Sulphate reduction as a geomorphological agent in tidal marshes (‘Great Marshes’ at Barnstable,Cape Cod,USA)

Many tidal marsh surfaces feature water-filled depressions, known as salt pans (shallow) or ponds (deeper). In the Great Marshes at Barnstable, Cape Cod, pond formation is an active process. We hypothesize that degradation of organic matter by sulphate-reducing bacteria in these peat-rich marsh deposits is the primary cause of pan and pond formation. Sulphate reduction below an actively developing pond is probably enhanced by higher temperature and salinity of the pond water. Computer simulation suggests that ponds with similar characteristics to those in the Barnstable marshes may develop by sulphate reduction. Necessary conditions are sufficiently deep percolation and diffusion of sulphate into the underlying marsh deposits, and a high decomposition rate stimulated by high water temperatures in the ponds. In areas with a high density of ponds, drainage of the ponds by headward erosion of tidal creeks may cause rapid disintegration of the marsh surface. © 1998 John Wiley & Sons, Ltd.     

Long‐term carbon storage and hydrological control of CO2 exchange in tundra ponds in the Hudson Bay Lowland

Carbon dioxide fluxes and water balance were examined in 43 tundra ponds in the northern portion of the Hudson Bay Lowland near Churchill, Manitoba. Most of the ponds were hydrologically disconnected from their catchments during dry periods throughout the post‐melt season. However, episodic reconnection occurred following large precipitation events where depression storage was exceeded. Significant shifts in pond chemistry were observed following precipitation events, with the degree of CO₂ saturation increasing during these periods. Pond CO₂ concentrations rapidly fell to pre‐event levels following events, suggesting that hydrological connectivity can affect the magnitude and direction of CO₂ gas fluxes in tundra ponds. Atmospheric CO₂ invaded ponds with highly organic sediments for most of the summer, suggesting that terrestrially derived inorganic carbon was insufficient to meet the demands of algal net production. In contrast, ponds with highly mineral sediments continued to evade CO₂ during the summer. In a subset of 11 ponds, long‐term rates of carbon accumulation in sediment ranged from 0·6 to 2·2 mol C m^?2 year^?1. Very strong correlations existed between average sediment accumulation rates and pond perimeters and basin areas suggesting that peat may be a major source of sediment carbon. Aeolian transport is also a potentially large source of sediment carbon. Copyright © 2004 John Wiley & Sons, Ltd.     

Dynamics of evapotranspiration from a riparian pond complex in the Western Boreal Forest,Alberta, Canada

The relative contributions to total actual evapotranspiration (AET) from pond and riparian areas in a pond‐wetland complex in the Western Boreal Plain (WBP) of northern Alberta are measured using the Bowen ratio energy balance technique. Measurements show that a pond typical of the WBP evaporates at a rate more than twice that of the adjacent riparian peatland. Relating the actual to potential evapotranspiration over both surfaces yields Priestley–Taylor α coefficients of 0·69 and 1·11 for the peatland and pond respectively. Further results demonstrate that the sheltering and turbulent influences of the adjacent forested areas must be considered in the processes governing the permanence of WBP ponds. That is, forestry practices may inadvertently enhance the evaporative losses from the ponds, over and above the controls exerted by the regional climate. Copyright © 2006 John Wiley & Sons, Ltd.     

Groundwater vulnerability at the Solzanskii area of sludge-lignin accumulation ponds at the Baikal pulp-and-paper plant

The article presents the results of a hydrogeological survey aimed to substantiate the engineering recultivation of accumulation ponds of lignin mud by inwashing it with coal ash. The ash bed causes compression consolidation of lignin bed, leading to an increase in the pond seal margin. The mass exchange between the ash and the lignin mud is accompanied by changes in the hydrogeochemical conditions: the mineralization of the liquid phase of technogenic soils increases by a factor of up to 8, and the concentration of microcomplex increases to very high values. The analysis of the qualitative state of groundwater showed it to be tolerant to the effect of accumulation ponds. The moderate deviation from the local natural background is due to other pollution sources. The applied recultivation technology is effective and environmentally safe, though it needs modernization. The alternative technology, proposed by OOO VEB-Inzhiniiring, i.e., grouting the pond content, is extremely hazardous, and the implementation of the project involves considerable environmental risk because of the possible loss of pond containment.     

The erodibility of upland soils and the design of preafforestation drainage networks in the United Kingdom

Hydraulic thresholds for erosion of fourteen upland mineral and organic soils were determined in a hydraulic flume. These soils are from areas to be afforested in the United Kingdom. Some of the group are erosion resistant but others are susceptible to erosion once denuded of vegetation; for example, by preafforestation ploughing. These threshold data were required to calibrate a hydraulic model for effective design of preafforestation drainage networks on a variety of soils. However, simple field measures of soil properties indicative of erosion potential would be of value to the forestry industry for management purposes. Consequently, hydraulic threshold data were related by linear regression methods to basic soil properties, including organic content, grain size, bulk density, compression strength and penetration resistance. The investigation concluded that four peat soils are not eroded by clear water velocities up to 5·7 m s⁻¹, although a mineral bedload might induce erosion at lesser current speeds. Penetration resistance is a good field indicator of the degree of humification of the peat soils. Although selected physical parameters contribute resistance to water erosion, an increased organic content is pre-eminent in reducing erosion susceptibility in both organic and mineral soils. Although compressive strength was not indicative of soil erodibility, field measurements of penetration resistance on a variety of soils could be related to hydraulic thresholds of erosion; albeit through the construction of discriminant functions interpolated by eye. Consequently, organic content (laboratory) or penetration resistance (field) might form the basis of classifying upland soils in terms of erodibility. Mineral soils differ widely in terms of their erodibility, so that subject to further consideration, the use of ploughing for forestry cultivation might be appropriate in wider circumstances than presently recommended by the Forests and Water Guidelines. Ploughing should be acceptable on deep peat providing the underlying mineral soil is not exposed in the bottom of the furrow, and furrows are not led from mineral soils on to deep peat. © 1997 John Wiley & Sons, Ltd.     

Basal‐topographic control of stationary ponds on a continuously moving landslide

The Slumgullion landslide in the San Juan Mountains of southwestern Colorado has been moving for at least the last few hundred years and has multiple ponds on its surface. We have studied eight ponds during 30 trips to the landslide between July 1998 and July 2007. During each trip, we have made observations on the variability in pond locations and water levels, taken ground‐based photographs to document pond water with respect to moving landslide material and vegetation, conducted Global Positioning System surveys of the elevations of water levels and mapped pond sediments on the landslide surface. Additionally, we have used stereo aerial photographs taken in October 1939, October 1940 and July 2000 to measure topographic profiles of the eight pond locations, as well as a longitudinal profile along the approximate centerline of the landslide, to examine topographic changes over a 60‐ to 61‐year period of time. Results from field observations, analyses of photographs, mapping and measurements indicate that all pond locations have remained spatially stationary for 60–300 years while landslide material moves through these locations. Water levels during the observation period were sensitive to changes in the local, spring‐fed, stream network, and to periodic filling of pond locations by sediment from floods, hyperconcentrated flows, mud flows and debris flows. For pond locations to remain stationary, the locations must mimic depressions along the basal surface of the landslide. The existence of such depressions indicates that the topography of the basal landslide surface is irregular. These results suggest that, for translational landslides that have moved distances larger than the dimensions of the largest basal topographic irregularities (about 200 m at Slumgullion), landslide surface morphology can be used as a guide to the morphology of the basal slip surface. Because basal slip surface morphology can affect landslide stability, kinematic models and stability analyses of translational landslides should attempt to incorporate irregular basal surface topography. Additional implications for moving landslides where basal topography controls surface morphology include the following: dateable sediments or organic material from basal layers of stationary ponds will yield ages that are younger than the date of landslide initiation, and it is probable that other landslide surface features such as faults, streams, springs and sinks are also controlled by basal topography. The longitudinal topographic profile indicated that the upper part of the Slumgullion landslide was depleted at a mean vertical lowering rate of 5.6 cm/yr between 1939 and 2000, while the toe advanced at an average rate of 1.5 m/yr during the same period. Therefore, during this 61‐year period, neither the depletion of material at the head of the landslide nor continued growth of the landslide toe has decreased the overall movement rate of the landslide. Continued depletion of the upper part of the landslide, and growth of the toe, should eventually result in stabilization of the landslide. Published in 2008 by John Wiley & Sons, Ltd.     

Assessing Risks of Shallow Riparian Groundwater Quality Near an Oil Sands Tailings Pond

The potential discharge of groundwater contaminated by oil sands process‐affected water (OSPW) is a concern for aquatic ecosystems near tailings ponds. Groundwater in the area, but unaffected by OSPW, may contain similar compounds, complicating the assessment of potential ecological impacts. In this study, 177 shallow groundwater samples were collected from riparian areas along the Athabasca River and tributaries proximate to oil sands developments. For “pond‐site” samples (71; adjacent to study tailings pond), Canadian aquatic life guidelines were exceeded for 11 of 20 assessed compounds. However, “non‐pond” samples (54; not near any tailings pond) provided similar exceedances. Statistical analyses indicate that pond‐site and non‐pond samples were indistinguishable for all but seven parameters assessed, including salts, many trace metals, and fluorescence profiles of aromatic naphthenic acids (ANA). This suggests that, regarding the tested parameters, groundwater adjacent to the study tailings pond generally poses no greater ecological risk than other nearby groundwaters at this time. Multivariate analyses applied to the groundwater data set separated into 11 smaller zones support this conclusion, but show some variation between zones. Geological and potential OSPW influences could not be distinguished based on major ions and metals concentrations. However, similarities in indicator parameters, namely ANA, F, Mo, Se, and Na‐Cl ratio, were noted between a small subset of samples from two pond‐site zones and two OSPW samples and two shallow groundwater samples documented as likely OSPW affected. This indicator‐based screening suggests that OSPW‐affected groundwater may be reaching Athabasca River sediments at a few locations.     

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.     

ODE TO THE SAN LUIS DRAIN

Abstract. The San Luis Drain (SLD) has enabled us to learn quickly the facts and effects of irrigating only 8,000 acres of seleniferous soils: the dissolving and organic uptake of selenium, its dissemination from ponds, entry into food chains, and accumulation in a wide variety of biota and detritus. If deprived access to SLD, the Westlands Water District (WWD) could direct their toxic wastes down natural slopes by trickling or sumps and drain ditches, but this means toward the Mendota Pool and the Main Canal and Outside Canal which carry water for irrigation and domestic wells; that is more ominous to Merced County than the SLD ever was.
The WWD needs detailed testing and mapping of its irrigable lands to discriminate the areas of seleniferous soils from those which are safe for irrigation. In the meantime, in irrigated lands above the Delta-Mendota Canal, all sumps and drains should be monitored for selenium in toxic concentrations, and irrigation should cease in the areas producing the excessive selenium. Monitors along the Outside and Main Canals (below drainage from known seleniferous areas) might be needed for preservation of good quality, perhaps by dilution with CVP water.     

Sediment‐water Fluxes of Nutrients and Dissolved Organic Carbon in Extensive Sea Cucumber Culture Ponds

Sediment samples were collected from three seawater aquaculture ponds, and soil characteristics, sediment oxygen consumption (SOC), dissolved organic carbon (DOC) and nutrient fluxes were measured using chamber incubations at laboratory. The three ponds were each representing a specific monoculture or polyculture model of sea cucumber. Total organic carbon (TOC) and total nitrogen (TN) contents in the dry sediment ranged from 0.14 to 0.26% and 0.022 to 0.037%, respectively. Total phosphorus (TP) contents in the sediment were more spatially and temporally variable. SOC ranged from 15.29 to 45.86 mmol m^–2 d^–1 and showed significant differences among the three ponds (p < 0.05). TOC, total carbon (TC) contents, and SOC of the sediment in the pond polycultured with jellyfish increased with culture time, indicating that jellyfish farming enhanced the accumulation of organic matter in the sediments to some extent. Sediment showed net nitrate and ammonium uptake in most ponds and months, and significant differences were found among months (p < 0.05). Dissolved inorganic phosphate (DIP) was released from the sediments in all ponds with low flux rates. DOC was released from the sediment in all ponds and ranged from 0.67 to 1.74 g DOC m^–2 d^–1. The results suggested that non‐artificial‐feeding sea cucumber culture ponds could not only yield valuable seafood products, but also effectively remove nutrients from the aquaculture systems and consequently alleviate nutrient loadings of the nearby coast.     

Nutrient dynamics in water and sediment of Mediterranean ponds across a wide hydroperiod gradient

In Mediterranean ponds, summer drought enhances seasonality whose intensity varies along topographic and climatic gradients. The alternation of wet and dry periods in rain dependent ponds affects their biogeochemistry and differentiates them from ponds fed by more stable water sources, such as groundwater springs. Superimposed onto this, land use is also a very strong factor of variability. In this study we compared nutrients and organic matter concentrations, in water and in sediment, among different types of Mediterranean ponds based on the source of water, hydroperiod and land use. Forty-three ponds were sampled in Eastern Spain corresponding to five pond types: (1) permanent spring ponds in lowlands, (2) permanent spring ponds in mountains, (3) semi-permanent rain ponds, (4) temporary rain ponds with long hydroperiod and (5) temporary rain ponds with short hydroperiod.The results of this study indicate relevant differences among these pond types. The temporary rain ponds with short hydroperiod are characterized by high turbidity due to suspension of sediment particles rich in phosphorous adsorbed onto them (argillotrophic aquatic systems). They are used for watering domestic sheep that enhance sediment suspension by trampling. Total phosphorous (TP) concentrations in the water are high (like those of hypertrophic lakes), but planktonic chlorophyll a is very low and not correlated with TP, because of the low P-bioavailavility in the water. At the other extreme, we have permanent ponds in lowlands fed by groundwater springs. They are heavily loaded with nitrates due to the surrounding intensive agriculture. In these and other permanent/semipermanent ponds chlorophyll is highly correlated with TP. Sediment characteristics provide a good indication of the hydroperiod, since desiccation has important effects on biogeochemical transformations. A threshold of 5% organic matter (OM) in the sediment separates temporary ponds with a short hydroperiod from those with a long hydroperiod, and a threshold of 8% separates the later from the semi-permanent and permanent ponds. Besides OM reduction, important loss of N occurs during desiccation through mineralization, ammonia volatization and the sequential nitrification/denitrification pathway. On the other hand, the increase of organic P mineralization in dry sediments does not represent a loss of P from the system, since o-P remains adsorbed or bound onto the soil. This leads to a low TN/TP ratio in sediments in temporary ponds with short hydroperiod. These characteristics have to be taken into account when establishing pond typologies and ecological thresholds to assess water quality in these unique aquatic habitats.     

THE RESPONSE OF SAG POND SEDIMENT TO THE PALEOEARTHQUAKE EVENT ON THE XIADIAN FAULT ZONE

The wedge-shaped deposit formed in front of fault scarp is called colluvial wedge. Repeated faulting by faults may produce multiple colluvial wedges, each of which represents a paleoseismic event. When there are two or more colluvial wedges, the new colluvial wedge is in sedimentary contact with the fault, while the old ones are in fault contact with the fault. The shape of colluvial wedge is usually in the form of horizontal triangle, and the sedimentary facies is usually of binary structure. The overall grain size decreases gradually from bottom to top. Soil layer generally develops on the top, and different types of soil are developed under different climate or soil environments. Another deposit in front of fault scarp is the sag pond graben. The graben in front of sag pond is generally a set of sedimentary assemblages of colluvial facies, alluvial diluvial facies and swamp facies. The area close to the fault, especially the main fault, is of colluvial facies, while the area away from the fault is of alluvial and pluvial facies and marshy facies. In an accumulative cycle, the size of the deposit decreases from bottom to top, and soil layers develop on the top or surface. Multiple pile-ups may be a marker for identifying multiple faulting events. The pile-up strata such as colluvial wedge and fault sag pond can be used as identification markers for paleoseismic events. Colluvial wedge and sag pond, as the identification markers for paleoearthquake, have been well applied to practical research. However, there is still lack of detailed research on the lithological structure and genetic evolution in the interior of colluvial wedge and sag pond sediment, meanwhile, there is still a deficiency in the analysis of the completeness and the regional characteristics of paleoearthquake by using colluvial wedge and sag pond sediment. This paper discusses the method of identifying paleoearthquake by using sag pond sediments and colluvial wedge. We discuss the lithologic combination and sedimentary evolution of sag pond and choose the surface rupture zone of the 1679 M8.0 earthquake on the Xiadian Fault as the research area. In this paper, the distribution range and filling sequence of sag pond are analyzed, using borehole exploration. Four paleoearthquake events are identified since 25ka to 12ka, based on the sag pond sediments and colluvial wedge. The in situ recurrence interval of these seismic events is 480a, 510a, 7 630a and 2 830a, respectively. The lithologic combination and sedimentary evolution law of the sag pond sediments caused by an ancient earthquake are discussed. The sag pond distribution range and filling sequence are determined by the surface elevation survey and drilling exploration. The exploratory trench exposes the sag pond filling strata sequence and lithologic combination. Based on this, we analyze the three sedimentation stages of sag pond sediments formed by a paleoearthquake event near the earthquake fault. It is believed that the filling sequence is composed from bottom to top of the colluvial wedge, the erosion surface or unconformity surface, the fine detrital sediments(containing biological debris)and paleosols. For the fault-sag ponds formed by active faults, the paleoearthquakes occurred near the unconformity or erosion surface of the sediments of the fault-plug ponds. An ancient earthquake event includes the combination of organic deposits such as sediments, clastic deposits, bioclasts, burrow, plant roots and other organic deposits on the vertical scour surface or unconformity. The time interval between two paleoseismic events is defined by two adjacent unconformities(or scour surfaces). According to the vertical facies association and chronological test results of the sediments in the Pangezhuang trough of the Xiatan Fault, four paleo-seismic events are identified since the late Pleistocene period of 25~12ka BP, with recurrence intervals of 480a, 510a, 7 630a and 2 830a, respectively.     

Removal mechanisms of nitrogen in waste stabilization ponds

The aim of this research work was to determine the major nitrogen transformation and removal mechanisms in primary and maturation ponds. To accomplished this objective, nitrogen mass balance in waste stabilization pond system was determined using a dynamic mathematical model in order to elucidate the biological nitrogen transformation mechanisms that are effective for removal of nitrogen in this pond system. Results show that nitrogen removal efficiency in a primary facultative pond unit was 13.2%, which was largely due to net loss of organic nitrogen to sediments (9.76%) and denitrification (3.42%). On the other hand, maturation pond removed 15.2% of nitrogen received in the influent with denitrification (13.55%) being the major pathway for nitrogen removal. Ammonia volatilization was not a predominant mechanism for nitrogen removal in both primary facultative and maturation ponds. The major nitrogen transformation routes were mineralization and ammonia uptake in the primary facultative pond, but ammonia uptake by microorganisms was a predominant nitrogen transformation mechanism in maturation pond.     

太湖流域池塘养殖污染排放估算及其空间分布特征

池塘养殖是农业源污染的重要来源之一,尤其在水网密布、渔业发达的太湖流域,控制池塘养殖过程中氮、磷、化学需氧量等污染物的排放,对于减轻水体富营养化程度、恢复水质健康、维持地区社会经济可持续发展具有重要意义.基于野外采样、入户调查、遥感解译等多种手段,结合GIS软件技术,对太湖流域池塘养殖污染物的排放进行了估算.结果表明,20142015年太湖流域总氮、硝态氮、铵态氮、总磷、可溶性磷、COD Cr的年排放量分别为6.1×10^6、1.1×10^6、1.7×10^6、1.3×10^5、1.1×10^5和8.0×10^7 kg.其中鱼类池塘养殖排放系数分别为69.5、12.4、20.1、1.6、1.3和919.8 kg/hm 2;虾类池塘排放系数分别为3.0、0.5、0.9、0.07、0.06和39.3 kg/hm^2;蟹类池塘排放系数分别为6.4、1.2、1.9、0.2、0.1和84.9 kg/hm^2.太湖流域池塘养殖各类污染物排放分布特征为位于太湖西北部、南部和东北部的大部分地区池塘养殖污染物排放较高,位于太湖东部和太湖西南部的池塘养殖污染物排放较低.池塘养殖业发达、饲料肥料投入高、养殖密度大等是造成该流域池塘养殖污染物排放较高的主要原因.针对太湖流域池塘养殖减排治理,建议推行合理的池塘污染治理管理政策与策略,综合考虑饲料利用率与投放量、养殖面积、养殖密度、养殖生物生态混养,以及一些科学养殖管理措施和净化养殖废水的技术措施等.     

Phytoplankton Distribution in an Oligotrophic Pond and a Eutrophic Pond

Summary: An oligotrophic pond and a eutrophic pond of Bhagalpur, India, were studied for phytoplankton distribution and to establish the relationship between this distribution and the physico-chemical properties of the water. Altogether, 114 algal taxa were identified. In Rekabganj pond, diatoms constituted 54.4 % of the algal species followed by green algae (29.4 %), blue greens (11.7 %) and euglenoids (2.9 %). In Ramna pond, blue greens were the most dominant comprising 35.7 % of algal species followed by green algae (32.8 %), diatoms (18.5 %) and euglenoids (8.5 %). The members of Dinophyceae, Chrysophyceae and Xanthophyceae were poorly represented in both the water-bodies. Aphanizomenon flos-aquae, Microcystis aeruginosa, Chlorella vulgaris, Cladophora crispata, Volvox aureus and Euglena spp. were recorded only in Ramna pond, indicating its higher nutrient status. Dinobryon calciformis, many pennate diatoms and desmids, indicators of oligotrophy, were observed in Rekabganj pond only. Measurements of water properties in the two ponds showed that transparency, dissolved oxygen and silicate were higher in Rekabganj pond than in Ramna pond, while total alkalinity, hardness, total dissolved solids, dissolved organic matter, different cations, phosphate, nitrate and chloride were lower in Rekabganj pond than in Ramna pond.     

Footpath morphology and terrain sensitivity on high plateaux: the Mamore Mountains,Western Highlands of Scotland

Variations in the morphology of a high‐level footpath are characterized using a new approach that relates footpath morphology to six terrain units defined jointly by two contrasting plant communities (U7 grass–heath communities dominated by Nardus stricta and Carex bigelowii, and U10 moss–heath communities dominated by Carex bigelowii and Racomitrium lanuginosum) and by the contrasting textural characteristics of underlying mineral soils developed on schist, granite and quartzite. All six terrain units are characterized by distinct footpath morphologies. The most critical factor affecting footpath morphology is the shear strength of the vegetation mat and underlying root zone. Vegetation mat shear strength was measured using a specially constructed shear rake. On all three lithologies, median shear strengths for U7 communities significantly exceed those for U10 communities, so that pathways on the former are significantly narrower and deeper than those developed on the latter. Adjacent zones of damaged or modified vegetation cover are also wider on U10 communities. The role of mineral soil (regolith) texture and thus underlying lithology in controlling footpath morphology is more complex. For soils with abundant fines, granite soils have lower shearing resistance than schist soils, and are associated with wider footpaths. Footpaths are also wide on clast‐supported quartzite regolith, which has high shearing resistance: pathways are trapezoidal in cross‐section in areas of U7 vegetation cover, but footpaths are very broad and diffuse in areas of U10 cover. Pathway depths are limited by increasing shear and compressive strength with depth. Implications of these findings for further research and management strategies are discussed. Copyright © 2007 John Wiley & Sons, Ltd.     

低湿洼地鱼塘中异养细菌的矿化作用

对黄淮海平原低湿洼地鱼塘中异常细菌的矿化作用进行了初步研究,结果表明：（１）鱼塘水体中异养细菌的呼吸强度与鱼塘水体中的有机物质含量及温度密切相关;（２）鱼塘水体中异养细菌的生物量表现出明显的季节性变化;异养细菌的生物量在表层水及底层水之间的差异不明显。（３）鱼塘水体中异常细菌分解有机物质的动力学特点如下：开始时,鱼塘水体中有机物质的转化较少,随温度的增高及异养细菌生物量的增加,水体中的矿化作用逐渐     

典型农业流域不同类型池塘水体CO2排放特征

内陆水体是大气CO₂收支估算的重要组成部分。农业流域分布着大量池塘景观水体,且具备蓄洪抗旱、消纳污染、水产养殖等多种功能。但是,农业流域不同功能的小型池塘CO₂排放特征尚不清楚。本研究以极具农业流域代表性的烔炀河流域为研究对象,选取流域中用于水产养殖(养殖塘)、生活污水承纳(村塘)、农业灌溉(农塘)、蓄水(水塘)的4个功能不同的景观池塘,基于为期1年的野外实地观测,以明确农业流域小型池塘CO₂排放特征。结果表明,不同功能池塘水体CO₂排放差异显著,受养殖活动、生活污水输入和农田灌溉等人类活动影响,养殖塘((80.37±100.39) mmol/(m²·d))、村塘((48.69±65.89) mmol/(m²·d))和农塘((13.50±15.81) mmol/(m²·d))是大气CO₂的热点排放源,其CO₂排放通量分别是自然蓄水塘((4.52±23.26) mmol/(m²·d))的18、11和3倍。统计分析也表明,该流域池塘CO₂排放变化总体上受溶解氧、营养盐等因素驱动。4个不同景观池塘CO₂排放通量全年均值为(37.31±67.47) mmol/(m²·d),是不容忽视的CO₂排放源,其中养殖塘和村塘具有较高的CO₂排放潜力,在未来研究中需要重点关注。     

Aluminum compounds in surface waters and soils of different southern taiga ecosystems in the upper part of the Mezha R.

Regularities in the distribution of some Al compounds in surface water in different southern taiga ecosystems have been studied. The main source of Al in surface water in both ecosystems has been shown to include the top organogenic and mineral horizons of soils within the 40–50-cm loam deposits, underlain by moraine loam. Al concentration in surface water is 1–2 orders of magnitude greater than that in a spring’s water. The amount of Al carried out from ecosystems with predominant occurrence of peat-podzol-gley soils is greater that from ecosystems with dominating podzol soils. In creeks in ecosystems with peat-podzol-gley soils, Al occurs both as a component of organoaluminum compounds and as monomeric aquahydroxocomplexes. In creeks that drain a territory with dominating podzol soils, almost all Al occurs in complexes with organic matter. Al concentration has been shown to have seasonal dynamics, and the concentration of toxic compounds in surface water has been predicted to increase because of anthropogenic acidification.     

Heat as a tracer to estimate dissolved organic carbon flux from a restored wetland

Heat was used as a natural tracer to characterize shallow ground water flow beneath a complex wetland system. Hydrogeologic data were combined with measured vertical temperature profiles to constrain a series of two-dimensional, transient simulations of ground water flow and heat transport using the model code SUTRA (Voss 1990). The measured seasonal temperature signal reached depths of 2.7 m beneath the pond. Hydraulic conductivity was varied in each of the layers in the model in a systematic manual calibration of the two-dimensional model to obtain the best fit to the measured temperature and hydraulic head. Results of a series of representative best-fit simulations represent a range in hydraulic conductivity values that had the best agreement between simulated and observed temperatures and that resulted in simulated pond seepage values within 1 order of magnitude of pond seepage estimated from the water budget. Resulting estimates of ground water discharge to an adjacent agricultural drainage ditch were used to estimate potential dissolved organic carbon (DOC) loads resulting from the restored wetland. Estimated DOC loads ranged from 45 to 1340 g C/(m2 year), which is higher than estimated DOC loads from surface water. In spite of the complexity in characterizing ground water flow in peat soils, using heat as a tracer provided a constrained estimate of subsurface flow from the pond to the agricultural drainage ditch.