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| Titel |
Influence of vegetative filter strips on heavy metal retention in runoff waters: a laboratory evaluation |
| VerfasserIn |
Thomas Lambrechts, Charlotte de Braekeleer, Anne Iserentant, Guido Rentmeesters, Stanley Lutts, Charles Bielders |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250032263
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| Zusammenfassung |
| Point-polluted industrial sites can be exposed to water erosion, leading to a dispersion of,
e.g., heavy metal contaminated soil particles. Sowing vegetative buffer strips could limit
this problem. We therefore investigated the influence of different vegetative filter
strips on heavy metal retention, for runoff water loaded with two different polluted
sediments.
An experimental flume was built in order to simulate sediment retention by short
vegetative buffer strips for different runoff discharges, slopes and sediment concentrations. At
the lower bound of the flume, a 0.58 m wide x 1 m long x 0.1 m deep cage filled with soil
could be inserted. Three treatments were considered: bare soil and soil sown with
either Trifolium repens or Lolium perenne. The plants were allowed to grow for 2
months after germination. The setup allowed characterizing the water and sediment
discharge at the outlet of the vegetative strips by means of a tipping bucket with splitter
device.
Heavy metal-polluted soils were collected at two industrial sites highly polluted with 1)
arsenic and lead (Ath), and 2) cadmium and zinc (Prayon). We investigated the
effects of the three different covers for these two sediment types (4 replications by
treatment), with a slope of 8%, a discharge of 1.7 m3/h and a sediment concentration
of 10g/l. Besides sediment mass, we determined heavy metal concentrations and
particle size of the sediments collected both at the outlet of the flume and in the
sediment deposits upstream of the strips. Following these experiments, size separation
of the initial soils was performed, to analyze heavy metal concentrations of each
size class. Finally, selective extractions (water, CaCl2 and EDTA) were performed,
allowing estimation of heavy metal soluble fractions not retained by vegetative filter
strips.
Ath Prayon
As [%] Pb [%] Cd [%] Zn [%]
Lolium perenne 24.1 21.5 23.7 21.2
Trifolium repens 47.8 40.5 55 52.4
Bare soil 20.5 10.9 26.5 22.1
Concentrations [mg/kg] 800 40000 42 2400
Heavy metal retention by vegetative filter strips and mean concentrations
[mg/kg] of soils.
Heavy metal concentrations increased at the outlet of the flume because of selective
sedimentation. Vegetative filter strips with Trifolium repens were the most effective to trap
sediments and heavy metals. These strips slowed significantly the flow, leading to important
sediment deposits upstream. Lolium perenne were not more efficient than bare
soil, because of its erected posture and its low number of tillers after 2 months. |
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