小叶章湿地土壤对磷的净化效率模拟

选取三江平原小叶章(Calamagrostis angustifolia)湿地,模拟了不同植物生长期、不同净化阶段、不同土层的小叶章湿地土壤对磷的净化效率及地表水磷输入量对土壤净化效率的影响.结果表明:小叶章的成熟期内湿地土壤对磷的净化效率最高;在各种因素的共同影响下小叶章生长期对土壤净化磷效率的影响不显著;总磷(TP)输入浓度由10 mg·L-1增加到20 mg·L-1时,小叶章湿地土壤对磷的净化效率提高;TP输入浓度为20 mg·L-1时,净化前期和中后期小叶章湿地土壤对磷的平均净化效率分别为4.56和-0.71 mg·kg-1·d-1,差异显著;11P输入浓度为20 mg·L-1时,小叶章湿地0～10、10～20和20～40 cm土壤层对磷的平均净化效率分别为2.27、-0.87和0.51 mg·kg-1·d-1,但差异不显著.     

人工湿地运行过程中有机物质的积累

研究了杭州西湖边人工湿地污水净化生态工程经一年多运行后有机质的积累情况,同时测定了基质的孔隙度和水力传导性,结果表明,人工湿地在运行一年后总有机质积累达到0.658kg/m^2,60%有机质积累主要在0-100mm。湿地上,下池有机质积累有明显差异。且随着基质中的深度和离入水口的距离都呈下降趋势。两池中下层孔隙度均高于上层,并存在显著差异。有机质积累对水力传导性和净化效果均有一定影响,可通过定期收割植物和清除枯落物来维持湿地的长期运作能力。     

生活污水慢渗生态处理对土壤及杨树生长的影响

为了观测生活污水杨树林地处理对土壤和林木生长的影响,2008—2009年在郑州市龙湖镇,采用不同水力负荷(0、3、6、9、12、15cm/周),进行了污水慢渗生态处理试验。测定了污水处理期间杨树地上部分生长量,对表层(0—40cm)和下层(40—100cm)土壤理化性质进行了分析。选用土壤容重、有机质、全氮、全磷、全钾、速效氮、速效磷、速效钾作为土壤质量因子,运用土壤质量综合指标评价不同处理表层土壤质量,对下层土壤的理化性状的变化进行了研究。结果表明:在3—9cm/周水力负荷时,表层土壤质量综合指标值(QI值)和杨树地上部分生长量均随着水力负荷的增加而增加,在9cm/周水力负荷时达到最大;水力负荷大于9cm/周,QI值和杨树地上部分生长量随着水力负荷增加而降低。在水力负荷较低时,污水处理对下层土壤性状影响较小,水力负荷大于9cm/周,污水处理对下层土壤性状产生了不良影响。生活污水杨树林地处理比较适宜的水力负荷是6—9cm/周。     

鄱阳湖湿地景观恢复的物种选择及其对环境因子的响应

湿地是重要的生态系统,对人类和野生生物都具有极其重要的价值。由于自然因素的变化和人类活动的干扰,湿地退化严重。近年来,湿地恢复已成为世界环境问题改善的重要工具之一。选择适用的湿地植物是退化湿地恢复的关键途径。本文以鄱阳湖湿地为研究对象,通过专家赋值、野外调查、定位观测等方法,筛选了苦草、野菱、芦苇、苔草等25种鄱阳湖常见植物作为湿地景观恢复的优先物种。对苦草、黑藻、菹草、菖蒲、芦苇等5种植物对环境因子的响应进行观测。结果表明,苦草在清水环境130-140cm处的生长最好;黑藻在清水环境中100-110cm处的生长最好;菹草在不同水深(50-160cm)下都能够生长,菹草高度随水深增加而增加;菖蒲具有一定的耐淹能力(< 80cm),但完全淹水(水深100-120cm)明显影响到菖蒲根状茎萌发、幼苗生长和生物量的积累;芦苇根状茎萌发对水深要求严格,土壤要湿润且透气性良好才是芦苇萌发的最好条件,芦苇根状茎萌发前淹水超过20 cm其萌发将会受到明显抑制,淹水超过30 cm则无法萌发。通过对沉水植物的透明度研究表明,植物对水质的透明度都有一定的要求,透明度较好更利于湿地植物的生长发育。     

耕作深度对蔗地土壤物理性状及甘蔗产量的影响

探讨蔗地机械化耕作深度对耕层土壤物理性状及甘蔗产量构成因子的影响,阐明深松作业的针对性土壤区位和障碍因子,可为甘蔗良好耕层的构建和土壤改良策略的制定提供科学依据.本研究设置3种深松作业深度(35、40和45 cm),以不深松为对照,对蔗地土壤物理性状(紧实度、容重、含水率、孔隙度、三相容积率)和甘蔗产量构成因素及蔗茎产量等指标进行研究.结果表明: 耕作作业深度与蔗地土壤结构特性及甘蔗产量的改善提升效应呈显著正相关.深松能够打破犁底层,显著降低土壤紧实度和容重,减小机械作业相应的贯入阻力和抗剪强度,尤其对20～30 cm土层的上述因子具有显著改善效应,对甘蔗高产意义重大.深松显著提高了30 cm以内土层的液相容积率,增大了土壤水分库容,使10～30 cm土层的水分指标显著改善.10～30 cm土层是深松对耕层土壤固相容积率改善效应最显著的区位.耕作深度的增加对甘蔗有效茎数、株高、蔗茎产量及蔗糖含量具有显著的促进效应.鉴于蔗区当前较普遍的机具装备水平,我国适宜蔗区实施机械化深松的作业深度标准应不小于40 cm.     

莫莫格湿地芦苇生理生态特征对水深梯度的响应

通过在莫莫格湿地测量芦苇的生态特征、叶绿素含量和光化学效率,对水深梯度影响芦苇生理生态的规律进行了分析.芦苇株高、生物量、叶绿素含量以及最大光化学效率与湿地水深呈显著正相关关系,这些指标随水深的增加而提高;芦苇盖度与水深呈负相关关系,随着水深增加,芦苇盖度逐渐降低;芦苇最大光化学效率在6～7月份达到最大,进入8月后下降,同时芦苇生长减慢.结果表明,6～7月份是芦苇生长的关键时期,应尽量满足芦苇需水要求.15 cm水深是芦苇最小生态水位,而35～45 cm的水深能确保芦苇最佳生长状态,是芦苇生长的最适宜生态水位.     

莫莫格湿地芦苇对水盐变化的生理生态响应

认识湿地植物对不同水盐环境的生理生态响应特征和规律,是确定湿地生态需水阈值的关键,为湿地生态需水量计算及生态恢复提供科学依据.通过对莫莫格湿地水盐环境因子与芦苇生理生态特征指标进行调查研究,并利用国际通用植被数量分析软件CANOCO4.5对其关系进行了冗余度分析(RDA).结果表明:湿地水深、Na+,HCO(3)含量3个环境因子组合对芦苇生理生态特征变异的解释量达到54.7％,说明这3个变量是影响芦苇生理生态特征变异的重要因子,水深是关键驱动因子.水深与芦苇株高、生物量、叶绿素含量、最大光化学效率Fv/FM以及光化学性能指数PIABS成显著正相关,随着水深的增加,芦苇株高、生物量以及叶绿素含量等逐渐增加.Na+含量、HCO(3)含量与芦苇生理生态特征的相关性没有达到显著水平.因此,中轻度盐碱湿地生态恢复需要重点考虑水深条件对湿地生态的影响,其次是水质( Na+/HCO(3))因素的影响作用,确保适宜生态水位,满足生态恢复需要.     

两栖榕在人工湿地的生长特性及其对污水的净化效果

研究了两栖榕在潜流型人工湿地的生长特性及其对污水的净化效果。一年多的实验表明,生长在人工湿地的两栖榕具有发达的侧根和不定根,保持正常的净光合速率,蒸腾速率,根系活力生长速率。两栖榕人工湿地对TN,TP,CODCr和BOD5的去除率分别为54．2％、40．9％、72．4％和74．3％,与无植物系统相比较,去除率分别提高了17％、12％、10％和11％,此外,两栖榕人工湿地系统中,水力停留时间对去除率果有一定影响。     

水深梯度下湿地植被空间分布与生态适应

采用模糊数学排序方法对黄河三角洲国家级自然保护区不同水深梯度下芦苇湿地植被进行了．研究,揭示了水深对植被空间分布的影响。结果表明,不同水深梯度下植物生境和群落类型都表现出较大差异,水深-30～40cm,为水陆过渡地带,旱生、水生植物并存,物种最为丰富,该段水深上植被盖度最大;水深在-30-50cm,由于地下水深较低,该段水深是研究区盐碱化程度最大处;水深低于-50cm时,地表较为干旱,盐碱化程度有所降低,植被类型被耐干旱植被代替。不同水深梯度影响了土壤水分、空气和土壤的生物、物理、化学过程,引起植被生长环境中土壤水分、盐碱化程度的改变,进而对植被空间分布和植被生态特征产生影响。     

水深梯度对钝脊眼子菜生长和繁殖的影响

水深是影响湿地植物生长和分布的一个重要限制性因子,该研究以具有典型异型叶性的钝脊眼子菜(Potamogeton octandrus)为对象,通过分析浅水处理(10 cm和30 cm)和深水处理(50 cm和70 cm) 4个水深梯度下幼苗生长、生物量及繁殖策略等,探讨钝脊眼子菜在不同水深条件下的适应机制和表型可塑性。结果表明,钝脊眼子菜植株到达水面后出现异型叶,相对生长率显著降低,且与水深梯度呈正相关。钝脊眼子菜的株高随着水深的增加呈现爆发式的增长,10 cm水深的总茎长显著低于其他水深处理。水深对节间数也有显著性影响,其中,30 cm组处理节间数最多;而深水处理组的节间长和生物量均显著高于浅水处理组。分蘖数在4组处理之间均表现出显著性差异,随着水深的增加呈现显著性递减。生物量和地上生物量分配则随着水深增加而明显增加。水深处理对有性生殖指标有显著性影响,水深的增加抑制其有性繁殖。其中,10 cm条件下无花序形成,50 cm水深下的花粉量、P/O比和花序数显著高于其他处理组,且深水处理的结实数和结实率均显著高于30 cm组。这表明钝脊眼子菜可通过调整形态可塑性和生物量分配,并采取不同的繁殖策略,以达到对水深的最佳适应,其中最适水深生长范围在50 cm左右。     

How hydrological and hydraulic conditions affect performance of ponds

During the 1990s there has been a growing interest in (re)constructed wetlands and ponds for treatment of agricultural runoff, sewage water, and stormwater. Some of these facilities, however, are poorly designed in terms of hydrological and hydraulic performance, which strongly affects their treatment capacity. This paper gives an overview of the present knowledge regarding pond hydraulics in terms of effective volume ratio and dispersion. The importance of these parameters is demonstrated by modelling of nitrogen removal in 13 ponds of different design. The results show that effective volume ratio has a clear influence, which increases when removal rate coefficients increase, while dispersion is of minor importance for removal efficiency. Finally, the concept of hydraulic efficiency is discussed in the light of these results.     

人工湿地对胡子鲇养殖水体循环净化的研究

以大型观光植物美人蕉-砾石为基础的垂直流人工湿地对胡子鲇养殖水体进行净化处理和回流使用,在胡子鲇养殖中测定了水体主要水质指标的变化,表明人工湿地对养殖水体净化效果显著,养殖期间BOD5、COD、TN的平均去除率分别为81.77%、55.55%和65%,净化后水质部分符合渔业用水标准,可以循环利用.对照池水体由于BOD5、COD、TN得不到去除而持续增加,混浊度显著高于实验池,并出现水华.这种水体循环养殖模式具结构简单和易推广等优点.     

Is consolidation drainage an indirect mechanism for increased abundance of cattail in northern prairie wetlands?

In the Prairie Pothole Region of North America, disturbances to wetlands that disrupt water-level fluctuations in response to wet–dry climatic conditions have the potential to alter natural vegetative communities in favor of species that proliferate in stable environments, such as cattail (Typha spp.). We evaluated the effect of water-level dynamics during a recent fluctuation in wet–dry conditions on cattail coverage within semipermanently and permanently ponded wetlands situated in watersheds with different land use and amounts of wetland drainage. We found that ponded water depth increase was significantly greater in wetlands where water levels were not near the spill point of the topographic basin, where banks were steeper, and in larger wetlands where past dry conditions had less influence on change in pond area. Proportion of the wetland covered by cattail was negatively correlated with increased water depth, bank slope and pond area. Our observations provide evidence that cattail coverage in prairie wetlands is regulated by water-level fluctuations and that land use surrounding the wetland might have an indirect effect on cattail coverage by altering water-level response to wet–dry climate conditions. For example, drainage of smaller wetlands into larger wetlands that are characterized by more permanent hydroperiods, leads to stabilized water levels near their spill point and is therefore a potential mechanism for increased cattail abundance in the northern prairie region.     

Impact of water depth on root morphology of Juncellus serotinus (Cyperaceae)

Root morphological adaptation is an important mechanism for wetland plants to adapt to environmental conditions. The objective of this study was to investigate the impact of water depth on biomass allocation and root morphology (including root mean diameter, root length, root surface area and root volume) of a wetland plant species, Juncellus serotinus (Cyperaceae). Four levels of water depth were chosen: 10, 30, 50 and 70 cm. Due to the enormous root system, and for easy observation, five groups were used according to the distance from the rhizome: 0–5, 5–10, 10–15, 15–20 and longer than 20 cm (> 20 cm). Results showed that with increasing water depth plant total biomass and root biomass decreased significantly (p < 0.05), and that biomass was mainly allocated to shoots resulting in decreased root to shoot ratio. Root morphology parameters also changed significantly with increasing water depth (p < 0.05). Root mean diameter in all treatments and all other root morphology parameters decreased with increasing distance from the rhizome, while maximum root length, root surface area and root volume in 10 and 30 cm occurred between 5 and 15 cm from the rhizome. The results indicate that shallow water (less than 30 cm in depth) is favorable for the development of J. serotinus root system, and that root morphological characteristics shift with increasing distance from the rhizome.     

A modeling approach for mixing and reaction in wetlands with continuously varying flow

Prior investigations have examined steady-state flow in surface flow treatment wetlands, with mixing modeled as advection-dominated, and reaction calculated using flow-weighted averages over collections of stream tubes with different velocities. This work extends these concepts to non-steady flow conditions and temporally varying inlet concentrations. The essential construct that makes the approach feasible is definition of a set of reference (steady) state conditions under which the residence time distribution (RTD) and stream-tube specific rate constants are defined. Residence time in any stream tube under non-steady flow is treated as a linear function of its reference-condition residence time, and the overall wetland retention time under both mean and varying flow regimes. Outlet concentration is found by convolution of the reaction term with a varying inlet concentration function. For real-world flow and concentration data collected at discrete points in time, integration for outlet concentration is approximated using linear interpolation to generate inlet concentrations and velocities at intermediate points in time. The approach is examined using data from the literature. Vegetation density and depth distributions are seen as central in determining mixing and treatment performance.     

不同设计参数对雨水湿地水量水质的调控规律

基于前置塘+二阶表流湿地组合的雨水湿地系统的室内降雨径流模拟实验数据,研究了不同降雨重现期、不同常水位、不同湿地出水口高度、不同湿地级数以及不同污染负荷等设计参数对湿地水量水质调控效果的影响规律,研究结果表明:前置塘+二阶湿地组合的雨水湿地系统通过截留、缓冲和存储作用,对不同降雨径流条件下的产流时间、流量、径流削减率具有多重调控作用,延长了污染物在流域内部的滞留时间,减少了污染负荷的输出,对降雨径流过程中污染物总量具有较好的截留效果。并随设计参数的变化有明显的变化规律。随着降雨重现期的增加,湿地出水口高度的降低,湿地常水位的增加,以及湿地级数的减少,湿地出流量增加,产流时间提前,出流持续时间延长,径流削减率降低。从场次降雨污染物平均浓度(EMC)削减率上看,降雨过程中,雨水湿地仅对SS削减比较明显,削减率达70%—80%,对其他污染物浓度的削减效果不明显。从场次降雨污染物总量削减率来看,雨水湿地对降雨径流污染物具有较好的截留效果,并随着降雨重现期减少、湿地出水口高度增加、湿地常水位降低,呈逐渐增加趋势。     

A hydrologic assessment of the Everglades Nutrient Removal Project, a subtropical constructed wetland in South Florida (USA)

The Everglades Nutrient Removal Project (ENRP), a 1544-ha constructed wetland in south Florida, was intensively monitored throughout its five-year operational history. Water budgets for the ENRP and each of its interior treatment cells were dominated by surface flows (≥85% of inflows; ≥68% of outflows) with smaller contributions from precipitation, evapotranspiration, groundwater flux, and change in storage. The mean water depth, hydraulic loading rate for surface water, and nominal hydraulic retention time for the entire wetland were 0.6 m, 3.1 cm d⁻¹ and 17.7 d, respectively, and were comparable to values anticipated in design. The east flow-way was slightly shallower (0.2 m) and received proportionately more flow (61%) than the west flow-way. The hydrology of other treatment wetlands is often driven by surface flows. All treatment cells in the ENRP were to some extent hydraulically short-circuited. There was net groundwater inflow to the ENRP from Water Conservation Area 1 (WCA-1) resulting from significant head differences between these wetlands. Groundwater outflow to the adjacent farmlands was greatest in Cell 2 and substantially exceeded groundwater inflow. All hydrologic parameters exhibited seasonality to some extent; fluctuation in water depth and groundwater inflows corresponded with the seasonal change in stage in WCA-1. Errors in the ENRP and individual cell water budgets were generally less than 10% and within the range of errors for water budgets from other wetlands.     

Effects of variable hydroperiods and water level fluctuations on denitrification capacity, nitrate removal, and benthic-microbial community structure in constructed wetlands

The hydrologic character of wetlands is one of the attributes by which they are defined. There are, however, conflicting reports about the detrimental versus beneficial responses of wetland systems to water level fluctuations and variable hydroperiods. We conducted water level and hydroperiod fluctuation studies in full-scale experimental wetlands in order to determine the effects of hydraulic operation on wetland performance (in terms of nutrient removal), and benthic-bacterial community function (in terms of denitrification potential, DNP) and structure (via terminal restriction fragment length polymorphisms, T-RFLP). In our comparison, detention time was the controlling factor for nitrate removal at the system level. However, widely fluctuating water levels and variable hydroperiods did not diminish either the nitrate removal capacity of the experimental wetlands, or the size or composition of benthic-bacterial communities relative to the more stable water level systems. Rather, significant differences in denitrification potential rates, bacterial cell densities, and benthic community structure were a function of sampling location within the experimental wetlands regardless of hydraulic operation. The results of this study support the need for reconsidering the hydraulic criteria for wetland delineation.     

Hydrodynamics of vertical subsurface flow constructed wetlands: Tracer tests with rhodamine WT and numerical modelling

Typical unsteady unsaturated conditions can profoundly affect the hydrodynamics of vertical subsurface flow constructed wetlands. In this study we analyzed the hydrodynamics of a 33 m² vertical flow pilot plant, treating municipal secondary effluents. Three different saturation conditions were analyzed under several constant flux regimes: complete saturation, partial saturation with the free water table 20 cm over the bottom of the bed, and complete drainage. Tracer tests were performed in steady state conditions by dosing rhodamine WT as square input signals. Breakthrough curves were analyzed by means of both a classical residence time distribution analysis and an originally developed numerical plug-flow model with longitudinal dispersion adapted to the unsaturated conditions. We found that the degree of global mixing in the vertical flow constructed wetland increased as the water content increased; this effect was controlled by the hydraulic residence time of the system. Conversely, the degree of local mixing was inversely affected by water content; the dispersivity was 4.5, 10, and 14 cm for fully saturated, partially saturated and draining conditions, respectively. We explain the dependency of dispersivity on water content in physical terms; however, further studies are needed to mathematically include this relationship in numerical models that describe the behaviour of vertical flow constructed wetlands.     

Nitrate removal from groundwater using constructed wetlands under various hydraulic loading rates

This study set up two flow-through pilot-scale constructed wetlands with the same size but various flow patterns (free water surface flow (FWS) and subsurface flow (SSF)) to receive a nitrate-contaminated groundwater. The effects of hydraulic loading rate (HLR) on nitrate removal as well as the difference in performance between the various types of wetlands were investigated. Nitrate removal rates of both wetlands increased with increasing HLR until a maximum value was reached. The maximum removal rates, occurred at HLR of 0.12 and 0.07 m d(-1), were 0.910 and 1.161 g N m(-2)d(-1) for the FWS and SSF wetland, respectively. After the maximum values were reached, further increasing HLR led to a considerable decrease in nitrate removal rate. Nitrate removal efficiencies remained high (>85%) and effluent nitrate concentrations always satisfied drinking water standard (<10mg NO3-NL(-1)) when HLR did not exceed 0.04 m d(-1) for both FWS and SSF wetlands. The first-order nitrate removal rate constant tends to decrease with increasing HLRs. The FWS wetland provided significantly higher (p<0.05) organic carbon in effluent than the SSF wetland, while the SSF wetland exhibited significantly (p<0.05) lower effluent DO than the FWS wetland. However, there was no significant difference (p>0.05) in nitrate removal performance between the two types of constructed wetlands in this study except in one trial operating at HLR of 0.06-0.07 m d(-1).