【作者】 石孝洪；

【导师】 魏世强；

【作者基本信息】 西南农业大学 ， 环境工程， 2004， 硕士

【摘要】 针对国内外对淹水土壤在于湿交替下磷释放机制及环境效应的研究不足，选取三峡水库消落区主要类型土壤代表性样品30个，进行了模拟淹水磷释放与吸附试验，确定了土壤磷释放速率和释放负荷。通过系统测定土壤在周期性淹水条件下的性质变化，结合磷吸附解吸试验，研究了不同类型和不同利用的土壤在干湿交替条件下的磷释放机制，提出了表征水土界面磷迁移的量化指标。研究结果显示： 土壤在模拟淹水期间，上覆水pH与土壤pH呈正相关，电导率随淹水时间延长逐渐升高。土壤释放的金属离子主要为Ca²⁺、Mg²⁺，释放到水中的Feⁿ⁺、Mn²⁺浓度较低，而K⁺表现为负释放。 干湿交替对土壤氧化还原电位（Eh）、pH及其无定形氧化物有显著影响，不同类型和不同利用的土壤在干湿交替条件下的性质变化存在差异。在淹水期间，土壤pH逐渐向中性接近，土壤Eh显著降低，有机质（OM）含量高的土壤，Eh下降的速率和幅度都较大，最低可降到-250～-300mV。淹水土壤干燥后，pH和Eh可恢复到淹水前水平。淹水能使土壤活性铁(Fe_OX)含量显著提高，30个土壤淹水后，Fe_OX均值比淹水前升高了121％，旱地土壤淹水后Fe_OX增幅高于水田，15个旱地土壤淹水后，Fe_OX均值从1070mg／kg升高到4030mg／kg，比淹水前升高了277％，土壤淹水干燥后Fe_OX含量与淹水前无显著差异。土壤活性铝(Al_OX)的淹水效应不如Fe_OX明显，土壤淹水能提高Al_OX含量，但与淹水前相比差异并不显著，淹水干燥后Al_OX含量降低，与淹水前和淹水时存在显著差异。土壤的磷吸持饱和度（DPS）在干湿交替条件下表现出显著性差异，淹水期间土壤DPS显著降低，淹水干燥后升高。 干湿交替对土壤有效磷（Olsen P）及磷形态转化有显著影响。不同类型和不同利用的土壤在淹水期间Olsen P均有不同程度升高，淹水干燥后又恢复到淹水前水平，但旱地土壤经过淹水干燥后Olsen P比未淹水时有所降低，干湿交替对石灰性黄壤的Olsen P无显著影响。在试验期间（135天），添加到土壤中的外源磷主要转化成为Ca₂-P、Ca₈-P、Al-P和Fe-P，转化为O-P和Ca₁₀-P的比例极少，土壤淹水能增加Ca₂-P、Ca₈-P和Al-P含量，干燥能增加Fe-P含量。 干湿交替对土壤磷的等温吸附解吸性能有显著影响。土壤磷最大吸附量（q_m）和最大缓冲能力（MBC）为淹水＞淹水后干燥＞未淹水，旱地紫色土淹水后q_m升高了413％，水田黄壤淹水后MBC升高了10倍。土壤磷的解吸能力为未淹水＞淹水后干燥＞淹水。 在模拟淹水条件下，黄壤的释磷能力明显低于冲积土和紫色土，冲积土的磷释放能力强。磷释放一般在淹水28天后达到平衡。土壤添加外源磷后，上覆水磷浓呈指数增加，可用模型C_RP＜0.45=A·e^BPi来描述，该模型表明，出露期在消落区土壤上进行施磷肥耕作，在淹没期将带来高的磷释放风险。磷释放量与添加外源磷和淹水时间的关系可用模型Q_RP＜0.45=A·P_i^α·t^β，t≤西南农业大学硕士学位论文30来表征，模型参数a、刀与土壤吸磷能力有关。 在模拟淹水条件下，土壤吸磷能力表现为黄壤>紫色土>冲积土。当水中磷浓度较低时，吸附达到平衡的时间较短，当水中磷浓度较高时，吸附达到平衡的时间相对较长，可用广义Langmuir模型描述为:伽=l/扭+B.t“)，A=于只”，B=P’名“，，占一1 .015，。一0.0125，。与淹水土壤的活性铁、活性铝含量呈显著正相关，:与淹水土壤的活性铁、活性铝含量呈显著负相关。 淹水土壤磷释放能力可由两个方面来表征，一是土壤磷的形态及水平，二是土壤的吸磷能力.土壤磷活性及水平越高，且土壤吸磷能力越弱，磷释放风险就越高。表征土壤磷活性的指标可选用Cacl:P、olsenP、caZ一P、Cas一P等，这些指标与磷释放量呈显著正相关。等温吸附解吸参数（如知、为田c、f等）虽然可以表征土壤吸磷能力，但模拟淹水时土壤的吸磷能力受多种因子控制。本研究表明淹水土壤的吸磷能力与土壤Feox、A咏、OM、C副CO3、pH等因素有关，OM通过Feox作用影响吸磷能力。磷吸持饱和度（及尺b腼司是土壤磷活性水平和土壤吸磷能力的综合指标，它与磷释放量呈极显著正相关（p<0 .001）.土壤磷释放与土壤性质的关系可以用多元回归方程（场T’Ihan。=一4.771+2 .056 xolsen卜0.02科x为rBC，扩=0 .729**，N=30）描述。 三峡水库消落区主要土壤样品全磷含量范围为0.021司.085%，均值为0.058%伽月0）。olsenP含量范围为1 .87阳35.6m眺g，均值为11.7m叭g。早地全磷略高于水田:早地有效磷比水田高78.5%;刀咫坛表现为早地>水田;黄壤的C匆一P、C扩P含量较低，冲积土的CaZ一、Ca吕wep含量较高，早地的磷活性及水平高于水田，冲积土磷活性及水平较高.A玩、Feox、OM表现为水田>早地，黄壤的OM、Feox、A城高于紫色土和冲积土，冲积土的OM、F旬x、Alox较低，水田的吸磷能力高于早地，黄壤吸磷能力强，冲积土吸磷能力弱.三峡水库消落区土城磷释放风险表现为早地>水田，冲积土>紫色土>黄壤。 消落区土壤在模拟淹水条件下，土壤磷有较强的释放能力。当淹水4天和28天时，上覆水总磷浓度分别有47.7%和90肠的土壤?更多还原

【Abstract】 Aim at various defects of some past researches on both release characteristic of phosphorus from flooding soil or periodically flooding soil and its environmental effect, typical soils from water level fluctuating zone of the Three Gorges Reservoir were studied in this research, by conducting release and sorption experiments of phosphorus under simulated inundation condition,release speed and load of soil were confirmed. Furthermore, after systematically determination of soil character under periodically flooded condition, combined with the results from sorption-desorption experiments, we studied the release mechanism of phosphorus from different soil type and land using, and some indexes could represent phosphorus transportation in water-soil interface were also proposed.Results showed, during simulated flooding periods, the relationship between pH of water column and pH of soil was positively correlation, while the specific conductance climbed up with the prolonging flooding periods. The main metal ions, which released from soil were Ca2+ and Mg2+, and the concentrations of released Fen+ and Mn2+ were relatively low, while K+ showed negative-desorption.Alternately dried and flooded condition has significant influence on the redox potentials (Eh), pH of soil and amorphous oxides, and the change of soil character under that condition differed from different soil type, as well as land using. During flooding periods, soil pH tends to be neutral, and its Eh drops down significantly. For soil has a high organic matter (OM) content, the decrease speed and range are high, which could drop to the extend of -250-300 mV. When the inundated soils were dried, the value of its pH and Eh could resume to a level before inundation. Besides, the oxalate-extractable iron (Feox) concentration in soil increased significantly after flooding. The mean value of Feox in 30 soils sampling increased 121% compared with that of before flooding. The increase range of Feox of upland soils is higher than that of paddy soils. After 15 upland soils were flooded, the mean value of Feox raised from 1070mg/kg to 4030mg/kg, which increased 277% compared with that of before flooding. However, after the soil flooding was dried, its Feox content is similar with the value before floodong. Compare to the flooding effect on Feox, the concerning effect on the oxalate-extractable aluminum (Alox) is not so evident, flood could increase the Alox concentration in soil, however, the change is insignificant. After the flooding soil was dried, its Alox concentration dropped down, which is significantly different from the value before flooding and during flooding periods. The degree of saturation with phosphorus (DPS) shows significant difference under alternately dried and flooded conditions. DPS decreased during flooding periods, and increased after the soil flooding was dried.Alternately dried and flooded condition also has significant impact on Olsen P in soil. Soil with different type, as well as different land using, shows various levels of Olsen P increase during flooding periods. After the flooding soil was dried, its Olsen P content resumed to the level beforeflooding. However, for upland soils, the samples after flooding had a lower Olsen P level than that of before flooding. The influence of dried-flooded cycle on alkaline yellow soil is insignificant. During the whole procedure (135 days) ,phosphorus applied to soils mainly transformed to Ca2-P, Ca8-P, Al-P and Fe-P, while only a tiny fraction transformed into O-P and Ca10-P. Flooding could increase the concentration of Ca2 -P,Ca8-P and Al-P, while drying could increased Fe-P concentration.Alternately dried and flooded condition has significant influence on soils isothermal sorption-desorption ability of phosphorus. The adsorption maximum of phosphorus (qm) and the maximum buffer capacity (MBC) of soil follow the order of flooding > drying after flooding > unflooding. The qm of upland purple soil increased 413% after floodig, while the MBC of paddy yellow soils soil increased 10更多还原