RESUMEN
Phosphorus (P) plays an important role in immobilizing heavy metals (HMs), thereby preventing their accumulation, especially in edible parts of crops. In this study, vermicompost (VM) and chemical fertilizers (CFs) were used as soil amendments to increase the available P concentration in soil contaminated with cadmium (Cd) and nickel (Ni), with the aim of reducing their bioavailability, uptake, and bioaccessibility. Using CF and VM as soil amendments substantially increased the available P and exchangeable potassium concentrations in the soil. Furthermore, VM addition led to an increase in OM content and in exchangeable calcium and magnesium, resulting in the improved growth of lettuce. It also reduced the uptake of Cd and Ni in the two lettuce cultivars tested in the study. However, CF addition boosted the accumulation of Cd and Ni by increasing the soil acidity. CF addition, and especially VM addition, altered the chemical forms of Cd and Ni from active to inactive. Overall, the results of this study underscore the positive impact of using VM as a soil amendment on lettuce growth and the prevention of HM accumulation in edible parts of lettuce. VM addition led to decreased bioavailability, uptake, and bioaccessibility of HMs in soil, which could improve food safety and reduce potential risks associated with HM contamination.
Asunto(s)
Disponibilidad Biológica , Lactuca , Metales Pesados , Fósforo , Contaminantes del Suelo , Suelo , Contaminantes del Suelo/metabolismo , Lactuca/metabolismo , Lactuca/crecimiento & desarrollo , Suelo/química , Fertilizantes , Cadmio/metabolismo , Níquel , Compostaje/métodosRESUMEN
(1) Background: Trace metal (TM) contamination of farmland soil in Taiwan occurs because factories dump wastewater into irrigation ditches. Since vermicompost affects the bioavailability of TMs, the objective of this study was to evaluate its effects on the accumulation of growth of TMs in leafy vegetables. (2) Methods: Two TM-contaminated soils and different types of pak choi and lettuce were used and amended with vermicompost. Besides soil properties, the study assessed vermicompost's influence on the growth, accumulation, and chemical forms of TMs and on the health risks posed by oral intake. (3) Results: Vermicompost could increase the content of soil organic matter, available phosphorus, exchangeable magnesium, and exchangeable potassium, thus promoting the growth of leafy vegetables. The accumulation of four TMs in crops under vermicompost was reduced compared to the control, especially for the concentration of cadmium, which decreased by 60-75%. The vermicompost's influence on changing the chemical form of TMs depended on the TM concentrations, type of TM, and crop species; moreover, blanching effectively reduced the concentrations of TMs in high-mobility chemical forms. Although vermicompost mostly reduced the amount of cadmium consumed via oral intake, cadmium still posed the highest health risk compared to the other three TMs.
Asunto(s)
Metales Pesados , Contaminantes del Suelo , Cadmio/análisis , Metales Pesados/análisis , Suelo , Contaminantes del Suelo/análisis , Taiwán , VerdurasRESUMEN
(1) Background: Even in croplands with a low concentration of cadmium (Cd), there is still a risk for planting crops because of the high accumulation capacity of some leafy vegetables. (2) Methods: In this study, water spinach was planted in four main soil series (Wa, Eh, Tk, and Yu) in central Taiwan, which were spiked with Cd. The soil available phosphorous content was increased to 10-17 mg/kg, and the accumulation and developed chemical forms of Cd were analyzed. (3) Results: The experimental results showed that addition of phosphorous to Wa and Eh promoted the growth of water spinach. Accumulation and upward translocation of Cd were also increased in the phosphorus treatment compared with the control. The addition of phosphorus increased the percentage of Cd compartmentalized in undissolved Cd phosphate, which revealed that the mobility and toxicity of Cd were reduced in the phosphorus treatment. However, most of the water spinach was not edible because the vegetable-induced hazard quotient, which was calculated using three methods, showed hazardous potential in general.
Asunto(s)
Cadmio/metabolismo , Fertilizantes/análisis , Contaminación de Alimentos/análisis , Ipomoea/química , Fósforo/administración & dosificación , Contaminantes del Suelo/metabolismo , Transporte Biológico , Ipomoea/metabolismo , Medición de Riesgo , Suelo/química , TaiwánRESUMEN
A plant's tolerance to heavy metals (HMs) and its detoxification mechanisms are associated with the subcellular distribution of HMs and their chemical forms. In this study, water spinach (Ipomoea aquatica Forsk.) was grown in two soils contaminated with a single HM (cadmium, Cd) or combined HMs (Cd and nickel, Ni). Inoculation of arbuscular mycorrizal fungi (AMF) was conducted to increase the accumulation of phosphorus (P) in plants. One major exception was to decrease the migration and accumulation of HMs in edible parts by the formation of P-HM complexes. The effects of blanching and simulated digestion on bioaccessibility were also assessed. The experimental results showed that the water spinach species used in this study had a high capacity to accumulate HMs. AMF treatment improved water spinach growth and decreased the accumulation of Ni but not that of Cd. Soluble and inorganic Cd and Ni were the major subcellular fractions and chemical forms in water spinach; these two HMs also exhibited higher migration capacities in comparison to chromium (Cr). Relative to raw tissues, 45-84% of Cd, Cr, and Ni were leached after blanching. Approximately 32-55%, 16-50%, and 27-40% of Cd, Cr, and Ni, respectively, were bioaccessible and could be metabolized by in vitro digestive fluids.
Asunto(s)
Ipomoea/química , Ipomoea/microbiología , Metales Pesados/análisis , Micorrizas , Disponibilidad Biológica , Concentración de Iones de Hidrógeno , Fósforo/análisis , Suelo/química , Contaminantes del Suelo/análisisRESUMEN
Impatiens walleriana (I. walleriana), a potential cadmium (Cd) hyperaccumulator, can propagate by cuttings, which are less expensive to grow than seedlings. Different growth periods for cuttings, however, may lead to different physiological characteristics. In this study, I. walleriana cuttings were hydroponically grown in Cd-containing solutions (1.0-10.0 µM) for various growth periods (10-60 days). Experimental results showed that the Cd treatments had negative effects on growth compared to the controls that were not spiked with Cd. The extension of the growth period promoted most of the growth exhibitions of I. walleriana, except for SPAD readings for cuttings grown in the 5.0 and 10.0 µM solutions. The accumulation of Cd also increased over time, except in the roots of the cuttings grown in the 5.0 and 10.0 µM solutions. The subcellular distribution and chemical forms of Cd showed that I. walleriana developed better tolerance and detoxification capacities in the cuttings grown in the 5.0 and 10.0 µM solutions than in the cuttings grown in the other two Cd treatments.
Asunto(s)
Cadmio/metabolismo , Cadmio/toxicidad , Impatiens/crecimiento & desarrollo , Impatiens/metabolismo , Relación Dosis-Respuesta a Droga , Hidroponía , Impatiens/efectos de los fármacos , Raíces de Plantas/efectos de los fármacos , Raíces de Plantas/crecimiento & desarrollo , Raíces de Plantas/metabolismo , Contaminantes del Suelo/metabolismo , Contaminantes del Suelo/toxicidad , Factores de TiempoRESUMEN
Impatiens walleriana plants accumulate sufficiently high concentrations of cadmium (Cd) for this species to be considered a potential Cd hyperaccumulator. Rooted cuttings were grown hydroponically for 25 and 50 days in solutions spiked with various Cd concentrations. The subcellular distribution and chemical forms of Cd in different organs were analyzed, and its upward translocation was also assessed. The plants accumulated large amounts of Cd; the Cd concentration in the roots and shoots reached 120-1900 and 60-1600 mg/kg, respectively. Regardless of the growth period, the Cd accumulated in the roots was primarily compartmentalized in the soluble fraction or ethanol and deionized water extractable chemical forms with high migration abilities. Translocation to the shoots was followed by an association of Cd mainly in the cell wall or with pectate and protein. The roots' Cd showed a high migration capacity for predicting the shoots' Cd concentrations. Different exposure periods significantly affected the subcellular distribution of Cd in the stems, and thus the upward translocation.
Asunto(s)
Cadmio/metabolismo , Impatiens/crecimiento & desarrollo , Impatiens/metabolismo , Contaminantes del Suelo/metabolismo , Biodegradación Ambiental , Cadmio/química , Impatiens/química , Modelos Biológicos , Estructura Molecular , Hojas de la Planta/química , Hojas de la Planta/metabolismo , Raíces de Plantas/química , Raíces de Plantas/metabolismo , Contaminantes del Suelo/químicaRESUMEN
Impatiens (Impatiens walleriana) has been shown to be a potential cadmium (Cd) hyperaccumulator, but its mechanisms in accumulation and detoxification have not been reported. Rooted cuttings of Impatiens were planted in artificially Cd-contaminated soils for 50 days with total target concentrations of 0, 10, 20, 40, 80, and 120 mg/kg. The subcellular distribution and chemical forms of Cd in the different organs were analyzed after the pot experiment. Compared with the control group, various Cd treatments affected the growth exhibitions of Impatiens, but most of them were not statistically significant. The Cd accumulation of different organs increased with an increase in the soil Cd concentrations for most of the treatments, and it was in the decreasing order of root>stem>leaf. In the roots of Impatiens, Cd was mainly compartmentalized in the soluble fraction (Fs), which has a high migration capacity and will further translocate to the shoot. The Cd was mainly compartmentalized in the cell wall fraction (Fcw) in the shoots as a mechanism of tolerance. Most of the Cd in the various organs of Impatiens was mainly in the forms of pectate and protein-integrated (FNaCl), whereas a minor portion was a water soluble fraction (FW). The experimental results show that the Cd in the Fs, FW, and FNaCl in the roots of Impatiens had a high mobility and will further translocate to the shoot. They could be used to estimate the Cd accumulated in the shoots of Impatiens.
Asunto(s)
Cadmio/química , Cadmio/metabolismo , Impatiens/citología , Espacio Intracelular/metabolismo , Contaminantes del Suelo/química , Contaminantes del Suelo/metabolismo , Biodegradación Ambiental , Cadmio/aislamiento & purificación , Impatiens/metabolismo , Hojas de la Planta/metabolismo , Raíces de Plantas/metabolismo , Tallos de la Planta/metabolismo , Suelo/química , Contaminantes del Suelo/aislamiento & purificaciónRESUMEN
Due to the low phytoavailability of some heavy metals (HMs), a prolonged period is required when phytoextraction is used to remove these HMs from contaminated soils. The use of chelants and other chemical compounds are often used to increase the phytoavailability of the HMs for plant uptake. Negative effects of chemical agents on the soil and groundwater have rarely been reported during chemical-enhanced phytoextraction. This research applied chelants to various soil series with different characteristics to assess their impacts on soil quality. The experimental results showed that the application of 5 mmol kg(-1) of all chelants had a negative effect on the soil quality. This was especially true for electrical conductivity (EC) when diethylene trinitrilo pentaacetic acid (DTPA) was used as the chemical extracting agent.
Asunto(s)
Quelantes/análisis , Suelo/química , Quelantes/efectos adversos , Concentración de Iones de HidrógenoRESUMEN
Nitrogen is an essential element for plant growth and development; however, due to environmental pollution, high nitrate concentrations accumulate in the edible parts of these leafy vegetables, particularly if excessive nitrogen fertilizer has been applied. Consuming these crops can harm human health; thus, developing a suitable strategy for the agricultural application of nitrogen fertilizer is important. Organic, inorganic, and liquid fertilizers were utilized in this study to investigate their effect on nitrate concentrations and lettuce growth. The results of this pot experiment show that the total nitrogen concentration in soil and the nitrate concentration in lettuce increased as the amount of nitrogen fertilizer increased. If the recommended amount of inorganic fertilizer (200 kg·N·ha⻹) is used as a standard of comparison, lettuce augmented with organic fertilizers (200 kg·N·ha⻹) have significantly longer and wider leaves, higher shoot, and lower concentrations of nitrate.
Asunto(s)
Agricultura/métodos , Fertilizantes , Lactuca/efectos de los fármacos , Nitratos/metabolismo , Nitrógeno/farmacología , Conductividad Eléctrica , Concentración de Iones de Hidrógeno , Lactuca/crecimiento & desarrollo , Lactuca/metabolismo , Hojas de la Planta/efectos de los fármacos , Hojas de la Planta/crecimiento & desarrollo , Hojas de la Planta/metabolismo , Brotes de la Planta/efectos de los fármacos , Brotes de la Planta/crecimiento & desarrollo , Brotes de la Planta/metabolismo , Suelo/químicaRESUMEN
Arsenic contamination in a large area of agricultural fields on the Guandu Plain of northern Taiwan was confirmed in a survey conducted in 2006, but research concerning the relationship between bioavailable As concentrations in contaminated soils and crop production in Taiwan is not available. Pot experiments were conducted to examine the growth and accumulation of As in four vegetable crops grown in As-contaminated soils and to assess As intake through consumption. The phytotoxic effects of As in soils were not shown in the pot experiments in which vegetable crops were grown in soils contaminated with different As levels in situ collected from Guandu Plain (120-460 mg/kg) or artificially spiked As-contaminated soils (50-170 mg/kg). Experimental results showed that the bioavailable As extracted with 0.5M NaHCO3 from soils can be used to estimate As concentrations in vegetables. The As concentrations in the vegetables were compared with data shown in the literature and As limits calculated from drinking water standards and the provisional tolerance weekly intake (PTWI) of inorganic As established by the Food and Agriculture Organization of the United Nations/World Health Organization (FAO/WHO). Although the As levels in the vegetables were not high and the bioavailability of As in the soils was quite low, long-term consumption may result in higher As intake in the human body.
Asunto(s)
Arsénico , Contaminación de Alimentos/análisis , Contaminantes del Suelo , Verduras , Arsénico/análisis , Arsénico/farmacología , Arsénico/toxicidad , Disponibilidad Biológica , Monitoreo del Ambiente , Inocuidad de los Alimentos , Humanos , Medición de Riesgo , Contaminantes del Suelo/análisis , Contaminantes del Suelo/farmacología , Contaminantes del Suelo/toxicidad , Taiwán , Verduras/efectos de los fármacos , Verduras/crecimiento & desarrollo , Verduras/metabolismoRESUMEN
The phytotoxic effects of excess copper (Cu) on grapevines (Vitis vinifera L. var. Kyoho) were examined, both from macroscopic and microscopic perspectives, by using a fifteen-day hydroponic experiments. The influence of magnesium (Mg) on Cu phytotoxicity to, and accumulation and translocation in grapevines was also observed. For phytotoxicity effect, results showed that a relative low median growth inhibition level of Cu was found for grapevine roots (0.809-3.671µM). Moreover, Cu toxicity was significantly alleviated by Mg treatment at Mg(2+) activity between 0.15 and 2.01mM. For accumulation and translocation effects, results indicated that competition for binding sites between Cu and Mg occurred for roots; however, Mg and Cu levels in stems and leaves were not affected by solution metals concentration. At Cu concentration less than 1µM, the translocation of Cu was decreased significantly for the highest Mg treatment; at Cu concentrations greater than 5µM, no obvious change was observed in leaf TF value between Mg treatments, while an increasing trend of stem TF value was observed with increasing Mg. These results suggest that the toxic effect resulted from metals depend not only on the competition of coexistent cations for plasma membrane surface, but also on the transport and distribution of toxic metals in physiological active sites in plants.
Asunto(s)
Cobre/metabolismo , Cobre/toxicidad , Magnesio/farmacología , Vitis/efectos de los fármacos , Vitis/metabolismo , Cationes/farmacología , Cobre/análisis , Hidroponía , Hojas de la Planta/efectos de los fármacos , Hojas de la Planta/metabolismo , Raíces de Plantas/efectos de los fármacos , Raíces de Plantas/metabolismo , Tallos de la Planta/efectos de los fármacos , Tallos de la Planta/metabolismo , Vitis/crecimiento & desarrollo , Contaminantes Químicos del Agua/toxicidadRESUMEN
The accumulation of heavy metals, especially cadmium (Cd), in leafy vegetables was compared with other vegetables. Pak choi (Brassica campestris L. ssp. chinensis) is a leafy vegetable consumed in Taiwan and its safety for consumption after growing in contaminated soils is a public concern. A pot experiment (50 days) was conducted to understand the dynamic accumulation of Cd by pak choi grown in artificially contaminated soils. The edible parts of pak choi were sampled and analyzed every 2-3 days. The dry weight (DW) of pak choi was an exponential function of leaf length, leaf width, and chlorophyll content. The accumulation of Cd increased when the soil Cd concentration was raised, but was kept at a constant level during different growth stages. Pak choi had a high bioconcentration factor (BCF = ratio of the concentration in the edible parts to that in the soils), at values of 3.5-4.0. The consumption of pak choi grown in soils contaminated at levels used in this study would result in the ingestion of impermissible amounts of Cd and could possibly have harmful effects on health.
Asunto(s)
Brassica/crecimiento & desarrollo , Brassica/metabolismo , Cadmio/metabolismo , Contaminación de Alimentos/análisis , Contaminantes del Suelo/metabolismo , Espectrofotometría Atómica , Taiwán , Verduras/crecimiento & desarrollo , Verduras/metabolismoRESUMEN
French marigold (Tagetes patula) and impatiens (Impatiens walleriana) can act as hyperaccumulator plants for removal of cadmium (Cd) from contaminated sites. In this study, an exponential decay model was used to predict the maximum removal of Cd from artificially spiked soils by impatiens. Application of a chelator, EDTA, was also assessed for effects on the bioconcentration (BCF) and translocation (TF) factors of the two species with four replicates. Exposure to Cd significantly decreased the biomass of two plant species. Impatiens and French marigold accumulated Cd at a rate of 200-1200 mg Cd kg(-1) in shoots, with BCFs and TFs of 8.5-15 and 1.7-2.6, respectively.
Asunto(s)
Cadmio/metabolismo , Quelantes/farmacología , Ácido Edético/farmacología , Impatiens/efectos de los fármacos , Contaminantes del Suelo/metabolismo , Tagetes/efectos de los fármacos , Biodegradación Ambiental , BiomasaRESUMEN
To better understand the ability of switchgrass (Panicum virgatum L.), a perennial grass often relegated to marginal agricultural areas with minimal inputs, to remove cadmium, chromium, and zinc by phytoextraction from contaminated sites, the relationship between plant metal content and biomass yield is expressed in different models to predict the amount of metals switchgrass can extract. These models are reliable in assessing the use of switchgrass for phytoremediation of heavy-metal-contaminated sites. In the present study, linear and exponential decay models are more suitable for presenting the relationship between plant cadmium and dry weight. The maximum extractions of cadmium using switchgrass, as predicted by the linear and exponential decay models, approached 40 and 34 µg pot(-1), respectively. The log normal model was superior in predicting the relationship between plant chromium and dry weight. The predicted maximum extraction of chromium by switchgrass was about 56 µg pot(-1). In addition, the exponential decay and log normal models were better than the linear model in predicting the relationship between plant zinc and dry weight. The maximum extractions of zinc by switchgrass, as predicted by the exponential decay and log normal models, were about 358 and 254 µg pot(-1), respectively. To meet the maximum removal of Cd, Cr, and Zn, one can adopt the optimal timing of harvest as plant Cd, Cr, and Zn approach 450 and 526 mg kg(-1), 266 mg kg(-1), and 3022 and 5000 mg kg(-1), respectively. Due to the well-known agronomic characteristics of cultivation and the high biomass production of switchgrass, it is practicable to use switchgrass for the phytoextraction of heavy metals in situ.
Asunto(s)
Metales Pesados/análisis , Panicum/química , Contaminantes del Suelo/análisis , Agricultura , Biodegradación Ambiental , Biomasa , Cadmio/análisis , Cromo/análisis , Modelos Biológicos , Zinc/análisisRESUMEN
PURPOSE: Although the ecotoxicological effects of copper (Cu) on grapevine are of global concern due to the intensive and long-term application of Cu-based fungicides in vineyards, comparatively little is known about the phytotoxicity, accumulation, and translocation of Cu in grapevines. Therefore, this study was to conduct a hydroponic experiment to determine the influence of solution Cu concentration not only on bioaccumulation and the translocation of Cu in grapevine roots, stems, and leaves, but also on the subsequent growth inhibition of the roots. METHODS: Grapevine cuttings were grown for 30 days and then exposed to various Cu concentrations (0.1-50 µM) for 15 days. The dose-response profile was described by a sigmoid Hill equation. Optical microscopy was used to examine the cytotoxicity of Cu on the roots. In addition, bioaccumulation factors (BAFs) and translocation factors (TFs) were calculated from the results of the hydroponic experiment. RESULTS: Copper was tolerated by grapevines at a concentration ≤1 µM. The median inhibition concentration (IC(50)) obtained from the Hill model was 3.94 µM (95% confidence interval, 3.65-4.24). From the light micrographs of root tip cells, signs of toxicity including increased vacuolization and plasmolysis were observed at solution Cu concentrations ≥10 µM. In addition, a higher Cu concentration was found in the roots (25-12,000 mg kg(-1)) than in the stems (5-540 mg kg(-1)) and leaves (7-46 mg kg(-1)), indicating a very limited translocation of Cu from the roots to the aboveground parts. CONCLUSIONS: This study investigated not only the macroscopic root growth and Cu accumulation by grapevine, but also the microscopic changes in root tissue at the cell level after the exposure experiment. Based on the BAFs and TFs, the grapevine could be considered a Cu-exclusive plant. For toxic effects on the exposure of roots to Cu, this study also revealed that root growth, as well as the histological changes in rhizodermal cells, can be used as phytotoxic indicators of grapevine under Cu stress.
Asunto(s)
Cobre/farmacocinética , Cobre/toxicidad , Vitis/efectos de los fármacos , Relación Dosis-Respuesta a Droga , Raíces de Plantas/efectos de los fármacos , Raíces de Plantas/crecimiento & desarrollo , Raíces de Plantas/metabolismo , Tallos de la Planta/efectos de los fármacos , Tallos de la Planta/crecimiento & desarrollo , Tallos de la Planta/metabolismo , Espectrofotometría Atómica , Vitis/crecimiento & desarrollo , Vitis/metabolismoRESUMEN
Solid phase microextraction (SPME) coupled with gas chromatography was employed to estimate bioavailability of pyrene in soils with different properties of textures, organic matter contents (SOM) and aging periods. Experimental results indicated that biodegradation rates increased from 0.10 (sandy loam) to 0.15 (silty loam) microg g-1 hr1. By contrast, biodegradation rate decreased from 0.10(1.3% SOM) to 0.04 (7.6% SOM) microg g-1hr1. The amounts of pyrene biodegraded decreased 27% when SOM was modified from 1.3 to 7.6%, indicating that distributions of pyrene in soils at biodegradation end points were affected by the SOM. Sequestration as measured by sonication extraction had evidently occurred in aged soil samples. SPME measurements slightly overestimated the amount of pyrene degraded by indigenous and seeded microorganisms, in soils with the different properties (correlation coefficient, R2= 0.74). The present study demonstrates that the SPME method can not replace biodegradation tests commonly used for predicting bioremediation efficacy.
Asunto(s)
Biodegradación Ambiental , Pirenos/química , Contaminantes del Suelo/química , Suelo/química , Microextracción en Fase Sólida , Monitoreo del Ambiente , Factores de TiempoRESUMEN
A major challenge in phytoextraction is to increase plants' removal rates of metals from contaminated soils. In this study, we developed a phytoextraction model, by coupling a saturable Michaelis-Menten type accumulation model and an energy-based toxicity model, to predict copper (Cu) removal by switchgrass (Panicum virgatum L.) grown hydroponically under various exposure concentrations. Results of the present study indicated that the phytotoxicity of Cu to switchgrass is relatively low, whereas a certain accumulation capacity exists in the plant for Cu. In addition, the simulation results suggested that, under a lower dissolved concentration, Cu removal is increased more efficiently as the exposure duration increases. Although it is difficult to extrapolate the results from greenhouse-based hydroponic experiments to field conditions, we believe that the current methodology can offer a first approximation in predicting the phytoextraction duration needed for plant species to remove a specific metal from contaminated sites, which is crucial in evaluating the economic costs for remediation purposes.
Asunto(s)
Cobre/metabolismo , Panicum/metabolismo , Contaminantes Químicos del Agua/metabolismo , Biodegradación Ambiental , Cobre/análisis , Cobre/toxicidad , Relación Dosis-Respuesta a Droga , Hidroponía , Panicum/efectos de los fármacos , Panicum/crecimiento & desarrollo , Contaminantes Químicos del Agua/análisis , Contaminantes Químicos del Agua/toxicidadRESUMEN
The purpose of this study is to evaluate the phytoextraction of cadmium (Cd) from contaminated soils by switchgrass (Panicum virgatum L.), which is a promising energy crop with high biomass. Two ecotypes of switchgrass cultivars, Alamo and Blackwell, were investigated in a pot experiment. Dry weight and plant Cd concentration of the switchgrass plants growing on Cd-spiked soils (0, 20, and 60 mg Cd kg(-1) soil) with chelating agent amendments (1 g kg(-1) citric acid [CA] and 0.1 g kg(-1) ethylene diaminetetraacetic acid [EDTA]) were measured to examine the phytotoxicity and accumulation of Cd in the switchgrass. Fractions of Cd (F1, exchangeable; F2, carbonate; F3, Fe-Mn oxide; F4, organic matter; F5, residual) for the soils sampled at the time of harvesting were also determined using chemically sequential extractions. In the results, the dry weight of the switchgrass decreased with increasing Cd, with a significant dry weight reduction when Cd exceeded 20 mg kg(-1). However, the high Cd spike of 60 mg kg(-1) was not lethal to Alamo and Blackwell, which suggests that switchgrass plants can tolerate Cd and grow in contaminated soils. Compared with the control, the CA and EDTA amendments had no adverse effect on the growth of switchgrass plants. With regard to Cd accumulation, higher plant Cd concentrations were frequently found after CA amendment in Alamo; however, the Cd concentrations of Blackwell plants may increase when amended with EDTA. On the basis of the fractionation of soil Cd, dry weight and plant Cd concentration could be expressed as a function of Cd fractionation to predict the phytoextraction of Cd. Thus, the fractionation of Cd is a useful approach for evaluating the phytoextraction of Cd by switchgrass in contaminated soils. According to the comparison of phytoextractions of Cd between Alamo and Blackwell, Alamo plants removed substantially more Cd from Cd-spiked soils than Blackwell. Therefore, Alamo is better suited for the phytoextraction of Cd from contaminated soils.
Asunto(s)
Cadmio/análisis , Fraccionamiento Químico , Panicum/química , Contaminantes del Suelo/análisis , Biodegradación AmbientalRESUMEN
Many studies have been conducted on phytoextraction; however, non-native hyperaccumulator species are not suitable for the natural environment of Taiwan in many cases. Drawing upon previous results, the growth and heavy metal accumulation in artificially cadmium-contaminated soils were compared for five local garden flower species. The treatments included a control (CK), 9.73 +/- 0.05 mg kg(-1) (Cd-10), and 17.6 +/- 0.8 mg kg(-1) (Cd-20). All plants were harvested at 35 days after transplanting and analyzed for Cd content. Cd accumulation in the shoot of French marigold (Tagetes patula L.) and Impatiens (Impatiens walleriana Hook. f.) grown in Cd-20 treatment were 66.3 +/- 6.5 and 100 +/- 11 mg kg(-1), which equated to a removal of 0.80 +/- 0.11 and 0.60 +/- 0.37 mg Cd plant(-1), respectively. The maximum Cd accumulation of Impatiens reached the threshold value (100 mg kg(-1)) characteristic of a Cd hyperaccumulator and its bioconcentration factor (BCF) and translocation factor (TF) were greater than one. Impatiens therefore has the potential to hyperaccumulate Cd from Cd-contaminated soils. With the exception of Garden verbena, significant relationships were found between Cd concentrations in soil extracted by 0.05 M EDTA, 0.005 M DTPA, and 0.01 M CaCl2 and the concentration of Cd in the shoots of the tested garden flowers.
Asunto(s)
Cadmio/metabolismo , Flores/metabolismo , Disponibilidad Biológica , Contaminación Ambiental , Impatiens/metabolismo , Metales Pesados/metabolismo , Raíces de Plantas/metabolismo , Brotes de la Planta/metabolismo , Salvia/metabolismo , Salvia officinalis/metabolismo , Plantones/metabolismo , Contaminantes del Suelo/metabolismoRESUMEN
A site in central Taiwan with an area of 1.3 ha and contaminated with Cr, Cu, Ni, and Zn was selected to examine the feasibility of phytoextraction. Based on the results of a preexperiment at this site, a total of approximately 20,000 plants of 12 species were selected from plants of 33 tested species to be used in a large-area phytoextraction experiment at this site. A comparison with the initial metal concentration of 12 plant species before planting demonstrated that most species accumulated significant amounts of Cr, Cu, Ni, and Zn in their shoots after growing in this contaminated site for 31 d. Among the 12 plant species, the following accumulated higher concentrations of metals in their shoots; Garden canna and Garden verbena (45-60 mg Cr kg(-1)), Chinese ixora and Kalanchoe (30 mg Cu kg(-1)), Rainbow pink and Sunflower (30 mg Ni kg(-1)), French marigold and Sunflower (300-470 mg Zn kg(-1)). The roots of the plants of most of the 12 plant species can accumulate higher concentrations of metals than the shoots and extending the growth period promotes accumulation in the shoots. Large-area experiments demonstrated that phytoextraction is a feasible method to enable metal-contaminated soil in central Taiwan to be reused.