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| Phosphorus(P)is the limiting factor for biomass growth in surface waters. In sandy soils, due to their low sorp- tion capacity and high permeability, leaching processes are special interest (Sawhney 1977). Discharge of wastewater from agricultural and industrial activities contributes to P enrichment in aquatic ecosystems (Camargo et al. 2005). P in the soil solution exists as negatively charged P ion, but it is well known that P is relatively immobile in the soil system (Johnson et al. 1997). However, several recent studies provide clear evidence that P can be leached from soil under suitable conditions (Jalali and Kolahchi 2009; Jalali 2009; Maguire and Sims 2002; Heckrath et al. 1995). Leaching of nutrients including P from sandy soils has been identified as one of the main factors for degrading water quality (Chen et al. 2006). The amount and distri- bution of rainfall and the type and rate of used fertilizer are known as the factors that affect losses of P from sandy soils. P in soil is considered to be distributed among several geochemical forms including soil solution and exchangeable, organic matter phase, Ca-bound phase, Fe–Al-bound phase, and residual phases(Hedley et al. 1982a, b). A sequential chemical extraction of P from soils could provide a method- ology for examining soil P that allows for a better understanding of status of P (Linquist et al. 2011). Also, knowledge about P fractionation in soils is important for predicting bioavailability, leachability, and transformations of P between chemical forms in surface water and soils (Sui et al. 1999). The Ca- bound, Fe–Al oxide-bound, and organic matter- bound fractions could be considered relatively active depending on the actual physical and chemical prop- erties of soil. Soil amendment is considered as one of the best ways to reduce P leaching from sandy soils. Important factors for P retention are the pres- ence of amorphous aluminum (Al) oxides and iron (Fe) compounds in the soil (Börling et al. 2001; Borggaard et al. 1990). Also, presence of calcium (Ca) in soils decreases the release of P (Hughes and Gilkes 1984). Previous studies have shown that ad- dition of materials containing these elements can reduce P solubility (Kalbasi and Karthikeyan 2004; Dou et al. 2003). There are many methods to control P loss. One of these methods is the addition of nanoparticles (NPs) and natural clay minerals. To assess the risk of eutrophication problems, it is nec- essary to know the leaching behavior of P in the presence of modified and unmodified adsorbents when mixed with soil. Although, several investiga- tions of P leaching from amended soil with compost and inorganic fertilizer (Esteller et al. 2009; Elliot et al. 2002a); piggery waste ash (Kuligowski and Poulsen 2009); CaCl2, CaCO 3, Al(OH) 3, cellulose, and mill mud (Yang et al. 2007); and biosolids (Lu and O’Connor 2001) have been carried out, relative- ly few studies on the P leaching from amended soil with clay minerals and NPs are available. On the other hand, several researchers are concerned that NPs transported in the environment may contami- nate surface and groundwater and pose potential risks to microorganisms, animals, and humans when applied in commercial quantities (Wiesner et al. 2006; Colvin 2003). Therefore, it is essential to understand the release of the NPs from soil column. The objectives of this paper are (1) to assess P leaching fromanamended sandy soil with clay minerals and NPs,(2)to investigate the different P form spresents in soil after P leaching,(3)to evaluate movement of Pin a column experiment using transport model, and (4) to evaluate movement of the NPs from soil column. |
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| 磷（P）是生物质在地表水中生长的限制性因素。在沙质土壤中，由于它们吸附容量低而渗透性高，因此其浸出过程特别受到关注（桑尼1977）。农业和工业活动的废水排放有利于水生生态系统富集P（卡马乔等人，2005）。在土壤溶液中P以带负电荷的P离子形式存在，但众所周知，P在土壤系统中是相对稳定的（Johnson等，1997）。但是，最近的一些研究提供了明确的证据，证明磷可以在适当的条件下从土壤中浸出淋溶（Jalali and Kolahchi 2009; Jalali 2009; Maguire and Sims 2002; Heckrath et al. 1995）。从沙土中包括P在内的营养物质的浸出已被确定为是水质退化的主要因素之一（陈等，2006）。降雨量及其分布、以及所使用肥料的类型和速率都是已知影响磷从沙土中损失的因素。 p在土壤被以几种地球化学形式分布，包括土壤溶液、可交换、有机物相、钙结合相、Fe-Al结合相，以及残余相位分布（Hedley et al. 1982a， b）。从土体中进行序贯化学提取所得到的P为检测土壤中磷提供了一种方法，能够更好地了解的P的状态（Linquist等，2011）。此外，对土壤分馏所得到的P的了解是重要的，可以帮助预测磷的生物利用度、浸出力，以及P在地表水和土壤之间不同化学形式之间的转换等（Sui et al.，1999）。根据土壤的实际物理和化学特性，Ca结合磷、铁 - 铝氧化物结合磷、以及有机物结合磷可以用于参考各不同组分磷的相对活性。土壤改良剂被认为是减少磷从沙质土壤中浸出的最佳方法之一。保留P的重要因素是土壤中有非晶态铝（Al）氧化物和铁（Fe）化合物的存在（Börling et al. 2001; Borggaard et al. 1990）。另外，土壤中钙离子（Ca）的存在也可减小P的释放（Hughes and Gilkes 1984）。以前的研究已经表明，添加含有这些元素的材料可以降低P的溶解度（Kalbasi and Karthikeyan 2004; Dou et al. 2003）。有许多方法可以控制磷的流失。这些方法之一是添加纳米颗粒（NPs）和天然粘土矿物质。为评估富营养化问题的风险，有必要知道改性和未改性吸附剂与土壤混合存在条件下P的浸出行为。虽然在使用堆肥和无机肥的土壤（Esteller et al. 2009; Elliot et al. 2002a），猪场废弃物粉煤灰（Kuligowski and Poulsen 2009）、氯化钙、碳酸钙、AL(OH)3、纤维素和磨泥（Yang et al. 2007），以及生物固体（Lu and O’Connor 2001）中有关P浸出的研究已经开展，但对用粘土矿物和纳米粒子修正土壤条件下P浸出的研究相对很少。而另一方面，一些研究人员担心，纳米颗粒在环境中的运输可能会污染地表水和地下水，使用商业应用的量会对微生物、动物和人类具有潜在风险（Wiesner et al. 2006; Colvin 2003）。因此，了解纳米颗粒从土壤柱中的释放是至关重要的。本文的目的是：（1）评估用粘土矿物和纳米颗粒修正沙土中P的浸出，（2）研究P浸出后，土壤中的磷的不同型式，（3）用运输模型实验评估P在柱中的运动，（4）评估纳米颗粒在土壤柱中的运动。 |
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