Soil Cd Availability Research Articles

Contaminated agricultural soils: Trace-elements speciation, their phytoavailability and their uptake by flax plants

Flax seeds are used in animal food because of their high content in Omega 3. A number of trace-elements (TEs) - essential as micronutrients, however toxic at supraoptimal concentrations - can accumulate in this plant at quantities incompatible with their introduction in food chain. In order to control this risk and evaluate the uptake of TEs, it is necessary to assess the contents of various species of TEs in soils and plants (each organ and total contents). We were mainly interested in evaluating the availability of Cd, Cu, Ni, Pb and Zn in soils on which flax were grown. Two situations have been compared: the first corresponds to fields into which some sewage sludge were brought in agronomic doses and the second corresponds to plots of land irrigated by waste water over a 100 years period. We are currently performing TEs extractions from soils and plants using different methods: the data of sequential and total extractions (assisted by microwaves) are presented. We have studied two flax varieties in four stages of culture (sowing, stage 10cm, flowering, maturation). The content, speciation of TEs in soils as well as their transfer in flax seeds are discussed.

Phytoextraction of cadmium with Thlaspi caerulescens

The in situ phytoextraction of cadmium from soils can only be achieved using plants that are both tolerant to high Cd concentrations and able to extract sufficient amounts of the metal. However, very few plant species are capable of remediating Cd polluted soils in a reasonable time frame. This paper aims to show that the population of the hyperaccumulator Thlaspi caerulescens J. & C. Presl. from Viviez (south of France), which has a high Cd-accumulating capability, is an efficient tool to remove Cd from contaminated soils. Roots of T. caerulescens Viviez proliferate in hot spots of metals in soils which is particularly advantageous because of heterogeneity of the distribution of metal in polluted soils. Isotopic techniques showed that plants from this population acquire Cd from the same pools as non-accumulating species, but that it was much more efficient than non-hyperaccumulators at removing the metal from the soil labile pool. This is due: to (i) a specific rooting strategy, and (ii) a high uptake rate resulting from the existence in this population of Cd-specific transport channels or carriers in the root membrane. Growth and overall extraction can be improved with appropriate N fertilisation, supplied either as mineral fertilisers or uncontaminated sewage sludge. Selecting bigger plants is possible from within a suitable Cd-accumulating population to improve the phytoextraction process. Growing the Cd-accumulating populations results in a reduction in the availability of Cd and Zn as shown with field and lysimeter experiments conducted for several years. As a result, on a practical aspect, Cd hyperaccumulating populations of T. caerulescens may be used as a tool to efficiently reduce the availability of Cd in soils, providing appropriate populations are used.

Availability and Distribution of Cd, Ni, Cu, and Zn in a Northern Piedmont Biosolids-Amended Soil.

Availability and Distribution of Cd, Ni, Cu, and Zn in a Northern Piedmont Biosolids-Amended Soil.

Soil Cd availability to Indian mustard and environmental risk following EDTA addition to Cd-contaminated soil.

A pot experiment was conducted to investigate the influence of EDTA on the extractability of Cd in the soil and uptake of Cd by Indian mustard (Brassica juncea). Twenty levels of soil Cd concentration ranging from 10 to 200 mg kg(-1) were produced by spiking aliquots of a clay loam paddy soil with Cd(NO3)2. One week before the plants were harvested EDTA was applied to pots in which the soil had been spiked with 20, 40, 60...200 mg Cd kg(-1). The EDTA was added at the rate calculated to complex with all of the Cd added at the 200 mg kg(-1) level. Control pots spiked with 10, 30, 50... 190 mg Cd kg(-1) received no EDTA. The plants were harvested after 42 days' growth. Soil water- and NH4NO3-extractable Cd fractions increased rapidly following EDTA application. Root Cd concentrations decreased after EDTA application, but shoot concentrations increased when the soil Cd levels were >130 mg kg(-1) and Cd toxicity symptoms were observed. The increases in soil solution Cd induced by EDTA did not increase plant total Cd uptake but appeared to stimulate the translocation of the metal from roots to shoots when the plants appeared to be under Cd toxicity stress. The results are discussed in relation to the possible mechanisms by which EDTA may change the solubility and bioavailability of Cd in the soil and the potential for plant uptake and environmental risk due to leaching losses to groundwater.

Effect of current-season application of calcitic lime and phosphorus fertilization on soil pH, potato growth, yield, dry matter content, and cadmium concentration

Two glasshouse and three field experiments were conducted to investigate the effects of current-season application of calcitic lime and phosphorus (P) fertilizer on (i) soil pHw, (ii) growth of haulms (tops), (iii) tuber number, yield and dry matter content, and (iv) cadmium (Cd) concentrations in tubers of the potato (Solanum tuberosum L.) cultivars Russet Burbank, Crystal, and Pontiac grown in acid Entisols. Rates of calcitic lime ranged from 0 to 20 t ha−1, and rates of P, applied as single superphosphate, ranged from 0 to 100 kg ha−1. Liming increased surface (0–15 cm) soil pHw by up to 3.1 units while P fertilization increased it by only 0.3 of a unit. In the glasshouse experiments, total yields of leaves, stems and haulms were not significantly affected by the application of lime while plant height was increased. Phosphorus fertilization increased total leaf, stem and haulm yields and plant height. The number of tubers per plant and tuber yield were either unaffected (4 experiments) or decreased (1 experiment) by liming. Phosphorus fertilization significantly increased tuber yield and number in 3 experiments. The magnitude of the yield responses to applied P was greater in the glasshouse experiments than in the field experiments. Liming did not significantly affect tuber dry matter content which was however, increased by the application of P in the glasshouse experiments. There were no consistent interactions between lime and P in their effects on any of the growth or yield parameters measured. Application of lime, up to 10–15 t ha−1, significantly reduced tuber Cd concentrations in glasshouse experiments but not in field experiments. This discrepancy between field and glasshouse experiments indicates that the effects of liming on Cd availability in acid soils and on plant uptake need further investigation. Phosphorus fertilization significantly increased tuber Cd concentrations in 2 experiments. Based on our field experiments, further investigations are required to determine if banding superphosphate increases tuber Cd compared with broadcasting. It was found that for potato crops grown in acid Entisols, current-season application of calcitic lime was ineffective as an agronomic practice for growers to improve haulm growth and tuber yield response to applied P and to reduce Cd residues in tubers.

Extratores para Cd, Cu, Cr, Mn, Ni, Pb e Zn em LATOSSOLOS tratados com biossólido e cultivados com milho<A NAME="top"></A>

O uso de biossólidos (lodo de esgoto) em áreas agrícolas cria uma demanda por informações sobre o extrator mais adequado para se prever disponibilidade de metais pesados, presentes nesse resíduo, para as espécies vegetais cultivadas nessas áreas. A eficiência dos extratores HCl 0,1 mol L-1, Mehlich 3 e DTPA 0,005 mol L-1 pH 7,3 e da água régia na previsão da fitodisponibilidade de metais pesados presentes em solos tratados com biossólido foi avaliada através de um experimento com milho cultivado em LATOSSOLO VERMELHO Distrófico (LVd) e LATOSSOLO AMARELO Distrófico (LAd). As parcelas experimentais foram vasos com capacidade para 0,5 m³de terra, distribuídos em blocos ao acaso, em esquema fatorial 4 x 4, quatro tratamentos (LVd+lodo, LVd, LAd+lodo e LAd) e quatro métodos de extração com quatro repetições. O biossólido foi aplicado antes do cultivo do milho, numa quantidade total de 388 Mg ha-1, base seca, parcelada em 5 vezes espaçadas de 2 meses cada. Antes de semear o milho foi feita a amostragem da terra a 0-0,20 m, que foi analisada para teor total dos metais presentes com água régia e teores trocáveis removidos pelos extratores: solução 0,1 mol L-1 de HCl, Mehlich 3; DTPA-TEA pH 7,3. As plantas foram separadas em folha diagnose, folhas ao final do ciclo, pendão, colmo, bainha, sabugo, palha e grãos. Apesar da quantidade de biossólido aplicada aos solos, os teores totais dos metais analisados não excederam os limites críticos estabelecidos pela United States Environmental Protection Agency (USEPA) e pela Diretriz da Comunidade Européia. As correlações feitas entre teor de metais presentes nas várias partes das plantas e teores dos metais removidos pelos diferentes extratores evidenciaram que Mehlich 3 foi eficiente apenas na previsão da fitodisponibilidade de Cu e Zn. Nenhum dos extratores testados foi eficiente na previsão da disponibilidade de Cd, Cr, Ni e Pb para as plantas de milho.

Association of Cadmium in Durum Wheat Grain with Soil Chloride and Chelate‐Extractable Soil Cadmium

Cadmium uptake by food crops needs to be understood in order to limit Cd accumulation in the food chain. Cadmium is a potentially toxic heavy metal with no known benefit to humans, and plant foods are the predominant sources of Cd in human diets. In this study, 124 paired samples of soil and grain were collected from a field of durum wheat [Triticum turgidum L. subsp. durum (Desf.) Husn.] cultivar Munich in northeastern North Dakota. This field on the Langdon Research Extension Center was selected for study because it provided a range in soil pH and salinity. Cadmium in the durum grain ranged widely from 0.025 to 0.359 mg kg−1 Accumulation of Cd in grain was strongly and positively associated with soil salinity as represented by soluble chloride, soluble sulfate, or extractable Na, and also with chelate‐extractable Cd. Relationships to salinity were curvilinear. Concentrations of Cd in grain were not closely related to soil pH. The relationship of Cd in grain to the logarithm of water‐extractable soil Cl− (Clw) was especially close. A predictive model based on chelate‐extractable Cd and logCl−w in soil accounted for 66% of the variability of Cd in grain. Based on these results, and published work for other crops, we believe that the accumulation of Cd in durum wheat grain is enhanced by Cl− in the soil. Although the mechanism is not clear, it is likely to involve increased solubility or availability of soil Cd resulting from the formation of chloro‐complexes in soil solution.

Cadmium availability to wheat in five soil series from the Yonne district, Burgundy, France

Preliminary results from the French ASPITET programme demonstrated that Cd background levels in agricultural soils can vary greatly (0.02–6.9 mg Cd kg −1) depending on parent material and pedogenic processes (Baize, 1997). However, the total Cd content in soil is often not significantly related to the Cd concentration in edible plant parts. A field case study was undertaken across the southern part of the Yonne district, Burgundy, France. This area has various soil series with either low or high geochemical Cd content in the topsoil. Cd availability in soils sampled at 16 sites belonging to five soil series was investigated using single extractions. In addition, shoots (at stem elongation) and grains (at harvest) of field-grown wheat were collected at the same sites and analysed for macronutrients and trace elements. Cd concentrations in grain varied from 0.015 to 0.146 mg Cd kg −1 DM depending on soil characteristics, soil series, and plant mineral composition. Cd grain concentrations did not reflect total Cd content in the surface soil layer; however, they were correlated with Cd extracted by a 0.1 M calcium nitrate unbuffered solution, and to a lesser extent with either soil pH or CEC. These three parameters may be useful guides to predict Cd in wheat grain harvested in the Yonne district. An inverse relationship was found between Cd and Cu contents in grain. The highest Cd concentrations in wheat grain occurred in plants grown on Aubues soils which had marginal Cu and Zn deficiencies in shoots. In order of Cd accumulation in wheat grain, soil series may be ranked as follows: Domérien < Carixien, Terres Noires < Sols Marron < Aubues.

Kinetics of Cadmium Release from Soils as Influenced by Organic Acids: Implication in Cadmium Availability

AbstractThe low‐molecular‐weight organic acids (LMWOAs) secreted by plant roots modify the mobility of Cd through formation of soluble complexes in the soil rhizosphere; the kinetics of Cd release as influenced by organic acids and its impact on Cd bioaccumulation remains to be established. The influence of LMWOAs (10−3 and 10−2 M), viz., acetic, citric, oxalic, fumaric, and succinic acids, which are present in the soil rhizosphere, on the kinetics of Cd release from selected soils (Luseland, Waitville, and Jedbergh) of Saskatchewan, Canada, was investigated at 25°C and at an ionic strength of 0.1 M NaNO3. It was observed that the Cd release from the soils increased initially up to a reaction period of about 2 h and then slowly decreased with time. With time, the LMWOAs were apparently microbially degraded and the soil solution Cd2+, which was transformed from the Cd‐LMWOA complexes by microbial degradation, was adsorbed onto the negatively charged soil particles. Increasing amounts of Cd were released from the soils to the soil solution with the renewal of LMWOAs after every 2 h. The short‐term (reaction period of 0.25 to 1 h) kinetics of Cd release from the soils was described by a parabolic diffusion kinetic model. The overall diffusion coefficient of the Cd release from the soil and the Cd released by the renewal of LMWOAs followed the same trend as the Cd availability index of the soils: Luseland &gt;&gt; Waitville &gt; Jedbergh. Thus, the results presented in this investigation indicate the importance of the kinetics of the Cd release from the soils by the LMWOAs excreted by root exudates in understanding the availability of soil Cd.

Influence of phosphate on cadmium adsorption by soils

In batch equilibrium experiments, it was found that orthophosphate increased Cd adsorption and decreased its desorption by three representative soils. Ion activity products in the equilibrium solution indicated that cadmium activity was under saturated with respect to Cd3(PO4) (s) on the Red earth(Typic Hapludult) and the Yellow-brown earth(Typic Hapludalf). With the calcareous Yellow fluvo-aquic soil(Typic Haplaquent), phosphate enhanced Cd adsorption at lower Cd concentration but it decreased the adsorption at high Cd level. Ion activity products and solubility diagrams suggested that at high Cd level Cd3(PO4)2 had formed and the activity of Cd in solution was controlled by this precipitate. This implies that the formation of Cd3(PO4)2 (s) is unable to decrease Cd activity so long as soil adsorption sites are unsaturated by Cd. It is suggested from these results that one could not expect decreasing soil Cd availability by phosphate fertilization unless a simultaneous rise in soil pH also occurs.

Effects of nitrogen-containing fertilizers on solubility and plant uptake of cadmium

In a pot experiment, three N-fertilizers, differing in NO−3 and NH+4; content, were compared in terms of their effects on the extractability of soil Cd in 1M ammonium acetate at pH 7 and on the uptake of native and added Cd by winter rape (Brassica napus L. var. oleifera Metzger). In another similar experiment the Cd-availability in soils receiving NPK-fertilizer applied in a concentrated, granulated form was compared to that in soils receiving a uniform application of dissolved NPK-fertilizer. Both loamy sand and clay soils were used. With the N-fertilizers levels of extractable soil Cd and plant Cd-contents were lowest in the nitrate of lime treatment, highest in the ammonium sulphate treatment and intermediate in the nitro-chalk treatment. The addition of 1 mg kg−1 DW Cd to the soil increased Cd-levels but did not change the response pattern. There was a strong association between the effects of the various fertilizers on Cd availability and their effects on soil pH: the stronger the acidifying effect the higher the Cd availability. When applied at a low dose, granular NPK was more effective than dissolved NPK at enhancing plant uptake of Cd from both soils, but this was not the case when applied at a higher dose to the sand. The two forms of NPK differed little in their effect on extractable soil Cd. Plant uptake of Cd was greater from soils receiving granular NPK with a high Cd-content than from those receiving granular NPK low in Cd. In both experiments extractable Cd was taken up to a greater extent from the sand than from the clay. An increase in fertilizer dose generally resulted in an increase in levels of soil-Cd and in Cd concentrations in the plants.

Cadmium Buffering Capacity and Accumulation in Swiss Chard in Some Sludge‐Amended Soils

AbstractCadmium sorption by soils could be an important factor regulating the plant availability of soil Cd. Five soils containing varying amounts of Cd resulting from previous sludge application were analyzed for residual Cd availability under field conditions using Swiss chard (Beta vulgaris L.) as an indicator plant. The Cd accumulation was not highly correlated with DTPA (diethylene‐triamine‐pentaacetic acid)‐extractable Cd (R2 = 0.53). This result may be explained by a dissimilar response of plant Cd and DTPA Cd to soil pH. However, DTPA extracted 50 to 75% of sorbed Cd, depending on soil type. The recovery was little affected by the quantity of Cd sorbed. As such, DTPA Cd could be used to predict Cd accumulation by converting it to the quantity of Cd sorbed (Cds). The Cds was combined with the pH‐dependent Cd buffering capacity (BC) to obtain Cds/BC, an intensity factor for soil Cd. The buffering capacity is defined as the slope of the Cd‐sorption isotherm. The Cds/BC and plant Cd were highly correlated over all the soils, using the Michaelis‐Menten equation as a model (R2 = 0.83).

Yield and uptake response of lettuce to cadmium as influenced by nitrogen application

A screen house experiment was conducted to determine the effect of N (0, 50, 100 and 150 mg N kg−1) and Cd (0, 5, 10, 25 and 50 mg Cd kg−1) on growth and concentration and uptake of N and Cd in lettuce grown for 70 days. Nitrogen application increased significantly fresh yield, dry matter yield, N concentration and uptake, whereas these parameters were significantly decreased by Cd application at all levels of N. The concentration and uptake of Cd were significantly increased by Cd application at all levels of N. This increased Cd uptake was related to increased availability of Cd in soil. Application of N upto 100 mg N kg−1 increased Cd uptake, whereas there was sharp reduction in Cd uptake at 150 mg N kg−1 treatment at all levels of Cd. The plant dilution effects and reduced translocation of Cd from roots to tops or the competition at the root absorption sites at highest level of N seem to be the mechanisms responsible for N suppressed Cd uptake in this study.

THE EFFECT OF SULFATE ON THE AVAILABILITY OF CADMIUM1

The objective of the study was to determine the effect of sulfate salinity on the availability of Cd in soil. Specifically the study consisted of a greenhouse experiment with Swiss chard (Beta vulgaris Cicla) as the biological indicator of Cd in two sets of an acid soil treated with 0.25, 1.00, and 2.50 mg Cd kg−1 in combination with four rates of Na2SO4 ranging up to 30 mol m−3 in the saturation extract (H2O). One set was limed with CaCO3; the other was left as an acid soil. The content of Cd in shoots of Swiss chard after 9 wk postemergence was taken as the measure of available Cd. Immediately after the plants were harvested, the soil solution was analyzed for cations and anions; these data were taken as input data to chemically speciate Cd in the soil solution. The total concentration of Cd in soil solution, CdT, was found to consist of principally Cd2+, CdCl+, and CdSO4° in the unlimed soil. The speciation of the soil solution for the limed soil show CdT to comprise the above plus CdCO3+. Regression analysis of leaf Cd in relation to CdT, Cd2+, acd2+, CdCl+, CdSO4°, and CdCO3° showed leaf Cd to be primarily a function of the aCd2+ in the acid series and CdT in the alkaline series. The availability of soil solution Cd as judged by the Cd concentration of Swiss chard (shoot) was substantially greater for the unlimed soil.

The Effect of Chloride on the Availability of Cadmium

AbstractCadmium complexes readily with chloride and sulfate; hence, increases in soil salinity may influence its availability. To evaluate the effect of chlorinity, a major component of soil salinity, the following study was undertaken. A greenhouse experiment was conducted with Swiss chard (Beta vulgaris Cicla) as the biological indicator of available Cd in soil at pH 4.0 and pH 7.0 and treated with three levels of Cd(NO3)2 combined with five levels of CaCl2. The soil solution was analyzed for cations and anions; these analyses were used as input data to chemically speciate Cd in the soil solution. Under these treatments, the total concentration of Cd in the soil solution, CdT, was found to exist principally as Cd2+ and CdCl+. Multiple regression analysis of leaf Cd data in relation to the concentration of CdT, Cd2+, and CdCl+ showed leaf Cd to be primarily a function of the Cd2+ concentration.

Cadmium Availability to Rice in Sludge‐amended Soil under “Flood” and “Nonflood” Culture

AbstractRice plants (Oryza sativa var. ‘Colusa’) were grown to maturity in pots containing a soil (Domino silt loam, pH 7.5, Xerollic calciorthid) amended with 1% sewage sludge enriched with variable amounts of CdSO4 ranging up to 640 µg Cd/g. Two sets of soil cultures were used, one for rice under continuous flood and the other under nonflood conditions. Grain production for rice under flood management was relatively unaffected by the Cd treatment; 25% yield decrement was associated with a treatment of 320 µg Cd/g. Under nonflood management, however, a comparable decrement in grain production was observed with a treatment of only 17 µg Cd/g. The Cd content of mature leaves at early flowering varied from approximately 0.3 µg Cd/g for the controls to 2.8 µg Cd/g for plants receiving the highest Cd treatments. Leaf Cd values were slightly higher under the nonflood culture. The Cd content of the grain under nonflood management was approximately 55% greater than that of grain under flood management. The Cd content of mature leaves correlated with grain production (r = 0.872***) for rice produced under either flood or nonflood culture. Chemical analysis of saturation extracts revealed greatly reduced Cd concentrations in soil solutions under flood management which may account for the greater tolerance of the cultivar to soil Cd under flood culture. This reduced availability of Cd in flooded soils is attributed to precipitation of CdS.