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Industrial Hemp (Cannabis sativa L.) Growing on Heavy Metal Contaminated Soil: Fibre Quality and Phytoremediation Potential

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  • Faserinstitut Bremen

Abstract and Figures

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.
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Industrial Crops and Products 16 (2002) 3342
Industrial hemp (Cannabis sati6aL.) growing on heavy
metal contaminated soil: fibre quality and phytoremediation
potential
P. Linger
a,
*, J. Mu¨ssig
b,
*, H. Fischer
b
, J. Kobert
a
a
Department
9
Chemistry,Physiological Chemistry of Plants,Uni6ersity of Wuppertal,Gauss Str.
20
,
42097
Wuppertal,Germany
b
Faserinstitut Bremen e.V., FIBRE,PO Box
10 58 07
,
28058
Bremen,Germany
Accepted 19 December 2001
Abstract
Hemp (Cannabis sati6aL.) 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. © 2002 Elsevier Science
B.V. All rights reserved.
Keywords
:
Cannabis sati6aL.; Fibre quality; Fibre bundle; strength; fineness; Optical fibre fineness analyzer; Airflow; Phytoremedi-
ation; Phytoextraction
www.elsevier.com/locate/indcrop
1. Introduction
In the future, we will have to deal with the
problem that increasing numbers of agriculturally
used areas will be contaminated by anthropo-
* Corresponding authors. Tel.: +49-202-439-2820; fax: +
49-202-439-3142.
E-mail addresses
:
linger@uni-wuppertal.de (P. Linger),
muessig@faserinstitut.de (J. Mu¨ssig).
0926-6690/02/$ - see front matter © 2002 Elsevier Science B.V. All rights reserved.
PII: S0926-6690(02)00005-5
P.Linger et al.
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Industrial Crops and Products
16 (2002) 3342
34
genic-derived pollutants. Consequently, these ar-
eas will no longer be able to be used for food
production. One of the most important classes of
pollutants are heavy metals which stem from cad-
mium-containing phosphate fertilisers, the smelt-
ing industry or sewage sludge distribution
(Adriano, 1986, Saxena et al., 1999).
However, several approaches exist for cleaning
up contaminated soils (Rulkens et al., 1998; Chen
et al., 2000). One of the most interesting is phy-
toremediation, or strictly speaking phytoextrac-
tion (Cunningham et al., 1995; Cunningham and
Ow, 1996; Ernst, 1996; Chaney et al., 1997;
Raskin et al., 1997; Salt et al., 1998; Chen et al.,
2000; Meagher, 2000). In this case, plants grow on
polluted soil, extract the toxic substances and
accumulate them in the upper parts of the plant.
They are then harvested, and consequently the
soil is cleaned up. On the other hand, the greatest
shortcoming of this method is the long period of
time needed for decontamination. The plants used
in phytoremediation are generally annual herbs
which dont have any economic value, but do
have a very high extraction potential, namely
hyperaccumulators (Robinson et al., 1997; Salt et
al., 1998; Wenzel et al., 1999).
The aim of our research is to combine phytore-
mediation with a crop of commercial interest,
with the view of achieving low price decontamina-
tion of soil by the production of a commercially
usable resource. The plant we chose for our ap-
proach was Cannabis sati6aL., hemp. Hemp has
been used by man for over 5000 years and is
known to have many uses. The bres can be used
for clothes, insulating material, or as a composite
material (Nature, 1996). The seeds serve as an
excellent source of oil due to its composition of
unsaturated fatty acids (Theimer et al., 1997). The
oil has a range of uses including production of
colours, lacquer and in the cosmetic industry
(Karus et al., 1995; Rausch, 1995; Wirtshafter,
1995; Hupperts et al., 1997). The seeds also
provide a source of protein for man and animals
(Patel et al., 1994). Moreover, the compounds
resulting from hemps secondary metabolism are
of major interest to the pharmaceutical industry
(Karus, 1995; Robinson, 1996; Grotenhermen,
1998).
Here, we explore the following issues: (a) is
hemp a suitable plant for phytoextraction; (b) is
the commercially utilisable bre material contami-
nated with heavy metals; and (c) if so, how does
this contamination inuence bre quality.
To nd out the answers to these issues, we
carried out a eld trial on a heavy metal contam-
inated eld.
2. Materials and methods
2
.
1
.Plant material/experimental arrangement
The hemp cultivation experiments were or-
ganised in 1999 at the trial station in Hagen
(Nordrhein-Westfalen, Germany) using the hemp
variety C.sati6aUSO 31. The plot of the test was
3×4 m wide, the seed was sown on 12th June.
The seed rate was 250 seeds/m
2
(with no addi-
tional fertilisation), and the number of plants
shortly before harvesting was nearly 100 plants/
m
2
. The mature plants were harvested about 15
weeks later on 24th September, with an average
stem height of 183 cm. The stems were picked by
hand, dried and stored at 20 °C and 50% relative
humidity. The stems and the separated hemp bre
bundles are named in accordance with the identi-
cation code USO Hagen 99. The soil of the trial
site had been polluted by sewage sludge distribu-
tion and contained 102 ppm cadmium (Cd), 419
ppm nickel (Ni) and 454 ppm lead (Pb) (Hygiene-
Institut des Ruhrgebietes, 1997).
We compared the bre content and the bre
properties from the trials on heavy metal polluted
ground with hemp stems from non-polluted
ground. Since there was no comparable unpol-
luted area near the polluted one, reference values
were taken from an area with different soil com-
position and meteorological conditions. Thus, the
observed differences are only partially caused by
the heavy metal contamination. We took samples
from the test location of the chamber of agricul-
ture Weser-Ems in the Wehnen district, in the
community of Bad Zwischenahn, near Oldenburg
in the northern part of Germany.
The experimental plants were subjected to 4
randomised repetitions. The plots of the test were
P.Linger et al.
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Industrial Crops and Products
16 (2002) 3342
35
3x6 m wide, and were sown also with hemp
variety USO 31 during the last week of April,
1999. The seed density was 200 seeds/m
2
with a
rate of nitrogen of 100 kg/ha, the germination
rate was on average 182 plants/m
2
(28th May).
The experimental plot was harvested on 27th Au-
gust, 1999 and hemp exhibited an average stem
height of 260 cm. However, the number of plants
reached the level of maturity required for harvest-
ing was much reduced. In 1999, the values of
plant density were only examined for the hemp
variety Fedrina 74. For this hemp variety, the
seed rate was also 200 seeds/m
2
and the number
of plants counted shortly before harvesting was 99
plants/m
2
. The stems of USO 31 were dried and
stored at 20 °C and 50% relative humidity
(Martens and Mu¨ssig, 2000). The stems and the
separated hemp bre bundles are named in accor-
dance to the identication code USO Wehnen 99.
The stems from both the contaminatedtrial in
Hagen and the controltest trial in Wehnen were
unretted.
2
.
2
.Mechanical separation of fibre bundles
After crop collection the stems were dried and
stored. The bre bundles were separated mechani-
cally with a BAHMER-FLAKSY laboratory
device. This equipment was developed by Bahmer
Maschinenbau GmbH (Germany) and consists of
four pairs of proled, rotating rolls. The speed
control was adjusted to position 10, resp. 10
m/min transport speed. After six passages through
the machine, the hurdless bre-bundles were
rened with a coarse separator. A self-developed
laboratory coarse separator was used. This ma-
chine consists of a serrated cylinder (Ø261 mm)
and is fed by a rotating roll (Ø32 mm). The
distance from the feeding roll to the rotating
serrated cylinder is 20 mm. The bre transport
after coarse separation was organised by air. The
results of separation are comparable with indus-
trial separation techniques (Mu¨ssig, 2001).
2
.
3
.Chemical separation of fibre
The bre content (pure bre content) was ex-
amined by the method from Bredemann (1942)
Fig. 1. Various forms of hemp bres open to testing (Mu¨ssig,
2001).
after chemical separation in 2% NaOH in an
autoclave at 2 bar pressure. From the test plots, a
random sample was taken and from this four
stems were cut into top, middle, and bottom
parts. The pure bre content was measured for
the different sections.
2
.
4
.Tensile testing
The mechanically separated hemp bres were
conditioned for 24 h at 20 °C and 65% relative
humidity. The strength of single hemp bre bun-
dles was tested. Fig. 1 shows the differences be-
tween the various forms of hemp bres which are
open to testing.
The single hemp bre bundles were tested in an
Instron universal testing device 4502 with an In-
stron 2518806/1 kN power cell. Samples were
fastened to a Pressley clamp with Plexiglas jaws.
The free clamping length was 3.2 mm and the test
speed was 2 mm/min. The device is shown in Fig.
2. The length of each tested single bundle was
Fig. 2. A single hemp bre bundle fastened to the Pressley
clamp.
P.Linger et al.
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Industrial Crops and Products
16 (2002) 3342
36
constant because of the thickness of the Pressley
clamps and the distance of the gauge length (3.2
mm). The length l
B
of each bundle was 15 mm.
The mass of the single bundles Mwas measured
with an accuracy of 0.01 mg. The mass related
neness gF (in tex) of each bundle could be
calculated with the following sizes equation:
gF=
M
mg
N
B
l
B
mm
·10
3
·10
6
=1000
(1)
With the calculated mass related neness gF (in
tex) and the experimentally measured value for
the breaking force of the single bundle F(in N),
the strength R
H
(in cN/tex) could be calculated
according to Eq. (2).
R
H
u
F
N
gF
tex
·1
10 (2)
To obtain an acceptable level of accuracy for bre
bundle strength, 100 valid results are necessary.
Experiments with bundle breaking inside or near
the clamping area or slipping effects were counted
as non-valid results.
2
.
5
.Fibre neness testing
The neness of bre bundles was examined by
an optical bre neness analyzer (OFDA) and
airow methods. The principle of the different
measurement methods is given in Fig. 3. The
OFDA was developed for measuring the diameter
of wool bre (Baxter et al., 1992). This apparatus
efciently measures width distribution of bast
bre bundles and results have been found to
correlate well with those of other methods. Be-
cause of the large number of measurements taken,
our results could be well reproduced. Compared
with the OFDA, the airow method does not
provide information about the distribution of
neness for individual bundles. However, this
method is very rapid as well as being highly
reproducible (Drieling et al., 1999).
Prior to the experiment the hemp bres were
conditioned for 24 h at 20 °C and 65% relative
Fig. 3. Airow and OFDA methods to measure the neness of
hemp bre bundles (Martens and Mu¨ssig, 2000).
humidity. The pressure of the Airow testing
device was adjusted to a water column of 120 mm
and calibrated after a recently developed method
to get comparable airow values from different
labs and researchers for hemp testing (Mu¨ssig,
2001). For each sample, we used three specimens
each weighing 2.5 g. The measurement was taken
three times.
The FMT-Shirley device works in the same way
as the airow, i.e. with indirect examination of the
bre surface by the ow of air. The coarse hemp
bre bundles were measured in the FMT at com-
pression stage P
L
. For each sample we used three
specimens each weighting 4 g. The measurement
was taken three times. In contrast to the airow,
coarser bres gave low and ne bres high Shirley
values.
To examine the bundle width distribution with
the OFDA, the bundles were cut into 3 mm long
snippets. The snippets were prepared on a slide
using tweezers. We prepared 5 slides for each
hemp sample for both USO Hagen 99 and USO
Wehnen 99. Each slide was scanned twice.
2
.
6
.Determination of hea6y metal content
Determination of heavy metal content was car-
ried out by means of atomic absorption spec-
troscopy (AAS). Four different parts of the plant
were prepared as samples: (1) seeds; (2) leaves; (3)
Í
Á
Ä
P.Linger et al.
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Industrial Crops and Products
16 (2002) 3342
37
bres; and (4) hurds. These samples were dried at
105 °C for 3 h prior to the analysis. For each
sample, 1.52 g were weighed in a 24-ml crucible,
and heated to 450 °C at a rate of 2 °C/min, and
kept at this temperature for 10 h.
After cooling, the residues were weighed again
to obtain the total residue amount, dissolved in 10
ml concentrated nitric acid (HNO
3
ROT-
IPURAN
®
, Roth no. 4989.1), and then diluted
with distilled water to a total volume of 50 ml.
This solution was used as the sample for AAS
determination of cadmium (Cd), lead (Pb) and
nickel (Ni) content in an AAS 5FL (Carl Zeiss
Technology). Heavy metal content of the original
sample was calculated back from the concentra-
tion of the measured solution.
3. Results and discussion
3
.
1
.Fibre properties
One problem we faced for this investigation was
that we could only use hemp plants from different
habitats. Many different factors are known to
inuence hemp bre quality and quantity such as
meteorological conditions, soil properties, fertili-
sation, sowing period, plant density and harvest
period. Therefore, it is difcult to compare the
results from plants of different origins. Neverthe-
less, the data could provide insight if soil contam-
inated with heavy metals has a signicant impact
on bre properties.
3
.
1
.
1
.Mechanical separation of bre
Mechanical extractable bre content after
decortication and mechanical separation was 26%
for USO Hagen 99 and 36% for USO Wehnen
99.
3
.
1
.
2
.Chemical separation of bre/pure bre
content
As described in Section 2.3, we examined the
bre content (pure bre content) using Brede-
manns method. The results are shown in Fig. 4.
We compared the bre content from the trials on
heavy metal polluted ground (USO Hagen 99)
with hemp stems from non-polluted ground (USO
Wehnen 99).
Fig. 4. Pure bre content of hemp stems/USO Wehnen 99 vs.
USO Hagen 99.
As seen in Fig. 4, the value of the pure bre
content in the stems of contaminatedUSO Ha-
gen 99 samples is reduced in comparison to the
values of the controlUSO Wehnen 99 samples.
This holds true for all parts of the stems.
Comparable results were achieved by mechani-
cal decortication and separation.
3
.
1
.
3
.Fibre neness
We examined the neness of the mechanically
separated hemp bre bundles using two measure-
ment methods. The Airow measurements are
shown in Fig. 5.
The Airow values gave highly similar results
for both contaminatedand controlhemp sam-
ples, with a tendency for the USO Wehnen 99
sample to be a little bit coarser. The same result
was observed with the FMT-Shirley values (Fig.
Fig. 5. Airow values for the neness of mechanically sepa-
rated hemp bre bundles/USO Wehnen 99 vs. USO Hagen
99.
P.Linger et al.
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Industrial Crops and Products
16 (2002) 3342
38
Fig. 6. FMT-Shirley value for hemp bre bundles/USO Weh-
nen 99 vs. USO Hagen 99.
Fig. 8. OFDA bre bundle width of hemp sample USO Hagen
99.
6). It should be pointed out that in general
coarser bres show reduced Shirley values.
The results from the airow and the FMT
measurements do not provide information about
the distribution of neness of the bundles. How-
ever, these methods are very rapid and highly
reproducible. To nd out about the distribution
of bre bundle width, we used the OFDA system.
This apparatus efciently measures width distri-
bution of bast bre bundles. The distribution of
the coarse separated bre bundles for the sample
USO Hagen 99 is documented in Fig. 7.
The results of the OFDA measurement show a
wide distribution of bre bundle width. For a
mechanically coarse separated unretted hemp
sample this is typical (Dreyer and Mu¨ssig, 2000).
The data of the USO Hagen 99 samples are
summarised in the box-and-whisker chart in Fig.
8.
The nearly identical results from the different
neness testing methods document the low differ-
ences between the neness of the bre bundles of
the two hemp samples USO Hagen 99 and USO
Wehnen 99.
3
.
1
.
4
.Strength of single bre bundles
As described in Section 2.4, we tested single
bre bundles and not collectives. The tensile prop-
erties of the coarse separated hemp bre bundles
are documented in the box-and-whisker chart in
Fig. 9.
A wide range of values were obtained, and was
more distinct for the single bundles USO Wehnen
99. The wide range of strength distribution of
hemp bres has also been documented in the
work of Sankari (2000) and Keller et al. (2001).
Although the values of the strength of the bre
bundles of USO Hagen 99 are smaller than those
of USO Wehnen 99, the values are still on an
acceptably high level and the distribution is more
homogeneous.
To summarize the results, heavy metal polluted
soil had no signicant inuence on bre proper-
ties. All results seemed to be in natural occurring
range.
Fig. 7. Distribution of bre bundle width of hemp USO Hagen
99.
P.Linger et al.
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Industrial Crops and Products
16 (2002) 3342
39
Fig. 9. Strength of single hemp bre bundles/USO Wehnen 99
vs. USO Hagen 99.
of the soil with these in the plants, we nd that
the concentration of Ni in the soil is only four
times higher than that of Cd. Therefore, there
must be different mechanisms for uptake and
accumulation for nickel, lead, and cadmium in
general and also for the different plant parts
themselves. The highest concentrations of all ex-
amined metals were found in the leaves, which
indicates the transport of heavy metals via the
xylem sap. In the seeds, the concentrations of Cd
and Ni are relative high. However, the concentra-
tions found in hurds and bres are comparably
small.
For Ni, the concentration relation was leaves\
seeds\hurds \bres, whereas it was leaves \
bres\hurds \seeds for Pb. For Cd, the relation
was leaves\seeds \bres =hurds, but the Cd
concentrations found here are comparably small.
Though, the possibility can not be ruled out that
concentration levels could be different in soils
with a different heavy metal composition.
Another interesting aspect is the total metal
uptake of the plant, which depends on (a) the
concentrations found in its single parts, and (b)
on the relative mass constitution of the plant.
That is to say, the contribution of the relatively
high metal concentrations found in the seeds to
the total mass of metal in the plant is negligible,
since the seeds contribute only 810% of the
plants total mass (LBP, 1996). The leaf content
accounts for 1315%, bre content 25 27%,
whereas the dominating part is the hurd content
with about 60%.
3
.
2
.Determination of hea6y metal content
For all samples Cd, Pb and Ni content were
examined by AAS. The complete results are dis-
played in Table 1. Heavy metals could be detected
in all parts of the plants which are of commercial
interest. In each case, the concentration relation
was Ni\Pb \Cd. It is obvious from the data,
that hemp shows a strong specicity for the accu-
mulation of various heavy metals. From this
study, the concentrations of Cd were eight to 26
times lower than the Ni concentrations. However,
when comparing the heavy metal concentrations
Table 1
Heavy metal contents of the hemp samples
WeightSample Residue Ni contentCd content Pb content
(g) (%)
ppm Average ppm Average ppm Average
1.732 12.962.6 0.78 2.60Hurds
2.8 9.99 11.51.973Hurds 2.6 0.76 0.8 2.94
7.421.537Fibres 3.5 0.85 3.97
6.96.323.93.780.8Fibres 0.793.31.575
63.8323.3Leaves 3.941.485 23.20
2.058 23.5 2.96 3.5Leaves 21.65 22.4 63.46 63.6
33.241.980.757 1.19Seeds 6.0
0.829 6.4 1.03 1.1 1.69 1.8Seeds 24.79 29.0
P.Linger et al.
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Industrial Crops and Products
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40
These mass contribution may be slightly differ-
ent depending on variety, season, and crop region,
but it depicts clearly that the plants total metal
accumulation is dominated in the hurds on one
hand, due to their large contribution of over 50%
to the total mass, and in leaves on the other hand
due to their high individual metal uptake.
To calculate the phytoextraction potential, we
determined the absolute amount of Cd in one
plant, i.e. 126 mg Cd (plant)
1
. By extrapolation
the total extraction of Cd by hemp could be
calculated as 126 g Cd (ha vegetation period)
1
.
This implies about 126 g Cd (ha)
1
in 34
months. Thlaspi caerulescens, one of the best stud-
ied hyperaccumulators for cadmium, is able to
accumulate 3000 ppm (Brooks et al., 1998) and to
extract up to 2 kg Cd (ha year)
1
under optimal
growth conditions (Saxena et al., 1999). The phy-
toextraction potential of T.caerulescens is ap-
proximately 16-fold higher when compared with
USO 31, but hemp grows well under natural
conditions, and does not require the expensive use
of fertilisers nor the time- and money-consuming
control of optimal growth conditions. Another
point is, that T.caerulescens provides nothing,
which could be used as a raw material for com-
mercial purposes.
The question that has be answered is: Could
hemp, grown on contaminated soil, be used as a
supplier of food or raw material for commercial
applications? The WHO (1972) and FAO/WHO
(1995) pointed out that 70 mg Cd uptake per day
are not harmful to man. The WHO set a limit of
0.1 mg heavy metal (kg food)
1
. These levels
would therefore disqualify hemp seeds or leaves to
be used in food production. However, hemp oil
could be utilized in lacquer or industrial oil pro-
duction. The use of hemp bres for clothes pro-
duction would not be possible as the heavy metal
concentrations exceed the O
8
ko-Tex-Initiative
(2000) (Hohenstein), which are 0.1 ppm for Cd,
0.21.0 ppm Pb and 1.0 4.0 ppm Ni.
The main use of contaminated bres and hurds
might be in combine material, where the bre are
embedded in polymers and could not be set free.
Another possible use of the plant material is for
energy production in thermal power stations, as
here the plant material falls below the restrictions
(Winkler, 1997). In addition, it might be possible
to recycle the metal from the ash, this process is
called phytomining (Chaney et al., 1995;
Robinson et al., 1997; Brooks et al., 1998; Ander-
son et al., 1999; Nedelkoska and Doran, 2000).
From our work, it seems unrealistic that hemp is
an economically viable option in regard to
phytomining.
4. Conclusion
The fact that C.sati6aaccumulates heavy
metals in all plant parts limits its use as a raw
material in clothes as well as in the food chain.
However, the high quality of the bres and hurds,
which were not affected by the heavy metal con-
tamination, allows them to be used in special
products like combine material. Our experiments
provided no evidence of bre damage due to
heavy metal contamination. Fibre bundle neness
and strength from the contaminated as well as the
non-contaminated hemp are identical within the
limits of experimental error. The bre content was
signicantly lower in hemp grown on unpolluted
soil, however, it is not possible to decide if this is
only an effect of the contamination.
Hemp seems to be best suited for soils with a
low content of heavy metals due to its relative low
phytoextraction potential. Hemps commercial as-
pects together with its ability of extracting heavy
metals from the soil makes it an ideal candidate as
a prot yielding crop when used for phytoremedi-
ation purposes.
Acknowledgements
The authors thank Reent Martens and Jakob
Gatena from the Chamber of Agriculture Weser-
Ems in Oldenburg, Germany for the possibility of
using the samples USO 31 from the cultivation
trials in 1999 and for the detailed report of the
experiments. We are much indebted to Ute
Melville from the Institute of Applied and Physi-
cal Chemistry of the University of Bremen for her
support in the AAS measurements.
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Industrial Crops and Products
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41
References
Adriano, D.C., 1986. Trace Elements in the Terrestrial Envi-
ronment. Springer, Berlin.
Anderson, C.W.N., Brooks, R.R., Chiarucci, A., LaCoste,
C.J., Leblanc, M., Robinson, B.H., Simcock, R., Stewart,
R.B., 1999. Phytomining for nickel, thallium and gold. J.
Geochem. Exploration 67, 407415.
Baxter, B.P., Brims, M.A., Taylor, T.B., 1992. Description and
performance of the optical bre diameter analyser (OFDA)
(ISSN 0040-5000). J. Textile Inst. 83 (4), 507526.
Bredemann, G., 1942. Die Bestimmung des Fasergehaltes bei
Massenun-tersuchungen von Hanf, Flachs, Fasernesseln
und anderen Bastfaserpanzen. Faserforschung 16 (1942),
1439.
Brooks, R.R., Chambers, M.F., Nicks, L.J., Robinson, B.H.,
1998. Phytomining. Trends Plant Sci. 3 (9), 359362.
Chaney, R.L., Li, Y.M., Brown, S.L., Angle, J.S., Baker
A.J.M., 1995. Hyperaccumulator based phytoremediation
of metal-rich soils. Will Plants have a Role in Bioremedia-
tion, vol. 14, Annual Symposium, University of Missouri,
pp. 3334.
Chaney, R.L., Malik, M., Li, Y.M., Brown, S.L., Brewer,
E.P., Angle, J.S., Baker, A.J.M., 1997. Phytoremediation
of soil metals. Curr. Opin. Biotechnol. 8, 279284.
Chen, H.M., Zheng, C.R., Shen, Z.G., 2000. Chemical meth-
ods and phytoremediation of soil contaminated with heavy
metals. Chemosphere 41, 229234.
Cunningham, S.D., Ow, D.W., 1996. Promises and prospects
of phytoremediation. Plant Physiol. 110, 715719.
Cunningham, S.D., Berti, W.R., Huang, J.W., 1995. Phytore-
mediation of contaminated soils. TIBTECH 13, 393397.
Dreyer, J., Mu¨ssig, J., 2000. New horizons in natural bre
production: separation of hemp and nettle with enzymes,
3rd International Symposium Biorohstoff Hanf and An-
dere Faserpanzen Wolfsburg, Germany, 1316th Septem-
ber, 2000. Proceedings symposium: http://www.nova-
institut.de/Bioresource-hemp
Drieling, A., Ba¨umer, R., Mu¨ssig, J., Harig, H., 1999.
Mo¨glichkeiten zur Charakterisierung von Festigkeit, Fein-
heit und La¨nge von Bastfasern. Technische Textilien,
Jahrgang 42, Heft 4, November 1999, pp. 261262 (and
E66).
Ernst, W.H.O., 1996. Bioavailability of heavy metals and
decontamination of soils by plants. Appl. Geochem. 11,
163167.
FAO/WHO, 1995. Joint Committee on Food Additives and
Contaminants. Position Paper on Cadmium (prepared by
France), 27th Session, The Hague, Netherlands.
Grotenhermen, F., 1998. Conference Reports Medical
Cannabis Congresses in Germany, J. Int. Hemp Assoc.
5(2), 1998, available from: http://www.commonlink.com/
users/carl-olsen/HEMP/IHA/v5n2.html
Hupperts, R., Karus, M., Grotenhermen, F., 1997. Hanfsamen
und Hanfo¨l-Erna¨hrungsphsiologischer und therapeutischer
Wert. Eine Verbraucher- und Patientenbroschu¨re. 1.
Auage, Hu¨rth: nova-Institut, 1997.
Hygiene-Institut des Ruhrgebietes, 1997. Bodengutachten,
Gelsenkirchen.
LBP, 1996. Versuchsergebnisse aus Bayern 1996 Hanf
Ertrag, Faserqualita¨t, Inhaltsstoffe von O
8
lund
Presskuchen. Bayerische Landesanstalt fu¨r Bodenkultur
und Panzenbau (Hrsg.), Freising, Germany.
Karus, M., 1995. Hanf-O
8
korohstoff mit Zukunft? Bioresource
Hemp Symposium Frankfurt.
Karus, M., Linden, W., Murr, C., Waskow, F., 1995. Weshalb
der Hanf wiederkehren wird: U
8
ber die universelle Nutz-
panze Hanf, in: Bro¨ckers, M. (Ed.) Die Wiederentdeck-
ung der Nutzpanze Hanf. Verlag Zweitausendeins,
Frankfurt a.M., pp. 299351.
Keller, A., Leupin, M., Mediavilla, V., Wintermantel, E.,
2001. Inuence of the growth stage of industrial hemp on
chemical and physical properties of the bres. Ind. Crops
Prod. 13, 3548.
Martens, R., Mu¨ssig, J., 2000. Quality production of hemp
bre. nova-Institut (Organi.): 3. BIOROHSTOFF HANF
(Wolfsburg 13. bis 16. September 2000). Ko¨ln/Hu¨rth:
nova-Institut, 2000. Proceedings symposium: http://
www.nova-institut.de/bioresource-hemp
Meagher, R.B., 2000. Phytoremediation of toxic elemental and
organic pollutants. Curr. Opin. Plant Biol. 3, 153162.
Mu¨ssig, J., 2001. Untersuchung der Eignung heimischer
Panzenfasern fu¨r die Herstellung von naturfaserversta¨rk-
ten Duroplasten-vom Anbau zum Verbundwerkstoff. Du¨s-
seldorf: VDI Verlag GmbH, 2001, (Fortschritt-Bericht
VDI, Reihe 5, no. 630), (ISBN 3-18-363005-2).
Nature (1996). Car-maker turns to cannabis for bre,
Nature 384, 95
Nedelkoska, T.V., Doran, P.M., 2000. Characteristics of heavy
metal uptake by plant species with potential for phytore-
mediation and phytomining. Minerals Engineering 13. No.
5, 549561.
O
8
ko-Tex-Initiative, 2000. O
8
ko-Tex Standard 100. Forschung-
sinstitut Hohenstein, Bo¨nnigheim.
Patel, S., Cudney, R., McPherson, A., 1994. Crystallographic
characterization and molecular symmetry of edestin, a
legumin from hemp. J. Mol. Biol. 235, 361363.
Raskin, I., Smith, R.D., Salt, D.E., 1997. Phytoremediation of
metals: using plants to remove pollutants from environ-
ment. Curr. Opin. Biotechnol. 8, 221226.
Rausch, P., 1995. Verwendung von Hanfsameno¨l in der Kos-
metik, Bioresource Hemp Symposium Frankfurt, 1995
Robinson, R., 1996. Hanf-Droge, Heilmittel, Nahrung, Faser.
Naturhaus, VGS Verlagsgesellschaft.
Robinson, B.H., Brooks, R.R., Howes, A.W., Kirkman, J.H.,
Gregg, P.E.H., 1997. The potential of the high-biomass
nickel hyperaccumulator Berkheya coddii for phytoremedi-
ation and phytomining. J. Geochem. Exploration 60, 115
126.
Rulkens, W.H., Tichy, R., Grotenhuis, J.T.C., 1998. Remedia-
tion of polluted soil and sediment: perspectives and fail-
ures. Water Sci. Technol. 37 (8), 2735.
Sankari, H.S., 2000. Comparison of bast bre yield and me-
chanical bre properties of hemp (Cannabis sati6aL.)
cultivars. Ind. Crops Prod. 11, 7384.
P.Linger et al.
/
Industrial Crops and Products
16 (2002) 3342
42
Salt, D.E., Smith, R.D., Raskin, I., 1998. Phytoremediation.
Annu. Rev. Plant Physiol. Plant Mol. Biol. 49, 643668.
Saxena, P.K., KrishnaRaj, S., Perras, M.R., Vettakkoru-
makankav, N.N., 1999. Phytoremediation of heavy metal
contaminated and polluted soils, In: Prasad and Hage-
meyer (Eds). Heavy Metal Stress in Plants, Prasad, Hage-
meyer, pp. 305329.
Theimer, R.R., Mo¨lleken, H., Hoppe, A., 1997. Oils from
Cannabis sati6aL. valuable food and raw materials for
pharmaceuticals and other industrial products. Bioresource
Hemp Symposium; Frankfurt/Main: 56.
Wenzel, W.W., Lombi, I., Adriano, D.C., 1999. Biogeochemi-
cal processes in the rhizophere: role in phytoremediation of
metal-polluted sites, In: Prasad and Hagemeyer (Eds).
Heavy Metal Stress in Plants, Prasad, Hagemeyer, pp.
273304.
WHO, 1972. Evaluation of certain food additives and of the
contaminants mercury, lead and cadmium (FAO Nutrition
Report Series No 51 WHO Technical Report Series 505).
Food and Agriculture Organization of the United Nations,
Rome, Italy.
Winkler, H.D., 1997. Umweltmedienu¨bergreifendes Gesamt-
konzept zur Entsorgung von Gebrauchtholz-Richtwerte
zur umweltvertra¨glichen Verwertung und Beseitigung.
Jahresbericht 1997, Landesumweltamt Nordrhein-West-
falen.
Wirtshafter, D., 1995. Why Hemp seeds? Bioresource Hemp
Symposium Frankfurt.
... Increasing numbers of agriculturally used areas are contaminated by anthropogenic-derived heavy metals (HM) (Ali et al. 2013;Linger et al. 2002). Management of these areas constitutes a major environmental challenge since toxic materials absorbed by plants may contaminate the food chain and represents a major risk for human health (Linger et al. 2002;Muthusaravanan et al. 2018). ...
... Increasing numbers of agriculturally used areas are contaminated by anthropogenic-derived heavy metals (HM) (Ali et al. 2013;Linger et al. 2002). Management of these areas constitutes a major environmental challenge since toxic materials absorbed by plants may contaminate the food chain and represents a major risk for human health (Linger et al. 2002;Muthusaravanan et al. 2018). These areas are therefore no longer suitable for food crop production. ...
Preprint
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... The fate of metal uptake because of ion exchange and transport through the roots leads to heavy metal accumulation in the vegetative tissues [30]. Linger et al. [7] reported the leaves to contain the highest concentrations of Lead, Nickel, and Cadmium in industrial hemp indicating the movement of heavy metals through the xylem sap. Brassica juncea, a commonly used plant for phytoremediation, also indicated the highest concentration of metals was in the leaves [30]. ...
Preprint
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... High biomass Linger et al., 2002;Citterio et al., 2005;Rheay et al., 2021. ...
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... Hemp grown for fibre can be used as a renewable resource to decontaminate pollutants such as metals, radioactive elements, organics including pesticides and fertilizers, oils and solvents from soils (Linger et al., 2002). According to Small and Marcus (2002), hemp has been used in land reclamation in the oil and gas industry in Alberta. ...
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... High biomass Linger et al., 2002;Citterio et al., 2005;Rheay et al., 2021. ...
Article
Full-text available
Biofortification is the supply of micronutrients required for humans and livestock by various methods in the field, which include both farming and breeding methods and are referred to as short-term and long-term solutions, respectively. The presence of essential and non-essential elements in the atmosphere, soil, and water in large quantities can cause serious problems for living organisms. Knowledge about plant interactions with toxic metals such as cadmium (Cd), mercury (Hg), nickel (Ni), and lead (Pb), is not only important for a healthy environment, but also for reducing the risks of metals entering the food chain. Biofortification of zinc (Zn) and selenium (Se) is very significant in reducing the effects of toxic metals, especially on major food chain products such as wheat and rice. The findings show that Zn-biofortification by transgenic technique has reduced the accumulation of Cd in shoots and grains of rice, and also increased Se levels lead to the formation of insoluble complexes with Hg and Cd. We have highlighted the role of Se and Zn in the reaction to toxic metals and the importance of modifying their levels in improving dietary micronutrients. In addition, cultivar selection is an essential step that should be considered not only to maintain but also to improve the efficiency of Zn and Se use, which should be considered more climate, soil type, organic matter content, and inherent soil fertility. Also, in this review, the role of medicinal plants in the accumulation of heavy metals has been mentioned, and these plants can be considered in line with programs to Frontiers in Plant Science (2022) Interaction between zinc and selenium bio-fortification and toxic metals (loid) accumulation in food crops. improve biological enrichment, on the other hand, metallothioneins genes can be used in the program biofortification as grantors of resistance to heavy metals.
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This paper evaluates the valorization potential of industrial hemp (Cannabis sativa L.) fibers produced on HM-contaminated soil as a safe feedstock for the textile industry. The chosen strategy was phytoattenuation, which combines the progressive soil quality improvement of contaminated land using phytoremediation techniques with the production of safe non-food biomass. A field experiment was set up with two hemp cultivars on a site contaminated with Cd, Pb, and Zn and on a nearby site containing clean soil as a control. Stem height and diameter were analyzed, as well as stem and fiber yield and the HM concentrations in the fibers, which were compared to legal safety standards and toxicity thresholds used in the textile industry. The hemp cultivar Carmagnola Selected (CS) had a significantly higher stem and bigger stem diameter compared to cultivar USO 31 on both sites. Stem yields showed a decrease of 30% and 50%, respectively, for both hemp cultivars grown on the contaminated site. However, the stem yield of CS growing on the contaminated site was similar to the stem yield of USO 31 growing on the control site, indicating that hemp cultivation on contaminated soil can be economically viable. Total and extractable Cd, Pb, and Zn fiber concentrations were far below the toxicity standards for textile production purposes. These results are promising in terms of the potential valorization of contaminated land with hemp cultivation and the development of a non-food value chain within a phytoattenuation strategy.
Chapter
High contamination of soils with heavy metals, mainly due to increasing anthropogenic activity, significantly contributed to the reduction of soil fertility worldwide and has an adverse impact on crop production and non-target organ-isms. In addition, toxic metals accumulating in the consumable parts of plants in quantities exceeding permissible levels pose a serious risk to human and animal health. Phytoremediation presents an environment-friendly green approach to clean areas contaminated with toxic metals. Metal-tolerant medicinal and aromatic plants have been found to be suitable candidates for this purpose because they can grow on metal-contaminated soils without significant adverse effects on plants, whereas the metal-induced stress has a positive effect on the quantity and possibly also on the quality of the essential oil without translocation of metals into essential oil, which ensures an economic profit of such a solution. In this chapter, attention is focused on the impact of heavy metals on the growth and physiological and biochemical char-acteristics of plants, classification of plants in terms of metal accumulation capacity, phytoremediation techniques and the impact of soil metal contamination on the yield of essential oils of medicinal and aromatic plants. The potential of individual medic-inal and aromatic plants (herbs, succulents, shrubs and trees) for decontamination of soils polluted with heavy metals by phytoextraction or phytostabilization and the impact of microorganisms and chelating agents on the phytoremediation efficiency is discussed. The pharmacological activities of some medicinal shrubs and trees are briefly mentioned as well. Keywords: essential oils, heavy metals, hyperaccumulators, medicinal and aromatic plants, metal accumulation, metalloids, oxidative stress, phytoremediation, phytostabilization
Article
Background: Cannabis species have a propensity to bioaccumulate toxic heavy metals from their growth media. Increased testing for these metals is required to improve the safety of the legal medical and recreational cannabis industries. However, the current methods used for mandated heavy metals tests are not efficient for a large framework. As a result, there is limited testing capacity, high testing costs, and long wait times for results across North America. Objective: This study aimed to demonstrate that pooling strategies can be used to increase the throughput in cannabis testing labs and reduce some of the strain on the industry. Methods: This paper presents an algorithm to simulate different pooling strategies. The algorithm was applied to real world data sets collected from Washington and California state testing labs. Results: Using a single pooling method, a pool size of three samples on average resulted in a 23.8% reduction in tests required for 100 samples for the Washington lab. For the California lab, pooling four samples on average resulted in a 54.1% reduction in tests required for 100 samples. Conclusion: The algorithms generated from the Washington and California lab data demonstrated that pooled testing strategies can be developed on a case-by-case method to reduce the time, effort, and costs associated with heavy metals tests. Highlights: The benefits of pooled testing will vary depending on the region and rate of contamination seen in each testing lab. Overall, our results demonstrate pooled testing has the potential to reduce the fiscal costs of testing through increased efficiency, allowing increased testing, leading to greater safety.
Chapter
Full-text available
High contamination of soils with heavy metals, mainly due to increasing anthropogenic activity, significantly contributed to the reduction of soil fertility worldwide and has an adverse impact on crop production and non-target organisms. In addition, toxic metals accumulating in the consumable parts of plants in quantities exceeding permissible levels pose a serious risk to human and animal health. Phytoremediation presents an environment-friendly green approach to clean areas contaminated with toxic metals. Metal-tolerant medicinal and aromatic plants have been found to be suitable candidates for this purpose because they can grow on metal-contaminated soils without significant adverse effects on plants, whereas the metal-induced stress has a positive effect on the quantity and possibly also on the quality of the essential oil without translocation of metals into essential oil, which ensures an economic profit of such a solution. In this chapter, attention is focused on the impact of heavy metals on the growth and physiological and biochemical characteristics of plants, classification of plants in terms of metal accumulation capacity, phytoremediation techniques and the impact of soil metal contamination on the yield of essential oils of medicinal and aromatic plants. The potential of individual medicinal and aromatic plants (herbs, succulents, shrubs and trees) for decontamination of soils polluted with heavy metals by phytoextraction or phytostabilization and the impact of microorganisms and chelating agents on the phytoremediation efficiency is discussed. The pharmacological activities of some medicinal shrubs and trees are briefly mentioned as well.
Book
Full-text available
Kenevir ve endüstri
Article
I intend to fill, with this book, a need that has long been felt by students and professionals in many areas of agricultural, biological, natural, and environmental sciences-the need for a comprehensive reference book on many important aspects of trace elements in the "land" environment. This book is different from other books on trace elements (also commonly referred to as heavy metals) in that each chapter focuses on a particular element, which in tum is discussed in terms of its importance in our economy, its natural occurrence, its fate and behavior in the soil-plant system, its requirement by and detriment to plants, its health limits in drinking water and food, and its origin in the environment. Because of long­ distance transport to pristine areas of cadmium, lead, copper, and zinc in relatively large quantities, these elements have an extra section on natural ecosystems. A blend of pictorial and tabular data are provided to enhance understanding of the relevant information being conveyed. Since individual chapters are independent of one another, they are arranged alphabetically. However, readers with weak backgrounds in soil science are advised to start with the chapter on zinc, since soil terminology is discussed in more detail here. Sections on sorption, forms and speciation, complexation, and transformations become more technical as soil physical-(bio )chemical phenomena are discussed. The less important "environmental" trace elements are discussed together in the "Other Trace Elements" chapter.
Chapter
According to most legislative schemes, a soil may require remediation if certain concentrations of one or more heavy metals is exceeded in a designated part (topsoil, subsoil) of the soil profile. A multitude of remediation technologies has been developed for clean-up of heavy-metal-polluted soils (Iskandar and Adriano 1997; Pierzynski 1997). Classic methods, such as excavation, thermal treatment and chemical soil washing are typically expensive and destructive.
Chapter
Most plants and animals depend on soil, as a growth substrate, for their sustained growth and development. In many instances the sustenance of life in the soil matrix is adversely affected by the presence of deleterious substances or contaminants. These pollutants can be broadly classified into two groups: (1) organic, which contain carbon, and (2) inorganic, devoid of carbon (Webber and Singh 1995). The focus of this chapter is to provide an overview of the plant-based remediation strategies for inorganic pollutants, while the use of such strategies for organic pollutants is also briefly discussed (for an indepth review see Cunningham et al. 1995).
Article
This paper describes the development of an image-analysis system designed to determine rapidly and precisely the fibre-diameter distribution of a representative specimen of fibre snippets.The instrument hardware and software are described, together with the procedures developed for the measurement of wool samples. Other animal and artificial fibres may also be satisfactorily measured by the instrument. This paper includes details of system trials and of a round trial undertaken in October, 1991, for the purpose of assessing precision statistics on wool for a proposed IWTO Test Method under Examination.The round trial confirmed that the test method proposed has an over-all precision very similar to that of the Fibre Diameter Analyser (FDA) test method, which was recently accepted by IWTO as a Test Method under Examination for wool.
Article
Pot trials and tests in outside plots were carried out on the South African Ni hyperaccumulator plant Berkheya coddii in order to establish its potential for phytoremediation of contaminated soils and for phytomining of Ni. Outside trial plots showed that a dry biomass of 22 t/ha could be achieved after moderate fertilisation. Pot trials with varying soil amendments with nitrogen and phosphorus fertilisers showed enhanced uptake of Ni with increasing nitrogen addition, though there was no reaction to phosphorus. The Ni content of the plant was directly related to the ammonium acetate extractable fraction of Ni in a wide range of natural and artificial substrates. Excision of shoots induced a dramatic increase in the Ni content in the new growth (5500 μg/g compared with 1800 μg/g Ni). When plants were grown in pots with Ni added to the substrate (0–1%), the Ni content of the plants rose to a maximum value of about 1% dry mass. The data from this last experiment were used to calculate the probable Ni yield (kg/ha) of plants grown in nickel-rich soils in different parts of the world. It was calculated that moderately contaminated soils (100 μg/g Ni) could be remediated with only two crops of Berkheya coddii. The potential of this species for phytomining has also been evaluated and it is proposed that a yield of 100 kg/ha of Ni should be achievable at many sites worldwide. Phytomining is also discussed in general terms for other metals as well as Ni.
Article
Experience gained with the remediation of contaminated sites over the last 10 to 15 years has strongly increased the insight into the problem and how it can be tackled. A large number of remediation techniques, most of which focus on clean-up, are now available, and some of them are intensively applied in practice. However, the experiences gained with them show that they are not capable of solving all problems. Furthermore, each case of soil pollution is different and the way to manage it requires, within the limits set by policy and the finances available, a careful weighing of all relevant factors. Increased knowledge about the problem has resulted in potential new techniques, such as extensive in-situ treatment, the use of special treatment walls, phytoremediation and intrinsic natural degradation.
Article
Phytomining is the production of a `crop' of a metal by growing high-biomass plants that accumulate high metal concentrations. Some of these plants are natural hyperaccumulators, and in others the property can be induced. Pioneering experiments in this field might lead to a `green' alternative to existing, environmentally destructive, opencast mining practices. Phytomining for a range of metals is a real possibility, with the additional potential of the exploitation of ore bodies that it is uneconomic to mine by conventional methods.