Potamogeton crispus restoration increased the epiphytic microbial diversity and improved water quality in a micro-polluted urban river.

Special characterization and assembly of epiphytic microbial communities remain unclear in micro-polluted water column during submersed macrophytes restoration. In this study, an in-situ enclosure area sowing with turions of Potamogeton crispus (P. crispus) was conducted in a micro-polluted urban river to investigate the characterization of P. crispus and epiphytic microbial communities and their response to water environment under different water depths. Turions completely germinated in water column with <90 cm water depth and the germination speed decreased with increasing water depth within 18 days. There were obvious differences in morphological characteristics of P. crispus between deep and shallow water layers. P. crispus restoration decreased by 12-32%, 13-36%, 9-43% and 5-36% of COD, NH4+-N, TN and TP concentration, respectively, in enclosed overlying water compared to the river (P < 0.05) during 5 months of experiment. Illumina sequencing was employed to explore the epiphytic bacterial and microeukayotic communities at water depth 25-35 cm (shallow area) and 80-90 cm (deep area). A total of 9 bacterial and 12 microeukayotic dominant phyla were obtained in eight samples. It should be noted that the algae abundances were higher in shallow area than deep area but a reverse trend was observed for methanotrophs. Null model analysis revealed that dispersal limitation and undominated process was the most important assembly process, whereas stochastic processes gained more importance in shallow area than deep one. According to cooccurrence analysis (|r| > 0.6, P < 0.05), there were more strongly correlated edges in shallow area (456 edges) than deep area (340 edges). These results highlight that submerged macrophytes restoration can increase microbial diversity and improve water quality, and provide a "summer disease cured in winter" way by using could-resistant P. crispus for water purification in micro-polluted rivers in low-temperature season.

Vallisneria natans decreased CH4 fluxes in wetlands: Interactions among plant physiological status, nutrients and epiphytic bacterial community.

Submerged macrophytes provide niches for epiphytic microbes (including aerobic methanotrophs) growth. However, little is known about the impacts of submerged macrophytes growth status and nutrients loadings on methanotroph community and methane release in wetlands. In the present study, methane fluxes, bacterial and methanotroph community in epiphytic biofilm, and environmental parameters were investigated during Vallisneria natans senescence in wetlands under low (VnL) and high (VnH) nutrients for seven weeks. Relative conductivity and concentration of H2O2, total chlorophyll and malondialdehyde were higher in leaves of V. natans in VnH than VnL at the same sampling time. Nutrients loading increased methane fluxes in treatments with or without (Control) macrophytes, while healthy V. natans plants reduced the methane flux and nutrients concentration in water columns. CH4 fluxes were positively correlated to temperature and COD (p < 0.05). Methane oxidation rates were 3.04-31.68 µmol methane mg-1 fresh weight of V. natans leaves - epiphytic biofilm within 1 h. Proteobacteria, Cyanobacteria, Bacteroidetes, Verrucomicrobia, Planctomycetes, Actinobacteria and Acidobacteria were dominant phylum in all epiphytic biofilms. The mean abundances of pmoA/16S rRNA were higher in VnL than VnH. According to Illumina sequencing results of pmoA gene, γ-proteobacteria and α-proteobacteria were the dominant methanotroph class in epiphytic biofilm from VnH and VnL, respectively. Among seven detected methanotrophic genera, Methylomonas was significantly higher in VnH than VnL. Network analysis revealed that there were much closer relationships between the environmental parameters and epiphytic bacterial community in VnH than in VnL. COD and MDA were negatively correlated with Methyloglobulus, Methylosarcina, Methylobacter and Methylocystis, but positively correlated with Methylomonas and Methylosinus. This study highlights that methanotrophs in epiphytic biofilm play important roles in methane-oxidizing, which can be affected by plant physiological status and environmental parameters.

Interactions between suspended sediments and submerged macrophytes-epiphytic biofilms under water flow in shallow lakes.

Suspended sediments (SS) pollution is one of the factors affecting the transfer from turbid water state to clear water state in shallow lakes. However, the interactions between suspended sediments and submerged plants are far from clear. In this study, we investigated the settlement laws of SS in overlying water and its impact on the epiphytic biofilm of Myriophyllum verticillatum and Vallisneria natans under water flow. At least 90% of turbidity can be removed from overlying water, and the decreasing trend of water turbidity fitted the logarithmic decay model in all treatments. The size distribution of SS fit the log-normal distribution model in the first 240 min after SS addition. It should be noted that the main peak particle sizes were lower in treatments with submerged macrophytes (8.71-13.18 µm) than without plants (15.14-19.95 µm). Water flow and SS addition significantly increased the thickness of biofilms attached to M. verticillatum (p < 0.05), but they together significantly reduced the biofilm thickness on V. natans (p < 0.05). SS increased the bacterial α-diversity but decreased eukaryotic one in epiphytic biofilms. However, water flow had a more significant impact on microbial communities (especially eukaryotes) than SS and plant species. The relative abundances of dominant phylum Proteobacteria, class Alphaproteobacteria and Betaproteobacteria, and class Verrucomicrobiae increased in epiphytic biofilms after SS addition. Co-occurrence networks reveal that photosynthetic microbes in epiphytic biofilms played an important role in microbial communities under water flow and SS, and many hub microbes were increased by SS addition but reduced by water flow. These data highlight that SS decline can be predicted by the logarithmic decay model and, SS and water flow can affect the epiphytic-biofilm on submerged macrophytes.

Analysis of mercury emissions and cycles in typical industrial city clusters: a case study in China.

China's Suzhou (SZ), Wuxi (WX), and Changzhou (CZ) (collectively referred to as the SXC area) have developed economies and advanced industrial production, which are typical industrial city clusters. To analyze the Hg flow characteristics, we quantified the Hg emissions and circulation according to six categories (including industrial production, agricultural livestock, vehicle exhaust, solid waste, atmospheric deposition, and runoff). The results showed that the Hg emission from coal accounting for 40.99% of the total circulation. The amount of Hg circulating in SZ is obviously higher than those in WX and CZ, accounting for 47.88% of the total regional emissions. The Hg pollution in SXC area represent an optimistic level. Except that the Hg concentration in the soil in WX is slightly higher than the first-level soil quality standard, the water and atmosphere in the three cities and the soil in SZ and CZ all meet the highest national standards. The study provides in-depth statistics on the Hg cycle characteristics of typical industrial urban agglomerations. It is beneficial to the management of Hg and provides a basis for the implementation of different schemes in different stages of production and emission, so as to effectively prevent the occurrence of serious heavy metal poisoning hazards. This research idea is widely used and can be applied to other regions and other heavy metal elements.

The change of water content and role of microbe in the sludge drying process.

In this study, the pure terephthalic acid sludge was treated by a drying process which was an economical and environmentally method. The water change and metabolic pathways for bacterial community function prediction were analyzed. The microbial community changes were studied by high-throughput sequencing to draw the dynamic succession model. Then multiple statistics was used to determine the key factors of the reduction. The results showed that the main stage of water loss in the PTA sludge drying process was the high temperature period where the water lost by evaporation accounted for more than 90% of the total removal. The main metabolic pathways for bacterial community function were amino acid (7.72%-8.71% of Kyoto encyclopedia of genes and genomes relative abundance and 8.26%-9.51% of Cluster of orthologous groups of proteins relative abundance) and carbohydrate metabolism. The model describing the dynamic succession of microbial communities showed that the dominant bacteria changed from Nitrospira, Novosphingobium and Azohydromonas to Pseudomonas, Paeniglutamicibac and Pelotomaculum. The key factors for water loss were Gemmatimonas, Novosphingobium and Azohydromonas with the correlation coefficients of 0.887, 0.772, 0.783, respectively; the key factors for dry matter loss were Pelotomaculum, total organic matter, dissovlved organic carbon and carbon/nitrogen ratio; the key factors for toxic substance loss were Brevundimonas, Novosphingobium and Gemmatimonas. These results provided theoretical support for the application and demonstration for hazardous waste sludge reduction.

Performance and mechanism of high-speed vermicomposting of dewatered sludge using a new type of laboratory earthworm reactor.

To solve the problem of the traditional vermicomposting cycle being too long, a new type of laboratory earthworm reactor was developed for high-speed vermicomposting of sludge. The earthworm reactor was established based on the model of first creating an optimal living environment for earthworms and then introducing sludge into the environment for vermicomposting. In addition, we selected four different materials to condition sludge to optimize the treatment efficiency and shorten the vermicomposting cycle. The results revealed that the use of the new earthworm reactor for high-speed vermicomposting can shorten the vermicomposting cycle to 61.33 h, which is 1/30 of the traditional method. Compared to the traditional method, the vermicompost obtained from high-speed vermicomposting had better stability and maturity (C/N: 14.96, humification index: 4.69, Germination index: 78.84%, TOC: 88.5 mg/g and ash content: 686 mg/g). Besides, the FT-IR, SEM, EEM, and enzyme activity from the earthworm analysis results show that the addition of vermicompost (raw material) was beneficial to the stability and mineralization of the final vermicompost for dewatered sludge vermicomposting.

Pilot-scale vermicomposting of sewage sludge mixed with mature vermicompost using earthworm reactor of frame composite structure.

To improve the efficiency of sludge vermicomposting, a new cost-effective method is provided. It uses a new earthworm reactor with a frame composite structure for vermicomposting and reuses mature vermicompost to condition the sludge. Under the optimum conditions (proportion of earthworm droppings: 15%; thickness of sludge laying: 6 cm; moisture content of initial sludge mixture: 75%), the method of continuous operation described herein works well and presents three advantages compared with the traditional vermicomposting method: the short time required for vermicomposting (20.25 h); covering a small area (5 m2/t·d); and a low cost. In addition, the vermicompost obtained from sludge vermicomposting shows better stability and maturity (C/N: 14.96; GI: 86.42%; TOC: 188.5 mg/g; ash content: 516.2 mg/g). The investigation of the associated mechanisms, including 3D-EEM, TGA, SEM and microbial community analyses, revealed that the addition of mature vermicompost can speed up the progress of decomposition and humification of organic matter in sludge. The process of vermicomposting and adding mature vermicompost significantly modified the microbial community of sewage sludge, and the changes in microorganisms in vermicompost were related to the microorganisms in the earthworm gut.

Intensity analysis of chromium cycling in south Jiangsu region of China.

Suzhou (SZ), Wuxi (WX) and Changzhou (CZ) (collectively called the SXC area) in southern Jiangsu Province surround Tai Lake on three sides and have an important impact on its ecology. The emission and circulation of Cr in the three cities were quantified according to the six categories (including industry production, agricultural livestock, vehicle exhaust, solid waste, atmospheric subsidence and runoff) to analyze its regional characteristics and source category characteristics and to build a Cr cycle diagram to evaluate the pollution situation. The results showed that the Cr emissions from solid waste were the highest and mostly came from industrial sludge, accounting for 76.4% of the total circulation. The Cr emissions from SZ and WX were significantly higher than those of CZ, accounting for 47.0% and 42.9% of the regional total. The Cr in the excrement of pigs and poultry, dry sedimentation and surface runoff exceeded 100 tons every year, which needed to be valued. The Cr concentration in the surface water, soil and atmosphere in SXC area all met with the highest national standards. Studies have shown that the sediments and benthic organisms in the west and north of Tai Lake were already in a low-pollution state, but which was overall acceptable. Through this study, Cr circulation was clarified in typical areas, which was convenient for the monitoring and management of heavy metal pollution in the areas surrounding Tai Lake.

Reduction of sludge by a biodrying process: Parameter optimization and mechanism.

Sewage sludge generated from chemical fiber plants is a hazardous waste with high disposal costs, and it is important to reduce the amount of sludge produced. In this study, a biodrying technology was controlled by thermophilic microorganisms to reduce and detoxify hazardous waste sludge. Ten batches of experiments were conducted under optimal parameters (i.e., under the conditions of a one-time feeding with the equipment temperature controlled at 60 °C, where the dosage of the microbial agent accounted for 4% of the dry weight of sludge) to evaluate the performance of the biodrying system reducing and detoxifying hazardous waste sludge under a continuous reaction. The results showed that the degree and rate of dehydration during the continuous reaction were 65.97% and 2.51%, respectively. The degrees of reduction for dry matter and toxic substances were 22% and 9%, respectively. The calorific value of sludge after treatment increased from 1678.53 J (later abbreviated as J) to 12256.17 J. The reduction effect in the pilot-scale experiment was 65%. Spectral analysis and microbial sequencing of the freeze-dried sludge advance our understanding of biodrying mechanisms and provide a foundation for the application of key technologies for the reduction and detoxification of hazardous waste sludge.

Pilot-scale composting of typical multiple agricultural wastes: Parameter optimization and mechanisms.

In this work, pilot-scale (100 kg of mixed wastes each time) composting of typical agricultural wastes, including chicken manure, vegetable leaves and rice husks with a mass ratio of 6:3:1, was studied. Effects of thermal phases and transformation time on performance, including moisture, nutrient, and carbon contents and C/N ratios of compost, were investigated. The optimal parameters were 75 ±â€¯5 °C and 18 h; the compost met the requirements of Chinese National Agricultural Organic Fertilizer Standard (NY525-2012). Mechanisms investigations demonstrated that, Bacillus and Sinibacillus played key roles in degrading high-molecular-weighted organic substances into small-molecular-weighted humic- and fulvic-acid-like matters, resulting in smaller particle size and loose structure of the product; rice husk particles acted as a conditioning agent and remained their originally morphology. The mechanism provided informative guidance for optimizing the process in practical application.

Flavonoids, alkaloids from the seeds of Crotalaria pallida and their cytotoxicity and anti-inflammatory activities.

Three flavonoids, cropalliflavones A-C, including two homoisoflavonoids with rare skeletons; three previously undescribed alkaloids, usaramine-N-oxide and cropallins A-B; and sixteen known compounds, were isolated from the seeds of Crotalaria pallida Ait. The absolute configurations of cropalliflavone A and usaramine-N-oxide were established by an ECD calculation and X-ray crystallography, respectively. Additionally, cropalliflavone B showed anti-proliferative activity against the MCF-7 cell line with an IC50 value of 6.77 µM, and cropalliflavone C showed anti-inflammatory activity, with an IC50 value of 16.07 µM.