[Behaviors and Mechanisms of CIP and OFL Adsorption by Magnetic Biochar].

A magnetic reed biochar (MBC) was fabricated through chemical coprecipitation first and subsequent pyrolysis of reed stalk powder precipitated with Fe2+/Fe3+ at 873.15 K. The structure and properties of the MBC were characterized using SEM, BET, FTIR, and VSM. Adsorption experiments were carried out to investigate the adsorption behaviors and mechanisms of ciprofloxacin (CIP) and ofloxacin (OFL) onto the MBC. The MBC possessed roughness and pores within its structure and contained a large amount of oxygen-containing functional groups on the surface. The BET surface area of the MBC was 254.6 m2·g-1, and the total pore volume was 0.257 cm3·g-1, thus the MBC exhibited a relatively high porosity. The adsorption process was found to be pH and temperature dependent. The relative contributions of adsorbate species (cations, zwitterions, and anions) to overall adsorption varied for different pH values. Thermodynamic parameters indicated that the CIP and OFL adsorption onto MBC was a spontaneous, endothermic, and entropy-increasing process. Kinetics and isotherm data of CIP and OFL adsorption onto MBC were well depicted by the pseudo-second-order model and the Langmuir model. The equilibrium adsorption capacities of CIP and OFL onto MBC were 27.84 mg·g-1 and 22.00 mg·g-1, respectively. Pore-filling effects, π-π interaction between electron donors and acceptors, hydrogen bonding formation, hydrophobic interaction, and electrostatic interaction may be important mechanisms for CIP and OFL adsorption onto the MBC.

Combination of Unmix and PMF receptor model to apportion the potential sources and contributions of PAHs in wetland soils from Jiaozhou Bay, China.

16 PAHs in Jiaozhou Bay wetland soils were analyzed by GC/MS. The potential sources and contributions were apportioned by Unmix and PMF models. The total concentrations of PAHs ranged from 176.1 to 563.3 ng/g with a mean of 345.3 ng/g. 2- and 3- rings PAHs were the dominant species accounting for 34.7-87.3% of the total PAHs. The similarities and differences of sources and contributions estimated by Unmix and PMF models were discussed. Three common sources (petrogenic source, coking oven and coal combustion) identified by two models, contributed 43.2%, 39.2% and 12.6% by Unmix and 33.5%, 29.1% and 16.0% by PMF to the total PAHs, respectively. In addition, diesel emission source (5.0%) by Unmix and a mixed source of diesel emission and natural gas burning (21.4%) by PMF were also extracted. It is essential to apply multiple source apportionment techniques to estimate potential source and contributions in further study.

Combination of Unmix and positive matrix factorization model identifying contributions to carcinogenicity and mutagenicity for polycyclic aromatic hydrocarbons sources in Liaohe delta reed wetland soils, China.

Surface soils were collected from Liaohe delta, China, the largest reed wetland in the world dominated by common reed (Phragmites australis). Samples were analyzed for sixteen priority polycyclic aromatic hydrocarbons (PAHs) by GC/MS. The potential source patterns and source contributions to seven carcinogenic PAH congeners were performed by combining of Unmix and positive matrix factorization (PMF) model with the formula of toxic equivalent quantity (TEQ BaP) and mutagenic equivalent quantity (MEQ BaP), respectively. Four source categories, including petrogenic source, biomass burning, diesel emission and coal combustion, were identified by Unmix and PMF models. For both Unmix and PMF model, the mixed sources (gasoline and diesel engine emission) contributed the most to the TEQ BaP and MEQ BaP, while petrogenic source, the largest contributor for PAHs, made lower contribution to TEQ BaP and MEQ BaP. Minor source contribution difference was found between two models, which might be attributed to uncertainties model parameters and species variables. Hence, it is very essential to use combined source apportionment techniques for quantitatively identifying PAHs sources and estimated their carcinogenicity and mutagenicity.

Carcinogenic and mutagenic potencies for different PAHs sources in coastal sediments of Shandong Peninsula.

In this study, sources of PAHs in coastal sediments of Shandong Peninsula were apportioned using the chemical mass balance (CMB) model, and source apportionment of carcinogenic and mutagenic potencies was conducted combining CMB with the formula of benzo(a)pyrene carcinogenic equivalent (BaPTEQ) and BaP mutagenic equivalent (BaPMEQ) concentration. Total concentrations of sixteen PAHs in sediment ranged from 181.2 ng g(-1) to 303.6 ng g(-1), and concentrations of eight carcinogenic PAHs (cPAHs) varied from 98.8 ng g(-1) to 141.1 ng g(-1). The BaP played a dominant role for carcinogenic and mutagenic potencies of PAHs, although the IND showed the highest concentration level. The vehicular sources made the highest contribution to BaPTEQ (57.7%) and BaPMEQ (55.5%), while petrogenic source, the highest contributor for PAHs (39.4%), provided the lowest contribution to BaPTEQ (1.1%) and BaPMEQ (1.5%). Besides, the ecotoxicological evaluation, based on Sediment Quality Guidelines (SQGs), showed low ecological risks generally.

Source apportionment of PAHs using Unmix model for Yantai costal surface sediments, China.

16 Polycyclic aromatic hydrocarbons (PAHs) in 20 surface sediments from Yantai offshore area were measured. The total PAHs concentrations varied from 450.0 to 4,299.0 ng/g, with a mean of 2,492.9 ng/g. The high molecular weight (HMW) PAHs were most abundant and the ratio ranged from 54.9 % to 81.6 % in all sampling stations, indicating that pyrogenic sources were a predominant contribution to PAHs pollution. The source contributions of PAHs were estimated based on the EPA Unmix 6.0 receptor model. The data were well simulated due to a high correlation coefficient between predicted and measured PAHs concentration (R(2) = 0.99). A mixed source of coal combustion and traffic pollution contributed to 38.9 % of the measured PAHs, followed by diesel emission (38.8 %) and a mixed source of biomass combustion and gasoline engine emissions (22.3 %). The current findings further validated that Unmix model could be applied to apportion the sources of PAHs in sediments.

[Distribution and sources of PAHs in soil from Liaohe estuarine wetland].

16 polycyclic aromatic hydrocarbons (PAHs) were measured by GC-FID for 31 surface soil samples collected from Liaohe estuary wetland in October of 2008 and May and August of 2009. The results showed that the total concentrations of PAHs in surface soil ranged from 293.4 ng x g(-1) to 1936.9 ng x g(-1) with a mean of 851.5 ng x ng(-1). The contents of PAHs were the highest in the oilwell reed field and the lowest in the beach. The total concentrations of PAHs and proportion of median and high molecular weight of samples collected in October was higher than those collected in May and August. The relative abundance of different benzene rings and the ratio analysis illustrated that pyrolysis was the main source in October, and the mixed pollution of pyrogenic and oil spill was the dominant source in May and August. The principle component analysis-multiple linear regression analysis (PCA-MLR) indicated that the major source in October was coal/vehicular emission (accounted for 45.5%), and the mixture of vehicular exhaust and oil spill was the major source in May and August (accounted for 75.2% and 42.2% respectively).

Probabilistic ecological risk assessment and source apportionment of polycyclic aromatic hydrocarbons in surface sediments from Yellow Sea.

Based on the concentrations of polycyclic aromatic hydrocarbons (PAHs) in 12 surface sediment samples from Yellow sea, the relative risk of 9 PAHs was investigated using joint risk probability distribution curves and overlapping area, which were generated based on the distributions of exposure and acute toxicity data (LC(50)), and the sources of PAHs were apportioned using principal component analysis. It was found that joint probability curve and overlapping area indicated the acceptable ecological risk of individual PAHs, only a small fraction of the benthic organisms was affected. Among the nine PAHs studied, the overall risk of pyrene was the highest, with that of naphthalene the lowest. For lower exposure levels at which the percentage of species affected was less than 10%, the risk associated with phenanthrene and fluorene were clearly higher than that of the other seven PAHs. It was indicated that PAHs in surface sediments mainly originated from vehicular emissions, coal combustion sources, coke oven emission and wood combustion, petroleum origin made little influence on sources of PAHs by PCA.

[Effects of several low-molecular-weight organic acids on the release kinetic of DDTs from red soil].

The kinetic release behavior of DDTs from red soil with three kinds of low-molecular-weight (LMW) organic acids solution and water leaching was investigated by kinetic device designed. The results show that the release percentage of DDTs from red soil by LMW organic acid can increase by 15% - 18% more than that by water, especially for the initial 250 mL leaching solution. When using water as leaching solution, the data of release kinetics of DDTs from red soil conformed to the apparently first dynamics equation (R2 > 0.99, p < 0.000 1), it implied that the surface diffuse of soil mineral is primary release mechanism of DDTs from red soil in water leaching system. The kinetic release behavior of DDTs in LMW organic acid leaching system can be described by parabola diffuse equation, double constant equation or Elovich equation. It implied that the LMW organic acids induced the complication of the release mechanisms of DDTs from red soil, this maybe related to the dissolution of soil mineral surface and structure change of inherent organic material that coating onto the soil mineral surface induced by LMW organic acid.

Prediction of solvents extraction-the organochlorine pesticides in soil using solubility parameter.

Prediction of the optimal extraction solvent based on the solubility parameter to extract the typical organochlorine pesticides from Jiangxi red soil was reported in this paper. Hildebrand solubility parameters, including dispersion coefficient (delta(d)), polarity (delta(p)) and hydrogen bonding (delta(h)), of extraction solvents (including hexane, dichloromethane, hexane/methanol (4:1, v/v), hexane/acetone (1:1, v/v), hexane/dichloromethane (1:1, v/v) and organochlorine pesticides were calculated using group contribution method. The solvents, such as hexane/methanol (4:1, v/v) and hexane/acetone (1:1, v/v) were selected as ideal extraction solvents to extract o,p'-DDT o,p'-DDE and o,p'-DDD with high recoveries (>82%), furthermore, these solvents can be used to extract alpha-endosulfan, Endrin and HCB with the reliable recoveries (>75%). The estimated finding by solubility parameters was supported by the results of soxhlet extraction.