There are a number of factors that contribute to heavy metal contamination in agricultural soils including deficient management of solid waste, waste water discharge, irrigation with contaminated water, and use of fer...There are a number of factors that contribute to heavy metal contamination in agricultural soils including deficient management of solid waste, waste water discharge, irrigation with contaminated water, and use of fertilizers and pesticides. The aim of this study is to estimate the sources and the levels of metals in soils of the ULB （Upper Litani Basin） that receive all mentioned factors. Soil samples were collected during the dry season from 24 sites along the Litani River flow, and 12 sites irrigated by Canal 900 withdrawn from the Qaraoun Dam along river. Metals in soils were analyzed using EDXRF （energy dispersive X-ray fluorescence） technique. Data revealed the following average levels of some heavy metals in soils with high percentage of samples exceeding the international guidelines： Mn （593 mg/kg）--67%, Ni （98 mg/kg）--96%, Cr （143 mg/kg）--92%, Hg （3.6 mg/kg）--38%, Cd （2.8 mg/kg）---25% and As （17.6 mg/kg）-84%. In canal soils： Mn （683 mg/kg）-86%, Ni （156 mg/kg）-100%, Cr （203 mg/kg） -100%, Hg （2.3 mg/kg）-25%, Cd （3.3 mg/kg）-25% and As （19.5 mg/kg）-92%. The prime source of toxic metals was due to the agricultural runoffs, beside sewage and domestic waste water discharge. Thus, the prominent findings of high levels of toxic metals （Cr, Cd, Hg and As） in soils and consequent probability in plants might induce a major health threat to consumers,展开更多
Heavy metal contamination of agricultural soils poses risks and hazards to humans. The remediation of heavy metal-polluted soils has become a hot topic in environmental science and engineering. In this review, the app...Heavy metal contamination of agricultural soils poses risks and hazards to humans. The remediation of heavy metal-polluted soils has become a hot topic in environmental science and engineering. In this review, the application of clay minerals for the remediation of heavy metal-polluted agricultural soils is summarized, in terms of their remediation effects and mechanisms, influencing factors, and future focus. Typical clay minerals, natural sepiolite, palygorskite, and bentonite, have been widely utilized for the in-situ immobilization of heavy metals in soils, especially Cd-polluted paddy soils and wastewater-irrigated farmland soils. Clay minerals are able to increase soil pH, decrease the chemical-extractable fractions and bioavailability of heavy metals in soils, and reduce the heavy metal contents in edible parts of plants. The immobilization effects have been confirmed in field-scale demonstrations and pot trials. Clay minerals can improve the environmental quality of soils and alleviate the hazards of heavy metals to plants. As main factors affecting the immobilization effects, the pH and water condition of soils have drawn academic attention. The remediation mechanisms mainly include liming, precipitation, and sorption effects. However, the molecular mechanisms of microscopic immobilization are unclear. F^ture studies should focus on the long-term stability and improvement of clay minerals in order to obtain a better remediation effect.展开更多
To evaluate the current state of the environmental quality of agricultural soils in Taiyuan City, a hotspot for China's industrial development, the concentrations of 8 heavy metals in soils were investigated by me...To evaluate the current state of the environmental quality of agricultural soils in Taiyuan City, a hotspot for China's industrial development, the concentrations of 8 heavy metals in soils were investigated by means of extensive sampling in farmlands, forestlands,and grasslands in the city. Statistical analyses and spatial distribution maps were used to identify the most significant heavy metal pollutants. The mean concentrations of As, Cd, Cu, Hg, Pb, Zn, Ni, and Cr were slightly higher than their background values in Taiyuan's topsoil, but were lower than the maximum permissible concentrations in the Chinese Environmental Quality Standard for agricultural soils. Farmland soils in Taiyuan had the highest average Cd, Cu, Hg, Pb, Zn, and Cr concentrations, but the As and Ni concentrations did not differ significantly among the farmland, forestland, and grasslands. Soil contamination by Cd, Cu, Hg, Pb,Zn, and Cr was mainly derived from farming practices, especially the use of sewage water for irrigation. In contrast, As and Ni might derive mainly from the soil parent material. The identification of heavy metal sources in agricultural soils may provide a basis for taking appropriate action to protect soil quality.展开更多
文摘There are a number of factors that contribute to heavy metal contamination in agricultural soils including deficient management of solid waste, waste water discharge, irrigation with contaminated water, and use of fertilizers and pesticides. The aim of this study is to estimate the sources and the levels of metals in soils of the ULB （Upper Litani Basin） that receive all mentioned factors. Soil samples were collected during the dry season from 24 sites along the Litani River flow, and 12 sites irrigated by Canal 900 withdrawn from the Qaraoun Dam along river. Metals in soils were analyzed using EDXRF （energy dispersive X-ray fluorescence） technique. Data revealed the following average levels of some heavy metals in soils with high percentage of samples exceeding the international guidelines： Mn （593 mg/kg）--67%, Ni （98 mg/kg）--96%, Cr （143 mg/kg）--92%, Hg （3.6 mg/kg）--38%, Cd （2.8 mg/kg）---25% and As （17.6 mg/kg）-84%. In canal soils： Mn （683 mg/kg）-86%, Ni （156 mg/kg）-100%, Cr （203 mg/kg） -100%, Hg （2.3 mg/kg）-25%, Cd （3.3 mg/kg）-25% and As （19.5 mg/kg）-92%. The prime source of toxic metals was due to the agricultural runoffs, beside sewage and domestic waste water discharge. Thus, the prominent findings of high levels of toxic metals （Cr, Cd, Hg and As） in soils and consequent probability in plants might induce a major health threat to consumers,
基金supported by the Central Public Research Institutes Basic Funds for Research and Development, China (No. 2016-szjj-wrxf-lxf)the National Natural Science Foundation of China (No. 41401362)the Funds for Science and Technology Innovation Project from the Chinese Academy of Agricultural Sciences (No. CAAS-XTCX-2016018)
文摘Heavy metal contamination of agricultural soils poses risks and hazards to humans. The remediation of heavy metal-polluted soils has become a hot topic in environmental science and engineering. In this review, the application of clay minerals for the remediation of heavy metal-polluted agricultural soils is summarized, in terms of their remediation effects and mechanisms, influencing factors, and future focus. Typical clay minerals, natural sepiolite, palygorskite, and bentonite, have been widely utilized for the in-situ immobilization of heavy metals in soils, especially Cd-polluted paddy soils and wastewater-irrigated farmland soils. Clay minerals are able to increase soil pH, decrease the chemical-extractable fractions and bioavailability of heavy metals in soils, and reduce the heavy metal contents in edible parts of plants. The immobilization effects have been confirmed in field-scale demonstrations and pot trials. Clay minerals can improve the environmental quality of soils and alleviate the hazards of heavy metals to plants. As main factors affecting the immobilization effects, the pH and water condition of soils have drawn academic attention. The remediation mechanisms mainly include liming, precipitation, and sorption effects. However, the molecular mechanisms of microscopic immobilization are unclear. F^ture studies should focus on the long-term stability and improvement of clay minerals in order to obtain a better remediation effect.
基金supported by the Science & Technology Pillar Program of Shanxi Province, China (No. 20121101011)the National Natural Science Foundation of China (Nos. 41271513 and 41101013)
文摘To evaluate the current state of the environmental quality of agricultural soils in Taiyuan City, a hotspot for China's industrial development, the concentrations of 8 heavy metals in soils were investigated by means of extensive sampling in farmlands, forestlands,and grasslands in the city. Statistical analyses and spatial distribution maps were used to identify the most significant heavy metal pollutants. The mean concentrations of As, Cd, Cu, Hg, Pb, Zn, Ni, and Cr were slightly higher than their background values in Taiyuan's topsoil, but were lower than the maximum permissible concentrations in the Chinese Environmental Quality Standard for agricultural soils. Farmland soils in Taiyuan had the highest average Cd, Cu, Hg, Pb, Zn, and Cr concentrations, but the As and Ni concentrations did not differ significantly among the farmland, forestland, and grasslands. Soil contamination by Cd, Cu, Hg, Pb,Zn, and Cr was mainly derived from farming practices, especially the use of sewage water for irrigation. In contrast, As and Ni might derive mainly from the soil parent material. The identification of heavy metal sources in agricultural soils may provide a basis for taking appropriate action to protect soil quality.
