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1.
Robert John Wilcock Karin Müller Gareth B. van Assema Margaret A. Bellingham Ron Ovenden 《Water, air, and soil pollution》2012,223(2):499-509
Water quantity and quality were monitored for 3 years in a 360-m-long wetland with riparian fences and plants in a pastoral
dairy farming catchment. Concentrations of total nitrogen (TN), total phosphorus (TP) and Escherichia coli were 210–75,200 g N m−3, 12–58,200 g P m−3 and 2–20,000 most probable number (MPN)/100 ml, respectively. Average retentions (±standard error) for the wetland over 3 years
were 5 ± 1%, 93 ± 13% and 65 ± 9% for TN, TP and E. coli, respectively. Retentions for nitrate–N, ammonium–N, filterable reactive P and particulate C were respectively −29 ± 5%,
32 ± 10%, −53 ± 24% and 96 ± 19%. Aerobic conditions within the wetland supported nitrification but not denitrification and
it is likely that there was a high conversion rate from dissolved inputs of N and P in groundwater, to particulate N and P
and refractory dissolved forms in the wetland. The wetland was notable for its capacity to promote the formation of particulate
forms and retain them or to provide conditions suitable for retention (e.g. binding of phosphate to cations). Nitrogen retention
was generally low because about 60% was in dissolved forms (DON and NOX–N) that were not readily trapped or removed. Specific yields for N, P and E. coli were c. 10–11 kg N ha−1 year−1, 0.2 kg P ha−1 year−1 and ≤109 MPN ha−1 year−1, respectively, and generally much less than ranges for typical dairy pasture catchments in New Zealand. Further mitigation
of catchment runoff losses might be achieved if the upland wetland was coupled with a downslope wetland in which anoxic conditions
would promote denitrification. 相似文献
2.
We compared, from 2004 through 2006, rates of soil–atmosphere CH4 exchange at permanently established sampling sites in a temperate forest exposed to ambient (control plots; ∼380 μL L−1) or elevated (ambient + 200 μL L−1) CO2 since August 1996. A total of 880 observations showed net atmospheric CH4 consumption (flux from the atmosphere to the soil) from all static chambers most of the time at rates varying from 0.02 mg m−2 day−1 to 4.5 mg m−2 day−1. However, we infrequently found net CH4 production (flux from the soil to the atmosphere) at lower rates, 0.01 mg m−2 day−1 to 0.08 mg m−2 day−1. For the entire study, the mean (±SEM) rate of net CH4 consumption in control plots was higher than the mean for CO2-enriched plots, 0.55 (0.03) versus 0.51 (0.03) mg m−2 day−1. Annual rates of 184, 196, and 197 mg m−2 for net CH4 consumption at control plots during the three calendar years of this study were 19, 10, and 8% higher than comparable values
for CO2 enriched plots. Differences between treatments were significant in 2004 and 2005 and nearly significant in 2006. Volumetric
soil water content was consistently higher at CO2-enriched sites and a mixed-effects model identified a significant soil moisture x CO2 interaction on net atmospheric CH4 consumption. Increased soil moisture at CO2-enriched sites likely increases diffusional resistance of surface soils and the frequency of anaerobic microsites supporting
methanogenesis, resulting in reduced rates of net atmospheric CH4 consumption. Our study extends our observations of reduced net atmospheric CH4 consumption at CO2-enriched plots to nearly five continuous years, suggesting that this is likely a sustained negative feedback to increasing
atmospheric CO2 at this site. 相似文献
3.
Effects of moisture and temperature on greenhouse gas emissions and C and N leaching losses in soil treated with biogas slurry 总被引:1,自引:0,他引:1
The objective of this study was to examine the effects of soil moisture, irrigation pattern, and temperature on gaseous and
leaching losses of carbon (C) and nitrogen (N) from soils amended with biogas slurry (BS). Undisturbed soil cores were amended
with BS (33 kg N ha−1) and incubated at 13.5°C and 23.5°C under continuous irrigation (2 mm day−1) or cycles of strong irrigation and partial drying (every 6 weeks, 1 week with 12 mm day−1). During the 6 weeks after BS application, on average, 30% and 3.8% of the C and N applied with BS were emitted as carbon
dioxide (CO2) and nitrous oxide (N2O), respectively. Across all treatments, a temperature increase of 10°C increased N2O and CO2 emissions by a factor of 3.7 and 1.7, respectively. The irrigation pattern strongly affected the temporal production of CO2 and N2O but had no significant effect on the cumulative production. Nitrogen was predominantly lost in the form of nitrate (NO3−). On average, 16% of the N applied was lost as NO3−. Nitrate leaching was significantly increased at the higher temperature (P < 0.01), while the irrigation pattern had no effect (P = 0.63). Our results show that the C and N turnovers were strongly affected by BS application and soil temperature whereas
irrigation pattern had only minor effects. A considerable proportion of the C and N in BS were readily available for soil
microorganisms. 相似文献
4.
The study examined the influence of compost and mineral fertilizer application on the content and stability of soil organic
carbon (SOC). Soil samples collected from a long-term field experiment were separated into macroaggregate, microaggregate,
and silt + clay fractions by wet-sieving. The experiment involved seven treatments: compost, half-compost N plus half-fertilizer
N, fertilizer NPK, fertilizer NP, fertilizer NK, fertilizer PK, and control. The 18-year application of compost increased
SOC by 70.7–121.7%, and mineral fertilizer increased by 5.4–25.5%, with no significant difference between control soil and
initial soil. The C mineralization rate (rate per unit dry mass) in microaggregates was 1.52–2.87 mg C kg−1 day−1, significantly lower than in macroaggregate and silt + clay fractions (P < 0.05). Specific C mineralization rate (rate per unit SOC) in silt + clay fraction amounted to 0.48–0.87 mg C g−1 SOC day−1 and was higher than in macroaggregates and microaggregates. Our data indicate that SOC in microaggregates is more stable
than in macroaggregate and silt + clay fractions. Compost and mineral fertilizer application increased C mineralization rate
in all aggregates compared with control. However, compost application significantly decreased specific C mineralization rate
in microaggregate and silt + clay fractions by 2.6–28.2% and 21.9–25.0%, respectively (P < 0.05). By contrast, fertilizer NPK application did not affect specific C mineralization rate in microaggregates but significantly
increased that in silt + clay fractions. Carbon sequestration in compost-amended soil was therefore due to improving SOC stability
in microaggregate and silt + clay fractions. In contrast, fertilizer NPK application enhanced SOC with low stability in macroaggregate
and silt + clay fractions. 相似文献
5.
Plant growth-promoting rhizobacteria (PGPR) play an important role in the biodegradation of natural and xenobiotic organic
compounds in soil. They can also alter heavy metal bioavailability and contribute to phytoremediation in the presence or absence
of synthetic metal chelating agents. In this study, the inhibitory effect of Cd2+ and Ni2+ at different concentrations of Ca2+ and Mg2+, and the influence of the widely used chelator EDTA on growth of the PGPR Pseudomonas brassicacearum in a mineral salt medium with a mixture of four main plant exudates (glucose, fructose, citrate, succinate) was investigated.
Therefore, the bacteriostatic effect of Cd2+, Ni2+ and EDTA on the maximum specific growth rate and the determination of EC50 values was used to quantify inhibitory impact.
At high concentrations of Ca2+ (800 μmol L-1) and Mg2+ (1,250 μmol L-1), only a small inhibitory effect of Cd2+ and Ni2+ on growth of P. brassicacearum was observed (EC50 Cd2+, 18,849 ± 80 μmol L−1; EC50 Ni2+, 3,578 ± 1,002 μmol L−1). The inhibition was much greater at low concentrations of Ca2+ (25 μmol L−1) and Mg2+ (100 μmol L−1) (EC50 Cd2+, 85 ± 0.5 μmol L−1 and EC Ni2+, 62 ± 1.8 μmol L−1). For the chosen model system, a competitive effect of the ions Cd2+ and Ca2+ on the one hand and Ni2+ and Mg2+ on the other hand can be deduced. However, the toxicity of both, Cd2+ and Ni2+, could be significantly reduced by addition of EDTA, but if this chelating agent was added in stoichiometric excess to the
cations, it also exhibited an inhibitory effect on growth of P. brassicacearum. 相似文献
6.
Richard W. Todd N. Andy Cole R. Nolan Clark William C. Rice Wen-Xuan Guo 《Biology and Fertility of Soils》2008,44(8):1099-1102
Cattle feedyards can impact local environments through emission of ammonia and dust deposited on nearby land. Impacts range
from beneficial fertilization of cropland to detrimental effects on sensitive ecosystems. Shortgrass prairie downwind from
an adjacent feedyard on the southern High Plains of Texas, USA changed from perennial grasses to annual weeds. It was hypothesized
that N enrichment from the feedyard initiated the cascade of negative ecological change. Objectives were to determine the
distribution of soil nitrogen and estimate N loading to the pasture. Soil samples were collected from 119 locations across
the pasture and soil total N (TN), nitrate-N and ammonium-N (AN) determined in the top 30 cm. Soil TN concentration decreased
with distance downwind from the feedyard from 1.6 ± 0.2 g kg−1 at 75 m to 1.2 ± 0.05 g kg−1 at 582 m. Nitrate-N concentration decreased within 200 m of the feedyard and changed little at greater distances. Ammonium-N
concentration decreased linearly (P < 0.001) with increasing distance from the feedyard from 7.9 ± 1.7 mg kg−1 within 75 m from the feedyard to 5.8 ± 1.5 mg kg−1 at more than 550 m from the feedyard; however, distance only explained 12% of the variability in AN concentration. Maximum
nitrogen loading, from 75 to 106 m from the feedyard, was 49 kg ha−1 year−1 over 34 years and decreased with distance from the feedyard. An estimate of net dry deposition of ammonia indicated that
it contributed negligibly to N loading to the pasture. Nitrogen enrichment that potentially shifted vegetation from perennial
grasses to annual weeds affected soil N up to 500 m from the feedyard; however, measured organic and inorganic N beyond that
returned to typical and expected levels for undisturbed shortgrass prairie.
相似文献
Richard W. ToddEmail: |
7.
Crop residues and fertilizer nitrogen influence residue decomposition and nitrous oxide emission from a Vertisol 总被引:2,自引:0,他引:2
Wisal Muhammad Sarah M. Vaughan Ram C. Dalal Neal W. Menzies 《Biology and Fertility of Soils》2011,47(1):15-23
Crop residues with high C/N ratio immobilize N released during decomposition in soil, thus reducing N losses through leaching,
denitrification, and nitrous oxide (N2O) emission. A laboratory incubation experiment was conducted for 84 days under controlled conditions (24°C and moisture content
55% of water-holding capacity) to study the influence of sugarcane, maize, sorghum, cotton and lucerne residues, and mineral
N addition, on N mineralization–immobilization and N2O emission. Residues were added at the rate of 3 t C ha−1 to soil with, and without, 150 kg urea N ha−1. The addition of sugarcane, maize, and sorghum residues without N fertilizer resulted in a significant immobilization of
soil N. Amended soil had significantly (P < 0.05) lower NO3−–N, which reached minimum values of 2.8 mg N kg−1 for sugarcane (at day 28), 10.3 mg N kg−1 for maize (day 7), and 5.9 mg N kg−1 for sorghum (day 7), compared to 22.7 mg N kg−1 for the unamended soil (day 7). During 84 days of incubation, the total mineral N in the residues + N treatments were decreased
by 45 mg N kg−1 in sugarcane, 34 mg kg−1 in maize, 29 mg kg−1 in sorghum, and 16 mg kg−1 in cotton amended soil compared to soil + N fertilizer, although soil NO3−–N increased by 7 mg kg−1 in lucerne amended soil. The addition of residues also significantly increased amended soil microbial biomass C and N. Maximum
emissions of N2O from crop residue amended soils occurred in the first 4–5 days of incubation. Overall, after 84 days of incubation, the
cumulative N2O emission was 25% lower with cotton + N fertilizer, compared to soil + N fertilizer. The cumulative N2O emission was significantly and positively correlated with NO3−–N (r = 0.92, P < 0.01) and total mineral N (r = 0.93, P < 0.01) after 84 days of incubation, and had a weak but significant positive correlation with cumulative CO2 in the first 3 and 5 days of incubation (r = 0.59, P < 0.05). 相似文献
8.
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
9.
Balaji Rao Suhas Mohan Andreas Neuber William Andrew Jackson 《Water, air, and soil pollution》2012,223(1):275-287
Perchlorate (ClO4−), a thyroid hormone disruptor, is both naturally occurring and a man-made contaminant increasingly found in a variety of
terrestrial environments. The environmental presence of ClO4− is considered to be the result of atmospheric formation and deposition processes. The ultimate processes, particularly heterogeneous-based
reactions, leading to natural ClO4− formation are not well understood. Oxidation of chlorine species by an energetic source such as lightning is considered to
be one of the potential heterogeneous sources of natural ClO4−. Currently, there is very little information available on lightning-induced ClO4−. We designed a laboratory electrical discharge reactor capable of evaluating ClO4− formation by the oxidation of “dry” sodium chloride (NaCl) aerosols (relative humidity (RH) <70%) in electrical discharge
plasma at voltages and energies up to 24 kV and 21 kJ, respectively. Similar to other non-electrochemical ClO4− production processes, the amount of ClO4− produced (0.5–4.8 μg) was 3 orders of magnitude lower than the input Cl− (7.1–60.1 mg). The amount of ClO4− generated increased with peak voltage (V) and theoretical maximum discharge energy with ΔClO4−/ΔV = 0.28 × 10−3 μg V−1 (R
2 = 0.94) and ΔClO4−/ΔE = 0.44 × 10−3 μg J−1 (R
2 = 0.83). The total ClO4− generated decreased with an increase in relative humidity from 2.8 ± 0.1 μg (RH ∼46%) to 0.9 ± 0.1 μg (RH ∼62%) indicating
that the presence of moisture inhibits the formation of ClO4−. Additional modifications to the reactor support the hypothesis of ClO4− formation due to the action of plasma on Cl− aerosols as opposed to direct oxidation on the surface of the electrodes. Finally, the contribution of lightning-induced
ClO4− in North America is calculated to have a wide range from 0.006 × 105 to 5 × 105 kg/year and is within the range of the measured ClO4− depositional flux in precipitation samples obtained across the USA (0.09 × 105–1.2 × 105 kg/y). 相似文献
10.
C. Alejandra Villamar Teresa Cañuta Marisol Belmonte Gladys Vidal 《Water, air, and soil pollution》2012,223(1):363-369
Since swine wastewater is used by farmers for soil fertilization, evaluation of toxic compounds or micro-contaminants of separate
streams is required. This paper uses the toxicity identification evaluation (TIE) procedure for the physicochemical and ecotoxicological
characterization of swine wastewater. To distinguish the most important toxic compounds, a physicochemical characterization
and phase I-TIE procedure were performed. The acute toxic effect of swine wastewater and treated fractions (phase II-TIE)
were evaluated using Daphnia magna determining 48-h LC50. Results show a high level of conductivity (23.5 μS cm−1), which is explained as due to the concentration of ions, such as ammonium (NH4+–N 1.6 g L−1), sulfate (SO42− 397.3 mg L−1), and chlorine (Cl− 1,230.0 mg L−1). The acute toxicity of the swine wastewater was evaluated on D. magna (48-h LC50 = 3.4%). Results of the different water treatments indicate that anionic exchange treatments could reduce 22.5% of swine
wastewater’s acute toxicity by reducing chlorine (to around 51%) and conductivity (8.5%). On the other hand, cationic exchange
treatment increased acute toxicity on D. magna (% RT = −624.4%), by reducing NH4+–N (around 100%) and total nitrogen (95.5%). This finding suggests that part of the toxicity comes from anionic compounds,
such as chlorine. 相似文献
11.
Chun-Chao Chuang Yu-Lin Kuo Chen-Ching Chao Wei-Liang Chao 《Biology and Fertility of Soils》2007,43(5):575-584
Two of 187 fungal isolates (Aspergillus niger 1B and 6A) displaying superior phosphate (P) solubilization and hydrolytic enzyme secretion were studied using P forms of
calcium (Ca-P), iron (Fe-P), and aluminum (Al-P). Phosphate solubilization in a sucrose-basal salt (SB) broth was increased
and pH decreased by both isolates. In Ca-P medium, solubilization for 6A was approximately 322 μg P mL−1 and pH decreased by 4.2 units to 2.3 in 72 h. However, when pH value of the SB broth was lowered to 2.5 using HCl, 65.3 ± 0.4 μg
mL−1 of P was released from Ca-P, whereas trace amounts of P were released from Fe-P and Al-P. Both isolates displayed enhanced
Al-P solubilization using NH4Cl rather than KNO3 as the N source; final pH values were not significantly different. With Ca-P, gluconic acid was predominantly produced by
1B and 6A, whereas oxalic acid predominated with Fe-P and Al-P. Addition of gluconic acid (final concentration of 8.5 μmol
mL−1) to Ca-P-supplemented SB lowered pH (2.9) and solubilized phosphate (146.0 ± 1.0 μg mL−1). Similarly, addition of oxalic acid (final concentration 6.6 μmol mL−1) to Ca-P- and Fe-P-amended media solubilized P (60.2 ± 0.9 and 21.6 ± 2.1 μg mL−1, respectively), although these quantities were significantly lower than those detected in unamended SB. The presence of unidentified
P solubilized compound(s) in the dialyzed (MW>500) supernatant warrants further study. In pot experiments, significant increases
in plant (Brassica chinensis Linn.) dry weight and N and P contents were observed with the addition of isolate 6A, when a small amount of organic fertilizer
together with either rock phosphate (South African apatite) or Ca-P served as the main P sources. 相似文献
12.
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
13.
Cotton Verticillium wilt is a destructive soil-borne disease affecting cotton production. In this study, application of bio-organic fertilizer
(BIO) at the beginning of nursery growth and/or at the beginning of transplanting was evaluated for its ability to control
Verticillium dahliae Kleb. The most efficient control of cotton Verticillium wilt was achieved when the nursery application of BIO was combined with a second application in transplanted soil, resulting
in a wilt disease incidence of only 4.4%, compared with 90.0% in the control. Denaturing gradient gel electrophoresis patterns
showed that the consecutive applications of BIO at nursery and transplanting stage resulted in the presence of a unique group
of fungi not found in any other treatments. Humicola sp., Metarhizium anisopliae, and Chaetomium sp., which were considered to be beneficial fungi, were found in the BIO treatment, whereas some harmful fungi, such as Alternaria alternate, Coniochaeta velutina, and Chaetothyriales sp. were detected in the control. After the consecutive applications of BIO at nursery and transplanting stage, the V. dahliae population in the rhizosphere soil in the budding period, flowering and boll-forming stage, boll-opening stage, and at harvest
time were 8.5 × 102, 3.1 × 102, 4.6 × 102, and 1.7 × 102 colony-forming units per gram of soil (cfu g−1), respectively, which were significantly lower than in the control (6.1 × 103, 3.4 × 103, 5.2 × 103, and 7.0 × 103 cfu g−1, respectively). These results indicate that the suggested application mode of BIO could effectively control cotton Verticillium wilt by significantly changing the fungal community structure and reducing the V. dahliae population in the rhizosphere soil. 相似文献
14.
Secondary salinity effects on soil microbial biomass 总被引:2,自引:0,他引:2
Dilfuza Egamberdieva Giancarlo Renella Stephan Wirth Rafiq Islam 《Biology and Fertility of Soils》2010,46(5):445-449
Secondary soil salinilization is a big problem in irrigated agriculture. We have studied the effects of irrigation-induced
salinity on microbial biomass of soil under traditional cotton (Gossypium hirsutum L.) monoculture in Sayhunobod district of the Syr-Darya province of northwest Uzbekistan. Composite samples were randomly
collected at 0–30 cm depth from weakly saline (2.3 ± 0.3 dS m−1), moderately saline (5.6 ± 0.6 dS m−1), and strongly saline (7.1 ± 0.6 dS m−1) replicated fields, 2-mm sieved, and analyzed for pH, electrical conductivity, total C, organic C (COrg), and extractable C, total N and P, and exchangeable ions (Ca2+, Mg2+, K+, Na+, Cl−, and CO32−), microbial biomass (Cmic). The Na+ and Cl− concentrations were 36-80% higher in strongly saline compared to weakly saline soil. The COrg concentration was decreased by 10% and CExt by 40% by increasing soil salinity, whereas decrease in Cmic ranged from 18-42% and the percentage of COrg present as Cmic from 8% to 26%. We conclude that irrigation-induced secondary salinity significantly affects soil chemical properties and
the size of soil microflora. 相似文献
15.
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
16.
In this study, the effects of 1 h aeration, nitrogen gas N2(g) sparging (15 and 30 min) and increasing ferric ions (Fe+3) as FeSO4 (10, 20 and 50 mg L−1) and Fe3O4 nanoparticles (1, 2 and 4 g L−1) concentrations on three less hydrophobic and three more hydrophobic polycyclic aromatic hydrocarbons (PAHs) and toxicity
removals from a petrochemical industry in Izmir (Turkey) were investigated in a sonicator with a power of 650 W and an ultrasound
frequency of 35 kHz; 1 h aeration increased the yields in benzo[b]fluoranthene, benzo[k]fluoranthene and benzo[a]pyrene PAHs (less hydrophobic) from 62% to 67% to around 95–97% after 150 min sonication at 60°C. However, 1 h aeration did
not contribute to the yields of more hydrophobic PAHs (indeno[1,2,3-cd]pyrene, dibenz[a,h]anthracene, benzo[g,h,i]perylene). The maximum yields were obtained at acidic and alkaline pH for more and less hydrophobic PAHs, respectively, after
60 and 120 min sonication at 30°C; 30 min N2(g) sparging, 50 mg L−1 Fe+3 increased the yields of less hydropobic PAHs after 150 min sonication at 60°C. Two milligrams per liter of Fe3O4 nanoparticles increased both less (87–88%) and more (96–98%) hydrophobic PAH yields. The Daphnia magna acute toxicity test showed that the toxicity decreased significantly with an hour aeration, 30 min N2(g) sparging, 50 mg L−1 Fe+3 and 2 g L−1 Fe3O4 nanoparticles at 60°C after 120 and 150 min sonications. Vibrio fischeri was found to be more resistant to the sonicated samples than D. magna. Significant correlations were found between the physicochemical properties of sonicated PAHs and acute toxicities both organisms. 相似文献
17.
High yield culture medium is fundamental for production of inoculants for plant growth-promoting bacteria. Based on substitution
of glucose in tryptone–yeast extract–glucose medium by Na-gluconate or glycerol, two new culture media were developed for
mass cultivation of the commonly used plant growth-promoting bacterium Azospirillum sp. After 18 h of incubation, these modifications increased populations of different strains of Azospirillum (to ∼1011 cells ml−1 [single cell count] and ∼5 × 109 CFU ml−1 [plate count method]), significantly reduced generation time, and were also suitable for production of common synthetic inoculants. 相似文献
18.
The response of faba bean to the application of four rates of gypsum (0, 2.5, 5.0, 10.0 t ha−1) to a non-saline, alkaline sodic soil was measured in terms of grain yield, dry matter (DM) production, N accumulation and
the proportional dependence of the legume on symbiotic N2 fixation (P
atm). A yield-independent, time-integrated 15N-dilution model was used to estimate symbiotic dependence. A significant decrease in the exchangeable sodium percentage and
significant increases in exchangeable Ca++ and the Ca++:Mg++ ratio in the 0–10-cm soil layer were measured 30 months after application of 10 t ha−1 gypsum. Despite low and erratic rainfall during crop growth, faba bean DM and N uptake responded positively to gypsum application.
The symbiotic dependence of the legume at physiological maturity was little affected by sodicity (P
atm = 0.74 at zero gypsum and 0.81–0.82 at 2.5–10 t ha−1 gypsum). The increase in fixed N due to gypsum application was mainly due to increases in legume DM and total N uptake. At
10 t ha−1 of gypsum, faba bean fixed more than 200 kg N ha−1 in above-ground biomass. 相似文献
19.
Pot experiments were carried out over two growing periods to assay the biocontrol efficacy and rhizosphere colonization of
Trichoderma harzianum SQR-T037 (SQR-T037) applied as SQR-T037 conidia suspension (TCS), SQR-T037 conidia suspension blended with organic fertilizer
(TBF), or SQR-T037 fermented organic fertilizer (TFF). Each formulation had three T. harzianum numbers. In two experiments, Percent Disease Indexes (PDIs) decreased with the increase of SQR-T037 number added to soils.
The TFF treatment consistently exhibited the lowest PDIs at same amendment rate of SQR-T037 and 0–8.9%, 25.6–78.9%, and 4.4–50.0%
of PDIs were found in TFF, TCS, and TBF treatment, respectively. Soils treated with TFF showed the highest SQR-T037 population
in rhizosphere and bulk soil. Decrease of Fusarium oxysporum population in both bulk and rhizosphere soils occurred in the treatment SQR-T037 at 105 and 106 cfug−1 soil rate. The TFF treatment at the SQR-T037 rate of 103 cfug−1 soil significantly (p < 0.05) increased SQR-T037 population within the rhizoplane but had no effect on F. oxysporum population when compared to TCS and TBF. Generally, TFF treatments were superior to TCS and TBF treatments on disease control
by sustaining colonization of SQR-T037 and decreasing F. oxysporum abundance in the rhizosphere soil. We propose that TFF treatment at SQR-T037 rate of 107 cfug−1 (i.e., 105 cfug−1 soil after applied to soil) was the best formulation for controlling Fusarium wilt of cucumber. 相似文献
20.
Yunpu Zheng Ming Xu Jiancheng Zhao Shuqing Bei Lihua Hao 《Biology and Fertility of Soils》2011,47(4):473-480
Microcoleus vaginatus Gom., the dominant species in biological soil crusts (BSCs) in desert regions, plays a significant role in maintaining the
BSC structure and function. The BSC quality is commonly assessed by the chlorophyll a content, thickness, and compressive
strength. Here, we have studied the effect of different proportions of M. vaginatus, collected from the Gurbantunggut Desert in northwestern China, on the BSC structure and function under laboratory conditions.
We found that when M. vaginatus was absent in the BSC, the BSC coverage, quantified by the percentage of BSC area to total land surface area, was low with
a chlorophyll a content of 4.77 × 10−2 mg g−1 dry soil, a thickness of 0.86 mm, and a compressive strength of 12.21 Pa. By increasing the percentage of M. vaginatus in the BSC, the BSC coverage, chlorophyll a content, crust thickness, and compressive strength all significantly increased
(P < 0.01). The maximum chlorophyll a content (13.12 mg g−1dry soil), the highest crust thickness, and the compressive strength (1.48 mm and 36.60 Pa, respectively) occurred when the
percentage of inoculated M. vaginatus reached 80% with a complex network of filaments under scanning electron microscope. The BSC quality indicated by the above
variables, however, declined when the BSC was composed of pure M. vaginatus (monoculture). In addition, we found that secretion of filaments and polymer, which stick sands together in the BSC, increased
remarkably with the increase of the dominant species until the percentage of M. vaginatus reached 80%. Our results suggest that not only the dominant species but also the accompanying taxa are critical for maintaining
the structure and functions of the BSC and thus the stability of the BSC ecosystems. 相似文献