防渗膜集成永久性渗漏监控系统的定位

介绍了由导电HDPE防渗膜和预埋渗漏监控模块共同构成的集成永久性防渗膜渗漏监控系统及其基本工作原理,阐述了第3代导电防渗膜以及渗漏监控模块的特点,重点介绍了在贵州省环境保护厅监督下进行的我国第1次防渗膜永久监控系统现场验证实验,就实验场地规划、导电防渗膜的安装与检测、渗漏监控模块的安装、系统调试和实验过程分别做了说明。实验结果表明,监控系统可以对直径1 cm的小孔渗漏发出实时报警信号,定位的漏点与实际漏点间的差距仅为0.68 m,相对于1 405 m2的实验区域,定位精度达到了1/1 000,显示了极高的敏感度和良好的渗漏定位能力。该现场验证实验的成功,对于建立有效的填埋场环境监控系统有着积极的影响。     

Resistant sorption of in situ chlorobenzenes and a polychlorinated biphenyl in river Rhine suspended matter

The desorption kinetics of in situ chlorobenzenes (dichlorobenzenes, pentachlorobenzene and hexachlorobenzene) and 2,4,4^′-trichlorobiphenyl (PCB-28) were measured with a gas-purge technique for river Rhine suspended matter sampled in Lobith, The Netherlands. This suspended matter is the main source of sediment accumulation in lake Ketelmeer. In lake Ketelmeer sediment earlier observations showed that slow and very slow fractions dominate the desorption profile.

For the river Rhine suspended matter, only for PCB-28 a fast desorbing fraction of around 1.6% could be detected. The observed rate constants were on the average 0.2 h⁻¹ for fast desorption, 0.004 h⁻¹ for slow desorption, and 0.00022 h⁻¹ for very slow desorption. These values are in agreement with previous findings for the sediment from lake Ketelmeer and with available literature data on fast, slow, and very slow desorption kinetics.

The results from this study show the similarity of desorption profiles between river Rhine suspended matter, and the top layer sediment from lake Ketelmeer. This indicates that slow and very slow fractions are already present in material forming the top layer of lake Ketelmeer, and were not formed after deposition of this material in the lake. The absence of detectable fast fractions for most compounds could be caused by the absence of recent pollution of the suspended matter. But, the observations may also be explained by a rapid disappearance of compounds from the fast fraction due to a combination of a high affinity of very slow sites for these compounds, and their relatively high volatility.     

Monitoring, modelling and environmental exposure assessment of industrial chemicals in the aquatic environment

Monitoring and laboratory data play integral roles alongside fate and exposure models in comprehensive risk assessments. The principle in the European Union Technical Guidance Documents for risk assessment is that measured data may take precedence over model results but only after they are judged to be of adequate reliability and to be representative of the particular environmental compartments to which they are applied. In practice, laboratory and field data are used to provide parameters for the models, while monitoring data are used to validate the models' predictions. Thus, comprehensive risk assessments require the integration of laboratory and monitoring data with the model predictions. However, this interplay is often overlooked. Discrepancies between the results of models and monitoring should be investigated in terms of the representativeness of both. Certainly, in the context of the EU risk assessment of existing chemicals, the specific requirements for monitoring data have not been adequately addressed. The resources required for environmental monitoring, both in terms of manpower and equipment, can be very significant. The design of monitoring programmes to optimise the use of resources and the use of models as a cost-effective alternative are increasing in importance. Generic considerations and criteria for the design of new monitoring programmes to generate representative quality data for the aquatic compartment are outlined and the criteria for the use of existing data are discussed. In particular, there is a need to improve the accessibility to data sets, to standardise the data sets, to promote communication and harmonisation of programmes and to incorporate the flexibility to change monitoring protocols to amend the chemicals under investigation in line with changing needs and priorities.