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1.
In this study, the effects of 1 h aeration, nitrogen gas N 2(g) sparging (15 and 30 min) and increasing ferric ions (Fe +3) as FeSO 4 (10, 20 and 50 mg L −1) and Fe 3O 4 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 N 2(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 Fe 3O 4 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 N 2(g) sparging, 50 mg L −1 Fe +3 and 2 g L −1 Fe 3O 4 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
2.
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 (O 3), ultraviolet irradiation (UV), and O 3/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 O 3/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 EC 50 of 28.6, in addition to chromosome aberrations in 40% of dividing cells for the treated wastewater. 相似文献
3.
Crop residues with high C/N ratio immobilize N released during decomposition in soil, thus reducing N losses through leaching,
denitrification, and nitrous oxide (N 2O) 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 N 2O 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 NO 3−–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 NO 3−–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 N 2O from crop residue amended soils occurred in the first 4–5 days of incubation. Overall, after 84 days of incubation, the
cumulative N 2O emission was 25% lower with cotton + N fertilizer, compared to soil + N fertilizer. The cumulative N 2O emission was significantly and positively correlated with NO 3−–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 CO 2 in the first 3 and 5 days of incubation ( r = 0.59, P < 0.05). 相似文献
4.
We compared, from 2004 through 2006, rates of soil–atmosphere CH 4 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) CO 2 since August 1996. A total of 880 observations showed net atmospheric CH 4 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 CH 4 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 CH 4 consumption in control plots was higher than the mean for CO 2-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 CH 4 consumption at control plots during the three calendar years of this study were 19, 10, and 8% higher than comparable values
for CO 2 enriched plots. Differences between treatments were significant in 2004 and 2005 and nearly significant in 2006. Volumetric
soil water content was consistently higher at CO 2-enriched sites and a mixed-effects model identified a significant soil moisture x CO 2 interaction on net atmospheric CH 4 consumption. Increased soil moisture at CO 2-enriched sites likely increases diffusional resistance of surface soils and the frequency of anaerobic microsites supporting
methanogenesis, resulting in reduced rates of net atmospheric CH 4 consumption. Our study extends our observations of reduced net atmospheric CH 4 consumption at CO 2-enriched plots to nearly five continuous years, suggesting that this is likely a sustained negative feedback to increasing
atmospheric CO 2 at this site. 相似文献
5.
Temporal depositional rates are important in order to understand the production and occurrence of perchlorate (ClO 4−) as limited information exists regarding the impact of anthropogenic production or atmospheric pollution on ClO 4− 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 ClO 4
− 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 ClO 4
− 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 ClO 4
− 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 ClO 4− with SO 42− was found for the annual UFG ice core layers and of ClO 4
− with SO 42− and NO 3− in sub-annual Eclipse ice samples ( R > 0.3, N = 121, p < 0.002). The estimated yearly ClO 4− 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 ClO 4− depositional flux for the Eclipse ice core, in contrast to a previous study on the Arctic region. The presence of ClO 4− 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 ClO 4− formation. 相似文献
6.
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 (CO 2) 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 CO 2 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
7.
PurposeImidacloprid is a widely used seed dressing insecticide in Brazil. However, the effects of this pesticide on non-target organisms such as soil fauna still present some knowledge gaps in tropical soils. This study aimed to assess the toxicity and risk of imidacloprid to earthworms Eisenia andrei and collembolans Folsomia candida in three contrasting Brazilian tropical soils. Materials and methodsAcute and chronic toxicity assays were performed in the laboratory with both species in a tropical artificial soil (TAS) and in two natural soils (Oxisol and Entisol), at room temperature of 25 °C. The ecological risk was calculated for each species and soil by using the toxicity exposure ratio (TER) and hazard quotient (HQ) approaches. Results and discussionAcute toxicity for collembolans and earthworms was higher in Entisol (LC50?=?4.68 and 0.55 mg kg?1, respectively) when compared with TAS (LC50?=?10.8 and 9.18 mg kg?1, respectively) and Oxisol (LC50collembolans?=?25.1 mg kg?1). Chronic toxicity for collembolans was similar in TAS and Oxisol (EC50 TAS?=?0.80 mg kg?1; EC50 OXISOL?=?0.83 mg kg?1), whereas higher toxicity was observed in Entisol (EC50?=?0.09 mg kg?1). In chronic assays with earthworms, imidacloprid was also more toxic in Entisol (EC50?=?0.21 mg kg?1) when compared to TAS (EC50?=?1.89 mg kg?1). TER and HQ values indicated a significant risk of exposure of the species to imidacloprid in all soils tested, and the risk in Entisol was at least six times higher than in Oxisol or TAS. ConclusionsThe toxicity and risk of imidacloprid varied significantly between tropical soils, being the species exposure to this pesticide particularly hazardous in very sandy natural soils such as Entisol. 相似文献
8.
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 (C Org), and extractable C, total N and P, and exchangeable ions (Ca 2+, Mg 2+, K +, Na +, Cl −, and CO 32−), microbial biomass (C mic). The Na + and Cl − concentrations were 36-80% higher in strongly saline compared to weakly saline soil. The C Org concentration was decreased by 10% and C Ext by 40% by increasing soil salinity, whereas decrease in C mic ranged from 18-42% and the percentage of C Org present as C mic 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
9.
Consumer demand for cleaned squid generates a substantial amount of waste that must be properly disposed of, creating an economic
burden on processors. A potential solution to this problem involves converting squid by-products into an organic fertilizer,
for which there is growing demand. Because fertilizer application to lawns can increase the risk of nutrient contamination
of groundwater, we quantified leaching of NO 3–N and PO 4–P from perennial ryegrass turf ( Lolium perenne L.) amended with two types of fertilizer: squid-based (SQ) and synthetic (SY). Field plots were established on an Enfield
silt loam, and liquid (L) and granular (G) fertilizer formulations of squid and synthetic fertilizers were applied at 0, 48,
146, and 292 kg N ha −1 year −1. Levels of NO 3–N and PO 4–P in soil pore water from a depth of 60 cm were determined periodically during the growing season in 2008 and 2009. Pore
water NO 3–N levels were not significantly different among fertilizer type or formulation within an application rate throughout the
course of the study. The concentration of NO 3–N remained below the maximum contaminant level (MCL) of 10 mg L −1 until midSeptember 2009, when values above the MCL were observed for SQG at all application rates, and for SYL at the high
application rate. Annual mass losses of NO 3–N were below the estimated inputs (10 kg N ha −1 year −1) from atmospheric deposition except for the SQG and SYL treatments applied at 292 kg N ha −1 year −1, which had losses of 13.2 and 14.9 kg N ha −1 year −1, respectively. Pore water PO 4–P levels ranged from 0 to 1.5 mg P L −1 and were not significantly different among fertilizer type or formulation within an application rate. Our results indicate
that N and P losses from turf amended with squid-based fertilizer do not differ from those amended with synthetic fertilizers
or unfertilized turf. Although organic in nature, squid-based fertilizer does not appear to be more—or less—environmentally
benign than synthetic fertilizers. 相似文献
10.
Perchlorate (ClO 4−), 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 ClO 4− is considered to be the result of atmospheric formation and deposition processes. The ultimate processes, particularly heterogeneous-based
reactions, leading to natural ClO 4− 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 ClO 4−. Currently, there is very little information available on lightning-induced ClO 4−. We designed a laboratory electrical discharge reactor capable of evaluating ClO 4− 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 ClO 4− production processes, the amount of ClO 4− produced (0.5–4.8 μg) was 3 orders of magnitude lower than the input Cl − (7.1–60.1 mg). The amount of ClO 4− generated increased with peak voltage (V) and theoretical maximum discharge energy with ΔClO 4−/ΔV = 0.28 × 10 −3 μg V −1 ( R
2 = 0.94) and ΔClO 4−/ΔE = 0.44 × 10 −3 μg J −1 ( R
2 = 0.83). The total ClO 4− 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 ClO 4−. Additional modifications to the reactor support the hypothesis of ClO 4− 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
ClO 4− in North America is calculated to have a wide range from 0.006 × 10 5 to 5 × 10 5 kg/year and is within the range of the measured ClO 4− depositional flux in precipitation samples obtained across the USA (0.09 × 10 5–1.2 × 10 5 kg/y). 相似文献
11.
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 Cd 2+ and Ni 2+ at different concentrations of Ca 2+ and Mg 2+, 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 Cd 2+, Ni 2+ and EDTA on the maximum specific growth rate and the determination of EC50 values was used to quantify inhibitory impact.
At high concentrations of Ca 2+ (800 μmol L -1) and Mg 2+ (1,250 μmol L -1), only a small inhibitory effect of Cd 2+ and Ni 2+ on growth of P. brassicacearum was observed (EC50 Cd 2+, 18,849 ± 80 μmol L −1; EC50 Ni 2+, 3,578 ± 1,002 μmol L −1). The inhibition was much greater at low concentrations of Ca 2+ (25 μmol L −1) and Mg 2+ (100 μmol L −1) (EC50 Cd 2+, 85 ± 0.5 μmol L −1 and EC Ni 2+, 62 ± 1.8 μmol L −1). For the chosen model system, a competitive effect of the ions Cd 2+ and Ca 2+ on the one hand and Ni 2+ and Mg 2+ on the other hand can be deduced. However, the toxicity of both, Cd 2+ and Ni 2+, 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
12.
Purpose The effects of the addition of an acidic fertilizer solution and/or slaked lime (5.5 g Ca(OH) 2 kg −1) on a slightly acidic shooting range soil (pH 6.1, % organic carbon 5.4) with moderate metal (e.g., 620 mg kg −1 Pb) and metalloid (17 mg kg −1 Sb) concentrations on metal and Sb solubility and plant accumulation were investigated. 相似文献
13.
The toxicity of pure phenol, formaldehyde, and industrial wastewater, containing phenol and formaldehyde, from a resin production plant was evaluated using aquatic organisms from different taxonomic groups. Test organisms included mixed bacterial culture, unicellular green algae Scenedesmus quadricauda (Turp.) Breb., crustacea Daphnia pulex de Geer (daphnids), and fish Oncorhynchus mykiss Call, 1990 (rainbow trout). Formaldehyde was found to be more toxic to the mixed bacterial culture (120h EC 50 = 34.1 mg L -1), algae (24h EC 50 = 14.7 mg L -1), and crustacea (48h EC 50 = 5.8 mg L -1) than phenol. Phenol proved to be more toxic to fish (48h LC 50 = 13.1 mg L -1) than to the mixed bacterial culture (120h EC 50 = 510 mg L -1), algae (24h EC 50 = 403 mg L -1), and crustacea (48h EC 50 = 25 mg L -1). The toxicity of the industrial wastewater to the mixed bacterial culture, algae, and crustacea was caused mainly by formaldehyde, but for fish the presence of phenol in the wastewater proved to be the significant reason for toxicity. Differences in sensitivity of the selected test organisms were also observed, with fish and crustacea being the most sensitive species. 相似文献
14.
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 (NO 3−, CO 32− 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 NO 3− > CO 32− ≅ DOC, with the highest rates observed in the 3 mM NO 3− 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 NO 3− on a non-photolabile pesticide, with indirect photodegradation probably attributable to the light-induced release of aqueous
hydroxyl radicals ( ·OH) from NO 3−. 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
15.
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 (N 2O + N 2)–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 (N 2O + N 2)–N from oligotrophic, mesotrophic, and transitional peats were markedly increased by the addition of 0.15 g NO 3–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 (N 2O + N 2)–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
16.
We investigated Cd, Zn, and Cd + Zn toxicity to soil microbial biomass and activity, and indigenous Rhizobium leguminosarum biovar trifolii, in two near neutral pH clay loam soils, under long-term arable and grassland management, in a 6-month laboratory incubation,
with a view to determining the causative metal. Both soils were amended with Cd- or Zn-enriched sewage sludge, to produce
soils with total Cd concentrations at four times (12 mg Cd g −1 soil), and total Zn concentrations (300 mg Zn kg −1 soil) at the EU upper permitted limit. The additive effects of Cd plus Zn at these soil concentrations were also investigated.
There were no significant differences in microbial biomass C ( B
C), biomass ninhydrin N ( B
N), ATP, or microbial respiration between the different treatments. Microbial metabolic quotient (defined as qCO 2 = units of CO 2–C evolved unit −1 biomass C unit −1 time) also did not differ significantly between treatments. However, the microbial maintenance energy (in this study defined
as qCO 2-to- μ ratio value, where μ is the growth rate) indicated that more energy was required for microbial synthesis in metal-rich sludge-treated soils (especially
Zn) than in control sludge-treated soils. Indigenous R.
leguminosarum bv. trifolii numbers were not significantly different between untreated and sludge-treated grassland soils after 24 weeks regardless of
metal or metal concentrations. However, rhizobial numbers in the arable soils treated with metal-contaminated sludges decreased
significantly ( P < 0.05) compared to the untreated control and uncontaminated sludge-treated soils after 24 weeks. The order of decreasing
toxicity to rhizobia in the arable soils was Zn > Cd > Cd + Zn. 相似文献
17.
Simple and rapid chemical indices of soil nitrogen (N)-supplying capacity are necessary for fertilizer recommendations. In
this study, pot experiment involving rice, anaerobic incubation, and chemical analysis were conducted for paddy soils collected
from nine locations in the Taihu Lake region of China. The paddy soils showed large variability in N-supplying capacity as
indicated by the total N uptake (TNU) by rice plants in a pot experiment, which ranged from 639.7 to 1,046.2 mg N pot −1 at maturity stage, representing 5.8% of the total soil N on average. Anaerobic incubation for 3, 14, 28, and 112 days all
resulted in a significant ( P < 0.01) correlation between cumulative mineral NH 4+-N and TNU, but generally better correlations were obtained with increasing incubation time. Soil organic C, total soil N,
microbial C, and ultraviolet absorbance of NaHCO 3 extract at 205 and 260 nm revealed no clear relationship with TNU or cumulative mineral NH 4+-N. Soil C/N ratio, acid KMnO 4-NH 4+-N, alkaline KMnO 4-NH 4+-N, phosphate–borate buffer extractable NH 4+-N (PB-NH 4+-N), phosphate–borate buffer hydrolyzable NH 4+-N (PB HYDR-NH 4+-N) and hot KCl extractable NH 4+-N (H KCl−NH 4+-N) were all significantly ( P < 0.05) related to TNU and cumulative mineral NH 4+-N of long-term incubation (>28 days). However, the best chemical index of soil N-supplying capacity was the soil C/N ratio,
which showed the highest correlation with TNU at maturity stage ( R = −0.929, P < 0.001) and cumulative mineral NH 4+-N ( R = −0.971, P < 0.001). Acid KMnO 4-NH 4+-N plus native soil NH 4+-N produced similar, but slightly worse predictions of soil N-supplying capacity than the soil C/N ratio. 相似文献
18.
This work aims to identify and characterize heavy metal contamination in a fluvial system from Cartagena–La Unión mining district
(SE Spain). In order to assess the dynamics of transport and the accumulation of heavy metals, sediments, surface water and
vegetation, samples along “El Avenque” stream were collected. The former direct dumps of wastes and the presence of tailing
ponds adjacent to the watercourse have contributed to the total contamination of the stream. Total Cd (103 mg kg −1), Cu (259 mg kg −1), Pb (26,786 mg kg −1) and Zn (9,312 mg kg −1) in sediments were above the limits of European legislation, being highest where tailing ponds are located. Bioavailable
metals were high (3.55 mg Cd kg −1, 6.45 mg Cu kg −1, 4,200 mg Pb kg −1 and 343 mg Zn kg −1) and followed the same trend than total contents. Metals in water were higher in sampling points close to ponds, exceeding
World Health Organization guidelines for water quality. There is a direct effect of solubilisation of sediment metals in water
with high contents of SO 42−, product of the oxidation of original sulphides. The mobility of metals varied significantly with shifts in pH. Downstream,
available and soluble metals concentrations decreased mainly due to precipitation by increments in pH. As a general pattern,
no metal was bioaccumulated by any tested plant. Thus, native vegetation has adopted physiological mechanisms not to accumulate
metals. This information allows the understanding of the effect of mining activities on stream contamination, enforcing the
immediate intervention to reduce risks related to metals’ mobility. 相似文献
19.
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 NO X–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 ≤10 9 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
20.
The abandonment of cultivated wetland soil increased the contents of light fraction organic matter (LFOM), heavy fraction
organic matter (HFOM) and soil organic matter (SOM). The LFOM and HFOM content increased to 13.3 g kg −1 and 62.4 g kg −1 after 5 years whereas they were 8.4 and 47.9 g kg −1 after 9 years of cropping, respectively. Fourteen years after abandonment, HFOM content increased to 104.3 g kg −1. LFOM was positively correlated with HFOM ( p < 0.001). A Langmuir equation was used to calculate the highest HFOM value. The value for the natural wetland soil was closed
to this theoretical value (140.8 g kg −1). After 14 years of abandonment, the HFOM maximum (HFOM Max) value was lower than the equilibrium value suggesting that a further increase in HFOM can occur after abandonment. Assuming
a linear accumulation (3.87 Mg C ha −1yr −1), it would take approximately 24 years after the abandonment to reach the HFOM Max value. 相似文献
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