamar Bodek Jules M. Blais 《The Science of the total environment》2009,407(16):4696-4702
The concentration of methylmercury (MeHg) in aquatic ecosystems is the net result of the highly dynamic abiotic and biotic processes of mercury methylation and demethylation. In this study, we conduct an examination of the net fluvial loading of methylmercury (MeHgNet = MeHgWatershed − MeHgLake outflow) across a 3 year time frame in both a dystrophic lake and an oligotrophic lake. A significant portion of MeHgNet variance in both lakes could be attributed to a seasonal pattern (11.4%, p = 0.009; oligotrophic, and 27.0%, p < 0.0001; dystrophic) which in both cases, was most correlated with air temperature. The dystrophic lake appeared to be a net source of methylmercury (MeHgNet = − 1.9 ± 0.3 mg MeHg d− 1) while the oligotrophic lake appeared to be a net sink (MeHgNet = 0.4 ± 0.2 mg MeHg d− 1), indicating that there was net methylation in the dystrophic lake and net demethylation in the oligotrophic lake. Higher MeHg loading to the lakes occurred during the summer and between seasons there was a difference in MeHgNet of 1.1 ±0.3 mg MeHg d− 1 and 3.1 ± 0.6 mg MeHg d− 1. Seasonal patterns of MeHgNet in the oligotrophic lake lagged behind the dystrophic lake by 39 days. The short term variation in MeHgNet was dominated by precipitation (t = 2.73, p = 0.008; dystrophic, t = 2.53, p = 0.017; oligotrophic). 相似文献
20.
F. Fernández-Luqueño C. Martínez-Suárez J. Méndez-Bautista F. López-Valdez M.L. Luna-Guido 《The Science of the total environment》2009,407(14):4289-4296
Addition of different forms of nitrogen fertilizer to cultivated soil is known to affect carbon dioxide (CO2) and nitrous oxide (N2O) emissions. In this study, the effect of urea, wastewater sludge and vermicompost on emissions of CO2 and N2O in soil cultivated with bean was investigated. Beans were cultivated in the greenhouse in three consecutive experiments, fertilized with or without wastewater sludge at two application rates (33 and 55 Mg fresh wastewater sludge ha− 1, i.e. 48 and 80 kg N ha− 1 considering a N mineralization rate of 40%), vermicompost derived from the wastewater sludge (212 Mg ha− 1, i.e. 80 kg N ha− 1) or urea (170 kg ha− 1, i.e. 80 kg N ha− 1), while pH, electrolytic conductivity (EC), inorganic nitrogen and CO2 and N2O emissions were monitored. Vermicompost added to soil increased EC at onset of the experiment, but thereafter values were similar to the other treatments. Most of the NO3− was taken up by the plants, although some was leached from the upper to the lower soil layer. CO2 emission was 375 C kg ha− 1 y− 1 in the unamended soil, 340 kg C ha− 1 y− 1 in the urea-amended soil and 839 kg ha− 1 y− 1 in the vermicompost-amended soil. N2O emission was 2.92 kg N ha− 1 y− 1 in soil amended with 55 Mg wastewater sludge ha− 1, but only 0.03 kg N ha− 1 y− 1 in the unamended soil. The emission of CO2 was affected by the phenological stage of the plant while organic fertilizer increased the CO2 and N2O emission, and the yield per plant. Environmental and economic implications must to be considered to decide how many, how often and what kind of organic fertilizer could be used to increase yields, while limiting soil deterioration and greenhouse gas emissions. 相似文献