Natural Water Level Research Articles

The level of water in the river flowing through the breeding site shapes the body condition of a lekking bird\u2014the Great Snipe Gallinago media

The display of lekking Great Snipe males is an energetically demanding activity and therefore, access to the rich feeding sites in the proximity of their leks is essential. During the breeding season, Great Snipes mostly prey on earthworms, whose availability is affected by moisture and penetrability of the soil. In this study, we investigated the relation between the body condition of displaying Great Snipe males and the water level of the river flowing through their breeding grounds, which can affect soil characteristics. We found that the body condition of males decreased over the course of the lekking period in May, showing the great energetic expenditure of their advertising display in courtship. The high water level in the river resulted in the increase in body condition of birds, probably due to improved prey availability, as earthworms moved closer to the ground surface in search of optimal conditions. Further rise in the water level caused flooding of the meadow and a decrease in the body condition of lekking Great Snipes, possibly because of the deterioration of feeding condition, as earthworms tend to leave flooded areas. Moreover, as the flooded area enlarged, the floodplain became inaccessible for foraging Great Snipes, due to their relatively short legs restricting them from wading in deep water. Our results show that for the lowland leks of the Great Snipe to be preserved it is advisable to allow for the natural water level fluctuations in the river shaping the hydrological conditions of the floodplains.

Assessment of the Ecological Risk from Heavy Metals in the Surface Sediment of River Surma, Bangladesh: Coupled Approach of Monte Carlo Simulation and Multi-Component Statistical Analysis

River sediment can be used to measure the pollution level in natural water, as it serves as one of the vital environmental indicators. This study aims to assess heavy metal pollution namely Copper (Cu), Iron (Fe), Manganese (Mn), Zinc (Zn), Nickel (Ni), Lead (Pb), and Cadmium (Cd) in Surma River. Further, it compares potential ecological risk index values using Hakanson Risk Index (RI) and Monte Carlo Simulation (MCS) approach to evaluate the environmental risks caused by these heavy metals. in the study area. With obtained results, enrichment of individual heavy metals in the study area was found in the order of Ni > Pb > Cd > Mn > Cu > Zn. Also, variance in MCS index contributed by studied metals was in the order of Cd > Pb > Ni > Zn > Cu. None of the heavy metals, except Ni, showed moderate contamination of the sediment. Risk index values from RI and MCS provide valuable insights in the contamination profile of the river, indicating the studied river is currently under low ecological risk for the studied heavy metals. This study can be utilized to assess the susceptibility of the river sediment to heavy metal pollution near an urban core, and to have a better understanding of the contamination profile of a river.

Elucidation of the stoichiometry of Fe(III) and Fe(II) complexes formed with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP). Application to Fe(III) and Fe(II) Electrochemical Determination at Trace Level in Natural Water

Elucidation of the stoichiometry of Fe(III) and Fe(II) complexes formed with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP). Application to Fe(III) and Fe(II) Electrochemical Determination at Trace Level in Natural Water

Optimum ecological water level of water-carrying lake based on the relationship between water quality and water level

适宜的生态水位能够反映湖区生态系统的多种需求，是湖泊长期稳定健康运转的基本保障. 目前湖泊适宜生态水位的推求大多侧重恢复天然水位情势. 然而过水型湖泊承担着防洪、供水、航运等多种功能，频繁的人类活动导致湖泊水位情势异常复杂. 同时随着社会经济的快速发展，水质恶化对过水型湖泊生态系统造成了较大的负面影响，仅恢复天然水位情势难以反映过水型湖泊的生态需求. 因此，在IHA-RVA法的基础上，本文针对过水型湖泊吞吐性强的特点，利用水质-水位二元响应关系系统地提出了一套逐月修正过水型湖泊适宜生态水位阈值，并确定适宜水位变动率的方法. 以洪泽湖为应用实例，结果表明：1)根据湖泊水文情势和入湖污染物变化情况，湖泊调度周期可以划分为平水期(1—4月)、泄水期(5—6月)、蓄水前期(7—9月)和蓄水后期(10—12月)；2)各时期内，洪泽湖水位和水质呈现较强的相关性，其中平水期、泄水期和蓄水后期水质均随着水位上升而下降，平均Pearson系数达-0.77，仅在蓄水前期水质随水位上升而改善；3)现阶段洪泽湖的自净能力和污染物滞留比例竞争关系激烈，逐月适宜生态水位阈值为：12.92~12.99、12.79~12.99、12.84~12.99、12.86~12.99、12.71~12.89、12.39~12.63、11.97~12.93、12.50~13.07、12.65~13.26、12.90~13.04、12.90~13.04、12.90~13.04 m，除蓄水前期外，基于水位水质关系修正的适宜生态水位范围较IHA-RVA法计算的天然水位范围缩小了73.4 %. 总体而言，基于本文方法设计的湖泊适宜生态水位不仅可以满足生态系统对于水体大小的需求，一定程度上也可以体现湖泊生态系统对于水质的要求，为洪泽湖等过水型湖泊的生态调度、水资源管理提供科学依据.;The optimum ecological water level (OWL) guarantees stable and healthy operation of the lake in the long term by meeting various needs of the lake ecosystem. Previous studies on OWL mainly focused on restoring natural water level regime. However, water-carrying lakes have complicated water lever regimes resulted from flood control, water supply, shipping and other functions. Meanwhile, the water quality was further deteriorated due to rapid economic development. Consequently, the previous methods could not meet all the ecological needs of water-carrying lakes. Basing on IHA (indicators of hydrological alteration)-RVA (range of variability approach) method and relationship between water quality and water level, this paper proposed a method for identifying of the threshold of monthly OWL and determining the OWL variation of water-carrying lake. Taking Lake Hongze as an example, the results indicate that: 1) The lake regulation cycle can be divided into flat period (January-April), discharge period (May-June), early storage period (July-September) and late storage period (October-December) from the angle of hydrological regime and pollution into the lake. 2) There's a strong correlation between water quality and water level in each period as water quality improves with water level rising during the early storage period and deteriorates in other periods (Pearson coefficient was -0.77). 3) Due to the competition between the lake's self-purification capacity and pollutant retention ratio, the monthly OWL threshold from January to December is: 12.92-12.99, 12.79-12.99, 12.84-12.99, 12.86-12.99, 12.71-12.89, 12.39-12.63, 11.97-12.93, 12.50-13.07, 12.65-13.26, 12.90-13.04, 12.90-13.04, 12.90-13.04 m, respectively. The range of OWL modified by the relationship between water level and water quality is reduced by 73.4 % compared with the results of IHA-RVA method except in the early storage period. In general, the OWL designed by methods in this paper can reflect the requirements of lake ecosystem for water quantity and water quality to a certain extent, and provide scientific basis for the ecological regulation and water resource management of Lake Hongze and other water-carrying lakes.

Air Warming and Drainage Influences Soil Microarthropod Communities

The degradation of wetlands due to climate change is of critical concern to human beings worldwide. Little is known about the potential synergistic effects of simultaneous water level reduction and warming on the underground wetland ecosystems. We conducted a 5-month field experiment in the Sanjiang Plain, utilizing open-top chambers and water level automatic control systems to investigate such synergistic effects. Soil springtails (Collembola) and mites (Acari) in the top (0–20 cm) soil layers were sampled to calculate their density, diversity, and to screen for indicator species. Warming significantly influenced soil springtail communities, slightly increasing the total density and total abundance under the natural water level while reducing them under a constant water level. In addition, Anurida maritima and Vertagopus laricis, two indicators for the natural water level, had the highest densities in the natural water level treatment and under the combined treatment of warming and natural water level, respectively. Cheiroseius sinicus and Malaconothrus tardus had the highest densities in warming under the 0 cm water level, significantly higher than the other three treatments. This study also revealed the importance of maintaining fluctuating water levels for microarthropod communities influenced by global warming, providing a theoretical basis for water level control in wetland restoration.

Biogeochemistry of Mediterranean Wetlands: A Review about the Effects of Water-Level Fluctuations on Phosphorus Cycling and Greenhouse Gas Emissions

Although Mediterranean wetlands are characterized by extreme natural water level fluctuations in response to irregular precipitation patterns, global climate change is expected to amplify this pattern by shortening precipitation seasons and increasing the incidence of summer droughts in this area. As a consequence, a part of the lake sediment will be exposed to air-drying in dry years when the water table becomes low. This periodic sediment exposure to dry/wet cycles will likely affect biogeochemical processes. Unexpectedly, to date, few studies are focused on assessing the effects of water level fluctuations on the biogeochemistry of these ecosystems. In this review, we investigate the potential impacts of water level fluctuations on phosphorus dynamics and on greenhouse gases emissions in Mediterranean wetlands. Major drivers of global change, and specially water level fluctuations, will lead to the degradation of water quality in Mediterranean wetlands by increasing the availability of phosphorus concentration in the water column upon rewetting of dry sediment. CO2 fluxes are likely to be enhanced during desiccation, while inundation is likely to decrease cumulative CO2 emissions, as well as N2O emissions, although increasing CH4 emissions. However, there exists a complete gap of knowledge about the net effect of water level fluctuations induced by global change on greenhouse gases emission. Accordingly, further research is needed to assess whether the periodic exposure to dry–wet cycles, considering the extent and frequency of the cycles, will amplify the role of these especial ecosystems as a source of these gases and thereby act as a feedback mechanism for global warming. To conclude, it is pertinent to consider that a better understanding about the effect of water level fluctuations on the biogeochemistry of Mediterranean wetlands will help to predict how other freshwater ecosystems will respond.

Theoretical evaluation of calibration factor for CR-39 track detector for alpha radioactivity measurement in natural water

A simple track-etch method by using CR-39 detectors has been developed for determining the total alpha radioactivity level in natural water. The detectors are immersed into water sample for alpha exposure. Alpha particles generated near the detectors create latent tracks, which are a measure for the alpha radioactivity of the sample. Calibration factor (CF) evaluation for a track detector is a part of this method. It is evaluated by considering major alpha-emitters present in natural water and taking into account the actual geometry of the set-up. The method for evaluating the CF is based upon the calculating range of alpha particles in water and the estimating effective volume of water around the detector. The evaluated CF is found to be(116.18±9.88)Bq.l−1.(tracks.cm−2.h−1)−1. This method has been used to determine the total alpha radioactivity of 52 drinking water samples collected from different tube-well and tap water points at eight districts of Indian state of West Bengal. Measured radioactivity values vary from (15.17±1.29)Bq.l−1 to (45.67±3.88)Bq.l−1 with a mean value of (27.64±2.35)Bq.l−1. These radioactivity values are compared well with the worldwide alpha activity values reported in research articles. It is observed that the measured alpha radioactivities are below the recommended reference level and hence, the drinking waters of the sampling sites are safe for consumers. The CF evaluated and the experimental method developed in the present study can also be utilized in the radioactivity research field. Data obtained in the present study may serve as a good baseline.

Scenario of radon alpha activity level in natural drinking waters of different regions of eastern part of India: A review report

Background/Objectives: High density to alpha-particle radiations, particularly from radon, can increase health risks. This study presents the radon alpha-activity of drinking waters in regions of eastern part of India. Methods/Statistical analysis: To figure out radon alpha-activity concentration in natural drinking waters in the above mentioned regions, present study reviewed many literatures that pertinent to radon alpha-activity of waters in the regions. Both inclusion and exclusion criteria have been followed to select the literatures for review. This study consulted the reports of literatures for obtaining data sources. Recommendations of national and international groups have been used to interpret the results. Findings: A wide variation of radon alphaactivity concentration in drinking water of the regions has been found in between 0:31 and 911 Bq=l. Most of the radioactivity values exceeded MCL or reference level recommended by USEPA and UNSCEAR, and few are exceeding action limit given by EU and WHO. High alpha-activity level in waters has been seen in the arsenic and fluoride contaminated areas and near the areas of U-mine and thermal springs. Low level of alpha-activity has been seen in some regions of Assam, Meghalaya, Mizoram and Orissa, and in the east coast region of West Bengal. The radon alpha-activity level in coastal area of Orissa is higher than that of West Bengal. It is found that the sources of the alphaemitting radionuclides, arsenic and fluoride may coexist in the arsenic and fluoride contaminated regions. This study is the first that reviewed the alpha contamination level in natural drinking waters in the eastern part of India. More studies on these regions are required in the future. Novelty/Applications: Novelty of this study relies on the observed alpha-activity of drinking waters in the regions. Radioactivity data provided in this study can help to researchers for further investigation. Keywords: Natural waters; Alpha emitters; Radon; Alpha activity; Human health; India

Synergy between Satellite Altimetry and Optical Water Quality Data towards Improved Estimation of Lakes Ecological Status

European countries are obligated to monitor and estimate ecological status of lakes under European Union Water Framework Directive (2000/60/EC) for sustainable lakes’ ecosystems in the future. In large and shallow lakes, physical, chemical, and biological water quality parameters are influenced by the high natural variability of water level, exceeding anthropogenic variability, and causing large uncertainty to the assessment of ecological status. Correction of metric values used for the assessment of ecological status for the effect of natural water level fluctuation reduces the signal-to-noise ratio in data and decreases the uncertainty of the status estimate. Here we have explored the potential to create synergy between optical and altimetry data for more accurate estimation of ecological status class of lakes. We have combined data from Sentinel-3 Synthetic Aperture Radar Altimeter and Cryosat-2 SAR Interferometric Radar Altimeter to derive water level estimations in order to apply corrections for chlorophyll a, phytoplankton biomass, and Secchi disc depth estimations from Sentinel-3 Ocean and Land Color Instrument data. Long-term in situ data was used to develop the methodology for the correction of water quality data for the effects of water level applicable on the satellite data. The study shows suitability and potential to combine optical and altimetry data to support in situ measurements and thereby support lake monitoring and management. Combination of two different types of satellite data from the continuous Copernicus program will advance the monitoring of lakes and improves the estimation of ecological status under European Union Water Framework Directive.

Dynamics of taxonomic and functional community structure in macrozoobenthos and the underlying driving factors in Lake Dongting during 1988 and 2016

洞庭湖是我国第二大淡水湖泊，其水文条件对湖泊湿地生态系统健康的维系发挥着不可替代的作用.近年来，水环境恶化日益威胁湖区水生态系统健康.然而，有关底栖动物水生态健康评价的研究仍然停留在物种群落结构方面，缺乏底栖动物群落功能对水污染响应的研究，尤其在较长时间尺度上.因而，本研究分析了1988—2016年近30 a来洞庭湖的水质和底栖动物群落数据，探寻底栖动物群落功能对水环境恶化的响应规律.结果表明，洞庭湖水体总氮浓度是威胁底栖动物物种和功能群落变动的主要因素.此外，不断恶化的水环境驱动底栖动物物种和功能群落结构改变，表现为敏感水生昆虫的比例下降，寡毛类、小型软体动物比例的上升，并伴随着体长为1.00~1.99 cm、背扁型、侧扁型、不移动等功能性状类别比例的下降.同时，水环境恶化降低物种丰富度、功能丰富度和劳氏二次熵多样性.基于距离的冗余分析结果显示，水体氮营养盐、重金属离子和有机污染物共同驱动底栖动物物种群落结构的变异，而营养盐类与无/有机污染物决定着其功能群落结构的变异.鉴于洞庭湖水质不断恶化的状况，本研究建议采取一系列措施，包括合理管控湖区周边废水直排入湖、取缔湖区内的非法采砂以及调控枯水季洞庭湖水位等.生物监测和评价方面，建议将底栖动物物种和功能群落一并纳入评价体系，且优先选用物种丰富度、功能丰富度和劳氏二次熵指数评估换水周期较短的大型浅水湖泊水质变化对底栖动物物种和功能多样性的影响.;Lake Dongting is the second-largest and Yangtze-connected freshwater lake in China, maintaining the wetland ecosystem health. However, in recent decades, the deterioration of water quality is increasingly threatening the lake ecosystem health. Previous studies related to the bioassessment of the aquatic ecological condition using the macrobenthic fauna focused on the effects of deterioration of water quality on the benthic natural community structures, instead of its community functioning, especially at a long time scale. Thus, the present study analyzed the water quality and macrozoobenthic faunal data of the lake in the past thirty years to detect the mechanisms of variances of functional structures underlying the deterioration of water quality. Our results showed that total nitrogen remains the main stressor affecting the changes of taxonomic and functional structures in macrobenthic fauna. In addition, degraded water environmental condition determined the changes of taxonomic and functional structures in the macrozoobenthos, showing the decreases in the proportion of sensitive aquatic insects and increases in the proportion of oligochaetes and small mollusks, accompanying by decreasing in the trait category values of 1.00-1.99 cm, dorsal flat, lateral flat, no mobility, etc. Moreover, the accumulation of aquatic pollution decreased taxa richness, functional richness, and Rao's Q diversity. Results of dbRDA showed that nitrogen, heavy metals, and inorganic/organic pollutants jointly determined the variation of macrobenthic taxonomic structure, while nitrogen and inorganic/organic pollutants dominated the variation of its functional structure. According to the deteriorated water quality of the lake, a set of measures are proposed in the present study, including treatment of domestic sewage and industrial wastewater discharged directly into the lake, banning illegal sand mining in the lake area, and maintaining the natural water level in dry season. In terms of bioassessment and monitoring, we suggest that the taxonomic and functional community structure in macrozoobenthos should be incorporated into the bioassessment framework. If assess the effects of the deteriorated water quality of large shallow lakes with short periods of water exchange on the macrozoobenthos taxonomic and functional diversity, the taxa richness, functional richness, Rao's quadratic entropy coefficient indices are recommended.

Distribution of naturally occurring uranium and other heavy toxic elements in selected spring water samples of Pithoragarh District, Uttarakhand, India

The main purpose of this study was to investigate the seasonal variation of the uranium (U) concentration level in natural drinking water. Laser fluorimetry technique has been used for the microanalysis of uranium concentration in water samples collected from different natural sources like springs and subterranean springs of various depths. A total of 23 drinking water samples were collected based on their consumption for drinking purposes from the different areas of Pithoragarh district. Seventeen physico- chemical parameters, six heavy metals and uranium were estimated in the samples. The results showed that the average value of TDS was observed 204.65 mg/L during pre- monsoon season and 213.82 mg/L during post- monsoon season, the uranium concentration in drinking water samples varied from 0.10–9.90 µg L−1 in pre-monsoon and 0.10–8.32 µg L−1 in post-monsoon seasons. The study revealed that none of the samples had exceeded the guideline values prescribed for concentration of uranium in drinking water by World Health Organization (30 µg L−1) and sources can be considered safe with respect to the level of uranium concentration.

Modeling on naturalization of inflow and outflow nutrients sources of Blue Nile River at the Lake Tana in Basaltic Plateau of Ethiopia

Lake Tana is the largest natural reservoir in Ethiopia and the head water of Abbay basin. However, after building of an irrigation weir and further lying Tunnel to Tana Belles, Lake Tana maximum amplitude of water level canges from 2.18 to 3.56 m that differ substantially in 1.38 m from amplitude of natural water level fluctuation. Understanding the natural characteristics of the Lake is important to know its water balance and for sustainable development. But it is difficult to study the natural characteristics of the Lake and its water balance using the regulated water level and outflow data sets. Thus it is evident that the regulated water level and outflow data sets have to be first naturalized before they are used for any analysis and modeling. Lake level and outflow data that have been collected since 1976 were considered to assess the regulation effect and then for naturalization. Inflows to the Lake from the main tributaries have also been collected to find if there are any correlations with either the Lake Level and/or the outflow. Regression analyses were used to develop the naturalization models. The regression analyses of flows from Gilgel Abay and Gummar with Lake Level shows that there is a very good correlation between them in different seasons. Besides, same has also been observed between Lake Level and out flow. These relationships can be used to naturalize the regulated outflow and water level.

Lanthanide rarity in natural waters: implications for microbial C1 metabolism.

Research in the last decade has illuminated the important role that lanthanides play in microbial carbon metabolism, particularly methylotrophy. Environmental omics studies have revealed that lanthoenzymes are dominant in some environments, and laboratory studies have shown that lanthoenzymes are favored over their calcium-containing counterparts even when calcium is far more abundant. Lanthanide elements are common in rocks but occur at exceedingly low levels in most natural waters (picomolar to nanomolar range) with the exception of volcanic hot springs, which can reach micromolar concentrations. Calcium is orders of magnitude higher in abundance than lanthanide elements across natural settings. Bacteria that use lanthanides for growth on simple carbon compounds (e.g. methanol and ethanol) grow optimally at micromolar concentrations. It is highly likely that bacteria in the environment have evolved specialized lanthanide sequestration and high-affinity uptake systems to overcome lanthanide deprivation. Indeed, we identified genes in soil metagenomes encoding the lanthanide-binding protein lanmodulin, which may be important for cellular differentiation between calcium and lanthanides. More research is needed on microbial adaptations to lanthanide scarcity.

Microwave assisted accelerated fluoride adsorption by porous nanohydroxyapatite

Fluoride pollution of water is a matter of concern in many countries due to its association with chronic kidney failure. Therefore, it is important to develop fast and efficient methods for fluoride removal from drinking water using environmentally friendly materials. In this article, the synthesis, characterization and microwave assisted accelerated fluoride removal by porous nanohydroxyapatite (PHAP) are reported. The PHAP samples were synthesized using polyvinyl pyrrolidone and sodium dodecyl sulphate micellar system as the template. The prepared nanohydroxyapatite was characterized using TEM, SEM, FT-IR, TGA, XRD and BET. Investigation of the morphology of microcrystals using TEM showed the presence of spherical particles of 20–35 nm size and highly porous rod-shaped crystals with the aspect ratio of 2:13. The adsorption of F− ions using PHAP was carried out under the influence of microwave radiations using concentrations comparable to existing F− levels in natural water. The equilibrium is reached within 80 s and this is the fastest saturation time recorded for any existing material. The kinetic experiments showed that the fluoride adsorption is an activated second order process. The equilibrium fluoride adsorption capacity of PHAP was found to be 9.19 mg g−1 at pH 6.5 for 80 s and this was proven to be a potential material to remove F− ions rapidly from drinking water.

Friction correlation of an offset strip fin modeled as porous medium for application to a geothermal heat exchanger

Accelerated global warming caused by the use of fossil fuels has resulted in an elevated demand for renewable energy such as geothermal energy, which exploits the constancy of ground temperature throughout the year to achieve cooling or heating. Standing-column-well geothermal systems provide high quantities of heat but are affected by decreases of the natural water level due to drought, depletion of underground water, and geographical specificities, which complicates the steady and reliable operation of these systems. To address this problem, we herein propose a novel geothermal heat exchanger equipped with an offset strip fin (OSF) and investigate OSF friction correlation modeled in terms of porous media in this heat exchanger. The reference friction factor, which is assumed to be a function of the Reynolds number (Re) and a characteristic coefficient, is calculated by computational fluid dynamics (CFD) in the Re range of 100–20,000 for a unit geothermal heat exchanger with OSFs and for 16 types of variable-dimension OSFs. The independent friction factor for these OSFs is obtained by nonlinear regression analysis. Next, by assuming that the characteristic coefficient is a function of OSF parameters, the generalized friction factor correlation for OSF is obtained by multiple regression analysis and it is verified by comparing existing friction factor correlations with the proposed values for 50 < Re < 1,000. In the case of a low (<200) Re, the maximum error is found to be 8 %, whereas in the case of a high (>500) Re, the maximum error is within 2 %, which confirms that the proposed friction factor correlation is consistent with existing data. On the other hand, the friction factor decreases with increasing OSF fin length, which is in a good agreement with the results of previous studies. In addition, the friction factor is analyzed for various working fluids (air, water, and antifreeze) by using the proposed correlation, where it is found to be independent of fluid type. The proposed friction factor correlation in the present study provides a quick assessment of calculating the pressure drop of OSF for a geothermal applications, which obviates the need for complicated and costly computational analysis.

Differences of Regulative Flexibility between Hydrological Isolated and Connected Lakes in a Large Floodplain: Insight from Inundation Dynamics and Landscape Heterogeneity

The inundation areas of floodplains are crucial to wetland ecosystems, especially in supporting biodiversity. Accurately identifying the spatial and temporal patterns of inundation areas is important for understanding floodplain ecosystem processes. Here, lakes in the Yangtze River Floodplain were divided into two types according to hydrological conditions: the natural connected lakes (Dongting Lake and Poyang Lake) with natural water level fluctuations and the isolated lakes (lakes in Jianghan Plain) with stable water levels. We established a method to identify inundation areas using multi-sources remote sensing data based on the Google Earth Engine. The dynamics of inundation areas were determined, and the relative indices were calculated in common year (2017) and a drought year (2018). The differences between the connected lakes and the isolated lakes were analyzed, and impacts of hydrological fluctuations on inundation area and habitat quality were evaluated. The results show that lakes with natural hydrological fluctuations have a greater regulative flexibility, with both patch density (PD) and submerged elasticity index (SEI) values higher than that of isolated lakes. The trend of the vegetation index in the connected lakes and in the isolated lakes is also different. The mean EVI in Dongting Lake and Poyang Lake showed a U-shaped trend which is similar to the shape of the trend of PD. The trend of mean enhanced vegetation index (EVI) in the isolated lakes is the opposite and has a lower range of variation over a year. This study provides new indicators and rapid methods for habitat quality assessment in floodplains, as well as presenting scientific information useful for improving wetland management in the middle and lower Yangtze River.

Estimating the ecological water levels of shallow lakes: a case study in Tangxun Lake, China

Water level management is an effective tool for the ecological restoration of shallow lakes. In this study, we developed an ecologically-based approach to estimate the monthly suitable ecological water levels (EWLs). This approach took both the lake topographic features and aquatic plants’ growth characteristics into account. The aquatic vegetation coverage was used to characterize the degree of the lake ecological restoration. The relationship between water level and vegetation coverage was established. We chose the Tangxun Lake as a testbed, and the recommended lowest EWL was 16.6 m, as the minimum threshold for water level regulations. The results revealed that the predicted vegetation coverage decreased with the rise of water level during the germination period (February and March). To achieve the vegetation coverage goal of 30% and 50%, the lake’s water levels must be lowered to 17.1 m and 16.8 m respectively during germination. The EWLs were recommended to be low in spring and high in summer, which was matched with the natural water level regimes. The proposed approach can provide a reliable reference for water level regulation of shallow lakes especially the lakes with insufficient data.

Do anthropogenic hydrological alterations in shallow lakes affect the dynamics of plankton?

• Plankton was affected differently by natural and anthropogenic water level changes. • Higher total plankton biomass with anthropogenic WL regulation. • Higher zooplankton species richness with anthropogenic WL regulation. • Higher phytoplankton species richness with natural WL changes. • Higher cyanobacterial microcystins concentration with anthropogenic WL regulation. Anthropogenic and natural climate-impacted water level (WL) fluctuations are one of many environmental problems affecting natural ecosystems. The aim of this study was to explain differences in the development of autotrophic and heterotrophic plankton in two shallow, temperate, embanked lakes with different modes of WL regulation. Lake Mytycze has natural WL changes supplied exclusively by precipitation; a decrease in water level was predominantly due to more evaporation than precipitation. In this lake, nutrient concentration, particulate matter, growth of toxigenic cyanobacteria and contamination with microcystins correlated positively with decreases in WL. Lake Tomaszne has anthropogenic WL regulation, elevated values of nutrients and particulate matter, but they were caused by the periodic, abrupt entrance of river waters rich in allochthonous nutrients, organic and inorganic particles. In this lake, a higher biomass of cyanobacteria was observed than in the lake with natural WL changes; the concentrations of intracellular microcystins in water correlated positively with the biomass of toxigenic species. In both lakes, decreases in the biomass of algivorous crustaceans correlated with the occurrence of cyanobacterial biomass. Biomasses of algivorous crustaceans increased abruptly when concentration of microcystins diminished below 2 μg∙dm −3 . These biomass peaks occurred due to rapid development of the cladocerans; Bosmina longirostris was found in the lake with natural WL changes and Daphnia cucullata was found in the lake with anthropogenic WL regulation. The development of predacious crustaceans was not related to the blooms of filamentous cyanobacteria or the biomass of algivorous crustaceans (as potential prey). In both lakes, Thermocyclops crassus and Mesocyclops leuckartii (Copepoda) contributed significantly to the biomass of predacious crustaceans; their abundance correlated positively with the amount of particulate matter, which was probably utilised as an alternative food source. These findings illustrate indirect influence of WL on plankton composition and biomass through alteration of environmental variables. The results indicate that the mode of WL regulation (natural vs anthropogenic) must be taken into consideration when estimating the influence of WL changes on plankton dynamics.

Automated Determination of Dissolved Reactive Phosphorus at Nanomolar to Micromolar Levels in Natural Waters Using a Portable Flow Analyzer.

Automated in-field methods for measuring dissolved reactive phosphorus (DRP) over a large concentration range are in high demand for the purpose of better understanding the biogeochemistry of phosphorus in the river-estuary-coast continuum to the open ocean. Here, an automated portable and robust analyzer was described for the determination of nanomolar to micromolar levels of DRP in natural waters. The quantification of DRP was based on classic phosphomolybdenum blue (PMB) chemistry. All the components of the analyzer were computer-controlled using LabVIEW-based laboratory-programmed software. When equipped with a 3 cm Z-type flow cell, the system demonstrated linearity with concentrations up to 12 μmol L-1, a sampling rate of 20 h-1, a limit of detection of 0.11 μmol L-1, and relative standard deviations (RSDs) of 0.4-4.6% (n = 11-576). When a solid-phase extraction cartridge was combined with the analyzer, the PMB formed from the sample was automatically concentrated on the hydrophilic-lipophilic balanced sorbent. The concentrated PMB compound was eluted with NaOH solution and measured in the spectrophotometric system. Under optimal conditions, the nanomolar-level mode afforded a sampling rate of 8 h-1, a limit of detection of 1.7 nmol L-1, and RSDs of 3.0-5.7% (n = 11-120). The system exhibited advantages that included a wide linear range, high sensitivity and reproducibility, low reagent consumption, and insignificant interference from salinity, silicate, arsenate, and other P-containing compounds. The system was successfully applied for discrete sample analysis, fixed site online monitoring, and the real-time underway measurement of DRP in riverine-estuarine-coastal waters.

Photolysis of a mixture of anthracene and benzo[a]pyrene at ultra-trace levels in natural water with disinfection purposes

The photodegradation of anthracene (AN) and benzo[a]pyrene (BaP), two priority polycyclic aromatic hydrocarbons (PAHs), was examined at ultra-trace levels in surface water to elucidate their behaviour under several irradiance values and types of radiation. The emitting flux and the spectrum of the lamps were found to develop a crucial role in AN and BaP degradation since removal efficiencies of the target contaminants higher than 99% were found after 15 min of irradiation under an ultraviolet C (UVC) irradiance of 0.63 mW/cm2, corresponding to a fluence of 560.25 mJ/cm2. On the other hand, although ultraviolet A (UVA) lamps exhibited a higher irradiance compared to that of UVC lamps, they were not efficient for degrading the target PAHs. The removal kinetic studies corroborated these findings, being the AN elimination rate in surface water higher than that in deionized water at optimal operating conditions. Disinfection potential was also measured. A rapid microbial load inactivation, in terms of total coliforms naturally contained in the water matrix studied, was evidenced within 15 min of treatment for the fluence referred. However, after 24 hr in the dark, a regrowth was observed. Additionally, photolysis products more toxic than the parent compounds were found, which were not removed even by extending the treatment time. In this regard, it can be concluded that the individual action of UVC light for removing AN and BaP with disinfection purposes is not an efficient treatment; therefore, the use of radiation in combination with other kinds of treatments is required.