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1.
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. 相似文献
2.
The water quality of an urban pond in the thickly populated area of Varanasi city (5 km apart) was studied and compared with a rural pond in the Banaras Hindu University campus for transparency, conductivity and nutrient richness (Cl?, SO, PO? P, NO? N, organic carbon, Ca2+, Mg2+, K+, Na+) at three depths (surface, 1.5 m, 3 m) at monthly intervals between February 1982 and February 1983. This was done to assess the effects of urban surroundings of a very ancient city sector on pond water quality in reference to that of a rural pond. The rural pond had a lush growth of 12 macrophytic species, whereas the urban one had only such a growth with many phytoplanktonic species. Transparency was maximum in the winter season and the rural pond water was more transparent, while the electrolytical conductance was maximum in the rainy season, being higher in the urban pond. Electrolytical conductivity was negatively correlated to transparency: urban: EC = 1081.612–6.575 T, r2 = 0.897, F1,11 = 96, P <0.005; rural: EC = 728.981–4.328 T, r2 = 0.892, F1,11 = 91, P <0.005. Chloride and sulphate concentrations were highest in summer months, but the former was much higher in the urban pond while the latter in the rural pond. NO3–N was highest in the rainy season in the rural pond and in early winter in the urban one and showed a definite trend with change in depth. PO4–P also varied with depth and time and it was higher in late summer and the early rainy season in the rural pond and in early winter in the urban pond. But both these nutrients were much higher in the urban pond. The maximum organic carbon concentration was found in the rainy season in the rural pond and in summer months in the urban pond. The variation of organic carbon with depth was distinct. Both summer and winter seasons showed almost similar values of calcium concentration in the rural pond, but in the urban pond it was maximum in summer. Organic carbon and calcium were higher in the urban pond. The magnesium concentration was highest in rainy months in both the ponds, but the periodicity of the minimum differed. The distribution of calcium with depth was not well defined. The highest concentration of potassium was found in the winter season in both the ponds. The sodium concentration in the rural pond was observed maximum in summer and minimum in the rainy season, but in the urban pond the trend was different. The variation of potassium and sodium with depth was not well defined. Magnesium and sodium were also higher in the urban pond but potassium was almost at the same concentration in both the ponds. The effect of urbanisation may be one of the factors which might be responsible to the shift of the species composition towards phytoplanktonic flora. 相似文献
3.
Understanding the influence of complex interactions among hydrological factors, soil characteristics and biogeochemical functions on nutrient dynamics in overland flow is important for efficiently managing agricultural nonpoint pollution. Experiments were conducted to assess nutrient export from Ultisol soils in the Sunjia catchment, Jiangxi province, southern China, between 2003 and 2005. Four plots were divided into two groups: two peanut plots and two agroforestry (peanut intercropped with citrus) plots. During the study period, we collected water samples for chemical analyses after each rainfall event that generated overland flow to assess nutrient export dynamics. The concentrations of potassium (K) and nitrate‐N (NO3––N) in overland flow were higher during the wetting season (winter and early spring). This reflects the solubility of K and NO3––N, the accumulation of NO3––N during the dry season and an increase in desorption processes and mixing with pre‐event water caused by prolonged contact with soil in areas with long‐duration, low‐intensity rainfall. In contrast, concentrations of total nitrogen (TN) and total phosphorus (TP) were higher during the wet season (late March to early July) and during the dry season (mid‐July to the end of September or early October). This was due to the interaction between specific hydrological regimes, the properties of the Ultisol and particulate transport processes. Variations in nutrient concentrations during storm events further identified that event water was the dominant source of total nitrogen and total phosphorus, and pre‐event water was the dominant source of NO3––N. In addition, the results obtained for the different land uses suggest that agroforestry practices reduce nutrient loss via overland flow. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
4.
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。 相似文献
5.
藻类是湖泊生态系统中重要的初级生产者,物种多样性高且对水环境变化敏感,其生产力水平与群落构建模式是反映湖泊环境梯度和生态系统特征的可靠指标。其中硅藻优势属种的演替模式及其环境条件识别,是开展湖泊生态健康和环境质量评价的重要内容。本文选择亚热带地区浅水湖泊异龙湖开展季节调查,对20个采样点的叶绿素a和硅藻群落组成等指标开展分布特征及其驱动因子的定量评价,系统分析藻类变化的时空模式、驱动因子及其指标异同。2020年12月一2021年9月,异龙湖水环境特征的季节波动明显,综合营养指数TSI平均为74.76,总体处于富营养水平。在80个水体样品中共发现硅藻21属68种,群落结构以浮游类型(平均占比79.33%±20.69%)的耐中富营养种为主;在4个季节的调查中,膜糊直链藻Aulacoseira ambigua(61.62%±20.26%)为优势种。主成分分析显示,硅藻群落组成存在明显的空间差异和季节变化。冗余分析和方差分解等结果表明,水体营养因子(TN、TP和N:P)是影响叶绿素a浓度空间变化的重要因子(解释方差为19.08%±11.4%),水温和水深梯度的影响较小(9.63%±11.31%... 相似文献
6.
为了研究太湖底栖动物优势种类——霍甫水丝蚓(Limnodrilus hoffmeisteri)对于湖泊富营养化的影响,以温度和密度为模拟控制条件,对太湖霍甫水丝蚓进行营养盐释放的室内控制实验,研究温度和密度的变化对霍甫水丝蚓NH_4~+-N和PO_4~(3-)-P释放率的影响,根据霍甫水丝蚓铵态氮(NH_4~+-N)和磷酸盐(PO_4~(3-)-P)释放率与温度的关系方程,结合太湖霍甫水丝蚓2007-2010年的生物量估算其对太湖水体氮磷的潜在贡献.结果表明,随温度升高太湖霍甫水丝蚓NH_4~+-N和PO_4~(3-)-P的释放率均呈现逐渐升高的趋势,而密度变化对霍甫水丝蚓NH_4~+-N和PO_4~(3-)-P释放率的影响均不显著,太湖霍甫水丝蚓NH_4~+-N和PO_4~(3-)-P年平均释放量分别为1925.5和210.0 t,分别可达到全太湖沉积物-水界面NH_4~+-N和PO_4~(3-)-P的年净通量的19.3%和23.3%,表明霍甫水丝蚓的营养盐释放对于湖泊生物地化循环和湖泊富营养化具有显著的影响. 相似文献
7.
The system consists of three preliminary clarifiers and two ponds operating in series. It drains 100,000 to 120,000 m3 highly loaded wastewater per year over the ground. In dependence on load, in the pond 1 a midsummer-time bacterial maximum of up to 800 m3/l occurs. The algal biomass, too, shows an annual curve with one peak; the maximum is independent of the ice cover and varies with the seasons. The BOD5 shows a spring maximum and a summer maximum independent of the biomasses and their variations. In the second pond only slight changes are found from June till October; here prevail algae and a maximum of flagellates. Although a stage of filtrators and consumers is lacking, the system can be regarded as a sewage pond system with a reduction of BOD5 by 73%. 相似文献
8.
Characterization of tidally influenced seasonal nutrient flux to the Bay of Bengal and its implications on the coastal ecosystem 
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下载免费PDF全文 Submarine groundwater discharge (SGD) introduces solute and nutrients to the global oceans, resulting in considerable nutrient cycling and dynamics in the coastal areas. We have conducted high‐resolution, spatio‐temporal, lunar tidal cycle patterns and variability of discharged solute/nutrient assessment to get an overview of seasonal nutrient flux to the Bay of Bengal in eastern parts of the Indian subcontinent. Whereas the premonsoon season SGD was found to be dominant in the marine influence (M‐SGD), the postmonsoon season was found to be predominated by the terrestrial component of SGD (T‐SGD), extending from coast to near offshore. The solute fluxes and redox transformation were found to be extensively influenced by tidal and diurnal cycles, overlapping on seasonal patterns. We have assessed the possible role of SGD‐associated solute/nutrient fluxes and their discharge mechanisms, and their associated temporal distributions have severe implications on the biological productivity of the Bay of Bengal. The estimated annual solute fluxes, using the average end‐member concentration of the SGD‐associated nutrients, were found to be 240 and 224 mM·m?2·day?1 for NO3? and Fetot, respectively. Together with huge freshwater flux from the Himalayan and Peninsular Indian rivers, the SGD has considerable influence on the bay water circulation, stratification, and solute cycling. Thus, the observation from this study implies that SGD‐associated nutrient flux to the Bay of Bengal may function as a nutrient sink, which might influence the long‐term solute/nutrient flux along the eastern coast of India. 相似文献
9.
Elżbieta Zębek 《Water Resources》2014,41(5):583-591
The study of seasonal dynamics of net phytoplankton was carried out above and below the hydroelectric plant (HP) on the Pas ka River. Correlations were found between the abundance of diatoms and conductivity, O2, PO4; the abundance of cyanobacteria and water temperature and conductivity, and the abundance of chlorophytes and O2 and Ntot. Multiple correlations revealed the most significant factor for diatom development is PO4, for cyanobacteria is water temperature, and for chlorophytes is Ntot. A lower abundance and biomass of phytoplankton, and less species diversity and nutrient concentrations were registered below the HP than above it. The seasonal dynamics of phytoplankton abundance provided similar results. The maximum biomass of the assemblage was found earlier below the HP, in April, than above it, in May. However, no differences were recorded in the dominant species within phytoplankton abundance. The phytoplankton biomass was dominated by the Melosira varians and Spirogyra sp., which are typical taxa of plant periphyton and possibly emanate from the concrete elements of the dam. This HP changed the local hydrological and environmental conditions, affecting available nutrients, and thereby phytoplankton development in the vegetative season. 相似文献
10.
Riparian zones are highly-dynamic transition zones between surface water (SW) and groundwater (GW) and function as key biogeochemical-reactors for solutes transitioning between both compartments. Infiltration of SW rich in dissolved oxygen (DO) into the riparian aquifer can supress removal processes of redox sensitive compounds like NO3−, a nutrient harmful for the aquatic ecosystem at high concentrations. Seasonal and short-term variations of temperature and hydrologic conditions can influence biogeochemical reaction rates and thus the prevailing redox conditions in the riparian zone. We combined GW tracer-tests and a 1-year high-frequency dataset of DO with data-driven simulations of DO consumption to assess the effects of seasonal and event-scale variations in temperature and transit-times on the reactive transport of DO. Damköhler numbers for DO consumption (DADO) were used to characterize the system in terms of DO turnover potential. Our results suggest that seasonal and short-term variations in temperature are major controls for DO turnover and the resulting concentrations at our field site, while transit-times are of minor importance. Seasonal variations of temperature in GW lead to shifts from transport-limited (DADO > 1) to reaction-limited conditions (DADO < 1), while short-term events were found to have minor impacts on the state of the system, only resulting in slightly less transport-limited conditions due to decreasing temperature and transit-times. The data-driven analyses show that assuming constant water temperature along a flowpath can lead to an over- or underestimation of reaction rates by a factor of 2–3 due to different infiltrating water temperature at the SW–GW interface, whereas the assumption of constant transit-times results in incorrect estimates of NO3− removal potential based on DADO approach (40%–50% difference). 相似文献
11.
随着我国湖泊治理力度的加大,太湖和巢湖的营养盐水平,特别是氮水平近年来明显下降,如2007年以后太湖总氮和近年来巢湖的氨氮水平都呈现下降趋势,但是2个湖泊水华蓝藻的优势种却向相反的方向演化,太湖的长孢藻(Dolichospermum)比例在增加,而巢湖的长孢藻比例却在降低,为阐明这种变化过程和驱动因素,本研究利用太湖(19932015年)和巢湖(2012 2018年)的历史数据分析了2个湖泊中的水华蓝藻——微囊藻(Microcystis)和长孢藻生物量的历史变化过程,并结合营养盐数据分析了影响2种水华蓝藻变动的驱动因素.结果显示:太湖和巢湖的微囊藻生物量多年来始终保持高位波动,近年来均有升高的趋势,这与2个湖泊磷的高位波动具有明显的相关性,磷是决定微囊藻生物量长尺度变化的主要驱动因素;太湖的长孢藻生物量呈现较大波动变化,2007年以后明显升高,巢湖的长孢藻生物量则明显下降,氮与长孢藻生物量呈现负相关关系,而且这种负相关仅在低磷浓度时具有显著性.微囊藻生物量对磷浓度变化敏感的正反馈响应是其水华形成的重要机制之一,在高温高磷条件下,微囊藻可以快速繁殖,并竞争性排除长孢藻,从而形成优势;而长孢藻可以通过温度生态位和固氮两种方式占据优势,在氮浓度相对较低,且温度低于微囊藻形成水华的温度范围时,长孢藻可以依靠温度生态位的优势形成水华,而在氮限制的条件下,即使在夏季高温时,长孢藻依然可以利用固氮作用形成水华,但是关键的温度阈值和开始固氮的氮浓度阈值仍不清楚.基于2种水华蓝藻对营养盐变化响应的差异,建议在进行蓝藻水华治理、污染削减过程中,应针对不同水华蓝藻的特性进行分时段分类别的营养盐控制策略. 相似文献
12.
Bla?enka Gašparovi? Tamara DjakovacNataša Tepi? Danilo Degobbis 《Continental Shelf Research》2011,31(10):1149-1160
Surface-active organic substances (SAS), nutrients, chlorophyll a (Chl a), dissolved oxygen (O2), salinity (S) and temperature (T) were measured approximately monthly in the northern Adriatic Sea (NA) during two years. Results were elaborated for two stations of different trophic status. Exhaustive statistical examinations of measured variables were performed to contribute to better understanding of the processes and interdependence of the measured parameters. The results of those analyses allowed the region to be described based on several groups of data relevant for particular processes. Chl a appear to be independent parameter; orthosilicate, nitrite and ammonium represent the parameter group most relevant for regeneration processes; the second group includes nutrients dominant in freshwater inputs (orthophosphate and nitrate), while in the third group are parameters related to primary production processes (T, O2, organic phosphorus and SAS). Probably due to time lags between nutrient uptake and phytoplankton growth as well as between cells growth/division and SAS release, both, the correlation between nutrients and Chl a and the correlation between Chl a and SAS were not statistically significant. Although significantly higher nutrient and Chl a concentrations were found in the mesotrophic western part of the region in comparison to the oligotrophic eastern part, the SAS concentration differences were less marked. It is assumed that more OM is produced, but also at the same time remineralized, at the mesotrophic western part, leading to higher concentrations of regenerated nutrients there. Presence of different phytoplankton taxa and/or fractions (micro and nano) at the two stations may have also contributed to minimize the difference in SAS contents. Higher SAS acidities were noticed in the mesotrophic than in the oligotrophic part. 相似文献
13.
Transport of nitrogen in soil water following the application of animal manures to sloping grassland
Abstract A field experiment was conducted on a sloping grassland soil in southwest England to investigate the downslope transport of nitrogen in soil water following the application of cattle manure, slurry and inorganic fertilizer. Transport of nitrogen (N) species was monitored on hydrologically isolated plots. Manure (50 t ha?1), slurry (50 m3 ha?1) and fertilizer (250 kg N ha?1) were applied in February/March 1992. Subsurface water movement, by both matrix and preferential flow, was the dominant flow route during the experiment. Subsurface and surface nutrient flow pathways were monitored by analysing soil water and surface runoff for NO3-N, NH4-N and total N. Subsurface flow chemistry was dominated by NO3-N, with concentrations usually between 2 and 5 mg NO3 ?N dm?3. Differences between fertilizer and manure treatments and the untreated control were not significant. Significantly elevated NO3-N concentrations were observed in soil water in the buffer zone, indicating the importance of a buffer zone at least 10 m wide between manure spreading zones and an adjacent water course. 相似文献
14.
Dimethyl Sulfoxide Reduction Method for the Characterization of Biomass Activity in Sludge of an Aerated Lagoon The microbial biomass activity was studied in sludge from a wastewater lagoon (Hatzbachtal) which consisted of 4 aerated ponds and one polishing pond. The lagoon was characterized by low BOD5 loading and high dilution because of water from the surroundings. Sludge samples were taken from 4 sampling sites of each aerated pond and from one site of the polishing pond. The biomass activity in the sludge samples was analysed with the help of dimethyl sulfoxide reductase (DRA) and dehydrogenase (DHA) activity. In addition, Corg-content was also determined. The effect of different reaction parameters on the DRA was studied in relation to incubation period, temperature and atmosphere as well as sludge weight and pH value. The results presented here show that a linear increase in the DRA occured for the sludge weight ranging from 0.1 to 0.5 g, incubation period from 0.5 to 11 h and incubation temperature from 20 to 50 °C. The pH spectrum from acidic to neutral did not effect the DMS formation in sludge. Although the values for DRA were always higher in anaerobic incubation of sludge than in aerobic incubation, the courses of the DRA in both conditions were parallel. Comparing the biomass activity in sludge from different sampling sites of the aerated ponds, the average Corg-content was found to be reflected by the DRA and DHA. Further, the variation in the DRA could represent also the influence of oxygen concentration. Therefore, a reduction in biomass activities indicated a decline in the availability of oxygen. 相似文献
15.
Combining physical-based models and satellite images for the spatio-temporal assessment of soil infiltration capacity 总被引：1，自引：1，他引：0
Daniele Pedretti Daniel Fern��ndez-Garcia Xavier Sanchez-Vila Marco Barahona-Palomo Diogo Bolster 《Stochastic Environmental Research and Risk Assessment (SERRA)》2011,25(8):1065-1075
The performance of managed artificial recharge (MAR) facilities by means of surface ponds (SP) is controlled by the temporal
evolution of the global infiltration capacity I
c
of topsoils. Cost-effective maintenance operations that aim to maintain controlled infiltration values during the activity
of the SP require the full knowledge of the spatio-temporal variability of I
c
. This task is deemed uncertain. The natural reduction in time of I
c
depends on complex physical, biological and chemical reactions that clog the soil pores and has been observed to decay exponentially
to an asymptotic non-zero value. Moreover, the relative influence of single clogging processes depend on some initial parameters
of the soil, such as the initial infiltration capacity (I
c,0). This property is also uncertain, as aquifers are typically heterogeneous and scarcely characterized in practical situations.
We suggest a method to obtain maps of I
c
using a geostatistical approach, which is suitable to be extended to engineering risk assessment concerning management of
SP facilities. We propose to combine geostatistical inference and a temporally-lumped physical model to reproduce non-uniform
clogging in topsoils of a SP, using field campaigns of local and large scale tests and additionally by means of satellite
images as secondary information. We then postulate a power-law relationship between the parameter of the exponential law,
λ, and I
c,0. It is found that calibrating the two parameters of the power law model it is possible to fit the temporal evolution of total
infiltration rate at the pond scale in a MAR test facility. The results can be used to design appropriate measures to selectively
limit clogging during operation, extending the life of the infiltration pond. 相似文献
16.
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. 相似文献
17.
Klemens Hocke 《Annales Geophysicae》1996,14(2):201-210
During the MLTCS (Mesosphere-Lower Thermosphere Coupling Study) campaign the EISCAT UHF radar was continuously operated over 7 days (30 July-5 August 1992) in the CP-1 mode. The long time series obtained of the fundamental ionospheric parameters field-aligned ion velocity (Vi), ion and electron temperature (T and Te), and electron density (Ne) are useful in investigating tidal variations in the E- and F-region since the geomagnetic activity was particularly low during the time of measurement. Maximum entropy spectra of the parameters were calculated for the relatively quiet interval from 1 August to 4 August 1992 and indicated dominant variations with harmonics of 24 hours. In the electron density spectrum especially, harmonics up to the sixth order (4-h period) are clearly visible. The phase and amplitude height profiles (100-450 km) of the diurnal, semidiurnal, and terdiurnal variations were determined by Fourier transform for a 24-h data set beginning at 12:00 UT on 3 August 1992 when the contaminating influences of electric fields were negligible. The tidal variations of the ion temperatures are compared with the corresponding variations of the neutral temperature predicted by the MSISE-90 model. A remarkable result is the dominance of terdiurnal temperature oscillations at E-region heights on 3–4 August 1992, while the measured diurnal and semidiurnal variations were negligible. The finding was confirmed by the analysis of further EISCAT data (2-3 August 1989, 2–3 July 1990, 31 March- 1 April 1992) which also showed a dominant terdiurnal temperature tide in the E-region. This is different from numerous observations of tides in the E-region at mid-latitudes where the diurnal and especially the semidiurnal temperature oscillations were dominant. 相似文献
18.
寡—中营养型水体中,虽然营养盐水平偏低,但仍会偶发性出现较为严重的蓝藻水华现象,其具体机制仍有待深入探索研究. 本研究以偶发水华水体方便水库为例,通过历史数据分析和调查研究,探讨了其水华蓝藻的优势类群,并分析了蓝藻水华形成的主要驱动因素. 研究发现：方便水库优势的水华蓝藻为浮丝藻和长孢藻,这两种丝状蓝藻是发生偶发性蓝藻水华的潜在风险物种,其中浮丝藻的发生风险最高,风险时段为7—9月. 方便水库多年来营养盐浓度呈现下降的趋势,其中总氮浓度的下降趋势快于总磷浓度,整体有利于蓝藻水华的防控,但是营养盐的波动,尤其是随着降雨导致的地表径流入库对水体总磷的脉冲式补充,降低了水体氮磷比,增加了水库偶发蓝藻水华的风险; 在营养盐满足的条件下,水温、高锰酸盐指数和氧化还原电位是发生浮丝藻水华的主要驱动因素,氧化还原电位、水温和透明度是发生长孢藻水华的主要驱动因素. 本研究结果有助于提升对偶发性蓝藻水华机制的认识和应急处置工作的精准性. 相似文献
19.
Entrapped biogenic gas in peat can greatly affect peatland biogeochemical and hydrological processes by altering volumetric water content, peat buoyancy, and ‘saturated’ hydraulic conductivity, and by generating over‐pressure zones. These over‐pressure zones further affect hydraulic gradients which influence water and nutrient flow direction and rate. The dynamics of entrapped gas are of global interest because the loss of this gas to the atmosphere via ebullition (bubbling) is likely the dominant transport mechanism of methane (CH4) to the atmosphere from peatlands, which are the largest natural terrestrial source per annum of atmospheric CH4. We investigated the relationship between atmospheric pressure and temperature on volumetric gas content (VGC) and CH4 ebullition using a laboratory peat core incubation experiment. Peat cores were incubated at three temperatures (one core at 4 °C, three cores at 11 °C, and one core at 20 °C) in sealed PVC cylinders, instrumented to measure VGC, pore‐water CH4 concentrations, and ebullition (volume and CH4 concentrations). Ebullition events primarily occurred (71% of the time) during periods of falling atmospheric pressure. The duration of the drop in atmospheric pressure had a larger control on ebullition volume than the magnitude of the drop. VGC in the 20 °C core increased from the onset of the experiment and reached a fluctuating but time‐averaged constant level between experiment day 30 and 115. The change in VGC was low for the 11 °C cores for the initial period of the experiment but showed large increases when the growth chamber temperature increased to 20 °C due to a malfunction. The core maintained at 4 °C showed only a small increase in entrapped gas content throughout the experiment. The 20 °C core showed the largest increase in VGC. The increases in VGC occurred despite pore‐water concentrations of CH4 being below the equilibrium solubility level. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
20.
《Limnologica》2015
Thirty kettle hole ponds located in agricultural landscape of western Poland were studied with respect to physico-chemical (temperature and pH) and chemical (SC, dissolved oxygen, concentration of nutrients) variables of surface water quality during two subsequent years. Most of the ponds selected for the study host populations of endangered large branchiopod crustaceans, thus the aim of the study was to find out the rules governing these ecosystems and infer the best ways to protect them. Precipitation during the first year of the study was close to the average for the region, whereas severe drought was recorded during the second year. The influence of water regime, morphological parameters, catchment characteristics and vegetation on the parameters of water (pH, conductivity, contents of O2, N-NH4, N-NO2, N-NO3, SRP and TP) separately for both years was tested using redundancy analyses (RDA). The results showed that the factors significantly explaining the variance in water chemistry differed between years of the study. In the year of average precipitation, the most important factors were related to the morphology of the pond and its catchment. In contrast, under drought conditions the factors connected with pond vegetation and water depth were significant. However, in general, hydroperiod length of the pond was the most important factor, significant in all the models created. 相似文献