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1.
Iron (Fe) nanoparticles (NPs), with 30–40 nm diameter, were stabilized on sand. The resulting synthesized Fe/SiO2 NPs, with different Fe contents (0–25 mg kg?1) were employed as fertilizers in probing the mean germination time (MGT), growth and dry matter of barley and maize and their comparison with common Fe/SiO2 in a completely randomized design (CRD) experiment. The results showed that our fertilizers had significant effects on MGT, with the lowest of 0.58 day for barley and 0.79 day for maize; at 15 and 5 mg kg?1 nano Fe/SiO2, respectively. Application of 15 mg kg?1 of nano Fe/SiO2 increased the shoot length: 8.25% and 20.8% for barley and maize, respectively. However, the concentration of 25 mg kg?1 had a negative impact on shoot length in barley. Increasing the concentrations of both nano and common Fe/SiO2 particles, increased the root lengths in both plants, however this increase was higher with the application of nano Fe/SiO2. Likewise, seedling length enlarged with the concentration increase of both Fe/SiO2 particles and was more pronounced with nano Fe/SiO2. The application of nano Fe/SiO2 was more effective compared with the common Fe/SiO2 in encouraging barley and maize growth. The positive impact was higher in maize than barley.  相似文献   

2.
The adsorption of heavy metals [cadmium (Cd 2+), cobalt (Co2+), nickel (Ni2+), zinc (Zn2+), and lead (Pb)] and calcium (Ca2+) on humic acid and silica were investigated to understand the adsorptive selectivities of heavy metals on the constituents of soil. The experiments for the adsorption of Cd and Pb were carried out in a 0.1 mol L?1 (M) sodium nitrate (NaNO3) background solution, whereas those for the other metals were done in a 0.1 M sodium chloride (NaCl) solution. The adsorptive affinities of the metal ions on the humic acid and silica were ranked by the intrinsic surface complexation constants [K m 1(int)] that were calculated approximately from the adsorptive data using a constant capacitance model. The log [K m 1(int)] values of the metals were in the order Zn2+(?2.29) > Cd2+(?2.41) > Co2+(?2.74) > Ni2+(?2.92) ?> Ca2+ (?3.33) for the humic acid and Zn2+(?4.23) > Cd2+(?4.49) > Ni2+(?4.51) ? Co2+ (?5.99) > Ca2+(?6.37) for silica.  相似文献   

3.
An experiment was established to assess the ability of selenium (Se) to reduce cadmium (Cd) toxicity when tomato was grown hydroponically. A factorial experiment was arranged in a completely randomized design with six replicates in cucumber (Cucumis sativus cv. 4200). The Se was applied at four levels [0 mg L–1 (Se0), 2 mg L–1 Se (Se1), 4 mg L–1 Se (Se2), and 6 mg L–1 Se (Se3)], whereas Cd was applied at three levels [0 µM Cd (Cd0), 5 µM Cd (Cd1), and 7 µM Cd (Cd2)]. The Se improved the dry weight of roots even when plants were exposed to Cd. Treatment Se1 improved the dry weight of shoots in Cd1 and Cd2. Treatments Se1 and Se2 improved photosynthesis in Cd1. Treatment Se1 significantly improved stomatal conductance in Cd2 at all levels of Se relative to Cd2. The greatest Cd concentration in leaves was observed in Cd2 × Se0 and while Se concentration in solution increased in response to Se1, Se2, and Se3. The greatest Se level reduced Cd uptake the most. Growth and photosynthetic attributes can be negatively affected by Cd, but Se has the ability to buffer, or improve, several attributes.  相似文献   

4.
The use of multiwall carbon nanotubes (MWCNT) as an efficient solid extractor in preconcentration/cleanup studies for tin determination in water samples by electrothermal atomic absorption spectrometry (ETAAS) is proposed. In the proposed method, tin adsorption onto MWCNT was carried out by percolating the solution previously buffered (pH 4.79 with 0.24 mol?L?1 acetic acid/acetate buffer) at 4.0-mL?min?1 flow rate, followed by elution with 1.0 mL of 2.7 mol?L?1 HNO3. Factors such as sample pH, preconcentration/cleanup flow rate, type and concentration of eluent, and buffer concentration were appraised and optimized from chemometric tools based on fractional factorial design and Doehlert design. A limit of detection of 0.73 ??g?L?1 and precision (n?=?8) assessed as relative standard deviation of 8.6% and 7.0% for tin concentration of 8.0 and 43.0 ??g?L?1, respectively, were achieved. Foreign metallic ions (Ni2+, Pb2+, Co2+, Zn2+, Cd2+, Mn2+, and Fe3+) were checked as potential interferents, and no interference was observed up to an analyte/interference ratio of 1:10 (m/v). Direct tin determination by ETAAS in water samples containing high salt amount is drastically affected by background signal. However, previous cleanup of sample by MWCNT has promoted a significant improvement and makes the method useful for tin monitoring in water samples (mineral, lake, mine, and natural waters) by ETAAS. Quantitative recovery values ranging from 91.5% to 103.0% attested the applicability of the proposed preconcentration/cleanup for tin determination in water samples.  相似文献   

5.
The effectiveness of lime-ammonium-nitrate (LAN) as a nitrogen (N) fertilizer in weathered soils depends on the respective selectivity for ammonium (NH4) and calcium (Ca) by the soils. The study assessed Ca2+/NH4+ exchange selectivity of two benchmark soils from Botswana and examined the soil fertility management implications. Surface horizons (0–20 cm) of Pellustert and Haplustalf were equilibrated with 50 ml stock solution containing variable concentrations of Ca2+ and NH4+. The Ca2+/NH4+ exchange data were fitted into the Vanselow (KV), Gaines and Thomas (KGT), Davies (KD), and the regular solution (KRS) equations. The selectivity coefficients for the Ca2+/NH4+ exchange reactions varied widely with the soil exchanger composition except for the relatively stable KRS. The selectivity coefficients indicated strong preference for NH4+ to Ca2+. The thermodynamic exchange constant, Kex, was 5.75 ± 1.24 in the Pellustert, indicating preferential adsorption of NH4+, but not in the Haplustalf with Kex = 0.92 ± 0.27. The free energy for Ca2+/NH4+ exchange (ΔG°ex) was negative (?4.26 ± 0.59 kJ mol?1) in the Pellustert but slightly positive in the Haplustalf (0.34 ± 0.87 kJ mol?1). In conclusion, the soil-NH4 complex was more stable than soil-Ca complex in the Pellustert, indicating LAN as a N fertilizer would have greater potential effectiveness in the Pellustert than in the Haplustalf.  相似文献   

6.
In the present study, a method based on dispersive liquid–liquid microextraction (DLLME) followed by graphite furnace atomic absorption spectrometry (GFAAS) determination was proposed for the determination of selenium by using ammonium pyrrolidine dithiocarbamate (APDC) as the chelating reagent. The main factors influencing the DLLME were investigated systematically. Under the optimal conditions, the limit of detection for Se(IV) was 0.02 ng mL?1. The relative standard deviation was 4.1% (CSe(IV) = 0.2 ng mL?1, n = 8) with an enhancement factor of 135.8-fold from only 5 mL of the water sample. The proposed method was successfully applied to the determination of Se(IV) in anodic slime and electrolyte samples. In order to validate the proposed method, a Certified Reference Material (trace elements in water, 1643e, NIST) was analyzed, and the determined value obtained was in good agreement with the certified value.  相似文献   

7.
Abstract

Forest fires can change the greenhouse gase (GHG) flux of borea forest soils. We measured carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) fluxes with different burn histories in black spruce (Picea mariana) stands in interior Alaska. The control forest (CF) burned in 1920; partially burned (PB) in 1999; and severely burned (SB1 and SB2) in 2004. The thickness of the organic layer was 22 ± 6 cm at CF, 28 ± 10 cm at PB, 12 ± 6 cm at SB1 and 4 ± 2 cm at SB2. The mean soil temperature during CO2 flux measurement was 8.9 ± 3.1, 6.4 ± 2.1, 5.9 ± 3.4 and 5.0 ± 2.4°C at SB2, SB1, PB and CF, respectively, and differed significantly among the sites (P < 0.01). The mean CO2 flux was highest at PB (128 ± 85 mg CO2-C m?2 h?1) and lowest at SB1 (47 ± 19 mg CO2-C m?2 h?1) (P < 0.01), and within each site it was positively correlated with soil temperature (P < 0.01). The CO2 flux at SB2 was lower than that at CF when the soil temperature was high. We attributed the low CO2 flux at SB1 and SB2 to low root respiration and organic matter decomposition rates due to the 2004 fire. The CH4 uptake rate was highest at SB1 [–91 ± 21 μg CH4-C m?2 h?1] (P < 0.01) and positively correlated with soil temperature (P < 0.01) but not soil moisture. The CH4 uptake rate increased with increasing soil temperature because methanotroph activity increased. The N2O flux was highest [3.6 ± 4.7 μg N2O-N m?2 h?1] at PB (P < 0.01). Our findings suggest that the soil temperature and moisture are important factors of GHG dynamics in forest soils with different fire history.  相似文献   

8.
ABSTRACT

Elevated concentrations of carbon dioxide (e[CO2]) affect plant growth and physiological characteristics, including metal accumulation, and the activity of anti-oxidant enzymes. These effects were investigated in cadmium (Cd) tolerant wheat (Triticum aestivum L.) and sorghum (Sorghum bicolor (L.) Moench.) cultivars. Plants were grown at the ambient and elevated CO2 levels, with four concentrations of Cd (0, 10, 20 and 40 mg kg?1) added to the soil. After 60 days, subsamples were tested for chlorophylls and carotenoids, protein, enzyme activities and morphological characteristics.

Results showed that e[CO2] increased plant height, leaf area, and the dry weight of shoots and roots (P < 0.01). In addition, it decreased the Cd concentration in the shoots and roots of wheat, and increased the same concentrations for sorghum. With increasing Cd, the activities of the anti-oxidants, SOD and GSH-px increased in wheat. The differences in enzyme activity parallel the changes in Cd concentration in the plants of both species.  相似文献   

9.
We analyzed in soils with contrasting cultivation histories the depletion of P following sequential extractions with soil testing solutions. Soil samples were collected in three experiments in eastern Canada (L’Acadie, Lévis, and Normandin) and P was sequentially extracted 16 times, once daily, using Mehlich-3 (M3) or Olsen (Ol) solution. The cumulative amount of P extracted was 252 mg PM3 kg?1 and 77 mg kg?1 POl for L’Acadie, 212 mg PM3 kg?1 and 66 mg POl kg?1 for Lévis, and 424 mg PM3 kg?1 and 83 mg POl kg?1 for Normandin. The depletion of P was described by a logarithmic function (Y = a ln (N) + b) for PM3, and a power function (Y = αNβ) for POl. The inorganic P pool decreased in the three soils. The organic P pool did not decrease possibly because soil testing solutions did not directly extract P from this pool. This study demonstrated that laboratory soil testing analysis using M3 or Ol solution principally target P from the inorganic pool, suggesting that P fertilizer recommendations to mineral soils relying on these methods do not account for the potential of the organic P pool to contribute to soil P availability.  相似文献   

10.
Abstract

Wheat grown on cadmium (Cd)‐uncontaminated soils can still potentially translocate unacceptable levels of Cd to grain. The effect of zinc (Zn) and Cd levels on Cd uptake and translocation in “Grandin” hard red spring wheat (HRS‐wheat) (Triticum aestivum L.) was investigated using a double chelator‐buffered nutrient solution [EGTA used to buffer Cd, Zn, copper (Cu), manganese (Mn), and nickel (Ni); and Ferrozine (FZ) used to buffer Fe2+]. In the Zn level series of treatments, Cd2+ activity was held constant at 10?10.7 M, and the Zn2+ activity was varied from 10?7.6 to 10?5.2 M. As Zn2+ activity increased, the translocation of Cd to the shoots decreased. The shoot : root Cd concentration ratio decreased from 0.20 to 0.03 as pZn2+ went from 7.6 to 5.2, indicating that adequate to high levels of Zn are effective in reducing Cd translocation to the shoots of “Grandin” HRS‐wheat. In the Cd series, the Zn activity was at 10?6.6 M, while Cd activity was increased from 10?10.7 to 10?9.2 M. High levels of Cd did not significantly affect the uptake and translocation of Zn in the roots and shoots. While at pCd2+ of 9.2, the root and shoot Cd concentrations significantly increased, there was not a significant increase in the shoot : root Cd ratio. This would indicate that even at high Cd2+ activities, Zn is effective in regulating Cd uptake and translocation in “Grandin” HRS‐wheat.  相似文献   

11.
Yellow lupin (Lupinus luteus L.) and narrow-leafed lupin (L. angustifolius L.) are grown as grain legumes in rotation with spring wheat (Triticum aestivum L.) on acidic sandy soils of south-western Australia. Yellow lupin can accumulate significantly larger cadmium (Cd) concentrations in grain than narrow-leafed lupin. A glasshouse experiment was undertaken to test whether adding increasing zinc (Zn) levels to soil increased Zn uptake by yellow lupin reducing accumulation of Cd in yellow lupin grain. Two cultivars of yellow lupin (cv. ‘Motiv’ and ‘Teo’) and 1 cultivar of narrow-leafed lupin (cv. ‘Gungurru’) were used. The soil was Zn deficient for grain production of both yellow and narrow-leafed lupin, but had low levels of native soil Cd (total Cd <0.05 mg kg?1) so 1.6 mg Cd pot?1, as a solution of cadmium chloride (CdCl2·H2O), was added and mixed through the soil. Eight Zn levels (0–3.2 mg Zn pot?1), as solutions of zinc sulfate (ZnSO4·7H2O), were added and evenly mixed through the soil. Yellow lupin accumulated 0.16 mg Cd kg?1 in grain when no Zn was applied, which decreased as increasing Zn levels were applied to soil, with ～0.06 mg Cd kg?1 in grain when the largest level of Zn (3.2 mg Zn pot?1) was applied. Low Cd concentrations (<0.016 mg Cd kg?1) were measured in narrow-leafed lupin grain regardless of the Zn treatment. When no Zn was applied, yellow lupin produced ～2.3 times more grain than narrow-leafed lupin, indicating yellow lupin was better at acquiring and using indigenous Zn from soil for grain production. Yellow lupin required about half as much applied Zn as narrow-leafed lupin to produce 90% of the maximum grain yield, ～0.8 mg pot?1 Zn compared with ～1.5 mg Zn pot?1. Zn concentration in whole shoots of young plants (eight leaf growth stage) related to 90% of the maximum grain yield (critical prognostic concentration) was (mg Zn kg?1) 25 for both yellow lupin cultivars and 19 for the narrow-leafed lupin cultivar. Critical Zn concentration in grain related to 90% of maximum grain yield was (mg Zn kg?1) 24 for both yellow lupin cultivars compared with 20 for the narrow-leafed lupin cultivar.  相似文献   

12.
Abstract

The effect of cadmium (Cd) and sulphur (S) on dry weight, biochemical parameters and anatomical features of mustard (Brassica campestris L. cv. Pusa Bold) plant was investigated in a pot culture experiment using Cd (25, 50, and 100 mg kg?1 of soil), S (40 mg kg?1 of soil), and the combination of Cd+S (25+40 mg kg?1 of soil, 50+40 mg kg?1 of soil, and 100+40 mg kg?1 of soil). Sulphur treatment was given at sowing and Cd treatment was given when seedlings were fully established. Observations were recorded at the flowering stage. A significant and antagonistic interaction of Cd and S was observed. Compared to the control, leaf dry weight, total chlorophyll content, sugar content, nitrate reductase activity, and protein content decreased significantly with each Cd treatment, whereas the reverse was observed with S treatment. Combined treatments of Cd+S also reduced these parameters, but this reduction was less than the one observed with Cd treatments alone. However, nitrate accumulation in the leaves was 2.35 times higher with treatment of 100 mg Cd+40 mg S kg?1 of soil than in the controls, whereas it was 3.5 times higher with Cd (100 mg kg?1 of soil) alone. The relative proportion of vasculature in the stem, stoma length and width, and stomata length and width were inhibited with Cd treatments, whereas the combined treatments mitigated the adverse effect caused by Cd. Thus, S could alleviate the Cd induced impairment of biochemical and anatomical features of the plant and the enhancement of nitrate accumulation in the leaves.  相似文献   

13.
Chinese cabbage and surface soil samples (0–20 cm) from a periurban market garden in Yunnan Province (P.R. China) were collected to determine variations of cadmium (Cd) and zinc (Zn) contents in Chinese cabbage and the influence of soil factors. Mean Cd content was 0.49 mg kg?1 dry materials (DM) in Chinese cabbage, ranging between 0.23 and 1.34 mg kg?1 DM (n = 21 samples). Mean Zn content was 51.2 mg kg?1 DM, ranging from 34.9 to 157.5 mg kg?1 DM (n = 21 samples). The soil factors best predicting Chinese cabbage Cd and Zn contents were total and available Cd and Zn contents and cation exchange capacity (CEC). Soil samples and corresponding Chinese cabbage samples were divided into two groups: soils with low pH (<6.5, n = 10) and soils with high pH (>6.5, n = 11). Positive correlation between CEC with pH > 6.5 and Cd and Zn contents in Chinese cabbage were observed. Available trace element contents and CEC explained 77% and 69% of variation of Cd and Zn contents in Chinese cabbage, respectively. AEC (enrichment coefficient related to trace element availability) and BCF (bioaccumulation factors) could be used to understand Cd and Zn accumulation in Chinese cabbage.  相似文献   

14.
Agricultural soils are a primary source of anthropogenic trace gas emissions, and the subtropics contribute greatly, particularly since 51% of world soils are in these climate zones. A field experiment was carried out in an ephemeral wetland in central Zimbabwe in order to determine the effect of cattle manure (1.36% N) and mineral N fertilizer (ammonium nitrate, 34.5% N) application on N2O fluxes from soil. Combined applications of 0 kg N fertilizer + 0 Mg cattle manure ha?1 (control), 100 kg N fertilizer + 15 Mg manure ha?1 and 200 kg N fertilizer + 30 Mg manure ha?1 constituted the three treatments arranged in a randomized complete block design with four replications. Tomato and rape crops were grown in rotation over a period of two seasons. Emissions of N2O were sampled using the static chamber technique. Increasing N fertilizer and manure application rates from low to high rates increased the N2O fluxes by 37–106%. When low and high rates were applied to the tomato and rape crops, 0.51%, 0.40%, and 0.93%, 0.64% of applied N was lost as N2O, respectively. This implies that rape production has a greater N2O emitting potential than the production of tomatoes in wetlands.  相似文献   

15.
In an incubation experiment with flooded rice soil fertilized with different N amounts and sampled at different rice stages, the methane (CH4) and carbon dioxide (CO2) production in relation to soil labile carbon (C) pools under two temperature (35°C and 45°C) and moisture (aerobic and submerged) regimes were investigated. The field treatments imposed in the wet season included unfertilized control and 40, 80 and 120 kg ha?1 N fertilization. The production of CH4 was significantly higher (27%) under submerged compared to aerobic conditions, whereas CO2 production was significantly increased under aerobic by 21% compared to submerged conditions. The average labile C pools were significantly increased by 21% at the highest dose of N (120 kg ha?1) compared to control and was found highest at rice panicle initiation stage. But the grain yield had significantly responded only up to 80 kg ha?1 N, although soil labile C as well as gaseous C emission was noticed to be highest at 120 kg ha?1 N. Hence, 80 kg N ha?1 is a better option in the wet season at low land tropical flooded rice in eastern India for sustaining grain yield and minimizing potential emission of CO2 and CH4.  相似文献   

16.
In this study, cobalt magnetic nanoparticles (MNPs) were synthesized and then modified by sodium dodecyl sulfate (SDS) and 2-(5-bromo-2-pyridylazo)-5-diethyl aminophenol ligand (5-Br-PADAP), through a chemical precipitation method. Characterization of the prepared MNP adsorbents was performed by Fourier transform infrared and transmission electron microscopy. Cobalt nanoparticles (NPs) surface modified with SDS and 5-Br-PADAP was evaluated as a nanoparticulate solid-phase extraction (SPE) absorbent for lead ions Pb(II) from water and standard samples, prior to its flame atomic absorption spectrometry determination. Effects of pH, amount of sorbent, desorption solvent, adsorption time, desorption time, and interfering ion concentration on extraction efficiency were investigated. Under optimal conditions, the calibration curve was linear in the range of 1.0–500 ng mL?1of Pb(II) with R2 = 0.998. Detection limit was 1.6 ng mL?1 in the original solution (3Sb/m), and the relative standard deviation for replicate determination of 0.5 μg mL?1 Pb(II) was ±2.7%.  相似文献   

17.
Determining potassium (K) fertilizer requirement using sorption isotherms is considered more accurate than conventional soil K tests. A total of 59 surface soil samples were used to establish K exchange isotherm. To evaluate K requirement sorption test, a glasshouse experiment using perennial ryegrass (Lolium perenne, cv. Roper) was carried out on 10 soil samples. The experiment was laid out as a completely randomized design with four replications and four K levels (K0, K20, K40, K80). Concentrations of K in solution established by adding K in the pots estimated from the sorption curve ranged from 20 to 80 mg K l?1 including check treatment (no K). Dry matter yield of ryegrass in most soils approached maximum as adjusted K levels were increased to 20 mg K l?1. The amounts of K required to bring the soils to 20 mg l?1 in soil solution varied among soils and ranged from 99 to 399 mg kg?1, on average 205 mg kg?1 soil. It was found that a useful regression model for the prediction of standard K requirement (K20) included the combination of plant available K extracted by NH4OAc (Av-K) and clay content: K20 = ?41 ? 0.63 Av-K + 9.0 Clay (R2 = 0.61, p < 0.001, n = 59).  相似文献   

18.
Abstract

Growth response of a halophyte species, Suaeda salsa (L.) Pall, to graded NaCl concentrations was examined under water culture conditions. Growth increased with increasing NaCl concentration from 2 to 200 mol m?3, but decreased at NaCl concentrations above 200 mol m?3. Maximum growth was attained at 50 to 200 mol m?3. The role of Na and Cl in the growth stimulation by NaCl was examined by growing S. salsa in nutrient solutions with or without Na and Cl separately at 5 and 50 mol m?3. The growth stimulation induced by Cl was greater than that induced by Na, and Na did not significantly induce growth stimulation. The effect of Na or Cl on O2 evolution from leaves was examined under 5 and 50 mol m?3 concentrations using an oxygen electrode. Oxygen evolution from leaves in –Cl treatments was smaller than that in +Cl treatments both at 5 and 50 mol m?3. The O2 evolution in Na treatments with Cl was similar to that at NaCl. These results indicated that the mechanism of growth stimulation induced by Cl was mainly an increased photosystem II of photosynthesis in leaves. The contribution of Na on the growth stimulation of S. salsa by NaCl was smaller than Cl.  相似文献   

19.
Abstract

A sequential injection system for the determination of nitrate (NO3 ?) in vegetables was developed to automate this determination, allowing for substantially reduced reagent consumption and generated waste using low‐cost equipment. After extraction with water and filtration, the extracted nitrate is reduced inline to nitrite in a copperized cadmium (Cd) column and determined as nitrite. According to the Griess–Ilosvay reaction, nitrate is diazotized with sulfanilamide and coupled with N‐(1‐naphtyl)‐ethylenediamine dihydrochloride to form a purple‐red azo dye monitored at 538 nm.

Nitrate can be determined within a range of 1.35–50.0 mg L?1 of NO3 ? (corresponding to 0.270–10.0 g of NO3 ? per kg of vegetable), with a conversion rate of nitrate to nitrite of 99.1±0.8%. The results obtained for 15 vegetable extracts compare well with those provided by the classical procedure, with a sampling throughput of 24 determinations per hour and relative standard deviations better than 1.2%.  相似文献   

20.
In the present work, magnetic iron oxide nanoparticles (MIONPs) coated with sodium dodecyl sulfate (SDS) and modified with 1-(2-pyridylazo)-2-naphthol (PAN) as a new nanoparticle were prepared and used as an adsorbent for the extraction and preconcentration of copper ions. After adsorption, copper ions were desorbed with nitric acid (HNO3), followed by determination with flame atomic absorption spectrometry (FAAS). The extraction conditions0. were investigated systematically. The linear range 3.0–500.0 ng mL?1 and the detection limit of 0.6 ng mL?1 were obtained. The relative standard deviation (RSD) of the method for seven replicate determinations of 0.1 µg mL?1 of Cu(II) was 2.2%. The method was applied for the determination of Cu(II) in different water samples with good trueness. The accuracy was also evaluated through analyses of a certified reference material (CRM TMDW-500).  相似文献   

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