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

2- and HCrO 4 Anion Cr(VI): CrO 4 - Not retained by soil colloids (mainly of negative charge) Cr(VI): Highly toxic--easily mobilized in soil 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 (Cr 3+ ), relatively inert, low availability [#1] Mitigation practice: Allow time for ageing! (applies when Cr(VI) is not continuously deposited) [#2]Add organic matter Accelerates reduction [#3]Add positive-charge surfaces e.g., surfactant-modified zeolites Natural z. = negative charge SMZ: Positive charge Marked disadvantages of SMZ:

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

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 0 C for 5 h ), extracted with 20 mL 20% HCl Soil: Extracted for Cr(III) (with DTPA) Cr(VI) (with 0.01 M KH 2 PO 4 )

120 150 (a) b (b) c -1 ) 100 -1 ) 120 Soil C r(ΙΙΙ) (m g kg Soil C r(V I) (m g kg 80 90 ab 60 b 60 b 40 b a 30 20 a a a 0 0 C Z M S AS C Z M S AS No Cr (either III or VI) in control 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

120 150 (a) b (b) c -1 ) 100 -1 ) 120 Soil C r(ΙΙΙ) (m g kg Soil C r(V I) (m g kg 80 90 Added Cr(VI)=100 ab 60 b 60 b 40 b a 30 20 a a a 0 0 C Z M S AS C Z M S AS Cr(VI) at S: minimal reduction Concurs with low Cr(III) at S Cr(VI) decreased at Z, M, and AS (no sign. diff.)

25 400 c (a) (b) c b b -1 ) -1 ) c 20 Plant Cr(VI) (mg kg Plant Cr(III) (mg kg 300 b 15 200 10 b a a 100 5 a 0 0 C Z M S AS C Z M S AS C: Some minimal Cr(III), but no Cr(VI) 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... AS in soil decreased Cr(VI)... ...but remaining Cr(VI) equally available

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)

(c) -1 ) 4 Biomass (g pot b 3 2 a a a a 1 0 Cr(VI) toxicity indicated C Z M S AS Regression analyses...

25 (a) 20 Cr(III)-plant Cr(III) soil vs. plant 15 y = 0.2138x + 7.1907 10 R 2 =0.443** 5 p =0.0019 0 0 20 40 60 80 Cr(III)-soil 500 (b) 400 Cr(VI)-plant 300 Cr(VI) soil vs. plant y = 0.5016x + 102.16 200 R 2 =0.567*** 100 p =0.0005 0 0 100 200 300 400 500 600 Cr(VI)-soil 4 (c) y = -0.4447Ln(x) + 2.8148 R 2 =0.941*** 3 Cr(VI)-plant vs. p <0.0 Biomass 2 biomass 1 0 0 100 200 300 400 500 20 Cr(VI)-plant

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