Liansheng He

Identifying diffused nitrate sources in a stream in an agricultural field using a dual isotopic approach.

Nitrate (NO3(-)) pollution is a severe problem in aquatic systems in Taihu Lake Basin in China. A dual isotope approach (δ(15)NNO3(-) and δ(18)ONO3(-)) was applied to identify diffused NO3(-) inputs in a stream in an agricultural field at the basin in 2013. The site-specific isotopic characteristics of five NO3(-) sources (atmospheric deposition, AD; NO3(-) derived from soil organic matter nitrification, NS; NO3(-) derived from chemical fertilizer nitrification, NF; groundwater, GW; and manure and sewage, M&S) were identified. NO3(-) concentrations in the stream during the rainy season [mean±standard deviation (SD)=2.5±0.4mg/L] were lower than those during the dry season (mean±SD=4.0±0.5mg/L), whereas the δ(18)ONO3(-) values during the rainy season (mean±SD=+12.3±3.6‰) were higher than those during the dry season (mean±SD=+0.9±1.9‰). Both chemical and isotopic characteristics indicated that mixing with atmospheric NO3(-) resulted in the high δ(18)O values during the rainy season, whereas NS and M&S were the dominant NO3(-) sources during the dry season. A Bayesian model was used to determine the contribution of each NO3(-) source to total stream NO3(-). Results showed that reduced N nitrification in soil zones (including soil organic matter and fertilizer) was the main NO3(-) source throughout the year. M&S contributed more NO3(-) during the dry season (22.4%) than during the rainy season (17.8%). AD generated substantial amounts of NO3(-) in May (18.4%), June (29.8%), and July (24.5%). With the assessment of temporal variation of diffused NO3(-) sources in agricultural field, improved agricultural management practices can be implemented to protect the water resource and avoid further water quality deterioration in Taihu Lake Basin.

Detection of Copper (II) and Cadmium (II) binding to dissolved organic matter from macrophyte decomposition by fluorescence excitation-emission matrix spectra combined with parallel factor analysis

Fluorescence excitation-emission matrix (EEM) spectra coupled with parallel factor analysis (PARAFAC) was used to characterize dissolved organic matter (DOM) derived from macrophyte decomposition, and to study its complexation with Cu (II) and Cd (II). Both the protein-like and the humic-like components showed a marked quenching effect by Cu (II). Negligible quenching effects were found for Cd (II) by components 1, 5 and 6. The stability constants and the fraction of the binding fluorophores for humic-like components and Cu (II) can be influenced by macrophyte decomposition of various weight gradients in aquatic plants. Macrophyte decomposition within the scope of the appropriate aquatic phytomass can maximize the stability constant of DOM-metal complexes. A large amount of organic matter was introduced into the aquatic environment by macrophyte decomposition, suggesting that the potential risk of DOM as a carrier of heavy metal contamination in macrophytic lakes should not be ignored.

Characterizing the fluorescent properties and copper complexation of dissolved organic matter in saline-alkali soils using fluorescence excitation-emission matrix and parallel factor analysis

PurposeThe goals of this study are to identify the individual fluorophore component in dissolved organic matter (DOM) of saline-alkali soils, to determine the binding capacities and stability constants of Cu (II) with fluorescent DOM components, and to analyze the potential impact on the complexation between Cu (II) and DOM in different soil environment.Materials and methodsDOM extracted from five saline-alkali soil samples were studied by fluorescence quenching titrations combined with three-dimensional excitation-emission matrix (3D-EEM) spectra and parallel factor analysis (PARAFAC). Modified Stern–Volmer model was used to calculate the conditional stability constant (K) and the percent of fluorophores (f %) participating in the complexation reaction.Results and discussionThree main fluorescent components in the DOM, e.g., fulvic-like (component 1), humic-like (component 2), and protein-like (component 3) were identified and characterized by fluorescence EEM-PARAFAC. Both the components 1 and 2 showed fluorescence quenching by gradual addition of Cu (II), while component 3 had no marked change in fluorescence intensity. The higher log K of DOM-Cu (II) complexes suggests that the DOM has a high Cu binding affinity. Meanwhile, humic-like components showed higher in the proportion of organic ligands than those of fulvic-like components in the DOM of saline-alkali soils.ConclusionsThe fluorescence quenching titration using EEM-PARAFAC analysis allows for the assessment of metal ion interactions with specific fluorophores, and is a good approach to study the geochemical behavior of metal ions in saline-alkali soils and to provide a support for the management of saline-alkali soil environment.

How Long, Narrowly Constructed Wetlands Purify Irrigation Return Water: A Case Study of Ulansuhai Lake, China

The use of constructed wetlands (CWs) in the treatment of raw wastewater in China has proved to be very successful in recent decades. However, it is not known whether surface-flow constructed wetlands can effectively purify irrigation return water. To investigate the performance of a constructed wetland in terms of meeting the goals of pollutant purification, the 8th drainage of Ulansuhai Lake was used for this study. Pollutant removal performances, as well as hydrological characteristic variations in relation to specific characteristics of plants, were investigated utilizing two years of monthly average data. The results indicated that surface-flow constructed wetlands can effectively change the physical characteristics of return water and lead to a sharp decrease in pollutant concentrations. The 1200 m long, narrowly constructed wetland resulted in the average reduction rates of total nitrogen (TN) and total phosphorus (TP) of up to 22.1% and 21.5%, respectively. The overall purification efficient of the constructed wetland presented seasonal variations in four different monitoring periods (May, July, September, and November). Constructed wetlands with multiple types of plants exhibited higher efficiencies in pollutants removal than those with a single type of plant. The current study can provide meaningful information for the treatment of agricultural wastewater.

Case Study on Incentive Mechanism of Energy Efficiency Retrofit in Coal-Fueled Power Plant in China

An ordinary steam turbine retrofit project is selected as a case study; through the retrofit, the project activities will generate emission reductions within the power grid for about 92,463 tCO2e per annum. The internal rate of return (IRR) of the project is only −0.41% without the revenue of carbon credits, for example, CERs, which is much lower than the benchmark value of 8%. Only when the unit price of carbon credit reaches 125 CNY/tCO2, the IRR could reach the benchmark and an effective carbon tax needs to increase the price of carbon to 243 CNY/tce in order to make the project financially feasible. Design of incentive mechanism will help these low efficiency enterprises improve efficiency and reduce CO2 emissions, which can provide the power plants sufficient incentive to implement energy efficiency retrofit project in existing coal-fuel power generation-units, and we hope it will make a good demonstration for the other low efficiency coal-fueled power generation units in China.

Fluorescent characteristic and compositional change of dissolved organic matter and its effect on heavy metal distribution in composting leachates

Composting leachates were collected to investigate the fluorescent characteristic and compositional change of dissolved organic matter (DOM) and the effects of the DOM and nutrients on heavy metal distribution during a leachate combination treatment process. Excitation-emission matrix (EEM) fluorescence spectra showed that, with the progress of the treatment units, the content of fulvic-like, humic-like, and protein-like substances gradually decreased. One fulvic-like component (C1), three humic-like components (C2, C3, and C4), and three protein-like components (C5, C6, and C7) were identified in the leachate DOM by parallel factor analysis. Anaerobic-aerobic processes removed a large fraction of the tyrosine-like component (C7) and tryptophan-like component (C6) and a small amount of humic-like component (C2), while the membrane bioreactor showed a good removal effect on protein-like component. The ultra-filtration membrane treatment had a removal effect on fulvic-like and humic-like component and other recalcitrant compounds, while the reverse osmosis treatment had a good removal effect on both humic-like and protein-like components. Correlation analysis indicated that Mn and Cr were primarily associated with protein-like components and nutrients in the composting leachates. Ni and Pb were bound to fulvic-like, humic-like, and protein-like components, Co and Zn interacted with inorganic nitrogen and total phosphorus, and Cd only interacted with inorganic nitrogen.

Study on Clean Development Mechanism, Quantitative and Sustainable Mechanism

Aiming at the system and market problem of clean development mechanism (CDM), this study is carried out to establish the feasibility of certified emission reduction (CER) quantitative evaluation method and reserve mechanism in host country at the United Nations Framework Convention on Climate Change (UNFCCC) level. After the introduction of CER quantitative and sustainable mechanism, the amount of CER that can enter the market was cut to a quarter, which reduces about 75% of the expected CER supply. Market CER from the technology types of higher CER market share and lower support for sustainable development appears to have different degrees of reduction. As for the technology types of lower CER market share and higher support for sustainable development, the amount of market CER is maintained in line with prevailing scenario, and market CER supply becomes more balanced.