Jianzhong Song

Feasibility of phytoextraction to remediate cadmium and zinc contaminated soils

A Cd and Zn contaminated soil was mixed and equilibrated with an uncontaminated, but otherwise similar soil to establish a gradient in soil contamination levels. Growth of Thlaspi caerulescens (Ganges ecotype) significantly decreased the metal concentrations in soil solution. Plant uptake of Cd and Zn exceeded the decrease of the soluble metal concentrations by several orders of magnitude. Hence, desorption of metals must have occurred to maintain the soil solution concentrations. A coupled regression model was developed to describe the transfer of metals from soil to solution and plant shoots. This model was applied to estimate the phytoextraction duration required to decrease the soil Cd concentration from 10 to 0.5 mg kg(-1). A biomass production of 1 and 5 t dm ha(-1) yr(-1) yields a duration of 42 and 11 yr, respectively. Successful phytoextraction operations based on T. caerulescens require an increased biomass production.

Chemical and Isotopic Composition of Humic-Like Substances (HULIS) in Ambient Aerosols in Guangzhou, South China

Humic-like substances (HULIS) constitute a class of organic compounds identified in atmospheric samples that influence many properties of aerosols in the atmosphere. In this study, 6 HULIS samples were isolated from atmospheric total suspended particle (TSP) samples collected at 3 locations in Guangzhou of China, 1 each in summer and winter. On the basis of analyses by elemental analyzer, more detailed chemical species of elements were explored by proton nuclear magnetic resonance (1H NMR) spectroscopy for hydrogen and X-ray photoelectron spectroscopy (XPS) for carbon, oxygen, nitrogen, and sulfur. The sources of HULIS were identified by carbon isotopic techniques. The results show that HULIS made up an important component of water-soluble organic carbon (WSOC). Carbon and oxygen were the predominant components in the HULIS. The 1H NMR spectra indicated that H functional groups consisted of aliphatic C‒H, aromatic C‒H, H‒C‒C˭, and H‒C‒O groups. They were all characterized by the highest contents of aliphatic protons and the lowest contents of aromatic protons. The XPS analysis of the HULIS fraction isolated from winter samples at the urban site Wushan (WS) showed that C, O, N, and S have various chemical states. The oxidized carbon groups accounted for 30.5% of total carbon. The nitrogen species contained amide, quaternary, and nitrate groups, and the sulfur species consisted of thiophenes, thioesters, mercaptanes, sulfones, and sulfates. The δ13C values of HULIS showed no obvious differences among the 6 HULIS samples. The δ15N values of summer HULIS samples in Maofengshan Mountain Forest Park (MFS) and Universities Town (UT) were significantly higher than those of winter samples. It is noteworthy that 14C data clearly indicate that even in urban areas biomass-derived carbon was the major component in the atmospheric HULIS samples. Copyright 2012 American Association for Aerosol Research

Novel use of soil moisture samplers for studies on anaerobic ammonium fluxes across lake sediment-water interfaces.

Small soil suction samplers have been used for several years to sample soil solution for chemical analysis in laboratory and glasshouse experiments. They are very cheap, effective and convenient. Here we describe for the first time their use in studies on sediment porewater. Bulk sediment from West Lake, a shallow hypereutrophic lake in Hangzhou, Zhejiang Province, China, was placed in laboratory microcosms and incubated in the dark at 25 degrees C for 182 days to evaluate the feasibility of using the samplers to extract sediment porewater and to estimate NH4+ flux across the sediment-water interface under anaerobic conditions. The results show that the samplers were capable of sequentially extracting sediment porewater, 15 ml of which could be readily extracted for analysis within 30-45 min by vacuum applied using a plastic syringe. The NH4+ flux under laboratory conditions was characterized by a fast phase during the initial 18 days of incubation followed by a slower linear phase, with average release rates of 11.6 and 3.6 mg N m(-2) d(-1), respectively.

Comparative study for separation of atmospheric humic-like substance (HULIS) by ENVI-18, HLB, XAD-8 and DEAE sorbents: Elemental composition, FT-IR, 1H NMR and off-line thermochemolysis with tetramethylammonium hydroxide (TMAH)

Humic-like substances (HULIS) are significant constituents of aerosols, and the isolation and characterization of HULIS by solid-phase extraction methods are dependent on the sorbents used. In this study, we used the following five methods: ENVI-18, HLB-M, HLB-N, XAD-8 and DEAE, to isolate atmospheric HULIS at an urban site. Then we conducted a comparative investigation of the HULIS chemical characteristics by means of elemental analysis, Fourier transform infrared spectroscopy, (1)H nuclear magnetic resonance spectroscopy and off-line thermochemolysis with tetramethylammonium hydroxide. The results indicate that HULIS isolated using different methods show many similarities in chemical composition and structure. Some differences were however also observed between the five isolated HULIS: HULISHLB-M contains a relatively high content of OCH group, compared to HULISENVI-18 and HULISXAD-8; HULISXAD-8 contains a relatively high content of hydrophobic and aromatic components, compared to HULISENVI-18 and HULISHLB-M; HULISDEAE contains the highest content of aromatic functional groups, as inferred by (1)H NMR spectra, but a great amount of salts generally present in the HULISDEAE and thereby limited the choices for characterizing the materials (i.e., elemental analysis and TMAH thermochemolysis); HULISHLB-N has relatively high levels of H and N, a high N/C atomic ratio, and includes N-containing functional groups, which suggests that it has been altered by 2% ammonia introduced in the eluents. In summary, we found that ENVI-18, HLB-M, and XAD-8 are preferable methods for isolation and characterization of HULIS in atmospheric aerosols. These results also suggest that caution is required when applying DEAE and HLB-N isolating methods for characterizing atmospheric HULIS.

Characterization of extractable and non-extractable polycyclic aromatic hydrocarbons in soils and sediments from the Pearl River Delta, China

Formation of bound residues of pollutants in soils and sediments is an important process to control the fate of pollutants in the environment. The most of bound residue is not solvent extractable. In this paper, we measured both extractable and non-extractable polycyclic aromatic hydrocarbons (PAHs) in different organic matter fractions of samples from the Pearl River Delta, China. Non-extractable PAHs concentration was 234.45-1424.57microg/kg and accounted for 33.78-57.44% of total PAHs. 2-3 Ring PAHs were the dominant species and differed in concentration substantially between the samples. The atomic ratio of PAHs over organic-C in the fractions ordered as solvent soluble organic matter>humin>humic acids, matching the content of aliphatic moieties in the fractions of organic matter. The ratio of extractable and non-extractable PAHs may relate to the aging process of PAHs in soil and sediment.

Humic Acid, Kerogen, and Black Carbon Isolated from Atmospheric Total Suspended Particulate from Guangzhou, China

The organic macromolecules in total suspended particulate (TSP) are complex and have not been thoroughly investigated. In this article, six composite TSP samples were collected from urban, suburban, and forest sites of Guangzhou. Organic macromolecules in the TSP were separated into humic acids (HA), kerogen and black carbon (KB), and black carbon (BC) by chemical treatment with sodium hydroxide, hydrochloric acid/hydrofluoric acid, and potassium dichromate/sulfuric acid. Note that the BC isolated is part of KB. To obtain sufficient amounts of HA, KB, and BC for subsequent analyses, 1.5 g TSP were used for each sample. The isolated fractions were characterized by elemental analysis, solid-state 13C crosspolarization and magic angle spinning nuclear magnetic resonance spectroscopy, Fourier transformed infrared spectroscopy, stable carbon isotopic ratio, and radiocarbon ratio mass spectrometry. Total carbon content in TSP ranged from 12.8 to 19.0%, and HA, KB, and BC were accounted for 2.39–14.8, 37.4–53.5, and 16.0–32.1% of total carbon, respectively. Isolated HAs were characterized by high H/C and N/C atomic ratios; KB showed high H/C but low N/C atomic ratios; BC was low in H/C, indicating a predominance of aromatic units in its carbon skeleton. The δ13C and radiocarbon data showed that all macromolecular fractions were mixtures of components having biogenic and fossil-fuel origins. The contribution of biogenic material to HA, KB, and BC, estimated by radiocarbon ratios, are 44.2–61.5%, 17.5–24.8%, and 3.3–17.2%, respectively. The atmospheric optical properties and hygroscopicity of kerogen are not known at present and warrant investigation because of the high content of kerogen in TSP. Copyright 2013 American Association for Aerosol Research

Molecular Characterization of Water-Soluble Humic like Substances in Smoke Particles Emitted from Combustion of Biomass Materials and Coal Using Ultrahigh-Resolution Electrospray Ionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

Water-soluble humic like substances (HULIS) in smoke particles emitted from combustion of biomass materials and coal were characterized by ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry. The formulas identified were classified into four main groups: CHO, CHON, CHOS, and CHONS. The average H/C and O/C ratios are 1.13-1.33, 1.01-1.13, 1.26-1.48, 1.09-1.24 and 0.21-0.41, 0.27-0.45, 0.41-0.46, 0.44-0.61 for the CHO, CHON, CHOS, and CHONS groups, respectively. The CHO compound was the predominant component (43%-72%) of the smoke HULIS from biomass burning (BB) and coal combustion, followed by the CHON group for BB-smoke HULIS and the S-containing groups (i.e., CHOS and CHONS) for coal-smoke HULIS. These results indicate that the primary HULIS emitted from biomass burning contain a high abundance of CHON species, which appear to be made up mainly of oxidized nitrogen functional groups such as nitro compounds and/or organonitrates. The coal-smoke HULIS contained more compounds with relatively low molecular weight and high aromaticity index (AImod). They were significantly enriched in S-containing compounds with high double bond equivalent (≥4), and O/S ratios suggest that they are most likely made up of aromatic organosulfates and nitrooxy organosulfates that are usually found in polluted atmospheres. These findings imply that the primary emissions from combustion of biomass and coal fuels are potential sources of water-soluble HULIS in an atmospheric matrix and that coal combustion is an especially important source of sulfate compounds.