Mobility and bioavailability of lead （Pb） could be affected considerably by soil physicochemical properties; however, less is known about the effect of Pb levels and aging time. This study was conducted to evaluate ...Mobility and bioavailability of lead （Pb） could be affected considerably by soil physicochemical properties; however, less is known about the effect of Pb levels and aging time. This study was conducted to evaluate the effects of Pb levels and wetting-drying （WD） cycles on distribution and bioavailability of Pb in three semi-arid zone soils treated with different levels of Pb（NO3）2. Wetting-drying cycles simulated the actual field irrigation in the semi-arid soils. A soil with a long history of Pb contamination was also taken as a reference soil. The soils were spiked with various levels of Pb and incubated under WD cycles for 160 d. Sequential extractions and batch sorption experiments were performed to assess the fractionation of Pb in the spiked soils. Redistribution index （Uts） and reduced partitioning parameter （IR） were applied to semi-quantify the distribution of Pb in the spiked soils. A small amount of Pb sorbed was desorbed by the soils, indicating a strong and irreversible binding of Pb in the studied soils. Contribution of carbonate-bound （Car） and residual （Res） Pb fl＇actions to the total Pb of the soils was more than 97%. The Car, soluble plus exchangeable （SE）, and organic matter-bound （OMB） fractions of Pb were transferred to the Res fraction under the WD cycles. The IR and Uts values were influenced by Pb loading levels and WD; therefore, the Pb lability and/or redistribution pattern could semi-quantitatively be assessed via these parameters. At the end of the experiment, the Ia and Uts values for the Pb salt-spiked soils did not show the quasi- equilibrium state. The lability of Pb in the soils decreased with increasing incubation time and showed a strong dependence on Pb levels and soil chemical composition. WD cycles significantly affected the overall lability of Pb in soils through influencing the redistribution of Pb among solid-phase components.展开更多
Soil organic carbon(SOC) has primary importance in terms of soil physics, soil fertility and even of climate change control. One hundred soil samples were taken from an intensively cultivated Cambisol to quantify SOC ...Soil organic carbon(SOC) has primary importance in terms of soil physics, soil fertility and even of climate change control. One hundred soil samples were taken from an intensively cultivated Cambisol to quantify SOC redistribution triggered by soil erosion under a subhumid climate, by the simultaneous application of diffuse reflectance(240–1 900 nm) and traditional physico-chemical methods.The representative sample points were collected from the solum along the slopes at the depth of 20–300 cm with a mean SOC content of 12 g kg^(-1). Hierarchical cluster analyses were performed based on the determined SOC results. The spatial pattern of the groups created were similar, and even though the classifications were not the same, diffuse reflectance had proven to be a suitable method for soil/sediment classification even within a given arable field. Both organic and inorganic carbon distributions were found to be a proper tool for estimations of past soil erosion processes. The SOC enrichment was found on two sedimentary spots with different geomorphological positions. Soil organic matter composition also differed between the two spots due to selective deposition of the delivered organic matter. The components with low-molecular-weight reached the bottom of the slope where they could leach into the profile, while the more polymerised organic matter compositions were delivered and deposited even before on a higher segment of the slope in an aggregated form. This spatial difference appeared below the uppermost tilled soil layer as well, referring the lower efficiency of conventional ploughing tillage in soil spatial homogenisation.展开更多
基金Supported by the National Science Foundation of Iran and Urmia University,Iran
文摘Mobility and bioavailability of lead （Pb） could be affected considerably by soil physicochemical properties; however, less is known about the effect of Pb levels and aging time. This study was conducted to evaluate the effects of Pb levels and wetting-drying （WD） cycles on distribution and bioavailability of Pb in three semi-arid zone soils treated with different levels of Pb（NO3）2. Wetting-drying cycles simulated the actual field irrigation in the semi-arid soils. A soil with a long history of Pb contamination was also taken as a reference soil. The soils were spiked with various levels of Pb and incubated under WD cycles for 160 d. Sequential extractions and batch sorption experiments were performed to assess the fractionation of Pb in the spiked soils. Redistribution index （Uts） and reduced partitioning parameter （IR） were applied to semi-quantify the distribution of Pb in the spiked soils. A small amount of Pb sorbed was desorbed by the soils, indicating a strong and irreversible binding of Pb in the studied soils. Contribution of carbonate-bound （Car） and residual （Res） Pb fl＇actions to the total Pb of the soils was more than 97%. The Car, soluble plus exchangeable （SE）, and organic matter-bound （OMB） fractions of Pb were transferred to the Res fraction under the WD cycles. The IR and Uts values were influenced by Pb loading levels and WD; therefore, the Pb lability and/or redistribution pattern could semi-quantitatively be assessed via these parameters. At the end of the experiment, the Ia and Uts values for the Pb salt-spiked soils did not show the quasi- equilibrium state. The lability of Pb in the soils decreased with increasing incubation time and showed a strong dependence on Pb levels and soil chemical composition. WD cycles significantly affected the overall lability of Pb in soils through influencing the redistribution of Pb among solid-phase components.
基金funded by the Hungarian Foundation(OTKA)(No.PD-100929)supported by the KutatóKari Kiválósági Támogatás-Research Centre of Excellence-11476-3/2016/FEKUTsupported by the János Bolyai Research Fellowship by the Hungarian Academy of Sciences
文摘Soil organic carbon(SOC) has primary importance in terms of soil physics, soil fertility and even of climate change control. One hundred soil samples were taken from an intensively cultivated Cambisol to quantify SOC redistribution triggered by soil erosion under a subhumid climate, by the simultaneous application of diffuse reflectance(240–1 900 nm) and traditional physico-chemical methods.The representative sample points were collected from the solum along the slopes at the depth of 20–300 cm with a mean SOC content of 12 g kg^(-1). Hierarchical cluster analyses were performed based on the determined SOC results. The spatial pattern of the groups created were similar, and even though the classifications were not the same, diffuse reflectance had proven to be a suitable method for soil/sediment classification even within a given arable field. Both organic and inorganic carbon distributions were found to be a proper tool for estimations of past soil erosion processes. The SOC enrichment was found on two sedimentary spots with different geomorphological positions. Soil organic matter composition also differed between the two spots due to selective deposition of the delivered organic matter. The components with low-molecular-weight reached the bottom of the slope where they could leach into the profile, while the more polymerised organic matter compositions were delivered and deposited even before on a higher segment of the slope in an aggregated form. This spatial difference appeared below the uppermost tilled soil layer as well, referring the lower efficiency of conventional ploughing tillage in soil spatial homogenisation.
