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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）是生物質(zhì)在地表水中生長的限制性因素。在沙質(zhì)土壤中，由于它們吸附容量低而滲透性高，因此其浸出過程特別受到關(guān)注（桑尼1977）。農(nóng)業(yè)和工業(yè)活動的廢水排放有利于水生生態(tài)系統(tǒng)富集P（卡馬喬等人，2005）。在土壤溶液中P以帶負(fù)電荷的P離子形式存在，但眾所周知，P在土壤系統(tǒng)中是相對穩(wěn)定的（Johnson等，1997）。但是，最近的一些研究提供了明確的證據(jù)，證明磷可以在適當(dāng)?shù)臈l件下從土壤中浸出淋溶（Jalali and Kolahchi 2009; Jalali 2009; Maguire and Sims 2002; Heckrath et al. 1995）。從沙土中包括P在內(nèi)的營養(yǎng)物質(zhì)的浸出已被確定為是水質(zhì)退化的主要因素之一（陳等，2006）。降雨量及其分布、以及所使用肥料的類型和速率都是已知影響磷從沙土中損失的因素。 p在土壤被以幾種地球化學(xué)形式分布，包括土壤溶液、可交換、有機物相、鈣結(jié)合相、Fe-Al結(jié)合相，以及殘余相位分布（Hedley et al. 1982a， b）。從土體中進(jìn)行序貫化學(xué)提取所得到的P為檢測土壤中磷提供了一種方法，能夠更好地了解的P的狀態(tài)（Linquist等，2011）。此外，對土壤分餾所得到的P的了解是重要的，可以幫助預(yù)測磷的生物利用度、浸出力，以及P在地表水和土壤之間不同化學(xué)形式之間的轉(zhuǎn)換等（Sui et al.，1999）。根據(jù)土壤的實際物理和化學(xué)特性，Ca結(jié)合磷、鐵 - 鋁氧化物結(jié)合磷、以及有機物結(jié)合磷可以用于參考各不同組分磷的相對活性。土壤改良劑被認(rèn)為是減少磷從沙質(zhì)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態(tài)鋁（Al）氧化物和鐵（Fe）化合物的存在（Börling et al. 2001; Borggaard et al. 1990）。另外，土壤中鈣離子（Ca）的存在也可減小P的釋放（Hughes and Gilkes 1984）。以前的研究已經(jīng)表明，添加含有這些元素的材料可以降低P的溶解度（Kalbasi and Karthikeyan 2004; Dou et al. 2003）。有許多方法可以控制磷的流失。這些方法之一是添加納米顆粒（NPs）和天然粘土礦物質(zhì)。為評估富營養(yǎng)化問題的風(fēng)險，有必要知道改性和未改性吸附劑與土壤混合存在條件下P的浸出行為。雖然在使用堆肥和無機肥的土壤（Esteller et al. 2009; Elliot et al. 2002a），豬場廢棄物粉煤灰（Kuligowski and Poulsen 2009）、氯化鈣、碳酸鈣、AL(OH)3、纖維素和磨泥（Yang et al. 2007），以及生物固體（Lu and O’Connor 2001）中有關(guān)P浸出的研究已經(jīng)開展，但對用粘土礦物和納米粒子修正土壤條件下P浸出的研究相對很少。而另一方面，一些研究人員擔(dān)心，納米顆粒在環(huán)境中的運輸可能會污染地表水和地下水，使用商業(yè)應(yīng)用的量會對微生物、動物和人類具有潛在風(fēng)險（Wiesner et al. 2006; Colvin 2003）。因此，了解納米顆粒從土壤柱中的釋放是至關(guān)重要的。本文的目的是：（1）評估用粘土礦物和納米顆粒修正沙土中P的浸出，（2）研究P浸出后，土壤中的磷的不同型式，（3）用運輸模型實驗評估P在柱中的運動，（4）評估納米顆粒在土壤柱中的運動。 |
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