预测沉积物-水微宇宙系统中化学品浓度变化的多介质模型

沉积物-水微宇宙系统是经济合作发展组织(Organisation for Economic Co-Operation and Development,OECD)颁布的化学品测试准则中推荐的试验系统之一,可用来测试化学品对底栖生物的慢性毒性。为了在试验前对化学品的浓度变化进行预测,进而确定试验方法,以摇蚊慢性毒性试验系统为例,采用环境多介质模型的建模方法,构建了一种可通过化学品理化性质和试验系统参数,对化学品在沉积物-水试验系统中浓度变化进行预测的模型。结合试验数据和文献资料,给出了模型中试验系统参数的推荐取值,并使用Matlab软件中的Simulink工具对模型进行编程和求解。以此模型为基础,给出了模型在3个方面的应用,即预测蓄积时间、预测平衡时间以及拟合试验数据。对80种已有或假想化学品的蓄积时间和平衡时间进行了计算,得出的范围分别为1~204 d和1~73 d。此外,适当修改模型结构和模型参数,也可将其应用于其他暴露场景中。但使用模型对化学品浓度进行预测时发现,模型仅对沉积物中化学品浓度的预测结果较为准确,而对水中化学品浓度的预测结果与实测值相差1~2个数量级。模型对浓度的预测精度未来仍需进一步提高。上述研究结果完善了沉积物-水微宇宙系统试验方法。     

北京市MODIS气溶胶光学厚度与PM_(10)质量浓度的相关性分析

利用北京地区2012年1—12月NASA MODIS气溶胶光学厚度(AOD)和通过空气污染指数(API)转换得到的PM10质量浓度进行了相关性分析.结果发现,二者的直接相关程度较低,在引入季节变化的气溶胶标高且考虑了气溶胶的垂直分布后,进行标高订正,二者的相关系数有所提高;在考虑了湿度影响因子后,进行湿度订正,二者的相关系数显著提高;引入平均风速、平均气温和平均气压等气象因素,进行多元回归分析,相关系数进一步提高.证实了卫星遥感气溶胶光学厚度在经过垂直和湿度订正并考虑气象因素的情况下,可以作为监测北京地区颗粒物污染物地面分布的一个有效手段.     

Prediction of effluent concentration in a wastewater treatment plant using machine learning models

Of growing amount of food waste, the integrated food waste and waste water treatment was regarded as one of the efficient modeling method. However, the load of food waste to the conventional waste treatment process might lead to the high concentration of total nitrogen(T-N) impact on the effluent water quality. The objective of this study is to establish two machine learning models—artificial neural networks(ANNs) and support vector machines(SVMs), in order to predict 1-day interval T-N concentration of effluent from a wastewater treatment plant in Ulsan, Korea. Daily water quality data and meteorological data were used and the performance of both models was evaluated in terms of the coefficient of determination(R~2), Nash–Sutcliff efficiency(NSE), relative efficiency criteria(d rel). Additionally, Latin-Hypercube one-factor-at-a-time(LH-OAT) and a pattern search algorithm were applied to sensitivity analysis and model parameter optimization, respectively. Results showed that both models could be effectively applied to the 1-day interval prediction of T-N concentration of effluent. SVM model showed a higher prediction accuracy in the training stage and similar result in the validation stage.However, the sensitivity analysis demonstrated that the ANN model was a superior model for 1-day interval T-N concentration prediction in terms of the cause-and-effect relationship between T-N concentration and modeling input values to integrated food waste and waste water treatment. This study suggested the efficient and robust nonlinear time-series modeling method for an early prediction of the water quality of integrated food waste and waste water treatment process.     

Predicted no-effect concentrations for mercury species and ecological risk assessment for mercury pollution in aquatic environment

Mercury(Hg) exists in different chemical forms presenting varied toxic potentials. It is necessary to explore an ecological risk assessment method for different mercury species in aquatic environment. The predicted no-effect concentrations(PNECs) for Hg(Ⅱ) and methyl mercury(Me Hg) in the aqueous phase, calculated using the species sensitivity distribution method and the assessment factor method, were 0.39 and 6.5 × 10-3μg/L, respectively. The partition theory of Hg between sediment and aqueous phases was considered, along with PNECs for the aqueous phase to conduct an ecological risk assessment for Hg in the sediment phase. Two case studies, one in China and one in the Western Black Sea, were conducted using these PNECs. The toxicity of mercury is heavily dependent on their forms,and their potential ecological risk should be respectively evaluated on the basis of mercury species.     

Ozone concentrations, flux and potential effect on yield during wheat growth in the Northwest-Shandong Plain of China

Ozone (O₃) concentration and flux (F_o) were measured using the eddy covariance technique over a wheat field in the Northwest-Shandong Plain of China. The O₃-induced wheat yield loss was estimated by utilizing O₃ exposure-response models. The results showed that: (1) During the growing season (7 March to 7 June, 2012), the minimum (16.1 ppbV) and maximum (53.3 ppbV) mean O₃ concentrations occurred at approximately 6:30 and 16:00, respectively. The mean and maximum of all measured O₃ concentrations were 31.3 and 128.4 ppbV, respectively. The variation of O₃ concentration was mainly affected by solar radiation and temperature. (2) The mean diurnal variation of deposition velocity (V_d) can be divided into four phases, and the maximum occurred at noon (12:00). Averaged V_d during daytime (6:00–18:00) and nighttime (18:00–6:00) were 0.42 and 0.14 cm/sec, respectively. The maximum of measured V_d was about 1.5 cm/sec. The magnitude of V_d was influenced by the wheat growing stage, and its variation was significantly correlated with both global radiation and friction velocity. (3) The maximum mean F_o appeared at 14:00, and the maximum measured F_o was − 33.5 nmol/(m²·sec). Averaged F_o during daytime and nighttime were − 6.9 and − 1.5 nmol/(m²·sec), respectively. (4) Using O₃ exposure-response functions obtained from the USA, Europe, and China, the O₃-induced wheat yield reduction in the district was estimated as 12.9% on average (5.5%–23.3%). Large uncertainties were related to the statistical methods and environmental conditions involved in deriving the exposure-response functions.     

Effect of AlCl3 concentration on nanoparticle removal by coagulation

In recent years, engineered nanoparticles, as a new group of contaminants emerging in natural water, have been given more attention. In order to understand the behavior of nanoparticles in the conventional water treatment process, three kinds of nanoparticle suspensions, namely multi-walled carbon nanotube-humic acid (MWCNT-HA), multi-walled carbon nanotube-N,N-dimethylformamide (MWCNT-DMF) and nanoTiO₂-humic acid (TiO₂-HA) were employed to investigate their coagulation removal efficiencies with varying aluminum chloride (AlCl₃) concentrations. Results showed that nanoparticle removal rate curves had a reverse “U” shape with increasing concentration of aluminum ion (Al^3 +). More than 90% of nanoparticles could be effectively removed by an appropriate Al^3 + concentration. At higher Al^3 + concentration, nanoparticles would be restabilized. The hydrodynamic particle size of nanoparticles was found to be the crucial factor influencing the effective concentration range (ECR) of Al^3 + for nanoparticle removal. The ECR of Al^3 + followed the order MWCNT-DMF > MWCNT-HA > TiO₂-HA, which is the reverse of the nanoparticle size trend. At a given concentration, smaller nanoparticles carry more surface charges, and thus consume more coagulants for neutralization. Therefore, over-saturation occurred at relatively higher Al^3 + concentration and a wider ECR was obtained. The ECR became broader with increasing pH because of the smaller hydrodynamic particle size of nanoparticles at higher pH values. A high ionic strength of NaCl can also widen the ECR due to its strong potential to compress the electric double layer. It was concluded that it is important to adjust the dose of Al^3 + in the ECR for nanoparticle removal in water treatment.     

河流氧化亚氮产生和排放研究综述

氧化亚氮(N2O)是仅次于二氧化碳(CO2)和甲烷(CH4)的重要温室气体.由于人类活动对土地的影响导致河流系统中氮的可利用性增加,河流生态系统的N2O排放量正日益增长.本文对国内外河流水体N2O溶存浓度和饱和度、水-气界面排放通量及沉积物-水界面交换通量等数据进行了收集,并总结和分析了河流生态系统中N2O的产生机制及主要影响因子.     

上海市降水过程中汞的浓度变化研究

为了研究降水过程中汞浓度变化规律,采集了上海市区2009年7月6日一次连续降水过程中的分时段12个雨水样品,利用冷原子荧光测汞仪测定了总汞、溶解态汞和颗粒态汞浓度.分析结果显示,降水过程各时段雨水样品的总汞浓度变化范围为0.26～0.53 μg·L-1之间,其中溶解态汞占总汞的比例为67.9％～96.8％;总汞浓度和颗粒态汞浓度的总体变化规律较一致,降水事件的前30分钟内浓度较高,之后逐渐降低,最终趋于稳定;溶解态汞浓度从降水事件开始由高到低逐渐变化,最终也趋于稳定.通过清除比计算云下冲刷过程对雨水中总汞浓度的贡献,发现云下冲刷的贡献大于40.9％.     

萍乡市土壤中重金属离子含量、空间分布及其变化趋势研究

以江西省萍乡地区土壤为研究对象,分析研究了萍乡市土壤中重金属离子的含量及空间分布特征,并初步估算了重金属离子累积现速率和加速度.结果表明:萍乡市土壤整体环境质量较好,但随着社会经济的快速发展,工农业生产等人为活动对土壤的影响越来越大.从空间分布来看,在全市5个县区布置的52个采样点中,共有24个测点的重金属离子含量超标.其中上栗县有10个测点的重金属离子含量超标,明显多于其他县区,出现了与其他县区不同的污染特征.     

臭氧+曝气生物滤池深度处理工艺试验研究

针对某污水厂出水不达标的情况,本研究采用臭氧(O3)和曝气生物滤池(BAF)组合工艺对其进行深度处理.结果表明,当采用两级臭氧+曝气生物滤池工艺时,出水COD在31～46 mg/L,色度在13～29倍,均达到一级A排放标准.在最佳运行条件下,臭氧氧化使相对分子质量大于50 000的有机物含量减少10％,小于1 000的有机物含量增加14％.曝气生物滤池工艺使相对分子质量小于1 000的有机物含量降低了24％.