Environ. Sci. Technol. 2003, 37, 5636-5644
Behavior of the Polycyclic Musks HHCB and AHTN in Lakes, Two Potential Anthropogenic Markers for Domestic Wastewater in Surface Waters IGNAZ J. BUERGE,* HANS-RUDOLF BUSER, MARKUS D. MU ¨ LLER, AND THOMAS POIGER Plant Protection Chemistry, Swiss Federal Research Station, CH-8820 Wa¨denswil, Switzerland
The synthetic polycyclic musks HHCB and AHTN are potential chemical markers for domestic wastewater contamination of surface waters. Understanding their environmental behavior is important to evaluate their suitability as markers. This study focuses on the quantification of the processes that lead to an elimination in lakes. Rate constants for all relevant processes were estimated based on laboratory studies and models previously described. In lake Zurich, during winter time, both compounds are eliminated primarily by outflowing water and due to losses to the atmosphere. In summer, direct photolysis represents the predominant elimination process for AHTN in the epilimnion of lake Zurich (quantum yield, 0.12), whereas for HHCB, photochemical degradation is still negligible. HHCB and AHTN were then measured in effluents of Swiss wastewater treatment plants (WWTPs), in remote and anthropogenically influenced Swiss surface waters, and in Mediterranean seawater using an analytical procedure based on SPE and GC-MS-SIM with D6-HHCB as internal standard (LODs for natural waters, 2 and 1 ng/L, respectively). In winter, concentrations of HHCB and AHTN in lakes (99%, respectively), and D6-HHCB, used as internal standard, was synthesized and kindly provided by P. Schmid, Swiss Federal Laboratories for Materials Testing and Research, EMPA, Du ¨ bendorf, Switzerland (structures, Figure 1). D3-AHTN was synthesized by H-D exchange from AHTN in alkaline D2O solution but was not further used due to partial D-H exchange during analysis (see later). R-Hexachlorocyclohexane (R-HCH, > 99%), used as internal standard in photolysis experiments, was from Riedel-de Hae¨n, Seelze, Germany, and 4-nitroacetophenone (g97%) and pyridine (g99.9%), used for actinometry, were from Fluka, Buchs, Switzerland. Water Samples. Wastewater samples were obtained from five municipal wastewater treatment plants (WWTPs), located in the region of Zu ¨ rich, Switzerland (Table 1). These 10.1021/es0300721 CCC: $25.00
2003 American Chemical Society Published on Web 11/11/2003
TABLE 1. Concentrations and Loads of HHCB and AHTN in Effluents of WWTPs, Canton of Zu1 rich, Switzerland WWTP Gossau Uster Pfa¨ ffikon Bubikon-Du¨ rnten Knonau mean ( SD median
population serviced
sampling date
throughput HHCB concn load per capita AHTN concn load per capita ratio [m3 d-1] [µg/L] [mg person-1 d-1] [µg/L] [mg person-1 d-1] HHCB/AHTN
11000 36000 9200 5650 5000
Jan 25, 2001 Feb 14, 2001 Feb 14, 2001 Jul 17, 2001 Jul 17, 2001
3456 14250 3177 5322 6028
1.95 1.93 1.72 1.21 0.72
0.61 0.76 0.59 1.14 0.87 0.80 ( 0.22 0.76
0.76 0.71 0.63 0.51 0.31
0.24 0.28 0.22 0.48 0.37 0.32 ( 0.11 0.28
2.58 2.73 2.71 2.39 2.37 2.56 ( 0.17
TABLE 2. Volume, Water Residence Time, Water Throughflow, and Population in the Catchment Area of the Lakes Studieda
lake
volume, V [km3]
mean water residence time, τ [d]
mean water throughflow, Q [m3/s]
rate constant for flushing, kw [d-1]c
population in catchment area, P
population per water throughflow, P/Q [persons m-3 d] f
Walensee Vierwaldsta¨ ttersee Zu¨ richsee, upper basin Zu¨ richsee, lower basin Murtensee Sempachersee Hallwilersee Baldeggersee Pfa¨ ffikersee Greifensee
2.52 11.8 0.47 3.36b 0.55 0.64 0.28 0.17 0.06b 0.15b
530 1242 69 440b 584 5479 1388 2045 770b 420b
55 110 78 89 11 1.3 2.3 1.0 0.9 4.1
0.0019 0.0008 0.0145 0.0023 0.0017 0.0002 0.0007 0.0005 0.0013 0.0024
44200 168000 120000d 330000 75798 11900 24300 11500 12900e 107000e
0.009 0.018 0.018 0.043 0.081 0.102 0.120 0.136 0.174 0.303
a Reference 15. b Reference 13. c Inverse of residence time. d Reference 16. e Office for Waste, Water, Energy, and Air of the Canton of Zurich, Switzerland (AWEL), year 2000. f Measure for the anthropogenic burden to a lake by domestic wastewater.
FIGURE 1. Structures of HHCB and AHTN. (Dx) indicates the position of deuterium in D6-HHCB and D3-AHTN. installations operate with four stages, a mechanical, biological (activated sludge, with nitrification and mostly with denitrification), and chemical treatment (phosphate precipitation with iron salts, without chlorination) and subsequent sand filtration (13). The WWTPs serve populations of between 5000 and 36 000. Wastewater was collected flow-proportionally after sand filtration during 24 h and was stored at ≈4 °C. Samples were transferred to glass bottles and kept on ice until extracted within a few hours. Surface water was sampled at several lakes and rivers in the Swiss midland region (Figure 1a in ref 14). In addition, water from a small mountain lake (Murgsee, altitude 1820 m) with inputs mainly from snow, rain, and dry deposition and water from the Mediterranean Sea (southern Spain, Figure 1b in ref 14) was analyzed. The lakes differed with respect to population in the catchment area, morphology, hydraulics, and chemical/biological characteristics (Table 2 and refs 15 and 16). Typically, the midland lakes are stratified during the warmer season (April-November) with development of an epilimnion, a thermocline at 1-15 m depth, and a hypolimnion (17). In late fall and winter, the lakes are usually mixed down to the bottom. Most lakes were sampled at their outflow at 0-1 m depths. Water samples for vertical concentration profiles from Zu ¨richsee (depths, 1-130 m) were taken at the location above the deepest point of the lake with a 10-L Niskin bottle. Grab samples of river water were taken at 0-1 m depths. All water samples were filled on-site into glass bottles, protected from light, and refrigerated (4 °C) on arrival at the lab. Extraction
was usually performed within a few days. Seawater was collected using a CTD (conductivity-temperature-depth) rosette equipped with 10-L Go-Flo bottles, transferred to glass bottles, and refrigerated until extracted. “Fossil” groundwater was analyzed periodically for quality control purposes. This groundwater, with an age of several thousand years, is not expected to be contaminated with anthropogenic compounds (18) and was thus analyzed as a blank sample and, with fortification, as a recovery sample. Solid-Phase Extraction (SPE) and Cleanup. Extraction was done with reusable columns containing ≈10 mL of a macroporous polystyrene-divinylbenzene adsorbent (BioBeads SM-2, 20-50 mesh, Bio-Rad Laboratories, Hercules, CA). Separate adsorbent columns were used for WWTP samples and surface water samples in order to prevent crosscontamination. The water samples were fortified with D6HHCB (1 ng/µL in toluene) to spike levels of 10 (natural waters) and 100-250 ng/L (WWTP effluents). Unfiltered aliquots of 200 mL (WWTP effluents) or 1 L (natural waters) were then passed through the SPE column, and the analytes were recovered with methanol and three aliquots of dichloromethane. The extracts were cleaned up on a silica column with ethyl acetate/methanol 95:5 and concentrated to a final volume of about 0.2 mL (more details on sample treatment (14)). GC-MS-SIM. Aliquots of 1 µL of the final extracts were analyzed by gas chromatography-mass spectrometry (GCMS), using a Finnigan Voyager quadrupole MS under electron impact ionization (EI, 70 eV, 200 °C) and full-scan (m/z 45300, 0.4 s/scan, nominal mass resolution) or selected-ion monitoring (SIM) conditions. The analytes were quantified in the SIM mode using the ions m/z 243.2 (M‚+ - 15) (and 258.2, M‚+, for confirmatory purposes) for HHCB/AHTN, 264.2 (M‚+) for D6-HHCB, and 218.9 (216.9) for R-HCH. The GC conditions were as follows: split/splitless injection (250 °C, 48 s splitless), DB-1 fused silica column (25 m, 0.32 mm i.d., 0.25 µm film), temperature program: 70 °C, 1 min isothermal, 25 °C/min to 180 °C, 5 °C/min to 240 °C, 3 min isothermal hold at this temperature. No interference (
