Co phytoavailability for tomato in amended calcareous soils

A plot study was conducted to assess changes in Co phytoavailability for a tomato cultivar grown on an agricultural soil (a Calcic Petrocalcid) amended with sewage sludge, under controlled conditions in South-eastern Spain. The experiment consisted of three main treatment blocks: (A) without organic fertilisation, (B) with addition of 60 tha(-1) and (C) 120 tha(-1) of sewage sludge. For each block (A, B, and C), four levels of Co (0, 50, 100 and 200 mgkg(-1)) were added, as CoCl2. Diethylenetriaminepentaacetic acid, DTPA (0.005 M plus triethanolamine), ammonium acetate (1 N at pH 7), and water extractable fractions of the soils were analysed for all the plots. The time dependent Co accumulation in different parts (roots, stems, leaves, and fruits) of the tomato plants was studied. Soil Co seemed to be mainly in non-available forms, according to the low concentrations found in the water and ammonium acetate extracts, compared to DTPA. The gradient of Co accumulation in tomato plants was root > leaf > stem + branches > fruit, with a concentration in the edible parts ranging between 4 and 25 mg kg(-1). The organic amendment enhanced the plant extraction of Co, this effect being more significant with time. Plant extraction efficiency decreased with increasing Co concentration in the soils. Co in fruit showed the best correlation with all the Co extraction pools in the soil.     

Assessing the potential for cadmium phytoremediation with Calamagrostis epigejos: a pot experiment

A pot experiment was conducted for three vegetation periods on a sandy soil (pH 7.5) to study the uptake and distribution of Cd in plant tissues of Calamagrostis epigejos (L.) Roth. Cadmium was applied as CdCl2 (a total of 11 solution of 0, 20. 100, and 200 mg Cd l(-1)). HNO3- and water-extractable concentrations of Cd in 2- and 20-cm soil depths were correlated with the applied Cd showing that Cd was very mobile in the soil. The uptake of Cd from soil by Calamagrostis epigejos was directly related to the total soil Cd content and to the water-soluble pool of Cd. The concentrations of Cd in plant tissues (roots, rhizomes, leaves) and litter increased with increased applied Cd. Most of the Cd that was taken up was accumulated in roots (range from 1.88+/-0.42 to 40.96+/-16.71 mg kg(-1) dry mass), followed by rhizomes (0.52+/-0.13 to 25.70+/-6.35 mg kg(-1)) and leaves (0.30+/-0.06 to 9.20+/-1.93 mg kg(-1)). Cd concentrations of the litter were about twofold greater than the concentrations in the leaves (0.67+/-0.07 to 18.98+/-7.00 mg kg(-1)). The bioaccumulation factor (leaf/soil concentration ratio) increased significantly from 0.70+/-0.10 (control) to 1.1+/-0.17 (100 mg Cd l(-1)), but decreased again at the highest Cd level (200 mg Cd l(-1)) toward 0.74+/-0.34, which was not significantly different from the control. The low transfer of Cd from soil to above-ground organs at higher soil Cd concentrations indicates an exclusion mechanism. The leaf/root Cd concentration ratio (translocation factor) shows no significant relationship to increasing soil contamination. Only 4-7% of the total plant Cd was accumulated in the above-ground tissues. The phytoextraction potential (total Cd removed from soil) within three growing seasons ranged from 0.11 to 0.25% of the total soil Cd. Total output in above-ground living and dead plant material of C. epigejos would be approximately 20 g ha(-1) a(-1) for the lowest contamination level (+20 mg Cd per pot) and approximately 275 g ha(-1) a(-1) for the highest contamination level (+200 mg Cd per pot). This is within the range where an application for phytoextraction of Cd has been suggested by other authors. However, we conclude that the practical use of C. epigejos for phytoremediation is not mainly in the field of phytoextraction, but phytostabilization. C. epigejos has the capability to structurally stabilize the soil and reduce Cd contamination spread due to erosion. The uptake of the available Cd pool and accumulation in below-ground biomass may further prevent leaching into ground water.     

Performance of rose scented geranium (Pelargonium graveolens) in heavy metal polluted soil vis-à-vis phytoaccumulation of metals

An investigation was carried out to evaluate the effect of heavy metal toxicity on growth, herb, oil yield and quality and metal accumulation in rose scented geranium (Pelargonium graveolens) grown in heavy metal enriched soils. Four heavy metals (Cd, Ni, Cr, and Pb) each at two levels (10 and 20 mg kg–1 soil) were tested on geranium. Results indicated that Cr concentration in soil at 20 mg kg–1 reduced leaves, stem and root yield by 70, 83, and 45%, respectively, over control. Root growth was significantly affected in Cr stressed soil. Nickel, Cr, and Cd concentration and accumulation in plant increased with higher application of these metals. Chromium, nickel and cadmium uptake was observed to be higher in leaves than in stem and roots. Essential oil constituents were generally not significantly affected by heavy metals except Pb at 10 and 20 ppm, which significantly increased the content of citronellol and Ni at 20 ppm increased the content of geraniol. Looking in to the higher accumulation of toxic metals by geranium and the minimal impact of heavy metals on quality of essential oil, geranium can be commercially cultivated in heavy metal polluted soil for production of high value essential oil.     

Large-area experiment on uptake of metals by twelve plants growing in soils contaminated with multiple metals

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.     

青葙对土壤锰的耐性和富集特征

通过盆栽试验,研究了青葙(Celosia argentea Linn.)对不同浓度(0、50、100、200、300、500 mg/kg)锰(Mn)污染土壤的吸收和积累特性。结果表明,青葙的锰含量、生物富集系数和生物量均随着土壤锰浓度的增加而增加。当土壤锰含量为300 mg/kg时,青葙生长良好。在锰浓度500 mg/kg时,青葙叶片边缘出现轻微褪绿现象,但是植株的生长未受到抑制,并且叶片生物量显著增加(P0.05)。此时,叶片中锰含量达到最大值42927 mg/kg,生物富集系数为69.20。青葙吸收的锰有95%—97%被转移到地上部分,表明该植物对锰具有很强转运能力。本研究的结果为利用青葙修复锰污染土壤提供了有力证据。     

Hyperaccumulation of metals by Thlaspi caerulescens as affected by root development and Cd-Zn/Ca-Mg interactions

The aim of this work was to study, in a rhizobox experiment, the phytoextraction of metals by the hyperaccumulator plant Thlaspi caerulescens in relation to the heterogeneity of metal pollution. Six treatments were designed with soils containing various levels of metals. Homogeneous soils and inclusions of soils in other soil matrices were prepared in order to vary metal concentration and localization. Growth parameters of the plant (rosette diameter and shoot biomass) and localization of roots and shoot uptake of Zn, Cd, Ca, and Mg were determined after 10 weeks of growth. The plants grown on the polluted industrial soils provided a larger biomass and had lower mortality rates than those grown on the agricultural soil. Moreover, these plants accumulated more Zn and Cd (up to 17,516 and 375 mg kg(-1) DM, respectively) than plants grown on the agricultural soil (up to 7300 mg Zn kg(-1) and 83 mg Cd kg(-1) DM). The roots preferentially explored metal-contaminated areas. The exploration of polluted soil inclusions by the roots was associated with a higher extraction of metals. Zinc and Cd in the shoots of Thlaspi caerulescens were negatively correlated with Ca and Mg concentrations; however, the soil supply for these two elements was identical. This suggests that there is competition for the uptake of these elements and that Zn is preferentially accumulated.     

施硒对两种类型玉米硒元素分配及产量、品质的影响

通过盆栽试验,以普通玉米品种郑单958(ZD958)和糯玉米品种京紫糯218(JN218)为试验材料,研究了不同硒水平(0、10、25、50 mg·kg-1)下,玉米植株各器官对硒的分配和转运差异以及硒对玉米产量和籽粒品质的影响.结果表明： 低含量(≤10 mg·kg-1)硒促进了玉米生长,植株生物量和籽粒产量均显著增加;高含量(≥25 mg·kg-1)硒抑制了玉米生长,植株干物质积累量减少,籽粒产量和品质下降.施硒显著提高了玉米植株各器官的硒含量,硒在各器官的分配为根系>叶片>茎秆>叶鞘,两种类型玉米各器官硒含量均与土壤硒含量呈显著正相关.JN218在自然低硒土壤环境中具有较强的硒富集能力,而ZD958在10 mg·kg-1 硒水平下硒积累量高于JN218.如果以籽粒和地上部营养器官的硒积累量为评价标准,自然低硒(025 mg·kg-1)或高硒(25 mg·kg-1)土壤适宜种植JN218,而富硒(10 mg·kg-1)或硒污染(50 mg·kg-1)土壤适宜种植ZD958.     

四种北方阔叶树种苗木对土壤镉胁迫的生长反应与抗性比较

采用盆栽方法,研究了4种北方阔叶树种茶条槭、山梨、五角槭和山荆子一年生苗木对土壤镉胁迫的生长反应和抗性.采用土壤和风化砂混合物作为栽培基质,设计5种土壤镉浓度梯度处理(对照、10、50、100、200mg·kg^-1).结果表明,低浓度处理(≤50mg·kg^-1)刺激各树种苗木的地径、树高生长,其中茶条槭在10mg·kg^-1处理下地径和苗高增加幅度最大,分别为对照的135.8%和146.0%;随着镉处理浓度的增加,地上部生长量下降,茶条槭在最高浓度处理下,生长量降低最大,地径和苗高仅分别为对照的241%和280%.叶片和新枝生物量变化存在较大种间差异,茶条槭和山梨在低浓度处理时总体上表现增加;山荆子新枝生物量增加,叶生物量减少;五角槭表现一致减少.最高浓度处理时,叶和新枝生物量受影响最大的是茶条槭,分别为对照的4.6%和7.3%;其次为五角槭,分别为对照的5.7%和7.9%;山梨和山荆子受影响的幅度相对较小.新根生物量除山梨外,其它3个树种苗木的生物量表现一致下降,其中下降幅度以茶条槭最大,最高浓度处理仅为对照的2.3%.山梨在低浓度处理下,新根生物量有所增加,分别为对照的125.5%和117.1%.     

外源磷或有机质对板蓝根吸收转运砷的影响

采用土壤培养方法,研究了不同含砷水平土壤中添加外源磷或有机质对砷在板蓝根地下部和地上部累积与分配的影响。结果表明,在外源添加磷或者有机质的情况下,与自然土相比含砷土对板蓝根的生长有一定的促进作用;在自然土(13.4 mg/kg)中,外源磷没有明显影响板蓝根地下部对砷的累积,却显著降低了砷由地下部向地上部的转运,并且添加200 mg P2 O5/kg显著降低了砷在地上部的累积。然而,在含砷土(33.4 mg/kg)中,100 mg P2O5/kg处理显著降低了砷在地下部的累积,但随磷用量的增加反而促进了地下部砷的累积;在添加有机质试验中,10 g/kg的有机质显著降低了自然土中板蓝根地下部和地上部对砷的累积,并且砷的吸收能力也明显下降。在含砷土(23.4 mg/kg)中,添加5 g/kg的有机质不仅降低了砷在板蓝根中的富集,而且降低了其对砷的吸收能力,提高了砷由地下部向地上部的转运,但是随着有机质施用量增至10 g/kg,地下部砷含量及其吸收砷的能力均有一定程度的增大。因此,在砷水平较低的自然土壤上种植板蓝根添加200 mg P2O5/kg和10 g/kg的有机质是控制砷在该草药体内积累的适宜用量,而在砷水平较高的土壤上100 mg P2O5/kg和5 g/kg的有机质是降低板蓝根体内砷累积的适宜用量。     

Effects of soil-plant interactive system on response to exposure to ZnO nanoparticles

The ecotoxicological effects of nanomaterials on animal, plant, and soil microorganisms have been widely investigated; however, the nanotoxic effects of plant-soil interactive systems are still largely unknown. In the present study, the effects of ZnO nanoparticles (NPs) on the soil-plant interactive system were estimated. The growth of plant seedlings in the presence of different concentrations of ZnO NPs within microcosm soil (M) and natural soil (NS) was compared. Changes in dehydrogenase activity (DHA) and soil bacterial community diversity were estimated based on the microcosm with plants (M+P) and microcosm without plants (M-P) in different concentrations of ZnO NPs treatment. The shoot growth of M+P and NS+P was significantly inhibited by 24% and 31.5% relative to the control at a ZnO NPs concentration of 1,000 mg/kg. The DHA levels decreased following increased ZnO NPs concentration. Specifically, these levels were significantly reduced from 100 mg/kg in M-P and only 1,000 mg/kg in M+P. Different clustering groups of M+P and M-P were observed in the principal component analysis (PCA). Therefore, the M-P's soil bacterial population may have more toxic effects at a high dose of ZnO NPs than M+P's. The plant and activation of soil bacteria in the M+P may have a less toxic interactive effect on each of the soil bacterial populations and plant growth by the ZnO NPs attachment or absorption of plant roots surface. The soil-plant interactive system might help decrease the toxic effects of ZnO NPs on the rhizobacteria population.     

Stress indications in copper- and nickel-exposed Scots pine seedlings

Scots pine nursery seedlings were planted in pots, five seedlings per treatment, and placed in an experimental field at the University of Oulu in northern Finland at the beginning of June 1997. Copper and nickel sulphates were mixed with forest mineral soil before seedling planting. The metal levels ranged from 0 to 25 mg Ni kg(-1) dry soil and 0 to 50 mg Cu kg(-1) in dry soil and in combinations of both metals. Current year's needles for element analyses, EDS microanalyses, microscopy and glutathione and peroxidase activity analyses were collected from 1-5 seedlings per treatment in September. Seedling biomass in controls, Cu25 and Cu50 differed significantly from the Ni25Cu50 treatment. The root/shoot ratio was highest in the Ni5 treatment, indicating good root growth, though the roots were visibly healthier in the Cu25 treatment than in the Ni5 treatment. At higher Ni levels, the condition of roots deteriorated. The proportion of plasmolysed mesophyll cells was highest in the Ni25 treatment. Copper-treated seedlings did not suffer from Cu stress, because no severe injuries were seen in either the roots or the needles in Cu-exposed seedlings. The needle concentrations of Cu increased only slightly due to treatments. Ni accumulation in needles increased with increasing concentrations in soil. Needles of Cu-treated seedlings had less oxidized glutathione than those of Ni-treated seedlings, but the roots had higher, not significantly, peroxidase activity levels. Light-colored, swollen thylakoids were occasionally observed in the Ni25Cu50 treatment, indicating some interaction between Ni and Cu. Ni seemed to cause more oxidative stress to the seedlings than copper, which was manifested as a decreased GSH level and an increased proportion of GSSG in the Ni treatments. Copper together with nickel strongly decreased root growth, the root/shoot ratio being lowest in the Ni25Cu50 treatment.     

Phytoextraction of Soil Cobalt Using Hyperaccumulator Plants

A greenhouse study was conducted on phytoextraction of cobalt by nickel hyperaccumulators Alyssum murale and Alyssum corsicum and by two varieties of cobalt accumulator Nyssa sylvatica compared with the nonmetal accumulator crop plant Brassica juncea. The plants were grown on Sassafras sandy loam soil (<2 mg Co and 5 mg Ni/kg dry soil), amended with 1 mmol Co/kg dry soil (58.9 mg/kg), and two Ni smelter-contaminated soils, Quarry muck with 24 mg Co and 1720 mg Ni/kg dry soil and Welland loam with 37 mg Co and 2570 mg Ni/kg dry soil. All soils were adjusted to pH 6.5 to prevent Ni phytotoxicity. Of the five plant entries tested in the study, the two Alyssum species demonstrated the most promising Co phytoextraction results. In Co-amended Sassafras soil, the maximum concentration accumulated by Alyssum murale was 1320 mg Co/kg dry weight, which was almost 60 times higher than accumulation by crop plant Brassica juncea. At a single harvest after 60 days of growth, A. murale was able to extract more than 3% of Co from Co-amended soil. As expected, both Alyssum species accumulated up to 1% Ni on dry weight basis when grown on Ni-contaminated soils.

Nyssa sylvatica showed considerable Co accumulation; foliar Co concentration in the second harvest was as high as 800 mg/kg dry weight. The first few leaves that emerged were chlorotic, both in the Co-amended soil and Ni-contaminated soils, but with growth the signs of toxicity disappeared. In the Co amended soil, Co concentration in Nyssa sylvatica leaves was 30% of that found in shoots of Alyssum species, but an order of magnitude higher than that of Brassica juncea. The leaves accumulated a higher concentration compared with the stems.

Both Alyssum species and Nyssa sylvatica offer promise for phytoextraction of Co and ⁶⁰Co from contaminated or mineralized soils.     

EGTA对Cd胁迫下蓖麻Cd积累和营养元素吸收的影响

以‘淄蓖麻5号’蓖麻品种为材料,通过盆栽试验研究了重度Cd土壤污染（100 mg·kg^-1）条件下,不同浓度（0、0.5、1.0、2.0 mmol·kg^-1）外源螯合剂——乙二醇双(2-氨基乙基醚)四乙酸(EGTA)对蓖麻植株生长、Cd积累和营养元素吸收的影响,探讨外源螯合剂调控Cd污染土壤上植物生长和修复效应。结果显示：（1）在Cd胁迫下,土壤中外源添加0.5~2.0 mmol·kg^-1EGTA使蓖麻根系鲜、干重比不添加EGTA对照不同程度降低,但植株总干重没有受到显著影响。（2）外源EGTA能有效促进Cd从蓖麻根部向地上部的转移,2.0 mmol·kg^-1的EGTA处理使蓖麻叶片Cd 含量显著增加了41.34倍;与不添加EGTA对照相比,外源EGTA处理蓖麻叶片中Cd积累量随添加EGTA的浓度增加而显著大幅度增加14.0~45.6倍,占相应植株总积累量的36.89%~58.63%,而茎中Cd积累量增加幅度较小,根中Cd积累量则显著降低。（3）Cd胁迫条件下,外源EGTA对蓖麻各器官矿质元素含量的影响不一,EGTA促进K向蓖麻地上部的转运,同时抑制Mg向植株地上部转运;随土壤添加的EGTA浓度提高,蓖麻植株对Ca吸收表现为低促高抑,叶片Zn含量和植株Cu含量逐渐增加,叶片和根系Fe含量及植株各器官Mn含量显著增加。与无Cd胁迫对照相比,EGTA在提高植株Cd积累的同时,降低了根系对K的吸收。研究表明,Cd胁迫显著抑制了蓖麻植株的生长,适宜浓度的外源EGTA对Cd的这种抑制有显著的缓解作用;外源EGTA改变了Cd在蓖麻根、茎、叶中的积累分布情况,提高了Cd从根系向地上部,尤其是向叶片的转移能力,从而强化了蓖麻对Cd污染土壤的修复效率;在采用EGTA强化植物修复Cd污染土壤时,应适量增施K肥以保证植株的正常生理代谢。     

Effect of soil cadmium application and pH on growth and cadmium accumulation in roots, leaves and fruit of strawberry plants (Fragaria × ananassa Duch.)

Three strawberry (Fragaria × ananassa Duch.) cultivars Rainier, Totem and Selva were grown under greenhouse conditions in a Parkhill sandy loam soil with a background DTPA-extractable Cd concentration of 0.18 mg kg^-1 and a pH of 5.1. Experimental treatments included combinations of 4 Cd applications (0, 15, 30 and 60 mg Cd kg^-1 soil) applied as CdSO₄ and 2 soil pH values 5.1 and 6.8. Both the application of Cd and pH of the soil significantly affected plant growth, yield and Cd accumulation in plant tissue anf fruit. Although roots accumulated the highest concentrations of Cd of all plant parts investigated, increased soil Cd application reduced leaf weight more than root weight. In general, yield of strawberries was decreased by an increase in amount of soil-applied Cd, however the yield response varied among cultivars. At 60 mg Cd kg^-1 soil, yield of Rainier cultivar was reduced to 17.6% of control plants. Over 90% of total Cd taken up by plants grown in Cd-treated soil accumulated in roots, regardless of the Cd level in the soil. Root Cd concentrations ranged from 2.6 mg kg^-1 (control plants) to 505.7 mg kg^-1 (Totem plants grown in soil at highest Cd and a soil pH 5.1) and were directly related to soil Cd concentrations. Cd translocation from roots to leaves and fruit was very limited, resulting in a maximum Cd concentration in root leaf tissue of 10.2 mg kg^-1. Accumulation of Cd in fruit was found to correlate well with leaf Cd, although even at the highest amount of applied Cd, fruit Cd concentration did not exceed 700 g kg^-1 of fresh weight.Contribution no. 951     

Phytoremediation potential of Pityrogramma calomelanos var. austroamericana and Pteris vittata L. grown at a highly variable arsenic contaminated site

This study examined the phytoextraction potential of two arsenic (As) hyperaccumulators, Pteris vittata L. and Pityrogramma calomelanos var. austroamericana at a historical As-contaminated cattle dip site in northern New South Wales (NSW), Australia. Total As concentration in the surface soil (0-20 cm) showed a better spatial structure than phosphate-extractable As in the surface and sub-surface soil at this site. P. calomelanos var. austroamericana produced greater frond dry biomass (mean = 130 g plant(-1)) than P. vittata (mean = 81 g plant(-1)) after 10 months of growth. Arsenic concentration and uptake in fronds were also significantly higher in P. calomelanos var. austroamericana (means = 887 mg kg(-1) and 124 mg plant(-1)) than in P. vittata (means = 674 mg kg(-1) and 57 mg plant(-1)). Our results showed that under the field conditions and highly variable soil As at the site, P. calomelanos var. austroamericana performed better than P. vittata. We predict that P. calomelanos var. austroamericana would take approximately 100 years to reduce the total As to below 20 mg kg(-1) at the site compared to > or =200 years estimated for P. vittata. However, long-term data are required to confirm these observations under field conditions.     

蚯蚓和秸秆对铜污染土壤微生物类群和活性的影响

试验设置4个Cu浓度水平：0、100、200和400 mg·kg^-1 Cu²⁺,每个Cu浓度水平设置4个处理：对照(CK)、表施秸秆(M)、接种蚯蚓(E)、同时加入蚯蚓和秸秆(ME),研究了在Cu污染土壤中加入蚯蚓和秸秆对土壤微生物数量及活性的影响.结果表明：Cu污染、秸秆和蚯蚓均明显影响土壤微生物类群; Cu污染对细菌、放线菌具有抑制作用,而对真菌没有影响;秸秆显著提高了真菌数量;蚯蚓使土壤细菌、放线菌数量显著增加,而对真菌数量影响不大.Cu污染浓度＞200 mg·kg^-1处理对微生物量碳具有抑制作用;加入秸秆或蚯蚓,可显著提高土壤微生物量碳,而且同时加蚯蚓和秸秆处理土壤微生物量碳增加最显著.加入蚯蚓和秸秆后,土壤呼吸值显著增高.Cu<200 mg·kg^-1时,蚯蚓处理土壤呼吸值最大,平均比对照高3.06～5.58倍;Cu≥200mg·kg^-1时,蚯蚓、秸秆同时加入处理土壤呼吸值最高.4个处理土壤代谢商大小顺序为：ME>E>M>CK.蚯蚓和秸秆处理对土壤NH₄⁺-N没有影响,而对土壤NO₃^--N影响各异.接种蚯蚓,可显著提高土壤NO₃^--N含量;加入秸秆,可显著降低土壤NO₃^--N含量;同时加入蚯蚓和秸秆处理NO₃^--N含量最低.相关分析表明,土壤有效态Cu(DTPA-Cu)与土壤放线菌、细菌呈显著负相关,而与土壤呼吸、土壤NO₃^--N、NH₄⁺-N含量呈显著正相关.引入秸秆和蚯蚓,可在一定程度上减缓Cu污染对微生物数量和活性的影响.     

Effects of soil amendments and EDTA on lead uptake by Chromolaena odorata: greenhouse and field trial experiments

Greenhouse and field trial experiments were performed to evaluate the use of Chromolaena odorata with various soil amendments for phytoextraction of Pb contaminated soil Pb mine soils contain low amount of nutrients, so the additions of organic (cow manure) and inorganic (Osmocote and NH4NO3 and KCl) fertilizers with EDTA were used to enhance plant growth and Pb accumulation. Greenhouse study showed that cow manure decreased available Pb concentrations and resulted in the highest Pb concentration in roots (4660 mg kg(-1)) and shoots (389.2 mg kg(-1)). EDTA increased Pb accumulation in shoots (17-fold) and roots (11-fold) in plants grown in soil with Osmocote with Pb uptake up to 203.5 mg plant(-1). Application of all fertilizers had no significant effects on relative growth rates of C. odorata. Field trial study showed that C. odorata grown in soil with 99545 mg kg(-1) total Pb accumulated up to 3730.2 and 6698.2 mg kg(-1) in shoots and roots, respectively, with the highest phytoextraction coefficient (1.25) and translocation factor (1.18). These results indicated that C. odorata could be used for phytoextraction of Pb contaminated soil. In addition, more effective Pb accumulation could be enhanced by Osmocote fertilizer. However, the use of EDTA in the field should be concerned with their leaching problems.     

Uptake of heavy metals by native species growing in a mining area in Sardinia, Italy: discovering native flora for phytoremediation

This study assessed the distribution and availability of plant uptake of Zn, Pb, and Cd present in an abandoned mine at Ingurtosu, Sardinia (Italy). Geological matrix samples (sediments, tailings, and soil from a nearby pasture site) and samples of the predominant plant species growing on sediments and tailings were collected. Mean values of total Zn, Pb and Cd were respectively (mg kg(-1)) 7400, 1800, and 56 in tailings, 31000, 2900, and 100 in sediments, and 400, 200, and 8 in the pasture soil. The metal concentration values were high even in the mobile fractions evaluated by simplified sequential extraction (Zn 7485-103, Pb 1015-101, Cd 47-4 mg kg(-1)). Predominant native species were identified and analyzed for heavy metal content in various tissues. Among the plant species investigated Inula viscosa, Euphorbia dendroides, and Poa annua showed the highest metal concentration in aboveground biomass (mean average of Zn: 1680, 1020, 1400; Pb: 420, 240, 80; Cd: 28, 7, 19 mg kg(-1), respectively). The above mentioned species and A. donax could be good candidates for a phytoextraction procedure. Cistus salvifolius and Helichrysum italicus generally showed behavior more suitable for a phytostabilizer.     

Nitrogen mineralization and crop uptake of N from decomposing 15N labelled red clover and yellow sweetclover plant fractions of different age

Nitrogen mineralization from 15N labelled red clover (Trifolium pratense L.) and yellow sweetclover (Melilotus officinalis Lam.) plant fractions of three different ages (8-, 14- and 20-week old) was studied in an out-door pot experiment during 8.5 months. Individual plant fractions (leaves/stems/roots/flowers), 23 g dry matter pot-1 (corresponding to 7300 kg ha-1), were incorporated into a sandy soil. The net mineralization of N was measured as 15N recovery in spring wheat (Triticum æstivum L.), perennial ryegrass (Lolium perenne L.) following the wheat and in the soil mineral N pool. Dry matter and N yields of the wheat crop were largest in pots receiving the legume leaf materials and the oldest root fractions. The largest amount of net N mineralized was obtained after application of sweetclover leaves, 381 mg N pot-1 (38% of added N), and a smaller amount was measured from red clover leaves, 215 mg N pot-1 (26% of added N). The N release was much smaller from the stems, being on average 63 mg N pot-1 (15% of added N), with intermediate values obtained from roots, 152 mg N pot-1 (26% of added N). The effects of age of the legume fractions on net N mineralization were more pronounced for sweetclover than for red clover materials. Greater net N release was obtained from sweetclover leaves and roots with inceasing age, but the opposite was valid for stems. At final harvest of the ryegrass, an additional 2.8% of added legume N was mineralized, compared with at wheat harvest. The net N mineralized proportion of added N was significantly related to concentrations of N and cell wall constituents in the plant material. Differences in net N mineralization estimates were generally larger between plant fractions than between materials of different age, implying that leaf proportion of the above-ground biomass is of great importance when predicting net N mineralization from green-manure plant materials. In addition, the contribution from roots to net mineralized legume N could be substantial.     

Iron and phosphorus fertilizations and the development of proteoid roots in macadamia (Macadamia integrifolia)

Proteoid roots are reportedly an adaptation to soils with either low phosphorus (P) or iron (Fe) or both. Since macadamia (Macadamia integrifolia, a member of the family Proteaceae) is an important crop in Hawaii, a factorial experiment with soil P levels of 0, 150, and 500 mg/kg and Fe levels of 0, 5, and 10 mg/kg was conducted to evaluate the effects of P and Fe fertilizations and possible Fe x P interactions on proteoid root development and macadamia growth. The soil was a highly weathered Oxisol having 0.015 mg P/L and 0.03 mg Fe/L in the soil solution in its unamended state. Proteoid roots were reduced in number and as a percentage of the total root mass at the highest levels of P and Fe. Phosphorus, however was a major controlling factor. Optimum dry matter associated with at least 10% proteoid roots, corresponding to a P concentration approximately of 0.035 mg/L in soil solution and 0.10% P in leaves. Total Fe in leaves or the amount of Fe applied was not a good predictor of plant growth. In contrast, chlorophyll content, a surrogate of biologically active Fe, was. Soil-solution ratio of Fe ^1/3/ P (molar basis) could be used to predict the response of macadamia growth to P and Fe fertilizations.