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Heavy metal contamination of soils is a major problem worldwide. As a result, arable land polluted with heavy metals is unsuitable for food production. Utility of energy crops which allow the commercial exploitation of these soils by establishing biofuel feedstock production systems can offer a solution. Additionally, plant cultivation offers opportunities for site remediation. Field experiments have been performed on heavy metal contaminated arable soil located in southern Poland, in the vicinity of a former smelting factory. Although heavy metal concentration exceeded standards, the area has been used for agricultural purposes. Experiments involved testing Switchgrass (Panicum virgatum) cultivated with standard NPK fertilizers and commercially available microbial inoculum. Biomass water, macronutrients (N, P, K, Mg, Ca) and heavy metal (Cd, Pb, Zn) content in aboveground plant organs were assessed at the end of two growing seasons. Switchgrass biomass water content was higher after the second year for nearly 40%. Additionally, after the first as well as the second year fertilizers increased it. Magnesium content, essential in chlorophyll biosynthesis, was higher in the first year and additionally more evident in fertilized variants after every year. Heavy metals accumulation in aboveground organs was lower after the second year compare with the first year. Similar trend was observed for Ca and N plant accumulation. However P and K accumulations were higher after the second year of experiment. In conclusion, due to acclimatization, switchgrass reduce heavy metal uptake, what could result in increase of two biogenic elements (P, K) essential in plant growth.
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Agriculture & Forestry, Vol. 63 Issue 1: 69-76, 2017, Podgorica
DOI: 10.17707/AgricultForest.63.1.08
Heavy metal contamination of soils is a major problem worldwide. As a
result, arable land polluted with heavy metals is unsuitable for food production.
Utility of energy crops which allow the commercial exploitation of these soils by
establishing biofuel feedstock production systems can offer a solution.
Additionally, plant cultivation offers opportunities for site remediation.
Field experiments have been performed on heavy metal contaminated
arable soil located in southern Poland, in the vicinity of a former smelting
factory. Although heavy metal concentration exceeded standards, the area has
been used for agricultural purposes. Experiments involved testing Switchgrass
(Panicum virgatum) cultivated with standard NPK fertilizers and commercially
available microbial inoculum. Biomass water, macronutrients (N, P, K, Mg, Ca)
and heavy metal (Cd, Pb, Zn) content in aboveground plant organs were assessed
at the end of two growing seasons.
Switchgrass biomass water content was higher after the second year for
nearly 40%. Additionally, after the first as well as the second year fertilizers
increased it. Magnesium content, essential in chlorophyll biosynthesis, was
higher in the first year and additionally more evident in fertilized variants after
every year. Heavy metals accumulation in aboveground organs was lower after
the second year compare with the first year. Similar trend was observed for Ca
and N plant accumulation. However P and K accumulations were higher after the
second year of experiment.
In conclusion, due to acclimatization, switchgrass reduce heavy metal
uptake, what could result in increase of two biogenic elements (P, K) essential in
plant growth.
Keywords: Switchgrass, Heavy metals, Macronutrients, Inoculum,
Biomass composition.
Heavy industry (i.e., smelters, coal mine) is main emitter of heavy metals
(HMs) to the environment. The most dangerous directly for human health is
spreading HMs to vicinity agricultural areas where it can be introduce to food
Marta Pogrzeba (corresponding author:, Szymon Rusinowski, Jacek
Kryżak Institute for Ecology of Industrial Areas, Katowice, POLAND
Paper presented at the 7th International Scientific Agricultural Symposium "AGROSYM 2016".
Notes: The authors declare that they have no conflicts of interest. Authorship Form signed online.
Pogrzeba et al.
chain by accumulation in consumed plant organs (Järup, 2003). Such
contaminated arable lands should be excluded from agricultural production. The
alternative for such production can be establishing biofuel feedstock production
systems on those areas. Except biomass production for energy purposes there is
additional benefit in those land management what protect soil from erosion
(Meerset al., 2010). Mineral macro- and micronutrients are essential in plant
development and proper growth of plants is undeniable depends on its content in
soil. Mineral macronutrients are need for plants in higher amount in comparison
to micronutrients. Mineral macronutrients can be divided in to two groups:
primary mineral macronutrients (N, P, K) and secondary mineral macronutrients
(Ca, Mg, Fe, S) (Tripathi et al., 2014). There are reports indicates negative
impact of HM on macronutrients accumulation in above ground organs in
agricultural plant as well as in plant cultivated for medical purposes (Bello et al.,
2004, Siedlecka, 2014). There is a dearth of papers concerning on macronutrients
status in energy crop cultivated HMs contaminated soils. Panicum virgatum
(Switchgrass) is C4 photosynthesis perennial grass belongs to second generation
energy crops, however it can be also cultivated for feed purposes. It is originated
from prairie of Northern America where it is dominant species. Switchgrass due
to those features is plant very resistant to drought conditions (Parrish and Fike,
The aim of the study was to describe relationships in HMs and mineral
macronutrients accumulation in fertilized Switchgrass during two growing season
(2014 and 2015) after plantation establishment. Plants were treated with standard
NPK fertilizer and commercial available microbial inoculum (EmFarma,
Probiotics Magdalena Górska, Poland).
Site description
The trial was established in Bytom (Upper Silesia Region, 50°20'43.0"N
18°57'19.6"E, Poland) on arable land contaminated with HMs. Soil was
contaminated over the last century due to dust fall with HMs deposition (Zn, Cd
and Pb) emitted by already non-existent Zn/Pb smelter. The climate conditions at
the site are moderate, with monthly average temperature and precipitation
presented in Figure 1 (based on Institute of Meteorology and Water Management
data). Experiment design
Switchgrass plots were established at the beginning of May 2014 from the
seedlings obtained from seeds, pre-cultivated in growing room. On each of the
three plots 49 plants were planted with density of 3plants per 1 m2. Due to high
soil homogeneity (Tab. 1) and apprehension of uncontrolled fertilizer application
pseudo-replication were performed. On each plot four section were distinguish
(Fig. 2): edge plants excluded from further analysis(i) and three section (pseudo-
replication) from which samples were taken(ii). Each plot was treated in a
different way and 4 meter buffer zone between each experimental plot was set:
Macroelements and heavy metals content in Panicum virgatum cultivated on …
P - C - control (no treatment);
P - NPK - NPK standard fertilization, applied directly to the soil once before
planting (nitrogen 70 kg ha-1, phosphorus 30 kg ha-1 as P2O5 and potassium 45 kg
ha-1 as K2O);
P - INC - commercial microbial inoculum (EmFarma, ProBioticsPolska
Magdalena Górska, Poland) applied on seedlings roots before plantation and on
the leaves as aerosol in the middle of every month during the growing seasons
(from May to September 2014 and 2015).
Initial soil samples were collected before planting, one from each plot sections.
The plant samples for HMs and mineral macronutrients analysis were collected
in the middle of October each year: one sample were collected from the middle
plot section and two samples were collected from upper and down plot section.
Figure 1. Meteorological data for growing seasons 2014-2015
Soil and plant samples analysis
Soil pH was measured in H2O (1:2.5 m/v) with a combination
glass/calomel electrode (OSH 10-10, METRON, Poland) and a pH-meter (CPC-
551, Elmetron, Poland) at 20°C.
The conductivity was determined by an ESP 2ZM electrode (EUROSENSOR,
Poland) according to the Polish norm PN-ISO 11265:1997.
Soil texture was evaluated by the hydrometric method according to the
Polish norm PN-R-04032:1998.
The total content of metals in the soil and plant tissues was obtained using
hot plate digestion (HNO3 and HClO3, ratio 4:1) and flame atomic absorption
spectrometry (SpektrAA 300, Varian INC., USA).
Total nitrogen content (N) in plant (PB.06 edition 1 from 2011.09.01) and soil
(ISO 13878:1998), available phosphorus (P) in plant (PB.03 edition 1 from
2011.09.01) and soil (PN-R-04023:1996) as well as potassium (K) content in
Pogrzeba et al.
plant (PB.01 edition 1 from 2011.09.01) and soil (PN-R-04022:1996) samples
was assessed in Institute for Ecology of Industrial Areas laboratory.
Soil organic matter (OM) was measured by loss on ignition as follows: air
dry soil was sifted to pass a 2 mm sieve, dried at 105°C for 24 h and then (5 g)
treated with 550°C for 4 h. Soil organic carbon (C-org) was assessed according to
PN-ISO 14235:2003.
Figure 2. Section on plot distinguished for sample collection. Red - section
excluded from sampling, green section where two samples were collected,
yellow section where one sample was collected
Statistical analysis
Data were analyzed using a one-way ANOVA, followed by a post hoc
comparison using the Fisher LSD test (P < 0.05). Statistical analyses were
performed using Statistica 10 (Statsoft, USA). Spider charts were constructed
using Excel MS Office (Microsoft, USA) and standardization of data for charts
construction were performed using Statistica 10 Software (Statsoft, USA).
Results of soil analyses indicate that among experimental plots there were
no significant differences between measured parameter, except Zn (Tab. 1). Soil
Zn content was slightly higher on P INC plot when compare to control. There
were no significant differences between P NPK plot and P INC plot. Soil
texture on the experimental field was classified as silty loam. According to
obtained results and regulation of Polish law (D.2002. r.165 poz.1369) soil HMs
content exceed the limits defined by government regulation. In this case
experimental area should be classified as marginal, moreover whole agriculture
production should be abandoned (Gopalakrishnan et al., 2011). Spider charts
(Fig. 3) were used as a tool for assess values pattern changes of measured
parameters in above ground organs of Switchgrass among different treatments, as
well as annual changes for two growing seasons (2014 and 2015). Spider charts
can be divided in to three representative sections: water with secondary
Macroelements and heavy metals content in Panicum virgatum cultivated on …
macronutrient content (Ca, Mg) (1), primary macronutrients content (N, P, K) (2)
and HMs content (Zn, Cd, Pb) (3). Overall, the highest HMs accumulation in
above ground organs were found for control plants and it was conditioned by Cd
accumulation in the first growing season. The lowest values of Mg and Ca for
control plants could be associated with that highest HMs uptake. Hermans et al.
(2011) reported that in Arabidopsis thaliana old leaves the content of Cd was
lower forplants treated with Cd and Mg, when compare to plant treated only with
Cd. It can be assumed with agreement to presented results that higher Mg content
can reduce Cd accumulation in elder plants. It is well known that magnesium
plays significant role in chlorophyll biosynthesis due to this is essential for
photosynthesis process (Cakmak, 2014). Other measured parameters were equal
among each treatment in the first growing season. In the second growing season
it was found, that there is similar trend among treatments for Mg and Ca
accumulation, however it was found that those parameter values are lower when
compare to the second growing season.
Table 1. Soil physico-chemical characteristic, heavy metal content and
macronutrients content in initial soil samples
Soil physico-chemical characteristic
pH (H2O)
pH (KCl)
EC (µS cm-3)
OM (%)
C-org (%)
6.49 ± 0.03a
5.97 ± 0.05a
89.92 ± 1.41a
5.39 ± 0.02a
2.18 ± 0.03a
6.57 ± 0.04a
6.06 ± 0.07a
82.28 ± 2.80a
5.52 ± 0.06a
2.11 ± 0.03a
6.57 ± 0.03a
6.12 ± 0.02a
89.33 ± 2.89a
5.44 ± 0.06a
2.10 ± 0.01a
Soil heavy metals content
Pb (mg kg-1)
Cd (mg kg-1)
Zn (mg kg-1)
514.77 ± 14.26a
17.94 ± 0.05a
1659.50 ± 7.22b
487.30 ± 3.18a
18.06 ± 0.05a
1700.00 ± 6.35ab
496.50 ± 4.33a
18.02 ± 0.11a
1750.33 ± 34.04a
Soil primary mineral macronutrients content
Ntotal (%)
P (mg kg-1)
K (mg kg-1)
0.15 ± 0.00a
834.30 ± 6.64a
950.30 ± 17.32a
0.15 ± 0.00a
833.20 ± 8.66a
970.60 ± 1.15a
0.15 ± 0.00a
835.87 ± 15.90a
1014.27 ± 24.62a
Soil secondary mineral macronutrients content
Fe (mg kg-1)
Mg (mg kg-1)
Ca (mg kg-1)
9854.50 ± 44.74a
1557.00 ± 30.60a
3015.00 ± 49.07a
10135.00 ± 13.28a
1592.00 ± 4.04a
2998.50 ± 3.17a
10219.00 ± 164.93a
1669.33 ± 51.49a
3185.17 ± 98.48a
P Panicum virgatum, C control plot; NPK NPK fertilized plot, INC
microbial inoculated plot. Values are means ± SE (n=3). A lower case letters (a,
b, c, d) denotes significant differences among soils samples taken from different
plots at P ≤ 0.05 according to Fisher LSD test.
Pogrzeba et al.
Figure 3. Spider charts constructed on macronutrients, heavy metals and water
content show patterns indicated changes of those parameters; among treatment
(C control, NPK NPK fertilizer treated plant, INC microbial inoculum
treated plant) and growing season (a-2014 and b-2015) for Panicum virgatum(P).
Mg, Ca, P, K, N, Pb, Cd, Zn elements accumulation in above ground plants
organs. For better data visualization all presented values were standardized. Each
measurement was performed in 5 replicate (n = 5)
It also has been found that there is overall decrease in accumulation of
HMs and N for plants from each plot, except Cd accumulation in NPK treated
plants when compare to the first growing season. Increased K concentration in
plant samples was found for each variant and P was found to be increased on
each plot treated with fertilizer, when compare to the first growing season.
Gonçalves et al. (2009) reported, that higher Cd concentration in hydroponic
solution can decrease K uptake to above ground organs. This paper is with
agreement with obtained results, however the tendency is only contrary to NPK
treated plants. Water content in plant stems was 40% higher for plant in the
Macroelements and heavy metals content in Panicum virgatum cultivated on …
growing season 2015 when compare to the growing season 2014 and treatments
slightly increased it. This phenomena can be associated with ability to water
capture, which is correlated to root distribution. It is known that perennial grasses
root system become fully developed after 4th growing season (Ferchaud et al.,
2015). In this case water content could be increased due to annual increase of
roots density. Spider charts with description corresponds to overall annual and
treatment changes in biomass HMs, water and mineral macronutrient content. Its
allows to track changes in tendencies while detailed statistical analysis for
measured parameters is presented in Table 2.
Table 2. Matrix of statistical significant differences among analyzed parameters
presented on spider charts (Fig. 2)
Water content
P Panicum virgatum, C control; NPK NPK fertilized plants, INC
microbial inoculated plants.
A lower case letters (a, b, c, d, e, f where “a” corresponds to the highest value
and “f” to the lowest) denotes significant differences among plants elements and
water content taken from different plots at P ≤ 0.05 according to Fisher LSD test.
Each measurement was performed in 5 replicate (n = 5)
It could be concluded that HMs in soil affect mineral macronutrients status
in Panicum virgatum, especially Mg and K. Additionally there are differences
mostly in each measured parameters when compare growing seasons. It can be
associated with acclimatization of plant to contaminated site. There is a dearth of
papers concerning mineral nutrients as well as HMs status in the first two years
after establishment, because most of them are focused on fully establishment
trials, where perennial energy crops achieves its maturity after 3rd -4th year after
Research financed by the PHYTO2ENERGY project 7FP EU, Grant
Agreement No. 610797 and IETU statutory funds by Polish Ministry of Science
and Higher Education.
Pogrzeba et al.
The authors wish to extend their appreciation to dr Włodzimierz
Majtkowski from Plant Breeding and Acclimatization Institute, National
Research Institute (Poland), for providing seeds of Panicum virgatum.
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Ground Standards (in Polish).
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distribution of different perennial and annual bioenergy crops. Plant and Soil, 388,
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Rossato, L. V., Bisognin, D. A., Dressler, V. L., de Moraes Flores, E. M.,
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("elemental analysis")
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... It can be grown on light or moderately heavy saline or alkaline soils with full, mature yields being reached 3 years after planting. It is emphasised that P. virgatum can be used as a productive species in the reclamation and stabilisation of contaminated sites as well as for the bioaccumulation of heavy metals and energy production (Pogrzeba et al. 2017b). P. virgatum, like Miscanthus, has the ability to collect and store large amounts of carbon in below-ground biomass and to produce large quantities of above-ground harvestable biomass with minimal agricultural inputs (Dohleman et al. 2012). ...
... Only a few investigations focused on this element, among which only one was performed in field conditions (for P. arundinacea where As levels exceeded 7 mg kg −1 (Lord 2015). Among the studies we reviewed, the highest concentration of Pb in plant biomass was found for P. virgatum (Pogrzeba et al. 2017b;Aderholt et al. 2017;Gleeson 2007) and the lowest for S. hermaphrodita (Kocoń and Jurga 2017;Antonkiewicz et al. 2006;Pogrzeba et al. 2018a;Rusinowski et al. 2018). For P. virgatum, the highest value of Pb concentration among reports was 210 mg kg −1 DM (Gleeson 2007), while the highest value for S. hermaphrodita was 6.4 mg kg −1 (Antonkiewicz et al. 2006), though other studies on this species (Kocoń and Jurga 2017;Pogrzeba et al. 2018a;Rusinowski et al. 2018) have shown results below 1 mg kg −1 DM. ...
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... Miscanthus giganteus can be used for phytomanagement of polluted sites, restoring ecosystem services [35] with a significant removal of PTEs in the harvestable aerial biomass [36,37]. Pogrzeba et al. [38] reported that P. virgatum may be considered a promising crop for reclamation and energy production in contaminated sites. As reported by Antonkiewicz and colleagues [36], both Miscanthus giganteus and Phalaris arundinacea (canary reed grass) can be very efficient in uptaking bioavailable PTEs from municipal sludge, meaning that phytoextraction systems including such crops can allow agronomic use of potentially toxic sludge, recycling nutrients and immobilizing PTEs in above-ground plant tissues. ...
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Switchgrass (Panicum virgatum L.)—a perennial, warm-season (C4) species—evolved across North America into multiple, divergent populations. The resulting natural variation within the species presents considerable morphological diversity and a wide range of adaptation. The species was adopted as a crop—initially as a forage—only in the last 50 yr. Its potential uses have recently been expanded to include biofuels. Management of switchgrass for biofuels is informed by an understanding of the plant's biology. Successful establishment requires attention to seed dormancy and weed control as well as proper depth and date of planting. The plant's growth rate is closely tied to temperature, but timing of reproductive development is linked to photoperiod. Accordingly, the period of vegetative growth can be extended by planting lower-latitude cultivars at higher latitudes. This strategy may provide a yield advantage, but cold tolerance can become limiting. Switchgrass is thrifty in its use of applied N; it appears able to obtain N from sources that other crops cannot tap. The N removed in harvested biomass is often greater than the amount of N applied. In areas with sufficient rainfall, sustainable yields of ∼15 Mg ha yr may be achievable by applying ∼50 kg N ha yr. Harvesting biomass once per season—after plants have senesced and translocated N into perennial tissues—appears to allow plants to maintain an internal N reserve. Two harvests yr may increase yields in some cultivars, but a single annual harvest maximizes yields in many cases. If two harvests are taken, more N must be applied to compensate for the N removed in the midseason harvest. Taking more than two harvests yr often adversely affects long-term productivity and persistence. Switchgrass has potential as a renewable fuel source, but such use will likely require large infrastructural changes; and, even at maximum output, such systems could not provide the energy currently being derived from fossil fuels.
Macronutrients play very important role in plant growth and development. Their functions range from being structural units to redox sensitive agents. Generally, an application of macronutrient increases yield, growth and quality of crops. In the recent years, however, plant physiologists, biotechnologists and eco-physiologists are working to investigate various other blind features of these minerals and their future prospective because nutrients are involved in every step of plant life. Every macronutrient has its own character, and therefore it involves in different metabolic process of plant life. Herein this chapter deals with the recent progress made in finding out the roles of macronutrients in plant growth and acclimation process as well as future prospective of elemental research in plants.
The concentration levels (ppm) of selected toxic trace metals (Fe, Mn, Cu, Pb and Zn) and macronutrients (Na, K, Mg and Ca), along with P, were estimated in some of the important herbal plants of the southwest part of Nigeria. The atomic absorption spectrophotometer was employed for the estimation conducted on 10 plant species collected from different locations within Ogbomoso. The plants were Anacardium occidentale, Azadirachta indica, Butyrospermum paradoxum, Mangifera indica, Morinda lucida, Ocimum canum, Solanum erianthum, Solanum torvum, Zingiber officinale and Hyptis suaveolens. The metal contents in the samples were found at different levels. The highest mean levels (ppm) of Zn (35.1±0.01) and Cu (24.4±0.01) were found in Hyptis suaveolens while those of Mn (685±0.02) and Ca (51 340±21) were found in Morinda lucida. The result also showed that Ocimum canum had the highest amounts of K (36 600±350), P (3700±35) and Fe (241±0.05). Anacardium occidentale had the highest concentration of Na (613±0.60) while Azadirachta indica had the highest mean concentrations of Pb (0.49±0.03) and Mg (5630±12).
To achieve food and energy security, sustainable bioenergy has become an important goal for many countries. The use of marginal lands to produce energy crops is one strategy for achieving this goal, but what is marginal land? Current definitions generally focus on a single criterion, primarily agroeconomic profitability. Herein, we present a framework that incorporates multiple criteria including profitability of current land use, soil health indicators (erosion, flooding, drainage, or high slopes), and environmental degradation resulting from contamination of surface water or groundwater resources. We tested this framework for classifying marginal land in the state of Nebraska and estimated the potential for using marginal land to produce biofuel crops. Our results indicate that approximately 1.6 million ha, or 4 million acres, of land (approximately 8% of total land area) could be classified as marginal on the basis of at least two criteria. Second-generation lignocellulosic bioenergy crops such as switchgrass ( Panicum virgatum L.), miscanthus (Miscanthus giganteus), native prairie grasses, and short-rotation woody crops could be grown on this land in redesigned landscapes that meet energy and environmental needs, without significant impacts on food or feed production. Calculating tradeoffs between the economics of redesigned landscapes and current practices at the field scale is the next step for determining functional designs for integrating biofuel feedstock production into current land management practices.
In a transcriptomic study of magnesium (Mg) starvation in Arabidopsis, we identified several genes that were differentially regulated which are involved in the detoxification process of nonessential heavy metals such as cadmium (Cd). We further tested the impact of low Mg status on Cd sensitivity in plants. Interestingly, a -Mg pretreatment of 7 d alleviated the bleaching of young leaves caused by Cd. No or little difference in Cd tissue concentration between the +Mg and -Mg plants was observed, suggesting that lower Cd toxicity was probably not attributable to modified root to shoot translocation. Mg deficiency also promoted an increase in the iron (Fe) concentration (up to one-fourth) in Cd-treated leaves. Because high Fe concentrations have previously been reported to prevent the harmful effects of Cd, we explored whether Fe homeostasis plays a role in the Mg-Cd interaction. A protective effect of -Mg pretreatment was also observed on Fe starvation. However, Fe foliar spray partially alleviated Cd-induced chloroses, while it almost completely restored chlorophyll content in Fe-deficient leaves. In conclusion, the protective effect of Mg against Cd toxicity could be attributable partly to the maintenance of Fe status but also to the increase in antioxidative capacity, detoxification and/or protection of the photosynthetic apparatus.
Worldwide there are numerous regions where conventional agriculture is affected by the presence of elevated amounts of plant-available trace elements, causing economic losses and food and feed quality and safety. The Belgian and Dutch Campine regions are a first-class example, with approximately 700 km(2) diffusely contaminated by historic atmospheric deposition of Cd, Zn and Pb. Primary land use in this region is agriculture, which is frequently confronted with crops exceeding the European standards for heavy metal contents in food and feed-stuffs. Phytoremediation as a soil remediation technology only appears feasible if the produced biomass might be valorised in some manner. In the current case, we propose the use of energy maize aiming at risk-reduction and generation of an alternative income for agriculture, yet in the long run also a gradual reduction of the pollution levels. Since the remediation aspect is demoted to a secondary objective with sustainable risk-based land use as first objective, we introduce the term 'phytoattenuation': this is in analogy with 'natural attenuation' of organic pollutants in soils where also no direct intended remediation measures but a risk-based management approach is implemented. In the current field experiment, cultivation of energy maize could result in 33,000-46,000 kW h of renewable energy (electrical and thermal) per hectare per year which by substitution of fossil energy would imply a reduction of up to 21 x 10(3)kg ha(-1) y(-1) CO(2) if used to substitute a coal fed power plant. Metal removal is very low for Cd and Pb but more significant for Zn with an annual reduction of 0.4-0.7 mgkg(-1) in the top soil layer.
In order to evaluate the effect of cadmium (Cd(2+)) toxicity on mineral nutrient accumulation in potato (Solanum tuberosum L.), two cultivars named Asterix and Macaca were cultivated both in vitro and in hydroponic experiments under increasing levels of Cd(2+) (0, 100, 200, 300, 400 and 500 microM in vitro and 0, 50, 100, 150 and 200 microM in hydroponic culture). At 22 and 7 days of exposure to Cd(2+), for the in vitro and hydroponic experiment, respectively, the plantlets were separated into roots and shoot, which were analyzed for biomass as well as Cd(2+), and macro (Ca(2+), K(+) and Mg(2+)) and micronutrient (Cu(2+), Fe(2+), Mn(2+) and Zn(2+)) contents. In the hydroponic experiment, there was no reduction in shoot and root dry weight for any Cd(2+) level, regardless of the potato cultivar. In contrast, in the in vitro experiment, there was an increase in biomass at low Cd(2+) levels, while higher Cd(2+) levels caused a decrease. In general, Cd(2+) decreased the macronutrient and micronutrient contents in the in vitro cultured plantlets in both roots and shoot of cultivars. In contrast, the macronutrient and micronutrient contents in the hydroponically grown plantlets were generally not affected by Cd(2+). Our data suggest that the influence of Cd(2+) on nutrient content in potato was related to the level of Cd(2+) in the substrate, potato cultivar, plant organ, essential element, growth medium and exposure time.
The main threats to human health from heavy metals are associated with exposure to lead, cadmium, mercury and arsenic. These metals have been extensively studied and their effects on human health regularly reviewed by international bodies such as the WHO. Heavy metals have been used by humans for thousands of years. Although several adverse health effects of heavy metals have been known for a long time, exposure to heavy metals continues, and is even increasing in some parts of the world, in particular in less developed countries, though emissions have declined in most developed countries over the last 100 years. Cadmium compounds are currently mainly used in re-chargeable nickel-cadmium batteries. Cadmium emissions have increased dramatically during the 20th century, one reason being that cadmium-containing products are rarely re-cycled, but often dumped together with household waste. Cigarette smoking is a major source of cadmium exposure. In non-smokers, food is the most important source of cadmium exposure. Recent data indicate that adverse health effects of cadmium exposure may occur at lower exposure levels than previously anticipated, primarily in the form of kidney damage but possibly also bone effects and fractures. Many individuals in Europe already exceed these exposure levels and the margin is very narrow for large groups. Therefore, measures should be taken to reduce cadmium exposure in the general population in order to minimize the risk of adverse health effects. The general population is primarily exposed to mercury via food, fish being a major source of methyl mercury exposure, and dental amalgam. The general population does not face a significant health risk from methyl mercury, although certain groups with high fish consumption may attain blood levels associated with a low risk of neurological damage to adults. Since there is a risk to the fetus in particular, pregnant women should avoid a high intake of certain fish, such as shark, swordfish and tuna; fish (such as pike, walleye and bass) taken from polluted fresh waters should especially be avoided. There has been a debate on the safety of dental amalgams and claims have been made that mercury from amalgam may cause a variety of diseases. However, there are no studies so far that have been able to show any associations between amalgam fillings and ill health. The general population is exposed to lead from air and food in roughly equal proportions. During the last century, lead emissions to ambient air have caused considerable pollution, mainly due to lead emissions from petrol. Children are particularly susceptible to lead exposure due to high gastrointestinal uptake and the permeable blood-brain barrier. Blood levels in children should be reduced below the levels so far considered acceptable, recent data indicating that there may be neurotoxic effects of lead at lower levels of exposure than previously anticipated. Although lead in petrol has dramatically decreased over the last decades, thereby reducing environmental exposure, phasing out any remaining uses of lead additives in motor fuels should be encouraged. The use of lead-based paints should be abandoned, and lead should not be used in food containers. In particular, the public should be aware of glazed food containers, which may leach lead into food. Exposure to arsenic is mainly via intake of food and drinking water, food being the most important source in most populations. Long-term exposure to arsenic in drinking-water is mainly related to increased risks of skin cancer, but also some other cancers, as well as other skin lesions such as hyperkeratosis and pigmentation changes. Occupational exposure to arsenic, primarily by inhalation, is causally associated with lung cancer. Clear exposure-response relationships and high risks have been observed.