Interaction of arsenic and phosphate on their uptake and accumulation in Chinese brake fern

Interactive effects of arsenate (As (V)) and phosphate (Pi) were investigated under hydroponic culture. Arsenic concentrations in fronds and roots of Chinese brake fern (Pteris vittata L.) significantly (p < 0.05) increased with increasing As (V), but decreased (p < 0.05) with increasing Pi in nutrient solution. Phosphate uptake was significantly (p < 0.05) inhibited by 1000 micromol L(-1) As (V). Under 100 micromol L(-1) As (V), frond phosphorus (P) increased at 100 and 1000 micromol L(-1) Pi, and root P increased at 250 micromol L(-1) Pi exposures. Arsenic and P concentrations in fronds and roots of Chinese brake fern were negatively correlated (p < 0.05). Arsenate treatments enhanced As and P transport to fronds, while increasing Pi inhibited their transportation, with highest frond P and As (%) obtained under 100 micromol L(-1) treatment. pH values in nutrient solution increased with increasing exposure time, but decreased with increasing Pi levels. Dissolved organic carbon (DOC) contents (dry weight) in nutrient solution decreased with increasing Pi levels, both for treatments with and without As (V). Arsenate at 1000 micromol L(-1) significantly (p < 0.05) increased DOC contents, especially for treatment without Pi. Six organic acids were detected in root exudates of Chinese brake fern, with oxalic and malic acids being most dominant.

Cadmium tolerance and accumulation in cultivars of a high-biomass tropical tree (Averrhoa carambola) and its potential for phytoextraction

Averrhoa carambola is a high-biomass tropical tree that has been identified as a Cd accumulator. In the present study, field survey, pot, and hydroponic experiments were conducted to investigate the variation of Cd tolerance and accumulation in cultivars of A. carambola as well as its potential for phytoextraction. In the field survey, it was found that concentrations of Cd in aerial tissues of A. carambola varied greatly among sites and cultivars. The Cd bioconcentration factors (BCFs) and Cd removals by the field-grown A. carambola differed significantly among sites but not among cultivars. Nonetheless, all four carambola cultivars investigated were able to accumulate considerably high concentrations of Cd in their shoots, which indicated that the 4-yr-old carambola stands could remove 0.3 to 51.8% of the total Cd content in the top 20-cm soil layer. When cultured in Cd-spiked soils, the carambola cultivar Hua-Di always showed higher Cd tolerance than the other cultivars; however, this tendency was not confirmed by hydroponic experiment. The Cd BCFs of cultivar Thailand grown in soils with 6 and 12 mg Cd kg(-1) were highest among cultivars, whereas this trend was reversed at 120 mg Cd kg(-1) treatment. Nevertheless, the pot- and hydroponics-grown carambola cultivars generally showed higher capacities to tolerate and accumulate Cd, compared with the control species. The present results indicate that a strong ability to tolerate and accumulate Cd seems to be a trait at the species level in A. carambola, although some degree of variances in both Cd tolerance and accumulation exists among cultivars.

The role of radial oxygen loss and root anatomy on zinc uptake and tolerance in mangrove seedlings

Root anatomy, radial oxygen loss (ROL) and zinc (Zn) uptake and tolerance in mangrove plants were investigated using seedlings of Aegiceras corniculatum, Bruguiera gymnorrhiza and Rhizophora stylosa. The results revealed that B. gymnorrhiza, which possessed the 'tightest barrier' in ROL spatial patterns among the three species studied, took up the least Zn and showed the highest Zn tolerance. Furthermore, zinc significantly decreased the ROL of all three plants by inhibition of root permeability, which included an obvious thickening of outer cortex and significant increases of lignification in cell walls. The results of SEM X-ray microanalysis further confirmed that such an inducible, low permeability of roots was likely an adaptive strategy to metal stress by direct prevention of excessive Zn entering into the root. The present study proposes new evidence of structural adaptive strategy on metal tolerance by mangrove seedlings.

Femtosecond laser-drilling-induced HgCdTe photodiodes

Femtosecond-laser drilling may induce holes in HgCdTe with morphology similar to that induced by ion-milling in loophole technique. So-formed hole structures are proven to be pn junction diodes by the laser beam induced current characterization as well as the conductivity measurement. Transmission and photoluminescence spectral measurements on a n-type dominated hole-array structure give rise to different results from those of an ion-milled sample.

Vegetation changes and partitioning of selenium in 4-year-old constructed wetlands treating agricultural drainage

The knowledge of selenium (Se) partitioning in treatment wetlands and wetland vegetation management are essential for long-term effective operation of constructed wetlands treating Se-laden agricultural tile-drainage in central California. In this field study, samples from different compartments of treatment wetlands were collected and the vegetation change in each wetland cell was examined four years after the wetland's inception. The results showed that saltgrass (Distichlis spicata) and rabbitfoot grass (Polypogon monspeliensis) were less competitive than cattail (Typha latifolia) and saltmarsh bulrush (Scirpus robustus). Over 90% of the wetland cell originally vegetated with saltgrass or rabbitfoot grass was occupied by invasive plants--i.e., when invasive species were not controlled in the wetlands. More Se was likely found in sediments from vegetated regions, compared to the unvegetated areas of the wetland cell. Particularly, rhizosphere sediments accumulated about 4-fold more Se than non-rhizosphere sediments. Among the total Se retained in the wetland 90% of the total Se was partitioned in the top 10-cm layer of sediment. The Se accumulation in plant materials accounted for about 2% of the total Se mass retained in each wetland cell. This field study demonstrated that wetland plants play significant roles in the treatment of Se-laden agricultural drainage.

Constitutional tolerance to heavy metals of a fiber crop, ramie (Boehmeria nivea), and its potential usage

It is observed that ramie (Boehmeria nivea), an economic fiber crop, can establish and colonize metal-contaminated sites in China. Metal tolerance and accumulation by ramie originating from 13 metal-contaminated and 4 "clean" sites in China were compared under field and hydroponic conditions. All selected populations and germplasms displayed good growth performance under diverse metal-contaminated habitats; while growth responses, metal accumulation and tolerance were similar among the 8 populations and 2 germplasms when exposed to solutions containing elevated As, Cd, Pb, or Zn in the laboratory. These revealed that ramie possesses a certain degree of constitutional metal tolerance. To our knowledge, this is the first report of constitutional metal tolerance possessed by a fiber crop. Ramie can be considered as a good candidate for both fiber production and phytoremediation of sites contaminated by multi-metals, as it accumulates relative low metal concentrations, but possesses both high biomass and high economic value.

Mixed heavy metals tolerance and radial oxygen loss in mangrove seedlings

The effects of a mixture of heavy metals (Pb, Zn and Cu) on growth, radial oxygen loss (ROL) and the spatial pattern of ROL were investigated in mangrove seedlings of three species: Aegiceras corniculatum, Avicennia marina and Bruguiera gymnorrhiza. Heavy metals inhibited the growth of seedlings and led to decreased ROL and changes in the "tight" barrier spatial pattern of ROL. There was a significant positive correlation between the amount of ROL from the roots of seedlings and metal tolerance. The species with the highest ROL amount, B. gymnorrhiza, were also the most tolerant to heavy metals. The "tight" barrier spatial ROL pattern was also related to metal tolerance in the seedlings. Therefore, we conclude that both ROL amount and "tight" barrier spatial ROL pattern in the roots of the mangrove seedlings play an important role in resistance to heavy metal toxicity.

A comparison of arsenic tolerance, uptake and accumulation between arsenic hyperaccumulator, Pteris vittata L. and non-accumulator, P. semipinnata L.--a hydroponic study

The differences in arsenic (As) tolerance, uptake and accumulation between Pteris vittata (an As hyperaccumulator) and P. semipinnata (nonaccumulator) were investigated under hydroponic conditions. The results showed that As uptake by P. vittata was significantly higher (p<0.05) than that of P. semipinnata. Significantly higher concentrations of As accumulated in the fronds of P. vittata, while in the roots of P. semipinnata. The short-term (<24h) uptake kinetics were fitted a hyperbolic equation which could be divided into linear and saturable components (described by Michaelis-Menten kinetics/model). The increase in hydrogen peroxide (H(2)O(2)) content in both plant species significantly correlated (p<0.05) with increasing As content in the plants and As exposure time, especially for midrib of P. semipinnata. P. semipinnata showed higher concentrations of H(2)O(2) than those of P. vittata. The relative electrical conductivity (REC, %) values in the root and pinnae followed a similar trend as plant H(2)O(2) contents, increasing with As exposure, especially for P. semipinnata. Significantly higher REC (%) values (p<0.05) were observed in the root than that in pinnae of P. semipinnata. The results indicated that high doses of As produced oxidative damages in both plant species.

Intraspecific differences of arbuscular mycorrhizal fungi in their impacts on arsenic accumulation by Pteris vittata L

It has been shown that Pteris vittata, an arsenic hyperaccumulator, could be colonized by arbuscular mycorrhizal (AM) fungi either in controlled conditions or at field sites. However, physiological mechanisms of AM fungi influencing As accumulation and tolerance in the plant are not fully elucidated. Two predominant fungal species, Glomus mosseae and Glomus geosporum, and a rapidly sporulating fungal species, Glomus etunicatum, associated with P. vittata were isolated from As-contaminated soils. Two uncontaminated isolates, G. mosseae and G. etunicatum, served as reference isolates. Based on germination of spores exposed to elevated As, Pb and Zn concentrations, two contrasting isolates of G. mosseae were selected to investigate As accumulation in two populations of P. vittata [from an uncontaminated site of Hong Kong (HK) and an As-contaminated site located in Jinchuantang (JCT) of Hunan Province, China, respectively] under hydroponic culture and pot trials. At lower levels of As exposure (50-200 microM), both uncontaminated and metal-contaminated isolates of G. mosseae significantly increased short-term As influx into roots of P. vittata. However, at higher levels of As exposure (400-1000 microM), only uncontaminated isolates significantly increased short-term As influx into roots. When growing on 100mg As kg(-1) soils, uncontaminated isolates exhibited a higher level of colonization in roots of P. vittata than metal-contaminated isolates and only the former significantly increased As accumulation in roots of HK population and in fronds of JCT population. It was concluded that there were intraspecific differences of AM fungi in their impacts on As accumulation by P. vittata.

The relationship of root porosity and radial oxygen loss on arsenic tolerance and uptake in rice grains and straw

The correlations among arsenic (As) accumulation in grains and straw, rates of radial oxygen loss (ROL), and porosity of roots using 25 rice cultivars were investigated based on two pot experiments: (1) soil with addition of 100mg As kg(-1) for analysis of As in grains and straw, and (2) deoxygenated solution for analyzing rates of ROL and porosity of roots. The results showed that there were great differences in grain As (0.71-1.72 mg kg(-1)) and straw As (15.6-31.7 mg kg(-1)), rates of ROL (7.40-13.24 mmol O(2)kg(-1)root d.w. h(-1)), and porosity (20.91-33.08%) among the cultivars. There were significant negative correlations between As in grains or straw and ROL and porosity, and significant positive correlations between rates of ROL and porosities, respectively. Rice cultivars with high porosities tended to possess higher rates of ROL, and had higher capacities for limiting the transfer of As to aboveground tissues.

Variation in arsenic, lead and zinc tolerance and accumulation in six populations of Pteris vittata L. from China

Arsenic, Pb and Zn tolerance and accumulation were investigated in six populations of Pteris vittata collected from As-contaminated and uncontaminated sites in southeast China compared with Pteris semipinnata (a non-As hyperaccumulator) in hydroponics and on As-contaminated soils. The results showed that both metallicolous and nonmetallicolous population of P. vittata possessed high-level As tolerance, and that the former exhibited higher As tolerance (but not Pb and Zn tolerance) than the latter. In hydroponic culture, nonmetallicolous population clearly showed significantly higher As concentrations in fronds than those in metallicolous populations. In pot trials, As concentrations in fronds of nonmetallicolous population ranged from 1060 to 1639 mg kg(-1), about 2.6- to 5.4-folds as those in metallicolous populations. It was concluded that As tolerance in P. vittata resulted from both constitutive and adaptive traits, Pb and Zn tolerances were constitutive properties, and that nonmetallicolous population possesses more effective As hyperaccumulation than metallicolous populations.

The role of arsenate reductase and superoxide dismutase in As accumulation in four Pteris species

Using arsenic (As) hyperaccumulators to extract As from contaminated soils is an effective and low-cost technology. Most of the known As hyperaccumulators belong to Pteris species. The present study aims to explore the responses and role of arsenate reductase (AR) and superoxide dismutase (SOD) in As hyperaccumulating fern species (Pteris vittata, and P. multifida) and non-As hyperaccumulating species (P. ensiformis, and P. semipinnata) when grown in soils added with 0 (control), 100, and 200 mg/kg (dry weight) of arsenic as Na(2)HAsO(4).7H(2)O. The results show that AR activities of roots, SOD activities and As concentrations in both roots and fronds of the four Pteris plants increased when exposed to As-contaminated soils. AR activities of roots were much higher, but SOD activities and As concentrations of roots were lower than those of fronds. It is concluded that AR of roots and SOD of both roots and fronds may play important roles to accumulate and detoxify As in the four Pteris species.

Metal accumulation and arbuscular mycorrhizal status in metallicolous and nonmetallicolous populations of Pteris vittata L. and Sedum alfredii Hance

Although Pteris vittata L. and Sedum alfredii Hance have been identified as an As hyperaccumulator and a Zn/Cd hyperaccumulator, respectively, for a few years, variations in metal accumulation among populations and their arbuscular mycorrhizal (AM) status have not been fully explored. Six populations of P. vittata and four populations of S. alfredii from southeast China were investigated. Up to 1,373 As, 680 Pb, 376 Zn, 4.8 Cd, 169 Cu mg kg(-1) in fronds of P. vittata and 358 As, 2,290 Pb, 23,403 Zn, 708 Cd, 342 Cu mg kg(-1 )in shoots of S. alfredii were detected. Constitutive properties of As and Zn hyperaccumulation in metallicolous populations of P. vittata and S. alfredii, respectively, were confirmed. However, Cd hyperaccumulation in S. alfredii varied among populations. The two hyperaccumulators varied in efficiency in taking up other heavy metals. Different metal tolerance strategies adopted by the two hyperaccumulators varied among plant species and metal species. Low to moderate levels of AM colonization in P. vittata (4.2-12.8%) and S. alfredii (8.5-45.8%) were observed at uncontaminated and metal-contaminated sites. The relationship between metal concentrations and AM colonization in the two hyperacumulators was also examined. The abundance of AM fungal spores ranged from 16 to 190 spores per 25 g soil. Glomus microaggregatum, Glomus mosseae, Glomus brohultii and Glomus geosporum were the most common species associated with both P. vittata and S. alfredii. To our knowledge, this is the first report of AM fungal status in rhizosphere of P. vittata and S. alfredii.

Solubility and accumulation of metals in Chinese brake fern, vetiver and rostrate sesbania using chelating agents

Greenhouse experiments were conducted to study the effects of chelating agents on the growth and metal accumulation of Chinese brake fern (Pteris vittata L.), vetiver (Vetiveria zizanioides L.), and rostrate sesbania (Sesbania rostrata L.) in soil contaminated with arsenic (As), Cu, Pb, and Zn. Among the five chelating agents used [ethylenediaminetriacetic acid (EDTA), hydroxyethylenediaminetriacetic acid (HEDTA), nitrilotriacetic acid (NTA), oxalic acid (OA), and phytic acid (PA)], OA was the best to mobilize As, EDTA to mobilize Cu and Pb, and HEDTA to mobilize Zn from soil, respectively. The biomass of vetiver was the highest, followed by rostrate sesbania. All chelating agents inhibited the growth of Chinese brake fern and rostrate sesbania, but HEDTA significantly increased the aboveground biomass of vetiver. Dry weights of both Chinese brake fern and rostrate sesbania decreased with increasing EDTA concentrations amended in the soil, especially in treatments with high EDTA concentrations. EDTA and HEDTA enhanced Cu, Zn, and Pb, but lowered As accumulation in all three plant species, except for As in vetiver, while OA significantly enhanced As accumulation in the aboveground part of vetiver. Concentrations of Cu, Zn, and Pb in the aboveground parts of plants increased significantly with the increase of EDTA concentrations and treatment time. In addition to As, Chinese brake fern also accumulated the highest Cu, Pb, and Zn in its aboveground parts among the three plant species grown in metal-contaminated soil with EDTA/HEDTA treatments. This species, therefore, can be used to simultaneously clean up As, Cu, Pb, and Zn from contaminated soils with the aid of EDTA or HEDTA.

Zinc and cadmium accumulation and tolerance in populations of Sedum alfredii

To investigate the variation of Zn and Cd accumulation and tolerance of Sedum alfredii (a newly reported Zn/Cd hyperaccumulator), field surveys and hydroponic experiments were conducted among three populations of this species: two originating from old Pb/Zn mines in Zhejiang (ZJ) and Hunan (HN) Provinces and one from a "clean" site in Guangdong (GD) Province, China. Under field conditions, up to 12,524 and 12,253 mg kg(-1) Zn, and 1400 and 97 mg kg(-1) Cd in shoots of ZJ and HN plants were recorded respectively. Under hydroponic conditions, ZJ and HN plants accumulated significantly higher Zn and Cd in their leaves and stems, and possessed significantly higher Zn and Cd tolerance than GD plants. Among the two contaminated populations, ZJ plants showed higher Cd tolerance and accumulation (in leaves) than HN plants. The present results indicate that significant differences in Zn and Cd accumulation and tolerance exist in populations of S. alfredii.

Cut-off net acid generation pH in predicting acid-forming potential in mine spoils

Acidification of mine wastes can lead to a series of environmental problems, such as acid drainage, heavy metal mobilization, and ecosystem degradation. Prediction of acid-forming potential is one of the key steps in management of sulfide-bearing mine wastes. In this paper, the acid-forming potential of 180 mine waste samples collected from 17 mine sites in China were studied using a net acid generation (NAG) method. The samples contained different contents of total sulfur (ranging from 0.6 to 200 g kg(-1)), pyritic sulfur (ranging from 0 to 100 g kg(-1)), and acid neutralization capacity (ANC, ranging from -41 to 274 kg H2SO4 t(-1)). Samples with high acid-forming potential are generally due to their high sulfur content or low acid neutralization capacity. After the samples were oxidized by H2O2, the amounts of acid generation and the final NAG pH were measured. Results indicated that the final NAG pH gave a well-defined demarcation between acid-forming and non-acid-forming materials. Samples with final NAG pH >or= 5 could be classified as non-acid-forming materials, while those with NAG pH <or= 2.5 could be classified as moderate to strong acid-forming materials. Materials with NAG pH > 2.5, but < 5, had low risk of being acid-forming. The confirmation of cut-off NAG pH will be used as a rapid and cost-effective operational monitoring tool for the in-pit prediction of acid-forming potential of mine wastes and classification of waste types.

Uptake and accumulation of arsenic by 11 Pteris taxa from southern China

A field survey was conducted at a deserted arsenic (As) mine in Guangxi Province, China to explore new potential As hyperaccumulators. In addition, young plants of 11 Pteris taxa were grown in glasshouse conditions for 12 weeks on As-amended soils with 0, 50 and 200 mg As kg(-1). Results of the field survey showed that the fern Pteris fauriei accumulated over 1000 mg As kg(-1) in its fronds. Of the 11 Pteris taxa, Pteris aspericaulis, Pteris cretica var. nervosa, P. fauriei, Pteris multifida, P. multifida f. serrulata, and Pteris oshimensis were all found to hyperaccumulate As in addition to P. cretica 'Albo-Lineata' and Pteris vittata (already reported as As hyperaccumulators). However, Pteris ensiformis, Pteris semipinnata and Pteris setuloso-costulata showed no evidence of As hyperaccumulation. Results also revealed a constitutive property of As hyperaccumulation in different populations of P. cretica var. nervosa, P. multifida, P. oshimensis and P. vittata.

Effects of bacteria on enhanced metal uptake of the Cd/Zn-hyperaccumulating plant, Sedum alfredii

To investigate the effects of bacteria (Burkholderia cepacia) on metal uptake by the hyperaccumulating plant, Sedum alfredii, a hydroponic experiment with different concentrations of Cd and Zn was conducted. It was found that inoculation of bacteria on S. alfredii significantly enhanced plant growth (up to 110% with Zn treatment), P (up to 56.1% with Cd treatment), and metal uptake (up to 243% and 96.3% with Cd and Zn treatment, respectively) in shoots, tolerance index (up to 134% with Zn added treatment), and better translocation of metals (up to 296% and 135% with Cd and Zn treatment, respectively) from root to shoot. In the ampicillin added treatment with metal addition, stimulation of organic acid production (up to an increase of 133% of tartaric acid with Cd treatment) by roots of S. alfredii was observed. The secretion of organic acids appears to be a functional metal resistance mechanism that chelates the metal ions extracellularly, reducing their uptake and subsequent impacts on root physiological processes.

Survival strategies of plants associated with arbuscular mycorrhizal fungi on toxic mine tailings

A field survey of metal concentrations and arbuscular mycorrhizal (AM) components of plants growing on five mining sites was conducted in Chenzhou City, Hunan Province, Southern China and a control site in Hong Kong. Significant differences were observed in the average concentrations of total heavy metals (Pb, Zn, Cu, Cd) and one metalloid (As) in contaminated soils compared with the control site. Gramineae and Compositae were the dominant plant families growing on mine tailings, with Chrysanthemum moritolium (common chrysanthemum), Cynodon dactylon (Bermuda grass), Miscanthus florodulus (Sword grass) and Pteris vittata (Ladder brake fern) commonly found at all sites. AM fungal colonization was detected in most of the plants. Comparing the four common plant species, three components of mycorrhizal colonization (arbuscules, vesicles and coiled hyphae) were found in the roots of C. dactylon and P. vittata growing at Do Shun Long (DSL) mine site. Concentrations of As in fronds were 24-fold higher than in roots of P. vittata with the highest mycorrhizal colonization rate (73%) among all sampling sites. Extensive mycorrhizal colonization (85%) was also recorded in the roots of C. dactylon with As accumulation 57 times higher than in shoots. The four common plants found in metal contaminated sites had developed different strategies for survival in the contaminated sites with the aid of indigenous AM fungi.

The effects of hyperbaric oxygen treatment on lipid peroxidation of pregnant rabbits and their fetus during late pregnancy

OBJECTIVE

To measure the effects of hyperbaric oxygen on lipid peroxidation of pregnant and fetal rabbits during late pregnancy.

METHODS

Sixteen pregnant rabbits were randomly and equally divided into two groups. One, the HBO2 group, was exposed to 2-atm oxygen for 60 min a day from the 21st to the 30th day of gestation, and the other group, non-HBO2 group, did not obtain any hyperbaric oxygen treatment.

RESULTS

On the 30th day of pregnant period, the activity of antioxidant enzyme SOD in plasma of the pregnant rabbits of the HBO2 group was significantly higher than that of the non-HBO2 group, but there was no significant difference in the level of oxidative stress marker 8-iso-PG-F2 alpha between the two groups. As for the fetal rabbits, the SOD activity in umbilical plasma, placenta tissue and fetal brain tissue of HBO2 group was significantly higher than that of the non-HBO2 group, while there was no statistical difference between the concentrations of 8-iso-PG-F2 alpha of HBO2 and non-HBO2 group.

CONCLUSION

HBO2 treatment during the late pregnancy up-regulates the activity of antioxidant enzyme in plasma of pregnant rabbits, placenta, umbilical plasma, and fetal brain. This does not have significant effect on the oxidative stress in these tissues.

Lead and zinc accumulation and tolerance in populations of six wetland plants

Wetland plants such as Typha latifolia and Phragmites australis have been indicated to show a lack of evolution of metal tolerance in metal-contaminated populations. The aim of the present study is to verify whether other common wetland plants such as Alternanthera philoxeroides and Beckmannia syzigachne, also possess the same characteristics. Lead and zinc tolerances in populations of six species collected from contaminated and clean sites were examined by hydroponics. In general, the contaminated populations did not show higher metal tolerance and accumulation than the controls. Similar growth responses and tolerance indices in the same metal treatment solution between contaminated and control populations suggest that metal tolerance in wetland plants are generally not further evolved by contaminated environment. The reasons may be related to the special root anatomy in wetland plants, the alleviated metal toxicity by the reduced rooting conditions and the relatively high innate metal tolerance in some species.

Growth of Vetiveria zizanioides and Phragmities australis on Pb/Zn and Cu mine tailings amended with manure compost and sewage sludge: a greenhouse study

The Lechang lead/zinc (Pb/Zn) mine and Dabao Shan copper (Cu) mine are located at the north of Guangdong Province in southern China. The residual tailings were permanently stored in tailings ponds which required revegetation to reduce their impact on the environment. A greenhouse study was conducted to evaluate the feasibility of using Vetiveria zizanioides (vetiver) and Phragmities australis (common reed) for the reclamation of Pb/Zn and Cu mine tailings and to evaluate the effects of organic amendments using manure compost (11.00, 22.03, 44.05 and 88.10 t/ha) and sewages sludge (11.00, 22.03, 44.05 and 88.10 t/ha) on the revegetation of these tailings. The results revealed that the applications of manure compost or sewage sludge not only increased N, P and K concentrations, but also decreased DTPA-extractable Pb and Zn contents in Pb/Zn tailings and DTPA-extractable Cu contents in Cu tailings. For Pb/Zn mine tailings, application of sewage sludge increased the yields of both species (highest yield at 44.05 t/ha), but not manure compost. For Cu mine tailings, application of manure compost (highest yield for both species at 44.05 and 22.03 t/ha for vetiver and common reed accordingly) or sewage sludge (highest yield at 22.03 and 44.05 t/ha for vetiver and common reed accordingly) increased the yield of both species. In general, vetiver achieved a higher yield when compared with common reed, under the same treatment. Plant tissue analysis showed that application of manure compost and sewage sludge could significantly reduce Pb uptake and accumulation, but not Cu in both vetiver and common reed.

Arsenic uptake and accumulation in fern species growing at arsenic-contaminated sites of southern China: field surveys

Aiming at searching for new arsenic (As) hyperaccumulators, field surveys were conducted at 12 As-contaminated sites located in Guangxi and Guangdong Provinces of southern China. Samples of 24 fern species belonging to 16 genera and 11 families as well as their associated soils were collected and As concentrations in plant and soil samples were determined by inductively coupled plasma-atomic emission spectrometry (ICP-AES). The results show that among 24 fern species, Pteris multifida and P. oshimensis can (hyper)accumulate As in their fronds with high concentrations in addition to P. vittata and P. cretica var. nervosa, which have been previously identified as As hyperaccumulators. Total As concentrations in soils associated with P. multifida and P. oshimensis varied from 1262 to 47,235 mg kg(-1), but the DTPA-extractable As concentrations were relatively low, with a maximum of 65 mg kg(-1). Forty-four of 49 samples of P. multifida collected from five sites and 3 of 13 samples of P. oshimensis collected from one site accumulated over 1000 mg As kg(-1) in their fronds and As concentrations in the fronds were higher than those in the petioles and rhizoids. Although As concentrations in the fronds of P. oshimensis (789 mg kg(-1) averaged, range 301-2142 mg kg(-1)) were comparatively lower than those of P. multifida (1977 mg kg9-1), 624-4056 mg kg(-1)), its high aboveground biomass makes it more suitable for phytoremediating As-contaminated soils. Among all the species in Pteris genus studied, Pteris semipinnata accumulated only very low As concentration in its fronds (8 mg kg(-1), 1-18 mg kg(-1)). Further research is needed to study the differences in As uptake and accumulation among fern species in the same or other genera.

Interactions of mycorrhizal fungi with Pteris vittata (As hyperaccumulator) in As-contaminated soils

A greenhouse trial was conducted to investigate the role of arbuscular mycorrhizas (AM) in aiding arsenic (As) uptake and tolerance by Pteris vittata (As hyperaccumulator) and Cynodon dactylon (a multi-metal root accumulator). Plants inoculated with lived and killed native mycorrhizas isolated from an As mine site were grown in a sterile and slightly acidic soil. The infectious percentage of mycorrhizas (0 mg/kg As: 26.4%, 50 mg/kg As: 30.3%, 100 mg/kg As: 40.6%) and the average biomass of shoots in infected P. vittata increased (0 mg/kg As: 2.45 g/pot, 50 mg/kg As: 2.48 g/pot, 100 mg/kg As: 10.9 g/pot) according to the increase of As levels when compared to control. The indigenous mycorrhizas enhanced As accumulation (0 mg/kg As: 3.70 mg/kg, 50 mg/kg As: 58.3 mg/kg; 100 mg/kg As: 88.1 mg/kg) in the As mine populations of P. vittata and also sustained its growth by aiding P absorption. For C. dactylon, As was mainly accumulated in mycorrhizal roots and translocation to shoots was inhibited.

Increase of glutathione in mine population of Sedum alfredii: a Zn hyperaccumulator and Pb accumulator

Phytochelatins (PCs) have been induced in a large range of plant species, but their role in heavy metal tolerance is unclear. Sedum alfredii is a new zinc (Zn) hyperaccumulator and lead (Pb) accumulator found in an old Pb/Zn mine in the Zhejiang Province of China. Until now, the mechanisms of its hyperaccumulation/accumulation and tolerance were poorly understood. The aim of this work was to investigate whether PCs were differentially produced in mine populations of S. alfredii compared with a non-mine control of the same species. The results showed that plants from the mine site were more tolerant to increasing Zn and Pb concentrations than those from the control site. No PCs and cysteine (Cys) were detected by pre-column derivatization with HPLC fluorescence in any tissues of two populations at any treatment, which in turn indicated they were not responsible for Zn and Pb tolerance in the mine population. Instead, Zn and Pb treatments resulted in the increase of glutathione (GSH) for both populations in a tissue-dependent manner. Significant increases were observed in leaf, stem and root tissues of plants grown on the mine site. The results suggest that GSH, rather man PCs, may be involved in Zn and Pb transport, hyperaccumulation/accumulation and tolerance in mine population of S. alfredii.