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1.
Abstract. The impact of lead shot on soils and crops was examined at a clay pigeon shooting site in northern England. Topsoil cores were collected along a 300 m transect from the shooting range, and the numbers of lead shot pellets per soil core, total and 'plant-available'(0.5 m acetic acid extractable) lead concentrations, organic matter content, pH and cation exchange capacity were determined. The number of oilseed rape plants and their stem diameters were recorded in 1 m2 quadrats placed at the soil sampling locations. Total and 'plant-available' lead concentrations in the soil were most but plant numbers per m2 and mean stem diameters were least in the area of greatest lead shot deposition. Total lead concentrations in the soil commonly exceeded 5000 mg/kg; these are considerably greater than threshold 'trigger' concentrations proposed by the Department of the Environment, above which soils are considered to be contaminated and warrant further investigation. Concentrations of lead in the oilseed rape plants themselves were also largest in the area of most intense lead shot deposition; in root samples the lead concentration exceeded 400 mg/kg. The management and remediation of contaminated soils at the clay pigeon shooting site are discussed.  相似文献   

2.
Background values for heavy metals are necessary for the assessment of metal pollution of soils and plants. Samples of cultivated and uncultivated soils, oat grain, and seed heads of orchard grass (Dáctylis glomeráta) were collected from central, southeastern, and southwestern Norway. Total and easily extractable concentrations of As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn were determined in soil samples and total concentrations in plant samples. Element distributions have been correlated with petrology of soil parent material, type of mineral deposit, soil depth, geographic area, and land use. Concentrations of heavy metals are generally within the lower part of the normal global range. The petrology of the soil parent material has the greatest influence on aqua regia extracted metal concentrations among the factors studied. DTPA extracted metals show less dependence on rock types. Presence of alum shale results in particularly high values for Cd in both soil extracts and in oat grain. Soil cultivation seems to influence the relative concentration of metals in the topsoil. The ratios of easily extractable to total concentrations of metals are primarily related to the organic matter content. Metal concentrations in oat grain can best be predicted by concentrations in DTPA extracts and soil pH among the factors studied. Seed heads of orchard grass are less affected by concentrations in the soil and appear therefore to be a poor indicator of heavy metals in soils.  相似文献   

3.
Abstract

High concentrations of lead in contaminated soils comprise a potential public health hazard. Limits between safe and dangerous levels are often based on total soil lead content. Current chemical procedures to determine total lead are unsuitable for routine soil analysis because they are time‐consuming and require highly trained personnel. This paper describes the effectiveness of three rapid extraction procedures to estimate total lead in a large number of lead arsenate‐contaminated orchard soils. Dissolution of soil lead in Kjeldahl flasks using a nitric acid‐perchloric acid mixture was virtually complete (98%) when compared to values for total lead measured by treatment with a mixture of HF, HNO3 and KClO4. Shaking of 5‐g samples in 50 ml of lN HCl or lN HNO3 for 1½ hours extracted 95 and 93 percent of the total lead, respectively. Regression equations were derived to allow estimation of total lead from values obtained in the HNO3‐HClO4, HCl, or HNO3 extracts. The HNO3‐HClO4 digestion procedure is preferred with atomic absorption spectrophotometry, while HCl extraction is suitable for routine soil analysis with inductively coupled argon plasma spectrophotometers or similar instrumentation.

Grinding of the soils to promote sample uniformity appeared unnecessary, at least in the silt loam soils tested.  相似文献   

4.
Abstract

Total soil lead was predicted satisfactorily from the Lead extracted by the Standard Morgan soil testing solution (sodium acetate with acetic acid, pH 4.8). Using 161 soils, 85% of the variance in total lead content was accounted for by:

Total Lead = ‐115 + 106.4 √Sodium Acetate Extracted Lead A modified Morgan solution, utilizing EDTA as a chelating agent, extracted greater than 3 times as much lead as the regular Morgan's solution, but was no better in predicting total lead.  相似文献   

5.
The influence of pH was examined, over the range from 6 to 14, on the amounts of p-hydroxybenzoic, vanillic, p-coumaric, ferulic and syringic acids, p-hydroxybenzaldehyde and vanillin, extracted from four soils and associated roots or leaf litter. Adjustment of pH was obtained by the addition of graded amounts of Ca(OH)2 to water or by 2 m NaOH. The roots associated with three of the soils were from permanent pasture, perennial ryegrass and red clover, while the leaf litter associated with the fourth soil was from beech.The amounts of each phenolic compound extracted increased continuously with increasing pH, from a “threshold” value which varied between pH 7.5 and 10.5. The amounts extracted by water alone from the soil under permanent pasture, at pH 5.8, were equivalent to concentrations in the soil solution ranging from 1.4 μm for p-hydroxybenzoic acid to < 10 nm for ferulie acid. Amounts of up to 2000 times greater than these were extracted by 2 m NaOH. Similar effects of extractant pH were found with the other soils.Comparisons of the amounts of the phenolic compounds extracted from the soils, with the amounts extracted from the associated roots or leaf litter, suggested that substantial proportions of the soil phenolic compounds were either derived from organic residues more than 4 yr old or were the result of microbial synthesis.  相似文献   

6.
The effects of acid digestion procedures and instrumentation on extracted lead (Pb) concentrations from several soils, including a mildly Pb-contaminated soil, were determined using a two-factor factorial experiment. The two factors were (i) digestion procedure [seven levels: U.S. EPA, AOAC (dry ashing), nitric acid (NA), three aqua regia procedures (AR1, AR2, and AR3), and hydrofluoric acid (HF)] and (ii) instrumentation [two levels: atomic absorption spectrometry (AAS) and inductively coupled plasma (ICP) spectroscopy]. The greatest Pb recovery was obtained when soils were digested with HF and analyzed by AAS. The results suggest that the AOAC procedure (a standard procedure for recovery of soil nutrients and trace elements in Canadian laboratories) and EPA procedure (a standard procedure in American laboratories) may underestimate Pb concentrations in some Atlantic Canadian soil types. The AAS procedure is more accurate than ICP for determining Pb concentrations in soil with a history of PbHAsO4, at least for Atlantic Canadian soils.  相似文献   

7.
Humic acids are ubiquitous and abundant in terrestrial environments; therefore, they are often co-extracted with nucleic acids and interfere with quantitative PCR (qPCR) assays. In this study a recently developed NanoGene assay that is resistant to interference by humic acids was evaluated for gene detection in soil samples. The NanoGene assay utilizes a combination of magnetic beads, dual quantum dots labels, and DNA hybridization in solution. Seven soil samples containing different amounts of organic matter were tested to compare NanoGene and qPCR assays for their respective ability to detect a bacterial pathogen. We spiked the soils with Escherichia coli O157:H7, extracted genomic DNA, and conducted NanoGene and qPCR assays targeting the E. coli O157:H7-specific eaeA gene. To prevent the inhibition of PCR that is common when using DNA extracted from soils, we used a range of template DNA concentrations and BSA addition in the qPCR assay. Compared to the qPCR assay the NanoGene assay was significantly more resistant to the inhibitory effect of humic acids, successfully quantifying the eaeA gene within a linear (R2 = 0.99) range of 105 through 108 CFU/g soil for all seven soil samples tested. In contrast, the qPCR assay was significantly inhibited using the same template DNA isolated from soils containing a range of organic content (2.0%–12%). Interestingly, the qPCR assay was still inhibited despite additional purification steps, suggesting that humic acids were still associated with DNA at a level that was inhibitory to qPCR. This study demonstrated that the NanoGene assay is suitable for quantitative gene detection in diverse soil types and is not susceptible to inhibition by humic acids and other organic compounds that commonly lead to false negative results in qPCR assays.  相似文献   

8.
Abstract

The objective of this work was to appraise the double acid (0.05N HCl+0.025N H2SO4) extraction agent for assessing the availability of Ca, Mg, and K in organic soils. The evaluation was done by determining the relation and interactions between the concentrations of Ca, Mg and K extracted from soils and those found in onion and alfalfa tissues.

The extraction procedure was found to give good relations (r ≥ 0.848**) between the concentrations of Ca and Mg extracted from soils and those present in onion and alfalfa tissues, though interactions between the amounts of Ca and Mg extracted from soils were found.

A differentiation among soils was found upon relating the amounts of soil extracted K to its concentration in onion and alfalfa tissues. Soil extracted K was shown to be related to its preponderance (K x 100/K Ca Mg) over other extracted bases (r = 0.975**). A critical preponderance of 11% K was identified for alfalfa. The critical preponderance of K in crops appraises some of the interactions among available soil cations and, consequently, is suggested as an improved approach for predicting crop response to potassium fertilization.  相似文献   

9.
Abstract

A metal chelating exchange resin membrane was used to extract soil cadmium (Cd) and to evaluate the plant uptake of Cd from soils. Eight soils with widely varying properties and Cd levels were tested. Soil suspensions (4 g in 40 mL deionized water) were equilibrated with 5 cm2 Ca‐Chelex membrane which was retained inside a polypropylene bag and shaken at 150 rpm for 24 hrs. Resin membrane extractable Cd of the soils were correlated with Cd uptake by young wheat seedlings grown in these soils and compared with soil Cd extracted by several commonly used chemical extractants. The amounts of Cd extracted by the Ca‐Chelex membrane from all tested soils were correlated with those absorbed by young wheat seedlings or those extracted by the tested chemical extractants. The Ca‐Chelex membrane extractable Cd of the soil, however, had the strongest correlation with plant uptake Cd. It was demonstrated that the Ca‐Chelex membrane extraction is an appropriate method in estimating Cd phytoavailability of soil and is applicable to a wide range of soils.  相似文献   

10.
Abstract

The amounts and forms of zinc in twenty surface soils from Canterbury and Southland, New Zealand were determined using a sequential fractionation scheme. Total soil zinc concentrations ranged from 38.1 mg#lbkg‐1 to 113.8 mg#lbkg‐1. Although the proportions of zinc found in individual fractions varied between soils, on average approximately 3% occurred as exchangeable zinc, 5% as organic‐bound zinc, 9%, 18%, 24% was associated with manganese, amorphous iron and crystalline iron oxides, respectively, and 40% was in the residual fraction. In a group of soils formed in greywacke alluvium or loess, exchangeable zinc was inversely related to soil pH. Within the same group of soils, those of similar age with greater concentrations of total and organic‐bound zinc were present in imperfectly‐ and poorly‐drained soils compared with well‐drained soils. Zinc extracted from the soils with a range of reagents used to assess ‘plant available’ zinc was correlated strongly with the concentrations of zinc present in the exchangeable and organic‐bound zinc fractions.  相似文献   

11.
Black carbon (BC) occurs ubiquitously in the environment. Its oxidation in the laboratory yields a suite of benzene polycarboxylic acids (BPCAs), suggesting similar oxidation products in soils. Since only for a few soils the occurrence of BPCAs in the free form has been documented, screening for them in a broad range of contrasting soils was conducted. They were extracted from soil samples with 0.5 M NaOH and quantified using gas chromatography–mass spectrometry. As expected, BPCAs turned out to be as ubiquitous as BC. They were detected not only in every soil sample investigated so far, but also in samples from drill cores up to a depth of 10 m and in recently deposited calcareous tufa. The concentrations covered a range similar to that of some phenolic acids. The range exceeded those reported for low‐molecular‐weight aliphatic acids or simple sugars in soils. The distribution of BPCAs in soil profiles indicated a considerable potential of translocation within, and export from, soil, in particular of benzene hexacarboxylic (mellitic) acid. Mellitic acid may therefore be present in almost any geochemical sample affected by seepage water from soils. Its high water solubility and strong metal‐complexing ability suggest it may be involved in metal‐transport processes, at least on geological timescales.  相似文献   

12.
Many deciduous fruit tree orchard sites throughout the world are contaminated with lead (Pb) and arsenic (As) from past use of lead arsenate insecticides. The vertical distribution of Pb and As was examined in six contaminated orchard soils in the State of Washington, USA. Most of the Pb and As was restricted to the upper 40 cm of soil, with Pb concentration maxima ranging from 2.15 to 10.69 mmol/kg, and As concentration maxima ranging from 0.77 to 4.85 mmol/kg. In all cases, there were lower Pb and As concentrations at the soil surface than deeper in the profile. Arsenic was depleted relative to Pb in the topsoils and was enriched relative to Pb in the subsoils, suggesting that there has been preferential movement of As. Absolute soil enrichment with Pb occurred to depths between 15 and 50 cm. Absolute soil enrichment with As occurred to depths between 45 and > 120 cm. At 120 cm, Pb concentrations were < 0.05 mmol/kg, and As concentrations ranged from 0.07 to 0.63 mmol/kg. The deeper movement of Pb and As in the study soils relative to that reported for lead arsenate-contaminated soils elsewhere is attributed to high loading rates of lead arsenate, coarse soil texture, low organic matter content, and use of irrigation. The results indicate that Pb and As concentrations in lead arsenate-contaminated soils are high enough to be of potential environmental concern. The amount of As redistribution appears to be substantial enough to preclude some methods of remediation and to create potential risk of contamination of underlying shallow groundwater.  相似文献   

13.
Twenty-five soils, having a wide range of organic matter contents, were extracted with anhydrous formic acid containing 10 per cent acetylacetone, and the extracted material precipitated in two fractions with diisopropyl ether. Precipitates comprised from 5.1 to 51.1 per cent of the original soil organic matter, the proportion extracted tending to be greatest from acid soils of fairly high organic matter content and least from neutral or slightly alkaline soils of low organic matter content. Soil clay content appeared to have no effect on the efficiency of organic matter extraction, but was the most important soil factor governing the proportion of the total soil-N extracted. Amounts of N extracted ranged from 10.2 to 57.8 per cent of the original soil N content, extraction efficiency being greatest with soils of low clay content and low pH. There was evidence to suggest that soil clay afforded some protection to N compounds against extraction. The results indicate that formic acid/acetylacetone is most effective with soils in which much of the organic matter is only partly humified.  相似文献   

14.
The biodegradation of polyaromatic hydrocarbons (PAHs) has been well documented; however, the biodegradation of PAHs in contaminated soil has proved to be problematic. Sorption of PAHs to soil over time can significantly decrease their availability for extraction much less than for biodegradation. In this study the ability of various organic solvents to extract PAHs from coal tar-contaminated soil obtained from former manufactured gas plant (MGP) sites was investigated. Solvents investigated included acetone/hexane, dichloromethane, ethanol, methanol, toluene, and water. The extraction of MGP soils with solvents was investigated using soxhlet extraction, multiple soxhlet extractions, sonication, and brief agitation at ambient temperature with a range of solvent concentrations. Of particular interest was the documentation of the recalcitrance of PAHs in weathered MGP soils to extraction and to bioremediation, as well as to demonstrate the ease with which PAHs extracted from these soils can be biodegraded. The efficiency of extraction of PAHs from MGP soils was found to be more dependent upon the choice of solvent. The environmentally-benign solvent ethanol, was shown to be equal to if not better than acetone/hexane (the EPA recommended solvent) for the extraction of PAHs from MGP soils, brief contact/agitation times (minutes) using small quantities of ethanol (2 volumes or less) can achieve nearly quantitative extraction of PAHs from MGP soils. Moreover aqueous slurries of an MGP soils experienced less than 10% biodegradation of PAHs in 14 days while in the same period about 95% biodegradation was acieved using PAHs extracted from this soil by ethanol and subsequently added to aqueous bacterial suspensions.  相似文献   

15.
Application of legume green manure (GM) is suggested to be effective in increasing the availability of native soil phosphorus (P) and the dissolution and utilization of phosphate rock (PR)‐P by food crops. Experiments were conducted to study the dynamics of extractable P (P extracted by Bray‐1‐extracting solution) of an Ultisol amended with or without GM residues of contrasting P concentrations in the absence of growing plants. In two separate experiments, GM residues of Aschynomene afraspera (a flood‐tolerant legume) and of Crotalaria micans (upland) with varying P concentrations were added to an acidic soil amended with PR‐P or triple superphosphate (TSP) in plastic bottles. Soil moisture was brought to field capacity of the soil in the upland experiment and saturated with distilled water in the lowland setup. This was done to simulate aerobic upland and anaerobic lowland soil conditions in the relevant plastic bottles. Only P concentration of the residues added varied, while lignin and C : N ratios were similar. A temperature of 25°C was maintained throughout the experiment. Changes in soil extractable Bray‐1‐P were measured at the end of the incubation period (60 or 80 d). In the aerobic soils, extractable P in the combined PR+GM or TSP+GM treatments was significantly lower than in the PR‐ or TSP‐ treated soils. The amendment with GM residues alone significantly increased Bray‐1‐P over the unamended control in the case of the inorganic P‐fertilized GM residues. The trend in extractable P was similar in the soils incubated under anaerobic conditions. However, in the case of PR, concentrations of P extracted by Bray‐1 solution did not significantly change in the presence or absence of GM. The results suggest that the incorporation of GM residues with low P concentration does not lead to a net P release in upland or lowland soils. These results have implications for nutrient cycling in farming systems in W Africa as most of the soils are poor and very low in available P.  相似文献   

16.
Abstract

Wetland soils (hydric soils) are unique in their chemical characteristics compared to upland soils. It is known that they are capable of removing a variety of wastes from polluted water entering the wetland including metals and potentially toxic heavy metals. When these metals are determined in wetland soils, it is necessary to use the proper chemical extractant(s). Four commonly used chemical extractants (Mehlich 1, Mehlich 3, 0.1M HCl, and DTPA) for soil fertility evaluation were selected to measure metal concentrations of three different wetland soils/spoils. Soil samples were collected from the constructed wetland cells which were lined with Abernathy silt loam topsoil and two different mine spoil materials [collected from active coal strip‐mined sites in Alabama (pH 5.9) and Tennessee (pH 3.2)]. Mehlich 3 extracted the most zinc (Zn), iron (Fe), manganese (Mn), calcium (Ca), magnesium (Mg), potassium (K), sodiumm (Na), and aluminum (Al), while 0.1M HC1 extracted more cadmium (Cd), copper (Cu), and lead (Pb). Extractants followed the same trend in removing quantities of the metals from the three soil/spoil materials, with DTPA generally extracting the least amount of the metal (the trend was Mehlich 3 > 0.1N HCl > Mehlich 1 > DTPA). However, DTPA removed larger quantities of metals from Tennessee spoil compared to Alabama spoil and topsoil, suggesting the higher effectiveness of DTPA under acidic conditions. Metal concentrations in plant tissue did not show a definite trend in correlation with metals extracted by the four chemical extractants.  相似文献   

17.

A method is described for the determination of total lead in soil by atomic absorption spectrophotometry. The sample is digested with hot nitric acid. The dry residue is taken up in hydrochloric acid and excess iron is removed by extraction with acetylacetone‐chloroform. Lead is then extracted using the system DDC‐MIBK. The organic phase can be sprayed directly into the flame.

The method is not affected by elements occurring in contaminated soils. Iron is removed because a slow‐forming precipitate of the Fe‐DDC‐complex blocks the nebuliser system. The method is an improvement on other methods because no sulfuric acid is used for digestion, and therefore losses of lead by precipitation or occlusion are avoided. Tests confirm that the recommended method gives complete recovery of lead.

Lead can be determined in the range from 4 to 240 ppm in the soil. A standard soil sample has been analyzed, yielding a mean value of 125 μg Pb/g soil with a relative standard deviation of 2.4%.  相似文献   

18.
This research work intended to study the impacts of irrigation water containing various levels of copper, lead, and zinc on adsorption capacity of soil packed in 4′′ plastic columns and obtained from two locations around the city of Nablus: Salem (A) and Deir Sharaf (B). Results of simulation experiments showed an increase in the copper, lead, and zinc concentrations in soil and in leachate with increasing the amount of metal in irrigation water. Copper, lead, and zinc concentrations increased also with soil depth and duration of application. The results also indicate that the self purification of both soils was highly affected by physical factors, i.e. the intermittent application of irrigation water to the soils in the columns caused soil wetting and drying cycles whichresulted in the formation of cracks in shrinked soils specially in the top half of the columns. Crack formation is common in such clay soils due to the climatic conditions (Mediterranean type: dry summers and wet winters) and type of clay minerals in the soil. Thus, short circuiting of water through cracks results in moving contaminants fast and deep in the soil profile.  相似文献   

19.
Antioxidants are released during the NaOH extraction of soils, and this also releases phenolic compounds from plant and soil material. We hypothesized that phenolics would be important contributors to the antioxidant capacity (AOC) of soils. The concentrations of 12 phenolic compounds and the AOCs in 4 m ‐NaOH extracts of a range of UK soil types were measured. Samples of both surface and subsurface horizons were taken from 24 sites representing the major soil types (brown soils, gleys, podzols, peats and lithomorphic soils). The land use/vegetation varied from deciduous woodland through heather moorland to agricultural crops. The internal standards method was used to quantify the phenolics, which were detected by gas chromatography. The AOCs of the extracts and of standards of the individual phenolic compounds were measured using the TEAC (Trolox Equivalent Antioxidant Capacity) method. There were differences in the phenolic distributions extracted from soils with different land uses/plant inputs, as well as differences between surface and subsurface samples. A statistically significant linear relationship was found between the AOCs of the extracts and the sum of the phenolic compounds, as both these variables were positively correlated with the organic matter content of the soils. The AOCs of the individual phenols were used to calculate their contribution to the overall AOC of the extracts, and this was found to be small (approximately 1% of the total AOC). We concluded that the measured phenolic compounds were not important contributors to the AOCs of the soil extracts, and therefore that other unidentified antioxidant compounds were probably present.  相似文献   

20.
Abstract

Soils contaminated with heavy metals constitute a serious and widespread ecological problem but to clean such soils requires strong chemicals such as polycarboxylates; frequently ethylenediaminetetraacetic acid and nitrilotriacetic acid are used. However, these compounds are synthetic and toxic and their replacement by natural products such as soluble humic substances as washing agents for cleaning heavy metal polluted soils would be environmentally very attractive. In fact, such a replacement seems possible at least on cadmium and copper contaminated soil inasmuch as humic substances, depending on the concentration, were found to extract up to 45% and 54% of total cadmium and copper from a highly contaminated calcareous soil. Even though higher amounts of the two metals were extracted by ethylenediaminetetraacetic acid and nitrilotriacetic acid, the humic substances undoubtedly extracted the most reactive fractions. However, the humic substances extracted only 4% of total lead and 17% of total nickel, whereas the percentages for the synthetic polycarboxylates were about 30% for nickel and lead. Ethylenediaminetetraacetic acid and nitrilotriacetic acid may therefore be replaced by humic substances as washing agents for cadmium, copper and maybe nickel contaminated soils, whereas they seem unsuited for cleaning lead contaminated soils, at least if the soils are as calcareous as the soil tested.  相似文献   

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