珠江口水、沉积物及生物体As含量分布特征及生态风险评价

于2008年2、5、8及11月对珠江口进行了水、沉积物和生物体As含量的调查,分析其分布特征以及进行生态评价。结果表明：珠江口水体中As含量平均值为2.88μg·L-1,符合一类海水水质标准;其中,11月份显著高于其它3个月份(P <0.05)。全年珠江口水体八个河口在地域分布上As平均含量由高到低依次为：虎门、鸡啼门、磨刀门、崖门、洪沥门、蕉门、横门、虎跳门。表层沉积物As含量平均值为38.73 mg·kg-1,沉积物中As含量均超过海洋沉积物质量一类标准,但均未超三类标准。结果显示,表层沉积物横门含量最高,为(70.5±2.0) mg·kg-1,显著高于其它7个口门(P <0.05),而其它7个口门差异不显著。各口门含量从大到小依次为横门、洪沥门、鸡啼门、虎门、崖门、磨刀门、虎跳门、蕉门。表层沉积物地质累积指数评价结果与潜在生态风险系数评价结果一致,横门为中等污染水平,其余站点均为低污染水平。采集代表性生物样品,其中11种鱼类As平均含量为0.587 mg·kg-1,部分受检鱼类超出水产品中有毒有害物质限量要求,超标率为37.8%,肉食性鱼类平均含量要略低于杂食性鱼类,但不同食性和不同生活水层的鱼类As含量差异不显著(P >0.05)。受检生物样品虾的含量为0.314 mg·kg-1,符合水产品中有毒有害物质限量要求。与历年比较发现珠江口水、沉积物和生物体中As含量有上升的趋势,与其它河口相比较发现珠江口As污染在对比的河口和海湾中受污染程度较高。     

Removal of sulfadiazine from aqueous solution on kaolinite

The adsorption of sulfadiazine onto kaolinite clay as an alternative adsorbent was examined in aqueous solution, hnpacts of the contact time, pH, temperature, ionic strength and coexistent surfactants on the adsorption process were evaluated. The pH significantly influenced the adsorption process, with adsorption being promoted at lower pH due to the cation exchange mechanism. Decreasing ionic strength in the solution was favorable for adsorption, and the addition of cationic and anionic surfactants had negative effects on the adsorption capacity of sulfadiazine on kaolinite. Kinetic experiments showed that the adsorption followed the pseudo-second-order model. The equilibrium adsorption was well described by both Freundlich and Dubinin-Radushkevich （DR） models. According to the DR model, the adsorption mechanism was determined by cationic exchange and weak physical forces. The thermodynamic study showed that sulfadiazine adsorption onto kaolinite was a sponta- neous and endothermic reaction.     

Genotype variations in accumulation of cadmium and lead in celery (Apium graveolens L.) and screening for low Cd and Pb accumulative cultivars

To help reduce risks of heavy metal pollution, two pot experiments were conducted to investigate the variations, transfer potential, and stability of Cadmium (Cd) and Lead (Pb) accumulations in celery (Apium graveolens L.) and to screen for low Cd and Pb accumulative cultivars. The maximum differences in shoot Cd concentration were 4.7-fold under low-Cd exposure and 3.3-fold under high-Cd exposure. These genotype variations in Cd accumulation are sufficiently large to help reduce Cd contamination risk in soil by using the Low-Cd-Accumulative genotypes. Cd accumulation of the Low-Cd-Accumulative genotypes is significantly positive correlated with Pb accumulation. Evidence obtained proves that Cd and Pb accumulations in celery are stable and genotype-dependent at the cultivar level. The presence of high-Pb contamination in soil promoted Cd accumulation in shoots of celery. Celery is considered a species with high risks in Cd pollution and low risks in Pb pollution. Among the tested cultivars, cv. Shuanggangkangbing (SGKB) had the lowest shoot Cd and Pb accumulating abilities, and thus is the most important material for breeding of pollution-safe cultivars (PSCs) to minimize Cd and Pb accumulations in celery.     

Relationship between physicochemical properties and dewaterability of hydrothermal sludge derived from different source

Sewage sludge (SS) and deinking sludge (DS) were used to comparatively study the hydrothermal dewatering of sludge with different components. For a better overview, an insight into the relationship between physicochemical properties and dewaterability of hydrothermal sludge was provided. Results found that not all kinds of sludge were suitably conditioned by hydrothermal treatment (HT) in term of the elevation of dewaterability. Higher hydrothermal temperature tended to enhance the dewaterability of SS rather than DS, which was supported by the variation of their physicochemical properties (including water distribution, bonding energy, extracellular polymeric substance (EPS), particles size, acid functional groups and zeta potential in this study). In addition, the changes in surface morphology suggested that the reverse effect of HT on sludge dewaterability was mainly due to their dewatering behavior. For SS, the destruction of EPS structure leaded to the release of bound water, thereby strengthening sludge dewatering. Conversely, “Bridging effect” generated by lignocellulose in DS was beneficial for sludge dewatering; however, the increasing hydrothermal temperature degraded part of lignocellulose and weakened “bridging effect”, finally resulting in worse dewaterability of DS.     

硫氰酸根及其复杂体系的辐照降解研究

研究了硫氰酸根及其复杂体系⁶⁰Ｃo源γ射线辐照降解的情况,分别探讨了在自由基清除剂存在下硫氰酸根的降解,硫氰酸根辐照后氰的浓度,氰、硫氰复杂体系和氰、铜氰及硫氰酸根的复杂体系的辐照降解情况.结果表明,在自由基清除剂NaHCO₃和正丁醇存在的情况下硫氰酸根的降解受到影响,发现硫氰酸根在辐照的过程中有氰根的产生,可能的辐解方程为：SCN^-＋8·OH→SO^2-₄＋CN^-＋4H₂Ｏ,在氰、硫氰酸根复杂体系中硫氰的降解率只有30％左右,而游离氰的降解受硫氰影响较小,在氰、铜氰和硫氰酸根复杂体系中,由于竞争反应,硫氰酸根难以完全降解,氰能较快被降解,而铜氰则由于其强络合能力而在溶液中主要组成是Cu(CN)^2-₃,使得总氰的降解只能达80％左右,不能较完全降解.     

Epigenetic effect of long-term bisphenol A exposure on human breast adenocarcinoma cells

In this research, epigenetic effects of bisphenol A (BPA) on human breast cancer MCF-7 cells were analyzed. Genome-wide DNA methylation and gene expression were analyzed in MCF-7 cells exposed to BPA (10^?5 and 10^?6 mol/L for 5 weeks). No significant changes in the global level of 5-methyl-2′-deoxycytidine and 5-hydroxymethyl-2′-deoxycytidine were observed. DNA methylation profiling analysis indicated that BPA exposure resulted in the hypermethylation of FOXK2, LKB1, LMX1A and CUGBP2 and the hypomethylation of PTPRN2, TRIM27, BCAS3 and ZNF423. Decreased expression of apoptosis genes (P38 and BCL2L1) and increased expression of chemokine (Cxcl2 and ccl20) were detected. Changes of these genes were speculated to affect the ERα-related cell growth as well as cell apoptosis.     

Inverse uncertainty characteristics of pollution source identification for river chemical spill incidents by stochastic analysis

Identifying source information after river chemical spill occurrences is critical for emergency responses. However, the inverse uncertainty characteristics of this kind of pollution source inversion problem have not yet been clearly elucidated. To fill this gap, stochastic analysis approaches, including a regional sensitivity analysis method, identifiability plot and perturbation methods, were employed to conduct an empirical investigation on generic inverse uncertainty characteristics under a well-accepted uncertainty analysis framework. Case studies based on field tracer experiments and synthetic numerical tracer experiments revealed several new rules. For example, the release load can be most easily inverted, and the source location is responsible for the largest uncertainty among the source parameters. The diffusion and convection processes are more sensitive than the dilution and pollutant attenuation processes to the optimization of objective functions in terms of structural uncertainty. The differences among the different objective functions are smaller for instantaneous release than for continuous release cases. Small monitoring errors affect the inversion results only slightly, which can be ignored in practice. Interestingly, the estimated values of the release location and time negatively deviate from the real values, and the extent is positively correlated with the relative size of the mixing zone to the objective river reach. These new findings improve decision making in emergency responses to sudden water pollution and guide the monitoring network design.

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High zinc removal from water and soil using struvite-supported diatomite obtained by nitrogen and phosphate recovery from wastewater

Zinc is known as an essential element of human life. However, excessive zinc discharge into water and soil causes water pollution, leading to serious health issues such as septicemia, meningitis and iron-deficiency anemia. Here, a novel material made of struvite-supported diatomite was obtained from eutrophic water treated by mesoporous MgO-modified diatomite. This material was applied for zinc remediation in aqueous solutions and contaminated soils to test the reuse of P-containing products. Struvite-supported diatomite was characterized by field emission scanning electron microscopy and X-ray diffraction. Results show that the maximum removal efficiency of Zn(II) from wastewater streams reached 90.54% at an initial pH of 5 and struvite-supported diatomite dosage of 0.3 g/L. Moreover, the X-ray diffraction patterns of precipitates after Zn(II) sorption show that the combination between zinc and the phosphate group played a key role for zinc removal in solution. For Zn-contaminated soils amended with 10% struvite-supported diatomite, available Zn decreased by 65.38% and acid soluble Zn decreased by 56.9% after 56 days.     

High CO<Subscript>2</Subscript> adsorption by amino-modified bio-spherical cellulose nanofibres aerogels

Climate change has become increasingly serious due to the greenhouse effect. It is therefore necessary to control the content of greenhouse gases such as carbon dioxide in the atmosphere, using, for instance, CO₂-adsorbing materials. Here, we synthesized ultra-lightweight and spherical cellulose nanofibres aerogels by a suspension titration method using an efficient amination process. These functional materials with high porosity, higher than 96.54%, and three-dimensional network structure, were prepared by freeze-drying spherical cellulose nanofibres hydrogel. Their maximum CO₂ adsorption capacity reaches 1.78 mmol/g, and they show excellent regeneration, of more than 10 cycles. This synthesis of bioaerogels represents a new method for the preparation of bio-CO₂ adsorbents.     

Reaction pathways of dimethyl phthalate degradation in TiO2-UV-O2 and TiO2-UV-Fe(VI) systems

The photocatalytic degradation of dimethyl phthalate (DMP) in aqueous TiO₂ suspension under UV illumination has been investigated using oxygen (O₂) and ferrate (Fe(VI)) as electron acceptors. The experiments demonstrated that Fe(VI) was a more effective electron acceptor than O₂ for scavenging the conduction band electrons from the surface of the catalyst. Some major intermediate products from DMP degradation were identified by HPLC and GC/MS analyses. The analytical results identified dimethyl 3-hydroxyphthalate and dimethyl 2-hydroxyphthalate as the two main intermediate products from the DMP degradation in the TiO₂–UV–O₂ system, while in contrast phthalic acid was found to be the main intermediate product in the TiO₂–UV–Fe(VI) system. These findings indicate that DMP degradation in the TiO₂–UV–O₂ and TiO₂–UV–Fe(VI) systems followed different reaction pathways. An electron spin resonance analysis confirmed that hydroxyl radicals existed in the TiO₂–UV–O₂ reaction system and an unknown radical species (most likely an iron–oxo species) is suspected to exist in the TiO₂–UV–Fe(VI) reaction system. Two pathway schemes of DMP degradation in the TiO₂–UV–O₂ and TiO₂–UV–Fe(VI) reaction systems are proposed. It is believed that the radicals formed in the TiO₂–UV–O₂ reaction system preferably attack the aromatic ring of the DMP, while in contrast the radicals formed in the TiO₂–UV–Fe(VI) reaction systems attack the alkyl chain of DMP.