Studien zum Einfluss einer chemischen Ladung auf Sorption, Schicksal und Bildung nicht-extrahierbarer Rückstände organischer Chemikalien im Boden

Autor: Claßen, Daniela
Přispěvatelé: Schäffer, Andreas, Hollert, Henner
Jazyk: němčina
Rok vydání: 2019
Předmět:
Zdroj: Aachen 1 Online-Ressource (122 Seiten) : Illustrationen, Diagramme (2019). doi:10.18154/RWTH-2019-07191 = Dissertation, RWTH Aachen University, 2019
DOI: 10.18154/RWTH-2019-07191
Popis: Dissertation, RWTH Aachen University, 2019; Dissertation, RWTH Aachen University, 2019
In the present study we investigated the influence of an ionic functional group on the sorption, fate and formation of non-extractable residues of organic compounds in soil. Using uncharged 4-n-dodecylphenol[phenyl ring-14C(U)] (14C-DP), negatively charged 4-n-dodecylbenzenesulfonic acid[phenyl ring-14C(U)] sodium salt (14C-DS-) and positively charged 4-n-dodecylbenzyltrimethylammonium chloride[phenyl ring-14C(U)] (14CDA+) with high structural similarity, we performed sorption tests according to OECD 106 (Adsorption – Desorption using a Batch-Equilibrium Method) and simulation tests in soil according to OECD 307 (Aerobic and Anaerobic Transformation in Soil) with LUFA soil 5M. In the sorption tests equilibrium for adsorption and desorption of 14C-DA+ was reached after 15 and 1680 min and for 14C-DP and 14C-DS- after 240 min, respectively. During the sorption test, DP was abiotically degraded to more polar transformation products. Partitioning coefficients were therefore determined according to the amounts of adsorbed and desorbed DP detected by TLC-Analysis. Sorption kinetic for DS- was linear and the partitioning coefficients for adsorption and desorption amounted to logK=2.68 and logK =1.78. Cooperative adsorption of DP und DA+ was obviously higher (logK>3.30) compared to 14C-DS- and is considered irreversible (logK 3.0) and deviate from calculated logKoc in case of the ionic chemicals. Considering the structural similarity it could be shown that a positive charge lead to an increased sorption of organic chemicals on soil. Aim of the simulation test was to investigate the fate of 14C-DP, 14C-DS- und 14C-DA+ in sterile and non-sterile soil. After application of the test substances with 1 mg/kg to sterilized and non-sterilized soil and incubation for 0, 1, 7, 14, 49, 84 and 124 days, samples were sequentially extracted. Distribution of the applied radioactivity (AR) among volatile, mineralized, extractable and non-extractable residues (NER) for 14C-DP, 14C-DS- und 14C-DA+ were investigated. Extractable portions of 14C were examined by means of TLC, HPLC and LC-MS/MS analyses. After 124 days of incubation highest mineralization could be observed for 14C-DS- (64.5% AR), followed by 14C-DP (44.0% AR) and 14C-DA+ (37.8% AR) whereas formation of 14CO2 in sterile soil was neglectable. In case of 14C-DP und 14C-DS- the rate of mineralization and the microbial activity (DMSO reduction rate) in non-sterilized soil simultaneous increased from day 0 until day 14. For 14C-DA+ the mineralization and DMSO reduction rate were constantly low over time. Extractable radioactivity for 4C-DA+ amounted to 18.0% AR, but only low amounts of 14C-DP und 14C-DS- were extractable form the soil (2.7-4.7% AR) at the end of the test. Besides 14C-DP, 14C-DS- and 14C-DA+ polar and nonpolar (14C-DA+) transformation products were detected in the extracts over time. Highest amounts of 14C-DP, 14C-DS- and 14C-DA+ were potentially bioavailable in soil. In the calcium chloride extracts only transformation products were detected. Half-life (DT50) decrease in the following manner: DA+(61.70 days)>DS-(18.20 days)>DP(9.96 days). The findings suggest that a negative and positive charge increases the DT50 of organic chemicals in soil. Highest amounts of NER at the end of the tests were observed for 14C-DP (45.4% AR) followed by 14C-DA+ (34.2% AR) and 14C-DS- (23.1% AR). Considerable amounts of NER of 14C-DA+ (16.0% AR) were formed under sterile soil conditions. NER at day 7 and 84 were further investigated with respect to sequestered, covalently bound and biogenic residues (NER types I, II, and III). Silylation of 14C-DP, 14C-DS- and 14C-DA+ derived NER after 7 and 84 days of incubation released 3.0-23.2% AR, indicating that these were strongly sorbed or physically entrapped (type I NER) in the soil. The reminder of the residues (12.9-33.1% AR) were covalently bound (type II NER) to the soil. Analysis of extracts derived by silylation shows that 14C-DP (2.3% AR), but neither 14C-DS- nor 14C-DA+ were released by the silylation procedure. This suggests that only in case of 14C-DP, the parent substance was part of type I NER, which is considered reversibly bound to soil. Acid hydrolysis of the 14C-DP, 14C-DS- and 14C-DA+ NER containing soil after 7 and 84 days of incubation and subsequent analysis of soil extracts regarding 14C-aminoacids (14C-AA) indicates that 2.5-23.8% AR are biogenically formed residues (type III NER) in soil. Most DP and DS- derived NER were biogenically or covalently bound, whereas DA+ predominantly forms sequestered NER in soil. After re-incubation of the NER containing soil of 14C-DP, 14C-DS- und 14C-DA+ after 7 and 84 days with nonsterilized soil for 54 days, remobilisation (sum of volatile, mineralised and extractable residues) amounted to 7.2-19.1% AR; however, the highest amounts still remained nonextractable in soil (16.4-31.2% AR). With regard to the results it is recommended to use an experimentally determined logKd instead of calculated/experimental logKoc values for the assessment of the adsorption of ionic chemicals in soil in frame of persistence assessment. Furthermore, chemicals with an obviously high NER formation should be investigated according to sequestered (type I), covalently bound (type II) and biogenic (type III) NER. The formation of type I NER should be taken into account in the persistence assessment, if the parent substance has been analytically determined in this fraction. In this case, the sequestered amount of parent molecule should be included in the calculation of the DT50. In case that analytical investigations of type I NER regarding the parent molecule were technically not feasible, the DT50 has to be calculated considering the total amount of sequestered (type I) NER in accordance with the precautionary principle.
Databáze: OpenAIRE
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