Phytoremediation is an effective method to remediate Pb-contaminated soils and root exudates play an important role in this process. Based on gas chromatography-mass spectrometry (GC-MS) and metabolomics method, this study focuses on the comparative metabolic profiling analysis of root exudates from the Pb-accumulating and non-accumulating ecotypes of Sedum alfredii treated with 0 and 50 μmol/L Pb. The results obtained show that plant type and Pb stress can significantly change the concentrations and species of root exudates, and fifteen compounds were identified and assumed to be potential biomarkers. Leaching experiments showed that l-alanine, l-proline and oxalic acid have a good effect to activate Pb in soil, glyceric acid and 2-hydroxyacetic acid have a general effect to activate Pb in soil. 4-Methylphenol and 2-methoxyphenol might be able to activate Pb in soil, glycerol and diethyleneglycol might be able to stabilize Pb in soil, but these activation effect and stabilization effect were all not obvious.

Hydroponic experiments were conducted to investigate the variation of root exudates from the hyperaccumulator Sedum alfredii under the stress of cadmium (Cd). S. alfredii was cultured for 4 days in the nutrient solution spiked with CdCl2 at concentrations of 0, 5, 10, 40, and 400 µM Cd after the pre-culture. The root exudates were collected and analyzed by GC-MS, and 62 compounds were identified. Of these compounds, the orthogonal partial least-squares discrimination analysis (OPLS-DA) showed that there were a distinct difference among the root exudates with different Cd treatments and 20 compounds resulting in this difference were found out. Changing tendencies in the relative content of these 20 compounds under the different Cd treatments were analyzed. These results indicated that trehalose, erythritol, naphthalene, d-pinitol and n-octacosane might be closely related to the Cd stabilization, phosphoric acid, tetradecanoic acid, oxalic acid, threonic acid and glycine could be attributed to the Cd mobilization, and mannitol, oleic acid, 3-hydroxybutanoic acid, fructose, octacosanol and ribitol could copy well with the Cd stress.

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This study investigated the spatial distribution, sources, and health risks of heavy metals (As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn) in agricultural topsoils in Fuxin, China. One-hundred and thirty-eight topsoil samples were collected from Fuxin in August 2017. Except for Cu, Hg, and Pb, the mean concentrations of other heavy metals surpassed their respective background values. The mean concentration of Cd was nine times that of the background value. For the majority of heavy metals, contents in the Haizhou and Xihe areas and south of Fumeng County were significantly higher than those of other areas. The results of the geoaccumulation and potential ecological risk indexes revealed that Cd demonstrated moderate contamination. The Haizhou and Xihe areas were considerable risk areas, whereas heavy metals in other areas posed low risks. Results of the health risk assessment revealed that the non-carcinogenic risks caused by heavy metals were small-beer. The carcinogenic risks caused by Ni, Cr, and As surpassed acceptable levels. Based on the results of source apportionment, which is based on positive matrix factorization, agricultural sources contributed to half of the concentration of heavy metals; industrial and traffic sources contributed 32.12% and 14.97%, respectively.

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The objectives of this study were to investigate the levels, dispersion patterns, seasonal variation, and sources of 16 priority polycyclic aromatic hydrocarbons (16 EPA-PAHs) in the Hun River of Liaoning Province, China. Samples of surface water were collected from upstream to downstream locations, and also from the main tributaries of the Hun River in dry period, flood period, and level period, respectively. After appropriate preparation, all samples were analyzed for 16 EPA-PAHs. Total PAHs concentrations varied from 124.55 to 439.27 ng l(-1) in surface water in dry period, 1,615.75 to 5,270.04 ng l(-1) in flood period, and 2,247.42 to 7,767.9 ng l(-1) in level period. The 16 EPA-PAHs concentrations were significantly increased in the order of level period > flood period > dry period. The composition pattern of PAHs in surface water was dominated by low molecular weight PAHs, in particular two- to three-ring PAHs. In addition, two-ring PAH accounted for 39.33 to 88.27 % of the total PAHs in level period. Low molecular weight PAHs predomination together with higher levels of PAHs in flood and level period suggested a relatively recent local source of PAHs. Special PAHs ratios such as phenanthrene/anthracene and fluoranthene/pyrene indicated that under dry weather season conditions, the PAHs found in surface water were primarily from petrogenic source, while under wet weather season conditions they were from mixed source of both petrogenic inputs and combustion sources. The comparison of PAHs contamination among different types of areas in China suggested that atmospheric depositions might be the most important approaches of PAHs into water system. Although the Hun River exists low PAHs ecological risk now, potential toxic effects will be existed in the future especially in flood and level period.

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Seventy-four soil samples from the road greenbelts, residential areas, drylands, waste grasslands, education lands, industrial areas, city parks, and rural homesteads of Shenyang city, China, were collected and analyzed for 13 organophosphate esters (OPEs). OPEs were detected in all analyzed soil samples, which indicate that OPEs are ubiquitously environmental contaminants. The ∑OPEs concentrations ranged from 0.039 to 0.95 mg/kg dry weight (dw), with the mean and median concentrations of 0.23 and 0.16 mg/kg dw, respectively. The pollution levels of OPEs in different land use types were different; the concentrations of OPEs in dryland soils were maximum and in city park soils were minimum. Of 13 OPEs, tri-iso-butyl phosphate (TiBP), tris-(1-chloro-2-propyl) phosphate (TCPP), tri-butoxyethyl phosphate (TBEP), and tris[2-chloro-1-(chloromethyl) ethyl] phosphate (TDCP) were the most abundant OPEs, contributing 42.0 ± 12.8, 12.4 ± 2.32, 6.31 ± 1.88, and 5.76 ± 1.86% of ∑OPEs, respectively. Principal component analysis (PCA) and absolute principal component score-multiple linear regression (APCS-MLR) suggested that OPE pollution in soils may be derived from atmospheric deposition, road runoff and vehicular traffic emission, and wastewater/reclaimed water irrigation and sludge application, their contributions were accounting for 62.4, 17.6, and 20.0%, respectively. As compared to the results from other studies, the pollution of OPEs in the urban soils of Shenyang is relatively serious.