共查询到20条相似文献,搜索用时 843 毫秒
1.
The aerobic and anaerobic degradation of phenol and selected chlorophenols was examined in a clay loam soil containing no added nutrients. A simple, efficient procedure based on the high solubility of these compounds in 95% ethanol was developed for extracting phenol and chlorophenol residues from soil. Analysis of soil extracts with UV spectrophotometry showed that phenol,o-chlorophenol,p-chlorophenol, 2,4-dichlorophenol, 2,6-dichlorophenol and 2,4,6-trichlorophenol were rapidly degraded, whilem-chlorophenol, 3,4-dichlorophenol, 2,4,5-trichlorophenol and pentachlorophenol were degraded very slowly by microorganisms in aerobically-incubated soil at 23°C. Both 3,4,5-trichlorophenol and 2,3,4,5-tetra chlorophenol appeared to be more resistant to degradation by aerobic soil microorganisms at 23°C. None of the compounds examined were degraded by microorganisms in anaerobically-incubated soil at 23°C. Direct microscopic observation revealed that phenol and selected chlorophenols stimulated aerobic and to a lesser extent, anaerobic microbial growth in soil, and aerobic soil bacteria were responsible for the degradation of 2,4-dichlorophenol in aerobically-incubated soil at 23°C. Phenol,o-chlorophenol,m-chlorophenol,p-chlorophenol and 2,4-dichlorophenol underwent rapid non-biological degradation in sterile silica sand. Non-biological decomposition contributed, perhaps substantially, to the removal of some chlorophenols from sterile aerobically-incubated soil and both sterile and non-sterile anaerobically-incubated soil. 相似文献
2.
Experiments were carried out to study the transformation of 14C-ring-labeled 2,4-D and the two related chlorophenols 4-chlorophenol (4-CP) and 2,4-dichlorophenol (4-DCP) during straw composting
under controlled laboratory conditions. Incubation under sterile and nonsterile conditions was done to evaluate the relative
importance of the biotic and abiotic processes. Pre-composted straw was treated with the three chemicals. The availability
of the different chemicals was monitored during incubations as well as their degradation. Under nonsterile conditions, the
mineralization of both chlorophenols reached 20% of the applied compounds, whereas it was 52% for 2,4-D. Transitory water-soluble
metabolites of 2,4-D and chlorophenols were formed but they disappeared rapidly. After 21 days, 21% of the 2,4-D and 38% of
the 2,4-DCP was stabilized as nonextractable (bound) residues under nonsterile conditions. Bound residues of both chemicals
were negligible under sterile conditions. Availability of chemicals as estimated by water extraction decreased during incubation
proportionally to mineralization and to the formation of bound residues. The increase in immobilization of the chemical residues
was stronger under nonsterile conditions than under sterile conditions. Under nonsterile conditions 71% of the 4-CP was recovered
as bound residues, whereas under sterile conditions 30% of the applied 4-CP formed bound residues after formaldehyde addition
and only 8% with autoclaved straw. Global microbial activity decreased in the presence of the chlorophenols probably due to
their toxic effect. These data indicate that the biological activity associated with straw transformation during composting
stimulates the depletion of 2,4-D and chlorophenols by mineralization and by formation of bound residues.
Received: 6 September 1996 相似文献
3.
This study examined a comparative degradation of various chlorinated phenolic compounds including phenol, 4-chlorophenol (4-CP), 2,6-dichlorophenol (2,6-DCP), 2,4,6-trichlorophenol (2,4,6-TCP), 2,3,4,6-tetrachlorophenol (2,3,4,6-TeCP), and pentachlorophenol (PCP) using 28, 580, and 1,000 kHz ultrasonic reactors. The concentration of hydrogen peroxide was also determined in order to investigate the efficacy of different sonochemical reactors for hydroxyl radical production. Clearly, it was observed that the 580 kHz sonochemical reactor had maximum efficacy for hydroxyl radical production. The degradation of all the compounds followed the order; 580 kHz (91?C93%) > 1,000 kHz (84?C86%) > 28 kHz (17?C34%) with an initial concentration of 2.5 mg L?1 at a reaction time of 40 min with ultrasonic power of 200 ± 3 W and aqueous temperature of 20 ± 1°C in each experiment. Overall, the degradation of those phenolic compounds followed the order, PCP > 2,3,4,6-TeCP > 2,4,6-TCP > 2,6-DCP > 4-CP > phenol at various frequencies in the presence/absence of a radical scavenger (tert-butyl alcohol). It was revealed that the correlations between the compound degradation rates and the physicochemical parameters, R 2 = 0.99 for octanol?Cwater partition coefficient, R 2 = 0.95 for water solubility, R 2 = 0.94 for vapor pressure, and R 2 = 0.88 for Henry??s law constant, excluding PCP, were very good in the entire range of each parameter. 相似文献
4.
Microcosm studies were employed to determine the subsurface biodegradation rates of phenol, 2-chlorophenol (2-CP), 2,4-dichlorophenol (2,4-DCP), 2,4,6-trichlorophenol (2,4,6-TCP), and pentachlorophenol (PCP). Soil samples were taken from sites in Pennsylvania and Virginia from depths up to 31 m, and all samples contained significant microbial populations. Soil from both sites readily biodegraded all five compounds. Biodegradation rates increased as initial concentrations increased, and all biodegradation rates appeared to follow first-order kinetics with regard to the initial compound concentrations. Biodegradation rates for the five compounds followed the order: phenol = 2-CP > 2,4,6-TCP > 2,4-DCP. PCP was degraded more slowly than phenol or 2-CP, but similarly to 2,4,6-TCP and 2,4-DCP. Different soils exhibited different degradation rates, and the soil characteristics that may influence the rates are discussed. The data suggest that biological degradation is a significant attenuation mechanism for phenol and its chlorinated derivatives in subsurfaces saturated and unsaturated zones. 相似文献
5.
The photochemical degradation of two widely used organophosphorothioate insecticides, fenitrothion and diazinon, was investigated
in aqueous solutions containing three separate dissolved constituents commonly found in natural waters (NO3−, CO32− and dissolved organic matter (DOC)). The effect of these constituents on pesticide photodegradation was compared to degradation
in “constituent-free” pure water. Solutions were irradiated in an Atlas solar simulator fitted with a UV-filtered Xenon arc
lamp with light irradiances (500 W m−2) measured using a spectral radiometer to allow derivation of quantum yields of degradation. Fenitrothion absorbs light within
the solar UV range (λ, 295–400 nm) and underwent direct photolysis in pure water whereas diazinon (λ
max ∼250 nm) showed no observable loss over the experimental period. However, photodegradation conforming to pseudo-first-order
kinetics was observed for both chemicals in the presence of the dissolved constituents (at concentrations typically observed
in natural waters), with the rates of photodecay observed in the order of NO3− > CO32− ≅ DOC, with the highest rates observed in the 3 mM NO3− solutions (k
Fen = 0.155 ± 0.041 h−1; k
Dia = 0.084 ± 0.0007 h−1). For diazinon this rate was comparable to fenitrothion photolysis in pure water (k
fen 0.072 ± 0.0078 h−1), highlighting the importance of NO3− on a non-photolabile pesticide, with indirect photodegradation probably attributable to the light-induced release of aqueous
hydroxyl radicals (·OH) from NO3−. Suwannee river fulvic acid (serving as DOC) did not statistically affect the rate of photodecay for fenitrothion relative
to its photolysis in MilliQ water, although measured rates in DOC solutions were slightly lower. However, measurable rates
of photodecay were apparent for diazinon in the DOC solutions, indicating that fulvic acid, possibly in the form of “excited”
triplet-state-DOC plays a role in diazinon transformation. Hydrolysis was not apparent for fenitrothion (in buffered solutions
of pH 5–9) but was notable for diazinon at the lower pHs of 5 and 3 (k
Dia-hyd 0.3414 h−1 at pH 3 and 0.228 h−1 at pH 5), resulting in the formation of the degradate, 2-isopropyl–6-methyl–4-pyrimidinol. This work highlights the importance
of dissolved constituents on abiotic photodegradation of pesticides and it is recommended that these constituents be incorporated
into laboratory-based fate-testing regimes. 相似文献
6.
Groundwater drains used to manage saline watertables in the semi-arid zone of south-western Australia can discharge acidic
saline water with high concentrations of metals to waterways. Mitigating the acidity impacts of the waters requires sulfate-reducing
bioreactors capable of functioning under semi-arid conditions with limited source materials. Two simple pilot-scale bioreactor
designs using straw and sheep manure mixtures were evaluated over several years. The bioreactors increased pH from <3.5 to
>5.5 for 125–260 days, with concurrent evidence of sulfate reduction, >85% reductions in net acidity and >90% reductions in
Al and most trace elements (e.g. Pb, Cu, Ni, Zn, Ce and La). When outflow pH < 5.5 (remaining greater than inflows), reduction
in net acidity was 10–80% but concentrations of Pb, Cu and Ni remained >80% reduced over periods of 250 to >700 days. Rates
of alkalinity generation initially exceeded 10 g CaCO3/m2/day in both bioreactors thereafter decreasing to >1–2 CaCO3/m2/day. Al and Fe retention was implicated in trace metal removal when pH < 5.5, mediated by biological alkalinity generation.
High evaporation rates limited bioreactor function by restricting outflows with no benefits to alkalinity generation rates.
This experiment showed that simple bioreactors can neutralise acidic waters and remove metals for short durations and show
capacity for sustained reduction in acidity and metal concentrations over several years despite low alkalinity generation. 相似文献
7.
Pascal-Lorber S Despoux S Rathahao E Canlet C Debrauwer L Laurent F 《Journal of agricultural and food chemistry》2008,56(18):8461-8469
Chlorophenols are potentially harmful pollutants that are found in numerous natural and agricultural systems. Plants are a sink for xenobiotics, which occur either intentionally or not, as they are unable to eliminate them although they generally metabolize them into less toxic compounds. The metabolic fate of [ (14)C] 4-chlorophenol (4-CP), [ (14)C] 2,4-dichlorophenol (2,4-DCP), and [ (14)C] 2,4,5-trichlorophenol (2,4,5-TCP) was investigated in lettuce, spinach, and radish to locate putative toxic metabolites that could become bioavailable to food chains. Radish plants were grown on sand for four weeks before roots were dipped in a solution of radiolabeled chlorophenol. The leaves of six-week old lettuce and spinach were treated. Three weeks after treatments, metabolites from edible plant parts were extracted and analyzed by high performance liquid chromatography (HPLC) and characterized by mass spectrometry (MS), and nuclear magnetic resonance spectroscopy (NMR). Characterization of compounds highlighted the presence of complex glycosides. Upon hydrolysis in the digestive tract of animals or humans, these conjugates could return to the toxic parent compound, and this should be kept in mind for registration studies. 相似文献
8.
Components of organic phosphorus in soil extracts that are hydrolysed by phytase and acid phosphatase 总被引:8,自引:0,他引:8
Extracts were prepared from soil using water, 50 mM citric acid (pH ∼2.3) or 0.5 M NaHCO3 (pH 8.5), and were incubated with excess phytase from Aspergillus niger to determine the amounts of labile P. Two A. niger phytase preparations were used: (1) a purified form which exhibited a narrow substrate specificity and high specific activity
against phytate; and (2) a commercial preparation (Sigma) with activity against a broad range of P compounds. A comparatively
large proportion (up to 79%, or 5.7 μg g–1 soil) of the organic P (Po) extracted with citric acid was hydrolysed by the commercial phytase, while between 28% and 40% (up to 3.1 μg g–1 soil) was hydrolysed using purified phytase. By comparison, only small quantities of the Po in water and NaHCO3 soil extracts were enzyme labile. While extractable Po was increased both with increasing concentrations of citric acid (up to 50 mM) and increasing pH (pH 2.3–6.0), enzyme-labile
P increased only with citric acid concentration. The labile component of Po in citric acid extracts from soils with contrasting fertiliser histories indicated that enzyme-labile Po is a relatively large soil P pool and is potentially an important source of P for plants.
Received: 29 October 1999 相似文献
9.
Jae-Woo Choi Seung-Gun Chung Kie-Yong Cho Kyung-Youl Baek Seok-Won Hong Dong-Ju Kim Sang-Hyup Lee 《Water, air, and soil pollution》2012,223(3):1437-1441
This study investigated the encapsulation and photocatalysis of chlorophenol compounds in water using porphyrin-(polystyrene-b-2-dimethylaminoethyl acrylate) star polymer. The chloride ions generated during photocatalytic process were identified and
quantified. 2,4,6-Trichlorophenol, pentachlorophenol, and 2,4-dichlorophenol were satisfactorily decomposed in the photoreactor
using porphyrin-(polystyrene-b-2-dimethylaminoethyl acrylate) star polymer, with removal efficiencies of 2,454, 498, and 760 mg/g of porphyrin-(polystyrene-b-2-dimethylaminoethyl acrylate) star polymer. The half-life times reached around 30 min, with the exception of that for 2,4-dichlorophenol.
The star polymer-impregnated porphyrin is a promising photocatalyst for the removal of chlorophenols. 相似文献
10.
Daria Juretic Jelena Puric Hrvoje Kusic Vedrana Marin Ana Loncaric Bozic 《Water, air, and soil pollution》2014,225(10):1-18
The influence of structure on degradation of five halogenated phenols (XPs) by UV/H2O2 process was investigated. The combined influence of type or number of substituents and UV/H2O2 process parameters (pH and [H2O2]) on the degradation kinetics of 2-fluorophenol (2-FP), 2-chlorophenol (2-CP), 2-bromophenol (2-BP), 2,4-dichlorophenol (2,4-DCP), and 2,4,6-trichlorophenol (2,4,6-TCP) was studied using modified miscellaneous 33 full factorial design and response surface modeling (RSM). Studied XPs obey first-order degradation kinetics within the investigated range of process parameters. Determined degradation rate constants (k obs) were correlated with process and structural parameters by the quadratic polynomial models. Analysis of variance (ANOVA) demonstrated RSM models’ accuracy and showed that, in addition to pH and [H2O2], model terms related with the pollutant structure are highly influential. k obs of mono-XPs follow the decreasing order 2-FP, 2-CP, and 2-BP, while CPs follow the decreasing order 2-CP, 2,4-DCP, and 2,4,6-TCP. Biodegradability (biochemical oxygen demand (BOD)5/chemical oxygen demand (COD)) and toxicity (TU) were evaluated prior to the treatment and at the reference time intervals. The observed differences are correlated with the structural characteristics of studied XPs. 相似文献
11.
This study was conducted to investigate the effect of inorganic nitrogen (N) and root carbon (C) addition on decomposition
of organic matter (OM). Soil was incubated for 200 days with nine treatments (three levels of N (no addition (N0) = 0, low
N (NL) = 0.021, high N (NH) = 0.083 mg N g−1 soil) × three levels of C (no addition (C0) = 0, low C (CL) = 5, high C (CH) = 10 mg root g−1 soil)). The carbon dioxide (CO2) efflux rates, inorganic N concentration, pH, and potential activities of β-glucosidase and oxidative enzyme were measured
during incubation. At the beginning and the end of incubation, the native soil organic carbon (SOC) and root-derived SOC were
quantified by using a natural labeling technique based on the differences in δ
13C between C3 and C4 plants. Overall, the interaction between C and N was not significant. The decomposition of OM in the NH
treatment decreased. This could be attributed to the formation of recalcitrant OM by N because the potentially mineralizable
C pool was significantly lower in the NH treatment (3.1 mg C g−1) than in the N0 treatment (3.6 mg C g−1). In root C addition treatments, the CO2 efflux rate was generally in order of CH > CL > C0 over the incubation period. Despite no differences in the total SOC concentration
among C treatments, the native SOC in the CH treatment (18.29 mg C g−1) was significantly lower than that in the C0 treatment (19.16 mg C g−1). 相似文献
12.
Alok Kalra Mahesh Chandra Ashutosh Awasthi Anil K. Singh Suman Preet S. Khanuja 《Biology and Fertility of Soils》2010,46(5):521-524
The present study demonstrates the usefulness of natural microbial growth-promoting compounds for improving the stability
and life of vermicompost-based (both granular and its aqueous extract) bioformulations. Granular vermicompost maintained the
number of cells of Rhizobium meliloti Rmd 201 up to 5.9 × 108 after 180 days at 28°C compared with 2.1 × 108 in charcoal (powdered), while aqueous extract of the vermicompost supported the 5.6 × 107 rhizobia numbers even after 270 days. The addition of 25 μL/mL cow urine and 0.01 mM calliterpinone, a natural plant growth
promoter, increased the rhizobia number significantly in granular vermicompost and its aqueous extract, respectively. 相似文献
13.
Denitrification plays an important role in N-cycling. However, information on the rates of denitrification from horticultural
growing media is rare in literature. In this study, the effects of pH, N, C, and moisture contents on denitrification were
investigated using four moderately decomposed peat types (oligotrophic, mesotrophic, eutrophic, and transitional). Basal and potential denitrification rates (20°C, 18 h) from the unlimed peat samples varied widely from 2.0 to 21.8 and
from 118.9 to 306.6 μg (N2O + N2)–N L−1 dry peat h−1, respectively, with the highest rates from the eutrophic peat and the lowest from the transitional one. Both basal and potential
denitrification rates were substantially increased by 3.6–14- and 1.4–2.3-fold, respectively, when the initial pH (4.3–4.8)
was raised to 5.9–6.5 units. Emissions of (N2O + N2)–N from oligotrophic, mesotrophic, and transitional peats were markedly increased by the addition of 0.15 g NO3–N L−1 dry peat but further additions had no effect. Denitrification rates were increased by increasing glucose concentration suggesting
that the activity of denitrifiers in all peat types was limited by the low availability of easily decomposable C source. Increasing
moisture contents of all peats from 40 to 50% water-filled pore space (WFPS) did not significantly (p > 0.05) increase (N2O + N2)–N emissions. However, a positive effect was observed when the moisture contents were increased from 60% to 70% WFPS in the
eutrophic peat, from 70% to 80% in the transitional, from 80% to 90% in the oligotrophic and from 70% to 90% in the mesotrophic
peat. It can be concluded that liming, N-fertilization, availability of easily decomposable C, and moist condition above 60%
WFPS could encourage denitrification from peats although the rates are greatly influenced by the peat-forming environments
(eutrophic > mesotrophic > oligotrophic > transitional types). 相似文献
14.
Use of Ozonization for the Treatment of Dye Wastewaters Containing Rhodamine B in the Agate Industry
Machado Ênio Leandro de Sales Dambros Vagner Kist Lourdes Teresinha Alcayaga Lobo Eduardo Alexis Tedesco Solange Bosio Moro Celso Camilo 《Water, air, and soil pollution》2012,223(4):1753-1764
The industrial processing of precious stones is a source of revenue for several Brazilian towns, especially in the state of
Rio Grande do Sul. Given the growing number of small-sized companies that process precious stones, wastewater production is
inevitable and is a cause for concern inasmuch as preservation of nature is considered. The present study investigates the
detoxification of the wastewater produced by the process of rhodamine B dyeing using oxidation processes. Ozonization (O3), ultraviolet irradiation (UV), and O3/UV methods were assessed. Some of the parameters used to measure the efficiency of the analyzed treatments included COD,
ecotoxicity (Daphnia magna), cytotoxicity, and genotoxicity assays (Allium cepa assays). Results show predominance of negative and local environmental impacts, which are reversible in more than 70% of
cases. The major proposed reversibility measures were the change in the process layout and dye wastewater segregation. Among
the analyzed methods, ozonization proved to be more efficient in decolorization, with 60 min of treatment, pH = 9 and dosage
of 5.705 mg O3/mg of rhodamine B. A pseudo first-order reaction, with a kinetic constant of 7.5 × 10−2 min−1, was observed. The cytotoxic and genotoxic effects were assessed for both raw and treated wastewaters. Despite complete decolorization,
cytotoxicity and genotoxicity assays revealed an EC50 of 28.6, in addition to chromosome aberrations in 40% of dividing cells for the treated wastewater. 相似文献
15.
This study presents the application of soybean seed hulls for the decontamination and/or detoxification of phenol and chlorophenol polluted soils. The effect of soil was examined on both catalytic activity of soybean seed hull peroxidase (SBP) and enzymatic transformation of phenol, 2-chlorophenol, and 2,4-dichlorophenol through the polymerization reaction. The sorption of the enzyme to soil organic matter was found to account for the loss of partial catalytic activity of soybean seed hulls in a soil slurry environment. The organic matter present in loamy soils, rather than other soluble soil constituents and soil micro-organisms, is a factor in SBP inhibition by soil and the corresponding decline in treatment efficiency of phenol and chlorophenols. Under improved conditions, however, soybean seed hulls demonstrated a satisfactory ability to catalyze the polymerization reaction. Over 96% of total phenols were removed using soybean seed hulls in a soil slurry bioreactor, which demonstrates a great potential in use of soybean seed hulls, a readily available and inexpensive source of SBP, for bioremediation of soils contaminated with phenolic compounds. 相似文献
16.
Release of sulphate, potassium, calcium and magnesium from spent mushroom compost under laboratory conditions 总被引:1,自引:0,他引:1
D. P. C. Stewart K. C. Cameron I. S. Cornforth B. E. Main 《Biology and Fertility of Soils》1997,26(2):146-151
The release of sulphate-sulphur (SO4
2–-S), potassium (K), calcium (Ca) and magnesium (Mg) from soil amended with spent mushroom compost (SMC), a by-product of mushroom
production, was measured for 16 weeks in an open laboratory incubation at 25°C. Rates of application were up to 80 t ha–1 moist SMC (0.84% SMC dry weight) both with and without inorganic fertilizer. The rates of nutrient application in the inorganic
fertilizer were: 338 kg ha–1 N, 100 kg ha–1 of both phosphorus and K, and 114 kg ha–1 S. SMC contains 1.7% K, 6.5% Ca, 0.4% Mg and 1.2% S (of which 87% is inorganic), and has a carbon:sulphur ratio of 26. The
release of SO4
2–-S was rapid, and was described using either a first or mixed order exponential equation, or (underestimated) by the CENTURY
model. The release of K, Ca and Mg was initially rapid (first order) and then declined to a constant rate (zero order). Their
release was also described using first/first order or first order/parabolic diffusion equations. Model parameters indicated
the relative sizes of both readily releasable and recalcitrant nutrient pools. The recovery of SMC-supplied nutrients in the
absence of fertilizer was 75–83% of the S, 40–45% of the K, 14–20% of the Ca and 43–66% of the Mg. When fertilizer was applied
33–45% of the S, 22–36% of the K, 12–24% of the Ca and –4 to 20% of the Mg that were supplied by the SMC and fertilizer were
recovered in the leachate. The generally lower nutrient recovery when fertilizer was applied could have resulted from the
incomplete recovery of fertilizer S and K, from soil fixation of applied nutrients, and from the lower pH following fertilizer
application.
Received: 3 April 1997 相似文献
17.
Mohammad Mofizur Rahman Jahangir Dries Roobroeck Oswald Van Cleemput Pascal Boeckx 《Biology and Fertility of Soils》2011,47(7):753-766
Nitrous oxide (N2O) emissions, soil microbial community structure, bulk density, total pore volume, total C and N, aggregate mean weight diameter
and stability index were determined in arable soils under three different types of tillage: reduced tillage (RT), no tillage
(NT) and conventional tillage (CT). Thirty intact soil cores, each in a 25 × 25-m2 grid, were collected to a depth of 10 cm at the seedling stage of winter wheat in February 2008 from Maulde (50°3′ N, 3°43′ W),
Belgium. Two additional soil samples adjacent to each soil core were taken to measure the spatial variance in biotic and physicochemical
conditions. The microbial community structure was evaluated by means of phospholipid fatty acids analysis. Soil cores were
amended with 15 kg NO3−-N ha−1, 15 kg NH4+-N ha−1 and 30 kg ha−1 urea-N ha−1 and then brought to 65% water-filled pore space and incubated for 21 days at 15°C, with regular monitoring of N2O emissions. The N2O fluxes showed a log-normal distribution with mean coefficients of variance (CV) of 122%, 78% and 90% in RT, NT and CT, respectively,
indicating a high spatial variation. However, this variability of N2O emissions did not show plot scale spatial dependence. The N2O emissions from RT were higher (p < 0.01) than from CT and NT. Multivariate analysis of soil properties showed that PC1 of principal component analysis had
highest loadings for aggregate mean weight diameter, total C and fungi/bacteria ratio. Stepwise multiple regression based
on soil properties explained 72% (p < 0.01) of the variance of N2O emissions. Spatial distributions of soil properties controlling N2O emissions were different in three different tillages with CV ranked as RT > CT > NT. 相似文献
18.
The impacts of crop rotations and N fertilization on different pools of urease activity were studied in soils of two long-term
field experiments in Iowa; at the Northeast Research Center (NERC) and the Clarion-Webster Research Center (CWRC). Surface
soil samples (0–15 cm) were taken in 1996 and 1997 in corn, soybeans, oats, or meadow (alfalfa) plots that received 0 or 180 kg
N ha–1, applied as urea before corn and an annual application of 20 kg P and 56 kg K ha–1. The urease activity in the soils was assayed at optimal pH (THAM buffer, pH 9.0), with and without toluene treatment, in
a chloroform-fumigated sample and its nonfumigated counterpart. The microbial biomass C (Cmic) and N (Nmic) were determined by chloroform fumigation methods. The total, intracellular, extracellular and specific urease activities
in the soils of the NERC site were significantly affected by crop rotation, but not by N fertilization. Generally, the highest
total urease activities were obtained in soils under 4-year oats–meadow rotations and the lowest under continuous corn. The
higher total activities under multicropping systems were caused by a higher activity of both the intracellular and extracellular
urease fractions. In contrast, the highest values for the specific urease activity, i.e. of urease activity of the microbial
biomass, were found in soils under continuous soybean and the least under the 4-year rotations. Total and extracellular urease
activities were significantly correlated with Cmic (r>0.30* and >0.40**) and Nmic (r>0.39** and >0.44**) in soils of the NERC and CWRC sites, respectively. Total urease activity was significantly correlated
with the intracellular activity (r>0.73***). About 46% of the total urease activity of the soils was associated with the microbial biomass, and 54% was extracellular
in nature.
Received: 25 May 1999 相似文献
19.
Balaji Anandha Rao Cameron P. Wake Todd Anderson William Andrew Jackson 《Water, air, and soil pollution》2012,223(1):181-188
Temporal depositional rates are important in order to understand the production and occurrence of perchlorate (ClO4−) as limited information exists regarding the impact of anthropogenic production or atmospheric pollution on ClO4− deposition. Perchlorate concentrations in discrete ice core samples from the Eclipse Icefield (Yukon Territory, Canada) and
Upper Fremont Glacier (Wyoming, USA) were analyzed using ion chromatography tandem mass spectrometry to evaluate temporal
changes in the deposition of ClO4
− in North America. The ice core samples cover a time period from 1726 to 1993 and 1970 to 2002 for the Upper Fremont Glacier
(UFG) and Eclipse ice cores, respectively. The average ClO4
− concentration in the Eclipse ice core for the time period from 1970 to 1973 was 0.6 ± 0.3 ng L−1, with higher values of 2.3 ± 1.7 and 2.2 ± 2.0 ng L−1 for the periods 1982–1986 and 1999–2002, respectively. All pre-1980 ice core samples from the UFG had ClO4
− concentrations <0.2 ng L−1, and the post-1980 samples ranged from <0.2 ng L−1 to a maximum of 2.6 ng L−1 for the year 1992. A significant positive correlation (R = 0.75, N = 15, p < 0.001) of ClO4− with SO42− was found for the annual UFG ice core layers and of ClO4
− with SO42− and NO3− in sub-annual Eclipse ice samples (R > 0.3, N = 121, p < 0.002). The estimated yearly ClO4− depositional flux for the Eclipse ice core ranged from 0.6 (1970) to 4.7 μg m−2 year−1 (1982) and the UFG from <0.1 (pre-1980) to 1.4 μg m−2 year−1 (1992). There was no consistent seasonal variation in the ClO4− depositional flux for the Eclipse ice core, in contrast to a previous study on the Arctic region. The presence of ClO4− in these ice cores might correspond to an intermittent source such as volcanic eruptions and/or any anthropogenic forcing
that may directly or indirectly aid in atmospheric ClO4− formation. 相似文献
20.
Many phosphate solubilizing microorganisms (PSM) require external pyrroloquinoline quinone (PQQ) for strong phosphorus (P)
solubilization in vitro. The objective of this study was to isolate efficient and PQQ-independent PSM. A total of 21 PSM were
isolated from the rhizosphere soil of wheat and maize grown in the pots. Acinetobacter strains were the only PQQ-independent and most effective solubilizers of tricalcium phosphate containing agar. The mean P
dissolved in liquid cultures of Acinetobacter strains in a 5-day incubation ranged from 167 to 888 μg/ml P. The pH dropped to below 4.7 from 7.8 in six isolates, which
produced gluconic acid in concentrations ranging between 27.5 and 37.5 mM. There was a linear regression between soluble P
and gluconic acid concentrations in the bacterial cultures (P < 0.05; R
2 = 0.59). Inoculation with Acinetobacter sp. WR922 significantly (P < 0.05) increased wheat (Triticum aestivum L.) P content by 27% at 15 days after emergence (DAE) and dry matter by 15% at 30 DAE compared to the control. The plant
P content in inoculated plants at 30 DAE was linearly correlated with soluble P of the bacterial cultures (P < 0.05; R
2 = 0.69). Gluconic acid production directly affected phosphate solubilization in vitro, which in turn influenced plant P content
of inoculated plants in PQQ-independent P-solubilizing Acinetobacter strains. 相似文献