黄棕壤不同粒级组分对镉的吸附动力学与热力学研究

采用一次平衡法研究了黄棕壤不同粒级组分(粘粒≤2 μm、粉粒2～20 μm、细砂粒20～200 μm、粗砂粒200～2000 μm)对镉的吸附动力学与热力学,并采用拉格朗日假一级动力学方程、假二级动力学方程、颗粒内扩散模型对试验数据进行拟合.结果表明,2种温度下各粒级组分对镉的吸附均可分为快反应和慢反应2个阶段,0～15 min内为快反应阶段,吸附量达到饱和吸附量的95%以上,此后为慢反应阶段;随着温度由25℃升高到45℃,各组分对镉的饱和吸附量增加了4.86%～25.3%;各组分对镉的吸附动力学符合拉格朗日假二级动力学方程,吸附过程以化学吸附为主;二级动力学吸附速率常数表明,随着各组分粒级增大,吸附速率降低;在试验温度范围内随着温度升高,吸附速率加快;吸附过程的限速步骤为颗粒间扩散;各粒级组分对镉的吸附为吸热反应,反应能自发进行.     

五里湖和贡湖不同粒径沉积物吸附磷实验研究

通过研究五里湖和贡湖不同粒径沉积物对磷的吸附动力学曲线和吸附等温曲线,分析了不同粒径沉积物氮、磷和有机质含量以及化学组成等理化特征对其吸附磷的影响,初步得出如下结论五里湖和贡湖不同粒径沉积物对磷的吸附动力学曲线和吸附等温曲线具有相似的变化趋势;贡湖沉积物每一粒级的吸附量、吸附速率和吸附效率均高于五里湖沉积物;各粒级的变化趋势均为粘粒级＞细砂粒级＞粗砂粒级＞粉砂粒级;各粒级中粉砂粒级SiO2含量最高,可能是造成其对磷的吸附量、吸附速率和吸附效率在各粒级中最低的原因.     

西辽河不同粒级沉积物对磷的吸附特征

采用平衡吸附法研究了西辽河不同粒级沉积物对磷的吸附特征.结果表明,不同粒级沉积物对磷的吸附特征圴符合Langmuir吸附等温式和Freundlich吸附等温式;黏粒级和粉粒级的磷饱和吸附量较大,分别为3791.12,2323.33mg/kg,分别相当于粗砂的6.68和4.09倍;黏粒级和粉粒级沉积物吸附的磷是磷素循环的重要组成部分,西辽河冲泻质泥沙黏粒和粉粒所携载的吸附态磷的理论入海通量分别为3791.12,2323.33mg/kg冲泻质泥沙.占沉积物磷吸附总量的28.30%.沉积物对磷的比表面积标化吸附分配系数与松结态腐殖质相关性最大,比表面积标化饱和吸附量与稳结态腐殖质相关性最大,在稳结态和紧结态腐殖质所形成的团聚体结构沉积物中存在孔隙填充方式的磷吸附.     

西辽河不同粒级沉积物的氨氮吸附-解吸特征

为估算辽河吸附态氨氮入海通量,采用平衡吸附-解吸法研究了西辽河不同粒级沉积物对氨氮的吸附-解吸特征. 结果表明:不同粒级沉积物对氨氮的吸附-解吸特征均符合Langmuir和Freundlich吸附-解吸等温式;黏粒级和粉粒级沉积物的氨氮饱和吸附量较大,分别为3 643.82和2 693.71 mg/kg,相当于粗砂的8.04和5.94倍;西辽河冲泻质泥沙黏粒和粉粒所携载的吸附态氨氮的入海通量分别为170.10和164.52 mg/kg. 占沉积物氨氮吸附总量的14.99%;黏粒级和粉粒级沉积物的氨氮解吸比例较小,分别为30.66%和42.04%,入海后可分别为上覆水提供氨氮52.15和69.16 mg/kg;黏粒级和粉粒级沉积物所吸附的氨氮是氮素循环的重要组成部分;黏粒和粉粒级沉积物的腐殖质含量远远高于粗沙,在其所形成的团聚体结构中存在的孔隙填充方式——氨氮吸附是导致黏粒和粉粒级沉积物饱和吸附量较大、解吸比例较低的根本原因.      

西辽河不同粒级沉积物对重金属铅的富集特征

重金属铅等污染物以泥沙颗粒为载体迁移转化,颗粒态铅为河流输送铅的主要形态。为估算随泥沙颗粒迁移的重金属铅的质量分数,采用平衡吸附法研究了西辽河不同粒级沉积物对重金属铅的富集特征。结果表明,不同粒级沉积物对重金属铅的富集系数为:黏粒(2.03)>粉粒(1.85)>细砂(0.83)>粗砂(0.51)。细粒级沉积物对重金属铅的富集作用比较强,黏粒和粉粒的铅富集系数分别是粗砂的3.98和3.63倍,富集水平均为低度富集。其原因有二,细粒级沉积物中腐殖质含量明显高于粗粒级;细粒级沉积物中稳结态腐殖质所占比例较高,在稳结态腐殖质胶结形成的疏松多孔团聚体结构中存在的孔隙填充方式Pb吸附,在对Pb富集中发挥重要作用。不同粒级沉积物对铅的富集系数与腐殖质总量呈显著正相关(p<0.01),相关系数(r)为0.964;西辽河沉积物在汛期黏粒级和粉粒级冲泻质泥沙所携载的吸附态铅质量分数可分别按106.02 mg/kg和98.71mg/kg估算。黏粒和粉粒级沉积物所携载的吸附态铅是铅地球化学循环的重要组成部分。     

沙土不同粒级微团聚体可解吸态磷释放通量

流失的水土是污染物的重要载体,为了估算随水土流失的沙土中可解吸态磷对上覆水体的影响,采用平衡解吸法研究了沙土不同粒级微团聚体可解吸态磷的释放通量.结果表明,不同粒级沙土微团体吸附态磷的解吸比例为黏粒(0.21)＜粉粒(0.29)＜细砂(0.60)＜粗砂(0.96).主要原因有二:细粒级中腐殖质含量显著高于粗粒级;细粒级中有机质是通过可溶有机质与黏土矿物相互结合形成复合体而富集(黏粒和粉粒级微团聚体的稳结态腐殖质所占比例显著高于其它粒级).磷在稳结态和紧结态腐殖质所形成的团聚体结构中引起的团聚体结构不可逆形变是导致黏粒级(解吸比例Dr =0.21,解吸迟滞性指数TⅡ=0.47)和粉粒级(Dr=0.29,TⅡ=0.45)微团聚体磷的解吸比例降低,解吸迟滞性指数增大的根本原因.沙土黏粒和粉粒级微团聚体携载的可解吸态磷对上覆水体的释放通量可分别按(99.52±3.54) mg·kg-和(72.48±2.62) mg·kg-1进行估算.     

西辽河沉积物中不同粒径微团聚体磷的解吸特征

采用平衡解吸法研究了西辽河沉积物不同粒径微团聚体磷的解吸特征.结果表明,不同粒径团聚体磷的解吸比例为黏粒(0.20)<粉粒(0.28)<细砂(0.45)<粗砂(0.93);其原因为:细粒级微团聚体中腐殖质含量远远高于粗粒级;细粒级微团聚体中有机质是通过可溶有机质与黏土矿物相互结合形成复合体而富集,在其所形成的复合体团聚结构中引起的团聚体结构不可逆形变是导致磷的解吸比例降低,解吸迟滞性指数增大的根本原因;西辽河冲泻质泥沙黏粒和粉粒级微团聚体所携载的可解吸态磷(NAP)入海后可分别为上覆水提供磷(212.93±38.60)mg/kg,(159.45±31.44)mg/kg.沉积物黏粒级和粉粒级微团聚体所携载的NAP是磷素循环的重要组成部分.     

菲在大庆黑钙土有机-矿质复合体上的吸附与解吸

利用超声分散法提取了黑龙江大庆黑钙土中不同粒级有机-矿质复合体,并测定了其基本理化性质.其中粘粒复合体的有机质含量最高,比表面积以及阳离子交换容量最大.研究了多环芳烃菲在不同粒级有机-矿质复合体上的吸附和解吸行为.结果表明,菲在各粒级有机-矿质复合体上的吸附和解吸等温线均符合Freundlich方程,随粒径减小,有机-矿质复合体对菲的吸附容量以及吸附的非线性程度都增加.菲在有机-矿质复合体上的解吸表现出明显的滞后现象.高有机质含量的粘粒有机-矿质复合体对菲的吸附和持留能力均较强.      

沙土不同粒径微团聚体对磷的富集特征

流失的水土是污染物的重要载体,为估算沙土吸附态磷流失量,采用平衡吸附法研究了沙土不同粒径微团聚体对磷的富集特征.结果表明,不同粒径微团聚体对磷的富集系数为:黏粒(3.79)＞粉粒(2.98),沙土中微团聚体对磷的富集作用比较强,其原因有三:细粒级微团聚体中腐殖质含量显著高于粗粒级;细粒级微团聚体中有机质是通过可溶有机质与黏土矿物相互结合形成复合体而富集,在复合体结构中存在孔隙填充方式磷吸附;粘粒和粉粒中的铁铝键有机矿质复合体所占比例显著高于其它粒级,在对磷吸附中发挥重要作用,其吸附机制除孔隙填充方式外,还存在铁铝氧化物及水化氧化物对磷的配位吸附.不同粒径团聚体对磷的吸附分配系数和富集系数均与腐殖质总量呈显著正相关(p＜ 0.01,r分别为0.854和0.954);西辽河流域沙土在暴雨径流中黏粒级和粉粒级冲泻质泥沙所携载的吸附态磷质量分数可分别按1269.15 mg·kg-1和997.53 mg·kg-1估算,黏粒和粉粒级微团聚体对磷的富集系数(Er)可分别按3.79和2.98计算.     

黄泥土不同粒径微团聚体对Cd2+的吸附与解吸研究

对采自太湖地区黄泥土进行了低能量超声波分离,采用平衡吸附法研究了不同粒径微团聚体颗粒对重金属Cd²⁺的吸附和解吸特点.结果表明,不同粒径微团聚体对Cd²⁺的吸附特性均符合Freundlich方程,模拟方程得到的K值介于152～503之间,以粘粒级和粗砂级为最大.微团聚体对Cd²⁺的吸附容量与其中游离氧化铁含量、CEC呈显著正相关.不同微团聚体Cd的解吸特点不同,粘粒级的解吸率仅为8.4%,远远低于其它粒径的微团聚体,这些结果有助于了解田间条件下土壤重金属化学行为和微观尺度的化学过程.     

Effects of free iron oxyhydrates and soil organic matter on copper sorption-desorption behavior by size fractions of aggregates from two paddy soils

Effects of free iron oxyhydrates (Fed) and soil organic matter (SOM) on copper (Cu2+) sorption-desorption behavior by size fractions of aggregates from two typical paddy soils (Ferric-Accumulic Stagnic Anthrosol (Soil H) and Gleyic Stagnic Anthrosol (Soil W)) were investigated with and without treatment of dithionite-citrate-bicarbonate and of H2O2. The size fractions of aggregates were obtained from the undisturbed bulk topsoil using a low energy ultrasonic dispersion procedure. Experiments of equilibrium sorption and subsequent desorption were conducted at soil water ratio of 1:20, 25℃. For Soil H, Cu2+ sorption capacity of the DCB-treated size fractions was decreased by 5.9% for fine sand fraction, by 40.4% for coarse sand fraction, in comparison to 2.9% for the bulk sample. However, Cu2+ sorption capacities of the H2O2-treated fractions were decreased by over 80% for the coarse sand fraction and by 15% for the clay-sized fraction in comparison to 88% for bulk soil. For Soil W, Cu2+ sorption capacity of the DCB-treated size fraction was decreased by 30% for the coarse sand fraction and by over 75% for silt sand fraction in comparison to 44.5% for the bulk sample. Cu2+ sorption capacities of the H2O2-treated fractions were decreased by only 2.0% for the coarse sand fraction and by 15% for the fine sand fraction in comparison to by 3.4% for bulk soil. However, Cu2+ desorption rates were increased much in H2O2-treated samples by over 80% except the clay-sized fraction (only 9.5%) for Soil H. While removal of SOM with H2O2 tendend to increase desorption rate, DCB- and H2O2-treatments caused decrease in Cu2+ retention capacity of size fractions. Particularly, there hardly remained Cu2+ retention capacity by size fractions from Soil H after H2O2 treatment except for clay-sized fraction. These findings supported again the dominance of the coarse sand fraction in sorption of metals and the preference of absorbed metals bound to SOM in differently stabilized status among the size fractions. Thus, enrichment and turnover of SOM in paddy soils may have great effects on metal retention and chemical mobility in paddy soils.     

Adsorption and desorption of Cu on paddy soil aggregates pretreated with different levels of phosphate

Interactions between anions and cations are important for understanding the behaviors of chemical pollutants and their potential risks in the environment. Here we prepared soil aggregates of a yellow paddy soil from the Taihu Lake region, and investigated the effects of phosphate (P) pretreatment on adsorption-desorption of Cu²⁺ of soil aggregates, free iron oxyhydrates-removed soil aggregates, goethite, and kaolinite with batch adsorption method. The results showed that Cu²⁺ adsorption was reduced on the aggregates pretreated with low concentrations of P, and promoted with high concentrations of P, showing a V-shaped change. Compared with the untreated aggregates, the adsorption capacity of Cu²⁺ was reduced when P application rates were lower than 260, 220, 130 and 110 mg/kg for coarse, clay, silt and fine sand fractions, respectively. On the contrary, the adsorption capacity of Cu²⁺ was higher on P-pretreated soil aggregates than on the control ones when P application rates were greater than those values. However, the desorption of Cu²⁺ was enhanced at low levels of P, but suppressed at high levels of P, displaying an inverted V-shaped change over P adsorption. The Cu²⁺ adsorption by the aggregate particles with and without P pretreatments was well described by the Freundlich equation. Similar results were obtained on P-pretreated goethite. However, such P effects on Cu²⁺ adsorption-desorption were not observed on kaolinite and free iron oxyhydrates-removed soil aggregates. The present results indicate that goethite is one of the main soil substances responsible for the P-induced promotion and inhibition of Cu²⁺ adsorption.     

水稻土团聚体Cu2+吸附过程中铝的溶出及土壤溶液pH变化

采用低能量超声波分散和冷冻机干燥法提取太湖地区水稻土(黄泥土)不同粒径团聚体颗粒,用平衡吸附法研究团聚体对重金属Cu2+吸附过程中铝的溶出及土壤溶液pH变化,以及不同pH的Cu2+溶液中铝的溶出量的变化.结果表明,团聚体对Cu2+的吸附过程,发生铝的溶出和土壤溶液pH下降,溶出量和pH下降幅度随Cu2+吸附量增加而增加,相同条件下铝溶出量和pH下降幅度大小顺序为:粗粉砂级>粉砂级>砂粒级>黏粒级,与氧化铁和有机质含量大小顺序相反.Cu2+溶液pH下降,铝的溶出量增加显著.氧化铁和有机质对Cu2+吸附过程铝的溶出和土壤溶液pH下降具有一定的抑制和缓冲作用.     

Adsorption and desorption of Cu~(2+) on paddy soil aggregates pretreated with different levels of phosphate

Interactions between anions and cations are important for understanding the behaviors of chemical pollutants and their potential risks in the environment.Here we prepared soil aggregates of a yellow paddy soil from the Taihu Lake region,and investigated the effects of phosphate(P) pretreatment on adsorption-desorption of Cu~(2+) of soil aggregates,free iron oxyhydrates-removed soil aggregates,goethite,and kaolinite with batch adsorption method.The results showed that Cu~(2+) adsorption was reduced on the aggregates pretreated with low concentrations of P,and promoted with high concentrations of P,showing a V-shaped change.Compared with the untreated aggregates,the adsorption capacity of Cu~(2+) was reduced when P application rates were lower than 260,220,130 and110 mg/kg for coarse,clay,silt and fine sand fractions,respectively.On the contrary,the adsorption capacity of Cu~(2+) was higher on P-pretreated soil aggregates than on the control ones when P application rates were greater than those values.However,the desorption of Cu~(2+) was enhanced at low levels of P,but suppressed at high levels of P,displaying an inverted V-shaped change over P adsorption.The Cu~(2+) adsorption by the aggregate particles with and without P pretreatments was well described by the Freundlich equation.Similar results were obtained on P-pretreated goethite.However,such P effects on Cu~(2+)adsorption-desorption were not observed on kaolinite and free iron oxyhydrates-removed soil aggregates.The present results indicate that goethite is one of the main soil substances responsible for the P-induced promotion and inhibition of Cu~(2+) adsorption.     

Sorption of pyrene on two paddy soils and their particle-size fractions

In the present study, the sorption of pyrene on two kinds of bulk paddy soils, Gleyic Stagnic Anthrosols, and Ferric accumulic Stagnic Anthrosols as well as their particle-size fractions was investigated. The sorption isotherms fitted well with Freundlich equation. For both soils, the clay fraction（ 〈 2μm） and coarse sand fraction（2000-250μm） had higher sorption capacity than fine sand fraction（250-20 μm） and silt fraction（20-2 μm）. The IogKoc values obtained of each soil and its particle-size fractions were similar, proving that SOM content was a key factor affecting pyrene sorption. The Kd values showed a significant correlation with contents of dithionite-extractable Fe in both paddy soils and a good relationship with CEC in Gleyic Stagnic Anthrosols, indicating possible effects of surface properties of particle-size fractions on the sorption of pyrene.     

芘在土壤不同粒径组分中的形态分布

以芘为PAHs代表物,采用土壤粒径分级和PAHs连续提取方法,研究了老化4周污染黄棕壤中芘在不同粒径组分中的形态分布.结果表明,供试土壤中芘主要以有机溶剂提取态和可脱附态存在,结合态残留量所占比例甚小;细砂粒、粉粒、粗黏粒和细黏粒中芘残留占原土总残留的比例分别为6.00%、4.66%、34.68%和40.88%.各粒径组分中各形态芘含量大小顺序为有机溶剂提取态>可脱附态>结合态,有机溶剂提取态和可脱附态是各粒径组分中芘残留的主要存在形态(占比98.82%以上),芘结合态残留量占比<1.18%.土壤中黏粒(包括细黏粒和粗黏粒)是芘可脱附态、有机溶剂提取态、结合态和可提取态残留储存的主要粒径组分.