Dainan Zhang

Biosorption of phenanthrene by pure algae and field-collected planktons and their fractions.

The biosorption isotherms for phenanthrene (Phen) by cultured algae, field-collected plankton, and market algae samples (OSs) and their fractions (lipid-LP, lipid free carbon-LF, alkaline nonhydrolyzable carbon-ANHC, and acid nonhydrolyzable carbon-NHC) were established. All the biosorption isotherms are well fitted by the Freundlich model. The biosorption isotherms for the ANHC and NHC fractions are nonlinear and for the other fractions are linear. It was found that the NHC fractions are chemically and structurally different from other fractions by using elemental analysis and Fourier transformed infrared spectroscopy (FTIR), consisting mainly of aliphatic polymethylene carbon. The average KOC values for Phen at Ce=0.005Sw are 10706±2768mLg(-1) and 95843±55817mLg(-1) for the bulk market algal samples and their NHC isolates, respectively. As the NHC fraction for Porphyra contains higher polymethylene carbon than that for Seaweed or Spirulina, it exhibits higher biosorption capacity. Moreover, the logKOC values are significantly higher for the field-collected samples than for the market algae and cultured algae samples. The multivariate correlation shows that the logKOC values are positively related to the LP contents, and negatively to the C/N ratios for the original algal samples. Furthermore, the logKOC values are negatively related to the polarity indices (O/C and O+N/C) for the original samples and their fractions excluding LP fractions. These observations help to understand the role of polarity, LP and NHC fractions, and aliphatic structures in the biosorption of Phen, which requires more attention in the examination of sorption processes in the natural environment.

Biosorption of nonylphenol by pure algae, field-collected planktons and their fractions

Algal samples were fractionated into lipid (LP), lipid free (LF), alkaline nonhydrolyzable carbon (ANHC), and acid nonhydrolyzable carbon (NHC) fractions, and were characterized by the quantitative (13)C multiCP NMR technique. The biosorption isotherms for nonylphenol (NP) were established and compared with previously published data for phenanthrene (Phen). The log KOC values are significantly higher for the field-collected plankton samples than for the commercial algae and cultured algae samples, correlating with their lipid contents and aliphatic carbon structure. As the NHC fraction contains more poly(methylene) carbon, it exhibits a higher biosorption capacity. The sorption capacities are negatively related to the polarity index, COO/N-C=O, polar C and O-alkyl C concentrations, but are positively related to the H/O atomic ratios and poly(methylene) carbon. The higher sorption capacities observed for NP than for Phen on the investigated samples are explained by specific interactions such as hydrogen bonding and π-π interaction.

Novel Phenanthrene Sorption Mechanism by Two Pollens and Their Fractions

A pair of pollens (Nelumbo nucifera and Brassica campestris L.) and their fractions were characterized by elemental analysis and advanced solid-state (13)C NMR techniques and used as biosorbents for phenanthrene (Phen). Their constituents were largely aliphatic components (including sporopollenin), carbohydrates, protein, and lignin as estimated by (13)C NMR spectra of the investigated samples and the four listed biochemical classes. The structure of each nonhydrolyzable carbon (NHC) fraction is similar to that of sporopollenin. The sorption capacities are highly negatively related to polar groups largely derived from carbohydrates and protein but highly positively related to alkyl carbon, poly(methylene) carbon, and aromatic carbon largely derived from sporopollenin and lignin. The sorption capacities of the NHC fractions are much higher than previously reported values, suggesting that they are good sorbents for Phen. The Freundlich n values significantly decrease with increasing concentrations of poly(methylene) carbon, alkyl C, aromatic moieties, aliphatic components, and the lignin of the pollen sorbents, suggesting that aliphatic and aromatic structures and constituents jointly contribute to the increasing nonlinearity. To our knowledge, this is the first investigation of the combined roles of alkyl and aromatic moiety domains, composition, and accessibility on the sorption of Phen by pollen samples.

Distribution and partitioning of polybrominated diphenyl ethers in sediments from the Pearl River Delta and Guiyu, South China

Polybrominated diphenyl ethers (PBDEs) were investigated by GC-NCI-MS in sediments collected from the Pearl River Delta (PRD) and Guiyu town, South China. The concentrations of ∑39PBDEs and BDE 209 were in the ranges of 0.31-38.9 ng g-1 and 12.2-488 ng g-1 in the PRD, and 2.57-21,207 ng g-1 and 7.02-66,573 ng g-1 in Guiyu, respectively. The levels of PBDEs in Dongjiang River (DJ), Zhujiang River (ZJ), and Beijiang River (BJ), and Guiyu (GY) followed the order: GY > DJ > ZJ > BJ. The very high PBDE concentration (87,779 ng g-1) was detected at G1 sediment in Guiyu compared with those in sediments from other regions around the world. The PBDE mixtures detected were mainly comprised of penta-, octa-, and deca-BDEs, in which deca-BDE was the dominant constituent. The abundant congeners, excluding BDE-209, were BDE-47, BDE-99, and BDE-183, suggesting the diverse use of commercial products containing these congeners in this region. The concentrations of major congeners were significantly correlated with total organic carbon (TOC) contents (p < .01). A good regression between the logarithmic TOC-normalized BDE average concentrations and their log Kow confirmed that the sorption of PBDEs on sediment organic matter governed their spatial distribution, transport, and fate in the sediments. Furthermore, risk quotients (RQs) derived from concentrations of PBDEs in sediments from our study may pose high ecological risks to exposure of benthic organisms.

Nanopore-filling effect of phenanthrene sorption on modified black carbon

Black carbon was produced by slow pyrolysis under an oxygen-limited condition at 500 °C, and was modified by some chemical methods (oxidation, hydrolysis, activation, and surface recombination). The modified samples were characterized by using elemental analysis, Fourier transformed infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) surface analysis, Boehm titration, cation exchange capacity(CEC)analysis, CO2 adsorption analysis, and then used to investigate the sorption behavior of phenanthrene. The results showed that the activation of ZnCl2 gave a maximum nanopore volume of 96.5 μL/g and a specific surface area of 241 m2/g, while the oxidation of NaClO gave a minimum nanopore volume of 63.3 μL/g and a specific surface area of 158 m2/g. The FTIR, XPS, and Boehm titration analysis showed that the new oxygen-containing functional groups were introduced during the oxidation treatments of H2O2 and NaClO. The sorption of phenanthrene on all samples was typically nonlinear, and the nonlinear factor (n) was negatively correlated with Vo, especially with Vo at 0-1.1 nm. The sorption parameter (log KOC) was positively correlated with nanopore volume (Vo) and specific surface area (SSA). Moreover, the model analysis showed that the nanopore filling was the main sorption mechanism, and molecular sieve effect was observed in the sorption of phenanthrene.

Composition and structure of natural organic matter through advanced nuclear magnetic resonance techniques

Natural organic matter (NOM) plays important roles in biological, chemical, and physical processes within the terrestrial and aquatic ecosystem. Despite its importance, a clear and exhaustive knowledge on NOM chemistry still lacks. Aiming to prove that advanced solid-state 13C nuclear magnetic resonance (NMR) techniques may contribute to fill such a gap, in this paper we reported relevant examples of its applicability to NOM components, such as biomass, deposition material, sediments, and kerogen samples. It is found that nonhydrolyzable organic carbons (NHC), chars, and polymethylene carbons are important in the investigated samples. The structure of each of the NHC fractions is similar to that of kerogens, highlighting the importance of selective preservation of NOM to the kerogen origin in the investigated aquatic ecosystems. Moreover, during the artificial maturation experiments of kerogen, the chemical and structural characteristics such as protonated aromatic, nonprotonated carbons, and aromatic cluster size play important roles in the origin and variation of nanoporosity during kerogen maturation.Graphical abstractNMR parameters of thermally stimulated kerogens

Source, composition, and environmental implication of neutral carbohydrates in sediment cores of subtropical reservoirs, South China

Neutral monosaccharides, algal organic matter (AOM), and carbon stable isotope ratios in three sediment cores of various trophic reservoirs in South China were determined by high-performance anion-exchange chromatography, Rock-Eval pyrolysis, and Finnigan Delta Plus XL mass spectrometry, respectively. The carbon isotopic compositions were corrected for the Suess effect. The concentrations of total neutral carbohydrates (TCHO) range from 0.51 to 6.4 mgg−1 at mesotrophic reservoirs, and from 0.83 to 2.56 mgg−1 at an oligotrophic reservoir. Monosaccharide compositions and diagnostic parameters indicate a predominant contribution of phytoplankton in each of the three cores, which is consistent with the results inferred from the corrected carbon isotopic data and C/N ratios. The sedimentary neutral carbohydrates are likely to be structural polysaccharides and/or preserved in sediment minerals, which are resistant to degradation in the sediments. Moreover, the monosaccharide contents are highly related to the carbon isotopic data, algal productivity estimated from the hydrogen index, and increasing mean air temperature during the past 60 years. The nutrient input, however, is not a key factor affecting the primary productivity in the three reservoirs. The above evidence demonstrates that some of the resistant monosaccharides have been significantly elevated by climate change, even in low-latitude regions.