Application Od Stable Isotopes in Environmental Studies and in Food Authentication

STUDIA UNIVERSITATIES BABES_BOLYAI, PHYSICA, SPECIAL ISSUE, 2003

APPLICATION OD STABLE ISOTOPES IN ENVIRONMENTAL STUDIES AND IN FOOD AUTHENTICATION

Andrzej G. Chmielewski, Ryszard Wierzchnicki, Małgorzata Derda, Agnieszka Mikolajczuk, Grazyna Zakrzewska-Trznadel Institute of Nuclear Chemistry and Technology Dorodna 16, 03-195 Warsaw (Poland)

Abstract Environmental isotopes of light elements are used as modern, specific and reliable technique for studies of global element cycles, hydrology, and recently more and more for pollution monitoring. After the identification and quantification of pollution, it is of interest to characterize the sources and determine whether the pollution is locally derived or has been transported over long distances. Surface sources of pollution can be designated as natural, industrial, agricultural or domestic. 2- Atmospheric sulphur compounds e.g. SO2 and SO4 originate from coal combustion, volcano eruption or are produced by sea microorganisms. Measurements of 34S/32S in the samples are a useful way to distinguish of the sources. Isotopic ratio 34S/32S can be considered as a natural marker for the pollution origin study. Among other hydrological and chemical methods, tritium analysis and methods based on measurement of isotopic ratio of 2H/1H , 34 32 18 16 2- S/ S and O/ O in SO4 ions are used for monitoring and prognosis of the ground water quality in the vicinity of Bełchatów lignite mine. INCT carries on periodical monitoring of ground water in that industrial region. Natural products such as wine, spirits, fruit juices, flavours, oils, and honey are prime targets for fraudulent adulteration because of their high prices. The stable isotope techniques based on measuring the natural abundance of isotope ratios 2H/1H, 13C/12C, and 18O/16O in organic molecules have become the most efficient method to authenticate foodstuffs. The relative abundance of stable isotopes in food from different areas in Poland was measured by the isotopic ratio mass spectrometer Delta Plus, Finningan MAT, equipped with auxiliary accessories, as the difference relative to a standard (Vienna - Standard Mean Ocean Water).

1. Introduction

The chemistry of isotopes experienced a true revival during the 90s. Firstly, in response to the discovery of new experimentally confirmed phenomena new theoretical concepts were proposed, enabling a more efficient approach to the separation set-up design. Secondly, substances of altered isotopic composition ANDRZEJ CHMIELEWSKI, et al. found new practical applications thus becoming desirable products. Stable isotopes found new fields of application, such as medicine, environment protection as well as the areas of science and industry relating directly to the improvement of quality of human life. This work is intended to present some examples of stable isotopes application in environmental research and food authentication.

2. Stable isotopes in environmental studies

2.1. Water resources management

In addition to classical geologic/hydrologic methods, isotopic abundance of 2H, 3H, 13C, 14C, 15N, 18C, 34S is widely applied for investigation of the history and pathway of water in different parts of hydrological cycle. Isotopic content has been employed to determine  the origin and age of different water bodies  the location and proportion of water recharge  the degree of mixing  velocity of groundwater flow

Fig. 1. BEŁCHATÓW the Polish biggest lignite mine. APPLICATION OD STABLE ISOTOPES IN ENVIRONMENTAL STUDIES & FOOD AUTHENTICATION

Among other hydrological and chemical methods, tritium analysis and methods based on measurement of isotopic ratio of 2H/1H , 34S/32S and 18O/16O in 2- SO4 ions are used for monitoring and prognosis of the ground water quality in the vicinity of Belchatow lignite mine [1]. This is the biggest Polish open mouth mine, and with a new proposed expansion (the Szczercow field) will be in operation for the next 50 years. The general scheme of the region is presented in Fig. 1. The large salt deposit lies between the fields. Ground waters are pumped to allow exploitation of the mine. The main physico-chemical features as well as micro and macro components and environmental isotope concentrations were measured in the surface and ground waters in the hypothetical strip interaction region. It has been found that the outfall of mine pumped waters to the Widawka river do not spoil water quality, which preserves the first class of purity in the course between Ruszczyn and up to the Warta river. The forecast of the salinity increase for ground waters pumped by the protection barrier of salt deposit Debina have been worked out for water table altitude = 50.0 m below the sea level (state in December 2000). The range of the wet ash deposit interaction on water quality pumped by the Belchatow mine drainage system have been determined and evaluated.

2.2. Determination sulphur isotope ratio (34S/32S) in coal combustion process.

2- Atmospheric sulphur compounds e.g. SO2 and SO4 originate from coal combustion, volcano eruption or are produced by sea microorganisms. Measurements of 34S/32S in the samples are a useful way to distinguish the sources [2] of pollution. Intensive researches concerning analyses of sulphur isotope ratio in coal and different combustion streams (gases, desulphurisation product) are going on [3]. The aim of the work is determination of sulphur isotope composition in products of coal combustion process and application of sulphur isotopes ratio (δ 34S) as an environmental tracer. There are two main tasks of this work. The first is characteristic of sulphur isotopes composition in Polish coals from Upper Silesia and Lublin. Preliminary results shows, that sulphur in coal has a different isotopic composition (Tables 1 and 2) and occurs in many different forms (pyrite sulphur, sulphate and organic sulphur). Three samples from Sosnica Mine were taken from different depths (Table 2). There is a big differentiation not only between the concentration of the sulphur, but also between the composition of this element in source materials. The chemical compounds separation and determination of isotope composition may provide an information concerning the era and mechanism of sulphur incorporation in organic-rich sediments. The stable isotope composition of sulphur compounds of industrial origin present in atmosphere, biosphere, hydrosphere, groundwater, soil, etc., may differ from natural analogues. The analysis of stable isotope of sulphur is the only method to distinguish anthropogenic and natural source of sulphur. ANDRZEJ CHMIELEWSKI, et al.

Table.1. Sulphur isotopes ratio for sulphur present in Polish coals

Coal mine S[%] 34S[%] Pyrite sulphur Organic Sulphate sulphur sulphur Bogdanka 1.23 1.29 -2.50 -1.95 Kazimierz Juliusz 0.79 6.37 6.18 7.27 Chwalowice 0.81 1.97 3.85 1.19 Jankowice 0.64 0.33 15.88 - Slask 0.74 10.50 4.40 13.71 Sosnica 2.06 -6.62 4.66 -1.88 Belchatow* 0.30 - 9.37 - *lignite

Table 2. 34S of coals from the Sosnica Mine

Total Sulphur content S[%] 34S[%] S[%] Pyrite Sulphate Organics Pyrite Sulphate Organics 0.51 0.36 0.08 0.07 4.05 4.08 4.29 0.75 0.37 0.03 0.35 7.32 10.88 9.71 2.06 1.28 0.10 0.68 -6.62 -1.88 4.66

The technique may be used for: - monitoring of water; - investigation of gypsum dissolution; - investigation of ashes leaching; - investigation of deposition of sulphur from gases after desulphurisation process;

3. Stable isotopes in food authentication

Natural products such as wine, spirits, fruit juices, flavours, oils, and honey are prime targets for fraudulent adulteration because of their high prices. Traditional analytical methods like HPLC, GS and GC-MS make possible the identification and quantification of all the major molecules present, but more sophisticated analytical methods are required to detect whether natural ingredients have been mixed with similar materials from cheaper (synthetic) sources. Stable isotope composition is an important tool for food authenticity and control of the APPLICATION OD STABLE ISOTOPES IN ENVIRONMENTAL STUDIES & FOOD AUTHENTICATION origin. It allows detecting the origin from a geographic point of view or from the point of view of the production processes. The measurement of various isotopic ratios (hydrogen, oxygen, carbon and nitrogen) in different fractions of a product often enables the characterisation of the origin of starting materials. The isotopic fractionation of those elements in the environment undergoes complex patterns allowing to establish the correlation between the food (fruits, vegetables etc.) and raw materials (water and CO2). The aim of the study is to find the relationship between isotope composition of different sorts of food and its geographical origin and to compare the data from different regions of Poland.

The samples are received directly from a producer. Stable isotopic composition (18O/16O, 13C/12C, 15N/14N and D/H ) was measured for food (apples, tomatoes, potatoes, champignons and red beet) from different region of Poland. The collected data gives a possibility to find the relationship between time and place of origin and isotope ratio.

Fig.2. Block diagram of the sample preparation and measuring arrangement. EA - Elemental Analyzer, GB - GasBench II, HD - H/Device, CF -ConFloIII, IRMS - Isotope Ratio Mass Spectrometer

The composition of water present in the food was tested. Hydrogen was measured by H/Device and oxygen isotope ratio by Gasbench II (both instruments connected with mass spectrometer). For the comparison the water samples from the region of plant growing was collected and measured. In this study for measurements of carbon and nitrogen composition in food, we use our new ANDRZEJ CHMIELEWSKI, et al. instrument Elemental Analyser coupled with mass spectrometer (Fig.2). Fig.3 shows the places where samples were collected. The results of measurements of stable isotope composition 18O/16O 13C/12C, 15N/14N, D/H and geographical origin of tested food: apples, potatoes, tomatoes, red beet and champignons are presented at the Figures 4 and 5.

Fig. 3. Regions of sample collection

water region1 region2 region3 apples

-20

-12 -10 -8 -6 -4 -30 -2 -40 H 2

t -50 l e

d -60

-70 -80

delta 18O

Fig. 4. Relation between D and 18O in water and food samples APPLICATION OD STABLE ISOTOPES IN ENVIRONMENTAL STUDIES & FOOD AUTHENTICATION

apples region1 region2 region3 champignons

20 N

5 10 1

a t l

e 0 d -32 -27 -22 -10 delta 13C

Fig. 5. Relation between 15n and 13C in water and food samples

4. Conclusions

The isotope ratio analysis seems an efficient tool for environmental monitoring. It can be used to predict the ground water quality in industrially devastated regions and as a tracer to track the products of the combustion of particular coal. The new field of application of this technique is food quality control and food authenticity confirmation. The detection of frauds by analysis of the isotopic composition of the food is a well-established technique for a range of substances, but it still requires a huge effort to spread its applications. Isotopic methods become a reliable tool for checking the compliance of goods with and international regulations and several isotopic methods have already been included as a official standards for food quality and authenticity control.

Refereneces

1. Sołtyk W., Owczarczyk A., Walendziak J ., Methods of monitoring and prognosis of ground water quality changes in the region of power-mine complex „Belchatów” 2001, INCT Report 2/2001, Warsaw, 34 pp. 2. Andrews J.E., Brimblecombe P., Jicklus T.D., Liss P.S ., An Introduction to Environmental Chemistry, WNT, Warszawa, 1999 (Polish Edition). 3. Chmielewski A. G., et al., (2002), Sulfur isotope composition of Polish coals, Nukleonika, 47, 569-570.