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Denitrification and the controlling factors in Yunnan Plateau Lakes(China): Exploring the role of enhanced internal nitrogen cycling by algal blooms

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Journal of Environmental sciences 2019年第2期31卷 349-358页

作者： Sifeng Wu Zhen Wu Zhongyao Liang Yong Liu Yilin Wang college of Environmental sciences and Engineering Key Laboratory of Water and Sediment Sciences (MOE)Peking University college of Environmental sciences and Engineering Key Laboratory of Water and Sediment Sciences(MOE)Peking University

Denitrification plays an important role in nitrogen(N) removal in freshwater ecosystems.This internal process regulates the fluctuations of N concentration, especially for lakes with high nutrients concentrations and long residence time. Lakes in Yunnan plateau(southwestern China) provide typical cases, while studies in this region have been rare.Therefore, we studied denitrification of two lakes(Lake Dianchi in hypereutrophic state and Lake Erhai in mesotrophic) in this region. We used acetylene inhibition technique to quantify potential denitrification rate(PDR) of these lakes in April and August, 2015 and 2016. PDR of the sediments ranged 0–1.21 μmol/(N·m^2·hr), and that of overlying water ranged 0–0.24 μmol/(N·L·hr). Then, we used Least Angle Regression to determine the controlling factors for denitrification. Nutrients controlled PDR from two aspects: providing essential nitrogen sources; and affecting the richness and metabolism of denitrifying bacteria. In April, both aspects limited PDR; while only nitrogen sources limited PDR in August, due to depleted nitrate and enhanced denitrifying bacteria activity. Ammonia was most significant to denitrification, indicating that nitrate from nitrification transported to the bottom of wellmixed lake provide major N source by denitrification. The high PDR and low nitrate concentrate in August were evidence of an enhanced internal N cycling by algal blooms.

关键词： Denitrification Controlling factors Lake Dianchi Lake Erhai Algal bloom Internal cycling

Effects of the mixing degree upstream of the diverging area on the pollutant allocation characteristics of a braided river

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2022年第9期23卷 733-744页

作者： Jun ZOU Jian-min ZHANG Chang-yuan LI college of water Resource&Hydropower Sichuan UniversityChengdu 610065China Jiangxi Provincial Institute of water sciences Nanchang 330029China

The mixing degree upstream of the diverging area is one of the important factors influencing the pollutant allocation characteristics of braided rivers,but the effect remains unclear at present.In this paper,physical model tests were designed to study the effect on the pollutant flux ratio with six branching forms and a series of longitudinal discharge distances.The results indicated that the mixing degree upstream of the diverging area,which is closely related to the longitudinal discharge distance,notably affected the pollutant flux ratio.The lower the mixing degree,the larger was the deviation of the pollutant flux ratio from the discharge ratio.Moreover,a linear relationship was attained between the dimensionless mixing degree and the dimensionless deviation of the pollutant flux ratio from the discharge ratio.Consideration of different branching angles or different water layers or different branches did not affect this trend.The experimental results further demonstrated that the intercept and slope of the aforementioned linear relationship depended on the branching angle and exhibited an opposite monotonicity with a symmetric branch angle as the dividing point.These results help towards a better understanding of the mechanism of the factors influencing pollutant transport in complicated braided rivers,and provide a new approach to predicting the pollutant flux ratio of braided rivers.

关键词： Mixing degree upstream Diverging area Longitudinal distance Deviation of pollutant flux ratio Standard deviation Linear relationship

Temporal variations of reference evapotranspiration and its sensitivity to meteorological factors in Heihe River Basin, China

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water Science and Engineering 2015年第1期8卷 1-8页

作者： Jie Zhao Zong-xue Xu De-peng Zuo Xu-ming Wang College of Water Sciences Beijing Normal University

On the basis of daily meteorological data from 15 meteorological stations in the Heihe River Basin （HRB） during the period from 1959 to 2012, long-term trends of reference evapotranspiration （ET0） and key meteorological factors that affect ET0 were analyzed using the Mann- Kendall test. The evaporation paradox was also investigated at 15 meteorological stations. In order to explore the contribution of key meteo- rological factors to the temporal variation of ET0, a sensitivity coefficient method was employed in this study. The results show that：（1） mean annual air temperature significantly increased at all 15 meteorological stations, while the mean annual ET0 decreased at most of sites; （2） the evaporation paradox did exist in the HRB, while the evaporation paradox was not continuous in space and time; and （3） relative humidity was the most sensitive meteorological factor with regard to the temporal variation of ET0 in the HRB, followed by wind speed, air temperature, and solar radiation. Air temperature and solar radiation contributed most to the temporal variation of ETo in the upper reaches; solar radiation and wind speed were the determining factors for the temporal variation of ET0 in the middle-lower reaches.

关键词： Reference evapotranspiration Evaporation paradox Meteorological factor Heihe River Basin

Progress in plant phenology modeling under global climate change

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Science China Earth sciences 2020年第9期63卷 1237-1247页

作者： Yongshuo FU Xinxi LI Xuancheng ZHOU Xiaojun GENG Yahui GUO Yaru ZHANG College of Water Sciences Beijing Normal UniversityBeijing 100875China

Plant phenology is the study of the timing of recurrent biological events and the causes of their timing with regard to biotic and abiotic forces.Plant phenology affects the structure and function of terrestrial ecosystems and determines vegetation feedback to the climate system by altering the carbon,water and energy fluxes between the vegetation and near-surface atmosphere.Therefore,an accurate simulation of plant phenology is essential to improve our understanding of the response of ecosystems to climate change and the carbon,water and energy balance of terrestrial ecosystems.Phenological studies have developed rapidly under global change conditions,while the research of phenology modeling is largely lagged.Inaccurate phenology modeling has become the primary limiting factor for the accurate simulation of terrestrial carbon and water cycles.Understanding the mechanism of phenological response to climate change and building process-based plant phenology models are thus important frontier issues.In this review,we first summarized the drivers of plant phenology and overviewed the development of plant phenology models.Finally,we addressed the challenges in the development of plant phenology models and highlighted that coupling machine learning and Bayesian calibration into process-based models could be a potential approach to improve the accuracy of phenology simulation and prediction under future global change conditions.

关键词： Global change Plant phenology Phenology modeling Machine learning Ecophysiological experiment

Climate change trend and its effects on reference evapotranspiration at Linhe Station, Hetao Irrigation District

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water Science and Engineering 2014年第3期7卷 250-266页

作者： Xu-ming WANG Hai-jun LIU Li-wei ZHANG Rui-hao ZHANG College of Water Sciences Beijing Normal University

Linhe National Meteorological Station, a representative weather station in the Hetao Irrigation District of China, was selected as the research site for the present study. Changes in climatic variables and reference evapotranspiration （ET0 ）（estimated by the Penman-Monteith method） were detected using Mann-Kendall tests and Sen＇s slope estimator, respectively. The authors analyzed the relationship between the ET0 change and each climatic variable＇s change. From 1954 to 2012, the air temperature showed a significant increasing trend, whereas relative humidity and wind speed decreased dramatically. These changes resulted in a slight increase in ETo. The radiative component of total ET0 increased from 50% to 57%, indicating that this component made a greater contribution to the increase in total ETo than the aerodynamic component, especially during the crop growing season （from April to October）. The sensitivity analysis showed that ETo in Hetao is most sensitive to mean daily air temperature （11.8%）, followed by wind speed （-7.3%） and relative humidity （4.8%）. Changes in sunshine duration had only a minor effect on ET0 over the past 59 years.

关键词： climatic variables reference evapotranspiration change trend Mann-Kendall test sensitivity analysis

Degradation of dissolved organic matter in effluent of municipal wastewater plant by a combined tidal and subsurface flow constructed wetland

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Journal of Environmental sciences 2021年第8期33卷 171-181页

作者： Chunjian Lyu Ruixia Liu Xiaojie Li Yonghui Song Hongjie Gao Basin Research Center for water Pollution Control Chinese Research Academy of Environmental SciencesBeijing 100012China College of Water Sciences Beijing Normal UniversityBeijing 100875China

Dissolved organic matter(DOM)is an important constituent of wastewater treatment plant(WWTP)effluent.A novel combined tidal and subsurface flow constructed wetland(TF-SSFCW)of 90 L was constructed for a ten-month trial of advanced treatment of the WWTP effluent.Excitation emission matrix(EEM)fluorescence spectroscopy,parallel factor(PARAFAC)analysis and a two end-member mixing model were employed to characterize the composition and removal process of the effluent DOM(EfOM)from the WWTP.The results showed that the TF-SSF-CW performed an efficient EfOM removal with dissolved organic carbon(DOC)removal rate of 88%and dissolved organic nitrogen(DON)removal rate of 91%.Further analysis demonstrated that the EfOM consisted mainly of two protein moieties and two humic-like groups;protein moieties(76%)constituted the main content of EfOM in raw water and humic-like groups(57%)became the dominating contributor after treatment.The EfOM from the WWTP was mainly of aquatic bacterial origin and evolved to a higher proportion of terrigenous origin with higher humification in the TF-SSF-CW effluent.A common controlling treatment-related factor for determining the concentrations of the same kind of substances(protein groups or humic-like groups)was revealed to exist,and the ratio of removal rates between the same substances in treatment was calculated.Our study demonstrates that the TF-SSF-CW can be a novel and effective treatment method for the EfOM from WWTPs,and is helpful for understanding of the character of EfOM in wetland treatment.

关键词： Constructed wetland Effluent organic matter Excitation emission matrices PARAFAC analysis

Identifying the key N species for electrocatalytic oxygen reduction reaction on N-doped graphene

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Nano Research 2023年第5期16卷 6642-6651页

作者： Yiyin Peng Zhaoyong Bian Wenhai Zhang Hui Wang College of Water Sciences Beijing Normal UniversityBeijing 100875China college of Environmental Science and Engineering Beijing Forestry UniversityBeijing 100083China

The state of nitrogen in nitrogen-doped graphene(NG)promoting the conversion of molecular oxygen to hydrogen peroxide was investigated.The oxygen reduction reaction(ORR)reactivity of graphitic-N,pyrrolic-N,pyridinic-N in NG was predicted by density functional theory(DFT).A series of NG samples with different contents of these doped nitrogen types were prepared by the low-temperature thermal reduction method and used for the ORR evaluation.The H_(2)O_(2)yield,2e−ORR current efficiency,H_(2)O_(2)selectivity,electron transfer number(n)were systematically studied.The 2e−ORR selectivity was positively correlated with the N content,approaching 100%with increasing N content(0.40 V vs.reversible hydrogen electrode(RHE)),whereas the comparative energy efficiency showed a volcano-type trend related to N content,reaching a maximum of 94%.In addition,N species validation experiments proved the key role of pyrrolic-N in the synthesis of H_(2)O_(2).Compared with a pure graphene catalyst,further contaminant degradation studies on NG electrodes with different pyrrolic-N contents revealed that the lower pyrrolic-N the higher removal of p-nitrophenol(PNP).This work provides insight into the mechanism of ORR on metal-free catalysts and a facile approach to optimize this important environmental catalytic strategy.

关键词： oxygen reduction electrocatalysis nitrogen-doped graphene environmental remediation

Research progresses and prospects of multi-sphere compound extremes from the Earth System perspective

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Science China Earth sciences 2024年第2期67卷 343-374页

作者： Zengchao HAO Yang CHEN College of Water Sciences Beijing Normal UniversityBeijing100875China State Key Laboratory of Severe Weather Chinese Academy of Meteorological SciencesBeijing100081China

Compound extremes,whose socioeconomic and ecological impacts are severer than that caused by each event occurring in isolation,have evolved into a hot topic in Earth Science in the past decade.In the context of climate change,many compound extremes have exhibited increasing frequency and intensity,and shown novel fashions of combinations,posing more pressing demands and tougher challenges to scientific research and disaster prevention and response.This article,via a perspective of multi-sphere interactions within the Earth System,systematically reviews the status quo,new scientific understanding,and deficiencies regarding the definition,mechanism,change,attribution,and projection of compound extremes.This study also sorts out existing challenges and outlines a potential roadmap in advancing the study on compound extremes with respect to data requirement,mechanistic diagnosis,numerical modeling,attribution and projection,risk assessment,and adaptive response.Further directions of compound extremes studies and key research topics that warrant multi-disciplinary and multisectoral coordinated efforts are also proposed.Given that climate change has reshaped the type of extremes,a transformation from the traditional single-event perspective to a compound-event perspective is needed for scientific research,disaster prevention and mitigation,and climate change adaptation,calling for bottom-up innovation in research objects,ideas,and methods.This article will add value to promoting the research on compound extremes and interdisciplinary cooperations.

关键词： Extremes Compound extremes Climate change and risk Multi-sphere interactions

Review on utilization of biochar for metal-contaminated soil and sediment remediation

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Journal of Environmental sciences 2018年第1期30卷 156-173页

作者： Mingming Wang Yi Zhu Lirong Cheng Bruce Andserson Xiaohui Zhao Dayang Wang Aizhong Ding College of Water Sciences Beijing Normal University Department of Civil Engineering Queen's University

Biochar is a carbon-neutral or even carbon-negative material produced through thermal decomposition of plant-and animal-based biomass under oxygen-limited conditions.Recently, there has been an increasing interest in the application of biochar as an adsorbent, soil ameliorant and climate mitigation approach in many types of applications.Metal-contaminated soil remediation using biochar has been intensively investigated in small-scale and pilot-scale trials with obtained beneficial results and multifaceted effects.But so far, the study and application of biochar in contaminated sediment management has been very limited, and this is also a worldwide problem. Nonetheless, there is reason to believe that the same multiple benefits can also be realized with these sediments due to similar mechanisms for stabilizing contaminants. This paper provides a review on current biochar properties and its use as a sorbent/amendment for metal-contaminated soil/sediment remediation and its effect on plant growth, fauna habits as well as microorganism communities. In addition, the use of biochar as a potential strategy for contaminated sediment management is also discussed, especially as regards in-situ planning. Finally, we highlight the possibility of biochar application as an effective amendment and propose further research directions to ensure the safe and sustainable use of biochar as an amendment for remediation of contaminated soil and sediment.

关键词： Biochar Metal contamination Soil/sediment remediation Biological effect