白洋淀湿地氮素转化和N2O排放特征研究

通过对华北地区最大的湖泊湿地白洋淀近1年的野外观测,对湿地上覆水、沉积物/土壤中各种形态氮以及反硝化作用产物N2O排放通量的时空变化进行了系统研究。研究结果表明,白洋淀湿地对氮素污染物铵态氮的去除能力较强,平均去除率为77.1%。湿地中氮素的迁移转化过程时空变化明显,夏季是其氮素转化的快速期。湿地是温室气体N2O的排放源,夏季其排放通量最大,占全年排放通量总和的62.1%。其中湖滨带是整个湿地生态系统中氮素转化的活跃区,N2O年内平均排放通量高达109μg·m-2·h-1。由此可见,良好的湖滨带有利于湖泊富营养化的自然恢复。     

白洋淀典型湿地氮素转化和N2O排放特征研究

本文以华北地区最大的湖泊湿地-白洋淀为对象,通过为期近1年的野外观测,对白洋淀典型湿地上覆水、沉积物/土壤中各种形态氮以及反硝化作用产物N2O排放通量的时空变化进行了较系统的研究。研究结果表明,白洋淀湿地对氮素污染物铵态氮的去除能力较强,平均去除率为77.1%;白洋淀湿地中氮素的迁移转化过程时空变化明显,夏季是其氮素转化的快速期,湖滨带是整个白洋淀湿地生态系统中氮素转化的活跃区;有机质、营养盐丰富的白洋淀湿地是温室气体N2O的排放源,夏季N2O排放通量最大,占全年排放通量总和的62.1%,湖滨带是N2O排放的核心区,年均排放通量高达109µg•m-2•h-1。由此可见,白洋淀典型湿地系统中植被型湖滨带是氮素的一个很好的“处理器”,良好的湖滨带有利于湖泊富营养化的自然恢复。     

水生植物模拟湿地对受污河水中氮素去除的初步研究

分别以芦苇、茭草和宽叶香蒲构建人工模拟湿地系统,开展关于湿地中水生植物氮素去除效果的对比研究。研究结果表明：（1）人工湿地对污染河水中的无机氮有很高的去除效果,但不同植物的去除率有所不同;（2）铵态氮和硝态氮的去除是影响湿地系统总氮去除率的重要因素,且铵态氮的去除起主导作用;（3）芦苇特殊的根系结构增加了湿地系统中溶解氧的含量,进而改善水中各种动物、微生物的生活环境;（4）植物吸收不是湿地氮去除的主要途径,但它的存在足以直接和间接的影响到水体中各种形态氮素的转化以及系统中微生物的硝化／反硝化过程的进行。     

东平湖酶活性与温室气体通量及其影响因素

为研究东平湖沉积物酶活性与水体温室气体排放通量特征及其影响因素,2018年9月布设23个采样点,采集表层沉积物和表层水样品,分析沉积物中脲酶、蔗糖酶和碱性磷酸酶活性,采用顶空法和双层扩散模型估算水气界面N2O、CO2排放通量;采用相关分析、多元线性回归法探讨影响酶活性与温室气体排放通量的主要因子.结果表明:沉积物脲酶、...     

黄河三角洲湿地芦苇和棉田土壤呼吸试验研究

为探究温带河口湿地原生芦苇群落和人工棉田群落的土壤碳通量特征及其与各环境因子的关系,利用Li-8100开路式土壤碳通量测量系统对黄河三角洲湿地棉田和芦苇两种植被覆盖下的土壤呼吸速率进行了监测,同时测定了土壤和大气的温度、湿度,分析了两种不同利用方式的土壤呼吸变化规律及相关影响因子。结果表明:棉花群落和芦苇群落样地的土壤呼吸速率日变化曲线均呈不对称的单峰形式,且变化趋势基本相同,在12时-14时达到峰值,在6时-8时到达谷值,棉田的土壤呼吸高于芦苇地,且平均呼吸速率表现为棉花群落(0.927μmol/(m2·s))高于芦苇群落(0.705μmol/(m2·s)),这证明人为耕作会增加土壤碳通量的释放,导致碳排放量的增加。经相关性分析得出,土壤温度和大气湿度是影响棉花群落和芦苇群落土壤呼吸日变化的主要因素,其中前者对芦苇地影响更大,而后者对棉田的影响更大。     

黄河三角洲湿地土壤呼吸及其环境因子分析

为了给黄河河口湿地生态系统碳收支的动态模拟提供参数,进而为河口湿地优化管理提供科学依据,利用土壤碳通量测量系统LI-8100A对黄河三角洲湿地柽柳、芦苇、碱蓬3种典型植物群落的土壤呼吸速率进行监测,同时测定了湿度、温度等,分析了3种群落的土壤呼吸日变化特征及相关影响因子。结果表明:碱蓬、柽柳、芦苇3种植物群落土壤呼吸速率日变化曲线都呈单峰形式,且峰值出现的时间基本一致,都在14:00左右达到最大,最小值都出现在6:00左右。单因子回归分析表明,各环境因子与土壤呼吸速率间的关系均可用二次多项式模型来拟合。柽柳群落土壤呼吸速率主要受土壤温度变化的影响,碱蓬群落土壤呼吸速率受大气温度的影响较湿度的影响大,而大气温湿度和土壤温湿度对芦苇群落土壤呼吸速率均有较明显的影响。     

三门峡库区芦苇湿地蒸散量及其影响因子分析

根据三门峡库区长时间序列气象观测数据,采用FAO推荐的标准化Penman-Monteith公式,对库区湿地优势种群芦苇的实际蒸散量ETc进行了估算,分析了芦苇湿地蒸散量的年内和年际变化规律,并对影响芦苇湿地实际蒸散量的主要环境因子进行分析。结果表明:夏季三门峡库区芦苇湿地的实际蒸散量较大,冬季较小,在6月达到年度最高值,为190.17 mm;库区多年平均(1957—2010年)芦苇湿地实际蒸散量为1 056.59 mm,54 a中最高为1 278.23 mm(1959年),最低为818.05 mm(1984年);库区湿地ETc与各环境因子之间存在多元线性回归关系。     

湿地反硝化作用研究进展

湿地反硝化作用是复杂的物理化学及生物作用过程，存在诸多影响因素。土壤硝酸盐浓度、有机质含量、温度、氧化还原电位、土壤中空气分压、水分、pH、反硝化细菌的活性和分布密度等都会影响反硝化作用的效率。微生物作为反硝化作用的主要执行者已成为深入研究反硝化作用机理的重要环节，但反硝化作用的产物N2O是引起全球变暖的因素之一。通过对湿地反硝化作用研究现状的分析，提出了当前国内外在反硝化作用研究方面存在的不足。并对今后的研究重点进行了展望。     

黄河中游芦苇群落土壤CO_2排放及其影响因素

对黄河中游滨河湿地芦苇群落土壤CO_2排放速率数据进行采集,按相对水位、气温及群落状况进行筛选,旨在评价研究区CO_2排放水平,分析气候变化对其造成的影响。各条件下,低矮芦苇群落土壤CO_2排放速率平均为353.30 mmol·m~(-2)·h~(-1),成熟群落的为17.62 mmol·m~(-2)·h~(-1);随水位上升,CO_2排放速率逐渐下降,但成熟群落的在相对水位为-10~10 cm时有上升波动,低矮芦苇群落土壤的CO_2排放速率下降幅度大于成熟群落的;随气温上升,各类型湿地CO_2排放速率有下降趋势,其变化幅度排序为低矮干低矮湿成熟群落;低矮芦苇群落CO_2排放速率受水位、气温的影响都远大于成熟群落的。     

灌区农田温室气体减排潜力研究 ——以江苏省濉汴河灌区为例

农业生产活动具有碳源和碳汇的双重效应,为研究濉汴河灌区温室气体减排潜力,对灌区采取适当的减排固碳措施提供依据和建议,分别从稻田 CH4 排放、农用地 N2O 排放、农用柴油 CO2 排放、排灌电力生产造成的 CO2 排放以及作物生长季碳通量等方面,估算灌区2021 年温室气体排放量和吸收量,并针对相关指标进行敏感性分析,研究分析其对灌区温室气体排放量的影响程度。结果表明：濉汴河灌区 2021 年温室气体净排放量约为 7.21 万 t CO2 当量,且主要的排放组成是农田释放的 CH4 和 N2O。     

Evaluation of constructed wetlands by wastewater purification ability and greenhouse gas emissions.

Domestic wastewater is a significant source of nitrogen and phosphorus, which cause lake eutrophication. Among the wastewater treatment technologies, constructed wetlands are a promising low-cost means of treating point and diffuse sources of domestic wastewater in rural areas. However, the sustainable operation of constructed wetland treatment systems depends upon a high rate conversion of organic and nitrogenous loading into their metabolic gaseous end products, such as N2O and CH4. In this study, we examined and compared the performance of three typical types of constructed wetlands: Free Water Surface (FWS), Subsurface Flow (SF) and Vertical Flow (VF) wetlands. Pollutant removal efficiency and N2O and CH4 emissions were assessed as measures of performance. We found that the pollutant removal rates and gas emissions measured in the wetlands exhibited clear seasonal changes, and these changes were closely associated with plant growth. VF wetlands exhibited stable removal of organic pollutants and NH3-N throughout the experiment regardless of season and showed great potential for CH4 adsorption. SF wetlands showed preferable T-N removal performance and a lower risk of greenhouse gas emissions than FWS wetlands. Soil oxidation reduction potential (ORP) analysis revealed that water flow structure and plant growth influenced constructed wetland oxygen transfer, and these variations resulted in seasonal changes of ORP distribution inside wetlands that were accompanied by fluctuations in pollutant removal and greenhouse gas emissions.     

温度和基质对人工湿地脱氮除磷效果的影响

构建由潜流人工湿地和表流人工湿地串联而成的复合人工湿地系统,研究了复合人工湿地脱氮除磷效果以及温度和基质对人工湿地脱氮除磷效果的影响。结果表明,复合人工湿地TP、氨氮平均去除率为33.64%、57.24%;水温降低会导致人工湿地氮磷去除率下降;基质为粗砂的潜流人工湿地脱氮除磷能力大于基质为砾石的潜流人工湿地。     

淡水湿地生态系统中微生物驱动氮转化过程研究进展

淡水湿地在全球氮循环中发挥着重要作用,微生物驱动氮转化过程对于淡水湿地的自然净化功能及水体富营养化控制具有重要意义。近年来,随着分子生物学和生物信息学等技术的快速发展,湿地系统的氮转化功能菌群和微生物多样性等方面的研究取得了突破性进展。与此同时,受气候条件变化及人类活动影响,淡水湿地系统生境因子出现了复杂变化,进而影响了功能微生物及其氮转化途径。氮循环过程中产生的一氧化二氮(N₂O)是仅次于二氧化碳(CO₂)、甲烷(CH₄)的第三大温室气体,与淡水湿地系统微生态及功能密切相关,其产生机理和影响因素也受到广泛关注。由于参与氮循环的微生物复杂多样、功能菌群协同作用机制不明,以及其受气候条件变化和人类活动影响显著,仍有必要深入研究淡水湿地系统的微生物驱动氮转化过程及机制。     

The role of plant uptake on the removal of organic matter and nutrients in subsurface flow constructed wetlands: a simulation study.

Plants in constructed wetlands have several functions related to the treatment processes. It is generally agreed that nutrient uptake is a minor factor in constructed wetlands treating wastewater compared to the loadings applied. For low loaded systems plant uptake can contribute a significant amount to nutrient removal. The contribution of plant uptake is simulated for different qualities of water to be treated using the multi-component reactive transport module CW2D. CW2D is able to describe the biochemical elimination and transformation processes for organic matter, nitrogen and phosphorus in subsurface flow constructed wetlands. The model for plant uptake implemented describes nutrient uptake coupled to water uptake. Literature values are used to calculate potential water and nutrient uptake rates. For a constructed wetland treating municipal wastewater a potential nutrient uptake of about 1.9% of the influent nitrogen and phosphorus load can be expected. For lower loaded systems the potential uptake is significantly higher, e.g. 46% of the nitrogen load for treatment of greywater. The potential uptake rates could only be simulated for high loaded systems i.e. constructed wetlands treating wastewater. For low loaded systems the nutrient concentrations in the liquid phase were too low to simulate the potential uptake rates using the implemented model for plant uptake.     

Constructed wetland attenuation of nitrogen exported in subsurface drainage from irrigated and rain-fed dairy pastures.

Nitrogen removal performance is reported for constructed wetlands treating subsurface drainage from irrigated and rain-fed dairy pastures in North Island, New Zealand. Flow-proportional sampling of inflow and outflow concentrations were combined with continuous flow records to calculate mass balances for the wetlands. Drainage flows from the irrigated catchment were 2.5-4 fold higher and N exports up to 5 fold higher per unit area than for the rain-fed catchment. Hydraulic and associated N loadings to the wetlands were highly pulsed, associated with rainfall, soil water status, and irrigation events. Transient pulses of organic nitrogen were an important form of N loss from the rain-fed landscape in the first year, and were very effectively removed in the wetland (> 90%). Median nitrate concentrations of approximately 10 g m(-3) in the drainage inflows were reduced by 15-67% during passage through the wetlands and annual nitrate-N loads by 16-61% (38-31 7 g N m(-2)y(-1)). Generation in the wetlands of net ammoniacal-N and organic-N (irrigated site) partially negated reduction in nitrate-N loads. The results show that constructed wetlands comprising 1-2% of catchment area can provide moderate reductions in TN export via pastoral drainage, but performance is markedly influenced by variations in seasonal loading and establishment/maturation factors.     

水平潜流人工湿地脱氮除磷研究进展

总结了水平潜流人工湿地的脱氮除磷机理,分析了进水水质、植物、基质、温度和水力停留时间这5种影响处理效果的主要因素,从不同角度论述了提高脱氮除磷效果所采取的措施,并探讨了水平潜流人工湿地存在的局限性和发展趋势。     

Nitrogen removal capacity of wetlands: sediment versus epiphytic biofilms.

Wetlands are important sinks for nutrients and constructed wetlands are current practice for stormwater treatment. For nitrogen, the main removal process is denitrification (microbial reduction of nitrate to nitrogen gas). The bacteria responsible for this process are mostly found in the sediments and in epiphytic biofilms growing on wetland macrophytes. This paper reports on a project which aimed at measuring denitrification potential in sediments and epiphyton in urban wetlands. This study showed that wetland sediments could support high rates of denitrification. Interestingly, the most polluted of the wetlands studied had the highest denitrification potential. The management implication from this result is that indicators of pollution, such as hydrocarbon levels, will not necessarily reflect the ability of a wetland to denitrify. Two of the wetlands were studied in more detail. Here the denitrification potential of the epiphyton on dominant macrophytes and sediments were measured. The results indicated that the potential denitrification activity of the epiphyton was comparable to those measured in the sediments. Hence, biofilms could play a significant part in removing nitrogen loads. This work contributes to a better knowledge of the functioning of wetlands. This will lead to improved design and management of wetlands used for treating stormwater.     

Groundwater discharge drives water quality and greenhouse gas emissions in a tidal wetland

Wetlands play an important role in the global carbon cycle as they can be sources or sinks for greenhouse gases. Groundwater discharge into wetlands can affect the water chemistry and act as a source of dissolved greenhouse gases, including CO₂ and CH₄. In this study, surface water quality parameters and CO₂ and CH₄ concentrations were evaluated in a tidal wetland (Hunter Wetlands National Park, Australia) using time series measurements. Radon (²²²Rn), a natural groundwater tracer, was used to investigate the role of groundwater as a pathway for transporting dissolved CO₂ and CH₄ into the wetland. In addition, water-to-air CO₂ and CH₄ fluxes from the wetland were also estimated. The results showed a high concentration of radon in wetland surface water, indicating the occurrence of groundwater discharge. Radon concentration had a strong negative relationship with water depth with a determination coefficient (R²) of 0.7, indicating that tidal pumping was the main driver of groundwater discharge to the wetland. Radon concentration also showed a positive relationship with CO₂ and CH₄ concentrations (R² = 0.4 and 0.5, respectively), while the time series data revealed that radon, CO₂, and CH₄ concentrations peaked concurrently during low tides. This implied that groundwater discharge was a source of CO₂ and CH₄ to the wetland. The wetland had an average water-to-air CO₂ flux of 99.1 mmol/(m²·d), twice higher than the global average CO₂ flux from wetlands. The average CH₄ flux from the wetland was estimated to be 0.3 mmol/(m²·d), which is at the higher end of the global CH₄ flux range for wetlands. The results showed that groundwater discharge could be an important, yet unaccounted source of CO₂ and CH₄ to tidal wetlands. This work has implications for tidal wetland carbon budgets and emphasizes the role of groundwater as a subsurface pathway for carbon transport.     

Temporal Dynamics of Nutrients (N and P) and Hydrology in a Lake Superior Coastal Wetland

Coastal wetlands on Lake Superior are hydrologically complex ecosystems situated at the interface of upland catchments and the oligotrophic lake. Little is known about nutrient dynamics within coastal wetlands or their role in modifying or contributing to nutrient fluxes from watersheds to Lake Superior. We conducted an intensive study of Lost Creek Wetland (LCW) near Cornucopia, WI, with the objective of determining influences of temporal variability in hydrology on dynamics and retention of N and P. We measured hydrologic inputs and distributions of inorganic and organic forms of nitrogen and phosphorus within LCW under hydrologic conditions ranging from summer base flow to spring snow melt. Our study confirms that the interrelationship between hydrologic connections to lake and tributary and seasonal variations in hydrology can regulate internal nutrient dynamics of coastal wetlands. The strength of hydrologic linkage of LCW to Lake Superior and tributary varied greatly among seasons, resulting in shifts in the relative importance of these nutrient sources and influencing spatial distribution of nutrients within the wetland. Ratios of inorganic nitrogen and phosphorus in the wetland were consistently low (< 16) indicating a potential for nitrogen limitation. Retention of inorganic nitrogen ranged from 11% to 94% and was positively related to hydraulic residence time which ranged from < 1 day during snow melt to 26 days in summer. Retention of total and soluble reactive phosphorus was generally lower than retention of inorganic nitrogen and was not related to hydraulic residence time.     

Emission of greenhouse gases from constructed wetlands for wastewater treatment and from riparian buffer zones.

We measured N2O, CH4 and CO2 fluxes in horizontal and vertical flow constructed wetlands (CW) and in a riparian alder stand in southern Estonia using the closed chamber method in the period from October 2001 to November 2003. The average rates of N20, CH4 and CO2 emission from the riparian gray alder stand were from -0.4 to 58 microg N2O-N m(-2) h(-1) and 0.1-265 microg CH4-C m(-2) h(-1), 55-61 mg CO2-C m(-2) h(-1), respectively. The average N2O-N emission from the microsites above the inflow pipes of horizontal subsurface flow (HSSF) CWs was 6.4-31 microg N2O-N m(-2) h(-1), whereas the outflow microsites emitted 2.4-8 microg N2O-N m(-2) h(-1). In vertical subsurface flow (VSSF) beds the same value was 35.6-44.7 microg N2O-N m(-2) h(-1). The average CH4 emission from the inflow and outflow microsites in the HSSF CWs differed significantly ranging from 640 to 9715 and from 30 to 770 microg CH4-C m(-2) h(-1), respectively. The average CO2 emission was somewhat higher in VSSF beds (140-291 mg CO2-C m(-2) h(-1)) and at inflow microsites of HSSF beds (61-140 mg CO2-C m(-2) h(-1)). The global warming potential (GWP) from N2O and CH4 was comparatively high in both types of CWs (4.8 +/- 9.8 and 6.8 +/- 16.2 t CO2 eq ha(-1) a(-1) in the HSSF CW 6.5 +/- 13.0 and 5.3 +/- 24.7 t CO2 eq ha(-1) a(-1) in the hybrid CW, respectively). The GWP of riparian alder forest from both N2O and CH4 was relatively low (0.4 +/- 1.0 and 0.1 +/- 0.30 t CO2 eq ha(-1) a(-1), respectively), whereas the CO2-C flux was remarkable (3.5 +/- 3.7 t ha(-1) a(-1). The global influence of CWs is not significant. Even if all the global domestic wastewater were treated by wetlands, their share in the trace gas emission budget would be less than 1%.