EVALUATION THE MICROELEMENTS AND HEAVY METALS CONTENT IN THE CONDITIONS OF SOME AGRICULTURAL AND FOREST LANDS

. The study analyzed and evaluated the content of some microelements and heavy metals in the conditions of two categories of agricultural and forest land. The study location was in the "Padurea Cenad" Protected Area and the bordering agricultural area, Timis County, Romania. Among microelements, the content of iron (Fe, ppm), manganese (Mn, ppm), copper (Cu, ppm) and zinc (Zn, ppm) was analyzed


INTRODUCTION
The regime of microelements in the soil, in relation to plant nutrition, depends on a series of influencing factors (eg soil reaction, organic matter, electrical conductivity, antagonistic mineral elements, water and air regime, microbiological activity etc.), in relation to the type of soil, ecological and technological conditions in the case of cultivated lands (Jacoby et al., 2017;Dhaliwal et al., 2019).
In the case of natural ecosystems, such as the forest ecosystem, the content of microelements varies in relation to the type of soil, the type of predominant tree vegetation, orographic conditions, ecological conditions, etc. (Karunakar et al., 2015;Lasota et al., 2020).
In the case of cultivated lands, the content and regime of microelements in the soil depends on the type of soil, but to a large extent it depends on the agricultural system and plant culture technologies, respectively of anthropic influence (Tkaczyk et al., 2017).
In the conditions of some areas located near water courses, the flood zone, associated with flooding phenomena, the soils have registered changes in terms of quality indices and productive potential, through aluvial deposits and periodic accumulations of dissolved elements or contained in sediments (Brémond et al., 2013;Patel et al., 2021;Wang et al., 2022).
Both in the case of agricultural and forest lands, anthropogenic activities can influence the content of mineral elements, the physicochemical and biological properties, respectively the quality of the soils (Novák et al., 2020;Santorufo et al., 2021;Sur et al., 2022).
For the assessment of soils and lands, in agricultural or natural ecosystems, both classical methods, based on soil samples and laboratory analyses, as well as alternative methods, based on imaging, were used (Syso et al., 2014;Govedarica et al., 2015;Popescu et al., 2020).
Through appropriate methods and representative indices, the soils and lands in the peri-urban and urban areas were studied for the characterization of the respective ecosystems, in relation to the anthropic influences (Datcu et al., 2017;Calzolari et al., 2020).
Knowing the content of microelements in agricultural soils is important for establishing fertilization plans, appropriate methods and techniques for applying fertilizers with microelements for the purpose of high efficiency ( This study was carried out on two categories of land (agricultural and forestry), where the content of some microelements and heavy metals was analyzed, but also for the characterization of the soil based on quality indices.

MATERIAL AND METHODS
In the "Padurea Cenad" Protected Area region, Timis County, Romania, the study evaluated the content of some microelements and heavy metals in the soil in two categories of land, agricultural and forest.
The soil samples were collected from representative plots, on agricultural land (field crops, conventional technologies, non-irrigated system) and forest land.
In relation to the purpose of the study, the content of iron (Fe, ppm), manganese (Mn, ppm), copper (Cu, ppm), zinc (Zn, ppm), as well as some heavy metals, chromium (Cr , ppm), nickel (Ni, ppm) and lead (Pb, ppm) were considered to analysis. The soil samples were analyzed in the Timisoara OSPA Laboratory, using accredited laboratory methods.
The values of the microelements and heavy metals content were analyzed through appropriate mathematical and statistical methods, in relation to the proposed study. The ANOVA test was used to evaluate the presence of the variance in the obtained data, and to quantify the statistical certainty.
To evaluate the interdependence between the values of the content of microelements and heavy metals, correlation analysis was used, based on statistical safety parameters (p < 0.05; p < 0.01, p < 0.001).
The level of variability was assessed through the coefficient of variation (CV), as well as through the graphic method (diversity profile).
The PCA analysis was used to quantify the level of contribution of the main components in relation to the variance, for the characterization of the two categories of land studied, in relation to the values recorded for the content of microelements and heavy metals.
For the statistical analysis and some graphic representations, the calculation mode from EXCEL and the PAST software (Hammer et al., 2001) were used.

RESULTS AND DISCUSSIONS
The content of microelements and heavy metals (expressed in ppm) resulted from this study and characterization of the two land categories (agricultural, forest) is presented in table 1.
Iron (  From the analysis of the recordet values of the microelements and heavy metals content, through the ANOVA test, single factor (Alpha=0.001), the statistical safety and the presence of the variance in the set of experimental data were confirmed, according to F>Fcrit, p<0.001, table 2. Positive and negative correlations were found between the values of the content of microelements and heavy metals in the two categories of studied lands, with different levels of intensity.
Very strong correlations were found between Fe and Cu (r=0.914), between Fe and Ni (r=0.916), between Mn and Zn (r=0.935), between Mn and Cr (r=0.933), between Zn and Cr (r=0.920), and between Ni and Pb (r=0.990) respectively.
Strong correlation was found between Fe and Pb (r=0.851), and moderate correlations were found between Mn and Ni (r=-0.732) and between Mn and Pb (r=-0.731).
Correlations of lower intensity were also found in the case of other studied elements, the values of the correlation coefficient being presented in table 3. The level of variability of the evaluated soil quality indices values (microelements, heavy metals) was quantified by calculation (coefficient of variation, CV) and by the graphic method (Diversity profiles).
Based  Pb microelements and heavy metals (as biplot) was found at CP1-A and CP2-F. Associated with the content of Mn and Zn and Cr (as biplot) CP2-A was positioned, and associated with Fe, Cu, Ni and Pb (as biplot) CP1-F was associated.

Figure 2. PCA diagram (correlation matrix) for control points (CP), arable (A), forest (F), and the content of microelements, respectively heavy metals (as biplot)
From the analysis of the distribution of the microelements (Fe, Mn, Cu, Zn) and heavy metals (Cr, Ni, Pb) content in relation to the soil reaction and the content of macroelements, published in a previous study (Rosu and Sala, 2022), have certain correlations were recorded, some of which are statistically safe.
Other correlations were also recorded, but of lower intensity and reduced conditions of statistical certainty. Thus, very strong correlations were recorded between Ni and pH (r=-0.938), moderate correlations between Fe and pH (r=-0.721), between Mn and pH (r=0.718) and weak correlations between Zn and pH (r=0.868) and between Cu and pH (r=0.622).
Variable levels of correlations between microelements and soil reaction were also reported in other studies (Mercik et al., 2002;Mohiuddin et al., 2022). Rudawska and Leski (2005) reported low values for the content of macro and microelements in the conditions of some sandy and acidic soils, in low forest areas. The values recorded for the content of microelements and heavy metals in the two soil categories show the great spatial variability of agricultural and forest lands, even within a common study perimeter. The variability of land in natural and agricultural ecosystems is the result of different influencing factors (natural and anthropogenic), and different studies have analyzed and quantified the level of spatial variability through different methods, techniques and models of approach (Mwendwa et al., 2022;Zou et al., 2022).
The content of microelements in the soil, and those provided through fertilization, influenced the growth and development of the vine, the content of mineral elements in the vines, respectively the ripening of the vines shoots (Sala and Blidariu, 2012).
The results obtained in the present study facilitated the highlighting of the differences regarding the content of microelements and heavy metals, and the appreciation of the levels of spatial variability in the two