Varying effect of biochar on Cd, Pb and As mobility in a multi-metal contaminated paddy soil.
Varying effect of biochar on Cd, Pb and As mobility in a multi-metal contaminated paddy soil.
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DOI：
10.1016/j.chemosphere.2016.01.044
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发表时间：
2016-06
期刊：
影响因子：
8.8
通讯作者：
D. Yin;Xin Wang;Can Chen;Bo Peng;Changyin Tan;Hai-long Li
中科院分区：
文献类型：
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作者：
D. Yin;Xin Wang;Can Chen;Bo Peng;Changyin Tan;Hai-long Li
镉、铅和砷是中国土壤中最突出的污染物。本文研究了水葫芦(BCW)和稻草(BCR)生物炭在酸性降水条件下对土壤Cd、Pb和As的固持能力和耐久性。两个生物炭中的Cd、Pb和As总量均低于国际生物炭倡议推荐的生物炭毒性标准所允许的最大限值。为了评价BCS对Cd、Pb、As的生物有效性和迁移性的影响，首先进行了CaCl2、KH2PO4和SPLP的提取。在用CaCl2和KH_2PO_4中性提取时，在BC为2%或5%的情况下，随着KH_2PO_4萃取物As的增加，CaCl2萃取物中的Cd/Pb浓度显著降低。在以模拟酸性雨水为萃取剂的SPLP中，用2%的BCW提取的SPLP提取物中Cd、Pb和As的含量与之相当，而其他处理的SPLP-Cd、Pb或As的含量略有或显著增加。较长时间的浸出柱试验进一步证实了2%BCW在连续酸暴露下对Cd的固定化具有较高的耐久性。同时，与无生物炭对照相比，使用2%BCW的洗脱液中As浓度几乎没有增加，这表明酸输入时As动员的风险较低。然而，在酸洗初期，无论是BCW对照土壤还是2%BCW改良剂土壤，渗滤液中的铅含量都显著高于对照土壤，这表明铅矿物在BCW(很可能是PbO)中的酸溶度高于供试土壤(PbO2，PbAs2O6)。综上所述，BCW在酸雨条件下对土壤Cd的固定具有重要的潜力，而对As的活化作用不大。但它可能会同时将高度酸溶的铅矿物加载到土壤中，导致酸暴露时铅的移动性增加。因此，需要对生物炭中的铅含量提出更严格的门槛，以确保生物炭在人为酸化土壤中的应用。
Cd, Pb and As stand as the most prominent contaminants prevailing in Chinese soils. In the present study, biochars derived from water hyacinth (BCW) and rice straw (BCR) were investigated regarding their applicability and durability in soil Cd, Pb, and As immobilization under acid precipitation. Total Cd, Pb, and As in both BCs were below the maximum allowed threshold according to biochar toxicity standard recommended by International Biochar Initiative. To evaluate BCs effect on Cd, Pb, As bioavailability and mobility, CaCl2, KH2PO4and SPLP extractions were firstly carried out. In neutral extraction with CaCl2and KH2PO4, significantly reduced Cd/Pb concentrations in CaCl2extract along with elevated KH2PO4-extractable As were recorded with either BC at 2% or 5%. In SPLP with simulated acid rainwater as extractant, comparable Cd, Pb and As levels were determined in SPLP extract with 2% BCW, while slight to significant increase in SPLP-Cd, Pb or As was recorded with other treatments. Longer-term leaching column test further confirmed the high durability of 2% BCW in Cd immobilization under continuous acid exposure. In parallel, little increase in As concentrations in eluate was determined with 2% BCW compared to no-biochar control, indicating a lowered risk of As mobilization with acid input. However, remarkably higher Pb in leachate from both BCW-only control and 2% BCW-amended soils were noticed at the initial stage of acid leaching, indicating a higher acid-solubility of Pb minerals in BCW (most probably PbO) than in tested soil (PbO2, PbAs2O6). Taken together, BCW exhibited important potential for soil Cd sequestration with little effect on As mobilization under acid precipitation. But it may simultaneously load highly acid-soluble Pb minerals into soils, resulting in elevated Pb mobility upon acid exposure. Therefore, more stringent threshold for Pb content in biochar need to be put forward to secure biochar application in soils subject to anthropogenic acidification.