Methane levels in shallow subtropical lake sediments: Dependence on the trophic status of the lake and allochthonous input

The vertical sediment profiles (10 cm) of the margins of three shallow subtropical lakes (Rio Grande, Brazil) with different trophic states and surrounding areas were evaluated to identify the effects of the allochthonous input on the methane concentration in the sediment. Sediment cores were collected to quantify the organic matter content (OM) and total carbon (TC), total nitrogen (TN), total phosphorous (TP) and methane (CH₄) concentrations.The three lakes were distinguished according to the trophic status and classified as oligotrophic, dystrophic and eutrophic. The natural characteristics of the dystrophic and eutrophic lakes have been changed due to the allochthonous input of leaves and twigs (Eucalyptus sp.) and the excreta of birds, respectively. In the eutrophic lake, the allochthonous input contributed to high autochthonous production. The highest values of OM, TC, TN and TP were found in the superficial sediments of the dystrophic and eutrophic lakes. The accumulation of allochthonous organic matter in the littoral zone promoted changes in the vertical sediment profiles and contributed to increases in the CH₄ concentrations in the sediment.     

Organic diagenesis in sediment and its impact on the adsorption of bisphenol A and nonylphenol onto marine sediment

Hydrophobic organic contaminants in marine water are mostly adsorbed onto (partitioned into) sediment organic matter (SOM). To study the impact of SOM diagenesis on sediment adsorption properties, artificial sediment with rich SOM content was incubated for more than 120 days. The sediment was sampled every week, and batch sediment adsorption tests were conducted with bisphenol A (BPA) and nonylphenol (NP) as the model pollutants. The results show that the amount of organic matter loaded in the sediment decreased by nearly 80% during incubation. For the incubated sediment, the BPA partition coefficient, K_d, decreased whereas the organic normalized partition coefficient, K_oc, more than doubled. The experiments with NP show an even greater increase in K_oc. Organic matter diagenesis shows a profound effect on the adsorption behavior of sediment, as the SOM residue has an increasing affinity and partition capacity for organic contaminants.     

A new concept to forecast the process of suspended sediment accumulation in the bottom sediment of small reservoirs

The new concept presented for forecasting the rate of accumulation of suspended sediment in reservoir water in the bottom sediment allows reasonable estimates of the siltation process globally, regionally, or locally, to be obtained without the need for costly research. The method draws on three key parameters, i.e., the concentration of suspended sediments (SS), and its organic matter (OM_SS) content, as well as the storage capacity (V_R) (i.e., the water storage in the reservoir). All of these parameters easy to determine, with information on them, in fact, made widely available by most agencies managing reservoirs in different parts of the world. In practice, the proposed method can represent a missing link in the precise determination of a reservoirs rate of siltation (and hence, losses of storage capacity).     

Influence of macroinvertebrates on physico‐chemical and microbial processes in hyporheic sediments

The objective of this study was to measure the effects of invertebrates on the physical characteristics and microbial processes in hyporheic sediments. We investigated the impacts of an assemblage of three taxa (asellids, chironomid larvae, and tubificid worms) on sediment distribution, water fluxes, sediment organic carbon, biofilm (attached bacteria) characteristics, and O₂, dissolved organic carbon NO₃^?, NO₂^?, and NH₄⁺ concentrations in slow filtration sand–gravel columns. The results showed that invertebrates clearly modified the distribution of particles in the sediment column, probably because of the structures (tubes, macropores, and faecal pellets) produced by the three taxa in the sediment. Our assessment of water fluxes indicated that invertebrate activities led to an increase in the porosity of the sediment columns. In addition, aerobic (O₂ consumption) and anaerobic (denitrification and fermentative decomposition of organic matter) microbial processes occurring in the sediment were stimulated in the presence of invertebrates. Finally, the present study demonstrates that invertebrates can act as ecosystem engineers in heterogeneous sediments that are under the influence of an advective flux of water. The solute residence time increased in columns containing the faunal assemblage. Micro‐organisms used more dissolved organic matter and nutrients in the presence of invertebrates because invertebrate activities increased the contact between the biofilm and water. We conclude that engineering by invertebrates in natural conditions modifies characteristics of the hyporheic zone and thereby enhances both the porosity of the sediment and the solute transport across the benthic interface. Copyright © 2002 John Wiley & Sons, Ltd.     

Einsatz von Pflanzenkläranlagen zur Behandlung von schadstoffbelastetem Oberflächenabfluß städtischer Straßen

A combination of retention pond and reed bed was tested for its effectiveness in reducing non-point source runoff pollution from an urban area. This paper presents data on the development of reed plants (Phragmites australis Cav. Trin.), on the effectiveness of runoff purification and on the accumulation of contaminants in the pond sediment and the reed bed for the years 1993–1995. P. australis was well established and grew according to normal development. The measured length and biomass values of P. australis were larger on sand than on gravel and coarse materials. Toxic levels of heavy metals in the plants were not reached. Harvested plants can be composted. The purification system is effective within the following ranges: The rate of retention of suspended solids and heavy metals varies between 16% and 91%. For chemical oxygen demand the average values is 25%. Poor retention rates usually occur along with very low input concentrations. Generally retention within the reed bed is higher than in the pond. Between 1993 and 1995 the concentration of contaminants within the organic layer of the reed bed increased by 50% for lead and by 90% for poly aromatic hydrocarbons. Until 1994 the concentrations of mineral oil hydrocarbons also increased by 60%. Between 1994 and 1995 however the concentration of mineral oil hydrocarbons in the reed bed decreased rapidly by more than 50%: Mineral oil hydrocarbons underlie biological degradation within the reed bed. In the pond sediment a significant accumulation of heavy metals, poly aromatic hydrocarbons and mineral oil hydrocarbons has also been found. The concentrations of these contaminants are still far from inhibiting the function of the system.     

Physical, chemical and microbiological characterization of the intertidal sediments of Pereque Beach, Guarujá (SP), Brazil

Physical and chemical characteristics of intertidal sediments and their relationships with bacteria and cyanobacteria were analyzed at four stations at Pereque Beach. Granulometric analysis showed that Pereque beach has sediment that is classified as sand. The lowest value of the sediment C/N rates (6.08), mainly due to a higher concentration of organic nitrogen, was found at the northern part of Pereque Beach, where organic matter of marine source was more prominent. In this area, density (9.6x10(6)cells cm(-3)), biomass (1992.04ngC cm(-3)) and activity of bacteria were higher than at the southern end. In contrast, cyanobacteria density varied from 2.0 to 4.0x10(5)cells cm(-3), with biomass and total chlorophyll a of the sediment being higher at the southern part, where there are water input from Pereque River and higher organic matter of continental origin. The variability in the microbial population is discussed in the light of the sediment granulometry, organic matter quality, fresh water inflow and pollution.     

鲂胚胎的发育

太湖湖区暴雨径流携带有大量的泥沙和土壤有机物质,对河湖水质造成污染,为了定量分析有机污染对太湖水体的影响,分水田和旱地两种土地利用条件,采用数学模型模拟了湖区丰。平,枯典型年的产流,土壤侵蚀和有机物流失过程及年总量。结果表明,湖区土壤侵蚀量和有机物流失量随地表排水强度的增加呈指数形式增大,尤其是每年暴雨期,湖区地表排水中有机物含量显著增大,建议在太湖流域水质规划和治理中加以重视并采取必要防治措施。     

氧化还原条件对红枫湖沉积物磷释放影响的微尺度分析

选取贵州红枫湖为研究对象,在实验室条件下模拟了自然、好氧和厌氧条件下沉积物内源磷的释放过程,联合应用微电极技术和沉积物磷形态分析对沉积物—水界面开展了微尺度观测与研究.结果表明,厌氧条件下红枫湖沉积物总磷含量显著降低,且主要是NaOH提取态磷(NaOH-P)和残渣态磷(rest-P)含量降低所致,厌氧条件下沉积物孔隙水中磷酸盐浓度明显升高,而好氧条件下沉积物孔隙水磷酸盐浓度显著降低,反映厌氧条件显著促进了红枫湖沉积物磷释放.厌氧条件下沉积物内部溶解氧浓度下降、硫还原活动增强可能是导致NaOH-P释放的主要原因.O_2浓度的降低加速了沉积物还原作用并产生大量H2S,进而与二价铁离子形成硫化亚铁沉淀,最终导致NaOH-P(Fe-P)释放到孔隙水中.好氧条件向厌氧条件的转换可通过改变沉积物内部pH值分布和微生物活动促使rest-P释放:厌氧条件下,厌氧微生物不仅可以消耗硫酸根产生H_2S,导致pH值降低,还可消耗有机质,将有机磷转变为无机磷.上述研究结果表明,沉积物—水界面氧化还原环境可影响沉积物氧渗透深度、pH值分布、微生物活动、硫循环以及有机质降解过程,进而控制沉积物磷的形态转化与释放.联合应用微电极技术和沉积物磷形态分析对湖泊沉积物—水界面开展微尺度观测研究是揭示沉积物内源磷释放机制与控制因素的有效途径.     

Radiocarbon and 230Th data reveal rapid redistribution and temporal changes in sediment focussing at a North Atlantic drift

In locations of rapid sediment accumulation receiving substantial amounts of laterally transported material the timescales of transport and accurate quantification of the transported material are at the focus of intense research. Here we present radiocarbon data obtained on co-occurring planktic foraminifera, marine haptophyte biomarkers (alkenones) and total organic carbon (TOC) coupled with excess Thorium-230 (²³⁰Th_xs) measurements on four sediment cores retrieved in 1649–2879 m water depth from two such high accumulation drift deposits in the Northeast Atlantic, Björn and Gardar Drifts. While ²³⁰Th_xs inventories imply strong sediment focussing, no age offsets are observed between planktic foraminifera and alkenones, suggesting that redistribution of sediments is rapid and occurs soon after formation of marine organic matter, or that transported material contains negligible amounts of alkenones. An isotopic mass balance calculation based on radiocarbon concentrations of co-occurring sediment components leads us to estimate that transported sediment components contain up to 12% of fossil organic matter that is free of or very poor in alkenones, but nevertheless appears to consist of a mixture of fresh and eroded fossil material. Considering all available constraints to characterize transported material, our results show that although focussing factors calculated from bulk sediment ²³⁰Th_xs inventories may allow useful approximations of bulk redeposition, they do not provide a unique estimate of the amount of each laterally transported sediment component. Furthermore, our findings provide evidence that the occurrence of lateral sediment redistribution alone does not always hinder the use of multiple proxies but that individual sediment fractions are affected to variable extents by sediment focussing.     

Organic diagenesis in sediment and its impact on the adsorption of bisphenol A and nonylphenol onto marine sediment

Hydrophobic organic contaminants in marine water are mostly adsorbed onto (partitioned into) sediment organic matter (SOM). To study the impact of SOM diagenesis on sediment adsorption properties, artificial sediment with rich SOM content was incubated for more than 120 days. The sediment was sampled every week, and batch sediment adsorption tests were conducted with bisphenol A (BPA) and nonylphenol (NP) as the model pollutants. The results show that the amount of organic matter loaded in the sediment decreased by nearly 80% during incubation. For the incubated sediment, the BPA partition coefficient, Kd, decreased whereas the organic normalized partition coefficient, Koc, more than doubled. The experiments with NP show an even greater increase in Koc. Organic matter diagenesis shows a profound effect on the adsorption behavior of sediment, as the SOM residue has an increasing affinity and partition capacity for organic contaminants.     

Hydrochemical Characteristic of the Littoral Zone of Lake Onega

The article presents the results of hydrochemical studies of two areas, open and closed, in the littoral zone of Lake Onega, carried out in 2013–2014. The results show that water of river and slope runoff, enriched with both biogenic elements and allochthonous organic matter, persist over a long time in spring in the littoral zone. In the summer, water chemistry at open shores is similar to that in lake pelagic zone, while the closed areas of littoral zone show the effect of biological processes. In the period of autumn homothermy, river and slope waters have no considerable effect on coastal water quality.     

Comparison of production and degradation of organic matter at a littoral site of the prealpine Lake Constance

Biotic structures and processes of the comparatively large and deep Lake Constance are dominated by pelagic water bodies. Therefore, much more attention has thus far been paid to the carbon cycle of pelagic habitats as compared to littoral areas. Nevertheless, there is also an ongoing debate on the importance of littoral areas for the carbon cycle in this lake. Although actually existing data are certainly insufficient for a realistic carbon budget, investigations made during the past decade provide at least a rough basis for a first evaluation. Accordingly, littoral areas appear to contribute overproportionally (related to surface) both to production as well as to degradation of organic carbon in the lake. However, the relative effect seems to be more pronounced for heterotrophic activities, mostly due to intense degradation processes in littoral sediments. Related to volume, littoral water bodies exhibited similar or slightly higher microbial activities as compared to epilimnetic pelagic water bodies, while microbial abundances and activities observed for littoral sediments exceeded the corresponding overlying water layers by one to three orders of magnitude. As was confirmed by in situ measurements microbial oxygen consumption frequently exceeded photosynthetic oxygen production in the investigated littoral sites. Moreover, significant qualitative differences between water and sediment were found for the degradation potentials of xenobiotics as was exemplified for phenol and nitrilo-triacetic acid (NTA). Overall, a buffer function at the landwater interface may be ascribed to littoral areas due to which the large pelagic water bodies of the lake may become additionally protected against loads of undesired organic substances due to high littoral degradation capacities.     

Dependence of eelgrass (Zostera marina) light requirements on sediment organic matter in Massachusetts coastal bays: Implications for remediation and restoration

Using a calibrated bio-optical model we determined that the optical water quality conditions in several nitrogen-impaired embayments and in one unimpaired system were within the range of values known to support eelgrass growth. We also used the model to identify a range of light requirements for eelgrass (Zostera marina). Higher eelgrass light requirements, expressed as a percentage of surface-incident irradiance, corresponded with higher sediment organic matter content. These results corroborated findings by previous studies which indicate a generalized relationship: seagrasses growing in turbid conditions with poorer water and sediment quality have higher light requirements than those growing in less degraded conditions. The mechanistic reason for the variation in light requirements is still not completely explained and cannot be attributed to a single independent variable. Varying light requirement have important implications for eelgrass protection and should be considered when setting restoration targets for eelgrass in water quality and nitrogen remediation programs.     

Role of Methane Cycling in Organic Matter Turnover in Different Types of Lakes

The rates of microbiological processes in CH₄ cycling and organic matter destruction in the bottom sediment and water of different types of lakes in the Upper Volga basin and Baltic countries are determined. The rates of CH₄ removal from silts and the peculiarities of its distribution in water mass as a function of the lake productivity and the character of water mixing in it are studied. The role of processes in CH₄ cycling in destruction is shown to increase with increasing lake productivity.     

Denitrification in a Laurentian Great Lakes coastal wetland invaded by hybrid cattail (Typha × glauca)

Wetland ecosystems maintain and improve water quality through the process of denitrification, an increasingly important ecosystem service due to global N pollution. Invasive plants have the potential to disrupt denitrification by altering the environmental conditions that facilitate this process. Great Lakes coastal wetlands are experiencing widespread invasion by highly productive hybrid cattail with largely uncertain biogeochemical effects. Through field and controlled mesocosm studies, we sought to determine the effects of cattail invasion through time on denitrification rates and associated environmental factors in a Great Lakes coastal wetland. In the field, we found that cattail density correlated with increased denitrification and a suite of environmental and plant community characteristics and denitrification rates were positively correlated with NH₄ ⁺, sediment organic matter, reduced water levels, and cattail stand age. Through our controlled mesocosm study, we documented conditions 1- and 5-year following invasion and found that denitrification rates and soil organic matter increased in year 5, and cattail and year-since-invasion altered plant communities and soil NH₄ ⁺. Only a weak correlation between denitrification rates and cattail treatments was noted, however, owing to high replicate variability. Our results indicate that with increasing cattail residence time, one ecosystem service, biodiversity, was negatively impacted, while two other services, denitrification and sediment carbon accumulation, were enhanced. Thus, this highly invaded wetland still provides valuable services to aquatic ecosystems and to society. A holistic perspective is therefore critical when evaluating invasive species impacts in which negative impacts are weighed against other ecosystem services, which may be stimulated.     

Human‐induced sedimentation patterns of a channelized lowland river

Channelization of the severely polluted Odra and Vistula Rivers in Poland induced intensive accumulation of fine‐grained deposits rich in organic matter and heavy metals. These sediments have been identified in vertical profiles in a narrow zone along river banks both in groyne‐created basins and on the floodplain. Grain size, organic matter, zinc (Zn), lead (Pb), copper (Cu) content and cesium‐137 (¹³⁷Cs) was used for sediment dating and, stratigraphy and chemistry have been diagnostic features for these deposits, named industrial alluvium. In the most polluted river reaches stabilized by bank reinforcements and groynes, 2‐m‐thick slack water groyne deposits are composed of uniform strata of polluted silts with organic matter content over 10%, Zn content over 1000 mg/kg and average Cu and Pb over 100 mg/kg. The average rate of sediment accretion in groynes is higher than on the floodplain and reaches 5 cm/yr. Stratification which appears at higher levels in the groyne fields and on the levees reflects a change from in‐channel to overbank deposition and is typified by dark layers separated by bright, sandy, and less polluted strata. Stratified, 4‐m‐thick, sediment sequences have been found in groyne fields of incised river reaches. The average rate of sediment accretion in these reaches is of the order of 5 cm/yr. In stable and relatively less polluted river reaches, vertical‐accretion organic deposits are finely laminated and the average rate of deposition amounts to a few millimeters per year. Investigations indicate that groyne construction favors conditions for long‐term storage of sediments at channel banks. For this reason, groynes should be considered as structures that efficiently limit sudden release of sediment‐associated heavy metals stored in channels and in floodplains of the historically polluted rivers. Copyright © 2014 John Wiley & Sons, Ltd.     

太湖湖区有机物流失模拟

研究了１９９２－１９９４年女山湖大面积围栏养蟹利用与保护沉水植物资源的效果结果表明：围栏内河蟹的食物组成中,主要有菹草、苦草、金鱼藻、马来眼子菜、黄丝草和黑藻等沉水植物．其中菹草、黑藻的出现频率和概念生物量,分别在４、６、７、８和９月为最高;围栏内沉水植物的种类和生物量的变化与河蟹的放养密度关系密切,当河蟹的放养密度不超过３０只·ｈｍ~（－２）时,围栏内沉水植物的生物量与对照组均有明显的增加趋势,由此可证,女山湖大面积的围栏养蟹和适宜的放养密度,有效地利用和保护了围栏区内的沉水植物资源     

富营养化湖泊蓝藻-芦苇碎屑堆积分解过程及其潜在的共代谢效应

为探究富营养化浅水湖泊所富集的有机物对湖泊碳循环和水质的影响,本研究构建微宇宙系统,模拟蓝藻和芦苇碎屑单独分解及混合分解过程.通过测定各组上覆水营养盐浓度、有机质含量及结构的变化,揭示富营养化湖泊藻草残体混合分解过程中养分和有机碳的释放特征.结果表明,在实验0～88 h内,在添加相同的碳源条件下,蓝藻和芦苇混合处理组总碳(TC)释放量显著高于理论值,表明藻草碎屑混合分解存在共代谢效应.在培养初期,沉积物通过共代谢效应对水质产生了较大的影响,加速向水体中释放氮、磷物质.相较单独的植物分解,混合处理组中总氮(TN)、总磷(TP)的最大释放量分别提高了13.49%和26.84%;通过三维荧光光谱表征的类富里酸荧光强度变化也表明:较芦苇处理组,混合处理组中芦苇的分解速率更快.在培养开始后,各处理组均快速转变为厌氧状态,TC、TN、TP浓度随时间变化总体上呈先快速上升再逐渐平缓的趋势,分别在第228、108和324小时达最大值(372.4±2.98)、(138.45±2.97)和(7.95±1.11) mg/L.细菌特异性脂肪酸含量变化表明,将蓝藻碎屑添加到芦苇碎屑中,会增加芦苇碎屑中细菌的丰度,从而提高分解速率,激发共代谢效应.在全球气候变暖的背景下,随着富营养化湖泊藻类暴发频次增加,共代谢效应可能还会进一步加强,对富营养化湖泊水质将会持续产生影响.     

Environmental determinants of littoral paludification in boreal lakes

Numerical studies of the relationships between littoral processes and environmental variables are important because they provide understanding of the impacts of natural and human factors on lake systems. In this study, littoral paludification, its occurrence, types and main environmental determinants were studied in boreal lakes with varying size (41–560 km²) and total phosphorus content (4.5–35.5 μg L⁻¹) in Finland. The relative importance of catchment characteristics, water quality and water level regulation on paludification was analysed at the lake level (n=20), whereas the importance of site morphology, soil quality and aquatic vegetation was analysed at the site level (n=289). This study utilised two novel statistical methods in numerical analyses: generalised linear mixed models and variation partitioning (VP). Bottom ward overgrowth was the main paludification type in the studied lakes. At the lake level, the magnitude of spring flooding and the altitude of the lake had a negative response to paludification, whereas the existence of water level regulation, cover of clay soil and total phosphorus content correlated positively to paludification. At the site level, the paludification was negatively related to slope angle, and positively to the occurrence of clay soil, Glyceria maxima (reed sweet-grass) and the abundance of eutrophy indicator species. However, a considerable amount of variation in littoral paludification both at lake and site levels was accounted for by the joint effects of predictors and may thus be causally related to two or all three groups of predictors.     

Laboratory analyses of nutrient release processes from Haihe River sediment

Sediment samples were collected from the heavily contaminated Haihe River to conduct static nutrient release experiments with tap water,and to evaluate the effect of dredging depths,salinity and light ...