G L O B A L S Y M P O S I U MO N S O I L

P O L L U T I O N2 - 4 M A Y 2 0 1 8 | F A O - R O M E , I T A L Y

Fig. 2: Soil column set up.

Fig. 1: Picture of experiment equipment. (Mariotte bottle was used to supply water)

Possible pathways for Microplastics transport through soil and leaching to groundwater

Miao Yu1,2, Martine van der Ploeg1, Esperanza Huerta Lwanga1,3, Xiaomei Yang1, Hennie Gertsen1, Shaoliang Zhang1, Xiaoyi Ma2, Coen J Ritsema1, Violette Geissen1

1Soil Physics and Land Management Group, Wageningen University & Research; 2College of Water Resources & Architectural Engineering, Northwest A&F University,

3Agroecología, El Colegio de la Frontera Sur, Unidad Campeche.

12 cm

20 cm

40 cm

10 cm

basket

column

leachate

Tap water leaching

MP & litterSoil surface

Treatment

Leaching

Soil (Saturated)MPsLitterEarthworms

14 days

Collecting leachate and

filter itCollect floating

materials

Dry filter paper

Microscope

Glass slidesCut soil column

Extract MP from soil samples of cast walls

(Floating method)

Count burrows and scale the cast

0

500

1000

1500

2000

2500

0 200 400 600

EC

µs/

cm

time ( min)

C 1C 2C 3C 4C 5C 6C 7C 8

INTRODUCTION

› Microplastics (MPs) = plastic debris < 5 mm.

› MPs research mainly focused on aquatic ecosystems .

› knowledge gap in risks of MPs in terrestrial ecosystems .

› MPs in soil surface litter are ingested by earthworm and transported into burrows.

› Potential risk of MPs leaching to groundwater

OBJECTIVES

Assessment of leaching risk of light Polyethylene MP in a saturated sandy soil column (C) setup with biogenic tunnels.

METHODOLOGY

• MPs: Light Density Polyethylene (LDPE, 50% 1 mm-250 µm, 30% 250 µm-150 µm and 20% < 150µm), 7% w/w dry Litter.

• Soil type: Sandy soil (7 kg per column, OM 3.37%).

• Earthworm type: Lumbricus terrestris.

• 3.97 g MPs mixed with dry lit-ter (52.78 g per column) on soil surface and two adult earth-worms in each column.

• Incubation: 14 days (tempera-ture 16 °C and humidity 40%).

• Treatments: 8 replicates.• Leaching: bromide solution as

a tracer and measuring electric-ity conductivity in drainage when leaching.

• MPs extraction from leachate: collecting leachate after leach-ing, filter drainage water and extracting floating materials on filter paper (Fig. 3).

• MPs extraction from soil sam-ples: Floating method.

MAIN RESULTS

1. Solution in soil columns was totally replaced by tap water (Fig. 4) and breakthrough curves showed differences in biogenic activity.

2. 5.75±2 tunnels per column after 2 weeks incubation (Fig. 5). Bur-rows’ depth per column ranged from 0 cm to 50 cm, with an average of 20-30 cm depth.

3. MPs was found in soil samples in each soil layer (Fig. 5 and 6).

4. MPs was found in leachate (Fig. 7).

CONCLUSION

• Biogenic activities such as earth-worms can distribute and trans-port MP from surface into deep-er soil layers.

• With biogenic activities influ-ence, MPs leaching occurs by saturated preferential flow, which indicates a potential risk of MPs leaching to groundwater in terrestrial systems.

Fig. 3: Flow chart of experiment procedure.

Fig. 4: Soil column breakthrough curve with Bromide solution as a tracer.

Fig. 5: Burrows in soil column one.

Fig. 7: MPs particles per liter leachate after one saturated flow event.

0

0,02

0,04

0,06

0,080,1

0,12

0-10c

m

10-20

cm

20-30

cm

30-40

cm

40-50

cm

Aver

age

MP

wei

ght

conc

entra

tion

in so

il (%

)

Soil layer

2,53

6,69

14,82

3,15

0,85

11,46

8,93

5,92

0,002,004,006,008,00

10,0012,0014,0016,00

C 1 C 2 C 3 C 4 C 5 C 6 C 7 C 8

MP

parti

cle

num

ber /

litre

Columns

Fig. 6: MPs weight concentration in soil samples in treatment with MP and earthworm burrows (biogenic activities).

Poster GSOP 2018 01-20.indd 27 19/04/18 19:01