zahra sharifi; Alireza Astaraei; A Fotovat; mojtaba baranimotlagh; Hojat Emami
Abstract
Introduction: Zinc is one of the essential micronutrients for plants, mining and industrial activities leading to pollution of heavy metals, including zinc metal contamination in soils. In addition to the total concentration, knowledge of the Zinc fractions is necessary to assess the mobility of zinc ...
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Introduction: Zinc is one of the essential micronutrients for plants, mining and industrial activities leading to pollution of heavy metals, including zinc metal contamination in soils. In addition to the total concentration, knowledge of the Zinc fractions is necessary to assess the mobility of zinc in the soils. One of the sequential extraction methods is Tessier method. sequential extraction with plant cultivation simultaneously, is the appropriate approach for assessing the mobility of toxic metals. Therefore this study was conducted to evaluate the chemical forms and determine their relationship to the physical and chemical properties of soils in some fields under cultivation in Khorasan Razavi province.
Materials and Methods: The experiment was conducted in a completely randomized design with factorial arrangement includes 4 levels of contamination (0, 500, 1000 and 1500 (mg/kg)) and 10 soil types from different regions of Khorasan Razavi province of 0-30 cm depth in the range of electrical conductivity 1 up to 15 ds/m, with three replications at Research greenhouses of Ferdowsi University of Mashhad. An example of mining waste was prepared as a source of pollution. The soil samples were kept at field capacity moisture for 6 months. Then air-dried soil samples were used for planting borage and determine the Zinc fractions. Then soil samples were air dried and used for planting borage and determining the Zinc fractions. Texture, cation exchange capacity, organic carbon, electrical conductivity, pH and Available phosphorus and potassium were measured in the saturation extract. DTPA-extractable Zinc was measured by atomic absorption spectrometry. Borage was planted in greenhouses in 3 kg pots with three replications. During flowering, the plants were harvested and dry digestion method was used to measure the concentration of Zinc. Chemical forms and Pseudo total concentration of zinc in the samples were determined using Tessier and digestion by HCl and HNO3 acids (3:1) methods respectively. The concentration of the extracts was measured by atomic absorption spectrometry. Statistical analysis was done using Minitab and Excel softwares.
Results and Discussion: Chemical Forms Average of zinc in soils was as follows:
Exchangeable < iron and manganese oxides < organic < carbonate < residual
Despite the low percentage of organic matter in these soils, in high levels of Zinc contamination a large amount of zinc was saved. Lack of organic Zinc, in addition to the low amount of organic matter soil is related to the dominance of iron oxides. In high levels of soil contamination, increased concentrations of zinc in all fractions, especially organic and carbonate which leads to an increase in the availability of zinc, is a serious threat to environment. The amount of exchangeable zinc was insignificant. Also the exchangeable, forms a small part of total amount of metal in the soils. The correlation between the chemical forms with each other and with the pseudo total, absorbed by plant roots and shoots and extracted with DTPA together, was significant. Absence of correlation between the exchangeable and iron and manganese oxides is probably indicative of the fact that the main supplier of soluble and exchangeable zinc normally after carbonates are iron and manganese oxides, that have little role in these soils. There is a significant positive correlation between different fractions of zinc with each other and this indicate a dynamic relationship between the zinc chemical forms in the soil. Correlation coefficients between plant available and chemical forms of zinc showed that plant available zinc derived from all fractions. A higher correlation coefficient between the plant available with carbonate and organic zinc was obtained, which indicates that carbonate and organic are the major suppliers for available plants zinc.
Conclusion: In this study, the residual, carbonate and organic fractions are dominant form of zinc in soils, respectively. With increasing level of contamination, percentage of residual zinc decreased and percentage of other fractions increased, particularly organic and carbonate. Increasing the availability of zinc, is a threat to the environment. There is a high correlation coefficient between different fractions of Zinc with each other and with the pseudo total, amount of plant and available plant zinc showed that there is a dynamic relationship in the soil systems. There is a higher correlation coefficient between the available zinc and carbonate and organic fractions of soils, which indicate available plant zinc, are mainly derived from carbonate and organic fractions.
alireza hosseinpuor; H.R. Motaghian
Abstract
The amount of available micronutrients such as zinc (Zn) is a primary concern in treated soils with sewage sludge. This study was performed to evaluate Zn availability (DTPA-TEA, Mehlich 1 and Mehlich 3) and its fractionation in soils before and after treated with sewage sludge (1% w/w) and after wheat ...
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The amount of available micronutrients such as zinc (Zn) is a primary concern in treated soils with sewage sludge. This study was performed to evaluate Zn availability (DTPA-TEA, Mehlich 1 and Mehlich 3) and its fractionation in soils before and after treated with sewage sludge (1% w/w) and after wheat plantation in greenhouse conditions. The results of this study showed that mean of Zn extracted by using chemical extractants after sewage sludge application increased significant (P0.05). The results of fractionation showed that residual Zn, exchangeable Zn, Zn associated with organic matter, Zn associated with iron-manganese oxides, and Zn associated with carbonates increased 11, 26, 94, 172, and 279% respectively. The results of mean comparison showed that different between mean of Zn fractions (except Zn associated with iron-manganese oxides) before and after planting was significant (P
