Agricultural non-point nitrogen pollution control function of different vegetation types in riparian wetlands： A case study in the Yellow River wetland in China

Riparian wetland is the major transition zone of matter, energy and information transfer between aquatic and terrestrial ecosystems and has important functions of water purification and non-point pollution control. Using the field experiment method and an isotope tracing technique, the agricultural non-point nitrogen pollution control function of di erent vegetation types in riparian wetland was studied in the Kouma Section of the Yellow River. The results showed that the retention of agricultural non-point nitrogen pollution by riparian wetland soil occurs mainly in top 0–10 cm layer. The amount of nitrogen retained by surface soils associated with three types of vegetation are 0.045 mg/g for Phragmites communis Trin Linn, 0.036 mg/g for Scirpus triqueter Linn, and 0.032 mg/g for Typha angustifolia Linn, which account for 59.21%, 56.25%, and 56.14% of the total nitrogen interception, respectively. Exogenous nitrogen in 0–10 cm soil layer changes more quickly than in other layers. One month after adding K15NO3 to the tested vegetation, nitrogen content was 77.78% for P. communis Trin, 68.75% for T. angustifolia, and 8.33% for S. triqueter in the surface soil. After three months, nitrogen content was 93.33% for P. communis Trin, 72.22% for S. triqueter, and 37.50% for T. Angustifolia. There are large di erences among vegetation communities respecting to purification of agricultural non-point nitrogen pollution. The nitrogen uptake amount decreases in the sequence: new shoots of P. communis Trin (9.731 mg/g) > old P. communis Trin (4.939 mg/g) > S. triqueter (0.620 mg/g) > T. angustifolia (0.186 mg/g). Observations indicated that the presence of riparian wetlands as bu ers on and adjacent to stream banks could be recommended to control agricultural non-point pollution.     

表流湖滨湿地磷素汇-源功能研究

对抚仙湖马料河湖滨湿地基质进行了室内静态模拟,计算了基质-水界面磷平衡浓度(EPCo),确定湿地基质是充当溶解性活性磷(SRP)的源项或是汇项功能.此外,结合野外监测试验,即在静态实验期间对湿地进出口处水体的SRP浓度及流量进行了连续测定,对静态实验结果进行了验证.野外监测结果表明,基质是作为SRP源项还是汇项,在很大程度上取决于进水流量及进水磷浓度.在暴雨情况下,由于雨水的稀释作用,出水SRP浓度低于进水浓度;当进水量较小时,则取决于进水SRP浓度.进水SRP浓度高于磷平衡浓度,即作为汇项;进水SRP浓度低于磷平衡浓度,即作为源项.用一个简单的模型预测了基质-水界面系统的相互作用及SRP转换过程.该模型中假设基质表层以上10cm为水-土界面层,SRP释放或吸附均在这个边界层进行.预测结果表明,基质-水完全混合时,基质无论是吸附或释放磷速率都很大,大部分SRP通量迁移转换都在1h之内完成;界面系统基质磷释放/吸附主要受控于基质-水界面处EPCo和上覆水SRP浓度梯度.     

根表铁膜在人工湿地磷去除中的作用及基质的影响

本研究构建了基质铁含量分别为10.68％、23.52％、44.20％和pH分别为7.0、7.3、7.9的3个水平潜流人工湿地实验系统,在对污水进行5个月处理后,分析了各系统不同区域植物根表铁膜形成量及植物、基质、根表铁膜中磷的分配量,以期阐明植物根表铁膜在人工湿地磷去除中的作用及基质的影响.结果表明,经过5个月的污水处理,3个系统植物根表都出现了明显的铁膜,形成量在15 ～35 g·kg-1(以根干重计)之间,铁膜的形成量受到基质铁含量和pH共同影响,基质铁含量的增加,同时pH不增加或增加幅度较小时,铁膜形成量会相应增加;但若含铁基质材料碱性较强时,基质铁含量增加导致pH大幅增加时,根表铁膜形成量则不随基质铁含量增加而增加3个系统铁膜中磷含量都在20g·kg-1(以根干重计)左右,相差不大,铁膜磷含量受基质对磷的竞争和植物吸收转移影响.各系统中,铁膜单位磷含量远高于植物和基质,并且分配在铁膜中的磷总量既高于植物地上部分也高于地下部分,甚至与植物地上和地下部分总和接近,表明铁膜在人工湿地中是一个重要的磷吸附截留部位,对人工湿地磷的去除具有重要作用.     

我国不同营养状态湖泊沉积物有机磷形态分级特征研究

研究了我国不同区域的7个不同流域特征、生态结构、污染程度的湖泊表层沉积物中有机磷（P_o）形态的分布特征,分析了P_o各组分与沉积物其他组分的关系和生物有效性. 不同湖泊沉积物中P_o相对含量的差异表明其来源和生物地球化学循环的不同,不同湖泊沉积物中有机质（OM）与P_o表现出显著相关关系（R>²=0.80,p>＜0.01）,除杞麓湖外,其它湖泊的OM与活性P_o、中活性P_o和非活性P_o也表现出显著相关关系（R>²分别为0.85、0.52、0.80,p>＜0.01）. 沉积物中有机磷中以中活性有机磷和非活性有机磷为主,其含量分别占总P_o的15.12%～66.73%和27.99%～77.72 %,活性P_o的平均相对含量为6.1%. 不同P_o组分的相对含量顺序为：residual P_o> HCl-P_o >fulvic acid-P_o>humic acid-P_o> NaHCO₃-P_o,平均的相对比例为8.3∶3.1∶2.2∶1.8∶1.0. 活性P_o和TP、P_i、P_o、NaHCO₃-P_i、NaOH-P_i呈显著正相关,非活性P_o与TP、P_o、NaOH-P_i呈显著相关,说明活性P_o很容易转化为生物可利用磷,同时非活性P_o也可能成为生物可利用磷的潜在源,非活性P_o只是化学溶解上的相对“惰性”,它仍具有潜在的生物活性.     

Phosphorus fractions and its release in the sediments of Haihe River, China

The amounts and forms of phosphorus (P) in surface sediments of Haihe River, Tianjin, North China, were examined using a sequential chemical extraction procedure. Five fractions of sedimentary P, including loosely sorbed P (NH4Cl-P), redox-sensitive P (BD-P), metal oxide bound P (NaOH-P), calcium bound P (HCl-P), and residual P (Res-P) (organic and refractory P), were separately quantified. The results indicated that the contents of di erent P fractions in the sediments varied greatly. The total P (TP) contents ranged from 968 to 2017 mg/kg. Phosphorus contents in NH4Cl-P, BD-P, NaOH-P, and HCl-P ranged from 6.7 to 26.6 mg/kg, 54.5 to 90.2 mg/kg, 185.2 to 382.5 mg/kg, and 252.3 to 425.5 mg/kg, respectively, which represented 1.2%–3.2%, 7.7%–13%, 33.3%–48.9%, and 36.2%–54.2% of the sedimentary inorganic P, respectively. For all the sediment samples, the rank order of P-fractions was Res-P > HCl-P > NaOH-P > BD-P > NH4Cl-P. The highly positive relationship between the amounts of P released from the sediments and those in the NH4Cl-P and BD-P fractions, indicated that NH4Cl-P and BD-P were the main fractions that can release P easily.     

滇池流域磷循环系统的物质流分析

研究营养元素在社会经济系统中的物质代谢结构及特征,是有效预防和控制地表水体富营养化的关键性分析技术之一.以滇池流域磷循环为研究案例,运用物质流分析方法建立了2000年流域静态物质流模型(PHOSFAD),并在此基础上识别出流域磷循环系统的总体结构特征,以及资源开采、化工生产、农业种植、畜禽养殖、居民生活等生产和消费部门的物质利用效率特征,为科学防治滇池水体富营养化提供了重要决策依据和参考.     

洞庭湖区湿地资源可持续利用途径研究

湿地具有特殊的生态功能和社会经济价值。洞庭湖区湿地垦殖强度大,造成了生态环境严重退化的恶果。研究表明:控制人口总量,退田还湖,建立湿地自然保护区,大力发展避洪耐涝型湿地特色产业是保护和合理利用湿地资源的有效途径,且已取得了良好的社会、经济、生态效益。由此认为,如何协调好人口、资源与环境的关系是实现湿地资源可持续利用的战略目标。     

南方涝渍地区退田还渔的一个实例分析

以江汉平原四湖涝渍地区的一个经围湖造田形成的典型农业微域为研究对象,在对其土壤和作物生长状况进行调查的基础上,探讨了退田还渔的必要性与具体方案。结果表明,对小型湖泊通过围湖造田所形成的农业微域,在人工排水和土地平整不充分的情况下,其地貌和土壤还残留有原有湖泊的影响,处于原湖泊低处的土壤表现出明显的沼泽化和严重潜育化的特征。在该地区种植水稻产量比正常地区减产达16%～26.8%。利用数量化理论Ⅰ确定了该地区适宜退田还渔的具体位置和面积。按照这一方案实施的结果,该地区从1997～2001年的5年中精养鱼塘面积增加9倍,养鱼的效益比种植水稻高5～10倍,还减轻了该地区夏季和冬季的排水压力。     

泉州湾河口湿地不同植被恢复下沉积物磷形态和酶活性特征

基于定位观测,研究了泉州湾河口湿地秋茄（Kandelia obovate,KO）、桐花树（Aegiceras corniculatum,AC）、以及秋茄+桐花树（KA）混交等3种植被恢复下沉积物磷形态、酶活性以及环境因子变化特征,并与养蛏滩涂（恢复前,SC）进行了比较,以评估不同植被恢复模式对沉积物磷库及酶活性的影响.结果表明：(1)植被恢复19年后,3种恢复模式下沉积物全磷（TP）和无机磷（IP）含量相较恢复前均呈上升趋势,其中KA最高,SC最低;而沉积物有机磷（OP）含量在不同恢复模式间差异不显著;不同恢复模式下,IP均是沉积物磷的主要形态,占TP的60%～73%;其中,沉积物氢氧化钠提取磷（NaOH-P）和盐酸提取磷（HCl-P）在KA处理下明显高于恢复前（SC）.(2)与恢复前相比,不同恢复模式下沉积物碱性磷酸酶、脲酶、蔗糖酶活性明显增加,总体表现为AC>KA>KO>SC,但过氧化氢酶在不同植被恢复模式下并无明显差异.(3)冗余分析结果显示,不同恢复模式下沉积物磷含量变化主要受酶活性（特别是碱性磷酸酶）及环境因子（pH、有机质、全氮等）的综合影响.泉州湾河口湿...     

Temporal variability of iron concentrations and fractions in wetland waters in Sanjiang Plain, Northeast China

Chemical forms, reactivities and transformation of iron fractions in marshy waters were investigated with cross-flow filtration technique to study the iron environmental behavior. Iron fractions were divided into four parts: acid-labile iron (pre-acidification of unfiltered marshy water samples, 0.7 μm), high-molecular-weight iron (0.7-0.05 μm), medium-molecular-weight iron (0.05-0.01 μm), and low-molecular-weight iron ( 0.01 μm). The cross-flow filtration suggested that iron primarily exist in both the 0.7 μm and 0.01 μm size fractions in marshy waters. Rainfall is the key for rain-fed wetland to determine fate of iron by changing the aquatic biochemical conditions. By monitoring the variation of iron concentrations and fractions over three years, it was found that dissolved iron and acid-labile iron concentrations exhibit a large variation extent under different annual rainfalls from 2006 to 2008. The seasonal variation for iron species proved that the surface temperature could control some conversion reactions of iron in marshy waters. Low- molecular-weight iron would convert to acid-labile iron gradually with temperature decreasing. The photochemical reactions of iron fractions, especially low-molecular-weight iron had occurred under solar irradiation. The relative proportion of low-molecular-weight in total dissolved iron ranging from 28.3% to 43.2% were found during the day time, which proved that the observed decreasing concentration of acid lability iron was caused by its degradation to low molecular weight iron.     

滇池沉积物磷内负荷及其对水体贡献的研究

在滇池全湖选取 1 1 0个采样点 ,调查了沉积物磷的营养状况 ;外海不同方位选取 6个采样点 ,研究了沉积物磷的赋存形态、剖面分布及其对水体的贡献 .结果表明 ,滇池沉积物表层 ( 0～ 5cm)总磷含量主要变化在 2～ 3g·kg-1 ,最大值为 6 6 6g·kg-1 .沉积物剖面表明 ,表层总磷含量远高于底层 ,在 0～ 1 0cm总磷含量随深度增加而迅速降低 .在点 4、点 5和点 6 ,不同形态磷的含量顺序为NaOH P ,Org P >HCl P >BD P >NH4Cl P .滇池南部 (S1、S2 )沉积物钙结合态磷含量较高 ,表现为HCl P >NaOH P ,Org P >BD P >NH4Cl P(表层 0～ 2 0cm) .沉积物表层 0～ 1 0cm活性磷含量很高 ,且随深度增加含量急剧下降 ,滇池北部沉积物具有很大的释磷潜力 .可溶性磷在水 土界面的浓度梯度为沉积物磷向水体扩散提供了条件 ,在外源减少的情况下沉积物磷内负荷将在一定时间内成为滇池富营养化的主导因子