稻田沟渠-湿地系统的碳氮稳定同位素组成特征

由于稳定同位素在特定污染源中具有特定的组成,在污染物质迁移转化过程中作为示踪剂而广泛应用。针对目前农业面源污染较为严重的现状,该文利用碳氮稳定同位素研究了灌区内外源物输入对稻田沟渠-湿地系统的贡献。结果表明,水中颗粒性有机物(particulate organic matter,POM)由于受到光照、营养物质不同导致POM在各采样点组成不同,δ13C变化范围较大,均值为-27.8‰,与大型水生植物和浮游植物接近,此类植物可能是POM的主要来源。水中δ13CDIC(dissolved inorganic carbon,DIC)与浮游植物呈线性相关,浮游动物δ13C与浮游植物存在一定相关性,而浮游植物与POM之间不存在显著性差异,说明研究区内浮游动物对內源有机碳的利用主要是取食浮游植物低持斜聿愠粱?δ13C值变化范围在-27.2‰～-21.8‰之间,明显高于水体POM含量,说明表层沉积物存在比颗粒有机物更富集碳的藻类与陆源碎屑等物质。各采样点颗粒有机物δ15N值的范围3.1‰～4.2‰,平均值为3.6‰,其中湿地δ15N高于其他采样点。沉积物δ15N平均值为-0.6‰,与大气中N2较为接近。     

An Integration of Water Physicochemistry,Algal Bioassays,Phytoplankton, and Zooplankton for Ecotoxicological Assessment in a Highly Polluted Lowland River

Results of different approaches potentially useful for the evaluation of water ambient quality were analysed and compared in a small temperate lowland river with mixed diffuse and multiple-point source pollution. The Reconquista River (Buenos Aires Province, Argentina), one of the most polluted watercourses of Latin America, receives agrochemicals as well as domestic and industrial (mostly untreated) effluents. Physical and chemical water variables were determined; unispecies algal bioassays (with Chlorella pyrenoidosa and Scenedesmus acutus) were carried out in laboratory; and density and structure of phyto- and zooplankton were analysed at three sites in four dates (representing a range of likely conditions in the river). A general scheme of association among plankton, bioassays and physical/chemical variables was elaborated, that helped to infer possible control factors in this multi-stressed system. Some empirical methods, but mainly mathematical ones including multivariate techniques (as PCA, cluster analysis), were applied for evaluation of samples. A preliminary selection of indices and attributes as potential indicators of the water river quality was made, and then applied for assay a tentative integrative ordination of samples. The relative best water quality was recorded when-where dissolved oxygen concentration, algal diversity and planktonic crustacean density were higher. The worst water quality corresponded to the lack of cladocerans and lowest crustacean density, and higher: organic and industrial pollution, major nutrients (ammonium and orthophosphates), BOD, hardness, conductivity, algal biomass in bioassays, phytoplankton density (>10 000 ind. mL^-1), dominance of a single algal species (>90%), and rotifer proportion in zooplankton (>85%).     

In Situ partitioning and biomagnification of mercury in industrially polluted Husainsagar Lake,Hyderabad, India

The distribution of Hg in water, sediment, plankton and fish along with the in situ biomagnification of the metal in Husainsagar Lake, India were measured. The concentration of Hg in the water was 10 μg L^?1 and exceeded the water quality criteria standards. Sediments of the lake at different sites had Hg concentrations several thousand fold more than that of the overlying water column and showed relationship with the water content of the wet sediment. Sediments in the lake acted as a `sink' for the metal. The concentrations of Hg increased from nanoplankton → phytoplankton -> zooplankton. Fish, an end organism in the food chain, had Hg concentrations higher than that of nanoplankton and lower than those of phytoplankton and zooplankton. This trend did not illustrate the expected pattern of food chain enrichment in the classical sense as noted for chlorinated hydrocarbons (DDT).     

放牧对希拉穆仁草原土壤入渗过程影响的定量评估

为定量评估放牧对草原土壤入渗的影响,了解和防治放牧造成的水土流失,科学评估草原水文调节功能,采用双环入渗法研究了放牧对典型草原土壤入渗性能的影响,并收集影响土壤入渗的环境特征变量.结果表明:(1)土壤入渗能力均受到放牧活动的干扰,随着放牧强度的增加,土壤初渗速率、稳渗速率减小,达到稳渗时的历时缩短,而轻度放牧对土壤入渗...     

Numerical intermediate and far field dilution modelling

Studies of wastewater outfalls to coastal waters are now being performed using numerical hydrodynamic and transport models. Modelling of coastal waters requires specifying tidal boundary conditions along open water boundaries. It is not possible to obtain open water tidal boundary conditions from tide height observations alone because the datum between different tide gages cannot be determined to the accuracy required for numerical modelling. Presented in this paper is a method for estimating open water tidal boundary conditions from coincident current meter and pressure sensor measurements. The methodology is applied to a numerical hydrodynamic and transport model to analyze the dilution field and rate of sedimentation around a proposed wastewater outfall into outer Saint John Harbour on the Bay of Fundy. The intermediate and far field numerical model used in this study includes the momentum of the discharge to account for near field mixing.     

再生水灌溉模式对潮土结构性质及导水性能的影响

为揭示再生水不同灌溉模式下土壤结构性质及导水性能的差异。通过室内模拟土柱入渗试验,以清水灌溉为对照(CK),研究了再生水持续灌溉(RW)、再生水—清水混合灌溉(RW-2)及再生水—清水交替灌溉(ARW)3种灌溉模式对土壤容重、总孔隙度、团聚体稳定性、入渗率及饱和导水率的影响。结果表明:相比CK,各处理容重呈降低趋势,总孔隙度增加,但差异均不显著;再生水灌溉促进潮土>1mm粒级团聚体向<1mm粒级团聚体转化,相比CK,各处理<1mm粒级团聚体含量分别增长11.51%~31.22%;潮土团聚体水稳定性降低;各处理>0.25mm粒级团聚体含量分别降低2.92%~9.75%,平均质量直径分别降低11.30%~38.38%,几何平均直径分别降低3.93%~12.78%,其中RW最为显著;相关性分析表明,>1mm粒级水稳性团聚体含量对潮土结构稳定性贡献最大;再生水3种灌溉模式下潮土入渗率分别显著增长80.00%~260.00%;ARW处理潮土有效导水率上升22.68%,而RW和RW-2处理土壤有效导水率分别下降14.47%和42.36%。保持潮土结构性质方面以RW-2处理最好,改善潮土导水能力方面则以ARW处理最为显著。     

Modeling Flushing and Mixing in a Deep Estuary

The distribution of constituents from discharges in estuaries can be determined only to the detail with which the time-varying velocity field is known. Deep estuaries can exhibit complex vertical and horizontal circulation structures depending on tides, freshwater inflows, density stratification, and geometry. A numerical, time-varying, three-dimensional hydrodynamic and transport model is applied to the Gastineau Channel, a deep estuary in Alaska, to determine the dilution of material discharged from a submerged outfall into the Channel. The ability of the model to produce realistic flow fields is first confirmed by comparing computed velocities to measured velocities for stratified and unstratified conditions. Methods are then shown for determining the flushing rate of the estuary and the distribution of dilution throughout the estuary for these same conditions.     

Species diversity and water quality in Galveston bay,Texas

The relationships between species diversity of phytoplankton, zooplankton, nekton and benthos samples and the water quality of Galveston Bay, Texas were quantitatively compared. Two water quality parameters (i.e., percent waste water or the toxicity of the water at a given sampling station) were found to be inversely correlated with species diversity. A computerized dispersion model was used to calculate percent waste water. Toxicity was measured by subjecting a blue-green alga (Coccochloris elebans) to water samples and by utilizing growth depression as the toxicity criterion. Waters from the Houston Ship Channel and the Trinity River were found to be significantly toxic and the dispersion model was again used to determine the distribution of toxicity to each bay area. Evidence that toxicity was dispersed with input waters was experimentally verified. Those areas receiving the greatest amounts of toxic effluent exhibited the lowest mean annual diversities. Predictive equations were generated, indicating that diversity at any point in the bay can be computed from Houston Ship Channel diversity and the dispersion model. Computations were also accomplished whereby dilution and/or treatment of waste inflows could be estimated to achieve a desired and/or acceptable diversity level in the bay.     

Northern Lakes Recovery Study (NLRS) — Biomonitoring at the Ecosystem Level

NLRS is a joint Canadian/Norwegian study of the pace and extent of recovery of lake ecosystems from acidification. Twenty-one oligotrophic lakes within Killarney Park, Ontario were selected as the principal Canadian sites for this study. NLRS objectives for Killarney included: testing of new biomonitoring techniques, assessment of multiple stressor effects on recovery, and development of biological endpoints for critical load modelling. Sampling included: phytobenthos, phytoplankton, pelagic zooplankton, littoral zooplankton, sublittoral chironomids, and fish, as well as sediment cores for paleolimnological assessment of pre-industrial biotic communities. Strong statistical models were developed relating biotic composition to water quality variables. Prediction of future recovery will require additional understanding of the effects of differential colonization rates, climate variability, and the impact of unique events such as the arrival of an exotic species. Recovery proved to be best measured against modern reference data from circumneutral lakes rather than against historic data from acidified systems.     

Least limiting water range: A potential indicator of changes in near-surface soil physical quality after the conversion of Brazilian Savanna into pasture

The Brazilian savanna, or “Cerrado”, is an ecosystem that originally covered more than 200 Mha in Brazil. It is estimated that about 49.5 Mha in the Cerrado are now covered with cultivated pastures, which are responsible for half of Brazilian beef production. However, soil and pasture degradation represent a threat to this productive system and to the Cerrado ecosystem itself. Thus, the objective of this research was to evaluate the least limiting water range (LLWR) as an index of near-surface soil physical quality after conversion of Brazilian savanna to continuous and short-duration grazing systems. Three sites were evaluated: native Cerrado (NC), continuous grazing (CG), and short-duration grazing (SG). Thirty soil cores (5 cm height, 5 cm diameter) were collected at each site, and used for soil bulk density, soil water retention curve, and soil penetration resistance curve determinations. The results were used for quantification of LLWR and critical bulk density (D_bc), in which LLWR equals zero. The near-surface soil physical quality, as evaluated by the LLWR, was most restrictive for potential root growth in SG. In CG, potential restriction was moderate; however, the entire soil bulk density range was below the D_bc. In NC, potential restriction was minimum. The soil structural degradation process was primarily related to the increase in stocking rates in the grazing systems. The LLWR proved to be a useful indicator of Cerrado soil physical quality, being sensitive to alterations in near-surface physical properties.     

水利开发对二滩水库浮游植物及水质状况季节性影响

2010—2014年连续5 a（春季、夏季、秋季、冬季）对四川二滩水库进行浮游植物及水质定点采样调查,研究水利开发对浮游植物种类组成、数量特征、群落多样性及水质状况的影响。结果表明:（1）水利开发区共检出浮游植物7门251种,绿藻门（Chlorophyta）90种,所占比例为35.86%,对照区共检出浮游植物7门166种,绿藻门68种,所占比例为40.96%,水利开发区和对照区浮游植物种类在夏季和秋季较高,春季和冬季较低;（2）二滩水库水利开发区和对照区浮游植物Shannon-Wiener多样性指数（H）、Pielou均匀度指数（J_P）、Margalef种类丰富度指数（S）在夏季和秋季较高,春季和冬季较低,随季节呈先增加后降低趋势,而浮游植物密度（D）在秋季最低,不同季节浮游植物密度和丰富度指数均表现为水利开发区显著或者极显著高于对照区,多样性指数和均匀度指数均表现为对照区极显著高于水利开发区（p < 0.01）;（3）水利开发区和对照区水温、pH,TN,NH₄⁺-N,TP,高锰酸钾指数,BOD₅和COD_cr浓度呈一致的变化规律,随季节的变化呈先增加后降低趋势,秋季最高,春季和冬季较低,其中水温在夏季最高,透明度随季节变化呈“V”字形规律,在春季最高,秋季最低,而水温和TP浓度在水利开发区和对照区并没有明显差异;不同季节pH,TN,NH₄⁺-N,高锰酸钾指数,BOD₅和COD_cr浓度均表现为水利开发区高于对照区,局部有所波动,在冬季二者的差异不明显,说明了水利开发对二滩水库冬季水质的影响较小;（4）相关性分析表明二滩水库浮游植物群落多样性与水温和TN浓度呈显著或极显著正相关,与pH呈显著负相关,说明pH、水温和TN含量是影响二滩水库浮游植物多样性的主要因素。     

艾比湖退化湿地的生态恢复

精河入湖口是典型干旱区湖泊湿地,也是艾比湖湿地的重要组成部分。近50年来,由于人类活动及气候变化等多种因素影响,艾比湖湿地生态系统健康受到威胁,出现不同程度的退化。为改善和恢复生态环境,自2004年开始实施湿地恢复实验工程。选择未恢复区、恢复1年区、恢复3年区和恢复5年区,比较其水、浮游生物、植被、土壤及碳循环等生态特征,结合野外调查及试验数据分析,对其恢复状态进行监测和评价。结果显示,至2009年,试验区湿地水域面积比例增加,水质得到改善,植被群落呈正向演替,土壤达到中、轻度盐碱化土水平,水禽种类增加,生物多样性更加丰富,土壤呼吸速率随恢复时间延长而逐渐提高。由此表明,只要水源充足,精河入湖口退化湿地在恢复过程中经4～5年即可恢复到未退化状态,以恢复湿地水文条件为核心措施的湿地恢复方案具有可行性。研究对于干旱区其他类型湿地的恢复及生态功能的改善具有指导作用。     

Impact of fish introduction on planktonic food webs in lakes of the Patagonian Plateau

Patagonia fishless ponds have been stocked with fishes for recreational purposes since early in the 20th century. We carried out a summer plankton sampling in 18 Patagonian lakes; 12 fishless, 5 with introduced fishes and 1 with endemic fish fauna. The lakes are situated on a latitudinal gradient from 39° to 49°S. Zooplankton and phytoplankton composition, phytoplankton relative abundance, and zooplankton body size and mouthpart morphology were analyzed. Results showed differences between lakes with and without fishes; in the presence of fish zooplankton size spectrum tended to be narrower because of the disappearance of Daphnia and large centropagid copepods. Zooplankton composition changed: centropagid species richness decreased and rotifers dominated. Contrarily, in fishless lakes 3 or 4 centropagid species, differing markedly in body size and exploiting different food niches, were observed co-occurring. These changes in zooplankton seemed to cascade down to phytoplankton. Fish introduction increased the phytoplankton similarity in lakes even belonging to different basins in a latitudinal gradient. Indeed, cyanobacteria dominated only in lakes with introduced fishes. Probably the elimination of Daphnia favored cyanobacteria proliferation due to nutrient rebalance. As a consequence, water quality decreases and the value of sport fisheries is reduced. Fish introduction in Patagonia is a practice that should be re-evaluated by governments and NGOs due to its potentially negative impact on lakes and local economies.     

Collembolan grazing affects the growth strategy of the cord-forming fungus Hypholoma fasciculare

Mycelia of cord-forming fungi show remarkable patterns of reallocation of biomass and nutrients indicating an important role of these, often extensive, organisms in the spatial translocation of energy and nutrients in forest soils. Despite the rich tradition of interaction studies between soil microarthropods and fungi, the spatial implications of these interactions, due to the potential growth responses of the fungi and to the translocation of energy and nutrients within the mycelial network, have been largely ignored. In this paper we analyse fungal growth responses in two-dimensional model systems composed of compressed soil, the cord-forming fungus Hypholoma fasciculare and three fungivorous Collembolan species. We hypothesised that (i) the highly co-ordinated nature of cord-forming fungi would lead to growth responses following collembolan grazing, and that, (ii) such changes are dependent on grazing intensity, and (iii) changes are dependent on the species grazing. Mycelial extent and hyphal cover decreased with increasing grazing density; at highest grazing density also the fractal dimension of the mycelial border decreased, indicating a less branched foraging front due to the regression of fine hyphae and the development of mycelial cords. Effects differed greatly between collembolan species although they exerted comparable grazing pressure (the smaller species were added in larger numbers according to their allometric size-metabolic rate relationships): while grazing by Folsomia candida resulted in less mycelial extension and hyphal cover, these variables were not affected when Proisotoma minuta and Hypogastrura cf. tullbergi grazed. The effects of a species mix suggested an additive effect of the component species. This shows that fungal mycelia may suffer from damage caused by few but large collembolans, affecting extension as well as coverage of the mycelium, but that fungi may compensate for the biomass loss caused by more but slightly smaller collembolans. In about 20% of the model systems H. fasciculare switched from a growth pattern with a broad contiguous foraging front and uniform growth in all directions to a pattern with fast growing sectors while other sectors stopped growth completely. The switch occurred in grazed systems exclusively; thus we interpret this observation as a fugitive response and as a strategy for quickly escaping from places where grazing pressure is experienced.     

Effects of deer grazing and fence-line pacing on water and soil quality

Abstract. We studied the effects of red deer grazing and fence-line pacing on soil losses of contaminants (suspended sediment, Escherichia coli , phosphorus) and nitrogen species (ammonia, nitrate) via overland flow and soil physical properties (macroporosity, bulk density, saturated hydraulic conductivity, K _sat) soon after (1 day) and 6 weeks after grazing on a Pallic pastoral soil in southern New Zealand. Fence-line pacing decreased the soil volume occupied by water, macroporosity and K _sat, while increasing suspended sediment (to 0.226 g 100 mL⁻¹), total P (to 2.0 mg L⁻¹), mainly as particulate P (up to 90% of total P), and E. coli (to 3.52 log₁₀ c.f.u. 100 mL⁻¹) concentrations in overland flow at 1 day after grazing compared with soils from the rest of the paddock (0.148 g 100 mL⁻¹, 0.86 mg L⁻¹ and 2.86 log₁₀ c.f.u. 100 mL⁻¹, respectively). Although concentrations in overland flow were less at 6 weeks after grazing than at 1 day after grazing, losses of P, especially in fence-line soils, were still above recommended limits for surface water quality. Compared to P, losses of N species would be unlikely to have a significant impact on downstream water quality. Management strategies should be directed towards minimizing the occurrence of fence-line pacing to prevent contaminant loss and maintain water and soil quality.     

In situ compartmentation and biomagnification of chromium and manganese in industrially polluted Husainsagar Lake,Hyderabad, India

The concentrations of Cr and Mn in water, sediment, nanoplankton, phytoplankton, zooplankton, and fish were determined during 1983–1984, to investigate biomagnification of these metals in Husainsagar Lake, India. The concentration of Cr in the water phase was above the permissible limits and Mn exhibited complex distribution pattern. The high concentrations of Cr and Mn in the surficial sediment was related to an increase in the intensity of in situ processes, mainly the enrichments of these metals in the organisms. The concentration of Cr was least in nanoplankton and remained the lowest in samples of phytoplankton, zooplankton and fish. The concentration of Mn decreased from nanoplankton to fish, except in phytoplankton which showed the highest concentration. This trend did not illustrate the expected pattern of food chain enrichment in the classic sense of the term as noted for Hg and DDT. Furthermore, the Mn, but not the Cr, concentrations decreased with the increase in body weight of the fish.     

Maintaining estuary quality for shorebirds: towards simple guidelines

It is increasingly important to be able to monitor and maintain the quality of estuaries for overwintering shorebirds. Bird numbers alone are not sufficient to indicate quality nor, as recent research shows, can it be assumed that site quality is being maintained simply because there is enough food to meet the birds’ physiological demands; i.e., the amount of food available per bird in autumn needs to be greater than the amount eaten. But how much greater? We used a simple individuals-based and behaviour-based model to explore the factors that affect the relationship between overwinter mortality and the amount of food available per bird in autumn (the food:bird ratio). The aims were to explore how the natural history characteristics of a shorebird species affected the shape of this relationship, in order to identify characteristics of the system that should be included in any monitoring programme of site quality. In all cases there was a minimum threshold food:bird ratio above which mortality did not vary and below which mortality increased steadily. The amount of food per bird required at the threshold varied from one to six times the amount actually consumed by each bird during winter, depending on the amount of realism included in the model. The minimum threshold ratio was most strongly influenced by the shape of the relationship between intake rate and prey density - the functional response - and, when interference competition occurred, by the distribution of the birds’ main food supply. Simulations with realistic spatial distributions of prey predicted that the minimum required amount of food per bird would be between two and five times the amount actually consumed. The threshold approach could provide a simple method of monitoring estuary quality based on food supply and bird numbers. It also provides a potentially clearly-defined and unambiguous measure of the carrying capacity of a site. If applied to a sufficient number of real estuaries, general guidelines for maintaining estuary quality based on estuary characteristics, food supply and bird species might be established.     

Watershed risk analysis model for TVA's Holston River basin

The Electric Power Research Institute has launched a research project to develop a conceptual risk analysis framework for watershed management of point and nonpoint source pollution. The research leads to the design of an engineering model to 1) process and translate water quality data (coliform, HOD, DO, suspended solids, temperature, sediment, etc.) into decision variables (suitability for water contact sports and swimming, fish spawning fish survival, human consumption of fish, and freedom from algal nuisance, etc.) and 2) predict water quality improvements from proposed management alternatives. Actual development of the model is being carried out with the Tennessee Valley Authority (TVA) for the Holston River watershed.The effort includes model construction by importation of GIS map files, stringing together existing watershed and reservoir models, calibration of the model, and selection of decision variables and water quality check points. The model calculates hydrology, waste load, water quality and suitability of fish habitats at headwaters. The base case results and improvements after best management alternatives will be compared to the data observed by TVA's River Action Team. The final product will be a user friendly tool that stakeholders can use to find a cost effective method of improving water quality, including market-based pollution trading.     

放牧强度对青藏高原高寒矮嵩草草甸氧化亚氮释放的影响

依托青藏高原东北隅高寒矮嵩草草甸的5a放牧强度（禁牧、轻度放牧、中度放牧、重度放牧）试验平台,2016年在植物生长季的6-9月,基于静态暗箱-气相色谱法,测定N2O的释放特征及相应的环境、生物因子,探讨放牧强度对高寒草甸N2O释放特征的影响及其内在环境生物驱动机制。结果表明：环境、生物因子中仅表层土壤容积含水量、土壤容重及土壤有机碳含量对放牧强度响应显著（P＜0.05）。高寒草甸N2O释放的季节特征表现出生长季的早期和晚期相对较高的“U”型趋势。禁牧样地N2O释放速率最小,极显著（P＜0.01）低于其它3个放牧样地。高寒草甸N2O释放强度与放牧强度间表现出正相关趋势（R= 0.49, P＜0.01）。相关分析表明,表层土壤温度是高寒草甸N2O释放速率的主要影响因子,但放牧强度改变了土壤温度的影响程度。中短期放牧管理改变了高寒草甸植被生长季N2O释放速率,但未改变其释放的季节特征。禁牧管理提高了土壤温度,进而显著降低植被生长季N2O释放强度。     

The Dynamics of Suspended Sediment Transport in the Ribble Estuary

Velocity and turbidity were measured over a tidal cycle during both spring and neap tides in the Ribble estuary England. The data was analysed to determine the relative magnitudes of the various components of the residual circulation and sediment flux. The Lagrangian residual circulation was found to be dominated by the influence of freshwater input to the estuary the landward directed component of the circulation due to the Stokes drift being cancelled by the Eulerian flow induced by set-upThe dominant driving mechanism of the residual flux of suspended sediment was found to vary both spatially and over the spring-neap cycle. During the neap tide the flux in the mid estuary was negligable, however, during the spring tide landward transport of sediment by the mechanism of tidal pumping was found to be the dominant mechanism.