Pharmaceuticals in Groundwater - American Chemical Society

Chapter 5

Pharmaceuticals in Groundwater: Clofibric Acid beneath Sewage Farms South of Berlin, Germany 1

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Traugott Scheytt , Susanne Grams , Elzbieta Rejman-Rasinski , Thomas Heberer , and Hans-Jürgen Stan Downloaded by PENNSYLVANIA STATE UNIV on July 28, 2012 | http://pubs.acs.org Publication Date: July 30, 2001 | doi: 10.1021/bk-2001-0791.ch005

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Institute of Applied Geosciences II, Technical University of Berlin, Berlin, Germany Institute of Food Chemistry, Technical University of Berlin, Berlin, Germany 2

One of the first findings of pharmaceuticals in groundwater was reported from the sewage irrigation farms south of Berlin. Clofibric acid, the active metabolite of blood lipid regulators, was measured in concentrations up to 4.2 μg/L in groundwater. The fate of clofibric acid was investigated within the project "Sewage Farms South of Berlin" and with laboratory experiments. The distribution of clofibric acid in the unsaturated and saturated zone of the sewage irrigation farms reflects the high mobility and persistence of this substance. Results from laboratory batch experiments with sediments from the vicinity of the sewage irrigation farms show generally low sorption of clofibric acid. There is clear indication for the input of clofibric acid via sewage irrigation although no uniform spatial distribution pattern was found. Concentrations of clofibric acid in groundwater decrease due to the cessation of sewage farming operations.

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© 2001 American Chemical Society

In Pharmaceuticals and Care Products in the Environment; Daughton, C., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2001.

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Downloaded by PENNSYLVANIA STATE UNIV on July 28, 2012 | http://pubs.acs.org Publication Date: July 30, 2001 | doi: 10.1021/bk-2001-0791.ch005

Occurrences of pharmaceuticals in surface water and sewage water have been widely reported (1-3). Pharmaceuticals have been analyzed in German Rivers (e.g., Rhine, Danube), in the Italian river Po, in Swiss lakes, and even in the North Sea (4). Compared with those occurrences, the reported incidence of drugs in groundwater samples is much rarer. The processes leading to the input of pharmaceuticals into aquifers need further investigation, and the behavior of these substances, once within an aquifer, is almost unknown.

Groundwater input paths In the 1980s, the environmental behavior and the risks from pharmaceutical chemicals in the aquatic environment were assessed by Richardson and Bowron (5). The first analysis of a human medical compound, clofibric acid, in groundwater samples of Berlin area was reported in 1991 (6). Meanwhile, occurrences of pharmaceuticals in groundwater have not only been reported from the Berlin area, but also from several other places worldwide. Investigations from the state of Nevada (U.S.) show the presence of human pharmaceuticals (i.e., chlorpropamide, phensuximide, and carbamazepine) in groundwater (7). These investigators made use of these drugs, together with caffeine and elevated nitrate levels in groundwater, as indicators of recharge from domestic wastewater. The authors pointed out, however, that the usefulness of human pharmaceuticals as indicators of groundwater contamination by domestic wastewater is limited due to the unpredictable presence of drugs. Organic compounds originating from pharmaceutical manufacturing waste were identified in the groundwater down gradient of a landfill in Grindsted (Denmark). Among others, sulfonamides, barbiturates, and propyphenazone were the primary constituents detected in groundwater (8). Many of the identified organic compounds appeared at high concentrations in the sampling points (wells) close to the landfill. Sulfanilic acid (up to 6.5 mg/L) and propyphenazone (up to 4.0 mg/L) for example, were present in high concentrations. Almost all pharmaceuticals were no longer measurable within a distance of 115 m downstream of the landfill. The authors (8) argued that this could not be explained by dilution alone, when taking into consideration the chloride ion, which acts as a conservative tracer in this part of the aquifer. Most of the compounds were attenuated in the anaerobic zone characterized as methanogenic/sulfate-reducing, and generally the largest reduction seemed to take place under more reducing redox conditions.



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In the 1970s Garrison et al (9) and Hignite and Azarnoff (10) detected clofibric acid in sewage effluent. Clofibric acid is the active metabolite of the blood lipid regulators like clofibrate, etofibrate, and etofyllin clofibrate. Their investigations showed that only a small percentage of clofibric acid was eliminated by sewage water treatment. If surface water is contaminated by pharmaceuticals, these substances can reach groundwater in case of influent conditions (losing stream) and bank infiltration. Furthermore, groundwater contamination through sewage water is likely to be due to leaky sewage and septic systems. Irrigation with effluent water is another path by which drugs can be input into groundwater, as shown by Heberer and Stan (11). In Germany, the use of blood lipid regulators increased in the early 1960s. The daily doses of, e.g., clofibrate amounts to 1.5 g with about 29 million daydoses prescribed annually in 1993 in Germany. On the total, 198 million daydoses of clofibric acid derivatives and analogs were prescribed in 1993 with an estimated amount of about 15-21 t of clofibric acid released in 1993 with the sewage in Germany (Figure 1).

Figure 1. Prescriptions of clofibric acid derivatives and analogs in Million "Defined Day Doses " (DDD)from1984 to 1993 in Germany; source: (1 Recent investigations revealed that not only clofibric acid but a whole series of drags and drug metabolites were found at concentrations up to the μg/L-level in groundwater samples of Berlin waterworks. Among these pharmaceuticals detected in groundwater are phenazone, propyphenazone, diclofenac, ibuprofen, fenofibrate, and several other compounds (13). Clofibric acid was detected in groundwater and drinking water with maximum concentrations of up to 7,300 ng/L (14). The effect of sewage farm irrigation with the target of optimizing the reuse of sewage water is investigated at the sewage irrigation farms in Cairo, Egypt.



87 Sewage farms are designed to irrigate sewage effluent with the aim of improving the fertility of the soil. Even in the groundwater beneath these wellengineered sewage irrigation farms, a pharmaceutical was detected. Clofibric acid was found in concentrations of 40 ng/L to 75 ng/L in groundwater samples from sewage irrigation farms Gabal Al-Asfar (north of Cairo) in Egypt (15). These findings indicate that the occurrence of drugs in groundwater is not a local phenomenon. The fate of clofibric acid was investigated within the project "Sewage Farms South of Berlin" and with laboratory experiments. The objectives of these studies were to determine the environmental and transport behavior of clofibric acid, especially in the unsaturated and saturated zone.

Sample Preparation and Analysis of Clofibric Acid The water samples collected at the sewage irrigation farms south of Berlin had a volume of at least 1 liter. Samples were collected from sewage effluent, from surface water, from the unsaturated zone, and from the saturated zone in different depths. After collecting, the samples were transported directly to the laboratory. The sample extracts prepared by solid-phase extraction (SPE) were derivatized with different reagents such as pentafluorobenzyl bromide to enable gas chromatographic detection of the acidic analytes. A l l sample extracts were analyzed applying capillary gas chromatography-mass spectrometry (GC-MS) with selected ion monitoring (SIM). The detection limit was about 1 ng/L, and the limit of determination was 10-25 ng/L. More detailed information on analysis of clofibric acid is provided elsewhere (11, 14).

Sewage Irrigation Farms South of Berlin The sewage irrigation farms in the south of Berlin have been investigated within a research project that started in 1992. These farms are located about 10 km south of Berlin city limits. Sewage farming took place on an area of about 16 k m and started in 1894. About 80 years later, the area that was irrigated by sewage effluent decreased gradually until 1994, when irrigation with sewage effluent stopped completely. During the period of operation, the sewage irrigation farms were flooded with sewage effluent at an average of 1,400 mm to 3,000 mm per year (16). Within these farms, there are interconnected drainage channels. After irrigating with sewage water, only a part of the water infiltrated so deep as to recharge groundwater. A large amount of sewage water infiltrated into the unsaturated zone and was drained by the drainage channels after passing 2


88 via a short soil path (ca. 2 m). The run-off from the sewage irrigation farms, as well as drainage water, flowed to the rivers, an unquantified portion of which reached the river Spree upstream of Berlin.


Geology and Hydrogeology Geology beneath the sewage irrigation farms consists of quaternary sediments. These sediments belong to three major glaciations: the Elsterian, the Saalian, and Weichselian Glaciation. Tertiary Sediments are buried under these younger Pleistocene series. The quaternary sediments have a total thickness of 50 m in morphological highs, and up to 300 m in subsurface channels. These sediments consist of mostly glaciofluviatile fine-to-coarse grained sands with tills of differing thicknesses in between. Furthermore, the glacial sequence is often glaciotectonically disturbed and exhibits erosional patterns. From a hydrogeological point of view, these quaternary sediments can be subdivided into four aquifers (1: uppermost aquifer, 4: deepest quaternary aquifer) and 3 aquitards in between. The deepest, fifth aquifer belongs to the Tertiary. The aquifers are composed of sands, whereas the aquitards are composed of the tills. Hydraulic conductivities range from 1 χ 10" m/s to 4 χ 10" m/s for the aquifers, and the aquitards are characterized by Κ values between 1 χ 10" m/s to 9 χ 10" m/s. Due to these relatively high conductivities, even of the aquitards, and due to glaciotectonics, the aquifers are not isolated by the aquitards. Furthermore, the aquifers show a high number of interconnections, especially due to geological windows within the aquitards. The deepest, fifth aquifer belongs to the Tertiary and consists of fine-grained sand. Figure 2 shows a map of the sewage irrigation farms with the location of wells. Groundwater elevation of the 1 aquifer is portrayed by isolines of piezometric levels. Due to sewage irrigation, piezometric levels are high in the part of the sewage irrigation farms where sewage effluent was irrigated until the end of the operation. Piezometric levels decrease towards the edges of the study region. The groundwater flow direction is vertical in the 1 aquifer and radial in the 2 aquifer. 3

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Groundwater Ages Transport of groundwater constituents (including these pharmaceuticals) is mainly based on groundwater flow. Knowledge about groundwater ages can be used to infer groundwater flow paths. Groundwater ages were determined from tritium analysis of 84 groundwater samples. With these results, ages of up to 45 years can be dated.



89 Generally, groundwater in the uppermost aquifer has ages less than 10 years. Commonly, groundwater ages as young as 10 years can be found beneath the sewage irrigation farms within the 2 aquifer (Figure 3). This is due to the high recharge at the sewage irrigation farms and an almost vertical groundwater flow in the subsurface beneath the sewage irrigation farms. Vertical groundwater flow is almost completely limited to the 1 aquifer, whereas the predominant flow direction in the deeper aquifers is horizontal. Outside of the area of sewage farming operation, only the uppermost aquifer (1 aquifer) has groundwater with ages less than 10 years. Ages of groundwater increase (up to 40 years) in deeper aquifers. The deepest, tertiary aquifer generally has ages of more than 45 years (18).

Groundwater Chemistry The state of soil and groundwater contamination was analyzed, including heavy metals and organic contaminants, with a total of up to 845 groundwater samples for most of the constituents. Inorganic constituents analyzed were the main cations (Na , K , C a , M g , F e , M n , N H ) and anions ( H C 0 \ N 0 , N 0 , P0 ", CI", S0 "). The physico-chemical parameters (temperature, specific conductance, p H , redox potential, 0 ) were measured in the field. The organic compounds that were analyzed include pesticides, herbicides, PCBs, halogenated aliphatics, and halogenated aromatics. To discriminate groundwater that is influenced by sewage farming from naturally recharged groundwater, the relationship between sodium and calcium was found to be valuable. Ratios of concentrations (mg/L) of sodium to calcium higher than 0.4 proved to be the best indicators of groundwater influenced by sewage farming. Ratios of Na/Ca in groundwater without the influence of sewage fanning vary between 0.1 and 0.2. Groundwater from the upper two aquifers beneath the sewage irrigation farms have typically Na/Ca ratios between 0.6 and 0.9. This classification coincides well with groundwater ages of this region as the groundwater in the two uppermost aquifer has generally ages less than 10 years due the high recharge through sewage irrigation. Because of the above-mentioned vertical groundwater flow in the upper aquifer, the variations of groundwater constituents exhibit a remarkable spatial variation in the 1 aquifer. In the deeper aquifers, concentration variations decrease due to hydrodynamic dispersion and diffusion. +

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Figure 2. Map of equipotentials ofpiezometric levels of the 1 Aquifer in the area of the sewage farms south of Berlin; also location of cross section. (Reproduced from reference 17. Copyright 1998 Springer Verlag.)



Figure 3. Groundwater ages beneath the sewage farms (18)


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Distribution of Clofibric Acid Clofibric acid was measured in sewage effluent (10 samples), surface water, and in water from drainage channels (82 samples). Clofibric acid concentrations in these samples varied between values below the detection limit (1 ng/L) to 4,550 ng/L. The mean value for water from drainage channels was 1,100 ng/L. This average was even higher in places with effluent groundwater conditions. This suggests that after irrigation with sewage water, which subsequently infiltrated into the subsurface, a certain amount flows into the drainage channels, leading to these high concentrations. Surface water from the same area that is not directly influenced by sewage farm operation exhibits mean values ranging from 125 ng/L to 310 ng/L. Water samples from different depths within the unsaturated zone were collected, and the content of clofibric acid was measured. The average concentrations in pore water from the unsaturated zone declined from higher values near ground surface (1,430 ng/L) to lower values near the groundwater table (65 ng/L). The distribution of clofibric acid in groundwater was based on the analysis of 597 samples. Generally higher amounts of clofibric acid were measured in the upper aquifers and lower concentrations were detected in the deeper aquifers. However, the concentrations in most of the groundwater samples were below the detection limit. The maximum concentration in groundwater was found to be 4,175 ng/L below the sewage irrigation farms. Box plots are used to show the distribution of clofibric acid in sewage water, surface water, and the five aquifers (Figure 4). Upper and lower quartiles define the top and bottom of the box, and the median is marked by a horizontal line inside the box. The horizontal lines ("whiskers") connected to the upper and lower box sides are "adjacent values", i.e., the most extreme values that are not outliers. The observations that exceed the adjacent values are "outside values" or "outliers" and are marked as dots. This statistical analysis was done according to standard statistical procedures with the software package SPSS. About 80% of 690 samples had clofibric acid concentrations that were below the detection limit. Decreasing concentrations from sewage effluent to surface water, and in the subsurface with increasing depth, can be seen clearly in Figure 4. There are, however, a high number of outside values. Statistical analysis revealed that there was no clear correlation between clofibric acid concentration and most of the groundwater constituents or with different redox or p H environments. There was only a slight correlation between the concentration of clofibric acid and P 0 , D O C , and C O D as well as Na/Ca ratio; these parameters and ratios were found to be indictors of sewage recharge. A typical spatial distribution pattern for a conservative tracer could be found in the aquifers of the sewage irrigation farms for chloride and was expected for clofibric acid. However, no such "conservative" distribution was observed for clofibric acid: there were samples from wells of the same aquifer that contained high amounts adjacent to wells with no clofibric acid at all. 3

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Figure 4. Boxplots of clofibric acid concentrations [ng/L] in sewage effluent, surface water, and in thefiveaquifers; number of samples: Sewage water: 10; Surface water: 82; 1 Aquifer: 325; 2 Aquifer: 169; 3-5 Aquifer: 103. (Reproducedfrom reference 17. Copyright 1998 Springer Verlag.)



95 The wells were sampled several times since 1993, during which time a decrease of clofibric acid concentrations was observed in almost all wells, due to the cessation of sewage farming. Table I shows an almost continuous decrease of concentrations in well Rbl/78 over time. Although no homogeneous distribution was found in groundwater, the relative concentrations of clofibric acid remained about the same over time. High concentrations in groundwater from certain wells were found to also yield high concentrations during the next sampling campaign. In well Rbl/78 (Table I), level M P 2 at a depth of 12.9 m below ground surface exhibited the highest concentrations compared with the other levels for all sampling campaigns, although the values decreased markedly from the sampling campaign in fall 1993 to sampling campaign in summer 1999.

Table I. Concentration of clofibric acid in groundwater from multi-level well Rbl/78; level screenings are from top to bottom Well Name

Aquifer

Concentration of clofibric acid [ng/L] Fall 93

Fall 94

Rbl/78 OP

1

50

14

Spring 95 Summer 99 0

dry well

Rbl/78 M P I Rbl/78 M P 2 Rbl/78 M P 3 Rbl/78 U P

1 1 1 2

30 950 450 135

10 270 220 30

7 316 230 40

0 160 25 15

Laboratory Batch Experiments The decrease of clofibric acid concentration within the unsaturated zone and the lack of a uniform (i.e., "conservative") distribution in the groundwater at the sewage irrigation farms might be the effect of degradation or sorption. Therefore, batch experiments were conducted to investigate the sorption behavior of this substance. Medium-grained sand of the unsaturated zone was used as the sediment material. The samples were collected to the north of the sewage irrigation farms to (1) obtain sediment material similar to that from the sewage irrigation farms, and (2) to reduce background contamination; the location from which the sediment was obtained had never been in use as a sewage irrigation farm. To perform the experiments, a special fluid circulation device was used to better simulate natural conditions. This device operates with undisturbed soil samples and a permanent flow through the samples to enable



96 "dynamic" batch experiments. The major advantage is that soil samples remain undisturbed compared with normal batch experiments. Clofibric acid was added to deionized water to give concentrations of 300 ng/L, 1.0 μg/L, 3.0 μg/L, and 10.0 μg/L of clofibric acid in the solution. Dry weight of the samples (medium-grained sand) was about 250 g, and the amount of clofibric acid / water solution in the cycle about 175 mL. The experiment was conducted at two temperatures — 8 °C and 19°C; these temperatures were chosen because they correspond to the natural average temperature and maximum natural temperature in soils in the region of the sewage irrigation farms. The duration of each run was 24 hours. Set-up for all runs was kept the same except for temperature and clofibric acid concentration. Immediately after adding clofibric acid to the solution (about 1 hour) the actual initial concentration was measured. In general, the observed sorption was low (Table II). The concentrations after the run typically showed that sorption was low at lower concentrations (0.3 μg/L and 1.0 μg/L) and at the higher temperature (19°C). Sorption increased at higher concentrations (10 μg/L) and the lower temperature (8 °C).

Table II. Results of "dynamic" batch tests with the fluid-circulation device; concentration values are clofibric acid in the solution (water) Mixing Actual initial concentration concentration [Mg/LJ [Mg/L] 0.3 0.3 1.0 1.0 3.0 3.0 10.0 10.0

0.34 0.34 1.01 1.01 2.40 2.40 6.86 6.86

19°C 8°C Concentration after Concentration after experiment run experiment run [Mg/LJ 0.26

0.95 0.70 2.13

5.72 5.82

0.40 0.34 0.84 1.06 2.46 2.00 6.30 6.45

Interestingly, there was a difference between intended initial concentration and actually measured initial concentration. A comparison of these two concentrations reveals that although there was almost no difference at 0.3 μg/L and 1.0 μg/L, increasing differences were found at the higher concentrations (3 μg/L and 10 μg/L). Compared with the sorption results, these differences exceeded the amount of clofibric acid sorbed on the sediment material. This difference between intended initial solution at a concentration of 10 μg/L and


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the actually measured initial concentration not only occurred at these batch tests but also at a laboratory degradation experiment and column experiment (15). Results of a laboratory column experiment (15) with medium-grained sand show that clofibric acid is transported with the velocity of the conservative tracer (lithium). It was also interesting that the redox potential decreased remarkably from + 500 m V to -250 m V after adding clofibric acid and increased again after flushing the column with pure groundwater. Again, no correlation between clofibric acid and pH, oxygen content, or the concentration of groundwater constituents was found, whereas a possible dependence of the redox potential on clofibric acid was observed.

Discussion and Conclusion Data analysis from the sewage irrigation farms clearly indicates the input of clofibric acid by sewage irrigation. The input path of clofibric acid can be traced from sewage effluent and drainage water into the unsaturated zone and saturated zone. Analysis of groundwater ages shows that the older the groundwater, the lower the mean concentration of clofibric acid. Clofibric acid can consequently be used as an indicator for anthropogenic input sources. Significant amounts of clofibric acid even in the deeper aquifers demonstrate the high persistence of this contaminant. A typical spatial distribution pattern for a conservative tracer (chloride) was found in the aquifers of the sewage irrigation farms. This was also anticipated for clofibric acid because a previously conducted laboratory column experiment showed a transport behavior comparable to a conservative tracer. No such distribution, however, was observed for clofibric acid at the sewage irrigation farms. Instead, groundwater samples from wells of the same aquifer that contained high levels were adjacent to wells with no detectable clofibric acid. These variations may be due to varying input of clofibric acid as the concentrations in sewage effluent itself varied. According to Landesumweltamt Brandenburg (16), the mean annual precipitation (1951 - 1980) is 641 mm and the potential évapotranspiration is 664 mm in the study region. The climatic water balance is slightly negative. Therefore, varying évapotranspiration may, for example, lead to an increased concentration in summer when évapotranspiration is high. In conclusion, the input function is unpredictable to some extent and with this the distribution of clofibric acid in the unsaturated and saturated zone. Because there was no uniform concentration distribution of clofibric acid in groundwater, degradation and/or sorption processes were assumed. Additionally, the decrease in the clofibric acid concentrations in soil water from



98 the unsaturated zone with increasing depth also suggests possible degradation and/or sorption processes. Results of the sorption experiments with the fluid circulation device exhibited almost no sorption at lower concentrations or higher temperatures, and only slightly higher sorption tendency at higher concentrations and lower temperatures. The laboratory experiments exhibited an interesting difference between the intended initial concentration and the actually measured initial concentration. The actually measured initial concentration was much lower, and this phenomenon was also observed in several other experiments. We conclude that degradation processes, in addition to sorption, lower the concentration of clofibric acid in the study site. One of these degradation processes might be microbial metabolism. Despite the lack of a uniform distribution, clofibric acid concentrations in groundwater did exhibit certain consistent patterns. Groundwater samples with higher concentrations at certain wells in one sampling campaign showed the higher concentrations during other sampling campaigns again. Relative concentrations remain about the same over time. Concentrations showed almost no dependence on predominant physicochemical conditions or groundwater constituents. Groundwater flow paths seemed to determine the concentration of clofibric acid in groundwater. Furthermore, there has been a general decrease in concentration since 1993, coinciding with the end of sewage farm operations.

References 1. Sacher, F.; Lochow, E.; Bethmann, D.; Brauch, H.-J. Vom Wasser 1998, 90. 2. Heberer, Th.; Schmidt-Bäumler, K . ; Stan, H.-J. Acta Hydrochim. Hydrobiol. 1998, 26, 272-278. 3. Ternes, T.A. Wat. Res. 1998, 32, 3245 - 3260. 4. Buser, H.-R.; Müller, M . D . Environ. Sci. Technol. 1998, 32 (1), 188-192. 5. Richardson, M . L . ; Bowron, J.M. J. Pharm. Pharmacol. 1985, 37, 1-12. 6. Stan, H.-J.; Linkerhägner, M. Vom Wasser 1992, 79, 85-88. 7. Seiler, R.L.; Zaugg, S.D.; Thomas, J.M.; Howcroft, D . L . Ground Wat., 1999, 37 (3), 405-410. 8. Holm, J.V.; Rügge, K . ; Bjerg, P.L.; Christensen, Th.H. Environ. Sci. Technol., 1995, 29 (5), 1415-1420. 9. Garrison, A . W . ; Pope, J.D.; Allen, F.R. In: Identification & Analysis of Organic Pollutants in Water, Keith, C.H., Ed.; Ann Arbor Science Publishers Inc.: A n n Arbor, Michigan, 1976; pp 517-556. 10. Hignite, C.H.; Azarnoff, D.L. Life Sci., 1977, 20, 337-342. 11. Heberer, Th.; Stan, H.-J. Int. J. Environ. Anal. Chem. 1997, 67, 113-124.



99 12. Klose, G.; Schwabe, U . In Arzneimittel-Report 94; Schwabe, U.; Pfaffrath, D., Eds.; Gustav Fischer Verlag: Stuttgart, 1994; pp 271-277. 13. Heberer, Th.; Fuhrmann, B.; Schmidt-Bäumler, K . ; Tsipi, D.; Koutsouba, V . ; Hiskia, A . In Pharmaceuticals and Personal Care Products in the Environment: Scientific and Regulatory Issues; Daughton, C.G.; Jones-Lepp, T., Eds.; A C S book series; ACS/Oxford University Press: Washington, D C , 2000. 14. Heberer, Th.; Dünnbier, U.; Reilich, Ch.; Stan, H.-J. Fresenius Environ. Bull. 1997, 6, 438-443. 15. Scheytt, T.; Grams, S.; Fell, H . In Gambling With Groundwater - Physical, Chemical, and Biological Aspects of Aquifer-Stream Relations; Brahana, J.V., Eckstein, Y., Ongley L . K . , Schneider, R., Moore, J.E., Eds.; I A H / A I H Proceedings Volume: St. Paul, 1998; pp 13-18. 16. Landesumweltamt Brandenburg, Rieselfelder südlich Berlins - Altlast, Grundwasser, Oberflächengewässer; Studien- und Tagungsberichte B d . 13/14, Potsdam, 1997; pp 297. 17. Scheytt, T.; Grams, S.; Fell, H . Grundwasser 1998, 2, 67-79. 18. Asbrand, M. Ph.D. thesis, Technical University Berlin, Berlin, 1997.


Pharmaceuticals in Groundwater - American Chemical Society

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