[Research and Application Progress of Biochar in Amelioration of Saline-Alkali Soil].

Saline-alkali land， as one of the farmland problems that seriously threatens grain yield in the 21st century， is widely distributed and has great potential for development. Biochar is a relatively efficient novel soil amendment， which can play an important role in alleviating the soil acid-base barrier， soil pollution control， carbon sequestration， and fertilizer slow release and has a great prospect in promoting sustainable agricultural development. In recent years， the research and application of biochar to improve saline-alkali soil have attracted much attention. However， due to the complexity and heterogeneity of the structural components of biochar， the improvement effect of biochar on saline-alkali soil is highly uncertain， and there is also a lack of systematic summary and in-depth discussion of the key mechanisms， which limits the further popularization and application of biochar technology in the improvement of saline-alkali soil. This study comprehensively analyzed the effects of biochar on physicochemical properties， nutrient availability， and biological characteristics of saline-alkali soil； summarized the improvement effects of biochar and modified biochar on saline-alkali soil and their effects on quality and efficiency； and elucidated the possible mechanism of biochar in the improvement of saline-alkali soil. The future research prospect of biochar was discussed in order to provide reference for further research and development of green， efficient， and accurate improvement technology of biochar in saline-alkali soil and its popularization and application.

[Advances in Microbial Degradation and Transformation of Per- and Polyfluoroalkyl Substances(PFASs)].

Per- and polyfluoroalkyl substances (PFASs) have attracted extensive attention because of their persistence, long-distance migration ability, bioaccumulation, and biological toxicity. Currently, regulatory strategies concerning PFASs in the environment primarily focus on perfluoroalkyl acids (PFAAs). However, most polyfluoroalkyl compounds can be degraded to PFAAs by environmental microorganisms, also known as precursors. Exploring the microbial transformation behavior of precursors is fundamental to comprehensively evaluate the environmental risk of PFASs and formulate control and remediation schemes of PFAS-contaminated sites. Furthermore, anaerobic microbial reductive defluorination of PFAAs is a potential and challenging remediation technology. This review summarizes degradation rules and transformation pathways of precursors (fluorotelomer compounds and perfluorooctane sulfonamide derivatives), PFAAs, and novel PFASs by microorganisms and discusses factors affecting the microbial degradation. Finally, the future research directions are put forward.

[Jiawei Baitouweng Decoction affects intestinal mucosal tight junction proteins in rats with ulcerative colitis through p38 MAPK-MLCK signaling pathway].

The aim of this paper was to explore the effect and mechanism of Jiawei Baitouweng Decoction(JWBTW) against ulcerative colitis(UC) from the perspective of intestinal mucosal tight junction proteins. From 60 SPF-grade male SD rats, 10 were randomly selected as the blank control, and the remaining 50 were treated with 3% dextran sodium sulfate(DSS) solution to induce UC and then randomized into the model group, mesalazine group, and low-, medium-, and high-dose JWBTW( L-JWBTW, M-JWBTW and H-JWBTW) groups, with 10 rats in each group. After successive medication for 14 days, the rat general conditions like body weight and stool were observed and the disease activity index(DAI) was calculated. The pathological changes in colon tissue was observed under a microscope for injury severity scoring and histopathological scoring. The serum endotoxin content was determined by limulus assay, followed by the measurement of protein expression levels of ZO-1, occludin, claudin-1, p38 MAPK, MLCK, MLC2 and p-MLC in colon tissue by Western blot. The results showed that compared with the blank group, the model group exhibited significantly reduced body weight, elevated DAI, injury severity and histopathological scores and serum endotoxin content, up-regulated protein expression levels of p38 MAPK, MLCK, MLC2 and p-MLC, and down-regulated ZO-1, occludin and claudin-1. Compared with the model group,mesalazine and JWBTW at each dose obviously increased the body weight, lowered the DAI, injury severity and histopathological scores and serum endotoxin content, down-regulated the protein expression levels of p38 MAPK, MLCK, MLC2 and p-MLC, and up-regulated the ZO-1, occludin and claudin-1, with the most obvious changes noticed in the H-JWBTW group. All these have indicated that JWBTW exerts the therapeutic effect against UC by inhibiting the activation of p38 MAPK/MLCK pathway, reversing the protein expression levels of occludin, claudin-1 and ZO-1, decreasing the serum endotoxin content, promoting the repair of intestinal mucosal mechanical barrier, maintaining the integrity of tight junctions, and reducing the permeability of intestinal mucosa.

Pingkui Enema Alleviates TNBS-Induced Ulcerative Colitis by Regulation of Inflammatory Factors, Gut Bifidobacterium, and Intestinal Mucosal Barrier in Rats.

BACKGROUND: Ulcerative colitis (UC) is a chronic recurrent inflammation of the colon, and clinical outcome of UC is still unsatisfied. Pingkui enema, a traditional Chinese medicine prescription, has been safely applied for the treatment of diarrhea and dysentery in clinic for many years. However, its mechanism is still elusive. The present study is designed to investigate the effect of Pingkui enema on trinitrobenzene sulfonic acid- (TNBS-) induced ulcerative colitis (UC) and possible mechanism in rats. METHODS: UC was induced by intracolonic instillation of TNBS in male Sprague-Dawley rats, which were treated with different dosages of Pingkui enema (low, medium, and high) or sulfasalazine for ten days. Survival rate was calculated. A clinical disease activity score was evaluated. Histological colitis severity was analyzed by hematoxylin-eosin (HE) staining. Content of Bifidobacterium in intestinal tissue was analyzed by RT-PCR. Concentration of IL-8, IL-13, TNF-α, D-lactic acid (D-LA), and diamine oxidase (DAO) in serum and contents of adhesin and receptor of Bifidobacterium adhesion in rat intestinal mucus were measured by ELISA. RESULTS: The results showed that Pingkui enema treatment with high dosage markedly improved the survival rate compared with untreated and sulfasalazine treated groups. All dosages of Pingkui enema reduced pathological score. High dosage of Pingkui enema and sulfasalazine treatments significantly reduced the serum concentration of IL-8, TNF-α, D-LA, and DAO and markedly increased the serum concentration of IL-13. In addition, high-dose Pingkui enema and sulfasalazine treatments increased gut content of Bifidobacterium, gut mucus expressions of adhesin, and adhesin receptor of Bifidobacterium. CONCLUSIONS: Pingkui enema has therapeutic effect on TNBS-induced UC, and possible mechanism may be via regulation of gut probiotics (Bifidobacterium) and inflammatory factors and protection of intestinal mucosal barrier.

[Distribution and Fluxes of Perfluoroalkyl and Polyfluoroalkyl Substances in the Middle Reaches of the Yellow River (Weinan-Zhengzhou Section)].

Surface water samples were collected in the middle reaches of the Yellow River (Weinan-Zhengzhou section) and all 28 perfluoroalkyl and polyfluoroalkyl substance (PFAS) levels were measured using high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The results show that the levels of PFASs in the water and particle phase are 18.4-56.9 ng·L-1 and 26.8-164 ng·g-1, respectively. Perfluorohexanoic acid (PFHxA) in the water and particle phases is the main pollutant, accounting for 27% and 16% of the total concentrations, respectively, and 3H-perfluoro-3-[(3-methoxy-propoxy)-propanoate] acid (ADONA) and chlorinated polyfluorinated ethersulfonic acids (6:2 and 8:2 Cl-PFESA) were detected in the particle phase, indicating that the use of PFAS alternatives gradually increases. The lgKd of PFASs between the water and particle phase ranges from 2.95±0.553 (PFPeA) to 3.85±0.237 (8:2 FTUCA)and the adsorption of fluorotelomer carboxylic acids (FTCAs) and fluorotelomer unsaturated carboxylic acids (FTUCAs) on particulate matter increases with increasing of carbon chain length. Perfluoroalkane sulfonic acids (PFSAs) are more easily adsorbed by particulate matter than perfluoroalkyl carboxylic acids (PFCAs). The fluxes of PFASs in the Weinan-Zhengzhou section of the Yellow River show a decrease at first and then increase, indicating that this section receives pollution inputs from the upstream and tributaries. In addition, the results show that the fluxes of PFASs in the water phase are greater than those in the particle phase.

Aerobic degradation of trichloroethylene by co-metabolism using phenol and gasoline as growth substrates.

Trichloroethylene (TCE) is a common groundwater contaminant of toxic and carcinogenic concern. Aerobic co-metabolic processes are the predominant pathways for TCE complete degradation. In this study, Pseudomonas fluorescens was studied as the active microorganism to degrade TCE under aerobic condition by co-metabolic degradation using phenol and gasoline as growth substrates. Operating conditions influencing TCE degradation efficiency were optimized. TCE co-metabolic degradation rate reached the maximum of 80% under the optimized conditions of degradation time of 3 days, initial OD600 of microorganism culture of 0.14 (1.26×107 cell/mL), initial phenol concentration of 100 mg/L, initial TCE concentration of 0.1 mg/L, pH of 6.0, and salinity of 0.1%. The modified transformation capacity and transformation yield were 20 µg (TCE)/mg (biomass) and 5.1 µg (TCE)/mg (phenol), respectively. Addition of nutrient broth promoted TCE degradation with phenol as growth substrate. It was revealed that catechol 1,2-dioxygenase played an important role in TCE co-metabolism. The dechlorination of TCE was complete, and less chlorinated products were not detected at the end of the experiment. TCE could also be co-metabolized in the presence of gasoline; however, the degradation rate was not high (28%). When phenol was introduced into the system of TCE and gasoline, TCE and gasoline could be removed at substantial rates (up to 59% and 69%, respectively). This study provides a promising approach for the removal of combined pollution of TCE and gasoline.

The bioconcentration and degradation of nonylphenol and nonylphenol polyethoxylates by Chlorella vulgaris.

Nonylphenol polyethoxylates (NPnEOs), a major class of nonionic surfactants, can easily enter into aquatic environments through various pathways due to their wide applications, which leads to the extensive existence of their relative stable metabolites, namely nonylphenol (NP) and mono- to tri-ethoxylates. This study investigated the bioconcentration and degradation of NP and NPnEO oligomers (n = 1-12) by a green algae, Chlorella vulgaris. Experimental results showed that C. vulgaris can remove NP from water phase efficiently, and bioconcentration and degradation accounted for approximately half of its loss, respectively, with a 48 h BCF (bioconcentration factor) of 2.42 × 10(3). Moreover, C. vulgaris could concentrate and degrade NPnEOs, distribution profiles of the series homologues of the NPnEOs in algae and water phase were quite different from the initial homologue profile. The 48 h BCF of the NPnEO homologues increased with the length of the EO chain. Degradation extent of total NPnEOs by C. vulgaris was 95.7%, and only 1.1% remained in water phase, and the other 3.2% remained in the algal cells. The algae removed the NPnEOs mainly through degradation. Due to rapid degradation, concentrations of the long chain NPnEO homologous in both water (n ≥ 2) and the algal phase (n ≥ 5) was quite low at the end of a 48 h experiment.

[Bioremediation of PAHs contaminated soil from Beijing coking plant by Lasiodiplodia theobromae].

Bioremediation of PAHs contaminated soil from Beijing Coking Plant was performed using a novel fungal strain Lasiodiplodia theobromae (L. theobromae). Moreover, enhanced bioremediation of PAHs contaminated soil was investigated in the presence of different concentrations of Tween 80 and hydroxypropyl-beta-cyclodextrin (HPCD). The correlation of the dynamics of enzyme activities during remediation and the degradation of PAHs was analyzed. The results showed that the degradation rate of PAHs increased to 45.3% on the 70th day after addition of L. theobromae, which was 30 percentage points higher than that of the control group. At an optimum concentration of 2 g x kg(-1) for Tween 80 and 1 g x kg(-1) for HPCD, the degradation rate of PAHs was enhanced to 65.8% and 63.9%, respectively, which was 50 percentage points higher than that of the control group. Hydrogen peroxidase and invertase activities in soil in the bioremediation group with only L. theobromae and the surfactant enhanced group were both enhanced twice more than that of the control group. These results showed that L. theobromae may produce hydrogen peroxidase and invertase or have synergic effect with indigenous microorganisms. Correlation analysis showed that the correlation coefficients of PAHs degradation rate and maximum enzyme activities of hydrogen peroxidase and invertase were 0.781 and 0.837, respectively. Therefore, the correlation between invertase activities and degradation rate was higher.

[Effects of pH and Ni2+ on sorption behavior of phenanthrene on engineered nano-silica].

In order to reveal the sorption behavior of phenanthrene (PHE) on engineered nano-silica, batch equilibriums were conducted to study the effects of heating, solution pH, and heavy metal ion (Ni2+) on PHE sorption, and a site energy distribution model was used to analyze the changes of sorption behavior. The results demonstrated that the sorption isotherm of PHE could be fitted well by the Freundlich model. The sorption capacity of the original nano-silica (PNS) was enhanced by heating (heated nano-silica, HNS), with the Freundlich adsorption coefficient (lgK(F)) increasing from 1.48 to 2.43. The nonlinearity of sorption isotherm increased after heating. The sorption characteristics together with pore distribution and surface area analysis suggested that PHE sorption on nano-silica was a combination of pore-filing and surface sorption, with the microspores and mesopores of nano-silica playing a major role. While changes in solution pH did not show a significant effect on the sorption of PHE on PNS, the sorption of PHE on HNS decreased significantly with increasing pH, with IgK(F) reducing by 73.7% when pH increased from 4.0 to pH 8.0. The pH caused differences in sorption capacity could be mainly explained by zeta potentials of nanoparticles. High pH enhanced the charge of nanoparticles, and reduced the pore accessibility. The effect of Ni2+ on PHE sorption on HNS varied with its concentration. At low concentration (<5 mmol x L(-1)), Ni2+ suppressed PHE sorption, while at a higher concentration, NiZ2 enhanced the sorption of PHE at a lower concentration (50 microg x L(-1)), and the inhibition on the sorption of PHE at a higher concentration (500 microg x L(-1)) did not increase further. This complex pattern was a result of concurrence of multiple processes.

[Isolation of highly-effective benzo[a]pyrene degrading strain and its degradation capacity].

One new mycete, which could degrade high concentration (up to 100 mg/L) of benzo[a]pyrene (BaP) in liquid, was isolated from contaminated soil of Beijing Coking Plant by gradually increasing the concentration of BaP in mineral salt medium (MSM) in order to get new microorganism species for remediation of BaP contamination. The strain was identified as Lasiodiplodia theobromae, and its biodegradation ability in liquid was further investigated. The results showed that L. theobromae could utilize BaP as sole carbon and energy sources. The experiment was conducted for 10 days, and the biodegradation rate of BaP was 52.5% +/- 1.5%. Compared to Czapek's mineral medium, MSM was more suitable for L. theobromae, and biodegradation rate was 2.8 percent greater than that by using Czapek's mineral media after 10 days' cultivation. Potato-dextrose nutrient medium could accelrate the biodegradation in early stage, and biodegradation rate of BaP increased by 19.2 percent in the second day. However, the accelration was not significant in the latter period, biodegradation rate was only increased by 5.4 percent after 10 days' cultivation. L. theobromae could tolerate a wide pH range, with the optimum pH of 5. Addition of salicylic and sodium succinate enhanced the biodegradation rates by 6.2 percent and 4.2 percent, respectively, after 10 days' cultivation. Besides BaP, L. theobromae could also degrade high concentration (200 mg/L) of phenanthrene and pyrene, and the biodegradation rates were 70.0% +/- 1.0%, 59.2% +/- 3.2%, and 52.5% +/- 1.5% when they were single substrate and were 21.6% +/- 2.1%, 14.5% +/- 5.5%, and 11.9% +/- 2.2% when they existed in mixture, respectively. The biodegradation rate followed an order of phenanthrene > pyrene > BaP. The co-existence of the three substrates led a reduction in biodegradation. This study provides a new microorganism species for remediation of polycyclic aromatic hydrocarbons (PAHs) contamination in the environment.

[Extraction of main constituents from rice straw and their sorption of pyrene].

Main constituents (lignin, cellulose and hemicelullose) were extracted from rice straw, and characterized by elemental analysis and Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFT). Sorption of pyrene on rice straw and its main constituents was studied. The results showed that there are great differences in the properties of the three constituents, with lignin of higher aromaticity and lower polarity, while cellulose and hemicellulose of greater polarity and aliphaticity. Sorption of pyrene also differed a lot due to the varied characteristics of the sorbents. All isotherms were fitted well with Freundlich equation. Lignin showed the greatest sorption capacity for pyrene, with K(F) being 5.04 x 10(4), approximately 100 times greater than that of cellulose. Sorption of pyrene on hemicellulose was even a little smaller than that on cellulose. At low solute aqueous concentration (c(e) = 0.01 S(w)), the sorption of pyrene on rice straw was controlled by lignin, and sorption coefficient (K(d)) was a little smaller than that predicted by the K(d) value on lignin and its mass fraction. This suggested that some sorption sites such as alkyl and aromatic centers were covered when the lignin existed mixed in the rice straw. But at high concentration (c(e) = 0.5 S(w)), the K(d) value of pyrene on rice straw was markedly greater than the sum of those on three constituents, suggesting that partition on other constituents could not be neglected. Moreover, pyrene sorption isotherm on lignin was nonlinear (Freundlich exponent, n = 0.89), while sorption on the other three sorbents was more linear (n > 0.96). A negative relationship between n and aromaticity was observed, which illustrates that specific effect related with aromaticity is the main reason for nonlinearity. Organic carbon normalized sorption coefficients (K(oc)) increased with increasing aromaticity and decreased with increasing polarity of the sorbents.

Perchlorate and iodide in whole blood samples from infants, children, and adults in Nanchang, China.

Perchlorate, ClO(4)(-), interferes with iodide (I(-)) uptake by the sodium-iodide symporter (NIS) and thereby affects thyroid hormone production in the body. Studies have reported human exposures to perchlorate based on measurements in urine, but little is known about the levels in blood. In this study, we determined concentrations of perchlorate, iodide, and other anions (e.g., chlorate [ClO(3)(-)], bromate [BrO(3)(-)], bromide [Br(-)]) in 131 whole blood samples collected from Chinese donors aged 0.4 to 90 yr, in Nanchang, China. Perchlorate, iodide, and bromide were detected in all of the samples analyzed, whereas chlorate was found in only 27% of the samples and bromate was found in only 2%. The mean (range) concentrations of perchlorate, iodide, and bromide were 2.68 (0.51-10.5), 42.6 (1.58-812), and 2120 (1050-4850) ng/mL, respectively. Perchlorate levels in blood from Nanchang adults were 10-fold greater than levels that have been previously reported for U.S. adults. The iodide/perchlorate molar ratio ranged from 3.05 to 15.3 for all age groups, and the ratio increased with age (r = 0.732, p < 0.01). Perchlorate and bromide concentrations decreased significantly with age, whereas iodide concentrations increased with age. No significant gender-related differences in blood perchlorate, iodide, or bromide levels were found. A significant negative correlation was found between the concentrations of perchlorate and iodide in blood. Exposure doses of perchlorate were estimated for infants, toddlers, children, adolescents, and adults based on the measured concentrations in blood, using a simple pharmacokinetic model. The mean exposure doses of perchlorate for our age groups ranged from 1.12 (adults) to 2.22 µg/kg bw/day (infants), values higher than the United States Environmental Protection Agency's (USEPA) reference dose (RfD: 0.7 µg/kg bw/day). This is the first study on perchlorate and iodide levels in whole blood from infants, toddlers, children, adolescents, and adults from a city in China with known high perchlorate levels.

[Bioturbation of macrobenthos on estuarine sediment].

By using microcosm tracer technique, the bioturbation of macrobenthos Helice tientsinensis, Nereis diversicolor, Bullacta exarata, and Cyclina sinensis on the sediment in Beitang Estuary of Tianjin, China was quantitatively studied. The bioturbation of test macrobenthos had obvious effects on the distribution of the sediment, and the effects differed with the macrobenthos. The disturbed intensity (diffusion coefficient, 10(-3) cm2 x d(-1)) of surface sediment under the effects of the macrobenthos was in order of N. diversicolor (2.95) > H. tientsinensis (1.00) > C. sinensis ( 0.78) > B. exarata. (0.35) > control (0.05), and that of deep sediment was H. tientsinensis (3.10) > N. diversicolor (2.33) > C. sinensis (0.28) > B. exarata (0.15) > control (0.05), which was mainly due to that the macrobenthos were belonged to different functional groups. There was a significant relationship between the bio-volume of test macrobentos and the diffusion coefficient of surface sediment (P < 0.05), suggesting that the bio-volume of macrobenthos could be used as an indicator to predict their bioturbation capacity on esturaine sediment.

Perfluorinated compounds in whole blood samples from infants, children, and adults in China.

Two hundred and forty five human blood (whole blood) samples from Chinese donors aged from 0 to 90 yrs were analyzed for 10 perfluorinated compounds (PFCs). Perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) were the most abundant PFCs found in blood. The median concentration of PFOS was lower in nonadults (i.e., infants, toddlers, children, and adolescents) (2.52-5.55 ng/mL) than in adults (8.07 ng/mL). However, median concentration of PFOA in nonadults (1.23-2.42 ng/mL) was higher than that found in adults (1.01 ng/mL). A significant increase in PFOS (r = 0.468, p < 0.01) and perfluorohexane sulfonate (PFHxS) (r = 0.357, p < 0.01) concentrations with age was found, while PFOA concentrations (r = -0.344, p < 0.01) were negatively correlated with age. No significant gender-related differences in PFC concentrations were found across all ages. The composition profiles of PFCs, as identified by principal component analysis, varied for each age group; this suggested differences in sources and pathways of exposure to PFCs for different age groups. Based on the blood PFC concentration, we estimated the daily intake of PFOS by adults using a one-compartment toxicokinetic model. The modeled daily intake of PFOS agreed well with the calculated daily intake via diet and indoor dust (0.74 vs 1.19 ng/kg b.w. for males, 1.20 vs 1.15 ng/kg b.w. for females) suggesting that dietary intake and dust ingestion are the major exposure routes to PFOS exposure in China. This is the first comprehensive study on PFCs in human blood from infants, toddlers, children, and adolescents in China. The data are valuable for understanding the sources and pathways of human exposure to PFCs for different age groups.

Perfluorochemicals in meat, eggs and indoor dust in China: assessment of sources and pathways of human exposure to perfluorochemicals.

In this study, 10 perfluorochemicals (PFCs) were measured in meat, meat products, and eggs, and in indoor dust, collected in China. Perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) were the most frequently detected PFCs in these samples. Mean concentrations of PFOS and PFOA in foodstuffs were in the range of 0.05-1.99 ng/g fresh wt and 0.06-12.5 ng/g fresh wt, respectively. The mean concentrations of PFOA, perfluoroheptanoic acid (PFHpA), and PFOS in indoor dust were 205, 14.0, and 4.86 ng/g, dry wt, respectively. The estimated daily intake of PFOS and PFOA from meat, meat products and eggs (EDI(meat&eggs)) ranged from 6.00 to 9.64 ng/d and from 254 to 576 ng/d, respectively, when the values below the limit of quantitation (LOQ) were assigned as 0, and from 8.80 to 15.0 ng/d and from 255 to 577 ng/d, respectively, when the values below the LOQ were set at 1/2LOQ. The EDI(meat&eggs) of PFOS and PFOA increased with increasing family income. The estimated daily intake of PFOS and PFOA through inhalation of dust (EDI(dust)) ranged from 0.23 to 0.31 ng/d and from 9.68 to 13.4 ng/d, respectively. The daily intakes of PFOS and PFOA from the consumption of meat, meat products, and eggs, and from dust ingestion, as calculated from our samples in this study, were compared with estimated daily intake of PFCs reported from the concentrations in drinking water, fish and seafood from China. Our calculations indicate that dietary sources (EDI(dietary)) account for the overwhelming proportion of (>99% for PFOS and 98% for PFOA) total daily intake (TDI) in adults. The analyzed foodstuffs (meat, meat products, and eggs) were not the major contributors to dietary exposure to PFOS, whereas, meat was the primary contributor to dietary exposure to PFOA.

[Comparative study on water desorption and thermal desorption of aromatic hydrocarbons in soils].

In order to develop a new method to study the mobility and bioavailability of organic contaminants in soils, a set of thermal desorption device was established. Water desorption and thermal desorption of toluene and pyrene in three types of soils were investigated. The two desorption occurred as bi-phase, which indicates that the combination states of the aromatic hydrocarbons in soils are different. The desorption was described by the first-order two compartment model and an exponential decay equation. Parameters, such as fast desorption fraction F(rap), water and thermal desorption rate constants, b(w) and b(t) were derived. For toluene, values of F(rap) in three soils were 27.9%, 12.5%, 16.0%, respectively, and 2.4%, 22.0%, and 19.1% for pyrene. Values of b(w) were 0.241, 0.018, 0.038 for toluene and 0.008, 0.013, 0.012 for pyrene. There is a significantly positive correlation relationship between F (rap) and b(w) (toluene: R2 = 0.982; pyrene: R2 = 0.991). At 250 degrees C, values of b(t) in three soils were 0.167, 0.064, 0.141 for toluene, and 0.036, 0.062, 0.047 for pyrene. At 400 degrees C, the corresponding values were 0.429, 0.084, 0.398 for toluene and 0.066, 0.162, 0.153 for pyrene. Meanwhile, the water b(w) shows a good correlation with b(t) at selected temperatures (250 degrees C: R2 = 0.985; 400 degrees C: R2 = 0.848). Moreover, F(rap) is positively correlated with b(t). As F(rap) has been used to predict bioavailability, thermal desorption can therefore be used to predict bioavailability.

[Sorption and desorption of phenanthrene on sediments].

Batch experiments were employed to investigate the influences of salinity on the sorption of phenanthrene. Influences of initial phenanthrene concentration, sediment properties and salinity on desorption of phenanthrene were also studied and the mechanism for desorption hysteresis was deeply discussed. Salinity enhanced the sorption of phenanthrene on sediments, and the enhancement extent was related to sediment organic matter (SOM). A salting constant of 0.125 L x mol(-1) was derived from the PHE solubility in fresh water and salt water, and in the presence of sediment, salting constant was enhanced to 0.299 L x mol(-1). Desorption of phenanthrene all exhibited hysteresis to some extents and desorption hysteresis were described by a thermodynamic index TII. With the initial phenanthrene concentration increasing from 0.5 mg x L(-1) to 2.5 mg x L(-1), the value of TII first decreased from 0.80 to 0.38 and then increased to 0.55, suggesting the desorption hysteresis of phenanthrene first decreased and then increased. Sediment treated by NaOH showed a reduced sequestration ability on phenanthrene than the original sediment did, with the value of TII decreased from 0.55 to 0.33. Desorption of phenanthrene in fresh water was found for the first time to have a greater hysteresis than in salt water, indicated by the greater TII value of 0.55 in fresh water than that of 0.42 in salt water. Desorption hysteresis could be explained by the sorption of phenanthrene to sorption sites of different energies and sequestration inside the micropores of the sediments.

Influence of pyrene combination state in soils on its treatment efficiency by Fenton oxidation.

Interactions of hydrophobic organic compounds (HOCs) with soil organic matter (SOM) determine their combination state in soils, and therefore strongly influence their mobility, bioavailability, and chemical reactivity. Contact time (aging) of an HOC in soil also strongly influences its combination state and environmental fate. We studied Fenton oxidation of pyrene in three different soils to reveal the influences of SOM, contact time, and combination state on the efficiency of vigorous chemical reactions. Pyrene degradation efficiency depended strongly on the dose of oxidant (H(2)O(2)) and catalyst (Fe(2+)); the greatest degradation was achieved at an oxidant to catalyst molar ratio of 10:1. Pyrene degradation differed among the three soils, ranging from 65.4% to 88.9%. Pyrene degradation efficiency decreased with increasing SOM content, and the aromatic carbon content in SOM was the key parameter. We hypothesize that pyrene molecules that combine with the compact net structure of aromatic SOM are less accessible to Fenton oxidation. Furthermore, pyrene degradation efficiency decreased considerably after aged for 30 days, but further aging to 60 and 180 days did not significantly change degradation efficiency. The Fenton oxidation efficiency of pyrene in both unaged and aged soils was greater than the corresponding desorption rate during the same period, perhaps because Fenton reaction can make pyrene more accessible to the oxidant through the enhancement of HOCs' desorption by generating reductant species or by destroying SOM through oxidation.

[Desorption of polycyclic aromatic hydrocarbons in soils assisted by SPMD].

In order to develop a new method to study the desorption and bioavailability of hydrophobic organic chemicals (HOCs) in soils, a method using semi-permeable membrane device (SPMD) to study desorption of HOCs in soils has been set up, and assisted desorption of polycyclic aromatic hydrocarbons (PAHs), phenanthrene(PHE), pyrene(PYE), and benzo[a] pyrene (B[a]PYE) in three different kinds of soils was studied using SPMD. The results show that SPMD is a good measurement to study the desorption and bioavailability of HOCs in soils. SPMD assisted desorption of PAHs is highly dependent on the properties of the soils and the chemicals. PHE and PYE desorption percentages increase with the reduction of the content of soil organic matter (SOM), so that the desorption of the two chemicals increases from 56.45% and 48.28% to almost 100% when SOM content was reduced from 18.68% to 0.3%. However, clay has a significant holding effect on B[a]PYE, and PYE desorption is only 66.97% in Soil 3 with SOM of 0.3% and clay content of 39.05%. There is a great variety in the desorption among the different PAHs. With the reduction of SOM content and the elevation of contamination concentration, the difference between PHE and PYE decreases gradually, while B[a]PYE exhibits a significant difference from them. This could be attributed to the high lipophilicity and large molecular size of B[a]PYE, which make the molecule of B[a]PYE to be more easier to be held in the nanopores of clay and the dense region of SOM.