Investigation of selenium and arsenic in soil samples from a long-term field experiment Béla Kovács, Éva Széles, József Prokisch, Zoltán Győri University of Debrecen, Centre of Agricultural Sciences Department of Food Science and Quality Assurance 4032 Debrecen Böszörményi str Hungary

Debrecen Budapest Nagyhörcsök Pecs

We have to study the following goals in this research programme The behaviour of arsenic and selenium in soil:  total concentration,  available concentration,  leaching,  transformation.

Worldwide variation in Se status (Combs, 2001) USA China (urban) Venezuela Finland normal level Hungary China (Keshan dis. areas) Croatia

The applied elements and doses in the long-term field experiment (Nagyhörcsök Experimental Station)

Total element contents of soil samples depending on doses (sampling: 1994)

Lakanen-Erviö soluble element contents of soil samples depending on doses (sampling: 1994)

Rate of Lakanen-Erviö soluble and total element contents of soil samples depending on doses (sampling: 1994)

Concentration of arsenic depending on duration of field experiment and doses in soil samples

Plot treated with arsenic (4. level) Nagyhörcsök Experimental Station

Concentration of selenium depending on duration of field experiment and doses in soil samples

Plots treated with selenium (4. and 3. levels) Nagyhörcsök Experimental Station

Selenium content of treated (the highest level) and control plots in different soil layers (2000)

Analysis of selenium standards by IC-ICP-MS instrument 100 ppb Se-Meth+100 ppb selenite+100 ppb selenate Detection limits: 0.01 – 0.05 – 0.1 ppb Se-methionine selenite selenate (Se(IV), SeO 3 2- ) (Se(VI), SeO 4 2- ) COOH CHNH 2 CH 2 Se CH 3

selenate selenite organic selenium forms Comparison of contents of selenium forms in 1991 (I: 1. repetition, 1, 2, 3, 4 doses: 30, 90, 270 and 810 kg/ha)

Fate of selenite in soil (1:10 water extract) Heavy metal load field experiment: Dr. Imre Kádár, Nagyhörcsök oxidation selenite selenate organic selenium Conclusion: selenite will be oxidised in soil to selenate selenate more available for plants (it is analogous to sulphate) risk of leaching selenite selenate

Comparison of contents of selenium forms in 2000 from different layers selenite selenate organic selenium forms

Acknowledgements Dr. Imre Kádár (RISSAC) Hungarian Scientific Research Fund (OTKA T38450) István Széchenyi Scholarship

Thank you for your attention! As Se As Se

Separation of selenium ions by High Performance Liquid Chromatography – Inductively Coupled Plasma Mass Spectrometer hyphenated system (HPLC-ICP/MS) High Performance Liquid Chromatography (HPLC) column: IC-AN1 anion exchanger Inductively Coupled Plasma Mass Spectrometer (ICP-MS) Eluent: Phtalic- acid-Tris buffer

Other information  Different levels of the selected metal salts (13) were added to plots once at starting year (1991) and were mixed into the ploughed layer (0-20 cm)  The treatments were arranged in a split-plot design with replications (2)  These experimental plots are cultivated with commonly used agrotechnics, chemical fertilizers are added yearly to ensure sufficient macronutrient (NPK) supply  Composite soil samples consisting of 20 subsamples are collected yearly from the ploughed layer of each plot  To check the vertical movement of these pollutants, samples are also taken from the subsoil of plots with the highest level of added metal salts in some years (1993, 1996, 2000)  Type of soil in the experiment : calcareous loamy chernozem

Plot treated with cadmium (4. level) Nagyhörcsök Experimental Station

Plot treated with lead (4. level) Nagyhörcsök Experimental Station

Plots treated with molybdenum (1. and 4. levels) Nagyhörcsök Experimental Station

Nagyhörcsök Experimental Station plant and soil samples - The experiment includes: 4 levels in duplicate, i.e. 8 plots, each with a size of 21 m 2. - Experimental plants: maize (1991), carrot (1992), potato (1993), peas (1994), red beet (1995), spinach (1996), wheat (1997), sunflower (1998), sorrel (1999), barley (2000), rape (2001), poppy (2002), wheat (2003), alfalfa (2004), alfalfa (2005) - Soil sampling and analyses on soil samples: 1991: 0-20 cm soil layer of the plots, 1993: "mobile" fraction in the 0-20, 20-40, cm soil layers from plots with the highest level of added metal salts, 1996: "mobile" and "total" fractions in the 0-30, 30-60, cm soil layers from plots with the highest level of added metal salts. 2000: As: 0-20, 20-40, 40-60, cm soil layers from plots with the highest level of added metal salts, Se: 0-30, 30-60, 60-90, , , , , , cm from plots with the highest level of added metal salts.

Results considering plant analyses 1.Owing to the highest level of arsenic treatment, the quantity of crop of each applied plant decreased in each year. However arsenic content was not increased in different parts of plants, it was about 1-2 mg/kg concentration range. Arsenic is not mobile in the soil-plant system. From the applied plants, peas and spinach were the most sensitive affected by arsenic. Presumably the applied arsenite (As(III)) is transformed to arsenate (As(V)) which is the more toxic species. 2. The destroying effect of Se does not decrease with years, and what is more the effect of Se increases. Presumably the applied Na-selenite form is transformed to the more toxic Ca-selenate, it is oxidized among those soil conditions. We have to determine the concentration of different selenium species (selenite and selenate) in soil samples during our research. Similarly to Mo, Se is extremely mobile, the plant parts contain many hundreds mg/kg of selenium accompanied toxic symptoms. High applied concentration of selenium destroys even weed-plants recently also. The arsenic and selenium caused decrease of yield of different plants owing to the fitotoxic effect between : - maize seed: As and Se - red beet root: Se - carrot root: As and Se - spinach leaf: As and Se - potato tuber: As and Se - wheat seed: As and Se - peas seed: As and Se