Using Phytoremediation to Clean Up Sites
Phyto-remediation is the direct use of green plants and their associated microorganisms to stabilize or reduce contamination in soils, sludges, sediments, surface water, or ground water. First tested actively at waste sites in the early 1990s, phytoremediation has been tested at more than 200 sites nationwide. Because it is a natural process, phytoremediation can be an effective remediation method at a variety of sites and on numerous contaminants. However, sites with low concentrations of contaminants over large cleanup areas and at shallow depths present especially favorable conditions for phytoremediation. Plant species are selected for use based on factors such as ability to extract or degrade the contaminants of concern, adaptation to local climates, high biomass, depth root structure, compatibility with soils, growth rate, ease of planting and maintenance, and ability to take up large quantities of water through the roots.
Current Research From Around The World
- Heavy metal tolerance and accumulation of Cd, Cr and Ni by Cannabis sativa L.
- Industrial hemp (Cannabis sativa L.) growing on heavy metal contaminated soil: fiber quality and phytoremediation potential
- Industrial Hemp as a Raw Material for Energy Production
- Plant performance, dioxygenase-expressing rhizosphere bacteria, and biodegradation of weathered hydrocarbons in contaminated soil
- Remediation of Benzo[a]pyrene and Chrysene-Contaminated Soil with Industrial Hemp (Cannabis sativa)
- Phytoextraction of lead, zinc and cadmium from soil by selected plan
- Flax (Linum usitatissimum L.) and Hemp (Cannabis sativa L.) as Fibre Crops for Phytoextraction of Heavy Metals: Biological, Agro-technological and Economical Point of Views
- Current status and future scenarios of hemp breeding
Heavy metal tolerance and accumulation of Cd, Cr and Ni by Cannabis sativa L.
Sandra Citterio, Angela Santagostino, Pietro Fumagalli, Nadia Prato, Paolo Ranalli, Sergio Sgorbati
Experiments in semi-natural conditions were undertaken to assess hemp metal tolerance and its ability to accumulate cadmium, nickel and chromium. Cannabis sativa was grown in two soils, S1 and S2, containing 27, 74, 126 and 82, 115, 139 ?g g?1 of Cd, Ni and Cr, respectively. After two months from germination and at ripeness, no significant alteration in plant growth or morphology was detected. On the contrary, a high hemp reactivity to heavy metal stress with an increase in phytochelatin and DNA content was observed during development, suggesting the Cannabis sativaability to avoid cell damage by activating different molecular mechanisms. Metals were preferentially accumulated in the roots and only partially translocated to the above-ground tissues. The mean shoot Cd content was 14 and 66 ?g g?1 for S1 and S2 soil, respectively. Although not negligible concentrations they were about 100 times lower than those calculated for the hyperaccumulator Thlaspi caerulescens. Similarly Ni uptake was limited if compared with that of the Ni-hyperaccumulator Alyssum murale. Chromium uptake was negligible. As expected on the base of the metal concentration detected in ripe plants, no statistically significant variation in soil metal content was detected after one crop of hemp. Nevertheless, a consistent amount (g) of Cd and Ni is expected to be extracted by 1 ha biomass of hemp (about 10 t) per year and along the time a slow restoration of deeper soil portions can be obtained by its wide root system (at least 0,5 m deep). In addition, the possibilities of growing hemp easily in different climates and using its biomass in non-food industries can make heavy metal contaminated soils productive. This means economical advantage along with a better quality of soil.
Industrial hemp (Cannabis sativa L.) growing on heavy metal contaminated soil: fiber quality and phytoremediation potential
P. Lingera, , , J. Müssigb, , , H. Fischerb, J. Koberta
Hemp (Cannabis sativa L.) was used to examine its capability as a renewable resource to decontaminate heavy metal polluted soils. The influence of heavy metals on the fibre quality was of special interest. Determination of heavy metal content was carried out by means of atomic absorption spectroscopy (AAS). Four different parts of the plant were examined: seeds, leaves, fibres and hurds. In each case, the concentration relation was Ni>Pb>Cd. However, the heavy metal accumulation in the different parts of the plant was extremely different. All parts of hemp plants contain heavy metals and this is why their use as a commercially utilisable plant material is limited. We found that the highest concentrations of all examined metals were accumulated in the leaves. In this field trial, hemp showed a phytoremediation potential of 126 g Cd (ha vegetation period)?1. We tested the fibre quality by measuring the pure fibre content of the stems and the fibre properties after mechanical separation. In addition, the fibre fineness was examined using airflow systems and image analysis. The strength was measured by testing single fibre bundles with a free clamping distance of 3.2 mm using a universal testing device. Finally, we compared the results from the stems and fibres from trials on heavy metal polluted ground with hemp stems and fibres from non-polluted ground. Since there was no comparable unpolluted area near the polluted one, reference values were taken from an area quite far away and subsequently with a different soil composition and also exposure to different meteorological conditions. Thus, the observed differences are only partially caused by the heavy metal contamination.
Henryk Burczyka*, Lidia Grabowskaa, Jacek Ko?odzieja & Ma?gorzata Strybea
According to the “strategy for the development of a renewable energy sector” the share of renewable energy in the primarily energy balance in Poland should grow to 7.5% by 2010. The main source of renewable energy will be biomass from annual and perennial energy crops. Since January 1, 2007 Poland has been included in a European Union system of subsidies to energy crop production and hemp will be included in the group of energy crops. In Poland, climate and soil conditions are suitable for hemp cultivation. Currently, there are four cultivars of monoecious hemp registered (Beniko, Bia?obrzeskie, Silesia, and Tygra), yielding 10–15 tons of biomass per hectare. The technologies for hemp cultivation and harvesting are developed. Research conducted at the Institute of Natural Fibres has shown that hemp is a valuable raw material for energy production (its heat of combustion is about 18 MJ/kg). The source of energy is either the whole plant or its shives (75% of yield mass). Trials on producing briquettes from shives, conducted at the INF Experimental Farm at Steszew, were successful and a pilot line for the production of briquettes was installed.
Plant performance, dioxygenase-expressing rhizosphere bacteria, and biodegradation of weathered hydrocarbons in contaminated soil
Hans-Holger Listea, , , Ines Prutzb
Two greenhouse pot experiments were conducted to investigate the potential of 13 plant species (grasses, cruciferes, legumes, herbs) to thrive in a long-term contaminated soil from a former manufactured gas plant (MGP) site, to promote the proliferation of total and aromatic ring dioxygenase-expressing bacteria (ARDB) in the root zone, and to foster the biodegradation of petrol hydrocarbons (PHCs) and polycyclic aromatic hydrocarbons (PAHs). PHCs at 23 200 mg kg?1 and PAHs at 2194 mg kg?1 reduced seed germination, plant survival, and shoot yields for most plants. Total bacteria and ARDB were generally more abundant in contaminated soil and were most numerous in the rhizosphere of mustard. During 68 d, the loss of total petrol hydrocarbons (TPHs) and total US EPA priority PAHs (TPAHs) was greatest in soil planted with hemp and mustard. Pea, cress, and pansy increased the amounts of PAHs extracted from soil, including an almost 60% increase for dibenzo(ah)anthracene. Plants may enhance the chemical extractability and perhaps biological availability of initially unextractable molecules.
Remediation of Benzo[a]pyrene and Chrysene-Contaminated Soil with Industrial Hemp (Cannabis sativa)
Sonia Campbella, Daniel Paquina, Jonathan D. Awayaa & Qing X. Lia
The phytoremediation, with industrial hemp (Cannabis sativa), of a Hawaiian silty clay soil contaminated with two polycyclic aromatic hydrocarbons (PAHs), chrysene and benzo[a]pyrene, was studied. Hemp showed a very high tolerance to the contaminants. The growth rates of hemp, compared with control, in soils fortified with chrysene and benzo[a]pyrene at concentrations of each varying from 25 to 200 ?g/g were consistently above 100%. The plants grew from seed for 45 days in soil fortified with PAHs at concentrations of 25, 50, and 75 ?g/g. Controls were pots with contaminated soil but no plant. PAHs levels were significantly reduced in all pots (control and seeded pots), except for one set at a high concentration of chrysene, which may be due to uneven spiking.
A time course study over 28 days was done to monitor changes of microbial count and levels of chrysene. Little changes were observed for the total microbial count in the soil, and the concentration of chrysene in the soil decreased slightly in the pots containing plants. However, the chrysene levels in those pots were consistently lower than those in the pots without plants.
The Pb, Zn and Cd phytoextraction potential of 14 different plants was assessed in a chelate induced phytoextraction experiment. In the used soil heavy metals mainly reside in carbonate, organic matter, and residual soil fractions. The addition of a chelate, 5 mmol/kg ethylenediamine-tetracetic acid (EDTA), increased the proportion of phytoavailable Pb, Zn and Cd in the soil (dissolved in soil solution and exchangeable from soil colloids), and also their uptake by tested plants up to 48 times (Sinapis alba), 4.6 times (Raphanus sativus oleiformis), and 3.3 times (Amaranthus spp.), respectively, compared to the control. The biodegradable chelate ethylenediamine-disuccinic acid (EDDS) was generally less effective (tested on a selection of 4 plant species), except for Cannabis sativa. In a treatment with 10 mmol/kg EDDS, Pb, Zn and Cd concentrations of 1053 ± 125, 211 ± 16 and 5.4 ± 0.8 mg/kg, respectively, were measured in the biomass of Cannabis sativa and were 105, 2.3 and 31.7 times higher, respectively, than in the control treatment. The calculated Pb phytoextraction potential of Cannabis sativa amounted to 26.3 kg/ha.
Flax (Linum usitatissimum L.) and Hemp (Cannabis sativa L.) as Fibre Crops for Phytoextraction of Heavy Metals: Biological, Agro-technological and Economical Point of View
Miroslav Griga, Marie Bjelková
Fiber crops are world-wide distributed group of plant species belonging taxonomically to various plant families. The common denominator is their use of above-ground biomass for mainly industrial (non-food) or energy purposes. They include approximately 2,000 species—annual and perennial—belonging to monocotyledonous as well as dicotyledonous plants. About 20 species have got an economical (some of them local) importance. Majority of fibre species is grown in tropical and subtropical zones. Cellulose, a natural polymer with high strength and stiffness per weight, is the building material of long fibrous cells, which can be found in the stems, the leaves or the fruits/seeds of fibre plants. Thus, based on the fibrous cells localisation within the plant, we can recognise bast fibre species (e.g. flax, hemp, jute, kenaf, ramie and sida), leaf fibre species (sisal, banana and palm) and fruit/seed fibre species (cotton, coconut, kapok and luffa). During last 20 years, the fibre crops have been also considered as potential candidates for phytoremediation, particularly for phytoextraction of heavy metals from contaminated soils. Within fibre crops of temperate and subtropical zone, flax/linseed and hemp represent economically the most important species and also the majority of heavy metal-related experimental data were obtained and published in these two fibre crops. Here we bring information on biological potential of flax and hemp for heavy metal phytoextraction, the possibilities of agrotechnological treatments to affect/improve heavy metal uptake and, finally, the economical assessment of phytoremediation technology for flax and hemp growers and phytoremediation operators.
Current status and future scenarios of hemp breeding
Hemp is a multi-use crop, able to provide fiber, cellulose, seeds and seed oil, cannabinoid, and biomass. Integrating many agroindustrial chains, Cannabis is considered a crop model in which insights into specific metabolic pathways and biosynthetic processes are valuable for improvement of the plant for all sets of industrial derivatives. In this review the hemp breeding status is elucidated and many aspects are focused: (i) recovering, maintenance and characterization of genetic resources; (ii) widening of germplasm and genetic variability; (iii) marker-assisted selection and development of breeding programs; (iv) sexual differentiation; (v) monitoring of THC content. Modern hemp varieties for fiber and other specific end uses have been developed and new varieties are entering production. The scenario for the breeding advances in hemp relies on basic and applied research which provides insights to identify a strategy for the design of modified plants with enhanced performance. This is accounted by the dissection of traits into components and the modification of single steps of the related metabolic pathways. These advances are provided by genomic techniques and are able: (i) to identify key genes encoding enzymes and regulatory factors participating in cannabinoid, fiber and oil biosynthesis; (ii) to identify the mode of regulation of these genes; (iii) to characterize the function of the selected genes through higher, lower or specific expression incited by specific promoters. The identification of molecular markers for specific traits, gathered in a saturated linkage map, will have a remarkable impact on hemp breeding. The advances in basic and applied research make it possible to design methods for the identification of superior parents and cross combinations and the development of selection schemes that rely on less labour-intensive and time-consuming methods.