The effect of manure, zeolite and soil ageing in the dynamics of - - PowerPoint PPT Presentation

UNIVERSITY OF THESSALY

DEPARTMENT OF AGRICULTURE CROP SCIENCE AND RURAL ENVIRONMENT Laboratory of Soil Science

• Dr. Vasileios Antoniadis, Assistant Professor

The effect of manure, zeolite and soil ageing in the dynamics of hexavalent chromium in Cichorium spinosum

• V. Antoniadis, T. Polyzois, S. Petropoulos,

E.E. Golia and A. Dimirkou

Cr(VI): Highly toxic--easily mobilized in soil Cr(VI): CrO4

2- and HCrO4

• Anion

Not retained by soil colloids (mainly of negative charge) Easily absorbed by plants Mainly anthropogenic inputs (industrial waste-waters) In Greece: Assopos plain Vegetable producing area

Cr(VI) reduction Cr(III) (a likely reaction in soil) Cationic (Cr3+), relatively inert, low availability Mitigation practice: Allow time for ageing! [#1] (applies when Cr(VI) is not continuously deposited) [#2]Add organic matter Accelerates reduction [#3]Add positive-charge surfaces e.g., surfactant-modified zeolites Marked disadvantages of SMZ: Natural z. = negative charge SMZ: Positive charge

Marked disadvantages of SMZ:

• 1. Costly to modify

Not for field scale

• 2. Creates hydrophobic surfaces in soil

[#3] Use of natural zeolite Possible physical entrapment of anions in pores Cichorium spinosum Thorny chicory

• Wild vegetable species
• Tolerates harsh conditions (draught, salinity)
• Suspected tolerant species in Cr(VI)-contaminated soils

Edible shoots

Aims of our study: to test addition of manure, addition of zeolite soil ageing as Cr(VI) mitigation practices in a soil cultivated with C. spinosum.

Materials and Methods Pot experiment Soil with OM 1.3%, pH 7.5

5 treatments (x 5 replicates): (a) C: Control soil, with no additions (b) S: Soil added with 100 mg Cr(VI) kg-1 (c) Z: Soil added with 100 mg Cr(VI) kg-1 and 1% w/w zeolite (d) M: Soil added with 100 mg Cr(VI) kg-1 and 1% dry farmyard manure (e) AS ( “aged soil”): The same soil, amended one year before the experiment with 100 mg Cr(VI) kg-1 was used.

2-L pots Duration = 60 days At end: Harvested aerial biomass-obtained soil sample Plant: Oven-dried, biomass weighed, dry-ashed (500 0C for 5 h), extracted with 20 mL 20% HCl Soil: Extracted for Cr(III) (with DTPA) Cr(VI) (with 0.01 M KH2PO4)

No Cr (either III or VI) in control

(b)

a b b b c 30 60 90 120 150 C Z M S AS Soil C r(V I) (m g kg

• 1)

(a)

b ab a a a 20 40 60 80 100 120 C Z M S AS Soil C r(ΙΙΙ) (m g kg

• 1)

Cr(III): Z sign. higher than other treatments Cr(III) only from Cr(VI) reduction Produced Cr(III) entraped in z. pores... ...released slowly ...lasts longer in soil

Cr(VI) at S: minimal reduction

(b)

a b b b c 30 60 90 120 150 C Z M S AS Soil C r(V I) (m g kg

• 1)

(a)

b ab a a a 20 40 60 80 100 120 C Z M S AS Soil C r(ΙΙΙ) (m g kg

• 1)

Added Cr(VI)=100 Cr(VI) decreased at Z, M, and AS (no sign. diff.) Concurs with low Cr(III) at S

C: Some minimal Cr(III), but no Cr(VI)

(a)

b b a b a 5 10 15 20 25 C Z M S AS Plant Cr(III) (mg kg

• 1)

(b)

a c b c c 100 200 300 400 C Z M S AS Plant Cr(VI) (mg kg

• 1)

Same Cr(III) to Z, S, and AS (lower at M) Similar for Cr(VI): Z, S, AS: Same (lower at M) Thus (combing soil and plant data): Z in soil helped at Cr(III) evolution... ...but remaining Cr(VI) equally available AS in soil decreased Cr(VI)...

M was successful Two mechanisms: (a) Cr(VI) reduction to Cr(III) (b) organic ligands If (a) was true: Cr(III) should increase in soil and plant At M Cr(III) was the lowest of treatments (a) = false. (b) must be true... ...but we can not prove it (at the moment)

Cr(VI) toxicity indicated

(c)

a a a a b 1 2 3 4 C Z M S AS Biomass (g pot

• 1)

Regression analyses...

Cr(III) soil vs. plant

(b)

y = 0.5016x + 102.16 R 2=0.567*** p =0.0005 100 200 300 400 500 100 200 300 400 500 600 Cr(VI)-soil Cr(VI)-plant

(a)

y = 0.2138x + 7.1907 R 2=0.443** p =0.0019 5 10 15 20 25 20 40 60 80 Cr(III)-soil Cr(III)-plant

Cr(VI) soil vs. plant Cr(VI)-plant vs. biomass

(c)

y = -0.4447Ln(x) + 2.8148 R 2=0.941*** p<0.0

1 2 3 4 100 200 300 400 500 Cr(VI)-plant Biomass

20

Conclusions: The addition of organic matter (here, manure) is the best practice to minimize the Cr(VI) effects to C. spinosum. Thank you for your attention