VETIVER GRASS,VETIVERIA ZIZANIOIDES: A CHOICE PLANT FOR PHYTOREMEDIATION OF HEAVY METALS AND ORGANIC WASTES

Glasshouse and field studies showed that Vetiver grass can produce high biomass (>100t/tha^?1 year^?1) and highly tolerate extreme climatic variation such as prolonged drought, flood, submergence and temperatures (?15°–55°C), soils high in acidity and alkalinity (pH 3.3–9.5), high levels of Al (85% saturation percentage), Mn (578 mg kg^?1), soil salinity (ECse 47.5 dS m^?1), sodicity (ESP 48%), and a wide range of heavy metals (As, Cd, Cr, Cu, Hg, Ni, Pb, Se, and Zn). Vetiver can accumulate heavy metals, particularly lead (shoot 0.4% and root 1%) and zinc (shoot and root 1%). The majority of heavy metals are accumulated in roots thus suitable for phytostabilization, and for phytoextraction with addition of chelating agents. Vetiver can also absorb and promote biodegradation of organic wastes (2,4,6-trinitroluene, phenol, ethidium bromide, benzo[a]pyrene, atrazine). Although Vetiver is not as effective as some other species in heavy metal accumulation, very few plants in the literature have a wide range of tolerance to extremely adverse conditions of climate and growing medium (soil, sand, and tailings) combined into one plant as vetiver. All these special characteristics make vetiver a choice plant for phytoremediation of heavy metals and organic wastes.     

PHYTOREMEDIATION POTENTIAL OF MAIZE (ZEA MAYS L.) IN CO-CONTAMINATED SOILS WITH PENTACHLOROPHENOL AND CADMIUM

The ubiquitous coexistence of heavy metals and organic contaminants was increased in the polluted soil and phytoremediation as a remedial technology and management option is recommended to solve the problems of co-contamination. Growth of Zea mays L and pollutant removal ability may be influenced by interactions among mixed pollutants. Pot–culture experiments were conduced to investigate the single and interactive effect of cadmium (Cd) and pentachlorophenol (PCP) on growth of Zea mays L, PCP, and Cd removal from soil. Growth response of Zea mays L is considerably influenced by interaction of Cd and PCP, significantly declining with either Cd or PCP additions. The dissipation of PCP in soils was notably affected by interactions of Cd, PCP, and plant presence or absence. At the Pentachlorophenol in both planted and non-planted soil was greatly decreased at the end of the 10-week culture, accounting for 16–20% of initial extractable concentrations in non-planted soil and 9–14% in planted soil. With the increment of Cd level, residual pentachlorophenol in the planted soil tended to increase. The pentachlorophenol residual in the presence of high concentration of Cd was even higher in the planted soil than that in the non-planted soil.     

GROWTH OF CYMBOPOGON CITRATUS AND VETIVERIA ZIZANIOIDES ON Cu MINE TAILINGS AMENDED WITH CHICKEN MANURE AND MANURE-SOIL MIXTURES: A POT SCALE STUDY

The Rakha Cu mines are located at East Singhbhum, Jharkhand, India and their activities ceased in 2001. The tailings (residue) were permanently stored in tailings ponds that require vegetation to reduce their impact on the environment. A pot scale study was conducted to evaluate the suitability of Cymbopogon citratus (DC.) Ex Nees and Vetiveria zizanioides (L.) Nash for the reclamation of Cu tailings and to evaluate the effects of chicken manure and soil-manure mixtures on the revegetation of such tailings. Application of manure and soil-manure mixtures resulted in significant increase in pH, EC, OC, CEC and nutritional status of Cu tailings. The environmentally available and DTPA extractable Cu and Ni concentration reduced in amended tailings, while Mn and Zn content increased significantly. Plants grown on amended tailings accumulated lesser Cu and Ni but higher Mn and Zn. Plant biomass increased proportionally to manure and soil-manure mixtures application rates. Lemon grass produced more biomass than vetiver grass in either of the amended tailings. From the pot experiment, it can be suggested that application of chicken manure @ 5% (w/w) and in combination with lemon grass, could be a viable option for reclamation (phytostabilization) of toxic tailings.     

PHYTOREMEDIATION OF BTEX HYDROCARBONS: POTENTIAL IMPACTS OF DIURNAL GROUNDWATER FLUCTUATION ON MICROBIAL DEGRADATION

Volatile hydrocarbons have multiple potential fates in phytoremediation. This research investigated the relationship between biodegradation and plant uptake of BTEX compounds in laboratory and field settings. At a phytoremediation site, preliminary studies revealed minimal uptake into trees and enhanced degradation potential in the rhizosphere and in the bulk soil. Increased oxygen transport to the vadose zone caused by diurnal rise and fall of the water table was hypothesized to enhance degradation in the bulk soil. A detailed greenhouse study was then conducted to investigate potential bioremediation impacts using field-site soil and DN34 hybrid poplar trees.

In rhizosphere soils, the contaminated-planted reactor had significantly higher BTEX degrader populations versus the uncontaminated-planted reactor, as was anticipated. The bulk soil in the planted-contaminated reactor had increased degrader populations than the unplanted-contaminated soil or planted-uncontaminated soil, and planting increased degradation throughout the soil profile, not just in the limited volume of rhizosphere soils. Oxygen diffusive and advective transport into reactors was modeled and calculated. Oxygen input in planted reactors was at least 3 to 5 times higher than in unplanted reactors, and increasing oxygen input lead to increased degrader populations in a linear manner. These results combined with the knowledge that high-transpiration trees draw the contaminated groundwater to the capillary fringe and the rhizosphere indicate that phytoremediation can aid microbial degradation via multiple mechanisms: increasing degrader populations, increasing oxygen input via groundwater diurnal fluctuations, and transporting contaminants to the biologically-enriched soil profile.     

CADMIUM ACCUMULATION IN THE ROOTLESS MACROPHYTE WOLFFIA GLOBOSA AND ITS POTENTIAL FOR PHYTOREMEDIATION

Cadmium (Cd) pollution around the world is a serious issue demanding acceptable solutions, one of which is phytoremediation that is both cost-effective and eco-friendly. Removal of Cd from contaminated water using plants with high growth rates and sufficient Cd accumulation abilities could be an appropriate choice. Here, we investigated a potential Cd accumulator, Wolffia, a rootless duckweed with high growth rate. Cd uptake, accumulation, tolerance, and phytofiltration ability by Wolffia globosa were examined. Furthermore, the effects of arsenic (As) on Cd uptake and phytofiltration by W. globosa were also studied. Cd uptake kinetics showed a linear pattern and a hyperbolic pattern without a plateau in lower (0–2 μM) and higher (0–200 μM) Cd concentration ranges, respectively, suggesting rapid Cd uptake by W. globosa. Cd accumulation ability by W. globosa was higher at Cd concentrations < 10 μM than at >10 μM. All the five species of Wolffia exposed to 1 μM Cd for 5 days accumulated > 500 mg Cd kg^?1 DW. Ten gram fresh W. globosa could diminish almost all the Cd (2 μM) in a 200 mL solution. This enormous accumulation ability was mostly due to passive adsorption of Cd by the apoplast. Arsenic had no significant effect on Cd uptake and phytofiltration. The fresh fronds also showed a great As extracting ability. The results indicated that Wolffia is a strong Cd accumulator and has great Cd phytoremediation potential. Therefore, this plant can be used in fresh aquatic environments co-contaminated by low-levels of Cd and As.

Supplemental materials are available for this article. Go to the publisher's online edition of International Journal of Phytoremediation to view the supplemental file.     

EVALUATION OF THREE ORNAMENTAL PLANTS FOR PHYTOREMEDIATION OF PB-CONTAMINED SOIL

Characteristics of accumulation and tolerance of lead (Pb) in Quamolit pennata, Antirrhinum majus L. and Celosia cristata pyramidalis were investigated to identify Pb-accumulating plants. In this study, pot culture experiment was conducted to assess whether these plants are Pb-hyperaccumulators or accumulators. The results indicated that the Pb enrichment factor (concentration in plant/soil) and Pb translocation factor (concentration in shoot/root) of these plants were principally <1 in pot culture and concentration gradient experiments. However, the Pb concentration in Celosia cristata pyramidalis shoots was higher than 1000 mg kg^?1, the threshold concentration for a Pb-hyperaccumulator. Shoot biomass of Celosia cristata pyramidalis had no significantly (p < 0.05) variation compared to the control. Based on these results, only Celosia cristata pyramidalis could be identified as a Pb-accumulator.     

LEAD TOLERANCE AND ACCUMULATION IN PTERIS VITTATA AND PITYROGRAMMA CALOMELANOS,AND THEIR POTENTIAL FOR PHYTOREMEDIATION OF LEAD-CONTAMINATED SOIL

A field survey was conducted to search for Pb accumulation in fern species at Bo Ngam Pb mine, Thailand. Eleven fern species including Pteris vittata accumulated Pb in the range of 23.3–295.6 mg kg^?1 in the aboveground parts. Hydroponic, pot, and field trial experiments were carried out to investigate Pb-accumulation ability in ferns; including P. vittata and the ornamental species, Pityrogramma calomelanos, Nephrolepis exaltata cv. Gracillimum, and N. exaltata cv. Smirha. In hydroponic experiment, Pi. calomelanos accumulated the highest concentration of Pb (root 14161.1 mg kg^?1, frond 402.7 mg kg^?1). The pot study showed that P. vittata, Pi. calomelanos, and N. exaltata cv. Gracillimum grew well when grown in soil Pb at 92900 mg kg^?1. N. exaltata cv. Gracillimum accumulated the highest Pb concentration in the frond (5074 mg kg^?1) and P. vittata accumulated the highest Pb concentration in the root (16257.5 mg kg^?1). All fern species exhibited TF values less than 1 in both hydroponic and pot experiments. When P. vittata and Pi. calomelanos were grown at mine soils for 6 months, P. vittata tolerated higher soil Pb (94584–101405 mg kg^?1) and accumulated more Pb in frond (4829.6 mg kg^?1) and showed TF > 1 after 2 months of growth. These results indicated that P. vittata can be potentially useful for phytoremediation of Pb-contaminated soil.     

PlANT-ASSOCIATED BACTERIA AS TOOLS FOR THE PHYTOREMEDIATION OF OILY NITROGEN-POOR SOILS

The rhizospheres and phyllospheres of peas, beans, tomatoes, and squash raised in a desert sand soil mixed with 0.5% crude oil were rich in oil-utilizing bacteria and accommodated large numbers of free-living diazotrophic bacteria, with potential for hydrocarbon utilization. According to their 16S rRNA-sequences, the cultivable oil-utilizing bacteria were affiliated with the following genera, arranged in decreasing frequency: Bacillus, Ochrobactrum, Enterobacter, Rhodococcus, Arthrobacter, Pontola, Nocardia, and Pseudoxanthomonas. Diazotrophic isolates were affiliated with Rhizobium, Bacillus, Rhodococcus, Leifsonia, Cellulosimicrobium, Stenotrophomonas, Kocuria, Arthrobacter, and Brevibacillus. The crude oil–utilizing and diazotrophic isolates grew, with varying growth intensities, on individual aliphatic (C₈ to C₄₀) and aromatic hydrocarbons, as sole sources of carbon and energy. Quantitative gas liquid chromatographic measurements showed that representative bacterial isolates eliminated pure n-hexadecane, n-decosane, phenanthrene, and crude oil from the surrounding liquid media. Cultivation of oily sand–soil samples with any of the four tested crops led to enhanced oil degradation in that soil, as compared with the degradation in uncultivated oily sand–soil samples.     

IN-SITU SELECTION OF SUITABLE PLANTS FOR THE PHYTOREMEDIATION OF MULTI-METALS–CONTAMINATED SITES IN CENTRAL TAIWAN

Soils contaminated with metals are a serious problem in central Taiwan; 70% of the metals-contaminated soils in Taiwan are distributed there. We used soil turnover and dilution methods to reduce the total concentration of metals in soil, but this technique may be not suitable for other sites because of their shallow soil depths, which were less than 60 cm. Central Taiwan has the largest flower market in Taiwan and we propose that using local flower species to clean up the metals-contaminated soils is a feasible solution. A 1.3-ha area contaminated by multiple metals (As, Cr, Ni, Cu, and Zn) located in central Taiwan was selected for this large-area phytoremediation experiment. According to the Taiwan Environmental Protection Administration project contract, in-situ selection experiments were conducted to select 12 potential species from 33 tested species for further large area experiment. After in-situ planting of 33 species of plants in the contaminated soil for 33 d, bougainvillea and cockscomb showed yellow-colored leaves and withered as the result of the toxicity of metals. Herbaceous plants can accumulate higher concentration of metals and have higher bioconcentration factor in relative to woody plants. Three weighting models of growth condition and the metal-accumulated concentration of plants growing in the site were evaluated and compared. Six woody plants and six herbaceous plants were selected as high potential metal accumulators for a further large-area experiment.     

STABILITY OF ENHANCED YIELD AND METAL UPTAKE BY SUNFLOWER MUTANTS FOR IMPROVED PHYTOREMEDIATION

Plant biomass and metal shoot accumulation are key factors for efficient phytoextraction. In a previous study, chemical mutagenesis has been used to improve the phytoextraction potential of sunflowers. The main goal of the present study was to assess the stability of sunflower mutants with improved biomass and metal accumulation properties in the 3^rd and 4th generations. As compared to control plants, the best M₃ mutants showed the following improvement of metal extraction: Cd 3–5-fold, Zn 4–5-fold, and Pb 3–5-fold. The best M₄ sunflowers also showed enhanced metal extraction: Cd 3–4- fold, Zn 5–7-fold, Pb 6–8-fold and Cr 5–7-fold. The control sunflower inbred line IBL 04, grown directly on the field, accumulated metals in individual organs in the following decreasing order: Cd and Zn: leaves > stem > roots > flower > seeds; Cr: roots > flower > seeds > leaves > stem. The best sunflower mutants showed either higher metal accumulation in shoots or enhanced metal accumulation in roots, suggesting to improved phytoextraction or rhizofiltration efficiency, respectively.     

二龄草鱼肠炎病的研究

本文从细菌学、血清学、鱼体免疫以及药物治疗等几个方面,阐明了点状产气单胞菌是二龄草鱼肠炎病的病原菌。另外还对这种细菌特性及其致病方式进行了讨论,并对该病的诊断提供了方法。     

厦门地区高尔夫球场草种选择与绿化布局的初步探讨

本文就厦门地区高尔夫球场草种选择和绿化问题作了初步探讨。作者认为,厦门地区的自然条件适合暖地型草种的生长,草种应以狗牙根(Cynodon spp.)和结缕草(Zoysia spp.)为主。绿化设计应体现南亚热带滨海风光的植被景观,树种配置以亚热带植物为主,并与引种的树种相结合,注意绿化效果和球场功能的协调统一,做到绿化布局合理,以绿化效果衬托球场草坪的美观。     

几种鱼类细胞对草鱼呼肠孤病毒敏感性的研究

比较研究了鲫鱼异倍体细胞系(CAB-80)、团头鲂尾鳍细胞系(BCC)、大鳞副泥鳅雌核发育单倍体胚胎细胞系(PHG)、草鱼胚胎细胞系(GCE)、草鱼尾鳍细胞系(GCRF-2)、草鱼肾细胞系(GCK-84)及其四个克隆对草鱼呼肠孤病毒(GCRV)的敏感性。证实了这些细胞(PHG除外)在不同程度上对GCRV敏感,其中以GCK-84的敏感性最强。这表明,在体外培养条件下,GCRV并无严格的种族特异性。用经GCK-84传代的病毒感染草鱼种,能复制出典型的出血病症状。用GCK-84检测了病毒在GCK-84、GCRF-2、CAB-80、BCC和PHG中的滴度(TCID_(50/ml)),其值分别为8.24,7.36,2.90,2.15和1.33。4个克隆与肾细胞系对病毒的敏感程度亦不尽相同,其滴度在6.3到9.32之间变化。上述结果对细胞工程抗病育种预示有较大的潜在意义。在电镜下可见GCRV对被感染的细胞造成了严重的破坏。病毒为平均直径58nm的球形颗粒,具有一个高度电子密度的核心,平均直径约为38nm。病毒在细胞中的分布方式有三种:即散布于细胞质中的、呈晶格状包于一膜状结构中的和整齐或不整齐地聚集在一起但无膜包裹的。     

The Mechanism of Nitrate Accumulation in Pakchoi [Brassica Campestris L.ssp. Chinensis(L.)]

Decreased nitrate in vegetables can improve crop nitrogen utilization efficiency and lessen the human health risk caused by the reduction of nitrate to nitrite in vegetables. This paper studied the mechanisms of differences in nitrate accumulation and distribution within organs of two cultivars of pakchoi (Brassica campestris L.ssp. Chinensis (L.) previously screened in hydroponic experiments from 12 cultivars popularly grown in China at present. The two typical cultivars used in this experiment were Shanghaiqing with low nitrate accumulation and Liangbaiye 1 with high nitrate accumulation. There was no significant difference of total nitrate uptake but a significant difference in nitrate content existed between the two cultivars. Compared with Liangbaiye 1, Shanghaiqing showed a significantly higher photosynthetic rate and nitrate reductase activity. Determination of nitrate concentration (activity) in vacuoles with double-barrelled nitrate-selective microelectrodes showed that Shanghaiqing had lower vacuolar nitrate activity than Liangbaiye 1. Two putative nitrate reductase genes, nia1 and nia2, were amplified from the leaf blades of these two cultivars. Nia1 mRNA fragments (887 bp, accession numbers DQ082868 and DQ082869) were amplified using degenerate primer and nia2 mRNA fragment was amplified using one pair of generate primers designed according to DQ001901. Sequence analysis of DQ082868 and DQ082869 both showed 97% and 87% similarity with two nitrate reductase mRNA sequences of Brassica napus, accession numbers D38219 and D38220, respectively. The results of real time PCR to compare the relative expression of the putative nitrate reductase genes (nia1 and nia2) showed that Shanghaiqing had significantly higher expression level than Liangbaiye 1 and nia2 was significantly higher than nia1 in leaf blade and petiole. Both the nitrate reductase activity and the relative expression level of nia1 were in the order of leaf blade > root > petiole, while that of nia2 was leaf blade > petiole > root. There was no statistically significant difference of nitrate activity stored in vacuoles between the different organs of the two cultivars. It can be concluded that Shanghaiqing took up slightly less nitrate, but had significantly higher nitrate reductase activity in cytosol and had a higher relative expression of the putative nitrate reductase genes than Liangbaiye 1; this leads to the fact that Shanghaiqing has a lower nitrate content than Liangbaiye 1.     

Potential of vetiver (vetiveria zizanioides (L.) Nash) for phytoremediation of petroleum hydrocarbon-contaminated soils in Venezuela

Venezuela is one of the largest oil producers in the world. For the rehabilitation of oil-contaminated sites, phytoremediation represents a promising technology whereby plants are used to enhance biodegradation processes in soil. A greenhouse study was conducted to determine the tolerance of vetiver (Vetiveria zizanioides (L.) Nash) to a Venezuelan heavy crude oil in soil. Additionally, the plant's potential for stimulating the biodegradation processes of petroleum hydrocarbons was tested under the application of two fertilizer levels. In the presence of contaminants, biomass and plant height were significantly reduced. As for fertilization, the lower fertilizer level led to higher biomass production. The specific root surface area was reduced under the effects of petroleum. However, vetiver was found to tolerate crude-oil contamination in a concentration of 5% (w/w). Concerning total oil and grease content in soil, no significant decrease under the influence of vetiver was detected when compared to the unplanted control. Thus, there was no evidence of vetiver enhancing the biodegradation of crude oil in soil under the conditions of this trial. However, uses of vetiver grass in relation to petroleum-contaminated soils are promising for amelioration of slightly polluted sites, to allow other species to get established and for erosion control.