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生源要素磷(P)在天然沉积物-水界面上的吸附与分配
Alternative TitlePhosphorus (P) Adsorption and Partitioning on Natural Sediment-Water Interface
周爱民
Subtype博士
Thesis Advisor汤鸿霄
2005-06-01
Degree Grantor中国科学院研究生院
Place of Conferral北京
Degree Discipline环境工程
Keyword富营养化 沉积物 吸附 吸附模型 太湖 影响因素
Abstract本文以采自太湖的6 个沉积物样品为主要研究对象,对沉积物组成以及各种形态P 的含量分别做了定量分析,在鉴定典型沉积物的表面结合位特性的基础上,进一步研究了P 在沉积物上的吸附性质及其影响因素。
6 个采样点基本上覆盖了太湖主要水体区域,尤其是T1、T2 和T4 采样点分别代表着重富营养化、富营养化和中富营养化的太湖典型营养状态。分别用AAS和ICP-AES 法对沉积物中金属含量,特别是活性态金属含量进行了定量分析,发现活性态Fe 和Al 具有较高的含量。为了了解沉积物的吸附特性,本文以T1、T2 和T4 三个沉积物为例,用碱饱和酸量反滴定法对其表面结合位进行了滴定分
析和定量计算,发现表面结合位总量具有明显的大小顺序:T1>T2>>T4。这表明虽然沉积物样品采自同一湖泊,但其表面性质有着显著的差异,采自北太湖区域的T1、T2 沉积物对P 等阴离子污染物的吸附能力就应远比湖心区域沉积物T4强。利用表面络合模式的基本思想,用FITEQL 程序拟合计算得到T1 和T2 沉积物分别在0.1mol/L、0.01mol/L、0.001mol/L 的NaCl 溶液背景下的表面酸碱反应常数。
采用逐级提取法对6 个沉积物样品中的P 形态进行了分析。将无机态P 分为NaOH-P 、BD-P 、HCl-P 和 NH4Cl-P 四个部分,以6 个样品的平均值计算,这4 种形态P 含量的大小顺序为:NaOH-P > BD-P > HCl-P > NH4Cl-P。线性回归分析结果表明,在所考察的6 个太湖沉积物样品中活性态Fe 与BD-P 的含量有着明显的线性关系,这表明,由草酸盐溶液提取得到的活性态Fe 对P 在沉积物上的吸附以及沉积物对P 的持留作用上扮演着重要的角色,因此可以说Fe 是湖
泊水体富营化发生过程的重要控制因素。类似地,BD-P 和NaOH-P 含量的总和与活性态Fe 和Al 的(水合)氧化物的含量总和之间具有明显的线性关系,这表明活性态Fe 和Al 的(水合)氧化物是天然沉积物中吸附P 的主要物质承担者。将生物可用态P 定义为NH4Cl-P 、NaOH-P 和BD-P 含量的总和, 即:BAP=NH4Cl-P+NaOH-P+BD-P;研究发现,在所研究的太湖沉积物中50%以上
的无机态P 具有生物可用性,即这部分P 在环境条件允许的情况下易释放出来而被生物再次利用。
考虑到已吸附在沉积物上的那部分可交换态P(即NAP),从经典的Langmuir吸附等温线模型出发,推导出适合描述P 在已有P 污染的沉积物上吸附定量数学模型,并用此模型对P 在6 个太湖沉积物样品上吸附实验数据进行了拟合。拟合结果得到最大吸附容量(PAC),Langmuir 吸附平衡常数(k)。利用所得的拟合参数通过公式计算方法得到原有易交换态P(NAP),临界磷平衡浓度(EPC0),以及固-液分配系数Kp 值。最后通过线性回归数据分析方法发现分配系数Kp,附容量PAC 都与沉积物中活性态Fe 和Al 含量呈良好的线性关系,这也再次表明太湖沉积物中活性Fe 和Al 是对P 持留的主要物质作用者。
pH 值对P 吸附的影响实验表明:当pHpHb 时,溶液中的OH-会大幅度增加,它会与溶液中的SRP 竞争沉积物表面的吸附位,所以在这一pH 值范围内,P 的吸附量也会减少;那么,在pHaP 的吸附可逆性实验结果表明,P 在太湖沉积物上的吸附具有较好的可逆性。这种可逆性在很大程度上会加速了P 在湖泊水体的循环,也使沉积物对上覆水体中P 浓度的变化具有较快的响应,使之及时得到调节,最终使湖泊水体的富营化易于发生和发展,从而也增加了湖泊水体富营养化自我恢复的难度。
Other AbstractThere is substantial evidence that sediments can act as a phosphorus “buffer‘
controlling the concentrations in the overlying water through interactions with
suspended particles. It is essential to study the forms of P in sediment and the
adsorption-desorption behaviors of phosphorus between sediment-water interface for further understanding the mechanism of eutrophication and evaluating the restoration probability of eutrophication.
Six typical sediments from Taihu Lake, a meso-to-hypereutrophic lake, were
collected and examined on the basis of P-fractionation by sequential extraction
scheme. Sedimentary inorganic phosphorus were fractioned into four forms and the rank order according to the mean concentration of P-fractions in Taihu Lake was NaOH-P > BD-P > HCl-P > NH4Cl-P. The concentrations of BD-P were linearly
correlated with the content of active Fe (R2=0.95). Also, the linear relationship
between the sum of BD-P and NaOH-P and the sum of active Fe and active Al content was observed within the six sediments investigated (R2=0.96). Moreover, the bio-available phosphorus (BAP) content was estimated by the sum of NH4Cl-P, BD-P, and NaOH-P, viz. BAP=NH4Cl-P+NaOH-P+BD-P. In the Taihu Lake, the BAP
contents are ranging from 0.10mg/g dw to 1.25mg/g dw, and average 0.40mg/g dw for all sediment samples. The relative contributions of BAP to total sedimentary
phosphorus (TP) and inorganic sedimentary phosphorus (IP) range from 18.67% to
50.79% (33.61% on average) and from 52.82% to 82.09% (67.81% on average),
respectively.
The classic Langmuir isotherm equation was modified to describe phosphorus adsorption on P-polluted sediments. The P adsorption characteristics of six sediment samples from Chinese Taihu Lake were studied by short-term isotherm batch experiments and related to sediment compositions. The maximum P adsorption capacities (PAC) and P-binding energy constant (k) were obtained by nonlinearly fitting sorption data using the modified Langmuir isotherm model. Native adsorbed exchangeable phosphorus (NAP), the zero equilibrium P concentration value (EPC0), and partitioning coefficients (Kp) were subsequently calculated by corresponding formulae. Kp and PAC were linearly related to the contents of active Fe and Al in sediments by least squares regression analyses (R20.9 for both). The effect of pH in a wide range on adsorption process was investigated and H2PO4- was presumed to be the preferential sorption species in overall sorption process. The fact that the amount of P sorbed and zeta potential of sediment particles have no necessary relationship reveals that a strong contribution to the P binding still comes from a ligand-exchange process on the Me-OH2+ and Me-OH sites rather than electrostatic attraction. In addition, the influence of oxidation-reduction potential (ORP) was investigated and discussed and the dual nature of sediments as a pool or source of P in natural waters was evaluated in site T1~T4. In addition, the effects of salinity, particle size and solid concentration on P adsorption were also investigated.
The experiments designed for reversibility of P adsorption indicate that adsorbed P
will very likely be released by sediment if conditions permit. This property will accelerate significantly the cycling of P in water system and thus go against the restoration of eutrophic lake.
Subject Area水处理工程
Language中文
Document Type学位论文
Identifierhttp://ir.rcees.ac.cn/handle/311016/2214
Collection环境水质学国家重点实验室
Recommended Citation
GB/T 7714
周爱民. 生源要素磷(P)在天然沉积物-水界面上的吸附与分配[D]. 北京. 中国科学院研究生院,2005.
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