جستجوی مقالات مرتبط با کلیدواژه « بخش بندی » در نشریات گروه « آب و خاک »

Flooding and drainage cycles affect the biological and chemical characteristics of the soil in paddy fields and play an important role in cadmium (Cd) availability. In this study, the effect of biochar (B), hematite (H), and their simultaneous application (HB) on pH, Eh, and calcium chloride extractable Cd was investigated in a Cd-contaminated soil during a flooding and drainage period. Also, the Cd fractionation at the end of the incubation period was studied. The pH value increased during the flooding period and decreased with the beginning of the drainage period. The Eh value decreased from the beginning of the flooding and showed an increasing trend during the drainage period. Calcium chloride extractable Cd decreased during the flooding period, while at the beginning of the drainage increased with a slight slope and followed a decreasing trend up to the end of the drainage period. Cd concentration reduced at the end of the flooding period in the B, H and HB treatments compared to the control by 16.8%, 20.5%, and 25.7%, respectively. Also, the reduction in Cd concentration compared to the control treatment at the end of the drainage period was 18.2, 23.1 and 28.2% respectively. HB treatment reduced the Cd availability by reducing the soluble and exchangeable fractions and increasing organic, iron, and manganese oxides fractions. The results indicated that the application of amendments can reduce Cd availability in paddy fields and its uptake by the rice plant.

The aim was to evaluate the efficacy of Eisenia fetida soil earthworms in the biological treatment of Lead-contaminated soils in the presence of organic matters. 6 soil samples from zero to 15 cm depth were collected at different distances around the mine and a soil sample (control) was collected from the non-contaminated area. This experiment was investigated as a factorial in the form of a complete randomized block design with first factor of organic fertilizers (cow manure, carrot pulp, vermicompost and control) and the second factor of the presence or absence of earthworms. 12 earthworms weighing between 0.3 and 0.6g were selected for each soil sample (300g). For 42 days, the worms were exposed to lead-contaminated soils with a concentration of 133.19 to 13250 mg/kg. At the end of the experiment, the concentration of lead in soil and earthworms body was measured. Results of this study show that the highest concentration of lead in the body of earthworms was found in all treatments at S3 and S2, which were more polluted than other sampling points to this metal. Soil earthworms have different capacities for absorbing and accumulating lead. The amount of bioaccumulation factor for lead metal at point S7 was greater than one, which was similar to previous studies. A significant increase in the amount of exchange lead (50 mg/kg) was observed in the treatment of cow manure without inoculation with earthworms. While the application of organic fertilizer with earthworm reduced the amount of Lead metal in the carbonate sector.

In terms of environmental hazard assessment, earthworms are ecologically important components of soil and considered as a biological indicator to maintain soil health and quality. The aim of this study was to assess the efficacy of Eisenia fetida earthworms in the bioremediation of cadmium in contaminated soils. For this purpose, this study was carried out on a contaminated soil sampled from the Ahangaran mine, 26 Km far from the Malayer town and surrounding lands. In this study, six soil samples were collected from 0-15 cm depth at different intervals around the mine lands and one soil sample (control sample) from the non-polluted area. This experiment was investigated as a factorial in the form of a complete randomized block design with the first factor of organic fertilizers (cow manure, carrot pulp, vermicompost, and control) and the second factor was existence or absence of earthworms. Twelve earthworms with 0.3 to 0.6 g were selected for each soil sample (300 g). The worms were exposed to cadmium-contaminated soils at concentrations of 1.159 to 6.658 mg kg-1 for 42 days. At the end of the experiment, the concentration of cadmium was measured in soil and whole body of earthworms. The results showed that earthworms have different capacities for absorbing and accumulating cadmium, which is the behavior of earthworms resulting from the diet of earthworms. The highest concentration of cadmium in the whole body of earthworms was found in all treatments at point S3 (soil sampled from the third point), which was more polluted than other sampling points. The addition of cow manure to other treatments also increased accumulation of cadmium in the soil worm tissue. The low concentration of cadmium in the soil led to the high bioaccumultion factor of this metal for earthworms. In this study, the amount of bioaccumultion factor for cadmium was more than one. Application of cow manure, vermicompost and carrot pulp treated with earthworms, significantly increased 1.54, 1.03, 1.38 mg kg-1 Cd in the organic fraction and increased 3.02, 2.79, 2.69 mg kg-1 Cd in the carbonate fraction. Extractable fraction, which contains exchangeable forms and carbonates and organic fraction, can be a good indicator of strong adsorption of cadmium in soil for earthworms. In general, the use of organic fertilizers with earthworms increased cadmium in the organic sector.

Organic carbon pools and carbon lability directly affect soil biological، physical and chemical characteristics. Besides، capacity of self-organization of soil is related to the organic carbon pools. Sand size fraction (> 50 µm) organic matter is more labile than silt+clay size fraction organic matter. Assessment of this organic carbon variation can be a suitable index to determine soil quality. The aim of present study was to evaluate the impact of land use change on particle size fractions of organic carbon and carbon pool index. In September 2010، soil samples were collected from the three major land use types including wetlands around the lake، wetlands converted to wheat، and alfalfa cultivations. Soil samples were collected from the 0-30، 30-60 and 60-90-cm depths in each of land use. According to the results of particle size fractionation of organic carbon in 0-30-cm layer، the highest and lowest amounts of sand size fraction organic carbon were obtained in wetland (67. 01 g. C. kg-1soil) and wheat land use (24. 57 g. C. kg-1soil)، respectively. Land use change from wetland to alfalfa and wheat caused a decrease of silt+clay size fraction organic carbon in 0-30-cm by 48. 39 and 45. 14 t. C. h-1، respectively. In the 30-60-cm layer of cultivated land، soil organic carbon storage in silt+clay size particle was more than sand size fraction organic carbon. Results showed that carbon pool index in alfalfa، and wheat land was decreased by 50 and 60% compared to wetland، respectively. And carbon management index in alfalfa and wheat was declined by 44. 90% and 66. 70%، respectively.