Shoot Bioconcentration Factors Research Articles

Evaluating phytoremediation potential and nutrients status of Bassia indica (Wight) A. J. Scott (Indian Bassia) in a cadmium-contaminated saline soil.

Bassia indica (Wight) A. J. Scott is a fast-growing halophyte suitable for the remediation of saline lands on a large scale. However, no information is available regarding its phytoremediation potential for cadmium (Cd) alone or in combination with salinity. Besides evaluating phytoremediation, assessing micronutrient hemostasis as a crucial physiological insight into the mechanism involved in the tolerance of B. indica under saline soil contaminated with Cd was subjected. Under salinity stress, a considerable amount of sodium accumulates in the plant. Moreover, the accumulation of sodium increased by Cd stress levels. The increase in the exchangeable form of Cd in the rhizosphere in the presence of NaCl ions further elevated the Cd content in the plant tissues. For instance, compared to non-saline conditions, applying 2.5 and 5 g NaCl kg-1 to soil treated with 60 mg Cd kg-1 increased exchangeable Cd by 28.4 and 49.5% in rhizosphere soil, which led to increased cadmium content by 16.1 and 29.6% in the root (as amainpart of Cd accumulation), respectively. Under most stress conditions, potassium homeostasis in the shoot remained undisturbed. It was observed that this plant could transfer an optimal level of potassium from the roots to the shoots at a moderate salinity level. Changes and the distribution of Cu and Zn levels followed a similar pattern in the plant, indicating a common regulation mechanism for these nutrients. Generally, the plant could maintain an appropriate level of Fe, Zn, and Cu ions under most stressed conditions. However, the level of Mn decreased significantly under severe stress levels. Growth parameters, tolerance index, and the values of translocation factor < 1 and shoot bioconcentration factor > 1 under 5 mg Cd kg-1 soil treatment at different salinity levels indicated that B. indica could mitigate the detrimental effect of Cd toxicity and tolerate the NaCl stress via a phytostabilizer mechanism. However, the shoot bioconcentration factor values were very close to one at other Cd levels. Therefore, considering the obtained evidence and the innate ability of B. indica to remediation salinity, this plant is still recommended, even for higher Cd levels (even until 30 mg kg-1), in the presence of salinity.

Rhizospheric Lactobacillus spp. contribute to the high Cd-accumulating characteristics of Phytolacca spp. in acidic Cd-contaminated soil

Screening high Cd-accumulating plants and understanding the interactions between plants, rhizospheric microbes and Cd are important in developing microbe-assisted phytoremediation techniques for Cd-contaminated soils. In this study, the Cd tolerance and accumulation characteristics of Phytolacca americana L., P. icosandra L. and P. polyandra Batalin growing in acidic Cd-contaminated soil were compared to evaluate their phytoremediation potential. According to Cd concentrations (root: 8.26–37.09 mg kg−1, shoot: 2.80–9.26 mg kg−1), bioconcentration factors (BCFs) and translocation factors (TFs), the three Phytolacca species exhibited high Cd-accumulation capacities, ranked in the following order: P. icosandra (root BCF: 1.25, shoot BCF: 0.31, TF: 0.25) > P. polyandra (root BCF: 0.68, shoot BCF: 0.26, TF: 0.44) > P. americana (root BCF: 0.28, shoot BCF: 0.09, TF: 0.38). Phytolacca icosandra and P. polyandra can thus be considered as two new Cd accumulators for phytoremediation. Soil pH, available Cd (ACd) concentration and certain bacterial taxa (e.g. Lactobacillus, Helicobacter, Alistipes, Desulfovibrio and Mucispirillum) were differentially altered in the rhizospheres of the three Phytolacca species in comparison to unplanted soil. Correlation analysis showed that there were significant interactions between rhizospheric ACd concentration, pH and Lactobacillus bacteria (L. murinus, L. gasseri and L. reuteri), which affected Cd uptake by Phytolacca plants. The mono- and co-inoculation of L. murinus strain D51883, L. gasseri strain D51533 and L. reuteri strain D24591 in the rhizosphere of P. icosandra altered the rhizospheric pH and ACd concentrations, in addition to increasing the shoot Cd contents by 31.9%–44.6%. These results suggest that recruitment of rhizospheric Lactobacillus spp. by Phytolacca plants contributes to their high Cd-accumulating characteristics. This study provides novel insights into understanding the interactions between plants, rhizobacteria and heavy metals.

Phytoremediation and Bioconcentration of Mineral and Heavy metals in Zea mays Inter-planted with Striga hermonthica in Soils from Mechanic Village Wukari

Phytoremediation involves the use of plants to remediate contaminated sites. This study evaluates the effect of phytoremediation on mineral and heavy metal concentration in agricultural soil within the vicinity of mechanic village Wukari using Zea mays interplanted with Striga hermonthica (SMV-MS), Zea mays alone (SMV-M), Zea mays inter-planted with Striga hermonthica alongside the application of fertilizer (SMV-MSF) and Zea mays alone alongside fertilizer application (SMV-MF). The bioconcentration of mineral and heavy metal and their translocation factors from the root to shoot of maize plants were estimated using empirical models. The result reveals that the efficiency of phytoextraction of the mineral and heavy metals were within the range: P (3.12 – 44.71 %), K (16.89 – 96.32 %), Mg (0.013 – 94.12 %), Mn (2.31 – 99.98 %), Si (20.92 – 52.07 %), Zn (2.74 – 21.65 %), Pb (10.44 – 100 %), Cd (0.75 – 42.85 %), Fe (7.42 – 98.57 %) and Al (19.14 – 98.69 %) respectively. The mean root and shoot bioconcentration factors (BCFs) of K, Mg, Mn and Al were greater than one indicating higher accumulation of the elements in the root and shoot of the maize plants. The root BCF of the elements was generally in the order: Mn &gt; K &gt; Mg &gt; Cd &gt; S i &gt; Al &gt; P &gt; Fe &gt; Zn &gt; Pb while the shoot BCF was in the order: Mn &gt; K &gt; Mg &gt; Al &gt; Fe &gt; Cd &gt; S i &gt; P &gt; Zn &gt; Pb. The mean root to shoot translocation factors (TF) of P, Mn, Zn, Pb, Cd, Fe and Al were greater than one indicating effective translocation of the elements from the root to shoots. The translocation factors were generally in the order: Fe &gt; Al &gt; Pb &gt; Mn &gt; Zn &gt; P &gt; Cd &gt; Mg &gt; S i &gt; K.

Intercropping affects the physiology and cadmium absorption of pakchoi, lettuce, and radish seedlings.

Intercropping can affect the growth and elemental absorption of vegetables. This study investigated the physiology and cadmium (Cd) content of pakchoi (Brassica chinensis L.), lettuce (Lactuca sativa L. var. ramosa Hort.), and radish (Raphanus sativus L.) seedlings under monoculture, mutual intercropping of two or three varieties. Intercropping is not conducive to the accumulation of chlorophyll and biomass content of pakchoi, lettuce, and radish. When three seedlings were intercropped together, the antioxidant enzyme activity of pakchoi, lettuce, and radish increased and the content of malondialdehyde decreased, except that the superoxide dismutase activity of radish is inferior to the value of radish and pakchoi intercropping. Intercropping increased the soluble sugar and proline content in the lettuce seedlings, while those in the radish and lettuce seedlings reduced or had no significant effect. When intercropped with pakchoi and lettuce, the Cd content in the roots and shoots of pakchoi is higher and lower, respectively. At the same time, root or shoot bio-concentration factors also performed the same trend, and TF was the smallest and less than 1; however, the TF of lettuce is greater than 1. When intercropping with pakchoi or lettuce separately or together, it promoted the accumulation of Cd in radish root; when intercropping with pakchoi, the value of TF was the smallest. From the antioxidant system, the performance of the three seedlings intercropped together is better than the two; however, the accumulation of Cd shows the opposite trend, and the participation of cabbage in the intercropping is relatively conducive to reducing the Cd content in the edible parts.

Physiological and rhizospheric response characteristics to cadmium of a newly identified cadmium accumulator Coreopsis grandiflora Hogg. (Asteraceae)

Screening for superior cadmium (Cd) phytoremediation resources and uncovering the mechanisms of plant response to Cd are important for effective phytoremediation of Cd-polluted soils. In this study, the characteristics of Coreopsis grandiflora related to Cd tolerance and accumulation were analyzed to evaluate its Cd phytoremediation potential. The results revealed that C. grandiflora can tolerate up to 20 mg kg−1 of Cd in the soil. This species showed relatively high shoot bioconcentration factors (1.09–1.85) and translocation factors (0.46–0.97) when grown in soils spiked with 5–45 mg kg–1 Cd, suggesting that C. grandiflora is a Cd accumulator and can potentially be used for Cd phytoextraction. Physiological analysis indicated that antioxidant enzymes (i.e., superoxide dismutase, peroxidase, and catalase) and various free amino acids (e.g., proline, histidine, and methionine) participate in Cd detoxification in C. grandiflora grown in soil spiked with 20 mg kg–1 of Cd (Cd20). The overall microbial richness and diversity remained similar between the control (Cd0) and Cd20 soils. However, the abundance of multiple rhizospheric microbial taxa was altered in the Cd20 soil compared with that in the Cd0 soil. Interestingly, many plant growth-promoting microorganisms (e.g., Nocardioides, Flavisolibacter, Rhizobium, Achromobacter, and Penicillium) enriched in the Cd20 soil likely contributed to the growth and vitality of C. grandiflora under Cd stress. Among these, some microorganisms (e.g., Rhizobium, Achromobacter, and Penicillium) likely affected Cd uptake by C. grandiflora. These abundant plant growth-promoting microorganisms potentially interacted with soil pH and the concentrations of Cd and AK in soil. Notably, potassium-solubilizing microbes (e.g., Rhizobium and Penicillium) may effectively solubilize potassium to assist Cd uptake by C. grandiflora. This study provides a new plant resource for Cd phytoextraction and improves our understanding of rhizosphere-associated mechanisms of plant adaptation to Cd-contaminated soil.

Cadmium uptake by a hyperaccumulator and three Pennisetum grasses with associated rhizosphere effects.

Pennisetum grasses (P. purpureum Schumach. 'Purple', P. alopecuroides (L.) Spreng. 'Liren' and P. alopecuroides (L.) Spreng. 'Changsui'), and a cadmium (Cd) hyperaccumulator (Thlaspi caerulescens J.Presl & C.Presl), were grown in soil with four Cd addition levels of 0, 2, 20 and 200 mg/kg. Toxicity symptoms were not observed although growth of all plants decreased as Cd addition increased. Shoot bioconcentration factor (BCFS), the translocation factor (TF) and shoot accumulation of Cd for most plants first increased and then declined as Cd concentrations increased. In contrast, the root bioconcentration factor (BCFR) for T. caerulescens declined and root Cd accumulation for T. caerulescens and two P. alopecuroides cultivars increased consistently as Cd levels increased. P. purpureum had the largest biomass with shoot Cd accumulation similar to that of T. caerulescens, despite lower foliar Cd concentration. Although shoot Cd concentrations of two P. alopecuroides cultivars were lower than for P. purpureum, root Cd concentrations were greater. P. purpureum had Cd BCFS and TF (> 1) at 2- and 20-mg/kg Cd addition treatments, similar to T. caerulescens. P. alopecuroides cultivars had Cd BCFR (> 1) and TF (< 1) at all Cd levels. Roots did not affect rhizosphere pH. However, concentrations of acid extractable Cd in rhizosphere soil were lower than those of corresponding non-rhizosphere soil at all Cd levels for T. caerulescens and P. purpureum; T. caerulescens and P. purpureum did not affect less bioavailable Cd fractions. Concentrations of acid extractable Cd in the rhizosphere of the P. alopecuroides cultivars were not reduced at any Cd level. Differences in Cd accumulation among the three Pennisetum grasses were mainly attributable to root biomass and Cd TFs rather than rhizosphere Cd mobility.

Cadmium Accumulation Characteristics of Four Herbs

A pot-based experiment was conducted to study the Cd tolerance and accumulation characteristics of four invasive herbs (Galinsoga quadriradiata, Panicum dichotomiflorum, Setaria geniculata, and Lolium persicum) under exposures of 0 (T0), 5 (T5), 25 (T25), and 50 mg·kg-1 (T50) soil Cd concentrations to screen for potential Cd accumulators for phytoremediation. The results showed that the biomasses of both shoots and roots of G. quadriradiata had no significant changes compared to the control (T0) samples under all Cd treatments, whereas the biomass of the other three Poaceae species significantly decreased under the T25 or T50 treatment. The results indicate that G. quadriradiata had stronger Cd tolerance than the other three species. The Cd concentrations in the shoots and roots of the four herbs significantly increased with an increase in soil Cd concentrations, but the shoot bioconcentration factors (SBCF) of the four plant species significantly decreased under T5, T25, and T50 treatment. The SBCF of G. quadriradiata and P. dichotomiflorum were greater than 1 whereas those of S. geniculata and L. persicum were lower than 1. The translocation factors (TF) of G. quadriradiata were 0.93, 0.73, and 1.04 under T5, T25, and T50 treatment, respectively, which were significantly higher than those of the other three plants under the same soil Cd concentration. In addition, both the total Cd and shoot Cd contents of G. quadriradiata were notably higher than in the other three species under the same Cd treatment. Moreover, 90% of the Cd in G. quadriradiata could be transferred aboveground, which was significantly higher than for the other three plants. Based on our comprehensive comparison of Cd tolerance and accumulation capacity, we suggest that G. quadriradiata is a high-Cd accumulator with considerable phytoremediation potential.

Antagonistic effects of EDTA against biochemical toxicity induced by Cr(VI) in Hordeum vulgare L. seedlings.

The present study aims at the amelioration of chromium Cr(VI) toxicity using ethylenediaminetetraacetic acid (EDTA), and to understand the interactive effects of Cr(VI) and EDTA with respect to seedling growth, lipid peroxidation as assessed from malondialdehyde, pigments and antioxidative enzymes in Hordeum vulgare L. Following multivariate statistical techniques were used to study binary interactions between Cr(VI) and EDTA: 2-way ANOVA, Tukey's multiple comparison test, multiple regression with interaction between Cr an EDTA, beta coefficients, path analysis and non-metric multidimensional scaling (NMDS). The present study revealed that the EDTA decreases lipid peroxidation induced by Cr(VI) and ameliorates the antioxidative defence system and pigment constitution of seedlings grown in Cr(VI) containing media. EDTA-Cr(VI) interaction decreased the Cr content in the seedlings which may be attributed to the chelating effect of EDTA. The root and shoot bioconcentration factors, the ratio of Cr content in the plant to that in the medium, were decreased by addition of EDTA to Cr(VI), indicating a decrease in the uptake of Cr by the seedlings from the medium. NMDS revealed that the ranking of the studied parameters is maintained by ordination on two axes. The study established that EDTA is antagonistic to Cr(VI) induced biochemical toxicity, and improves the antioxidative defence system, increases the chlorophyll content, and decreases Cr uptake in barley seedlings.

Comparing chromium phyto-assessment in Brachiaria mutica and Leptochloa fusca growing on chromium polluted soil

Industrial discharge of chromium (Cr) into environment puts serious threat on living beings due to its potent toxicity. Phytostabilization, a type of in-situ phytoremediation is aimed to immobilize and stabilize the toxic elements in soil using root system of metal resistant potential plants. To evaluate the phytostabilization potential of two grass species Brachiaria mutica and Leptochloa fusca, a pot study was conducted using soil spiked with different concentrations of Cr (control, 25, 50 and 100 mg kg−1). Three plants were sown in each pot with three replications and arranged following completely randomized design. After three months of growth, the plants were harvested and above and below ground plant’s parts were analyzed for various growth and physiological parameters. Data revealed that plant biomass, chlorophylls and carotenoids reduced substantially with increasing Cr concentration. Antioxidant enzymatic activity increased significantly in L. fusca as compared to B. mutica with increasing Cr levels (up to 50 mg kg−1), then reduced at maximum Cr level (100 mg kg−1) in both grasses. Leptochloa fusca performed better with maximum root Cr accumulation 93.7 μg plant−1, shoot Cr accumulation 24.7 μg plant−1, root bioconcentration factor (BCF) 2.0, shoot BCF 0.08, shoot TF 0.06 and MTI 87%. While B. mutica showed maximum root Cr accumulation 18.4 μg plant−1, shoot Cr accumulation 7.6 μg plant−1, shoot BCF 0.03, root BCF 1.28, shoot TF 0.04, and MTI 56%. These results showed that L. fusca possessed good potential with better Cr bioaccumulation, MTI, BCF and antioxidant activities compared to B. mutica. Hence L. fusca can be used as good phytostabilizing agent for the soils contaminated with lower to moderate levels of Cr.

Effects of intercropping accumulator plants and applying their straw on the growth and cadmium accumulation of Brassica chinensis L.

Two pot experiments were conducted to study the effects of intercropping cadmium (Cd) accumulator plants (Stellaria media (L.) Villars, Cardamine hirsuta, Cerastium glomeratum Thuill, and Galium aparine L.) and applying their straw on the growth and Cd accumulation of Brassica chinensis L. Intercropping with four accumulator plants reduced the biomass, water content, and photosynthetic pigment content of B. chinensis compared with monoculture. Intercropping with accumulator plants increased the Cd content in the roots and shoot of B. chinensis, and the translocation factor (TF), root bioconcentration factor (root BCF), and shoot bioconcentration factor (Shoot BCF) increased. The soil pH decreased and the soil available Cd content increased by intercropping. Thus, intercropping with four accumulator plants can promote the Cd uptake of B. chinensis. The straw of four accumulator plants reduced the biomass, water content, and photosynthetic pigment content of B. chinensis compared with the control. The straw of S. media and C. hirsute increased the Cd content in the roots and shoots of B. chinensis, TF, root BCF, and shoot BCF. The straw of C. glomeratum and G. aparine decreased the Cd content in the roots and shoots of B. chinensis, TF, root BCF, and shoot BCF. The soil pH increased and the soil available Cd content decreased by application of straw. Thus, the straw of C. glomeratum and G. aparine can reduce the Cd uptake of B. chinensis.

Accumulation and associated phytotoxicity of novel chlorinated polyfluorinated ether sulfonate in wheat seedlings

Novel alternatives of perfluorooctane sulfonate (PFOS), chlorinated polyfluorinated ether sulfonates (Cl-PFAESs) are increasingly being detected in the aquatic and terrestrial environment. Previous studies mainly focused on aquatic biota; however, the knowledge about the ecotoxicological risk they pose to terrestrial plants was still lacking. In this study, the accumulation of two Cl-PFAES (6:2 and 8:2 Cl-PFAES) and PFOS in wheat seedlings at environmentally relevant levels (50 and 100 μg L−1) was investigated. Concentrations of Cl-PFAESs in the roots were an order of magnitude higher than those in shoots, indicating that they were primarily accumulated in the roots. The values of root and shoot bioconcentration factor was comparable between 6:2 Cl-PFAES and PFOS. However, these indexes of 8:2 Cl-PFAES were 42–91% higher and 70–76% lower than PFOS, respectively. As a result, 6:2 Cl-PFAES had a similar accumulation pattern as PFOS, whereas 8:2 Cl-PFAES was predominantly restricted to the roots, which might be attributed to their hydrophobicity and carbon chain length. In addition, at 250 mg L−1 of Cl-PFAESs, plant biomass and pigment content were 24–30% and 0.4–18%, respectively, which were lower than those of PFOS. As compared with PFOS, Cl-PFAESs induced higher levels of root membrane permeability, reactive oxygen species and malondialdehyde content, as well as reduced the activities of antioxidant enzymes and glutathione content. These suggested the occurrence of a severer oxidative damage and the breakdown of the antioxidant defence system in wheat cells. Therefore, we conclude that Cl-PFAESs might pose a higher potential threat to the environment than PFOS.

Phytoremediation potential of Pterocypsela laciniata as a cadmium hyperaccumulator.

To identify new cadmium (Cd) hyperaccumulators, the artificially high soil Cd concentration method was used to screen six common farmland weeds. Among them, only Pterocypsela laciniata (Houtt.) C. Shih showed characteristics of a Cd hyperaccumulator and was selected for further studies. In pot experiments, soil Cd concentrations of 5, 10, and 25mgkg-1 increased the biomass and photosynthetic pigment concentrations in P. laciniata when compared with the control, whereas 75 and 100mgkg-1 decreased them (the maxima were at 10mgkg-1 soil Cd). The antioxidant enzyme activities and the soluble protein concentrations of P. laciniata showed similar trends as biomass. The Cd concentrations in roots and shoots of P. laciniata increased as soil Cd concentration increased. When the soil Cd concentration was 50mgkg-1, the Cd concentration in the shoots of P. laciniata was 116mgkg-1 (the critical value for Cd hyperaccumulators is 100mgkg-1). Both the root and shoot bioconcentration factors of P. laciniata were larger than 1.0, and the translocation factor exceeded 1.0 in almost all treatments. The Cd extractions by the shoots and whole plants of P. laciniata reached maxima at 208 and 375μg plant-1, respectively. The Cd extractions by P. laciniata were different between two ecotypes. Therefore, P. laciniata is a Cd hyperaccumulator that could remediate Cd-contaminated soils, but the ecotypes should be considered when using P. laciniata for phytoremediation.

Cadmium Tolerance and Phytoremediation Strategies of Selected Tropical plants Cultivated on Industrial Dump Site under the Influences of Two Mycobionts

This research was carried out on a waste disposal site of a paint industry in Ijebu- Ijesha, Osun State, Nigeria in an attempt to assess the cadmium toxicity tolerance and bioremediation strategies of selected tropical plants cultivated under the influence of two mycobionts. On the waste disposal site, two plots (Plot A and B) having size of about 9 m by 12 m each were prepared with a control plot (Plot C) which is a non-polluted site. The experimental design on the first plots (Plot A) was 4x2x3 in which viable seeds of the four selected weeds were grown and inoculated with two mycobionts (Glomus intraradices and Glomus mosseae) respectively in a randomized complete block design with three replicates. However, on the second (Plot B) and control plots, only the seeds of the weeds were grown without mycorrhiza treatment using the same experimental design of 4x3 respectively. After Twelve weeks of planting, each plant was harvested, separated into root and shoot tissues and analysed for Cd concentrations using Atomic Absorption Spectrophotometry (AAS). Data collected were subjected to descriptive and inferential statistics. The highest (18.51 mg/kg) concentrations of Cd were reported in Amaranthus spinosus with root and shoot bioconcentration factors; and transfer factors greater than 1.00. Out of the four plants, 75% act as cadmium phytostabilizers in the absence of inocula and were good candidates for the biomanagement of hazardous sites while all the plant displayed the characteristics of a cadmium phytoextractor under mycorrhizal inoculation with Amaranthus spinosus having the highest mobility indices of cadmium under the influence of Glomus intraradices. The study concluded that the four weeds are good Cd phytoextractors in the remediation and biomanagement of marginal lands under bioaugmentation.

Turn bane into a boon: Application of invasive plant species to remedy soil cadmium contamination

Cadmium (Cd) is one of the mostly hazardous soil pollutants and has threatened human health by accumulating in grains of crops. Phytoremediation is a promising technique to remedy soil Cd contamination, but reported Cd hyperaccumulators remain limited. In this study, we explored potential applicability of three invasive plant species (Chromolaena odorata, Bidens pilosa and Praxelis clematidea) to remove soil Cd using greenhouse experiment. Results showed that the three species grew well with Cd treatments compared to the controlled individuals, suggesting that the species had high Cd tolerance by physiological adjustments such as up-regulating the antioxidant enzyme activities. The only exception was that the height of P. clematidea in the 60 mg kg−1 Cd treatment was less than that in the control. Within the tested Cd concentration range, the C. odorata exhibited high bioaccumulation characteristics that meet the recommended standards to identify as a hyperaccumulator (shoot Cd concentration > 100 mg kg−1 with bioconcentration and transfer factors > 1). The other two species had also the shoot bioconcentration factor and transfer factor greater than one, while the shoot Cd concentration was relatively lower. Our results highlight a potential applicability of the invasive species used in this study for remediation of the soil Cd contamination, which turns bane into a boon.

Cadmium accumulation characteristics of floricultural plant Cosmos bipinnata

ABSTRACTThe artificially high soil cadmium (Cd) concentration screening method was used to screen Cd-hyperaccumulators from floricultural plants. Among the five species of floricultural plants screened, Cosmos bipinnata showed the characteristics of Cd-accumulators. A pot experiment was conducted to further study Cd accumulation characteristics of C. bipinnata. The results showed that the biomass, chlorophyll content, superoxide dismutase activity, peroxidase activity and soluble protein content of C. bipinnata first increased and later decreased with the increase in soil Cd concentration, but the carotenoid content and catalase activity of C. bipinnata reduced. Cd contents in roots, stems, leaves and shoots of C. bipinnata increased with increasing soil Cd concentration. When the soil Cd concentration was 50 mg kg−1, the Cd content in shoots was up to 112.62 mg kg−1, which was higher than the Cd-hyperaccumulator critical value. The root and shoot bioconcentration factors exceeded 1 in various Cd treatments, but the translocation factors were less than 1. When the soil Cd concentration was 50 mg kg−1, the Cd accumulation in shoots achieved the maximum of 224.30 μg plant−1. Therefore, considering the tolerance and accumulation of Cd, C. bipinnata is a Cd-accumulator that could be used to remediate Cd-contaminated urban soil.

Influence of NaCl-salinity on Pb-uptake behavior and growth of River Red gum tree (Eucalyptus camaldulensis Dehnh.)

Lead (Pb) is one of the most toxic and persistent elements, with no known biological role. High concentrations of lead enter saline soils through anthropogenic activities and industrial waste. The decontamination of Pb polluted sites through phytoremediation, especially by using woody plants, is an attractive approach. Eucalyptus camaldulensis is a good accumulator of Pb and a recommended tree species for reclamation of saline soils. However, there is very limited knowledge about the Pb-uptake behavior of Eucalyptus camaldulensis under saline conditions. The objective of this study was to examine the simultaneous impact of NaCl salinity and Pb stress on the phytoremedial potential and growth behavior of E. Camaldulensis. Six-week-old Eucalyptus camaldulensis plants with uniform morphological features were transferred into hydroponic conditions, and they were exposed to the NaCl salinity stress at 200 mM and Pb stress at 10 mg L-1 and 20 mg L-1 (Pb1 and Pb2, respectively). The plants showed a 100% survival rate in all treatments. All the morphological parameters (plant height, plant diameter, and shoot dry weight) for E. Camaldulensis were significantly affected when exposed to Pb or Pb + NaCl-salinity, with the exception of root length which was 36% higher in Pb2 as compared to the control. The Pb uptake (mg Pb plant-1) was much higher (49.3) under Pb2 + NaCl-salinity, as compared to the control (1.2) and other treatments, which shows that saline conditions increased the Pb-uptake in E. Camaldulensis. The order of deposition of Pb (mg Pb kg-1 of dry weight) in plant parts was root (103.4) >> shoot (17.5) > leaves (13.6). Similarly, the bioconcentration factor (BCF) of the roots was 4 to 6 times higher than shoot BCF.

Cadmium accumulation and tolerance in the Cd‐accumulator Capsella bursa‐pastoris

Advances in phytoremediation research require the selection of new hyperaccumulators or accumulators and investigations of their tolerance and accumulation of heavy metals. Two concentration gradient experiments (preliminary and verification), involving the same soil Cd concentrations (0, 25, 50, 75, 100, and 125 mg kg−1), were conducted to study Cd accumulation and tolerance in Capsella bursa‐pastoris. In the preliminary and verification concentration gradient experiments, the Cd content in shoots of C. bursa‐pastoris exceeded 100 mg kg−1 at a soil Cd concentration of 50 mg kg−1, and the maxima of Cd contents in shoots were 307.67 and 369.20 mg kg−1 at 125 mg kg−1 Cd in soil, respectively. The shoot bioconcentration factor of C. bursa‐pastoris was greater than 1, but the translocation factor was less than 1.0 in the preliminary and verification concentration gradient experiments. In the verification concentration gradient experiment, the malondialdehyde content and the activities of superoxide dismutase, peroxidase, and catalase increased compared with the control. Therefore, C. bursa‐pastoris is a Cd‐accumulator with strong tolerance to Cd, and could be used to remediate Cd‐contaminated farmland soil in winter. © 2014 American Institute of Chemical Engineers Environ Prog, 2014 34: 663–668, 2015

Screening of a new cadmium hyperaccumulator, Galinsoga parviflora, from winter farmland weeds using the artificially high soil cadmium concentration method.

A new method, the artificially high soil cadmium (Cd) concentration method, was used to screen for Cd hyperaccumulators among winter farmland weeds. Galinsoga parviflora was the most promising remedial plant among 5 Cd accumulators or hyperaccumulators. In Cd concentration gradient experiments, as soil Cd concentration increased, root and shoot biomass decreased, and their Cd contents increased. In additional concentration gradient experiments, superoxide dismutase and peroxidase activities increased with soil Cd concentrations up to 75 mg kg(-1) , while expression of their isoenzymes strengthened. Catalase (CAT) activity declined and CAT isoenzyme expression weakened at soil Cd concentrations less than 50 mg kg(-1) . The maxima of Cd contents in shoots and roots were 137.63 mg kg(-1) and 105.70 mg kg(-1) , respectively, at 100 mg kg(-1) Cd in soil. The root and shoot bioconcentration factors exceeded 1.0, as did the translocation factor. In a field experiment, total extraction of Cd by shoots was 1.35 mg m(-2) to 1.43 mg m(-2) at soil Cd levels of 2.04 mg kg(-1) to 2.89 mg kg(-1) . Therefore, the artificially high soil Cd concentration method was effective for screening Cd hyperaccumulators. Galinsoga parviflora is a Cd hyperaccumulator that could be used to efficiently remediate Cd-contaminated farmland soil.

Cadmium accumulation characteristics of the winter farmland weeds Cardamine hirsuta Linn. and Gnaphalium affine D. Don

In a preliminary study, we found that the cadmium (Cd) concentrations in shoots of the winter farmland weeds Cardamine hirsuta Linn. and Gnaphalium affine D. Don exceeded the critical value of a Cd-hyperaccumulator (100mgkg(-1)), indicating that these two farmland weeds might be Cd-hyperaccumulators. In this study, we grew these species in soil containing various concentrations of Cd to further evaluate their Cd accumulation characteristics. The biomasses of C. hirsuta and G. affine decreased with increasing Cd concentrations in the soil, while the root/shoot ratio and the Cd concentrations in shoot tissues increased. The Cd concentrations in shoots of C. hirsuta and G. affine reached 121.96 and 143.91mgkg(-1), respectively, at the soil Cd concentration of 50mgkg(-1). Both of these concentrations exceeded the critical value of a Cd-hyperaccumulator (100mgkg(-1)). The shoot bioconcentration factors of C. hirsuta and G. affine were greater than 1. The translocation factor of C. hirsuta was less than 1 and that of G. affine was greater than 1. These findings indicated that C. hirsuta is a Cd-accumulator and G. affine is Cd-hyperaccumulator. Both plants are distributed widely in the field, and they could be used to remediate Cd-contaminated farmland soil in winter.

Application of Sewage Sludge for Growing Alfalfa, Its Effects on the Macro-Micronutrient Concentration, Heavy Metal Accumulation and Translocation

Alfalfa (Medicago Sativa) was grown by mixing sewage sludge at 0 (control soil), 20 (SSA2), 40 (SSA4), 60 (SSA6), and 80 (SSA8) t ha-1(w/w) amendment ratios to the soil. The soil pH decreased but, the electrical conductivity, organic matter, total N, available and total P, exchangeable and total K and Na, exchangeable Mg, DTPA-extractable Fe, Zn, Mn, Cu, Ni, Pb, and total Zn, Cu, Cr, and Pb increased in the soil. The shoot P, K, Ca, Mg, Fe, Zn, Mn, Cu, and root N, P, K, Na, Fe, Zn, Mn, Cu, Ni, and Cr concentrations increased but the root Mg concentration decreased in the plant. The translocation factor (TF) for Fe, Zn, Mn, and Cu (nutrients) increased at SSA2 and SSA4 as compared to SSA6, SSA8, and control soil. The TF was mostly higher than 1 for Zn, Cu, and Mn and for Fe it was lower than 1. The TF for Ni, Cr, and Pb (non-nutrients) was the highest in the control soil. The TF was lower than 1 for Ni and Cr in all treatments. For Pb it was more than 1 at SSA2, SSA4, and the control soil. The shoot bioconcentration factor (BCF) for Fe, Zn, Mn, and Cu at SSA2 and SSA4 were mostly higher than SSA6, SSA8, and the control soil. While the root BCF for Fe, Mn, Ni, and Cr were highest at SSA8, for Cu it was highest in the control soil. Both shoot and root BCF for all elements at all treatments were lower than 1. The total fresh and dried biomasses increased at SSA 2 , SSA 4 , and SSA 6 compared to the control soil, however, they were reduced by SSA 8 . The tolerance index (TIN) was greater than 100% for SSA 2 , SSA 4 , and SSA 6 . Although, the TIN was higher than 100% at SSA6, the value was lower than SSA2 and SSA4. It indicates that the plants are stressed at the amendments of sewage sludge at more than 40 ton ha -1 to the soil.