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Abstract: Several soil samples were used to study how the characteristics of natural organic matter (NOM) affect sorption of organic compounds. These soils contains different amounts and types of NOM. Aromaticity of NOM (percentage of aromatic carbons) was determined from solid-state CPMAS [sup 13]C NMR spectra and the soil effective polarity was computed from the equation developed by Xing et al. Naphthalene was used to examine the sorption characteristics of NOM. Both aromaticity and polarity of NOM strongly affected sorption of naphthalene. Old NOM showed higher affinity than that in the surface, young soils. Sorption increased with increasing aromaticity and decreasing polarity. Thus, the sorption coefficients of organic contaminants cannot be accurately predicted without some consideration of NOM characteristics. [ABSTRACT FROM AUTHOR]

Two parallel digestion systems of food waste (FW) and waste-activated sludge (WAS) were successfully initiated using a continuous stirred-tank reactor (CSTR), and the effect of different reduction extents of sludge retention time (SRT) on the co-digestion of FW and WAS was investigated. SRT Reduction extents longer than 8.3 d were not conducive to the stable operation of the co-digestion system when the organic load rate (OLR) was increased. The reduction extent of SRT should be reduced gradually from 5 d to 0.9 d to achieve high load and stable operation of the co-digestion of FW and WAS. After a long-term operation (approximately 282 d), the co-digestion reached stable operation at SRT of 9.1 d and OLR (calculated by COD) of (12.9±1.5) g·(L·d) -1 . The corresponding methane production, methane yield (calculated by COD), pH, and volatile fatty acid (VFA, calculated by COD) were 3.94-4.25 L·(L·d) -1 , 288-302 mL·g -1 , 7.80-7.83, and 0.32-0.39 g·L -1 , respectively. Additionly, the sludge characteristics of the co-digestion of FW and WAS under a high loading rate were also investigated. The results showed that the primary pathway of methane conversion was through acetic acid during the co-digestion of FW and WAS. Meanwhile, higher methanogenic activity of acetic acid, propionic acid, butyric acid, valeric acid, and coenzyme F 420 concentration were also measured.

Intake of contaminated soils is considered as an important exposure pathway of polybrominated diphenyl ethers (PBDEs) to humans, especially for children during their outdoor hand-to-mouth activities. Oral bioaccessibility is an essential tool to quantitatively assess the exposure risk of pollutants. In this study, we employed an in vitro digestion model to mimic the gastrointestinal digestion of typical PBDEs (BDE-28, BDE-47, BDE-99 and BDE-153 at a series of initial concentrations) in three natural soil samples with different TOC contents and to verify a previous hypothesis that the sorption of PBDE fraction mobilized from soil into digestive fluid on the surface of residual solid phase may lead to an underestimation of bioaccessibility of PBDEs. In addition, a method with multiple fluid-to-solid ratios was applied to calibrate the underestimation. The results indicated that the calibrated digestibility values were commonly higher than those without correction. For the different soil samples, the averaged increasing rates of PBDE digestibility at different initial concentrations ranged from 14.3% to 42.3%, from 11.1% to 32.1%, from 4.9% to 12.3% and from 0.0% to 7.7% for BDE-28, BDE-47, BDE-99 and BDE-153, respectively. Therefore, the bioaccessibility of PBDEs in gastrointestinal gut would be significantly underestimated without calibration, especially for tri- and tetra-BDEs and soil samples with low TOC contents or high PBDEs concentrations. The corrected digestibility values of BDE-28, BDE-47, BDE-99 and BDE-153 were 21.9%-54.7%, 18.8%-43.1%, 13.4%-27.2% and 9.3%-19.9%, respectively. The results indicated that the PBDEs digestibility was negatively correlated with lgK(ow); whereas there was no significant correlation of PBDE bioaccessibility with TOC contents in soils or with initial concentrations of PBDEs, particularly for the highly brominated components.

With the rapid development of nanotechnology and widespread use of nanoproducts, ecotoxicity of engineered nanoparticles (NPs) attracts increasing attention and research. This paper reviews the ecotoxicity and mechanisms of NPs to aquatic organisms systematically. Toxic effects of different classes of NPs to bacteria, algae, invertebrates and fish in aquatic environments were firstly summarized, possible toxicity mechanisms were then expounded and the relationship between toxicity mechanisms and unique physicochemical properties of NPs was also analyzed. The processes of NPs uptake and membrane penetration at the cell and molecular level were discussed and presented. In the natural water, NPs behaviors are influenced by water chemistry conditions, so toxic effect to aquatic organisms is different from that in laboratory conditions, which should be paid with increased attention and effort. Finally, bottle-necks and challenges of NPs ecotoxicity research and existing problems of test and analytical methods were analyzed and the future directions of research were suggested.

In situ micro-suction cups were used to collect samples of soil solution with Arundo donax Linn and Typha latifolia from defined segments at rhizosphere in field. The experiment was conducted to elucidate the contribution of iron plaque while wetland plants were used to remove phosphorus. The reddish iron plaque was observed and measured on the surfaces of roots of Arundo donax Linn and Typha latifolia in the field, 20,170.8 mg/kg (fresh weight) for Arundo donax Linn and 7640.3 mg/kg (fresh weight) for Typha latifolia were collected. Olsen-P contents of Arundo donax Linn with iron plaque were 28.85 mg/kg, 46.2% more than that of without, 34.99 mg/kg for Typha latifolia 21.9% more than that of without. The phosphate concentrations in the in situ rhizosphere soil solution of Arundo donax Linn with iron plaque were 0.65 mg/kg, 9.2% more than that of without, 0.56 mg/kg for Typha latifolia, 33.9% more than that of without. The phosphorus contents adsorbed by iron plaque were 81.7% for Arundo donax Linn and 85.7% for Typha latifolia of the wetland plants with iron plaque. Phosphate use efficiency of Arundo donax Linn with iron plaque was 16.5% more than that of without, 31.4% for Typha latifolia. The contents of phosphorus of single plant of the two wetland plants with iron plaque are higher than that of without. Due to adsorb phosphate with iron plaque, the transfer speeds of phosphate from non-rhizosphere to rhizosphere and from soil to soil solution are increasing. The phosphorus contents with iron plaque accumulated at rhizosphere and depleted at rhizosphere without iron plaque of Arundo donax Linn and Typha latifolia.

The effects of nano-rutile TiO2 and multiwalled carbon nanotubes on the growth and antioxidant enzymes of maize (Zea mays L. ) seedlings were investigated under hydroponic conditions. Nano-rutile TiO2 ( > or =50 mg/L) significantly decreased root and shoot growth (p < 0.05) after 9 days, while MWCNTs did not influence the biomass obviously. Under two stress conditions, the antioxidant system was activated respectively. Compared to the control, superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) were up-regulated (p < 0.05). Lipid peroxidation in terms of malondialdehyde (MDA) content was enhanced by TiO2 exposure, whereas, MWCNTs did not cause oxidative damages in maize seedlings. The results indicated that the phytotoxicity of nano-rutile TiO2 was much higher than that of MWCNTs, and oxidative stress induced by nanoparticles (NPs) exposure might play a role in the phytotoxicity of NPs. The remarkable effect of nano-rutile TiO2 is probably attributed to particle composition and shape.

A mini-rhizotron experiment with Alternanthera philoxeroides and Typha latifolia was conducted to measure the spatial and temporal dynamics of phosphorus in the rhizosphere solution. The organic acids in the in situ rhizosphere soil solution were analyzed. A decreasing phosphorus concentration gradient in soil solution toward the root was observed for both A. philoxeroides and T. latifolia. The phosphorus concentration in the rhizosphere soil solution of A. philoxeroides (2.53 mg x L(-1)) was lower than that of T. latifolia (5.43 mg x L(-1)) in the forth sampling day. Compared to T. latifolia, A. philoxeroides released more malic acid (27.33 umol x L(-1)) which was more efficient in phosphorus mobilization. A. philoxeroides was more effective in phosphorus uptake in the rhizosphere than T. latifolia.