Water quality prediction based on multi-task learning

Water pollution seriously endangers people’s lives and restricts the sustainable development of the economy. Water quality prediction is essential for early warning and prevention of water pollution. However, the nonlinear characteristics of water quality data make it challenging to accurately predicted by traditional methods. Recently, the methods based on deep learning can better deal with nonlinear characteristics, which improves the prediction performance. Still, they rarely consider the relationship between multiple prediction indicators of water quality. The relationship between multiple indicators is crucial for the prediction because they can provide more associated auxiliary information

Macrophyte identity shapes water column and sediment bacterial community

By assembling mesocosms and utilizing high-throughput sequencing, we aim to characterize the shifts of the bacterial community in freshwaters driven by two contrasting submerged macrophyte species, Ceratophyllum demersum L. and Vallisneria spiralis L. Although the microbe in both the water column and sediment were largely modulated by the macrophyte, the effect varied considerably depending on bacterial locations and macrophyte species. Actinobacteria was the most abundant taxa in the water column of all the three treatments, but its abundances were significantly higher in the two planted treatments. Moreover, Alphaproteobacteria showed high abundance only in the unplanted control. For bacterial taxa in the sediment, C. demersum significantly increased the relative abundance of Anaerolineae but reduced the relative abundance of Betaproteobacteria and Gammaproteobacteria, while V. spiralis increased the relative abundance of Deltaproteobacteria and Gammaproteobacteria. Additionally, in the C. demersum treatment, the water column bacterial community increased more dramatically in richness, alpha diversity, and the relative abundance of the dominant taxa than those in the V. spiralis treatment. Taken together, the findings from this study reveal that the two species of submerged macrophyte modified the bacterial community in waters, despite the obvious interspecific performance differences

General trends in freshwater ecological restoration practice in China over the past two decades: the driving factors and the evaluation of restoration outcome

Background Although freshwater ecological restoration (FER) has undergone an immense development over the past two decades in China either in the number of projects or in the spatial scale of implementations, a dearth of clear and comprehensive trends in this field is still a particular concern. We conducted a literature survey through searching the database of Web of Science between 1997 and 2017 to investigate the driving force behind FER practice and to summarize the restoration outcomes. Results A total of 2047 publications were hit and 198 of them were finally retained after manual screening. The number of studies in this field has been steadily increasing in recent years and their provincial distribution is positively correlated with GDP growth and the investment to pollution control and environmental protection, suggesting that economic development is a key driving factor of FER practice. Among the remaining articles, nearly half (46.5%) focus on lake ecosystems, and 34.8% and 32.8% of the studies indicate that land reclamation and eutrophication are the predominant causes of freshwater ecosystem degradation. The overarching target of the restoration is biodiversity increase (31.4%), followed by water quality improvement (24.7%) and ecosystem services (23.9%). Revegetation is a dominant restoration approach (40.9%). Reference sites for assessment of restoration projects are normally control locations without intervention (60%), or the status of the targeted sites before the interventions. For the restoration outcome evaluation, 86% of the studies present positive outcomes in terms of water quality improvement, and 79% have improvement in biological features. The most frequently monitored organisms are macrophytes (31%), followed by benthos as indicators of ecological condition. Conclusions Economic growth, water pollution and investment into environmental protection are the main driving factors of FER practice in China. The effort of restoration and evaluation over the past two decades has not been limited to improving hydrological function and water quality, but also pay increasingly more attention to biological processes and ecological integrity, and further the ecosystem services in recent years. However, the lack of long-term monitoring and socioeconomic attributes considered in restoration success assessments are still particular issues that need to be addressed in the future FER researches and projects

Effects of Artificial Reefs on Phytoplankton Community Structure in Baiyangdian Lake, China

The habitat and feeding environment of freshwater fish in freshwater lakes have been destroyed, with the problem of miniaturization and simplification of catches being serious. An artificial reef is an effective technical measure to protect and proliferate offshore fishery resources, but little research has been conducted on its application in freshwater lakes. A small artificial reef for freshwater lakes was designed according to the water depth of the lake and the habits of benthic fish. The artificial reef is composed of biomass modules, each of which is 900 × 120 mm. The community structure of phytoplankton around the artificial reef and its adjacent waters was studied. The results showed that 77 species from seven phyla were identified, with a high number of species from the Chlorophyceae. In terms of density composition, the density of cyanobacteria decreased month by month, while the phylum Chlorophyta and Cryptophyta increased first and then decreased. As for biomass composition, Chlorophyta and Cryptophyta increased first and then decreased. RDA analysis showed that water temperature, dissolved oxygen, and total phosphorus were the main influencing factors. To sum up, the artificial reef can improve the algae phase in the surrounding water column, inhibit the growth and reproduction of cyanobacteria to a certain extent, and have a significant enrichment and promotion effect on diatoms. Artificial fish reef affects the phytoplankton community structure of the surrounding water bodies mainly through the absorption of phosphorus nutrients. Artificial reefs can be popularized and applied in freshwater lakes to provide foraging and shelter for benthic fish in the lake

Enzyme activities in pilot-scale constructed wetlands for treating urban runoff in China: temporal and spatial variations

Two pilot-scale integrated constructed wetland (ICW) systems were constructed to assess the feasibility of treating urban runoff in Hefei, P.R. China. Each ICW consisted of a down-flow chamber (50m(2), planted with Canna indica), an up-flow chamber (50m(2), planted with Iris pseudacorus), and a horizontal subsurface-flow chamber (50m(2), planted with Acorus calamus) in series. Substrate enzyme activities, growth of vegetation, and contaminant removal efficiencies were monitored during a one-year period. These two systems, achieved an average efficiency of 64.8% for total phosphorus (TP), 59.6% for total nitrogen (TN), 52.7% for ammonium (NH4+-N, and 72.7% for chemical oxygen demand (COD). There were significant correlations between the phosphatase (PP) activity and the removal efficiencies of TP and COD, as well as between the urease (UR) activity and TN removal. The activities of both nitrate reductase (NR) and PP were the highest in down-flow chamber (DFC), and then in up-flow chamber (UFC) and horizontal subsurface-flow chamber (HFC), successively. Meanwhile, the maximum enzyme activities of DFC and UFC occurred in summer or autumn when plants were in the vigorous growing stage. Furthermore, the enzyme activities of both PP and UR were significantly correlated with all growth parameters of C. indica in DFC. Significant correlations existed between the root number of I. pseudacorus, and PP and UR activities in UFC. In HFC, there were no significant correlations between the enzyme activities (PP, UR, and NR) and all growth parameters of A. calamus

shorttermeffectsofdrawingwaterforconnectivityofriversandlakesonzooplanktoncommunitystructure

During 28-29, September 2005, water was drawn from Hanjiang River and Houguan Lake to the Yangzi River via Sanjiao Lake and Nantaizi Lake in Wuhan in order to provide favorable conditions for ecosystem restoration. To evaluate the feasibility and validity of drawing water as a means of ecosystem restoration, zooplankton populations were studied 3 times (before, immediately after finishing and a month after drawing water) at seven locations from 27 Sept. 2005 to 2 Nov. 2005. Water quality in the lakes was mostly improved and zooplankton species richness decreased as soon as drawing water had finished but increased a month after drawing water. Zooplankton density and biomass was reduced in the lakes by drawing water but was increased at the entrance to Sanjiao Lake because of landform geometry change. Before drawing water, most species in Sanjiao Lake e.g., Brachionus sp. and Keratella sp. were tolerant of contamination. After drawing water oligotrophic-prone species such as Lecane ludwigii and Gastropus stylifer emerged. We conclude that drawing water could be important for improving water quality and favour ecosystem restoration. Dilution of nutrient concentrations may be an important role in the effect

Effects of Cd(2+) and Pb(2+) on the substrate biofilms in the integrated vertical-flow constructed wetland

The effects of single Cd(2+) and Pb(2+), and combined Cd(2+) and Pb(2+) on dehydrogenase activity and polysaccharide content of the substrate biofilms in the integrated vertical-flow constructed wetland (IVCW) were studied. Dehydrogenase activities decreased linearly with the increasing concentrations of Cd(2+) and Pb(2+) at different times (6, 24, 72, and 120 h). The activities at both 6 and 24 h were significantly higher than that at 72 and 120 h in the case of single and combined treatments. The single Cd(2+) and Pb(2+) treatments significantly inhibited dehydrogenase activities at concentrations in excess of 20 mu mol/L Cd(2+) and 80 mu mol/L Pb(2+), respectively. The inhibitory effect of Cd(2+) was much greater than that of Pb(2+). At the same time, the combined treatment of Cd(2+) and Pb(2+) Significantly inhibited dehydrogenase activities at all five concentrations studied and the lowest combined concentration was 1.25 mu mol/L Cd(2+) and 5 mu mol/L Pb(2+). A synergistic effect of Cd(2+) and Pb(2+) was observed. On the other hand, polysaccharide contents varied unpredictably with the increasing concentrations of Cd(2+) and Pb(2+) and extended experimental time. There were no significant statistical differences within the range of concentration and time studied, whether singly or in combination. These results implied that the effects of heavy metals on biofilms should be a concern for the operation and maintenance of constructed wetlands

Responses of water quality and phytoplankton assemblages to remediation projects in two hypereutrophic tributaries of Chaohu Lake

Water shortages and the presence of point and diffuse source pollution have caused a serious deterioration in water quality in two tributaries (the Tangxi River and Shiwuli River) of Chaohu Lake, China. To reduce nutrient pollution and suppress harmful algal blooms (HABs), hard engineering and ecological remediation projects were implemented. A post-project investigation from 2013 to 2016 was carried out to evaluate the outcome of the remediation projects by monitoring the seasonal and spatial variations in water quality and the phytoplankton community. In the Tangxi River, the average total phosphorus (TP) concentrations in the four seasons were below 0.5 mg L-1, with the lowest concentration (0.29 +/- 0.12 mg L-1) found in autumn. Remediation measures including sediment dredging, riparian buffer zone creation, downstream wetland park construction, and water augmentation using reclaimed water and filtered lake water might combine to promote P source mitigation. Moreover, the percentage of bloom-forming cyanobacteria (i.e., Microcystis, Aphanizomenon, Anabaena, Osanatoria, Phormidium and Planktothrix) in the phytoplankton assemblage and the biomass of the dominant species indicated successful HAB control. In the Shiwuli River, water quality improvements and phytoplankton responses have been observed since 2015 after the upgrading of a local wastewater treatment plant (WWTP) with effluent that was used for flow augmentation. Nevertheless, there is still room for improvement via increasing the river self-purification ability (e.g., the creation of downstream wetlands and riparian buffer zones) and promoting water augmentation according to the experience gained in the remediation projects of the Tangxi River.</p