109
required N for plant grow. The experiment ran for 24 days. The solutions were replenished
with Mili-Q water to ensure a constant volume of 500 mL throughout the experiment.
The pH was measured directly in all glass vessels by a MeterLab PHM220 pH meter
(Radiometer, Copenhagen, Denmark) at day 0, 3, 7, 10, 14, 18, 21 and 24, and dissolved
oxygen (DO) was measured at day 24 by a portable DO meter (OxyGuard International
A/S, Birkeroed, Denmark). The TBU analysis was performed by high-performance liquid
chromatography (HPLC; Thermo Scientific Ultimate 3000) using a diode array detector
(DAD). The analytes were separated on a Synergy 4μ Polar 80 Å column (150 mm × 2.0
mm ID) and the detector signal was monitored at λ = 220 nm and 240 nm.
The fresh biomass (FB), length of the longest root, maximum leaf/stem length and number
of leaves of both control and treated plants were determined at day 0, 3, 7, 10, 14, 18, 21
and 24, respectively. The relative growth rates (RGR) of the plants were quantified based
on Hadad et al [11], Eq. (1):
RGR =
2
−
1
(1)
Where
W
1
and
W
2
were the FB of plants at the start and the end of the experiment,
respectively, and t is the duration of the experiment (days).
The tolerance index (TI) was calculated based on the relative growth rate using Eq. (2):
TI (%) =
× 100
(2)
Results
After 24 days of treatment,
Berula erecta
achieved the highest removal (49%) when
compared with the removal efficiency of the other plants,
Typha latifolia, Phragmites
australis, Iris pseudacorus
, and
Juncus effusus
(27%, 31%, 25%, and 41%, respectively). A
significant reduction in RGR, root and stem/leaf growth rates were observed.
Phragmites
australis
showed the highest toxic tolerance (TI), followed by
Berula erecta
,
Iris
pseudacorus, Juncus effusus
and
Typha latifolia
. Our results suggest that the studied
species of wetland plants potentially can be used for the removal of TBU from
contaminated water. However, the mechanisms of the removal need to be resolved. Our
study was, however, conducted at a relatively high TBU concentration that adversely
affected the growth of the plants. Additional studies at more realistic low concentrations of
TBU need to be conducted to further assess the potential applicability of these wetland
species for TBU phytoremediation purposes.
Keywords
: emergent plants; pesticide; phytoremediation; plant growth; toxic tolerance
References
Ahmed, S., et al., Influence of parameters on the heterogeneous photocatalytic degradation
of pesticides and phenolic contaminants in wastewater: a short review. Journal of
Environmental Management, 2011. 92(3): p. 311-330.
