首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 31 毫秒
1.
Abstract

Arsenic (As) is a deadly poison at high concentrations. It is mysterious in the sense that people are exposed to it most of the time through drinking groundwater, fortunately at much lower concentrations than the deadly levels, and usually without knowing it. Arsenic content in alluvial aquifers of Punjab varied from 3.5 to 688 µg L?1. Arsenic status of groundwater is classified into low (<10 µg L?1), moderate (≥10 to <25 µg L?1), high (≥25 to <50 µg L?1), and very high (>50 µg L?1). In zone I, the concentration of As in groundwater varied from 3.5 to 42 µg L?1 with a mean value of 23.4 µg L?1. On the basis of these limits, only 8% of samples were low, whereas 51 and 41% of the total samples collected from this region fall in the moderate and high As categories. The concentration of As in groundwater of zone II varied from 9.8 to 42.5 µg L?1 with a mean value of 24.1 µg L?1. Arsenic concentration in the alluvial aquifers of the central plain of zone II is 2 and 52% in the low and moderate limits. In this region, 46% of groundwater sites contain high As concentrations. Arsenic concentrations in the aridic southwestern parts are significantly different from other two provinces. The As concentration ranged from 11.4 to 688 µg L?1 with average value of 76.8 µg L?1. Eleven percent of the aquifers of the southwestern region of zone III are in the moderate category, 54% in the high, and 35% in the very high. According to safe As limits (<10 µg L?1), only 3 and 1% of the groundwater samples collected from zones I and II were fit for dinking purposes with respect to As content. In the aridic southwest, zone III, all water samples contained As concentrations greater than the safe limits and thus are not suitable for drinking purposes. The presence of elevated As concentrations in groundwater are generally due to the results of natural occurrences of As in the aquifer materials. The concentration of other competitive oxyanions in waters such as phosphate, sulfate, and borate also depressed the adsorption of As on the sorption sites of aquifer materials and thereby eventually elevate the As concentration in groundwaters. In groundwater of alluvial aquifers of Punjab, released from sulfide oxidation and oxyhydroxide of iron, elevated (>10 µg L?1) concentrations of As were widespread because of high pH (>8.0) and higher concentrations of phosphate, borate, sulfate, and hydroxyl anions. It is conclusively evident that geochemical conditions, such as pH, oxidation–reduction, associated or competing ions, and evaporative environments have significant effects on As concentration in groundwater. These conditions influence how much As is dissolved or precipitated into the water and how much is bound to the aquifer materials or the solid particles in water.  相似文献   

2.
The rate at which dried soils are rewetted can affect the quantities and forms of nutrients in leachates. Both dried and moist replicated (n?=?3) samples of two contrasting grassland soil types (clayey vs brown earth) were irrigated during laboratory experiments with identical total amounts of water, but at different rates, ranging from 0 h, increasing by 30-min increments up to 4 h, and additionally a 24-h rewetting rate. Total P concentrations in leachates from dried samples of both soils generally decreased as rewetting rate increased, ranging from 2,923?±?589 μg P L?1 (0.5 h rewetting rate) to 731?±?46.0 μg P L?1 (24 h, clayey soil) and 1,588?±?45.1 μg P L?1 (0.5 h) to 439?±?25.5 μg P L?1 (24 h brown earth). Similar patterns in concentrations occurred for molybdate reactive P (MRP), although concentrations were generally an order of magnitude lower, indicating that the majority of the leached P was probably organic. The moist brown earth leached relatively high concentrations of MRP (maximum 232?±?10.6 μg P L?1, 0.5 h), unlike the moist clayey soil (maximum 20.4?±?10.0 μg P L?1, 0 h). The total oxidised N concentrations in leachates were less affected by rewetting rate, although longer rewetting rates resulted in decreased concentrations in leachates from the dried samples of both soils. The difference in responses to rewetting rates of the two soils is probably due to differences in the fate of the microbial biomass and adsorption properties in the soils. Results show that soil moisture could be an important factor in regulating nutrient losses and availability, especially under changing patterns of rainfall predicted by future climate change scenarios.  相似文献   

3.

Purpose

Transformation and transport of soil phosphorus (P) from chemical fertilizer or manure are affected by agronomic practices (i.e., fertilization, irrigation, and tillage) and numerous abiotic factors (i.e., temperature, drought, and rainfall). Previous studies on the effects of manure application on P loss were mostly conducted during cultivation and often using the laboratory column approach. Validated field observations by integrating P availability with the risk of P loss are few. This study aimed to evaluate the effects of rainfall and manure application on P leaching during fallow season.

Materials and methods

An in situ field lysimeter experiment was performed. Leachate was collected and analyzed for total P (TP) and dissolved reactive P (DRP). At the end of the lysimeter trial, soils were sampled incrementally to a depth of 40 cm with the following depth intervals: 0–4, 4–10, 10–20, 20–30, and 30–40 cm. Soil water extractable P (Pw) was analyzed and degree of P saturation (DPS) was calculated after oxalate and Mehlich-3 (M3) extractions.

Results and discussion

Phosphorus loading was found below 40 cm in all treatments and P was most concentrated in the 4–10 cm soil layer. High rainfall enhanced P leaching and consequently led to lower Pw and higher leachate DRP and TP than low rainfall. Furthermore, P leaching was observed regardless of manure application, with the highest leachate DRP (1.83 mg L?1) and TP (7.46 mg L?1) concentrations found at the end of experiment (day 53). Observed P leaching loads during fallow season (53 days) varied between 0.08 and 1.21 kg ha?1. The thresholds of DPS indicating P leaching were identified at 18.9% DPSM3(Ca) and 12.9% DPSM3(Ca+Mg), respectively. In this study, the DPSM3(Ca) and DPSM3(Ca+Mg) values exceeded the corresponding thresholds in the upper 30-cm soil layer but did not reach the thresholds at 30–40 cm. Nevertheless, the leachate DRP and TP indicated soil P leaching.

Conclusions

The results showed that intensive rainfall could significantly increase P leaching from manure application. Moreover, P leaching could occur in fallow season even in the absence of manure input, which should be assessed by not only soil P sorption capacities, but also soil fertilization history and hydrologic conditions. Implementation of soil P level evaluation is critical before spreading manure on land to avoid P pollution. Cost-effective and applicable soil test methods are required to generate environmental indicators to classify agricultural lands for risk of P loss, providing basis to safe manure disposal.  相似文献   

4.
ABSTRACT

Contamination of ground water as a consequence of soil leaching processes is an issue of major concern. In this context, a simulation of the soil leaching process was designed. A sequential injection (SI) method to monitor the soil leaching of iron complexes with in-line rain simulation for leachate production is described. The developed methodology comprises the SI determination of both iron(III) and 3-hydroxy-4-pyridinones iron(III) complexes, coupled to a mini soil column (mSC) for displaying in-line rain simulations. The described SI method enabled iron(III) determination within the range 2.0–35 µmol L?1, with a detection limit of 0.42 µmol L?1, and determination of iron(III) complexes in the range 1.0–45 µmol L?1. It was successfully applied to leachates from laboratory scale soil columns (LSSC), with good precision for both iron(III) and iron complexes determinations: calculated relative standard deviation (RSD) of 5% and 6%, respectively. A step further in automation and miniaturization was attained with the incorporation of a mini soil column for the in-line leachate production. The system enabled the soil leachate production and assessment in less than 5 min, including determinations in triplicate.  相似文献   

5.
Engineered plant growth media must support plant growth while minimizing environmental impact. The objective of this research was to determine how different growth media influence nutrient leaching. Plant growth media contained varied amounts of soil, sand, compost that did or did not contain manure, and possible sorbents for phosphorus. If the plant growth media included compost derived partly from manure, leaching losses of nutrients were excessive due to the high nutrient load in the compost. Layering compost over the plant media mix resulted in lower nitrate concentrations in effluent (87 mg L?1) compared with mixing compost into the media (343 mg L?1); however, growth of prairie grasses was reduced because of dense media below the compost blanket (0.09 versus 0.31 g). Using lower amounts of compost that did not contain manure resulted in lower mean nitrate concentrations in effluent (101 versus 468 mg L?1). Media that had no soil (13.3 mg L?1) had greater loss of phosphorus after harvest for unsaturated drainage than media with soil (1.8 mg L?1). To reduce nitrate leaching, only small amounts of low-nutrient compost (higher C:N ratio) should be incorporated into the media. If compost is applied as a surface blanket without incorporation, then soil should be added to the sand to reduce density of the media and increase plant growth.  相似文献   

6.
Abstract

The effect of zinc–phosphorus (Zn‐P) interaction on Zn efficiency of six wheat cultivars was studied. The higher dry matter yields were observed when Zn was applied at 5 µg g?1 soil than with no Zn application. Phosphorus applications also increased dry matter yield up to the application of 25 µg P g?1 soil. The dry matter yield was significantly lower at the P rate of 250 µg g?1 soil. At the Zn‐deficient level, the Zn‐efficient cultivars had higher Zn concentrations in the shoots. Zinc concentrations in all cultivars increased when the P level in the soil was increased from 0 to 25 µg P g?1 soil except for the cv. Durati, in which Zn concentrations decreased with increases in P levels. However, when Zn×P interactions were investigated, it was observed that at a Zn‐deficient level, Zn concentrations in the plant shoot decreased with each higher level of P, and more severe Zn deficiency was observed at P level of 250 µg g?1 soil.  相似文献   

7.
A flow injection analysis (FIA) method capable of automation for molybdate reactive phosphorus (P) determination in soil extracts is described. Results obtained using this method in three soil extracts [calcium chloride (CaCl2), Olsen, and Mehlich I] were the same as those provided by the manual molybdate blue colorimetric method. Linear range extending to 2 mg P L?1, detection limits ranging from 6 to 26 µg L?1 depending on the soil extract, and accurate recoveries from P‐spiked samples were achieved. The sensitivity of the system was around 0.3 absorbance units per mg P L?1, and the sampling frequency was 72 samples h?1, higher than those described for most of the flow injection methods.  相似文献   

8.

Purpose

A simple and highly efficient economic method for the analysis of 11 antibacterial drugs including two tetracyclines, three quinolones, four sulfonamides, chloramphenicol and tylosin, in livestock manure, was developed using solid-phase extraction (SPE) and high-performance liquid chromatography (HPLC).

Materials and methods

The analytes were successively extracted by EDTA-McIlvaine solution and organic solvent mixture. The extracts were degreased with n-hexane and cleaned through SPE on a hydrophile-lipophile balance (HLB) cartridge. All compounds were determined on a C18 reverse phase column with gradient elution.

Results and discussion

Recoveries calculated from spiked samples of animal manures ranged from 62.65 to 99.16 % for 11 antibiotics with relative standard deviations of less than 10.0 %. Limits of detection ranged from 0.1 to 1.9 μg kg?1, and limits of quantification ranged from 0.3 to 5.9 μg kg?1.

Conclusions

The results show that SPE-HPLC is an inexpensive and practical method for rapid detection of multiple antibiotics in animal manure.
  相似文献   

9.
Water loss as deep percolation is considerable in furrow irrigation in light soils due to the high infiltration rate. Application of soil conditioners such as bentonite reduces the infiltration rate and improves irrigation application efficiency (Ea) in these soils. The effects of bentonite application rates (BAR) of 0, 2, 4 and 6 g L?1 on infiltration of a loamy sand soil were determined in a soil column in the laboratory. The exponent of the Kostiakov infiltration equation was not influenced by BAR. Maximum reduction in infiltration equation coefficient and final infiltration rate (i f) occurred with 2 g bentonite L?1 and this reduction was lower on increasing BAR from 2 to 4 and 4 to 6 g L?1 compared with control. The effect of 2 g L?1 BAR on infiltration and its effect on the design of furrow irrigation in a field with a loamy sand soil indicated that in the first irrigation after field ploughing and seed planting, longer furrow length, lower deep percolation and higher Ea are obtained.  相似文献   

10.
Veterinary antibiotics like sulfonamides are frequently detected in arable lands and they can potentially contaminate food crops. It is thus of great importance to identify strategies to reduce food crops’ uptake of antibiotics. For the first time, using a pot culture experiment, sulfathiazole (STZ) uptake by lettuce (Lactuca sativa L.) grown in antibiotic-contaminated soils (10 and 100 mg STZ kg?1 soil) and treated with (in)organic amendments, namely chemical fertilizer (NPK), compost, and hairy vetch, was investigated. Subsequent enhanced plant growth was witnessed when using hairy vetch treatment. The amount of antibiotic uptake was significantly reduced to 5 and 33% with hairy vetch application compared to compost or NPK application at 10 and 100 mg kg?1 STZ, respectively. The total amounts of accumulated STZ in plant parts increased as the levels of STZ contaminated in soils were increased. STZ was much more abundant in the roots than the leaves. Within 30 days, the extractable STZ in the treated soils—especially with hairy vetch—diminished considerably to concentrations that are frequently detected in arable soils. We conclude that utilization of green manure (cover crop—hairy vetch) is a viable strategy for safer crop production in antibiotic-contaminated soils.  相似文献   

11.

Purpose

A total of 58 dewatered sludge samples were collected from 58 sewage treatment plants (STPs) geographically located in 31 provincial cities of China; the concentrations of heavy metals and antibiotics were determined to monitor the pollutant levels on a large scale, and the pollutant concentrations in sludge samples from different sources of sewage sludge and different geographical regions were compared.

Materials and methods

All the samples were divided into two portions, one of which was air-dried for determination of heavy metals. The other portion was placed in a brown glass bottle and frozen at ?20 °C for antibiotics analysis. Total heavy metals were digested with aqua regia and determined by atomic absorption spectrophotometry (Varian SpectrAA 220FS and Varian SpectrAA 220Z). The antibiotics were extracted with EDTA-sodium phosphate buffer with acetonitrile/Mg(NO3)2-NH3?H2O, v/v, 3:1 and analysed by liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS) and quantified by the isotope-labelled internal standard method.

Results and discussion

In all the sludge samples, zinc was the most abundant metal followed by copper, with relatively low concentrations of chromium, lead, nickel and cadmium. Only 20 % of samples exceeded the Chinese class A values of heavy metal standards for agricultural use (GJ/T309-2009). Sixteen different antibiotics were detected in all the sludge samples, and fluoroquinolones (FQs) and tetracyclines (TCs) were more abundant than sulfonamides (SAs). Concentrations of ∑FQs, ∑TCs and ∑SAs ranged from 1,569 to 23,825 μg kg?1 (mean 8,274 μg kg?1, dry weight), from 592 to 37,895 μg kg?1 (mean 8,326 μg kg?1, dry weight) and from 20.1 to 117 μg kg?1 (mean 55.4 μg kg?1, dry weight), respectively. Tetracyclines (except chlortetracycline) were significantly correlated with zinc and lead. No significant regional trends were observed in the concentrations of heavy metals and antibiotics in sludges.

Conclusions

Heavy metal concentrations are not the major factor restricting domestic and mixed flow sludge application, but the antibiotic concentrations in sludges are problematic; regulation of antibiotic use and establishment of standards to ensure safe handling of sludges are needed.  相似文献   

12.
Inceptisols and Vertisols are two dominant soil orders that support major agricultural production in India. These soils often exist in semi-arid and arid regions. Low precipitation and high evaporation demand leads to salt accumulation in these areas. The problem of salt accumulation is further compounded by the presence of saline/alkaline groundwaters. We evaluated the effect of modified Ca/Mg waters on ionic composition, dispersion, and clay flocculation of sodic Inceptisols, saline-sodic Inceptisols, and normal Vertisols from different parts of India. A completely randomized factorial design with three replications of individual soils were sequentially leached with five pore volumes of deionized, saline water of 60 and 120 me L?1 total electrolyte concentration (TEC) at a fixed SAR of 5.0 mmol1/2 L?1/2 and Ca:Mg ratio of 2:1, 1:1 and 1:2. Application of saline waters decreased pH and increased EC of the soil leachates after leaching five pore volumes of three Ca/Mg ratios of 60 and 120 me L?1 solutions in sodic Inceptisols and normal Vertisols. In saline-sodic Inceptisols, application of saline waters decreased both pH and electrical conductivity (EC) of the soil leachates. Preferential Ca2+ holding in soil was only noticed in sodic Inceptisols when leaching process was performed with independent saline waters, but Mg2+ has a tendency to hold in soil upon application of independent saline waters for all soils except sodic Inceptisols. Periodic application of deionized water could increase soil dispersion and decreased flocculation of clay particles. Mg2+ ion had less flocculating vis-à-vis high-dispersion effect on soil clays than the Ca2+ ion.  相似文献   

13.
Three hydroponic experiments were set up to study the rhizofiltration of cadmium (Cd) or nickel (Ni) from artificially contaminated nutrient solution with sunflower, squash, or Indian mustard. After 48 h of exposure with 2 mg L?1 Cd‐contaminated water, 460, 415, or 1092 µg Cd g?1 (dry weight) was detected in roots of 33‐day‐old sunflower and squash or in 50‐day‐old Indian mustard, respectively. As calculated, 1 g of root dry matter of the tested crop species removed 5.7–12.4% of total Cd content present in the nutrient solution. It was supposed that pseudomonads (soil rhizoplane bacteria) and the plant growth hormone ethylene can enhance the specific surface of roots and hence roots' metal adsorption capacity. As a trend, pretreatment of Indian mustard with Pseudomonas fluorescens bacteria enhanced slightly the Cd (from 1793 to 2346 µg g?1) or Ni (from 1088 to 1192 µg g?1) concentration of roots. Cadmium concentration in roots was also enhanced from 2694 to 3273 µg g?1 when the roots of Indian mustard were pretreated with Cd‐tolerant rather than Cd‐sensitive Pseudomonas cepacia. In spite of the occurrence of new root hairs, the pretreatment of roots with ethylene proved to be ineffective in enhancement of the Cd rhizofiltration capacity of Indian mustard.  相似文献   

14.
A method for simultaneous analysis of bisphenol A (BPA) and 17α-ethinylestradiol (EE2) in water supply was developed using solid-phase extraction and high-performance liquid chromatography with fluorescence detection. The linearity was evaluated between 2.5 and 200 μg L?1 (r> for the analytes. The limits of quantification were 1.5 and 2.1 ng L?1 for BPA and EE2, respectively. The extraction was made with C18 cartridges, and recoveries obtained varied between 70 and 102 % for the strengthening of 5 μg L?1. After the validation, the method was applied in the determination of pollutants in surface water and water supply of Sao Luis, Brazil, where BPA was found in two of the eight samples analyzed, with concentrations of 1.11 and 3.61 μg L?1.  相似文献   

15.
Abstract

Phytoremediation is a good technique for removing cadmium (Cd) from farmland soils. To remove Cd from these soils effectively, it is necessary for Cd ions to be transported to the shoot organs for later harvest. However, the mechanism of Cd translocation to shoot organs via xylem vessels has not yet been elucidated. We selected oilseed rape plants (Brassica napus L.) and established a method to collect xylem exudates from these plants. After 3 days of Cd treatment (10 µmol L?1 and 30 µmol L?1) the Cd concentrations in the xylem exudates were approximately 6.5 µmol L?1 and 16 µmol L?1, respectively. The detection of Cd in the xylem exudate indicated that Cd was moving to shoot organs via xylem vessels. The effect of these Cd treatments on the amino acid, organic acid and protein composition of xylem exudates from oilseed rape plants was investigated. The level of amino acids and organic acids detected was enough to bind Cd transported via the xylem. Sodium dodecylsulfate-polyacrylamide gel electrophoresis analysis revealed that proteins with molecular weights of 36 kDa and 45 kDa clearly increased in the exudates with Cd treatment. The possibility that these compounds are binding Cd in the xylem exudates was discussed.  相似文献   

16.
Abstract

To gain a better understanding of the distribution of charred plant fragment C (CPFC) and its contribution to organic C (OC) in the particle size fractions of Japanese volcanic ash soils, each of four soil samples was divided into six particle size fractions, namely three sand-sized aggregate (20–53, 53–212 and 212–2,000 µm) fractions, one silt-sized aggregate (2–20 µm) fraction, and two clay-sized aggregate (< 0.2 and 0.2–2 µm) fractions. Furthermore, after HCl–HF treatment of these aggregate fractions, sub-fractions of less than specific gravity (s.g.) 1.6 g cm?3 (< 1.6 fraction) were isolated using s.g. 1.6 g cm?3 sodium polytungstate solution. Microscopic observation indicated that the charred plant fragments, which are black or blackish brown, were the main components in the < 1.6 fractions. Therefore, the OC in this fraction was designated as CPFC. In all the soils studied, the quantitative distribution of the CPFC of the silt-sized aggregate fractions to total CPFC of whole soils, ranging from 59 to 84%, was greatest among the aggregate fractions. The sum of the distribution (%) values of the CPFC in the three sand-sized aggregate fractions varied from 6.9 to 33%, while that in the two clay-sized aggregate fractions ranged from 1.1 to 9.4%. Similar to the CPFC, in all soils, the quantitative distribution of the OC in the aggregate fractions was greater in the silt-sized aggregate fractions (52–76%) than in the other aggregate fractions (0.1–20%). In all soils, the quantitative contribution of total CPFC to total OC of whole soils ranged from 10 to 28%. The CPFC/OC values in the aggregate fractions were 21% or more in 10 samples from a total of 24 fractions, with a maximum value of 34%. On the basis of the findings obtained in the present study, it is assumed that in Japanese volcanic ash soils the silt-sized fraction is an important reservoir of CPFC and OC, and CPFC merits attention as one of the constituents of OC in particle size fractions.  相似文献   

17.
The selective inhibition technique by specific antibiotics (streptomycin, cycloheximide) applied to substrate-induced respiration (SIR) measurement was used to test the relative contribution of fungi to bacteria (F/B ratio) to the overall microflora-induced activity in soils of European Russia. Investigated soils covered a wide climatic transect and different ecosystem types including managed vs. natural ecosystems. Before direct comparison among sites, the antibiotic inhibition technique was optimized for soil characteristics. Once the optimal concentration was set, the combined effect of the two antibiotics resulted in average 60% inhibition of SIR. The analyzed sites (in total 47) including various biomes (tundra, middle taiga, southern taiga, subtaiga, dark coniferous forests outside the boreal region, steppe, mountain forests and arable sites), were characterized by a wide range of soil pHw (3.95–7.95), soil organic carbon (0.69–24.08%), soil microbial biomass carbon (149–5028 µg C g?1 soil) and soil basal respiration (0.24–8.28 µg CO2-C g?1 soil h?1). In all the analyzed sites, a predominance of fungal over bacteria activity was observed with F/B ratios always higher than one (4.9 on average). Natural sites were characterized by higher F/B ratios (on average 5.6) compared to agricultural ones (on average 3.5).  相似文献   

18.
Abstract

A study was undertaken to determine the effects of different concentrations of arsenic (As) in irrigation water on Boro (dry‐season) rice (Oryza sativa) and their residual effects on the following Aman (wet‐season) rice. There were six treatments, with 0, 0.1, 0.25, 0.5, 1, and 2 mg As L?1 applied as disodium hydrogen arsenate. All the growth and yield parameters of Boro rice responded positively at lower concentrations of up to 0.25 mg As L?1 in irrigation water but decreased sharply at concentrations more than 0.5 mg As L?1. Arsenic concentrations in grain and straw of Boro rice increased significantly with increasing concentration of As in irrigation water. The grain As concentration was in the range of 0.25 to 0.97 µg g?1 and its concentration in rice straw varied from 2.4 to 9.6 µg g?1 over the treatments. Residual As from previous Boro rice showed a very similar pattern in the following Aman rice, although As concentration in Aman rice grain and straw over the treatments was almost half of the As levels in Boro rice grain. Arsenic concentrations in both grain and straw of Boro and Aman rice were found to correlate with iron and be antagonistic with phosphorus.  相似文献   

19.
Abstract

Soils under the main mangrove (Rhizophora racemosa and Avicennia germinans) forest in the Niger Delta, Nigeria, were characterized, and their capacities to retain heavy metals were examined by using soil column leaching experiments, using 20 mg L?1 Cu, 50 mg L?1 Zn, 20 mg L?1 Cd, and 100 mg L?1 Mn solutions. At the end of the leaching experiments, soil samples from each column were divided into two layers (0–5 cm and 5–10 cm) and analyzed for total metal retained. The fractionation of heavy metals in the surface soil samples (0–5 cm) was investigated by the sequential extraction technique. The study showed that the soils were influenced by tidal flow and characterized by the presence of very fine textured, thin (0–5 cm) to moderately thick (10–15 cm) layer of alluvium (mud) on the surface. The fibric soil material beneath the surface mud varies in thickness from about 70 to 100 cm, and beyond the histic layer is the plastic, very sticky, massive clay. In situ, the soils were neutral in reaction (pH 7.0–7.2), but became strongly acid (pH 3.3–4.8) upon drying. They are saline, high in soluble salts, highly reduced, with CEC that is low in the fibric layer, but high in the mineral, clayey subsoil horizon. The soils are saturated with water for much more than 30 days in a year and have fiber content that is more than 40 cm thick, with the fibric sphagnum constituting more than three‐fourths by volume to a depth greater than 90 cm. The soils, classified as Typic Sphagnofibrists, sequestered considerable amounts of copper (Cu), zinc (Zn), cadmium (Cd), and manganese (Mn) with most of the metals retained in the surface soils. The anthropogenic heavy metals were mostly adsorbed probably to the negatively charged sites of organics and clay. These loosely bound metals may be desorbed and reenter the aqueous phase, thus becoming a secondary source of metal pollution.  相似文献   

20.
Abstract

Two experiments were conducted to evaluate the inhibitory effects of 2-chloro-6 (trichloromethyl) pyridine (nitrapyrin) and dicyandiamide on nitrous oxide (N2O), a greenhouse gas, emission from soils amended with ammonium sulfate. In the two experiments, samples of an Andosol and a Gray Lowland soil were kept in glass vessels sealed with a butyl rubber cap and incubated at 25°C. In the first experiment, nitrapyrin (1 µg g?1 dry soil) and dicyandiamide (10 µg g?1 dry soil) were applied to samples of a water-saturated Andosol and a Gray Lowland soil to which ammonium sulfate had been applied at a rate of 0.1 mg N g?1 dry soil. Nitrapyrin decreased N2O emissions from the Andosol and the Gray Lowland soil by 71% and 24%, respectively. Dicyandiamide decreased N2O emissions from the Andosol and Gray Lowland soil by 31% and 18%, respectively. In the second experiment, nitrapyrin (1 µg g?1 dry soil) was applied to samples of an Andosol at 51% water-filled pore space to which ammonium sulfate had been applied at rates of 0.01, 0.1 and 0.5 mg N g?1 dry soil. Nitrapyrin decreased N2O emissions by 62%, 83% and 74%, respectively. Changes in the NH+ 4 and NO? 2 + NO? 3 concentrations in soil showed that nitrapyrin and dicyandiamide slowed down the nitrification process, but did not completely stop the process at any time. The results reveal the potential of nitrification inhibitors to decrease N2O emission from fertilized soil in a wide range of moisture conditions and nitrogen levels.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号