Investigations on the sorption of a toxaphene model congener, the B7-1450, on marine sediments

Sorption is a natural process that takes place in sediments or soils and changes the mobility and availability of hydrophobic organic compounds, such as toxaphene pesticide in the environment. The sorption of the 2-exo,3-endo,5-exo,8,9,10,10-heptachlorobornane (B7-1450), used as a model compound of the toxaphene heptachlorobornane congeners found in sediments, was investigated for the first time through a series of batch sorption experiments. The losses of B7-1450 due to adsorption onto glass walls and to evaporation occurring during analytical treatment steps were corrected. The study showed that these specific losses ranged from 2% to 3.5% for the glass walls adsorption and can be as high as 15% for the evaporation treatment. The sorption coefficients, K(d) and K(oc), of B7-1450 could be overestimated by >30%, particularly for low-concentration samples, if the losses were not corrected. Loss correction equations were established, validated and applied to determine sorption coefficients for the B7-1450 congener. The K(oc) values for B7-1450 determined over a gradient of concentrations ranged from 3.5x10(4) to 6.5x10(4)mlg(-1), revealing a strong affinity of B7-1450 for marine sediments.     

Toxicity profile of labile preservative bronopol in water: the role of more persistent and toxic transformation products

Transformation products usually differ in environmental behaviors and toxicological properties from the parent contaminants, and probably cause potential risks to the environment. Toxicity evolution of a labile preservative, bronopol, upon primary aquatic degradation processes was investigated. Bronopol rapidly hydrolyzed in natural waters, and primarily produced more stable 2-bromo-2-nitroethanol (BNE) and bromonitromethane (BNM). Light enhanced degradation of the targeted compounds with water site specific photoactivity. The bond order analysis theoretically revealed that the reversible retroaldol reactions were primary degradation routes for bronopol and BNE. Judging from toxicity assays and the relative pesticide toxicity index, these degradation products (i.e., BNE and BNM), more persistent and higher toxic than the parent, probably accumulated in natural waters and resulted in higher or prolonging adverse impacts. Therefore, these transformation products should be included into the assessment of ecological risks of non-persistent and low toxic chemicals such as the preservative bronopol.     

Polybrominated diphenyl ethers (PBDEs) and alternative brominated flame retardants in air and seawater of the European Arctic

The spatial distribution of polybrominated diphenyl ethers (PBDEs) and several alternative non-PBDE, non-regulated brominated flame retardants (BFRs) in air and seawater and the air-seawater exchange was investigated in East Greenland Sea using high-volume air and water samples. Total PBDE concentrations (Ó₁₀PBDEs) ranged from 0.09 to 1.8 pg m⁻³ in the atmosphere and from 0.03 to 0.64 pg L⁻¹ in seawater. Two alternative BFRs, Hexabromobenzene (HBB) and 2,3-dibromopropyl-2,4,6-tribromophenyl ether (DPTE), showed similar concentrations and spatial trends as PBDEs. The air-seawater gas exchange was dominated by deposition with fluxes up to −492 and −1044 pg m⁻² day⁻¹ for BDE-47 and DPTE, respectively. This study shows the first occurrence of HBB, DPTE and other alternative flame retardants (e.g., pentabromotoluene (PBT)) in the Arctic atmosphere and seawater indicating that they have a similar long-range atmospheric transport potential (LRAT) as the banned PBDEs.     

不同预处理对电镀污泥电动过程的影响

以风干电镀污泥为电动处理试验材料，水为阳极电解液，柠檬酸柠檬酸铵缓冲液为阴极电解液，施加25 V直流电压条件下电动运行5 d，研究了水、低浓度木钙和硝酸等预处理对电镀污泥电动过程的影响。结果表明，各处理的阴极电解液pH值变化平稳，都维持在3～3.5较理想的范围。而1％木钙、1％硝酸饱和预处理电镀污泥，明显改变了电动过程中电渗流和电流密度的大小，对电镀污泥Cu、Ni的去除率也有明显增加。其中，木钙、硝酸预处理后对Cu的去除率由对照的13.24％分别提高到19.05％和25.55％，即去除量分别增大3 516.35 mg/kg和7 457.62 mg/kg；木钙、硝酸预处理后对Ni的去除率由对照的14.68％分别提高到16.47％和28.85％，即去除量分别增大800.91 mg/kg和6 359.92 mg/kg。     

天津冬季PM2.5与PM10中有机碳、元素碳的污染特征

研究了天津冬季PM2.5和PM10中碳成分的污染特征.结果表明,天津冬季PM2.5和PM10的平均质量浓度分别为(124.4±60.9)、(224.6±131.2)μg/m3;总碳(TC)、有机碳(OC)与元素碳(EC)在PM2.5中的平均质量分数比在PM10中分别高出5.0%、3.6%、1.2%;PM2.5中OC、EC的相关系数较高,为0.95,表明OC、EC的来源相对简单,可能主要反应了燃煤和机动车尾气的贡献.OC/EC的平均值在PM2.5和PM10中分别为3.9、4.9.次生有机碳(SOC)在PM2.55和PM10中的平均质量浓度分别为14.9、23.4/μg/m3,分别占OC的48.5%(质量分数,下同)、49.8%,OC/EC较高可能主要与直接排放源有关;PM2.5中的OC1与OC2的比例明显高于PM10,而聚合碳(OPC)的比例又低于PM10,同时PM2.5与PM10中的EC1含量均较高,表明天津冬季燃煤取暖和机动车尾气是重要的污染源.     

Comparison of manual and automated chambers for field measurements of N2O,CH4, CO2 fluxes from cultivated land

Chamber techniques can easily be applied to field trials with multiple small plots measuring carbon- and nitrogen-trace gas fluxes. Nevertheless, such chamber measurements are usually made weekly and rarely more frequently than once daily. However, automatic chambers do allow flux measurements on sub-daily time scales. It has been hypothesized that sub-daily measurements provide more reliable results, as diurnal variations are captured better compared to manual measurements. To test this hypothesis we compared automatic and manual measurements of N₂O, CO₂ and CH₄ fluxes from tilled and non-tilled plots of a rice–wheat rotation ecosystem over a non-waterlogged period. Our results suggest that both techniques, i.e., either manual or automatic chambers of N₂O and CO₂ emissions resulted in biased fluxes. The manual measurements were adequate to capture either day-to-day or seasonal dynamics of N₂O, CO₂ and CH₄ exchanges, but overestimated the cumulative N₂O and CO₂ emissions by 18% and 31%, respectively. This was due to neglecting temperature-dependent diurnal variations of C and N trace gas fluxes. However, the automatic measurements underestimated the cumulative emissions of N₂O and CO₂ by 22% and 17%, respectively. This underestimation resulted from chamber effects upon soil moisture during rainfall processes. No significant difference was detected between the two methods in CH₄ exchanges over the non-waterlogged soils. The bias of manual chambers may be significant when pronounced diurnal variations occur. The bias of automatic measurements can only be avoided/minimized if chamber positions are frequently changed and/or if chambers are automatically opened during rainfall events. We therefore recommend using automatic chambers together with continuous measurements of soil chamber moisture to allow for soil moisture correction of fluxes or to correct flux estimates as derived by manual chambers for possible diurnal variations.     

Isolation and characterization of an Alcaligenes sp. strain DG-5 capable of degrading DDTs under aerobic conditions

In this study, an Alcaligenes sp. strain DG-5 that can effectively degrade dichlorodiphenyltrichloro-ethanes (DDTs) under aerobic conditions was isolated from DDTs-contaminated sediment. Various factors that affect the biodegradation of DDTs by DG-5 were investigated. About 88 %, 65 % and 45 % of the total DDTs were consumed within 120 h when their initial concentrations were 0.5, 5 and 15 mg L^?1, respectively. However, almost no degradation was observed when their concentration was increased to 30 mg L^?1, but the addition of nutrients significantly improved the degradation, and 66 % and 90 % of the total DDTs were degraded at 336 h in the presence of 5 g L^?1 peptone and yeast extract, respectively. Moreover, the addition of 20 mM formate also enhanced the ability of DG-5 to transform DDTs, and its DDT transformation capacity (T_c) value was increased by 1.8 - 2.7 fold for the pure (p,p’-DDT or o,p’-DDT only) and mixed systems (p,p’-DDT, o,p’-DDT, p,p’-DDD and p,p’-DDE). Furthermore, it was found that competitive inhibition in the biodegradation by DDT compounds occurred in the mixed system.     

改性二次锶渣吸附去除废水中的磷

以改性二次锶渣为吸附剂，研究了吸附时间、吸附剂投加量、磷初始浓度和pH值对废水中磷去除效果的影响。结果表明，当总磷浓度为10mg／L，pH为7、二次锶渣投加量为15g／L时，90min内就可使废水中磷的去除率达到95％以上，总磷浓度低于污水综合排放标准的一级标准；改性二次锶渣对磷的吸附符合Langmuir等温吸附模型及准二级动力学模型。     

剩余污泥超声预处理后水解酸化特性

为探讨剩余污泥超声预处理后的水解酸化特性,考察了0.6 W/mL、5 min和1 W/mL、5 min 2种超声预处理条件下污泥水解酸化过程有机质、氮、磷的释放情况。实验结果表明,2种超声预处理均可促进污泥水解酸化,并且0.6 W/mL比1 W/mL的超声预处理更有利于SCOD的释放、VFAs的产生以及氮和磷的释放;水解酸化初期,超声预处理比未经超声预处理的污泥在有机质、氮、磷释放率上差异非常明显,随着水解酸化的进行,有机质和氮释放率差异仍很明显,而磷释放程度逐渐接近;经0.6 W/mL超声预处理,污泥水解酸化3 d后,SCOD释放率、VFAs浓度、TN释放率和NH4+-N释放率分别是未经处理污泥的1.85、2.63、1.85和1.41倍,而TP和PO43--P释放率较未经处理污泥仅分别多2.44和1.23个百分点。研究表明,控制适宜的声能密度、超声时间和水解酸化进程是超声预处理强化剩余污泥水解酸化效果的关键。