A simplified method for the extraction of the metals Fe,Zn, Cu,Ni, Cd,Pb, Cr,Co and Mn from soils and sewage sludges

The method described for digestion of soil samples with aqua regia is simple, flexible and safe to operate with large sample throughout. At least nine metals can be determined in the resulting solutions with errors of <5%. The results compare favourably with those from reflux aqua regia and averaged 88% of the certified total values for reference soils and 88% of those for reference sewage sludges.     

Extractable copper,lead, zinc and cadmium in Northern Ireland soils

A survey of extractable copper, lead, zinc and cadmium in Northern Ireland's top soils was carried out to see if the trace element concentrations could be related to the parent material of the soils and to the influence of human activity. Using ordnance-survey identification, 1305 samples were selected as representative of the soils of Northern Ireland. Duplicate subsamples of each soil were shaken with 0.05M EDTA (pH 7.0) for 60 min and the supernatant analysed for copper, lead, zinc and cadmium by atomic absorption techniques. Ranges and medians for each trace element are recorded and comparisons with results of copper reported for other countries have been identified. Relative distribution diagrams are presented for each of the elements under investigation and computer-drawn symbol maps have been produced showing the distribution of the concentration of each element in comparison to the parent geology. Finally correlation coefficients between the concentration of each trace element and the ammonium acetate/acetic acid (pH 4.2) extracted phosphorus and potassium have been calculated and used to show that a specific relationship between the extractable trace elements and man's additions to the soil, as indicated by the soil fertility, is poorly developed.     

Phytoavailability, human risk assessment and transfer characteristics of cadmium and zinc contamination from urban gardens in Kano, Nigeria

BACKGROUND: Quantitative data about phytoavailability and transfer into consumed plant parts for heavy metals in intensively managed urban vegetable production areas of sub‐Saharan Africa are scarce. We therefore studied the transfer of zinc (Zn) and cadmium (Cd) from soil to the root and subsequent translocation to edible portions of four vegetables in six urban gardens. RESULTS: While respective diethylenetriaminepentaacetic acid (DTPA)‐available Zn and Cd concentrations ranged from 18 to 66 mg kg^?1 and from 0.19 to 0.35 mg kg^?1, respectively, in soils, total Zn and Cd were 8.4–256 mg kg^?1 and 0.04–1.7 mg kg^?1 in shoot parts. Metal transfer factor (MTF) ratios were higher in Zn (0.2–0.9) than in Cd (0.1–0.6). Our data suggest that total Zn concentration in soil is a reliable indicator to assess its transfer from soil to crop in lettuce, carrot and parsley, while for Cd DTPA‐extractable concentration may be used to estimate soil–crop transfer of Cd in amaranthus and carrot. Overall, Cd was more easily translocated to the aerial plant parts than Zn. CONCLUSION: Zinc and Cd accumulation by vegetables in our soils is mainly a metabolically controlled process. Such accumulation can contaminate the ecosystem but under our conditions intake and ingestion of these metals will likely have to occur over a prolonged period to experience health hazard. Copyright © 2011 Society of Chemical Industry     

The application of regional geochemical reconnaissance data in areas of arable cropping

Copper, magnesium, manganese and zinc have been studied in stream sediments and soils in five representative areas of arable cropping in southern and eastern England. Results have been assessed on the one hand in relation to the geochemistry of bedrock and soil parent materials, and on the other to crop production. Stream sediment data closely reflected the total concentration of copper, magnesium and zinc in soils and at the same time were proportionately related to “available” levels of copper and magnesium in soils. On the basis of reported problems and field trials, concentrations of less than 7 parts/10⁶ Cu and 600 parts/10⁶ Mg in sediments are likely to delineate areas within which a proportion of soils are deficient in these elements, possibly leading to a reduction in yields in sensitive arable crops. Zinc data for sediments and soils were difficult to evaluate in the absence of recognised deficiencies in field crops in Britain. The marked effect of soil Eh/pH on the mobility of manganese in soils and on its availability to plants limits the use of this technique in predicting deficient areas. The possible importance of marginal soil deficiencies of copper leading to reduced yields in cereals is discussed together with the potential value of regional geochemical maps in delineating areas where such problems may be of economic significance.     

Chemical speciation and bioavailability of selenium in the rhizosphere of Symphyotrichum eatonii from reclaimed mine soils

Knowledge of rhizosphere influences on Se speciation and bioavailability is required to predict Se bioavailability to plants. In the present study, plant-availability of Se to aster (Symphyotrichum eatonii (A. Gray) G.L. Nesom) was compared in rhizosphere soils and nonrhizosphere (bulk) soils collected from a reclaimed mine site in southeastern Idaho, U.S. X-ray spectroscopy was used to characterize the oxidation state and elemental distribution of Se in aster roots, rhizosphere soils, and bulk soils. Percent extractable Se in aster rhizosphere soil was greater than extractable Se in corresponding bulk soils in all samples (n = 4, p = 0.042, 0.051, and 0.052 for three extractions). Selenium oxidation state mapping of 28 regions within the samples and X-ray absorption near edge structure (XANES) spectra from 26 points within the samples indicated that the rhizosphere and bulk soil Se species was predominantly reduced Se(-II,0), while in the aster roots, high concentrations of Se(VI) were present. Results show that within the rhizosphere, enhanced Se bioavailability is occurring via oxidation of reduced soil Se to more soluble Se(VI) species.     

Speciation of Se and DOC in soil solution and their relation to Se bioavailability

A 0.01 M CaCl(2) extraction is often used to asses the bioavailability of plant nutrients in soils. However, almost no correlation was found between selenium (Se) in the soil extraction and Se content in grass. The recently developed anion Donnan membrane technique was used to analyze chemical speciation of Se in the 0.01 M CaCl(2) extractions of grassland soils and fractionation of DOC (dissolved organic carbon). The results show that most of Se (67-86%) in the extractions (15 samples) are colloidal-sized Se. Only 13-34% of extractable Se are selenate, selenite and small organic Se (<1 nm). Colloidal Se is, most likely, Se bound to or incorporated in colloidal-sized organic matter. The dominant form of small Se compounds (selenate, selenite/small organic compounds) depends on soil. A total of 47-85% of DOC is colloidal-sized and 15-53% are small organic molecules (<1 nm). In combination with soluble S (sulfur) and/or P (phosphor), concentration of small DOC can explain most of the variability of Se content in grass. The results indicate that mineralization of organic Se is the most important factor that controls Se availability in soils. Competition with sulfate and phosphate needs to be taken into account. Further research is needed to verify if concentration of small DOC is a good indicator of mineralization of soil organic matter.     

Biogenic phosphate minerals in manure: implications for phosphorus loss to surface waters

Phosphorus (P) is present in waterways throughout the United States at concentrations that impair water quality. Agriculture, particularly livestock production, has been identified as a major cause of this impairment Excess manure P applied to croplands has increased P losses in runoff, leading to surface water eutrophication. We conducted a long-term (36-week) incubation with poultry and dairy manures applied to a silt loam soil to elucidate mechanisms controlling manure P loss to water. Manures were applied to supply the same total P rate to soils with different antecedent plant-available P concentrations (soil test P). There was a strong synergistic effect between dairy manure and soil test P on water extractable P, while soil test P did not affect P loss from poultry manure-amended soils. Using scanning electron microscopy and energy dispersive X-ray spectroscopy, we found that poultry manure contained sparingly soluble calcium and magnesium phosphate minerals that controlled soil solution P concentrations, while dairy manure did not These minerals resemble other biogenic phosphate minerals. Our findings refute current assumptions that all manure P behaves similarly in soils and that organic forms control manure-soil P loss to water.     

Simplified method for determining cadmium concentrations in rice foliage and soil by using a biosensor kit with immunochromatography

BACKGROUND: The behavior of cadmium in ecosystems needs to be monitored because of the human toxicity of this heavy metal. The need recently arose for a simple and quick on‐site test for trace levels of Cd in food and environmental samples. In response, an immunochromatographic assay kit for detecting Cd was manufactured by Kansai Electric Power Co. of Japan. This kit uses the antigen–antibody complex reaction between the Cd–EDTA complex and an anti‐Cd–EDTA antibody and shows the results in terms of the degree of color developed on a test paper. We previously reported the successful use of this kit to determine Cd concentrations in brown rice. Here, we applied the kit to the determination of Cd concentrations in rice foliage and soil. RESULTS: Cadmium in rice foliage was not extracted successfully by the method used for brown rice. However, it was successfully extracted by 0.1 mol L^?1 HCl solution at a rice foliage:HCl ratio of 1:20, and coexisting metals were removed sufficiently by the column treatment. The Cd concentrations determined by immunochromatographic assay were well correlated with the values obtained by acid decomposition and inductively coupled plasma mass spectrometry. The 0.1 mol L^?1 HCl‐extractable Cd concentration in soil was also determined successfully with the kit. CONCLUSION: Approximate Cd concentrations in rice plants and 0.1 mol L^?1 HCl‐extractable Cd concentrations in soil can be monitored easily and quickly by this method at locations where facilities for acid digestion and precision analysis are not available. Copyright © 2009 Society of Chemical Industry     

Soil and vegetable compositional relationships of eight potentially toxic metals in urban garden fields from northern Nigeria

BACKGROUND: Human exposure to heavy metals is attributed to consumption of vegetables raised in polluted soil environment. We examined the concentrations of As, Cd, Co, Cr, Cu, Ni, Pb and Zn in soils and lettuce (Latuca sativa) and amaranthus (Amaranthus caudatus) in 15 garden fields under long‐term wastewater irrigation. RESULTS: The concentrations of As (0.3–2.1 mg kg^?1), Cd (0.07–0.3 mg kg^?1), Co (4.6–9.1 mg kg^?1) and Cr (21.6–36.2 mg kg^?1) in the gardens were consistent with background concentrations in soils, but Ni (12.6–25.7 mg kg^?1), Cu (12.5–24.6 mg kg^?1), Pb (25.7–71.6 mg kg^?1) and Zn (52.3–158 mg kg^?1) concentrations were double the concentrations normally encountered in arable fields in the region. The concentrations of Cd and As in the vegetables were within safe limits, but Co (0.14–0.67 mg kg^?1 fresh weight (fw)) and Ni (1.0–2.7 mg kg^?1 fw) concentrations in lettuce were relatively high for leaf vegetables. The concentration of Pb (0.65–4.80 mg kg^?1 fw) was above safe limit of 0.3 mg kg^?1 fw, while the concentrations of Cu (1.3–2.7 mg kg^?1 fw and Zn (10.2–23.6 mg kg^?1 fw) were close to the unsafe limits for leaf vegetables. There were no strong linear correlations between soil metal concentrations and bio‐concentrations in the vegetable crops. CONCLUSION: We surmise that leaf vegetables can accumulate metals in their tissues to unsafe levels even when total metal concentrations in these soils are below the allowable concentrations in agricultural soils. Copyright © 2008 Society of Chemical Industry     

The availability to pasture plants of native and applied soil cobalt in relation to extractable soil cobalt and other soil properties

In pot trials using a range of soils from South-East Scotland, plant cobalt concentrations were significantly correlated with the amounts of cobalt extracted from soil with 0.05 M calcium chloride. Plant cobalt concentrations were also correlated with soil pH, showing a decrease with increasing soil pH. There were no significant correlations between plant cobalt concentrations and 0.5 M acetic acid-extractable cobalt, 0.04 M EDTA-exttactable cobalt, isotopically exchangeable cobalt or total soil cobalt. Uptake of cobalt by ryegrass from cobalt added to the soil was inversely related to both the ability of the soil to sorb cobalt and to soil pH.     

Interactions between soil and fertiliser in the supply of nitrogen to ryegrass grown on 21 soils

Perennial ryegrass (Lolium perenne L.) was grown in pots on 21 UK soils, both with and without fertiliser N. The fertiliser N was applied in six equal applications of ¹⁵N-labelled ammonium nitrate, each at the rate of 120 mg N per pot. The first application was mixed thoroughly with the soil, while subsequent applications were made in solution to the soil surface, after each of the first five of the six harvests of herbage. In the absence of fertiliser N, the proportion of the total soil N taken up by the plants, including stubble and roots at the sixth harvest, varied between 1.5 and 4.0%. In the presence of fertiliser N, the proportion varied between 2.1 and 4.7%. The apparent recovery of the fertiliser N was calculated from the difference between the amounts of N in the plants that received fertiliser N and in those that did not, expressed as a percentage of the amount applied. The actual recovery of the applied fertiliser N was determined by analysis of the plant material for ¹⁵N. With all soils at the first harvest, the apparent recovery was greater than the actual recovery. When calculated over all six harvests, apparent recovery of the total amount of fertiliser N was generally close to the actual recovery. This difference from the first harvest probably reflected (i) a reduction in the extent of turnover between fertiliser N and soil N when the fertiliser N was applied to the surface and (ii) a virtually complete uptake of available soil N by the end of the experiment, in both the absence and presence of fertiliser N. Differences between the 21 soils in actual recovery were not closely related, either positively or negatively, to a range of measured soil properties. A mean of 17.2% of the labelled fertiliser N was retained in the soil (excluding visible roots) at the end of the experiment. The lowest retention (6.2%) occurred with the soil which had the lowest contents of organic matter and silt plus clay but, with the other soils, the extent of retention varied only between 14.7 and 22.0% of that applied, and was not closely related to contents of total organic matter or macro-organic matter, or to the C:N ratio of the whole soil or the macro-organic matter.     

Forage quality and tannin concentration and composition of a collection of the tropical shrub legume Flemingia macrophylla

A collection of 23 Flemingia macrophylla (Willd.) Merrill accessions of different growth habits and contrasting digestibility and one Flemingia stricta reference accession were assessed for forage quality with particular emphasis on digestibility, condensed tannin concentration and fiber content. Large differences in in vitro dry matter digestibility (IVDMD) (356 to 598 g kg^?1), content of crude protein (CP) (121 to 254 g kg^?1) and extractable condensed tannins (CT) (0 to 268 g kg^?1), protein‐binding capacity of extractable CT or astringency (1.7 to 7.9 protein‐binding entities) (PBE) and monomer composition of extractable CT were detected. IVDMD and extractable CT were negatively correlated and extractable CT was positively correlated with protein‐binding capacity. Prodelphinidin was positively and propelargonidin negatively correlated with protein‐binding capacity of extractable CT. The accessions CIAT 18438, CIAT 21083, CIAT 21090 and CIAT 22082 were superior to the most widely used accession CIAT 17403 in terms of forage quality and could be an option in production systems with acid infertile soils. In future evaluations, particular attention needs to be paid to chemical and structural features related to the composition of extractable CT and their effect on nitrogen utilization by ruminants. Copyright © 2006 Society of Chemical Industry     

Uptake of copper,nickel and zinc by crops growing in contaminated soils

A series of three replicated pot trials is reported in which various crops were grown in soils having enhanced concentrations of copper, nickel and zinc. Concentrations of these elements in the tops of plants harvested at their most sensitive stage were compared with ‘total’ and ‘extractable’ concentrations in soil and with concentrations in soil solutions. There was little difference between the relationships of ‘total’ and ‘extractable’ soil metal and concentrations in plant tissue. In general, the correlation between concentrations of metals in soils and plants was unpredictable. Plants differed in their efficiency of uptake of elements; lettuce assimilated more than the other crops tested (barley, rape and ryegrass). Similarly, soil concentrations of the elements required to achieve toxic thresholds in plant tops increased in the order lettuce, ryegrass, rape and barley. Measurements made with conventional extractants of copper, nickel and zinc in soils can be of value in predicting plant uptake and hence toxicity, only if appropriate calibration curves plotting extractable soil metal against plant uptake are at hand for the particular soils and plants under consideration. Mild extracts are more sensitive to the soil properties, especially pH value, which determine plant uptake and results with metals in soil solution were promising, especially for zinc. Nevertheless, soil analyses for copper, nickel and zinc are not always closely associated with their likely toxicity to crops.     

Effects of long-term herbicide use,irrigation and nitrogen fertiliser on soil fertility in an apple orchard

In 1972 an experiment was set up to investigate the long-term effects of herbicide, irrigation and two rates of nitrochalk fertiliser application on soil fertility in a Cox's Orange Pippin apple orchard. Samples taken in 1986 showed that uncultivated soil which had been maintained bare by herbicide had much lower organic C, total N and extractable K and Mg concentrations than soil which had been maintained under grass. Extractable P concentrations were lower in soil under grass than in soil under herbicide. In the absence of grass, soil pH was slightly lower than in its presence. All these effects were much greater at depths above 7·5 cm than below. Irrigation of the grass slightly increased organic C and total N levels at 0–7·5 cm compared with unirrigated grass but had no effect on extractable P, K and Mg. Increasing the fertiliser rate from 63 to 189 kg N ha^?1 had no effect on organic C, total N, extractable P and K. Yet, throughout the soil profile, extractable Mg concentrations were greater at the low than at the high N fertiliser rate. In a seedling growth test on soil taken from the orchard in 1988 (and confirmed to be free from residual herbicide), apple seedlings grown in soil which had previously been under grass grew significantly better than those in soil which had been bare. These differences were ascribed to a greater rate of N mineralisation in the soil formerly under grass. The results of this trial indicate that to safeguard soil fertility it is necessary to maintain a grass cover in the orchard. In addition, fertiliser application on newly planted trees should be adjusted to take account of the presence or absence of grass in the previous soil management treatment.     

Effects of soil pH on the uptake of Al,F and other elements by tea plants

Soil extractable Al, F and Zn concentrations decreased whereas extractable Ca, Cu, K, Mg, Na and P concentrations increased when the soil pH was raised from 3 to 6. These trends led to a decrease in growth of tea seedlings as determined by measurements of relative dry weight gain (RDW), relative leaf number gain (RLN) and relative leaf area gain (RLA). Tea seedlings of both ‘large‐leafed’ and ‘small‐leafed’ varieties grown in soils at pH 3 and 3.5 were the tallest and healthiest, while those at pH 6 died after 3 months. The large‐leafed variety showed higher growth rates than the small‐leafed variety. The highest (p < 0.05) amounts of Al and F, 4225 and 430 mg kg^?1 respectively, were found in seedlings under pH 3.5 treatment. When Al and F concentrations in seedlings increased, elements such as Ca, Mg, Na and Zn gently decreased (p < 0.05) whereas P increased. K and Cu were not affected. The results indicated that soil pH values higher than 4 reduced Al and F concentrations in tea plants. © 2001 Society of Chemical Industry     

Soil selenium treatments to ameliorate selenium deficiency in herbage

Sodium selenite, sodium selenate, and sodium selenate in a pill formulation were applied to three soils known to produce Se-deficient herbage ( < 100 μg Se kg^?1 dry matter (DM)). The ability of the salts, applied in spring 1985, to ameliorate Se deficiency was followed over 3 years by taking four harvests each year. Selenate treatment at 10 g Se ha^?1 and selenate prill treatment at 20 g Se ha^?1 produced herbage with Se levels (geometric means) of between 0.57-0.86 and 1.79-1992 mg kg^?1 DM respectively in the first spring harvest after treatment. Selenite was less potent and selenite at 100 g Se ha^?1 produced a response in herbage closely similar to that of selenate at 10 g Se ha^?1. Even at 300 g Se ha^?1 the selenite treatment produced herbage with only 1.00-1.36 mg Se kg^?1 DM at the first harvest. Application of selenate in the prill form at 60 g Se ha^?1 produced herbage potentially toxic to grazing animals with 4.81-4.94 mg Se kg^?1 DM. The addition of fertiliser N to Se-treated plots increased total Se uptake at the first harvest by a factor of 4 and had a small effect on Se concentration. The Se concentration levels in herbage from Se-treated plots declined exponentially (t_1/2 = 21-43 days). On one soil derived from Lower Old Red Sandstone and lava, selenite at 300 g Se ha^?1 gave herbage with Se contents significantly above background (P < 0.05) in all harvests over 3 years.     

Indicator to predict the movement of phosphorus from soil to subsurface flow

The movement of phosphorus (P) in subsurface flow can contribute to losses from agricultural land. This study aims to identify a soil P threshold above which P loss is likely to accelerate as a function of soil and management type. Lysimeters (25 cm i.d. by 30 cm deep) were taken of four soils from agricultural watersheds in Pennsylvania and New York. The soils had a range of Mehlich-3 extractable P (7-517 mg of P kg(-1)) in surface soil (0-7.5 cm for grassland and 0-23 cm for cultivated/arable) and reactive P, filtered <0.45 microm (RP(<0.45 microm) in subsurface flow (0.007-1.53 mg of P L(-1)). The loss of P from lysimeters increased greatly when Mehlich-3 extractable P was in excess of a mean concentration of 280 mg kg(-1), the degree of saturation of P sorption sites exceeded 38%, and the corrected P sorption strength (corrected for desorption) derived from the monolayer Langmuir equation was less than 0.07 L of P mg(-1). Of these variables, P sorption strength was most consistently related to RP(<0.45 microm) in subsurface flow across a range of soil managements. Use of the corrected Langmuir sorption strength parameter to estimate subsurface flow RP(<0.45 microm) derived from four U.S. soils was tested on four soils of different physiochemical characteristics (one calcareous) from the U.K. The U.K. soils showed similar concentration trends to the U.S. soils, with elevated RP(<0.45 microm) below a sorption strength of 0.07 L of P mg(-1). We propose that the P sorption strength derived from the monolayer Langmuir equation may be used to estimate the potential for P loss in subsurface flow, when simpler environmental tests such as P saturation derived from acid ammonium oxalate extraction are unclear or unsuitable.     

Organochlorine insecticide residues in earthworms from arable soils

Six species of earthworms from an arable soil were analysed for residues of aldrin, dieldrin, DDT and γ-BHC. The ratios between the concentrations of γ-BHC, aldrin + dieldrin and p,p′-DDT + p,p′-DDE in the earthworms and in the soil (concentration factors) were similar but the residue concentrations were consistently higher in the smaller more shallow-living species Allolobophora caliginosa, A. chlorotica and A. rosea than in the larger deeper-living species Lumbricus terrestris, A. longa and Octolasion cyaneum. In arable field plots, dieldrin residues in A. longa and A. chlorotica increased with increasing concentrations in the soil but the concentration factors decreased. The concentrations of residues in earthworms (W) appear to be related to those in the soil (S) by an equation of the form W = aS^b where a and b are constants, the latter being about 0.79 for a wide range of residue data embracing the uptake of aldrin-dieldrin, DDT components, and γ-BHC by earthworms.     

Anthocyanin dyes extracted from grape pomace for the purpose of textile dyeing

BACKGROUND: Pomace from different grape varieties was studied with regard to the content of extractable anthocyanins. RESULTS: Total anthocyanin concentrations of 24.5–126 mg dm^?3 were found in the extracts. The amount of extractable pigment was dependent on the variety of grape. The extracts were applied in textile dyeing operations using cotton fabric pre‐mordanted with tannin as textile substrate. Red/violet shades were obtained that showed good water‐fastness; however, limited light‐fastness indicated need for improvement to fulfil requirements for textile application. CONCLUSION: Colour measurement by means of CIE‐Lab coordinates and Kubelka–Munk value showed a direct correlation between extractable anthocyanin concentration and colour depth of the dyed material. Thus the analytically determined concentration of anthocyanins in the aqueous extract can serve as a measure of quality of grape pomace as raw material for textile dyeing application. Copyright © 2007 Society of Chemical Industry     

Removal of soluble organic carbon from winery and distillery wastewaters by application to soil

A logistic model was used to describe the removal of water-soluble carbon from synthetic winery and distillery wastewaters containing ¹⁴C-labelled lactic acid and glycerol after their application to the top-soils of a brown earth and a solod. Decreases in the radioactivity of soil extracts during the first hour after application were ascribed to microbial uptake and adsorption. Oxidative microbial decay was responsible for the removal of the remaining ¹⁴C of the solution to concentrations of less than 5% of the applied ¹⁴C, with removal times dependent on the duration of a lag period (when present) and the rate of decay. Soils from existing wastewater disposal sites containing adapted populations of micro-organisms had shorter lag periods and faster rates of oxidative decay than newly exposed soils. When the loading of organic material was increased, higher concentrations of added ¹⁴C remained in the soil solution after initial microbial uptake or adsorption, and the lag periods were often prolonged. Their combined effects could not be fully offset by concurrent increased rates of oxidative microbial decay, which overall resulted in longer removal times. The disappearance of extractable ¹⁴C to concentrations of less than 5% of input ¹⁴C was used as the basis for determining the minimum times required between successive irrigations with wastewater, which increased in the order of acclimatised solod (0.3–1.4 d) < acclimatised brown earth (0.7–2.6 d) < non-acclimatised brown earth (1.1–4.5 d) < non-acclimatised solod (0.7–4.8 d). Estimates based on the evolution of ¹⁴CO₂were found to be less reliable, due to the continuous turnover of the ¹⁴C of the biomass after the extractable ¹⁴C had disappeared.