Measurement Of Freely Dissolved PAHs In Natural Water And Sediment With Low Density Polyethylene Devices

The freely dissolved concentrations of hydrophobic organic compounds (HOCs) arecommon and widespread. Most of HOCs have carcinogenic, teratogenic andmutagenic. HOCs concentrations and their source apportionment studies in water areimportant issues of environmental pollution analysis. Yet ecological risk and effectsassessment of HOCs are difficult tasks. HOCs could interact with solid and dissolvedsubstances in water system. The interaction may cause their different forms, so theirbioavailability is different. Obviously HOCs that were not adsorbed distributed orconnected with other compositions (solid oxide, black carbon, composition of mineral,colloidal and dissolved natural organic matter et al) are freely dissolved contaminants.The freely dissolved HOCs have most mobility and bioavailability so their ecologicalrisk and toxicity are serious. It is a hard task to test the freely dissolved concentrationsof HOCs in water and sediment. Low density polyethylene (LDPE) is a commonsampler present.Based on the principle of LDPE, the LDPE devices were improved. PAHs wereselected as target contaminants. Equilibration Time of LDPE in performance referencecompounds (PRCs) solution, sampling time and other parameters were determined byseries of experiments in the laboratory. Based on laboratory research, LDPE wasmade in PRC to measure freely dissolved HOCs in water and sediment in naturalwater system. LDPE devices were placed into rivers and lakes in Changchun. Fivekinds of PAHs: Naphthalene, Acenaphthene, Phenanthrene, Anthracene, Pyrene inwater and sediments were sampled and PAHs concentrations were obtained by bothLDPE method and liquid-liquid/ultrasonic extraction. The concentrations from twomethods were made a comparison. Different time of the natural water was sampled.The results indicated that the concentrations of PRC stabilized after64hours; LDPEsampling time was appropriate after12days. The places we surveyed werecontaminated with PAHs. LDPE-obtained water and pore water concentrations werelower than the total concentrations from water, pore water and condiments. Thecorrelativity between the results from LDPE and liquid-liquid extraction was well. Comparison with present literature freely dissolved PAH concentrations in naturalwater system in Changchun were low. PAHs concentrations at different time from plotA showed different results. The concentrations LDPE sampled in summer were higherthan in autumn. The freely dissolved PAHs concentrations in water were20%-70%ofthe total PAHs concentrations in water. Freely dissolved PAHs in pore water were20%-80%of total PAHs sin pore water. Concentrations of phenanthrene, anthracene,pyrene were only3%-6%of the total PAHs in sediments, well Naphthalene,Acenaphthene were60%-70%. The results proved that freely dissolved PAHs couldbe sample and calculate by LDPE devices. Distribution characteristics andbioavailability of PAHs could be assessed by LDPE-obtained concentrations. Watersystem in Changchun was contaminated lightly and the ecosystem was at risk. PAHspollution should be noticed.