| The studies of the spatial and temporal distribution,flux,transport,transformation,and environmental risk assessment of pollutants in aquatic environment depend mainly on the time-series monitoring data of the pollutants.Sample collection is the key step for environmental monitoring.However,it is difficult to obtained time-series data when the traditional sampling technique is applied.In this study,a new type of passive sampler based on osmotic pump(OP)and liquid phase microextraction(LPME)was developed for the first time and used to obtained time-series concentrations of pollutants in water.The main contents and results of this study are summarized as the follows:(1)A new passive sampler(OP-LPME sampler)based on OP and LPME was build,which is composed of 6 parts,namely,one OP,one extraction solvent coil,one information recorder,one porous extraction tube(Teflon AF 2400),one receiving coil and one housing.When the sampler was in operation,delivered by the OP,the extraction solvent(immiscible organic solvent)segments,which were stored in the extraction solvent coil and separated by aqueous solution in advance,would flow slowly through the porous extraction tube,which was immersed in water sample,and extract the target pollutants in the sample,and finally enter into the receiving coil for storage.During the sampling period,a number of extraction solvent segments flew through the porous extraction tube one by one,the target pollutants in water could be collected continuously.After retrieval,the target pollutants in each extraction solvent segment were determined and used to calculate the pollutant concentrations in water by calibration method.The information recorded and stored in the information recorder could be used to determine the extraction time for each solvent segment.When the pollutant concentrations in water and the extraction time were known,the time-series monitoring data were obtained.The OP-LPME sampler is power-free,small in size and weight,and can be used for long-term monitoring in field.(2)The developed OP-LPME sampler was tested in lab to extract polycyclic aromatic hydrocarbons(PAHs)in spiked water sample.The results showed that the concentrations of bicyclic,tricyclic,and tetracyclic PAHs in the extraction solvent(toluene)of the sampler varied with the concentrations of PAHs in the water sample.This indicated that the obtained results of the sampler could reflect the variation of the pollutants in water with time.However,a response delay for tetracyclic PAHs was found due to the small size of the pores in Teflon AF 2400 tube wall,and pentacyclic,hexacyclic PAHs could not be collected by the sampler.The feasibilities of two calibration methods were investigated.Semi-quantitative analysis of Acy,Flu,and Phe could be achieved when laboratory calibration was applied,and big errors were found for other PAHs.Due to the significant loss of extraction solvent,the PCRs calibration method with deuterated PAHs was proved to be ineffective for the sampler.As a result,the calibration method for OP-LPME sampler needs further studies(3)The OP-LPME sampler was deployed in Beixi and Xixi at Jiulong River for one week to monitor PAHs.The results show that the sampler ran very well in field.At Xixi station,naphthalene and phenanthrene were found in grab samples and the extraction solvent segments of the sampler.The time-series concentrations of phenanthrene obtained by analyzing the grab samples and calibrating the results of the sampler were almost in the same level.However,fluoranthene was detected in the grab samples but not in the extraction solvent segments of the sampler,it might be caused by the small pore size of Teflon AF 2400.These results shows that the result of the sampler can reflect the water pollution situation to some extent. |
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