«Zane Vincēviča-Gaile IMPACT OF ENVIRONMENTAL CONDITIONS ON MICRO- AND MACROELEMENT CONTENT IN SELECTED FOOD FROM LATVIA Summary of doctoral thesis ...»
2.2.2. Element speciation analysis Speciation analysis of studied soil samples was performed to detect bioavailability of elements in food chain segment soil-plant. Speciation analysis was done by fractioning by extracting 5 fractions of compounds: 1) fraction of water soluble metal forms; 2) fraction of acid soluble forms of metals; 3) fraction of reduced forms of metals; 4) fraction of organic bound forms of metals; 5) fraction of insoluble forms of metals, mostly bound with sulphides (Arthur et al., 2007; Malandrino et al., 2011; Tessier et al., 1979). Consequent extraction step by step was performed as shown in Figure 2.9.
Schematic overview of fractioning analysis 19 To assess the element bioavailability in food chain segment soil-human fractioning was done by extracting 3 fractions of compounds: 1) fraction of water soluble metal forms;
2) fraction of acid soluble forms of metals; 3) fraction of reduced forms of metals (Arthur et al., 2007; Malandrino et al., 2011; Tessier et al., 1979).
Sample solutions of every fraction were analysed to quantify element concentration with atomic absorption spectrometry and inductively coupled plasma mass spectrometry.
3.1.1. Impact of seasonality on element concentration in food Impact of seasonality was assessed taking into account detected element concentration in cottage cheese samples and hen egg samples.
Cottage cheese. Samples of cottage cheese were collected over two seasons, spring/summer and autumn/winter. Concentration of macroelements, especially Ca and K, was detected higher in samples from winter season (Figure 3.1.) that can be associated with seasonal distinctions in dairy cattle breeding conditions and feeding.
Figure 3.1. Average concentration of elements in cottage cheese depending on season
Higher concentration of microelements (e.g., Cr, Mn, Cu, Zn) can also be referred to samples collected in winter season. However, some elements such as Fe, Ni and Pb are detectable in higher concentration in samples from summer season. That can be associated with influence of environmental factors such as airborne particle deposition on grassland near roads or railway, e.g., particles containing Pb and Ni can become contaminants of food chain.
Seasonality of dairy cattle breeding differs especially due to different feeding regime – feed used in winter is more enriched with vitamins, micro- and macroelements but in summer cattle can be fed on grassland and is likely exposed to possible environmental pollution impact.
Hen eggs. Hen egg samples for seasonality assessment were collected each month from April, 2011 to March, 2012 in a courtyard farm at Aizkraukle (Latvia) with known poultry breeding conditions: in spring and summer season birds were kept in free-range conditions outdoors with possibility to find feed and as additional feed grass, vegetables and grains were fed; in autumn and winter season birds were kept in a shelter and fed with ready-to-use combined poultry feed and grains. Whole egg, egg yolk and egg albumen samples were analysed. In overall, it was detected that higher concentration of microelements (e.g., Cu, Fe, 20 Zn) is detectable in egg samples collected in summer or spring season (Figure 3.2.). The exception is Se which can be found in higher concentration in samples collected in winter. In addition, in egg yolk Se was quantified only in samples from winter season that can be associated with impact of seasonality as soils of Latvia contain very low Se content (Zegnere and Alsina, 2008). This can explain lowered Se concentration in egg samples from summer and spring season when birds are fed outdoors and consume soil, mesobiota and plants.
Similarly as found for cottage cheese sample also in egg samples higher concentration of macroelements can be attributed to the samples derived in winter season which is connected with poultry breeding and feeding seasonal distinctions.
3.1.2. Impact of botanical origin on element concentration in food It was possible to assess the impact of botanical origin on element concentration in food after the analysis if honey samples. Honey samples were divided in 7 groups according to their botanical origin: 1) polyfloral not defined honey (ns=33); 2) heather and forest blossom honey (ns=16); 3) rape and spring blossom honey (ns=5); 4) buckwheat and clover species honey (ns=9); 5) linden honey (ns=6); 6) meadows blossom honey (ns=8) and
7) commercially manufactured honey mixtures with unknown botanical origin (ns=3).
To detect also the impact of pollution attention was paid in detection of potentially toxic elements. The analysis of honey samples collected in Latvia revealed that in overall potentially toxic elements can be quantified in the following sequence: Zn Al Cu Ni Cr Pb Co Cd As (based on mean results, ns=80). The overall list of metals detected leads to think of possible contamination at storage and processing as, e.g., Al, Cu, Ni and Zn are the ordinary constituents of metallic household and kitchen equipment (Joudisius ir Simoneliene, 2009).
Taking into account the botanical origin of honey collected in Latvia significant differences in concentration of potentially toxic metals were detected among the species.
According to mean values of quantified potentially toxic metals possible honey contamination by honey type can be ranged as follows (from higher to lower element content): commercially manufactured honey mixtures with unknown botanical origin heather / forest blossom honey polyfloral honey meadows blossom honey linden honey buckwheat / clover honey rape
Concentration of Zn, Al, Pb and Cd in honey samples of different botanical origin Impact of botanical origin on element concentration can be connected with environmental factors. For example, such elements as As and Pb are found in higher concentration in linden blossom honey that knowing that linden trees are common part of urban greenery and therefore can be exposed to contamination by dust and airborne particles from roads, railroad and exhaust fumes from transport and industry. But rape or buckwheat blossoms and, respectively, element content in honey, can be affected by applied agriculture practice, use of agrochemicals and fertilizers. However, higher detected concentration of microelements in honey mixtures of unknown origin can be associated with inappropriate use of equipment (e.g., containing metal alloys) for honey preparation.
3.1.3. Impact of agricultural practice on concentration of elements in food The impact of agricultural practice on concentration of elements in food was assessed analysing data of root vegetables, cottage cheese and hen eggs.
Root vegetables. Knowing origin and applied agricultural practice in growth of root vegetable samples onions and carrots, it was possible to detect differences in element concentration for vegetables grown under the different agricultural conditions. Statistical analysis of the data by using Fisher’s criteria and appropriate t-tests allowed comparison of vegetable samples grown in different agricultural conditions, i.e., divided by subgroups of samples grown in farmlands versus samples grown in allotment gardens. Regarding the analysis of onion bulbs, significant differences between the mentioned subgroups were detected for several microelements. Sr, Ni, Cd, Se and Co were the elements the amounts of which were significantly higher in onions grown in farmlands, while Rb was the only single element which was detected in higher amounts in onions grown in allotment gardens. But the analysis of subgroups of carrots revealed a significant difference only for the three microelements: carrot samples grown in allotment gardens were significantly richer in Zn, Mn and Rb. These coherences purport the fact that farmlands are more likely influenced by possible contamination sources, mainly such as agrochemical impact that can result in 22 increased amounts of potentially toxic metals in vegetables, but the microelement analysis of vegetables grown in rural allotment gardens may reveal possible influence of geochemical background.
Farmlands can be affected by agricultural activities such as the use of fertilizers and pesticides much more intensively than allotment gardens, while private allotment gardens most frequently are small and located close to the roadsides and urban areas, as well as can be situated within cities and towns near industrial territories or on recultivated contaminated lands that can negatively influence air, soil and water conditions in gardens. Within the current research elevated concentration of potentially toxic elements was not detected for samples derived in allotment gardens; that is associated with sample collection in rural areas where risk of contamination is likely to be less.
Hen eggs. Data of hen egg analysis revealed differences among element concentration in samples derived from organic farms, domestic farms and large-scale poultry farms. For example, in egg samples from organic farms higher concentration of Cu, Fe, Mn, Pb and Zn (Figure 3.4). But Pb was not detected in any of samples derived from poultry farms.
Concentration of Fe, Zn, Cu, Mn, Pb and Se detected in hen egg samples from different poultry housing types In all cases the highest mean values of elements were determined for egg samples derived from organic farms, while element content of eggs from domestic farms and poultry farms was lower and relatively similar. As it is known that organic farming is strictly controlled and use of chemicals is restricted within this agricultural practice (EC Regulation 889, 2008), the results detected in the present study could not be associated with possible avian feed pollution of agricultural or veterinary chemicals, but might be connected with the impact of environmental factors on element content of egg samples, likely in relation to potential environmental contaminants (e.g., Cu, Pb, Zn).
23 3.2. Assessment of element bioavailability
3.2.1. Characteristics of soil samples To assess element bioavailability the experiment with selected food crops was done using five different soil samples: S1 – fen peat soil; S2 – sod-podzolic soil / sandy loam; S3 – sod-podzolic soil / sand; S4 – sod-podzolic soil / loamy sand; S5 – sod-podzolic soil / sandy clay loam (FAO, 2006; Kārkliņš u.c., 2009; Nikodemus, 2011; Noteikumi 804, 2005).
Higher pH was detected for soil S1 (pHH2O 5.31 / pHKCl 5.06), but the lowest for S5 (pHH2O 4.61 / pHKCl 5.11). Content of organic matter varied from 2.9 % to 4.2 % in mineral soil samples (S2-S5), but the lowest was detected for fen peat soil (S1) – 29.3 %. Cation exchange capacity (CEC) or cation base saturation (CBS) in great extent is dependent on soil pH. CBS in mineralsoils (S2-S5) detected 3.13-8.17 cmol/kg but in fen peat soil (S1) –
142.29 cmol/kg. Ca2+ content was 70.9 % of CBS for sod-podzolic soil / sandy clay loam (S5), but for fen peat soil (S1) 87.5 % of CBS, that indicates that selected soil samples are of high fertility and are applicable for crop growing (Hodges, s.a.). Total element content before soil contamination is summarized in Table 3.1.
Concentration of elements in studied soil samples prior contamination
Sod-podzolic soil / sandy clay loam (S5) contained higher concentration of Cr, Ni and Pb compared with other soil samples that can be associated with element adsorption on clay particles as this sample is richer with clay. Significant correlation (r0.8) was detected for such element pairs: Zn with Ca, Co, Cr, Fe, K, Ni, Mg; K with Cu, Pb; Ca with Co, Mn.
After soil contamination with CuSO4×5H2O solution in different target concentration (40, 70, 100, 130 un 200 mg/kg) or with Cd, Cu, Pb and Zn salt solution mixture the hyperaccumulation of some elements was observed, especially in fen peat soil (S1) (Table 3.2.).
3.2.2. Accumulation of elements in experimentally grown vegetables In contaminated soil samples such food crops as leafy lettuce Lactuca sativa, dill Anethum graveolens and radish Raphanus sativus were grown. To detect the element transfer and accumulation intensity from soil to plants the transfer factor (TF) was calculated. Higher TH values (10) were gained for Zn transfer in mineral soils (S1-S4) to lettuce, while lower TF is attributed to soil with higher content of organic matter, e.g., fen peat soil (S1). Addition of humic substances diminishes element transfer from soil to plants as well (Table 3.3).
Transfer factors (TF) for lettuce and radish samples grown in soils contaminated with salt mixture containing Cd, Cu, Pb and Zn
Among elements the lowest TF were calculated for lead. In overall higher TF values can be attributed to element transfer from soil to plant roots than to foliage. Data revealed that multielement contamination in soil increases the intensity of element accumulation in plants, e.g., interaction among Cu, Cd, Pb and Zn can intensify copper accumulation in lettuce for 31.4 %, if compared with monocontamination. Addition of humic substances can diminish element accumulation for 90 % in leafy vegetables (e.g., lettuce) and for about 25 % in root vegetables (e.g., radish).
3.2.3. Element bioavailability in food chain segment “soil-plant” Element bioavailability assessment was done after the sample fractioning analysis. In overall it was detected that differences in element concentration among the fractions can be comparable for fen peat soil (S1) and mineral soil samples (S2-S5). Higher amount of elements is bound in the fraction of reduced forms of compounds in soils S1 and S4, 41 % and 35 %, respectively, soil samples richer in organic matter (Figure 3.5.).
Greater part of elements incorporated in sulphide compounds refers to soil S3 (39 %).