Evaluation of transfer of heavy metals from the soil into the edible parts of pea and chickpea

Authors: Mária Timoracká 1    Miriama Kopernická 1    Alena Vollmannová 1   
1 Slovenská poľnohospodárska univerzita, Nitra, Slovensko   
Year: 2016
Section: Biotechnology and Food Technology
Abstract No.: 1331
ISBN: 978-80-972360-0-7

Pea is starchy, but high in fiber, protein, minerals and micronutirents. Pea contains about one-quarter protein and one-quarter sugar. Chickpea is rich in protein, polysaccharides and dietary fibre, also rich in minerals, especially calcium, iron, magnesium, phosphorus.It is the one of the highest quality and most digestible leguminous.

Generally, legumes are reported as a good source of minerals and trace elements. Metals, such as iron, zinc and manganese are essential metals, since they play an important role in biological systems, but they can be toxic when taken in excess. Heavy metals such as Pb and Cd rank among substantial environmental pollutants that are very phytotoxic in environment. Ecological risk from accumulation of heavy metals in soil is reflected on soil ability to provide hygienic safe foodstuffs.

The aim of the study was to determine the contents of heavy metals (Cu, Fe, Mn, Cd, Pb, Ni, Co, Cr, and Zn) in the soils and their transfer into dry pea (green cultivars: Jadeit, Achat, Olivín, Nefrit and yellow cultivars: Jantar, Svit, Jasna) and chickpea (cv. Beta, Slovák, Irenka).

Minerals and trace elements– in soil and matter - were determined using a Varian AA240FS atomic absorption spectrometer equipped with a D2 lamp background correction system, using an air–acetylene flame. Total content of risk metals including all of the forms besides residual metal fraction, content of mobile forms of selected heavy metals in soil extract by 1 mol.dm-3 NH4NO3 and 2 mol.dm-3 HNO3 was determined. The sample of pea and chickpea after their drying and decomposition by HNO3 on the microwave digestion were used. The results of soil were evaluated according to the legislative valid in the Slovak Republic and the content of risky elements in legume seeds were evaluated according to the Food Codex of the Slovak Republic.  

Soils from sites from which chickpea and peas were collected (locality Horná Streda) were medium to high humic with extremely acid soil reaction. These were characterized by good to very high magnesium content and high potassium content. Nutrient content determined in soil samples ranged from 2012 to 2100 mg.kg-1 N, 61.8-63.0 mg.kg-1 P, 294-318 mg.kg-1 K, 2725.5-2981.5 mg.kg-1 Ca, 593-612 mg.kg-1 Mg. A background value A for the total risk element content in soil were exceeded for Cd (limit exceeded to 46.6 %), Cu (limit exceeded to 4.76 %), and Ni (limit exceeded to 31.6 %), but in neither case it reached the indicative limit values B ​​established by legislative for soil contamination. Soil with acidic properties to create favorable conditions for the increased transfer of certain forms of elements into plants, so it was important to determine the content of potentially mobilized forms of heavy metals. The contents of potentially mobilizable heavy metals in nitric acid extract (a background A1) did not exceed a limit and fluctuated above allowable concentration, only in case of nickel (Law No 531/1994–540). Nickel may accumulate to toxic levels in soils due to anthropogenic activities. The risky elements contents in ammonium nitrate extract, with the exception of  Pb, did not exceed limit for the maximum levels of chosen risk elements in studied locality (Law No 220/2004). The soils from Horná Streda locality were relatively uncontaminated.

In the green and yellow seeds of pea seeds and also chickpea were the order of the average values of the nutrient content determined as follows: K> P> Mg> Ca. Thus, we can evaluate the variety and type does not affect on the amount of macroelements  in the seeds of leguminous plants.

The heavy metal content did not exceeded the limit for maximum values of selected heavy metals in the investigated varieties of legumes by the Codex Alimentarius of the Slovak Republic, with the exception of zinc (52.95 mg.kg-1, cv. Achat), nickel (7.3 mg.kg-1, cv. Slovák), lead (1.06 mg.kg-1, cv. Beta) a cadmium (cvs. Svit, Slovák, Beta).

The monitoring of heavy metals content mainly in chickpea is very important because in present, mainly due to the low sodium and lipid content, chickpea is enjoying a renaissance in the menu in Slovakia, especially in diabetic, low caloric and gluten-free diet.

This study was supported by the Grant Agency of the Ministry of Education VEGA 1/0308/14.