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1.
Nitrilotriacetic acid (NTA) and ethylenediaminetetraacetic acid (EDTA) were compared for their ability to solubilize Pb from a highly-contaminated (PbT 21%) soil collected from a battery recycling facility. For chelant concentrations below 0.04 M (representing a 1:1 chelant-to-PbT molar ratio), EDTA released 10 to 30% more Pb than NTA. NTA-to-Pb T ratios greater than 1:1 reduced Pb recovery because of readsorption of Pb(NTA)2 4? onto positively-charged oxide soil components at pH < 8.5. For the EDTA system, however, complexation completely bound all coordination sites of Pb and EDTA, leaving no functional groups available for surface adsorption. Thus, Pb recovery progressively increased with higher EDTA concentrations, although the additional Pb release with each EDTA increment became smaller. For pH < 5 and EDTA/Pb of 2:1, Pb recovery exceeded 90%. The addition of 0.5 M NaC1O4 enhanced Pb recovery by EDTA for pH 5 to 12, but substantially suppressed recovery by NTA for pH < 11. Because Pb release by NTA was diminished by high ionic strength and chelant-to-metal ratios, NTA may be limited as a soil washing reagent. Stronger complexation and consistent Pb desorption behavior by EDTA favors its use.  相似文献   

2.
We examined the effect of TiO2 nanoparticles (NPs) on the growth of maize and soybean plants and associated soil microbial communities. Plants were grown in a greenhouse, and low levels of undoped or nitrogen-doped TiO2 NPs were applied. Plant growth and nutrient content were determined, and effects of NPs on composition of soil microbial communities were examined using terminal restriction fragment length polymorphism analysis (TRFLP) of rDNA. We found no significant effects of TiO2 NPs on plant growth, nutrient content, or the composition of bacterial communities within the rhizosphere. However, arbuscular mycorrhizal fungal communities were affected by application of undoped and nitrogen-doped TiO2 NPs. This observation may be partially attributed to the small but significant TiO2 NP uptake levels in the root tissues of both plants. Our results suggest that even low concentrations of TiO2 NPs may influence some important groups of soil microbes, such as mycorrhizal fungi, but changes in the composition of microbial communities may not affect plant growth under conditions of adequate moisture and nutrients.  相似文献   

3.
Sediment cores were taken from the remote Sagamore and Woods Lakes in New York State's Adirondack acid lake region and analyzed for 3 to 7 ring polycyclic aromatic hydrocarbons (PAHs) and Ag, Al, As, Be, Cd, Cr, Cu, Hg, Ni, Ph, Se, Sn, TI, V, and Zn. With the exception of perylene, all of the parental PAHs, e.g. those without sidechains, and several of the metals, Pb, As, and Cd, were found to be significantly increased in the sediments of both lakes compared to their natural integrated deposits (ng cm?2) and their background concentrations (μg g?1 or ng g?1 dry wt). Although the concentrations were generally much higher in Woods Lake, the total anthropogenic integrated depositions were about the same in both lakes for most of the metals and the 3 to 4 ring PAHs. The prime source of most of the 3 to 7 ring PAHs and trace elements measured is ascribed to anthropogenic combustion. Anthropogenically derived materials decreased in concentration with depth to baseline levels in sediment layers estimated by137Cs analyses to be ～30 yr old, while biogenic or crustal derived species remained constant or fluctuated with core depth.  相似文献   

4.
The growth rates of two diatoms, acidophilic Asterionella ralfsii and circumneutral A. formosa, were differentially affected by varying pH, Al, and EDTA in chemically defined media. Free Al ion concentration increased as pH and EDTA concentration decreased. Free trace metal ion concentration decreased as EDTA levels increased but increased by orders of magnitude upon addition of Al. pH had an overriding species specific effect on growth rate; at low pH A. ralfsii had higher growth rates than A. formosa and vice versa at high pH. For both species higher EDTA levels depressed growth rates. Moderate additions of Al generally resulted in growth stimulation. The growth rate stimulations, especially at 200 and 400 μg L?1 Al additions, correlate to increases in free trace metal ion concentrations. The EDTA-AI interaction effects on growth rate were both pH and concentration dependent: at pH 7 both species were stimulated by addition of Al at all EDTA levels (except A. ralfsii at 5.0 mM EDTA and A. formosa at 0.5 mNM EDTA); at pH 6 Al addition either stimulated or had no effect on the growth rates of both species (except at low EDTA and high Al levels); at pH 5 A. formosa did not grow and additions of 200 μg L?1 Al stimulated growth of A. ralfsii. It is likely that the effect of pH, Al, and EDTA on speciation of essential or toxic trace metals affects growth rates of these diatoms in a species specific manner.  相似文献   

5.
This paper presents the findings of initial investigation of the role of Spartina alterniora Loisel. in the movement of chlorinated hydrocarbons. 14C-polychlorinated biphenyls and technical Aroclor® 1254 were used for the determinations. The findings demonstrate that Spartina accumulates 14C-radioactivity from sand and organic mud soil systems treated with 14C-PCB's. These findings also demonstrate that this plant has the capacity to accumulate 14C-radioactivity to levels elevated above that in the treated soil. Other experiments with Aroclor® 1254 demonstrate that cogeners of Aroclor® 1254 are present in Spartina stem and root extracts. These experiments also suggest that the chlorinated hydrocarbon uptake process is modulated by the plant and that this results in selective cogener uptake. The selectivity appears to be for the lesser chlorinated components of the commercial mixture. Overall, this study suggests that Spartina may act as an initial vector for mobilization of sediment bound chlorinated hydrocarbons to the estuarine food chain.  相似文献   

6.
Kaolinite was equilibrated with Cd and with varying amounts of the individual compounds: EDTA, NTA, alginic acid, and humic acid. In experiments in which the Cd and kaolinite concentrations were held constant, and the ligand concentration allowed to vary, conditions under which ligand enhanced and inhibited Cd association with the solid phase were noted. Further experiments at constant Cd: ligand confirmed that, for alginic acid and humic acid, enhancement of uptake occurred, while EDTA diminished uptake. These results were compared with the adsorption of ligand by clay in the absence of organic, and it is suggested that the enhancement of uptake is due to the formation of an adsorbed organic layer on the clay serving as a solid phase ligand.  相似文献   

7.
Tetrahymena pyriformis, a common freshwater ciliate concentrated the four common HCH (Hexachlorocyclohexane) isomers viz., α, β, δ, and γ to varied extent. Bioconcentration factor [as expressed by the ratio of cellular insecticide in ng mg?1 (dry weight) to supernatant in ng μL?1 ranged from 342 to 2260 for α-HCH, 37 to 831 for β-HCH, 326 to 2806 for δ-HCH and from 106 to 1214 ppm for γ-HCH.  相似文献   

8.
Greenhouse soils are regularly treated with metham-sodium, which in soil is quickly transformed to the fumigant methyl isothiocyanate. An experimental fumigation was carried out in a greenhouse with sandy soil. Data were collected on the behavior of methyl isothiocyanate in soil and its permeation through a film of low-density polyethene (LDPE) covering the soil. This cover was found to be highly permeable to methyl isothiocyanate. When the fumigation of greenhouse soil was simulated with a computation model, the use of LDPE film only appreciably reduced the rate of emission into the air in the first two days. The cumulative emission corresponded to about half of the dosage for some practical situations. It is concluded that dosages should be lower and applied more effectively, and less permeable soil covers should be used.  相似文献   

9.
Management of soils to facilitate plant beneficial microbial interactions requires basic knowledge of the species composition and microbial community structures in the plant rhizosphere. Here, we examined composition of bacterial communities associated with rhizosphere microsites located at the root tips and mature root zones of Lolium perenne when grown in Chilean ash-derived volcanic soils (Andisols: Freire and Piedras Negras soil series). Community structures were analyzed by pyrosequencing of 16S ribosomal RNA (rRNA) genes followed by in silico analysis for phylogenetic assignments (MOTHUR and Visualization tool for Taxonomic Compositions of Microbial Community (VITCOMIC)). Analysis of the community structure revealed significant differences in community structures in relation to the soil series, which differed particularly in the relative abundance of Cyanobacteria and Firmicutes. However, no significant differences were observed with respect to root microsite location in the same Andisol series. Predominant taxa included members of the Proteobacteria, Actinobacteria, and Acidobacteria. Analysis by VITCOMIC showed that dominant bacterial groups comprised only 5 to 10 % of the total bacterial community and the remaining majority of bacteria included low-abundant taxa (Fusobacteria, Thermotogae, Lentisphaerae, Tenericutes, Deferribacteres Spirochaetes, Planctomycetes, Thermotogae, and Deinococcus-Thermus), most of which have not been previously reported or associated with the plant rhizosphere according to GenBank database. The results indicate that most of bacteria in the Chilean Andisols have not been described to the rhizosphere plants and their functional traits are still largely unknown.  相似文献   

10.
A theoretical model describing the general interaction between atmospheric trace gases, such as S02, NH3, C02 and 02, chemical reactant gaseous product H2SO4 and hydrometeors containing NaCl is proposed to study a possible mechanism for HCl production in non-precipitating cloud and the determination of the pH value of cloud droplets. Four different cloud droplet distributions have been used to estimate the upper limit of the amount of gaseous HCl released into the atmosphere resulting from the evaporation of cloud droplets. It is shown that the acid production and the amount of HCl released depend on the following factors: (a) the temperature of the cloud; (b) the oxidation rates; (c) the ambient concentration of SO2, NH3, and H2SO4; (d) the life cycle of the cloud; and (e) the liquid content of the cloud. This proposed chemical model also predicts a pH value spectrum depending on the cloud droplet distribution. Field measurements for the dependence of pH value on particle size and spatial distribution of gaseous HCl are recommended.  相似文献   

11.
The occurrence and characteristics of chemically-based density stratification in portions of the Seneca and Oswego Rivers, downstream of ion-polluted Onondaga Lake, are described for seven different days in the summer and fall of 1978 and 1981, which covered a wide range of river flows. The results indicate that chemically-based density stratification occurs routinely in the Seneca River downstream of the lake inflow, in response to a continuous chemically-based density difference between the two systems of 0.0015 to 0.0030 g cm?3. The persistence of the phenomenon, and therefore the longitudinal range over which the river stratification occurred, was dependent on the velocity of river flow and the magnitude of the density gradient that bordered the upper river water and the lower released lake water. During the low flows common to summer the stratification extended approximately 14 km downstream to a dam, and 3 km upstream, of the lake outlet — river junction. Vertical mixing between the stratified layers increased as the flow in the Seneca River increased, and as the vertical density gradient decreased. A dimensionless group, $$\frac{D}{{V\left( {\frac{\rho }{{\Delta _\rho /\Delta _z }}} \right)}}$$ where: D = apparent vertical diffusion (m2 hr?1), V = average velocity of the overlying river flow (m hr?1 ), p = density at the interface between the stratified layers (g cm?3), and Ap/Az = density gradient between the stratified layers (g cm?3 m?1), was found to be constant for summer low flow conditions for a 6.5 km length of the Seneca River, thus quantifying the interaction between vertical mixing and the included influences for that portion of the river. The occurrence of chemical stratification in the river had dramatic implications on the corresponding distribution of dissolved oxygen (DO). The isolation of the organically enriched lake water in the lower layer enhanced the depletion of DO there, which resulted in the development of substantial (> 4.0 mg 1?1 ) DO stratification downstream of the discharge from the lake during summer low flow periods.  相似文献   

12.
The objectives of this study were to determine and to reduce phytotoxicity of two industrial effluents. Phytotoxicity of the treated and untreated samples was determined using millet seed germination test. The results of this and other studies showed that the test was reproducible and useful for effluent toxicity determination. Effluent sample I was from an industrial wastewater pretreatment plant and sample II was from a specialty chemical industry. Sample I was weakly acidic and sample II was alkaline. pH adjusted to 7 to 8 was found to have no effect in phytotoxin removal. Granular and powdered activated carbon effectively reduced phytotoxicity. Amberlite XAD-4 (nonionic polymeric adsorbent) and cation exchange resin had a partial effect. Anion exchange resin, silica gel, Sephadex G-75, and starch xanthate had no effect.  相似文献   

13.
A study has been conducted on the transformation of Cr(III) and Cr(VI) in simulated natural water conditions. It has been found that these forms are readily interconvertible under natural water conditions. The results of this study indicate that Cr(VI) is reduced by Fe(II), dissolved sulfides, and certain organic compounds with sulfhydryl groups, while Cr(III) is oxidized by a large excess of MnO2 and at a slow rate by Oz under conditions approximating those in natural waters. Based on the results of these studies, water quality standards for Cr should be based on total Cr rather than on Cr(VI), as has been frequently done in the past.  相似文献   

14.
The specific conductance of surface delivery waters to the Shark River Slough (Everglades National Park, Florida) has increased significantly since the completion of Levee 29 (L-29) and the S-12 water delivery system in the early 1960's. In order to document the response of specific conductance in the slough to changing environmental conditions, it was monitored continuously for a period of 12 mo at a location in central Shark approximately 17 km south of the water delivery site. In addition, variability in isoconductivity patterns throughout the slough was assessed by conducting biweekly surveys at 97 locations. Specific conductance was found to respond to a variety of natural and manmade environmental changes and proved to be an important management tool serving as an early indicator of potentially broad changes in water quality. Factors important in determining overall isoconductivity patterns in Shark Slough include:
  1. the ionic composition of surface delivered to Shark Slough via the S-12 delivery structures.
  2. the quantitative relationship between the amount of surface water delivered to the slough and the amount of precipitation falling directly upon the slough.
  3. the effects of evapotranspiration and concentration of biological organisms during seasonal periods of extreme drawdown.
  相似文献   

15.
The Salton Sea is a 93 000 ha saline lake fed by drainage water from more than 283 000 ha of irrigated lands in the Imperial and Coachella valleys of California. A total of 21 composite samples of four recreationally important fish species — bairdiella (Bairdiella icistia), orangemouth corvina (Cynoscion xanthulus), sargo (Anisotremus davidsoni), and Mozambique tilapia (Tilapia mossambica) —collected there were analyzed for 14 elements. Twelve of these elements were detected in one or more of the samples: As, B, Co, Cu, Fe, Hg, Mo, Ni, Pb, Se, V, and Zn. Cadmium and Tl were not detected. The ranges in concentrations of elements in the skinless fillets of bairdiella, corvina, and sargo, and in whole bodies of all four fishes were comparable to levels that are typically measured in saltwater fishes. Only Se concentrations were elevated (as much as 14 µg g?1 dry weight in both fillets and whole bodies) in this series of samples. Elevated concentrations of Se have already led to public health advisories concerning the consumption of fish and might eventually cause the demise of fish populations from toxic effects.  相似文献   

16.
Munronia delavayi Franch. (Meliaceae) is a vulnerable perennial species that is narrowly distributed and endemic to the dry-hot valley of the middle/lower Jinsha River. However, 12 hydropower stations are currently scheduled to be built in the middle and lower Jinsha River drainage and their distribution overlaps with the range of M. delavayi. The construction of these hydropower stations will cause flooding of the adjacent habitats that support M. delavayi and will change the local ecological environment, which may result in a new and dangerous situation for the survival of this species. Our aim was to evaluate the population structure and propose the most suitable conservation strategy for M. delavayi to support its adaptive potential. In this study, we collected 70 individuals from seven populations that covered most of the geographic range along the Jinsha River and investigated the population diversity, genetic structure and demographic history of this species by analyzing the variations in one mitochondrial marker (18sf-5sr), two non-coding chloroplast DNA regions (trnT-trnL, trnS-trnG), and one nuclear DNA marker (Gs687f-994r). As a result, three mitotypes, nine chlorotypes and six haplotypes with high genetic diversity (H T = 0.580, 0.774 and 0.740) were detected based on mtDNA, cpDNA and nDNA and a strong genetic structure (F ST = 0.855 and 0.545) was detected based on cpDNA and nDNA. Our study also indicated that habitat fragmentation and limited gene flow may result in the genetic differentiation of this species and that the population distributed in Qiaojia, Yongshan and Panzhihua should be proactively protected based on the conservation genetic analysis.  相似文献   

17.
A national and interregional programming model is analyzing the effects of banning Chlordane and Heptachlor from U.S. agriculture. The model has sectors for land and water resources, crop and livestock production, commodity transportation and domestic and foreign demand. The central Corn Belt would be put at some disadvantage and lose production to other regions. Soybeans and small grains would replace corn on low lands and the imputed values of this land would decline. Crop rotations would include somewhat less corn.  相似文献   

18.
The effect of six organic amendments on Pb solubility and availability was studied from May to September 1978 in a sandy soil low in organic matter. Three extractants were used to essay the Pb solubility: BaCl2 0.5M, AcNH4 2.5% at pH 7.0 and EDTA 0.05M at pH 7.0. During the aging process both increases and decreases of Pb solubility were observed in manured soils with respect to the control. Only in the soil treated with cow manure was a decrease of Pb solubility in ammonium acetate always noted. From regression lines of Pb concentration on soil/solution ratio it was possible to observe that only the soil treated with cow manure showed a significant decrease of slope of regression line when it was dispersed in ammonium acetate solution. The regression lines of Pb concentration on organic matter extracted by ammonium acetate and, especially, EDTA showed that these reagents extract mainly Pb complexed with organic compounds. A physiological test on Pb availability showed that only in the presence of cow manure was the Pb assimilation greatly decreased.  相似文献   

19.

Purpose

Middle-European floodplain soils are often contaminated with mercury (Hg) and periodically flooded. In this study, the influence of a flooding event and subsequent dewatering on the volatilization of elemental Hg and methylated species was investigated in a laboratory experiment.

Material and methods

Undisturbed soil cores were taken from a topsoil (12.1?±?0.75 mg kg?1 Hg) at the Elbe River in Lower Saxony, Germany. Soil columns were incubated at 20 °C with varying soil moisture (water-saturated for 2 weeks, 95 and 90 % water content for 1 week each), and the redox potential (EH) was recorded. The gaseous Hg that accumulated in the headspace of the flux chamber of the columns was pumped over cooled traps filled with adsorber material and analyzed by gas chromatography/inductively coupled plasma mass spectrometry for the various Hg species.

Results and discussion

The watering of the soil resulted in a rapid decrease in the EH and the achievement of strongly reducing conditions (EH??1 Hg at the beginning to 5.78 μg L?1 Hg at the end of the experiment. Species analyses revealed that exclusively elemental Hg volatilized. The volatilization rate was between 1.73 and 824 ng m?2 h?1 Hg, which is consistent with other studies at the Elbe River.

Conclusions

Even when flooded for a longer period of time, floodplain soils should show neither emission of methylated Hg nor exceptionally high volatilization of elemental Hg.  相似文献   

20.

Purpose

The aim of this study was to evaluate in the medium term (5 years) the effect of two organic amendments, which were spiked to a degraded soil as a strategy for bioremediation, on the amount and characteristics of soil humic acids (HAs) and their ability to associate with certain extracellular enzymes.

Materials and methods

Soil samples were collected in an experimental field where 5 years earlier, a mixture of the organic fraction of household waste and sewage sludge (2:1 ratio), both composted (composted residue, CR) and non-composted (fresh residue, FR), had been added in triplicate at rates equivalent to 1 % (D1) and 3 % of organic carbon (D2) to 30-m2 plots as a strategy for degraded soil restoration. Humic substances (HSs) and HAs were extracted from the collected soil samples and submitted to chemical, biochemical, spectroscopic (FTIR), and chemical-structural (CPMAS 13C NMR) analyses.

Results and discussion

After 5 years, the amended soils showed significantly higher HS and HA content than did the control soil, and the differences with respect to the control were greater with compost addition than with FR addition. The HA from the amended soils had higher H, N, and S contents than the HA from the non-amended soil in addition to a lower oxygen content and lower O/C ratio values. Furthermore, the FTIR spectra of the HA from the amended soils showed a higher absorption intensity in bands corresponding to aliphatic and amide-carboxylic groups and polysaccharide structures and a lower absorption intensity in bands corresponding to carbonyls and carboxylic groups than the HA from the control. These results were confirmed by 13C-NMR spectra, which showed a clear increase of aliphatic compounds in the HA from the amended soils with respect to the HA from the control. HA spectra were not greatly influenced by the maturity of the amendment or by the application dose.

Conclusions

In general, the addition of organic amendments increased the quantity of enzymes immobilized in the humic colloid. Furthermore, the addition of the composted residues favored to a greater extent the immobilization of the abovementioned enzymes, which represent a biological reservoir in the soil. This is of great importance since these enzymes possess functional capacity even when the soils are under conditions that are stressful or unfavorable for microbial life. An increase in the quantity of immobilized enzymes such as that observed in amended soils supposes an important improvement in soil quality.
  相似文献   

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