| Compared with other traditional sediment remediation technologies, in-situcarbonaceous adsorbent covering technology has the advantages of low cost, simpleconstruction, no post-processing,the smaller original ecological environment impact andso on; In this paper, we used granular activated carbon, powdered activated carbon andhumic acid as the repair adsorbent, first we measured their surface characteristics, andthese three adsorbents was applied to amend sediment which polluted by POPs in thelaboratory quiescent simulation experiments. Then granular activated carbon andpowdered activated carbon were selected for the repair agent to amend toxic andhazardous pollutants polluted sediments in the field experiment. Total analysis, fullwavelength scan, three-dimensional fluorescence spectroscopy, SPMDs, LDPEs passivesampling and bioaccumulation were used to evaluate the effectiveness of the amendmentin the laboratory experiments. And then total analysis and LDPEs passive sampling wereselected for the field experiment to accessing the effect of the amendment. The mainconclusions of this research were as follows:(1) The specific surface area, pore volume and pore size distribution of these carbonadsorbents were differences. Granular activated carbon which mainly consisted withmicropores has a huge surface area (880m2/g) and cylindrical and "V"-type compositedpore structure. Powdered activated carbon which mainly consisted with mesopore andmacroporous has a relatively high surface area (150m2/g) and conical tubular andplate-like composited pore structure. Humic acid which mainly consisted with mesoporehas a relatively small specific surface area (17m2/g) and bottle-shaped, narrow mouth width hindquarters and biconical tube-type composited pore structure.(2) Laboratory static simulation results shows that, after sediment repaired bycapping carbonaceous adsorbents, the target pollutants PCB128, PCB40and pyrene havea migration migrated to the adsorbent layer, and granular activated carbon repairment themigration phenomenon is the most obvious, the total amount of pollutants in the uppersediment respectively increased by22.63μg/kg,33.2μg/kg and0.23mg/kg after fivemonth repairment, and also after those amendment the total amount of the pollutantswere reduced. Granular activated carbon fixed condition rapidly reduced theconcentration of the overlying water soluble organic matter and made the overlying waterquality good. Powder activated carbon repair condition which the DOM content inoverlying water also significantly decreased after three month amendment, humic acidinvolved repair condition increased the repair "footprint" by introducing new solubleorganic matter to the water environment. Bionic passive sampling test results show thatgranular activated carbon got faster effectiveness for PCBs management, the averagereduced intake rates of PCBs intake by membrane were57%, powder activated carbonand humic acid got faster effectiveness for pyrene governance, but overall granularactivated carbon amendment show better results, corresponding average decrement oftarget contaminants respectively reached90%(PCBs) and88%(pyrene), almost tenpercent higher than other repair conditions. Humic acid condition fixed more PCBs sinceit introduced a number of soluble organic matter to the water environment, caused to thefilm did not detect PCBs in the enrichment process after5months repairment. By thechanged Pollutants pore water concentration which calculated from LDPEs membranecan be seen, total amount of sediment pore water pollutants treated by granular activatedcarbon dropped to0.01ng/l (PCBs) and0.48ng/l (pyrene) which lower than other repairoperating mode of the pore water concentration. Results also indicated that the morehydrophobicity of the contaminants, the smaller concentration of the contaminants in thepore water, and the more concentration of the contaminants accumulated to themembrane. Bioaccumulation test results showed that organisms still could uptake POPswhich bound by dissolving organic matter, minimum bioaccumulation quantity wereobtained at the condition of granular activated carbon amendment, respectively resultswere0.006μg/g(PCBs) and0.029μg/g(pyrene)，two kinds of these target pollutants corresponding biological enrichment factor were0.0093and0.046respectively,whichsuggests that carbonaceous repairment play a key role to the bioaccumulation. Combinedwith biological uptake and membrane passive sampling results to evaluate theeffectiveness of the repair methods will be more comprehensive.(3) In-situ amendment test result shows that, the concentration distribution of targetpollutants in different areas were uneven which lead to relatively larger measurementerror, and the amount of pollutants was reduced after five month amendment. Dimethylphthalate presented a maximum ground concentration which higher than other pollutantsto2~3orders of magnitude. Total amount analysis results revealed that, all pollutants hadthe tendency of migrating to the adsorbent layer, migration phenomenon was moreobvious in the granular activated carbon fixed condition, pollutants total amount in theadsorbent layer average increase rate reached86%, about twice than the powder carbonrepair condition. The membrane accumulation experiment results showed that twocarbonaceous adsorbent amendment were all significantly reduced aim pollutantsconcentrations, granular activated carbon repair effect was better, the average reducedintake rates intake by membrane were43.6%, about13%higher than the powder carbonrepair condition. At the same time, the results also show that the reduced intake rates ofthe target pollutants after amendment was lower than laboratory static simulation results.(4) Compared with SPMDs and LDPEs bionic test results showed that SPMDsmembrane results were more stable and persuasive, LDPEs results had little fluctuate, butalso could get similar conclusions. Simultaneous contrast the imports LDPEs and thedomestic LDPEs membranes results we can seen that the performance of two membraneswere analogous, and domestic LDPEs seems to be better, so select domestic productedmembranes for the project evaluation will be a more appropriate choice. |
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