Environ. Sci. Technol. 2008, 42, 1898–1903
Occurrence of Organophosphorus Flame Retardant and Plasticizers in Three Volcanic Lakes of Central Italy ALESSANDRO BACALONI, FRANCESCA CUCCI, CHIARA GUARINO, MANUELA NAZZARI, ROBERTO SAMPERI, AND ALDO LAGANÀ* Department of Chemistry, “La Sapienza” University, Piazzale Aldo Moro 5, 00185 Rome, Italy
Received October 09, 2007. Revised manuscript received December 10, 2007. Accepted December 11, 2007.
The concentration levels, distribution, and seasonal fluctuations of 12 organophosphorus flame retardants and plasticizers (OPs), of which some are reported to be toxic to aquatic organisms, were investigated in lakes from June 2006 to June 2007. Three volcanic lakes located in the Lazio area (Central Italy) and characterized by a different anthropical impact were selected. Analysis of lake water samples showed that in closed ecosystems (hydrogeological systems), such as small volcanic lakes, OP contamination may occur even in the absence of industries and treated or untreated waste discharges. The selected substances were found at ng/L concentrations in all lakes. In the two more anthropized lakes tributyl phosphate and tripropyl phosphate were the most abundant OPs, with peaks of respectively 784 and 951 ng/L. Maximum pollution levels were reached in October-November, and concentrations decreased to a minimum value in March-April. Chlorinated OPs showed the same trend, but their concentrations were 1 order of magnitude lower and the level decreasing was shifted with respect to alkyl OPs. On the contrary, tris(2-butoxyethyl) phosphate concentrations were quite similar among all water samples analyzed, indicating that their sources were different in nature. One of the three lakes is an important source of drinkable water, so nine wells situated in its neighborhood were also examined. No correlation between lake water and groundwater contamination could be found.
Introduction Organophosphorus compounds, industrially produced by reacting phosphorus oxychloride with various reactants, are derivates of phosphoric acid and comprise halogenated or nonhalogenated alkyl esters of phosphoric acid as well as aromatic derivatives, such as triphenyl phosphate (TPP), tricresyl phosphate (TCP), and triphenyl phosphine oxide (TPPO). Depending on the substituent characteristics, they have different chemical and physical properties making them useful in diverse applications as pesticides (1), flame retardants, plasticizers, hydraulic fluids, antifoaming agents, lacquers, paints or glues (2). The environmental fate of organophosphorus pesticides has been extensively studied * Corresponding author phone: +39 06 49913679; fax: +39 06 490631; e-mail:
[email protected]. 1898
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(1), whereas organophosphates employed for other ends (OPs) can be considered as emerging pollutants. These compounds are large-scale chemicals, with a production volume of almost 200000 tons per year and global consumption still growing (3). Their use as additives in diverse applications constitutes a risk as they may be released by the products they are added to and spread further in the environment. Moreover, some organophosphate esters like TPP, tributyl phosphate (TBP), and triortho-cresyl phosphate (ToCP) are supposed to be neurotoxic (4–6), and carcinogenic effects on animals have been observed for other OPs like tris(1,3-dichloro-2-propyl) phosphate (TDCP), tris(2-chloroethyl) phosphate (TCEP), and probably tris(2-chloroisopropyl) phosphate (TCPP) and tris(2-butoxyethyl) phosphate (TBEP) (7, 8). These compounds occur in the environment as a result of anthropogenic activity. Several studies have been conducted on the level and distribution of OPs in sewage treatment plants (STPs) (9–15). Although data about the degradation rate during processes of wastewater treatment are in some cases in disagreement, various papers report that STPs are a point source of introduction of these compounds into surface waters (11–16), and in fact, some OPs have often been detected in river waters (11–13, 17–19). Only two works reported the occurrence of OPs in groundwater, monitoring only three compounds (TBP, TCEP, and TBEP) (11, 12), while no study has been conducted to analyze OPs in a hydrographic closed system. One example of this kind of system is volcanic lakes, lacking emissaries and tributaries and STP input. In this type of lake, contamination can occur only via local anthropogenic activities or rain and runoff processes. In fact, the occurrence of OPs in remote areas, originated from long-range air transportation, has been reported in previous papers, where some OPs have been detected in samples of rainwater (11, 12, 20), snow (20, 21), Antarctica particulate matter (22), and pine needles in the Sierra Nevada Mountains, USA (23). In this study, seasonal fluctuations of the concentrations of 12 OPs in three lakes, with different anthropical impact, located in the Lazio area (Central Italy) were investigated from June 2006 to June 2007. One of the three lakes is an important source of drinkable water, so nine wells situated in its neighborhood were also monitored. Finally, some rainwater samples were collected in Rome and analyzed in order to verify the impact of rain as a source of OPs.
Experimental Section Reagents and Chemicals. Trimethyl phosphate (TMP), triethyl phosphate (TEP), TCEP, TPPO, tripropyl phosphate (TPrP), TPP, TBP, triisobutyl phosphate (TiBP), TBEP, and TCP were purchased from Sigma-Aldrich (St. Louis, MO). TCPP and TDCP were kindly provided by Supresta Chimicafine S.r.l., (Milan, Italy). Perdeuterated triphenyl phosphate, kindly supplied by C. Crescenzi (Stockholm University), was used as an internal standard (IS). Although not commercially available, it could be easily synthesized by reaction of pentadeuterated phenol with phosphoryl chloride (24). Individual stock solutions of each compound were prepared in acetonitrile at 1 mg/mL concentration. A composite stock solution at 0.05 mg/mL level was prepared by mixing equal volumes of individual stocks and properly diluting with acetonitrile. Working standard solutions were prepared by suitable dilution of the composite stock, kept at 4 °C and renewed weekly. All organic solvents were HPLC grade from Carlo Erba (Milan, Italy) and were used as received. Formic acid was RPE grade from Carlo Erba. Ultrapure water was 10.1021/es702549g CCC: $40.75
2008 American Chemical Society
Published on Web 02/12/2008
TABLE 1. Grid Values of the Monitoring Stations north Vico Lake 1 Vico Lake 2 Vico Lake 3 Vico Lake 4 Vico Lake 5 Albano Lake 1 Albano Lake 2 Albano Lake 3 Albano Lake 4 Martignano Lake Martignano Lake Martignano Lake Martignano Lake
FIGURE 1. Schematic map of the Lazio region showing the location of the three lakes investigated. produced from distilled water by a Milli-Q system (Millipore Corporation, Billerica, MA). Description of Sites. The main criterion in selecting the lakes was the different anthropical degree. The lakes selected were Albano, Vico, and Martignano, all of them situated in the Lazio region, Italy (Figure 1). A detailed view of their geographic location can be obtained by visiting a specialized Web site (25). Albano Lake is a volcanic basin contained in an ellipsoidal crater depression. The lake has a surface area of 6 km2, and its depth reaches 175 m. The mean renewal time is more than 67 years. Lacking emissaries and tributaries, the lake is characterized by an ancient Roman channel carved in the lava rocks through the crater wall, which has the purpose of regulating the lake level. Since 1960, the water level has sunk almost 4 m below the level of the artificial emissary. This is one of the reasons for the worsening of trophic conditions, caused especially by the reckless sucking from the water layer of this area. The lake is surrounded by houses inhabited all the year round and by many bathing resorts. Vico Lake is located at the bottom of a volcanic crater. The lake is surrounded by the Cimini Mountains, including the vast Mount Venere. The lake surface is 12.1 km2, with a maximum depth of 49.5 m and a hydraulic residence time of 17 years. The lake is surrounded by dense vegetation and agricultural activities, mostly hazelnut and chestnut tree cultivations, while a tourist area has developed on the northern shore. In addition, it is an important source of water for a number of municipalities: groundwater supplies several water systems used for drinking water (serving about 130000 inhabitants) and irrigation (for a total irrigated area of some 180 km2) (26). Lake Martignano, also of volcanic origin, whose crater is part of the Sabini range of hills, is a small lake, with a surface area of only 2.4 km2, and its depth is about 60 m. Lacking emissaries, its drainage basin is completely closed, and the water supplies are limited to rainfalls, drainage from surrounding area, a small tributary that totally dried up in the past few years, and some submerged springs; thus mean renewal time is calculated at about 31 years. Its environment is unspoiled because there are no roads or houses, with the exception of two small farms. The lake is situated in an area mainly constituted of cultivated lands and a thick bush composed of wild olive trees, juniper, and arbutus. Collection of Samples. The compounds of interest were monitored in the Vico, Albano, and Martignano lakes, and samplings were carried out once a month from June 2006 to June 2007. The grid values of the monitoring stations are listed in Table 1. Lake water samples were collected at a
1 2 3 4
42 42 42 42 42 41 41 41 41 42 42 42 42
18250 19490 19310 18590 18270 44460 45050 45310 44190 06470 07110 06280 06370
east 12 12 12 12 12 12 12 12 12 12 12 12 12
09190 11410 09380 10280 11310 40150 39190 39460 40510 18550 19080 18380 19160
depth of 0.5 m, using 2.5 L Ruttner bottles, and immediately transferred in glass bottles. Groundwater samples were collected in March 2007 from nine wells located in the Vico Lake neighborhood. After at least 10 min free flowing through the pipe line, 2.5 L were collected in glass bottles. Samples of rainwater were collected using flat bottom glass vessels, 30 cm i.d.; sampling was stopped when the water level was about 2 cm (1.4 L). Rain was collected in Rome and in the Martignano Lake visitors’ parking site during two rainfalls in May and June 2007, after at least two weeks of dry weather, and during the same day at both locations. During the first sampling, the rainfall in Martignano was too short, so the sample was discarded. All samples were kept at 4 °C, and to avoid possible sample alteration, they were extracted within 48 h from sampling. Before processing lake water samples, we removed suspended particulate matter by filtration with a 125 mm diameter GF/C glass microfiber filter (Whatman, Maidstone, U.K.) to avoid SPE cartridge plugging. Selected OPs were analyzed in duplicate in all water samples. Briefly, 0.5 L of water was extracted by a polymeric SPE cartridge and analyzed by (RP)LC/ESI+-MS/MS in MRM mode. For a detailed description of the analytical method, see ref 19. The relative standard deviations for all analytes were between 4 and 14% (n ) 5). Statistical evaluations were performed by ANOVA and correlation analysis. (p ) 0.05). Precautions and Quality Control. Due to the widespread use of OP compounds, they could be found in new vials probably owing to the plastic packing procedure, so all glassware used in this study was extensively cleaned with a 5% (w/v) nonionic surfactant solution and then rinsed with deionized water followed by acetone and finally ethanol. Moreover, all solvents and SPE cartridges utilized were carefully checked to be OP-free, performing blank procedure analysis when a new batch of solvents or laboratory equipment was purchased. For each set of real sample analysis a blank procedure and two tap water samples spiked at 30 ng/L and 100 ng/L, respectively, were also analyzed.
Results and Discussion Concentration levels, averaged on various sampling sites, of each OP found in the lakes Albano, Vico, and Martignano are reported respectively in Tables 2-4. Due to the low recovery (ca. 20%) (19), for TMP the method is not suitable for quantification and can be used only for screening; therefore, for this analyte the tables only report “detected” or “not detected”. As a general rule, there was no correlation between the sampling site inside a lake and analyte concentration, thus mean concentrations and standard deviation are reported. All the selected analytes were detected in all three lakes investigated. In all three lakes pollution is essentially VOL. 42, NO. 6, 2008 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
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TABLE 2. Concentrations of Selected Organophosphorus Compounds in Albano Lake Water Samples meana (SDb), ng/L Jun 2006 Jul 2006 Aug 2006 Sep 2006 Oct 2006 Nov 2006 Dec 2006 Jan 2007 Feb 2007 Mar 2007 Apr 2007 May 2007 Jun 2007 c
TMP TEP TCEP TPPO TPrP TCPP TDCP TPP TiBP TnBP TBEP TCP
d 26 (4) 5 (2) nd 13 (7) 6 (3) 5 (2) 7 (5) 81 (12) 42 (11) 10 (6) 2 (2)
d 42 (6) 8 (5) nq 13 (4) 9 (4) 5 (3) 15 (5) 150 (18) 36 (9) 21 (4) 6 (2)
d 23 (13) 17 (8) 2 (1) 109 (17) 15 (4) 19 (12) 16 (7) 380 (31) 70 (13) 47 (12) 8 (5)
d 17 (8) 14 (5) 1 (0) 429 (27) 21 (11) 17 (9) 8 (4) 346 (28) 419 (59) 82 (22) 11 (6)
d 18 (5) 14 (3) 1 (0) 486 (32) 19 (11) 15 (11) 4 (1) 209 (43) 242 (32) 32 (17) 8 (7)
d 13 (4) 27 (6) 4 (1) 115 (15) 62 (24) 41 (20) 14 (7) 327 (23) 784 (45) 127 (33) 12 (4)
nd 8 (3) 22 (11) 2 (2) 73 (21) 54 (26) 56 (28) 5 (3) 167 (16) 215 (17) 85 (19) 10 (4)
nd 5 (4) 9 (4) nd 16 (10) 34 (19) 60 (36) 3 (2) 96 (21) 45 (26) 53 (18) 5 (5)
nd 2 (1) nq nd 4 (2) 26 (20) 45 (26) nq 15 (8) 8 (5) 23 (20) 1 (2)
nd 1 (0) nq nd nq 29 (33) 20–1335e nq 2 (1) nq 16 (15) 2 (3)
nd nqd nq nq 2 (1) 19 (5) 20 (11) nq 1 (1) 3 (3) 9 (6) 1 (0)
nd 4 (2) 6 (2) nq 4 (1) 11 (8) 23 (9) 2 (2) 16 (6) 22 (9) 10 (5) 3 (2)
d 13 (6) 15 (9) 1 (1) 10 (4) 7 (6) 13 (7) 4 (3) 37 (20) 12 (7) 19 (8) 2 (3)
a Mean values from five sampling points. b Standard deviation. c d is detected; nd is not detected. Due to the low recovery (ca. 20%), for TMP the method is suitable for the detection but not for the quantification. d Detected, but not quantified. e Range of concentrations. Values detected did not follow a Gaussian distribution.
TABLE 3. Concentrations of Selected Organophosphorus Compounds in Vico Lake Water Samples meana (SDb), ng/L Jun 2006 Jul 2006 Aug 2006 Sep 2006 Oct 2006 Nov 2006 Dec 2006 Jan 2007 Feb 2007 Mar 2007 Apr 2007 May 2007 Jun 2007 c
TMP TEP TCEP TPPO TPrP TCPP TDCP TPP TiBP TnBP TBEP TCP
d 2 (1) nqd 1 (0) 13 (8) 12 (11) 7 (3) 6 (3) 31 (9) 17 (8) 75 (18) 3 (1)
d 2 (0) 4 (3) 1 (1) 114 (21) 10 (9) 12 (8) 21 (2) 164 (22) 353 (44) 61 (20) 1 (1)
d 8 (3) 15 (9) 2 (1) 183 (45) 17 (13) 35 (17) 15 (7) 81 (22) 211 (35) 99 (27) 7 (3)
d 12 (2) 31 (13) 3 (2) 229 (32) 15 (10) 29 (9) 15 (12) 163 (43) 165 (91) 115 (61) 17 (3)
d 27 (1) 12 (2) 1 (0) 951 (42) 27 (13) 29 (4) 11 (2) 351 (18) 636 (77) 50 (14) 14 (1)
d 10 (3) 33 (13) 2 (2) 33 (12) 25 (5) 24 (8) 8 (4) 34 (20) 14 (18) 12 (4) 9 (1)
d 4 (2) 64 (17) 3 (4) 6 (3) 27 (9) 18 (15) 15 (11) 22 (12) 31 (21) 26 (7) 12 (1)
nd 1 (0) 4 (4) 4 (4) 2 (1) 3 (1) 2 (3) 6 (2) 3 (3) 5 (5) 11 (9) 6 (2)
nd 2 (1) nq 1 (1) 5 (3) 4 (2) nq 4 (3) 1 (0) 4 (1) 13 (7) 2 (1)
nd 1 (0) nd 1 (1) 3 (4) 3 (1) nq 2 (0) 4 (7) 4 (5) 18 (6) 2 (1)
nd 1 (1) nq 1 (1) 2 (2) 2 (3) 2 (2) nq 3 (1) 3 (2) 8 (3) nq
nd 1 (1) nd 1 (0) 5 (3) 3 (1) nq 2 (1) 6 (1) 8 (2) 19 (4) 3 (2)
nd 2 (1) nq 2 (1) 13 (5) 6 (7) 3 (1) 4 (2) 19 (11) 23 (10) 32 (6) 4 (2)
a Mean values from four sampling points. b Standard deviation. c d is detected; nd is not detected. Due to the low recovery (ca. 20%), for TMP the method is suitable for the detection but not for the quantification. d Detected, but not quantified.
TABLE 4. Concentrations of Selected Organophosphorus Compounds in Martignano Lake Water Samples meana (SDb), ng/L Jun 2006 Jul 2006 Aug 2006 Sep 2006 Oct 2006 Nov 2006 Dec 2006 Jan 2007 Feb 2007 Mar 2007 Apr 2007 May 2007 Jun 2007 c
TMP TEP TCEP TPPO TPrP TCPP TDCP TPP TiBP TnBP TBEP TCP
nd 2 (2) nd nq 2 (1) nq 4 (3) 2 (1) 13 (5) 5 (3) 23 (9) 4 (2)
nd 5 (2) nqd nq 4 (2) nq 13 (5) nq 18 (5) 4 (3) 42 (11) 5 (2)
nd 3 (2) nq nq 3 (1) 2 (2) 17 (4) 2 (2) 21 (8) 19 (6) 50 (13) 3 (1)
nd 3 (1) 5 (2) 3 (3) 5 (2) 5 (1) 23 (5) 3 (0) 9 (5) 17 (3) 54 (12) 7 (3)
nd 2 (1) nq 2 (1) 2 (2) 2 (1) 5 (2) 2 (2) 10 (3) 11 (4) 8 (3) 4 (2)
nd 3 (1) nd 3 (2) 1 (1) 3 (2) 2 (1) 4 (2) 5 (3) 6 (2) 11 (6) 4 (3)
nd 1 (0) nq 1 (1) 1 (0) 3 (3) nq 3 (2) 4 (2) 9 (3) 16 (5) 2 (1)
nd 2 (1) nd 1 (0) 2 (1) nq 2 (0) 4 (3) 5 (2) 10 (3) 8 (5) 1 (1)
nd 2 (2) nd nq 2 (1) 4 (2) nq 5 (3) 3 (3) 7 (2) 13 (7) nq
nd 3 (1) nd nq 1 (0) 4 (2) nq 8 (7) 6 (3) 11 (2) 44 (19) 1 (0)
nd 2 (0) nd nq 1 (1) 2 (1) nd 4 (1) 4 (1) 5 (2) 21 (12) nq
nd 1 (1) nd nq 1 (0) nq nq 2 (2) 7 (3) 4 (1) 16 (8) 2 (2)
nd 2 (1) nq nq 3 (2) 2 (1) 2 (1) nq 12 (4) 8 (4) 17 (6) 3 (1)
a Mean values from four sampling points. b Standard deviation. c d is detected; nd is not detected. Due to the low recovery (ca. 20%), for TMP the method is suitable for the detection but not for the quantification. d Detected, but not quantified.
concentrated in the second part of the year when tourism increases greatly. Rising during the summer-autumn months, OP concentration decreases in winter, reaching a quite stable level during the spring months. This behavior may be due to three concomitant causes: (i) reduced input after tourist season; (ii) increased aerobic degradation (as proposed by Fries and Püttmann (12), the lower water temperature 1900
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resulting in higher dissolved oxygen concentrations supports aerobic degradation of the compounds); and (iii) dilution with less polluted water (the gradient temperature reversing promotes mixing with lower water layers). Correlation analysis showed that TPrP, TiBP, TnBP, TCPP, and TDCP may have the same diffuse origin with probable occasional superimposed inputs, and it also showed that OP
FIGURE 2. Comparison of tris(2-butoxyethyl) phosphate (TBEP) concentrations during one year (June 2006-June 2007) in the Albano, Vico, and Martignano lakes. pollution seems, at least partly, connected to tourism. Although Albano Lake is characterized by an anthropical impact of a more permanent type, data of nonchlorinated OP contamination in Albano and Vico basically show a similar distribution. TPrP and TBP were the most abundant OPs both in Albano and Vico lakes. TPrP maximum concentration values were reached in October (951 ng/L Vico and 486 ng/L Albano); also TnBP was found at the highest concentrations in October (636 ng/L Vico Lake) and in November (784 ng/L Albano Lake). These values agree with previous studies that found TnBP concentrations in rivers ranging from 20 to 4500 ng/L (11). The month in which all OPs showed the minimum contamination was April. Martignano Lake is the least polluted site, because, as previously described, civil and agricultural settlements are negligible. In this lake maximum TiBP and TnBP concentrations were reached in August (21 and 19 ng/L, respectively). This fact seems to confirm our hypothesis, since tourist impact in Martignano is due only to beach recreational activities which stop early in September, whereas in Vico and Albano tourism occurs also during autumn. TBEP behaves in a quite different manner; although the highest and lowest levels occurred in the same months as for TPrP and TnBP, the variation was much smaller. Maximum TBEP concentrations were 127, 115, and 54 ng/L in Albano, Vico, and Martignano, respectively, as shown in Figure 2. The relatively constant levels of TBEP found may be explained by the general use of products contianing TBEP. This compound is used as an ingredient in floor polish and floor waxes and has been reported in the literature as a drinking water contaminant (11, 27); moreover, it has been shown to be the most abundant OP in indoor dust at levels ranging from 0.014 to 5.3 g/kg (28) and in STP influents (15, 29). Therefore this trend may be explained by considering that in many cases restaurants and kiosks placed very close to lakesides discharge their waste directly into the water by means of small ducts. The explanation of data regarding chlorinated OP pollution is not straightforward. As could be inferred from the data reported in Table 5 relative to OP concentration in rainwater collected during two rainfalls in Rome and one in the Martignano Lake area, TCEP, TCPP, and TDCP water pollution in the studied sites seems to occur via atmospheric transport after emission from urban settlements and road traffic. Actually, these substances may be released from house and car interiors via their ventilation systems, since the compounds are frequently used in polyurethane polymers (21), and this could explain the relatively high concentrations found in rainwater samples collected in Rome. Probably the
TABLE 5. Concentrations of Selected Organophosphorus Compounds in Three Samples of Rainwater, Collected in Rome and near Martignano Lake rainwater, ng/L
a
TMP TEP TCEP TPPO TPrP TCPP TDCP TPP TiBP TnBP TBEP TCP
May (Rome)
June (Rome)
June (Martignano)
nd 50 161 23 15 739 448 20 30 48 115 4
nd 42 149 27 19 633 360 18 39 44 109 3
nd 12 19 nqb 2 28 108 8 6 11 38 2
a d is detected; nd is not detected. Owing to the low recovery (ca. 20%), for TMP the method is suitable for the detection but not for the quantification. b Detected, but not quantified.
transfer from air to water does not occur through rainfalls but by particulate matter fall-out, considering that the chlorinated OP concentrations in lakes Albano and Vico start to increase just when the monthly rainfalls start to decrease. Moreover, a road system surrounds these two lakes, whereas only a small road can reach the Lake Martignano tourist parking located about 1 km from the lakeshore. As reported in previous studies, chlorinated OPs are more resistant to degradation than alkyl- and aryl-OPs (16); in fact we observed a different trend in OP removal as shown in Figures 3 and 4, where concentrations of one alkyl phosphate (TPrP) and one chloroalky phosphate (TCPP) during a year are reported for the Albano and Vico lakes. The TCPP and TDCP persistence in Albano Lake during winter supports the hypothesis of car interior emission as a diffuse source for these compounds in the environment, because in this season there is heavy road traffic in the area included between Rome and the lake, and wind blows predominantly from the North quadrant (see Figure 1). Localized, sporadic OP point sources could also occur, as can be deduced from the large concentration differences among sampling sites in the same lake (see standard deviations) and also from the TDCP and TnBP high levels found in March and in November, respectively, at Albano Lake. VOL. 42, NO. 6, 2008 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
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FIGURE 3. Comparison of tetrapropyl phosphate (TPrP) concentrations during one year (June 2006-June 2007) in the Albano and Vico lakes.
FIGURE 4. Comparison of tetrachloropropyl phosphate (TCPP) concentrations during one year (June 2006-June 2007) in the Albano and Vico lakes. In Table 6 the OP concentrations found in nine wells situated around the Vico Lake basin (0.05–3 km from the lakeshore) are reported. The aim of these measurements was to ascertain if lake water infiltration into soil would carry OP contamination to groundwater. Low concentration levels of OPs were found in aqueous samples collected in wells located in the neighborhood of the lake, except for TBEP (5 of 9), and TPP + TCP (1 of 9). These results are not surprising, considering that (i) water transfer involves especially the lowest lake water layers where Op concentrations may be lower than near to the surface, due to (bio)degradation, and (ii) soil adsorption for these compounds is likely to occur. Thus, TBEP and aryl-OP contamination of wells should have a different origin. As already reported, TBPE is contained in 1902
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household cleaning products and well contamination might occur through leakage from house wastes discharged into the earthed up cesspool. The unusually high TPP and TCP concentration in well 7 (164 and 29 ng/L, respectively) might be related to the presence in its proximity of abusively discharged and buried plastic material, considering that these compounds are widely used as flame retardants in electronic commodities, especially for screens. This study shows that in closed ecosystems, such as small volcanic lakes, even in the absence of manufactory plants or STPdischarges,OPcontaminationcanoccur;thesummer-autumn tourist activities, which also imply an increased volume of traffic, probably being the main source of OP pollution. The OP concentration levels found indicate that their sources
TABLE 6. Concentration of Selected Organophosphorus Compounds in Nine Well Water Samples Located in the Neighborhood of Vico Lake ng/L
TMPa TEP TCEP TPPO TPrP TCPP TDCP TPP TiBP TnBP TBEP TCP
well 1
well 2
well 3
well 4
well 5
well 6
well 7
well 8
well 9
nd 1 nd 1 2 4 nd 10 3 4 34 nd
d 1 8 5 5 12 nd 7 5 5 53 nd
nd nd nd nd 4 nd nd nd 3 2 18 nd
nd nd nd nd nd 2 nd 4 nd nd 35 nd
nd nd nd 1 nd nq nd 6 nq nq 5 nd
nd nd nd 2 nq nq nd 2 nd nd 5 nd
nd nqb nd 2 1 3 nd 164 10 10 26 29
nd nd nd nq nd nd nd 2 nd nd 4 nd
nd nd nd 3 nd nd nd 6 nd nd nq nd
a d is detected; nd is not detected. Owing to the low recovery (ca. 20%), for TMP the method is suitable for the detection but not for the quantification. b Detected, but not quantified.
were predominantly diffuse and in relation to the volume of human presence. Moreover, although the levels of the most abundant OPs in the studied environment appear to be significantly lower than their acute toxicity values (3–8), the effects of long-term exposure to OPs could not be negligible.
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