重污染感潮河道底泥释放特征及其控制技术研究

以珠江三角洲城市重污染感潮河道为对象,研究了底泥污染物(重金属、有机物和营养盐)在静态、潮汐作用影响及人工曝气扰动下的释放特征.在此基础上,采用曝气充氧、重金属化学固定、激活底泥土著微生物等联合技术对底泥释放进行控制,研究其控制效果.结果表明:①感潮作用加速了底泥污染物的释放,与静态释放相比,Cu、Zn、Pb、Cr、COD、NH 4-N和TP的平均释放速率提高了1～4倍,释放量增加了0.3～1.8倍;底泥平均耗氧速率提高了1.28倍.②人工曝气扰动使底泥污染物局部急剧释放,并使泥水界面由弱碱性变成弱酸性;在有氧环境,NH 4-N、TP的释放得到有效抑制.③投加石灰调节pH至8～9,上覆水体Cu、Zn、Pb、Cr的去除率达到85%～98%,同时还可去除92%的TP和86%的浊度;在微碱性好氧条件下,Cu、Zn、Pb和Cr的释放量稳定在300μg·L-1以下.④底泥土著微生物层对水体及底泥污染物有良好的降解作用,通过间歇曝气COD、NH 4-N、TP去除率分别可达到85%、92%和71%;但微生物层具有较高的耗氧速率,达到45g·m-2·d-1.     

北黄海北部海域潮余流的模拟研究

基于二维水动力模型,在仅考虑潮流作用条件下,通过计算欧拉余流和拉格朗日余流并结合粒子追踪方法研究了辽宁大连—朝鲜龙渊郡连线北侧的北黄海北部海域的潮余流结构和粒子运移的趋势。结果表明:欧拉余流和拉格朗日余流流速整体较小,呈现由南向北的流向,但在獐子岛及长山群岛的附近岛屿和朝鲜半岛沿岸的海域欧拉余流和拉格朗日余流流速较大。对比粒子追踪计算的结果与欧拉余流和拉格朗日余流的结果表明,流向与粒子运移路径基本一致。该海湾的余流及粒子运动规律特点对辽东半岛东岸及朝鲜半岛西侧海域的排污及污染控制有重要的借鉴意义。     

黄河口典型潮沟土壤碳氮分布特征规律

为探究黄河三角洲盐沼土壤碳氮含量在潮沟水系中的时空分布特征,选取黄河口一条典型的潮沟系统,采集一、二、三级潮沟表层土壤,探寻土壤有机碳、总氮与土壤容重、盐度、pH等理化因子的相关关系。结果表明：土壤有机碳和总氮在时空尺度上表现出极大的异质性特征。时间尺度上,土壤有机碳和总氮出现先上升后下降的趋势。空间尺度上,一级潮沟土壤有机碳和总氮平均值（2.9 g·kg^-1、0.36 g·kg^-1）大于二级（1.4 g·kg^-1、0.18 g·kg^-1）、三级（1.6 g·kg^-1、0.21 g·kg^-1）潮沟。相关分析表明,土壤有机碳和总氮与盐度呈显著正相关（P<0.01）,与容重呈显著负相关（P<0.01）。盐沼湿地土壤碳氮含量受土壤水盐条件的影响,而潮沟水系的树状结构对水盐条件的影响是导致土壤碳氮含量时空差异分布的重要因素。     

闽江河口短叶茳芏湿地及其围垦的养虾塘CH4排放通量的比较

以闽江河口鳝鱼滩的短叶茳芏湿地及由其围垦而成的养虾塘为研究对象,2016年5月—2017年3月,分别采用静态箱-气相色谱法和悬浮箱/静态箱-气相色谱法对短叶茳芏湿地和养虾塘白天CH_4排放通量进行观测,并同步测定短叶茳芏湿地和养虾塘水体/沉积物理化指标.观测期间短叶茳芏湿地和养虾塘均表现为大气中CH_4的排放源,释放量变化范围分别为1.09~38.38 mg·m~(-2)·h~(-1)和0.01~65.38 mg·m~(-2)·h~(-1),均值分别为(11.67±1.99)mg·m~(-2)·h~(-1)和(18.69±4.84)mg·m~(-2)·h~(-1),重复测量方差分析统计结果表明:虽然在整个观测时间尺度上,养虾塘CH_4排放通量与短叶茳芏湿地无显著性差异(p0.05),但是在养殖期养虾塘CH_4排放通量显著高于同期短叶茳芏湿地(p0.05),增加了68.0%.短叶茳芏湿地CH_4排放通量与沉积物温度、间隙水总磷含量呈显著正相关关系(p0.01),养虾塘水-气界面CH_4排放通量与养殖水水深呈显著负相关关系(p0.01).亚热带河口感潮沼泽湿地围垦成为陆基养虾塘后增加了CH_4排放通量.     

排水速率对潮汐流人工湿地中CANON作用的强化

为强化潮汐流人工湿地（TFCW）中基于亚硝化的全程自养脱氮（CANON）作用,探究了不同排水速率（v_d）下系统中氮素的迁移转化机制与微生物特征.结果表明,v_d可显著影响TFCW中脱氮功能微生物的数量与活性,进而影响其氮素转化速率.当v_d由1.00降至0.50L/min时,填料层中逐渐形成较为严格的限氧环境,有利于短程硝化的稳定和厌氧氨氧化菌的富集,进而有助于CANON反应体系在TFCW中形成.而当v_d小于0.50L/min时,填料层中溶解氧相对不足,好氧氨氧化菌活性受到抑制,数量随之减少,CANON作用的强化效果有限,系统脱氮性能受到影响.当v_d为0.50L/min时,TFCW中的CANON作用可得到最大限度的强化,系统脱氮性能达到最佳,其TN和NH₄⁺-N的去除负荷分别为（116.79±13.16）和（102.75±4.35） mg/（L·d）.对v_d的合理设置可实现TFCW中CANON作用的强化,有利于CANON型人工湿地的构建.     

氮、硫输入对河口湿地土壤有机碳矿化的实验研究

通过室内培养实验,研究了氮、硫输入对闽江河口湿地土壤有机碳矿化和土壤理化性质的影响.结果表明:NH_4Cl(N1)、NH_4NO_3(N3)、K_2SO_4(S)和NH_4Cl+K_2SO_4(NS1)处理显著促进了湿地土壤有机碳矿化速率(p0.05),较对照分别提高了76.57%、60.09%、83.20%和52.59%,并且不同处理下土壤有机碳矿化速率均表现为随培养时间的增加而递减.氮、硫输入在不同时间对湿地土壤有机碳矿化的影响不尽一致,在前6 d各处理的促进作用最明显.湿地土壤有机碳累积矿化量在不同处理下均表现为随培养时间逐渐增加,其增长速率在培养初始阶段较快,而后逐渐减慢;不同培养时间有机碳累积矿化量在N1、N3、S和NS1处理下与对照处理间均存在显著差异(p0.05).短期培养结束后,N3、NS1处理显著增加了湿地土壤DOC含量(p0.05);N1、N3、NS1和NH_4NO_3+K_2SO_4(NS3)处理均显著增加了土壤NH_4~+-N含量(p0.05);KNO_3(N2)、N3、NS2和NS3处理均显著增加了土壤NO_3~--N含量(p0.05);S、NS1、NS2和NS3处理均显著增加了土壤SO_4~(2-)含量(p0.05).不同处理下湿地土壤Cl-、pH、EC具有微弱的波动变化特征,但在不同处理组间均不存在显著差异(p0.05).多元回归分析显示,DOC、NH_4~+-N和SO_4~(2-)是氮、硫输入处理下影响闽江河口湿地土壤有机碳矿化速率的主要控制因素.     

Role of Crab Herbivory in Die-Off of New England Salt Marshes

Abstract:  Die-offs of cordgrass are pervasive throughout western Atlantic salt marshes, yet understanding of the mechanisms precipitating these events is limited. We tested whether herbivory by the native crab , Sesarma reticulatum , is generating die-offs of cordgrass that are currently occurring on Cape Cod, Massachusetts (U.S.A.), by manipulating crab access to cordgrass transplanted into die-off areas and healthy vegetation. We surveyed 12 Cape Cod marshes to investigate whether the extent of cordgrass die-off on creek banks, where die-offs are concentrated, was related to local Sesarma grazing intensity and crab density. We then used archived aerial images to examine whether creek bank die-off areas have expanded over the past 2 decades and tested the hypothesis that release from predation, leading to elevated Sesarma densities, is triggering cordgrass die-offs by tethering crabs where die-offs are pervasive and where die-offs have not yet been reported. Intensity of crab grazing on transplanted cordgrass was an order of magnitude higher in die-off areas than in adjacent vegetation. Surveys revealed that Sesarma herbivory has denuded nearly half the creek banks in Cape Cod marshes, and differences in crab-grazing intensity among marshes explained >80% of variation in the extent of the die-offs. Moreover, the rate of die-off expansion and area of marsh affected have more than doubled since 2000. Crab-tethering experiments suggest that release from predation has triggered elevated crab densities that are driving these die-offs, indicating that disruption of predator–prey interactions may be generating the collapse of marsh ecosystems previously thought to be exclusively under bottom-up control .     

Predictors of specialist avifaunal decline in coastal marshes

Coastal marshes are one of the world's most productive ecosystems. Consequently, they have been heavily used by humans for centuries, resulting in ecosystem loss. Direct human modifications such as road crossings and ditches and climatic stressors such as sea‐level rise and extreme storm events have the potential to further degrade the quantity and quality of marsh along coastlines. We used an 18‐year marsh‐bird database to generate population trends for 5 avian species (Rallus crepitans, Tringa semipalmata semipalmata, Ammodramus nelsonii subvirgatus, Ammodramus caudacutus, and Ammodramus maritimus) that breed almost exclusively in tidal marshes, and are potentially vulnerable to marsh degradation and loss as a result of anthropogenic change. We generated community and species trends across 3 spatial scales and explored possible drivers of the changes we observed, including marsh ditching, tidal restriction through road crossings, local rates of sea‐level rise, and potential for extreme flooding events. The specialist community showed negative trends in tidally restricted marshes (?2.4% annually from 1998 to 2012) but was stable in unrestricted marshes across the same period. At the species level, we found negative population trends in 3 of the 5 specialist species, ranging from ?4.2% to 9.0% annually. We suggest that tidal restriction may accelerate degradation of tidal marsh resilience to sea‐level rise by limiting sediment supply necessary for marsh accretion, resulting in specialist habitat loss in tidally restricted marshes. Based on our findings, we predict a collapse of the global population of Saltmarsh Sparrows (A. caudacutus) within the next 50 years and suggest that immediate conservation action is needed to prevent extinction of this species. We also suggest mitigation actions to restore sediment supply to coastal marshes to help sustain this ecosystem into the future.     

黄河三角洲翅碱篷湿地硫化氢和羰基硫排放动态研究

利用静态箱/气相色谱法,观测了生长季(5~10月)黄河三角洲翅碱篷湿地H2S和COS的释放动态.结果表明,H2S、COS的排放通量具有明显的季节和日变化规律,在生长季,黄河三角洲翅碱篷湿地是H2S和COS的释放源,其中H2S的平均释放通量为4.97μg·(m2·h)-1,COS的平均释放通量为0.92μg·(m2·h)-1.在探讨的环境因子中,不同环境因子对翅碱篷湿地H2S和COS释放通量的影响不同,其中土壤SO2-4含量是影响H2S释放通量的主要因素,土壤含水量是影响COS释放通量的主要因素.含硫气体的排放可能还受到其它因素如植物、潮汐状况等多种因素的影响.     

闽江河口短叶茳芏沼泽湿地沉积物磷的赋存形态和空间分布

对闽江河口区不同盐度短叶茳芏沼泽湿地沉积物中磷的赋存形态和分布特征进行了研究,探讨了河口沉积物中磷的来源及其影响因子.结果表明:1闽江河口湿地沉积物全磷(TP)含量介于607.91~807.60 mg·kg-1,平均值为726.29 mg·kg-1;有机磷(OP)含量介于120.44~166.63 mg·kg-1,平均值为139.43 mg·kg-1,约占TP的18.93%;无机磷(IP)含量介于479.65~647.56 mg·kg-1,平均值为586.86 mg·kg-1,约占TP的81.07%,IP是磷的主要赋存形态.2IP中,赋存形态以闭蓄态磷(O-P)和铁结合态磷(Fe-P)为主,分别占IP的39.97%和32.92%;其次是钙结合态磷(Ca-P)和铝结合态磷(Al-P),分别占IP的17.89%、9.22%.3在空间分布上,TP、OP、IP含量在由海向陆方向整体呈先降低后递增趋势;IP不同赋存形态在空间上也整体上呈现出以上趋势;垂直方向上,总体都表现为随土层深度波动降低,这在一定程度上反映了近年来河口湿地环境污染的加剧.4磷的赋存形态和空间分布特征是电导率、pH、容重、含水率和粒度等多因子综合作用的结果.