Maryam Yousefifard; A. Jafari
Abstract
Introduction: In recent decades, industrial and technological advancements have led to the gradual increase of heavy metal concentrations. As such, this phenomenon of heavy metals being present in the environment at high concentrations causes deleterious effects on various terrestrial creatures and human ...
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Introduction: In recent decades, industrial and technological advancements have led to the gradual increase of heavy metal concentrations. As such, this phenomenon of heavy metals being present in the environment at high concentrations causes deleterious effects on various terrestrial creatures and human beings. Mercury (Hg) is one of the most toxic elements and can cause renal and neurotoxicity to humans and wildlife. It has been identified as a priority toxic substance in many countries. It is, however, rare to find information on Hg in soils from industrialized areas of Iran in literature. In order to ascertain the distribution of Hg, as well as the extent of contamination with Hg, and to provide policymakers with remediation measures for the affected soils, a study of surface soils was conducted in areas around of Kerman cement plant.
Materials and Methods: Soil samples were collected from the depth of 0 to 20 cm. 103 samples were taken and analyzed. Mercury concentration in soil samples were determined by atomic adsorption method coupled Graphite furnace. Statistical analysis and indices calculation were performed by SPSS and EXCEL, respectively, and distribution maps were prepared by kriging method in ArcGIS software. For evaluating pollution, Geoaccumulation index, enrichment factor and contamination factor were also calculated and interpreted.
Results and Discussion: The mercury concentration in soil samples ranged from 6.70 to 340.96 μg/kg, with a mean value of 164.06 μg/ kg. Mercury is naturally present in very low concentrations in the soil. The concentration of this element in soils ranges from 0.01 to 0.5 mg/kg around the world. The average Hg concentration in the earth crust is reported to be 80 μg / kg. In soils of the study area, the Hg concentration was higher than most of the reported values for soils worldwide and earth crust. This indicates that industrial activities have increased the concentration of mercury in the soil. In fact, the concentration of mercury more than the amount of earth crust indicates the onset of contamination due to various anthropogenic activities. The coefficient of variation of mercury concentration in the soil was 55%, which shows a high variability (CV≥ 35%) according to the classification proposed by Wilding et al. (19). The high variability coefficient shows the heterogeneous and non-uniform distribution of the property. Therefore, there is a high concentration of mercury in some areas of the study region. In other words, soil was affected by external factors in some areas. Based on the cleaning standards of soil for mercury in soils used for industrial purposes in some countries, all soil samples in the studied area have a much lower concentration of mercury than standard values. In other words, although the activity of the cement plant has increased the concentration of mercury in the soil, it can continue its industrial activity. The plant’s managers should, however, take a close look at the release of this metal and other pollutant. According to the results derived from Igeo, Hg was graded as unpolluted to moderately polluted. Low levels of contamination (CF <1) to significant contamination (3.00 ≤ CF <6.00) of mercury were observed based on the contamination factor. The results suggest that anthropogenic sources control the concentration of mercury in the soil. The average contamination factor more than one (CF> 1) indicates that the soils of this region have been exposed to mercury contamination. Spatial distribution map indicates that the highest concentration of mercury in the soil is between 200 and 341 μg/kg, which was observed around the factory and south-east of the region. Release of mercury in the environment is related to natural processes and human activities. Mercury release due to human activities is mainly due to combustion of fossil fuels, iron ore processing, steel industry and cement plants. Considering the high concentrations of mercury in the southeastern part of the region, the lower part of the plant, it seems that environmental factors such as the topography of the area may affect its distribution. The high concentrations of Hg were observed at low elevations, on the south side, and over the areas with relatively low slope gradients.
Conclusion: The results demonstrated that the concentration of Hg was higher than most of the reported values for soils worldwide and earth crust. This indicates that industrial activities have increased the concentration of mercury in the soil. According to the results derived from Igeo, Hg was graded as unpolluted to moderately polluted. In addition, the level of contamination was identified to be low to high, based on the contamination factor (CF). The spatial distribution map of the total concentration of mercury shows that the highest concentration of mercury was observed around the factory and to the south and southeast of the region. The high concentrations of this metal were at low elevations and on the south side of the catchment and in areas with relatively low slope gradients. It is concluded that although the concentration of this pollutant is not critical in the study area, due to the close proximity of the industrial area to the residential area, planning to control the release of this metal and other pollutants should be seriously considered.
rouhollaah vafaeezadeh; shamsollah Ayoubi; mohamamdreza mosaddeghi; maryam yousefifard
Abstract
Introduction: Land use changes are the most reasons which affect natural ecosystem protection. Forest soils have high organic matter and suitable structure, but their land use management change usually affects soil properties and decreases soil quality. There are several outcomes of such land use changes ...
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Introduction: Land use changes are the most reasons which affect natural ecosystem protection. Forest soils have high organic matter and suitable structure, but their land use management change usually affects soil properties and decreases soil quality. There are several outcomes of such land use changes and intensification: accelerated soil erosion and decline of soil nutrient conditions, change of hydrological regimes and sedimentation and loss of primary forests and their biodiversity. Establishing effects of land use and land cover changes on soil properties have implications for devising management strategies for sustainable use. Forest land use change in Yasouj caused soil losses and decreased soil quality. The objectives of this study were to assess some soil physical and chemical properties and soil magnetic susceptibility changes in different land uses and slope position.
Materials and Methods: Soil samples were taken from natural forest, degraded forest and dryland farm from different slops (0-10, 10-20 and 20-30 percent) in sout east of Yasouj. They were from 0–10 cm depth in a completely randomized design with five replications. Soil moisture and temperature regimes in the study area are xeric and mesic, respectively. Particle size distribution was determined by the hydrometer method and soil organic matter, CaCO3 equivalent and bulk density was determined using standard procedures described in Methods of Soil Analysis book. Magnetic susceptibility was measured at low and high frequency of 0.46 kHz (χlf) and 4.6 kHz (χHf) respectively with a Bartington MS2D meter using approximately 20 g of soil held in a four-dram clear plastic vial. Frequency dependent susceptibility (χfd) is expressed as the difference between the high and the low frequency measurements as a percentage of χ at low frequency.
Results and Discussion: Soil texture was affected by land use change from silty clay loam in forest to silty loam in dry land farm. Declining of organic matter and aggregate stability caused soil surface loss by erosion. The bulk density increased from 1.12 to 1.54 gcm-3 when forest changed to dry land farms. Soil compaction by tillage and lower amount of organic matter in farm lands are some of the reasons for increasing bulk density. Another possible reason could be decreasing of biological activity and parent material with greater calcite mixed with soil surface layer during land use change. Thus, the maximum and minimum amount of calcite was observed in dry land farm in 20-30 % slopes (57.46 %) and forest in 0-10 % slopes (13.37 %), respectively. In addition during soil formation calcite was translocated to lower horizons in natural forest. The greatest organic matter was 7.45 % and related to natural forest in 0-10 % slopes. Overall, the organic matter content was greater in all forest slopes than all other land use. In mineral soil, total organic carbon is not a proper factor in soil physical behavior. Complex and noncomplex organic carbon influence the soil physical behavior. Organic carbon in degraded forest and dry land farming was in complex form but in forest land use it was observed in two complex and noncomplex forms. Noncomplex organic matter was 53% and complex organic matter was 47%. It means that forest soil have better quality than degraded forest and dry land farm, respectively. Sedimentary rocks have rather low concentration of magnetic minerals with magnetic susceptibility from 0.1 (10-8 m3 kg-1) in the limestone to approximately 20 (10-8 m3 kg-1) in the siltstone. Low magnetite susceptibility in natural forest was more than degraded forest and dry land farm. Mean magnetite susceptibility values were 61.8, 48.6 and 42.4 10-8 m-3 kg-1, respectively which probably related to magnetic minerals formation during pedogenesis. Frequency magnetite susceptibility (χfd) was more than 3% in the most soils, significantly in forest soil (from 4.63-5 percent). Greater frequency magnetite susceptibility (χfd) values are suggested to be indicative of the dominance of super-paramagnetic grains and fiug single domain particles. χfd in soils reflects significant pedogenic magnetic minerals which formed during soil formation from calcitic parent materials.
maryam yousefifard; shamsollah Ayoubi; A. Jalalian
Abstract
This study was conducted to assess different chemical weathering indices and to evaluate the weathering rates of soils developed on volcanic (hornbelende andesite, pyroxene andesite and dacite) and plutonic (alkali granite, granodiorite, monzodiorite, syenite and pyroxene diorite) igneous rocks in the ...
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This study was conducted to assess different chemical weathering indices and to evaluate the weathering rates of soils developed on volcanic (hornbelende andesite, pyroxene andesite and dacite) and plutonic (alkali granite, granodiorite, monzodiorite, syenite and pyroxene diorite) igneous rocks in the northwestern Iran. Representative soil profiles were described and soil samples were collected and analyzed for selected chemical and physical properties. Total concentrations of major elements and trace element (Zr, V, Ti and Y) were determined with ICP-OES and ICP-MS, respectively. Significant correlation coefficients were obtained between soil properties (clay percent, pedogenic iron and bulk density) and Ba, B/A, B/R, CIA, CIW, PIA, PWI and the WR chemical weathering indices. These indices are based on the ratio of a group of mobile oxides to one or more immobile oxides and are suitable for explaining the weathering rate of the soils developed on igneous rocks in this semiarid region. A-CN-K and MFW ternary plots showed that the soils developed on volcanic rocks (hornbelende andesite> pyroxene andesite> dacite) were more weathered than those on the plutonic parent rocks (alkali granite, granodiorite, monzodiorite, syenite, pyroxene diorite). Ba and CIA weathering indices predicted weathering trend such as MFW ternary plot, and it seems these two weathering indices are the most suitable weathering indices after W index (or MFW ternary plot) in this semiarid region. Ca, Na and K elements are presented in chemical weathering formulas of these two indices. These elements are in the feldspar minerals structures which are the most mineral in the earth crust.