Hydrologic and Water Quality Functions of a Disturbed Wetland in an Agricultural Setting1

Abstract: In 2006, we collected flow, sediment, and phosphorus (P) data at stream locations upstream and downstream of a small degraded wetland in south‐central Wisconsin traversed by a stream draining a predominantly agricultural watershed. The amount of sediment that left the wetland in the two largest storms, which accounted for 96% of the exported sediment during the observation period, was twice the amount that entered the wetland, even though only 50% of the wetland had been inundated. This apparently anomalous result is due to erosion of sediment that had accumulated in the low‐gradient channel and to the role of drainage ditches, which trapped sediment during the wetland‐filling phase. In the case of total P, the inflow to the wetland approximately equaled the outflow, although the wetland sequestered 30% of the incoming dissolved reactive P. The discrepancy is almost certainly due to net export of sediment. Many wetlands in the glaciated midwestern United States are ditched and traversed by low‐gradient channels draining predominantly agricultural areas, so the processes observed in this wetland are likely to be common in that region. Knowledge of this behavior presents opportunities to improve water quality in this and similar regions.     

沿黄河下游湖泊湿地植物群落演替及其多样性研究

沿黄河下游湖泊湿地是黄河健康生命系统的重要组成部分,其植物群落演替及其多样性研究对湿地及其生物多样性保护有重要意义。通过野外样地调查,分析了沿黄河下游湖泊湿地植物物种组成及其群落的演替模式,并计算了群落植物多样性特征指数,包括物种丰富度指数（S）、多样性Simpson指数（D）、Shannon-wiener指数（H′）、均匀度指数Pielou（E）。结果表明,研究区湖泊湿地共有77种植物,属于28科61属,除榆树Ulmus pumila Linn.为木本植物外,其余76种为草本植物,其中有1种轮藻门植物,1种蕨类植物;从空间来看植物群落演替过程为沉水植物菹草群落→纯水烛群落→水烛群落→水烛＋扁秆藨草群落→藨草群落→芦苇群落,青龙湖湿地水环境的变化,使湿地植物群落的类型也随之发生变化;群落多样性指数Shannon-wiener指数均低于1.12,Simpson指数为0.41~1,Pielou均匀度指数为0.8左右;芦苇群落的物种数最多,有32个物种,水烛群落以12种次之,菹草群落、水烛＋扁秆藨草群落和扁秆藨草群落中的物种数差别不大。沿黄河下游湿地植物群落多样性水平较低,湿地系统有向陆地系统过渡的趋势。     

复合人工湿地去除有机污染物的研究

人工湿地中不同的污染物的去除机理不同,其去污的影响因素也不同.在国内,人工湿地对氮磷去除的研究较多,对新型有机污染物的研究很少,在很多机理上还属空白.总结了近年来国内外湿地对有机污染物去除的研究进展情况以及不同湿地类型对去除率的影响.系统的分析了有关湿地植物,基质,微生物对于有机污染物的去除作用机理,提出了存在问题并对今后湿地去除有机污染物的研究进行了展望.     

崇明东滩湿地植被类型和沉积特征对土壤碳、氮分布的影响

滨海湿地碳、氮储量的分布可能受盐沼植被和外源沉积物的综合影响.本文以长江口典型滨海湿地为研究对象,分别在崇明东滩湿地北部、中部和南部设置3条样线,根据外源沉积物的区域特征研究了3种主要盐沼植被(芦苇(Phragmites australis)、互花米草(Spartina alterniflora)、海三棱藨草(Scirpus mariqueter))和土壤中的有机碳(TOC)、总氮(TN)的季节变化及空间特征.结果显示,崇明东滩湿地北、中部为淤积型滩涂,南部呈侵蚀态势.盐沼植被中芦苇和互花米草生物量TOC、TN累积量均显著高于海三棱藨草带.北、中样线的相同植被类型中的土壤TOC、TN显著高于南样线.高潮滩的芦苇带土壤TOC储量高于中潮滩的互花米草带,而互花米草带土壤TN储量略高于芦苇带,海三棱藨草带和光滩土壤TOC、TN储量最低.盐沼植被类型显著影响土壤各层次TOC和TN储量的分布,其中,0~10 cm层次储量受植被类型和表层外源沉积物空间特征的交互作用影响.     

铁岭市莲花湖湿地生态系统对城区污水中氮、磷的去除效果分析

铁岭市位于辽宁省北部,主城区人口约40万人,城区污水排放量约14万m2／d,由城市排水管网收集后入污水处理厂集中处理。城区污水处理厂出水首先排入莲花湖湿地,经湿地生态系统净化后入凡河Ⅳ类水域,最终入辽河V类水域。利用人工湿地净化铁岭城市污水,对治理辽河水流域污染具有重要意义。本文根据城市污水在莲花湖人工湿地的走向以及莲花湖人工湿地的单元构成,对湿地主要构建单元的水质进行监测,分析莲花湖人工湿地净化城市污水中氮、磷污染物的净化效果,探求城市生态环境可持续发展的新思路。     

Land Use and Climate Variability Amplify Carbon,Nutrient, and Contaminant Pulses: A Review with Management Implications

Nonpoint source pollution from agriculture and urbanization is increasing globally at the same time climate extremes have increased in frequency and intensity. We review >200 studies of hydrologic and gaseous fluxes and show how the interaction between land use and climate variability alters magnitude and frequency of carbon, nutrient, and greenhouse gas pulses in watersheds. Agricultural and urban watersheds respond similarly to climate variability due to headwater alteration and loss of ecosystem services to buffer runoff and temperature changes. Organic carbon concentrations/exports increase and organic carbon quality changes with runoff. Nitrogen and phosphorus exports increase during floods (sometimes by an order of magnitude) and decrease during droughts. Relationships between annual runoff and nitrogen and phosphorus exports differ across land use. CH₄ and N₂O pulses in riparian zones/floodplains predominantly increase with: flooding, warming, low oxygen, nutrient enrichment, and organic carbon. CH₄, N₂O, and CO₂ pulses in streams/rivers increase due to similar factors but effects of floods are less known compared to base flow/droughts. Emerging questions include: (1) What factors influence lag times of contaminant pulses in response to extreme events? (2) What drives resistance/resilience to hydrologic and gaseous pulses? We conclude with eight recommendations for managing watershed pulses in response to interactive effects of land use and climate change.     

Hydrobiogeochemical Controls on Riparian Nutrient and Greenhouse Gas Dynamics: 10 Years Post‐Restoration

Little is known about the impact of agricultural legacy on subsurface biogeochemical processes in the years following restoration of riparian wetlands (WLs). More knowledge is also needed on the relative importance of seasons, precipitation events, and inputs of water and nutrients driving nitrogen (N), phosphorus (P), sulfur (S), and greenhouse gas (GHG) (N₂O, CO₂, CH₄) dynamics in these systems. This investigation of a riparian zone comprising a restored WL area and a nonrestored well‐drained alluvium (AL) area in the United States Midwest revealed that despite successful hydrological restoration a decade earlier, biogeochemical conditions in the WL area remained less anoxic than in natural WLs, and not significantly different from those in the AL area. No significant differences in N, P, S, and C compound concentrations or fluxes were observed between the AL and WL areas. Over the duration of the study, nitrate (NO₃^?) and soluble reactive phosphorus appeared to be primarily driven by hillslope contributions. Ammonium (NH₄⁺), sulfate (SO₄^2?), and CO₂ responded strongly to seasonal changes in biogeochemical conditions in the riparian zone, while N₂O and CH₄ fluxes were most influenced by large rewetting events. Overall, our results challenge overly simplistic assumptions derived from direct interpretation of redox thermodynamics, and show complex patterns of solutes and GHGs at the riparian zone scale.     

洞庭湖湿地景观格局变化以及三峡工程蓄水对其影响

通过对近20 a遥感影像的解译分析,结果表明：洞庭湖湿地景观格局变化较为迅速,在几种湿地景观类型中,芦苇分布面积稳定增长,由475 km²增至751 km²,年均增加13.1 km²,湖草的分布面积比较稳定,而水面与泥滩的分布面积则大幅减少。湿地格局演变总体上呈现芦苇挤占湖草的分布空间、湖草挤占水面泥滩的态势。分析认为泥沙淤积和湖泊水情变化改变了洲滩的淹水历时,引起植被分布的变化,是影响洞庭湖湿地景观格局的主要因素。2000年后,随着泥沙淤积减缓,湖泊水情变化对湿地景观格局影响更为重要,其中三峡水库的运行使洞庭湖中、低位洲滩提前出露,淹水历时缩短,导致湖草的分布界线明显向下延伸     

CLIMATE CHANGE: POTENTIAL IMPACTS AND INTERACTIONS IN WETLANDS OF THE UNTTED STATES1

ABSTRACT: Wetlands exist in a transition zone between aquatic and terrestrial environments which can be altered by subtle changes in hydrology. Twentieth century climate records show that the United States is generally experiencing a trend towards a wetter, warmer climate; some climate models suggest that this trend will continue and possibly intensify over the next 100 years. Wetlands that are most likely to be affected by these and other potential changes (e.g., sea‐level rise) associated with atmospheric carbon enrichment include permafrost wetlands, coastal and estuanne wetlands, peat lands, alpine wetlands, and prairie pothole wetlands. Potential impacts range from changes in community structure to changes in ecological function, and from extirpation to enhancement. Wetlands (particularly boreal peat‐lands) play an important role in the global carbon cycle, generally sequestering carbon in the form of biomass, methane, dissolved organic material and organic sediment. Wetlands that are drained or partially dried can become a net source of methane and carbon dioxide to the atmosphere, serving as a positive biotic feedback to global warming. Policy options for minimizing the adverse impacts of climate change on wetland ecosystems include the reduction of current anthropogenic stresses, allowing for inland migration of coastal wetlands as sea‐level rises, active management to preserve wetland hydrology, and a wide range of other management and restoration options.     

复合垂直流人工湿地微生物特征对典型污水的响应差异

污水性质是影响人工湿地微生物特征的重要因子,而微生物对人工湿地污染物净化功能的发挥至关重要. 运用两组IVCW(复合垂直流人工湿地)分别处理模拟生活污水和污水处理厂尾水,比较研究两组系统下行流、上行流池的基质酶活性及硝化反硝化强度,并通过脂肪酸甲酯图谱分析系统中的微生物群落结构,以解析人工湿地微生物特征对两种污水的响应差异. 结果表明:处理生活污水的IVCW下行流池中脱氢酶、过氧化氢酶、脲酶及硝酸盐还原酶活性均显著高于其他单元,四者平均值分别为其他单元的2.8~4.6、7.9~10.3、19.3~41.7和4.5~10.8倍. 处理生活污水IVCW基质的硝化强度是尾水处理系统对应单元的1.4~5.3倍(下行流)和1.3~3.9倍(上行流),而两组IVCW对应单元基质的反硝化强度之间无显著差异. IVCW下行流池中特征脂肪酸比值及微生物群落结构受污水类型的影响较小,均以厌氧细菌和革兰氏阳性菌为优势菌;上行流池微生物群落结构则受到污水类型的一定影响,真菌的相对丰度较高. 两种污水对IVCW基质酶活性和硝化强度的影响高于对反硝化强度和微生物群落结构的影响.