Impact of soil amendments on the freely

(1)

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Conclusion

• PDMS fiber and silicone O-ring can measure

C

_free

_{, chemical activity and diffusive mass fluxes in (un)planted soil}

• No detectable amounts of PAHs were measured either in the shoot or the leaves over 2 months

• Adding AC may quickly and permanently reduce the acute toxicity and bioavailability of PAHs in soil

• Plant-promoted microbial degradation may be a main mechanism of natural attenuation of PAHs

Impact of soil amendments on the freely dissolved concentrations,

chemical activities, and diffusive mass fluxes of PAHs in soil

Objectives

1. To investigate the potential of the soil amendments activated charcoal (AC), charcoal (biochar) and compost to

sorb

PAHs and the

effect of this on their bioaccessibility and bioavailability in soil.

2. To assess the capacity of plants to reduce the freely dissolved concentrations (

C

_free

_{), chemical activities (}

a

_{), and diffusive mass fluxes}

of PAHs in a planted and unplanted spiked soil.

Geoffrey Marchal

1 , Kilian E. C. Smith

1 , Zuzanna Frková

1 , Philipp Mayer

1 , Lis Wollesen de Jonge

2 , and Ulrich G. Karlson

1

_{Department of Environmental Sciences, Aarhus University, Box. 358, Frederiksborgvej 399, DK 4000 Roskilde, Denmark}

2

_{Aarhus University ,Department of Agroecology, Research Centre Foulum, Blichers Allé, Postbox 50, DK 8830 Tjele, Denmark}

Sorbent carbonaceous soil amendment | phytoremediation | bioaccessibility | bioavailability | radish (

Raphanus sativus

L.)

Method

• Agricultural soil (3% OM)

• Phenanthridine, phenanthrene, anthracene, fluoranthene, pyrene spiked at 30 mg

kg

soil

-1

_{and spiked soil was stored at 4°C for 1 month After 2 months (t = 0d),}

radish (5 per pots) were planted. Control with PAHs spiked soil but no

amendment nor plant

• AC, biochar or compost added at 10 g per kg soil

-1

_{and stored again at 4°C for 1}

month. Control with soil only and no amendment

• Silicone (6 O-rings) added to the soil as an extractive sink to measure diffusive

mass fluxes

• PDMS fiber added to the soil to measure freely dissolved concentration (

C

_free

₎

• At

t

_{= 7, 21, 42, 60 days 1 PDMS fiber was removed, and}

C

_free

_{and chemical}

activity were measured

• At

t

_{= 60 days all silicone O-rings were removed and diffusive mass fluxes were}

measured

Geoffrey Marchal

geoffrey.marchal@hotmail.com

aquarium

water radish

Aluminium lined pot

PDMS fiber

root

Soil

Silicone O-ring stem leaf

Air exchange

Results

C

_free

_{in planted soil}

Fig. 1: Measured freely dissolved pore water concentration of PAHs (C_free_{, µg L}-1_{) in the soils with radish plants and amended with either 1% (w/w) of activated carbon (AC), charcoal or compost. The control was soil with radish plants but without}

any soil amendment. The initial concentration of each PAH was 30 mg kg-1_{. Error bars indicate the range (n=4).}

Fig. 2: Measured initial (t_{= 7d) and final (}t_{= 60d) freely}

dissolved pore water concentration of PAHs (C_free_{, µg L}-1_{) in the}

control soil with radish plants (control soil) and the equivalent soil without plants (+B/+V). The initial concentration of each PAH was 30 mg kg-1_{. Error bars indicate the range (n =4).}

Fig. 3: Comparison of the sum chemical activity over time of the PAHs (sum of 5 PAHs) in the soils with radish plants and amended with 1% (w/w) of activated carbon (AC), charcoal or compost. The control was soil with radish plants but without any soil amendment. Also shown is the sum chemical activity of the equivalent unplanted soil (+B/+V). The initial concentration of each PAH was 30 mg kg-1_{. The grey zone}

indicates the range in chemical activities observed in the literature for the onset of lethal baseline toxicity.

C

_free

_{planted soil}

vs.

_{unplanted soil}

_{Chemical activity planted soil}

vs.

_{unplanted soil}

Fig. 4: Measured uptake fluxes of PAHs into the silicone O-rings in ng cm-2_d-1_from

the soils with radish plants and amended with 1% (w/w) of activated carbon (AC), charcoal or compost. The control was soil with radish plants but without any soil amendment. Also shown is the sum chemical activity of the equivalent unplanted soil (+B/+V).The initial concentration of each PAH was 30 mg kg-1_{. Error bars}

indicate the range (n =4).