Environ. Sci. Techno/. 1995, 29, 1542-1550
Sediment Porewater Partitioning of Polycyclic Aromatic Hydrocarbons in Three Cores from Boston Harbor, Massachusetts S U S A N E . MCGRODDYtm5 A N D J O H N W. FARRINGTON**t,* University of Massachusetts a t Boston, Boston, Massachusetts 02125, and Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543
Polycyclic aromatic hydrocarbon (PAH) concentrations were measured in sediments and porewaters isolated from three cores from Boston Harbor, MA. Measured porewater PAH concentrations were significantly lower than the concentrations predicted by two-and three-phase equilibrium partitioning models. W e hypothesize that only a fraction of the measured sediment PAH concentrations was available to partition rapidly into sediment porewaters.
Introduction Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous contaminants of lacustrine and coastal marine sediments (1-4). PAHs have both natural and anthropogenic sources (1, 2, 5). The two main sources of PAHs in most coastal sediments are combustion processes ranging from fossil fuel combustion to forest fires and the release of uncombusted petroleum products. In order to better understand the mobility and bioavailability of PAHs contained in sediments, the concentration of these compounds in sediment porewaters must be determined. Nonpolar organic compounds such as PAHs and polychlorinated biphenyls (PCBs)have very low aqueous solubilities. However, the presence of porewater organic colloids can enhance the porewater concentrations of these compounds beyond concentrations predicted by their solubilities (6-11). Previous studies of PAH environmental biogeochemistry suggest that the source of the specific PAH compounds affects their observed environmental behavior. Specifically, combustion-generated PAHs appear to be more strongly associated with particles than petroleum-derived PAHs. Prahl and Carpenter (12)suggest that combustion-generated PAHs may not be available to participate in sorption and desorption processes based on measured PAH concentrations associated with specific sediment size fractions (121. Pyrogenic PAHs appear to be unavailable to partition into the water column (13)and porewater (14). In addition, combustion-generated PAHs appear to be less bioavailable than petroleum-derived PAHs (15). Previous studies on gaslparticle distributions of PAHs associated with soot particles have shown lower gas phase concentrations than predicted from the compounds’ vapor pressures, suggesting that a fraction of the soot PAH is nonexchangeable or unavailable to equilibrate with the gas phase (16-19). A recent study on the gaslparticle distribution of perylene showed that a fraction of the perylene sorbed to combustion particles was resistant to desorption at temperatures up to 650 K (20). A spectroscopic study on the structure of hexane soot, including FT-IR, Raman, and I3C NMR revealed the highly aromatic nature of the soot matrix (21). The ratio of aromatic carbon:total organic carbon was calculated to be 0.89. In addition, significant concentrations of PAHs were extracted from hexane soot particles. The soot particles were observed to swell as a result of the solvent extraction (22). The authors suggest that the PAH compounds are adsorbed in the pores of the soot particles and released during solvent extraction. Boston Harbor sediments are known to be heavily contaminated with PAHs (4,23). We measured porewater and sediment concentrations of a suite of PAH compounds in three cores from Boston Harbor. Our colleagues measured total and dissolved porewater organic carbon concentrations in addition to conducting sorption experi* Author to whom correspondence should be addressed. E-mail:
[email protected]. Fax: 508-457-2188. + University of Massachusetts at Boston. Woods Hole Oceanographic Institution. 5 Current address: U S . Geological Survey, P.O. Box 25046, MS 408, Denver Federal Center, Denver, CO 80225.
1542 ENVIRONMENTAL SCIENCE &TECHNOLOGY / VOL. 29, NO. 6.1995
0013-936X/95/0929-1542$09.00/0
C 1995 American Chemical Society
22'
42'20'
4 0'
46'
BOSTON HARBOR
*
42.44'
04' 0 2' 74'00' FIGURE 1. Sampling sites in Boston Harbor, MA.
58'
ments with sediments and porewater organic colloids (11, 24). Our study was designed to measure in situ partition coefficientsand to compare them with binding coefficients measured in laboratory sorption experiments using porewater organic colloids and sediment samples from the same cores.
Materials and Methods Sampling Protocol. Three large-volume box cores were taken from three sites in Boston Harbor: (1) Fort Point Channel (42'21'22'' N, 71'02'41'' W, water depth 7 m), (2) Peddocks Island (42'17'20" N, 70"55'44"W, water depth 6 m), and (3) Spectacle Island (42'19'46" N, 70'59'34" W, water depth 9 m) (Figure 1). The cores were obtained using a Sandia-Hessler Type MK3 sediment corer (0.25 m2 x 70 cm box). Care was taken during the sectioning process to minimize the exposure of the cores to atmospheric oxygen by transporting them under a nitrogen headspace introduced between a plexiglass cover and the core top. Sectioning of the cores was completed within 1-4 h of sampling and consisted of 1-2 cm sections in the top 20 cm. The remainder of each core was sectioned into 2-4 cm sections. Sediment samples were stored refrigerated in solvent-rinsed glass jars with minimal headspace. Porewater Isolation. Within 72 h of sampling, the sediment sections were centrifuged to separate the pore-
56'
54'
52'
70'50'
water from the sediment. The Fort Point Channel sediments were centrifuged in 250 mL glass centrifuge bottles at 600g for 20 min. The Peddocks Island and Spectacle Island sediments were centrifuged in 750 mL polycarbonate centrifuge bottles at 1200g for 20 min. The two methods of centrifugation were compared, and no significant differences were found between the PAH concentrations measured in porewaters isolated by the two methods (25). DOC and Sediment Organic Carbon Analysis. Immediately following centrifugation, a subsample of the porewater was collected for dissolved organic carbon (DOC) analysis. The DOC was measured at Dr. P. M. Gschwend's lab at MIT using an Ionics 555 TOC Analyzer (Ionics Inc, Watertown, MA). The remaining porewater was filtered through a precombusted 1.2ym glass fiber filter. Porewater samples were refrigerated in 500 mL and 1 L amber glass bottles with minimal headspace and approximately 10% dichloromethane added to inhibit microbial activity. Subsections of each sediment section were reserved for CHN analysis. The CHN analysis was performed using a Perkin-Elmer2400 CHN analyzer. Portions of the remaining sediment from each core section were frozen at -40 "C until further analyses. Extraction Protocol. Sediment and porewater samples were analyzed for 31 PAH compounds. Prior to extraction, the samples were spiked with deuterated recovery surVOL. 29, NO. 6, 1995 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
1543
Average PAH Recoveries recovery surrogate sample FPC porewater FPC sediment SI porewater SI sediment PI porewater PI sediment
fluorene-&
51.9 f 12.2( n = 13) 65.0i 11.6 ( n = 17) 60.4i 19.3 ( n = 9) 92.1 f 29.4 ( n = 1 1 ) 51.1 i 18.7 ( n = 15) 77.1 i 25.5 ( n = 21)
enthracene-&o
73.9f 14.0 ( n = 13) 67.4f 11.6 ( n = 17)
not added not added
not added not added not added not added
107 f 20.5 ( n = 9) 115 f 23.8 ( n = 6) 91.0f 13.4( n = 15) 108 f 21.8 ( n = 18)
rogates (fluorene-dlo,anthracene&, terphenyl-dlo,perylene-dlz). The porewater samples were liquid-liquid extracted with 4 x 50 mL dichloromethane (DCM),and the four extracts were combined ( 7 ) . The sediment samples (-20 g wet wt) were extracted on a shaker table using 1 x 30 mL methanol and 3 x 25 mL DCM. The methanol fraction was extracted with hexane, and the hexane extract was combinedwith the DCM extracts (26). Further extraction of the sediment samples did not release measurable concentrations of PAH. Sediment and porewater extracts were reduced in volume using rotary evaporation followed by further concentration under a stream of high-purity nitrogen. Extracts of both sediment and porewater were passed through an anhydrous sodium sulfate column in order to remove residual water. Elemental sulfur was removed by passing the extracts through an activated Cu column. The copper was activated using concentrated HCl followed by exhaustive solvent rinses with methanol, acetone, dichloromethane, and hexane. Chromatographic Separations. The entire porewater extract was applied to a 1.0 x 30 cm glass chromatography column packed with 7 g of 5% deactivated silica gel (100200 mesh). The following sequential elution scheme was used: F1, 20 mL of hexane; F2, 15 mL of 25% dichloromethane (DCM) in hexane plus 5 mL of 50% DCM in hexane; and F3,15 mL of DCM. The PAHs were contained in F2. Each fractionwas concentrated by rotary evaporation to a final volume of -1 mL. The porewater fractions were stored in the freezer in amber glass vials. Approximately one-third of the total sediment extract (precise fraction was determined gravimetrically) was applied to a chromatography column packed with 7 g of 5% deactivated silica. The elution scheme was F1,25 mL of 25% DCM in hexane and F2, 25 mL of 50% DCM in hexane. The first fraction (Fl) was applied to a second column with the same elution scheme used for the porewater extract. Care was taken throughout the extraction and analysis of these samples to minimize their exposure to light. PAH Quantitation. The porewater fractions were brought up in 20-5OpL of internal standard solution: Fort Point Channel (FPC),terphenyl-dlo; Spectacle Island (SI) and Peddocks Island (PI), biphenyl-dlo and chrysene-dlz. The PAHs were measured quantitatively by gas chromatographylmass spectroscopy. The FPC samples were analyzed on a Finnigan 4510B gas chromatograph/quadropole mass spectrometer with a 30 m DB-5 column and helium as a carrier gas. The SI and PI porewater samples and FPC sediments were analyzed on a Carlo Erba 4160 gas chromatograph interfacedwith a Finnigan 4510B quadrople mass spectrometer programmed from 70 "C to 320 "C at 5 deglmin and held at 320 "C for 15 min. 1544
terphenyl-$0
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perylene-42
107 f 36.4( n = IO) 98.7f 22.7 ( n = 17) 116 f 19.8( n = 9) 104 f 14.2( n = 3) 96.1 117.3( n = 15) 102 f 8.18( n = 2)
All porewater PAH concentrations were obtained from response factors generated by calibration with authentic quantitative standards and application of the FiMigan Autoquant program to verify the identity of the analytes and calculate concentrations. PAHs in the SI and PI sediments were analyzed by GC/ FID on a Carlo Erba 4160 gas chromatograph with an oncolumn injector, 30 m DB5 column, hydrogen as a carrier gas; a 1pl injection at 70 "C with an initial hold of 1 min; heating at a rate of 3 deglmin to 250 "C, immediately followed by heating at 4 deg/min to 310 "C, finally heating at 6 deg/min to 320 "C for 15 min. The gas chromatograph response factors were obtained by calibrationwith the same quantitative standards used to calibrate the mass spectrometer. Procedural blanks were analyzed concurrently with the porewater and sediment samples. The porewater blanks consisted of 500 mL of double distilled H20 extracted in the same manner as the porewater samples. The sediment blanks were solvent-extracted sand that had been baked in a muffle furnace at 450 "C overnight and extracted in the same manner as the sediment samples. The PAH concentrations in the sediment blanks were either not detectable or several orders of magnitude below the sample PAH concentrations. The estimated limit of detection (LOD) was 10 ng of individual PAH/g dry wt of sediment (25). The SI and PI porewater blanks were analyzed concurrently. PAHs were either not present or present in trace amounts, below the estimated LOD (2-4 ng of individual PAHIL). The FPC porewater blanks contained significant concentrations of low molecular weight PAHs (Le., biphenyl, naphthalene, and phenanthrene). Less significant fluoranthene and pyrene concentrations were also measured. We determined that the source of these compounds was contaminated double distilled H20 used for the porewater blanks. In this case, the blankvalues do not reflect potential contamination of the porewater samples. None of the reported sediment and porewater concentrations were corrected for blank concentrations. The LOD calculated for the porewater samples depended on the initial volume of the porewater sample. The LOD values ranged from 10 ng/L for a 0.20 L sample to 2.0 ng/L for a 1.0 L sample. The accuracy of our quantitation was tested by analyzing a NBS standard marine sediment (NBS standard reference material 1941). Our measured concentrations for pyrene and fluoranthene were within 1 SD of the certified concentrations and the measured concentrations, for phenanthrene and benzo [alpyrenewere within 20% of the certified concentrations. Recoveries of the deuterated recovery surrogates that were added prior to extraction are summarized in Table 1.
30
2o
c
t
.0 15
m
I
0 0
0.2
0.4 0.6 0.8 1 sediment %lipid (%dry wt. sediment)
1.2
FIGURE 2. Sediment C,:N plotted against the sediment percent lipid for all three sediment cores: Fort Point Channel (B),Spectacle Island (01,and Peddocks Island (4.
The measured porewater and sediment concentrations have not been corrected for the recoveries. Our recoveries were similar to those reported by others (14). Recovery efficiencies for the porewater samples were less than those for the sediment samples due to greater evaporative losses as well as losses to glassware surfaces.
Results and Discussion Sediment Characteristics. The ratios of the organic carbon to nitrogen (Corg:N)calculated for the sediments from the three cores range from 8.0-11.4 for Peddocks Island to 14.2-24.8 for Fort Point Channel. The C,,,:N signature of the PI sediment was typical of estuarine sedimentary organic matter represented by the Station M site in Buzzards Bay (28)and other stations (29). The SI and FPC cores appear to have received significant inputs of organic carbon from sources relatively depleted in nitrogen. Potential sources include petroleum products, woody debris, and terrestrial soils. It is difficult to identify unique sources of organic matter for sites such as Fort Point Channel, where there is a wide array of potential sources. Plotting C,,,:N values versus the sediment lipid content (Figure 2) for all three cores shows PI sediments with the lowest lipid content and Corg:N values. The FPC sediment samples separate into two distinct groups. Sediments from 17-31 cm depth have relatively low lipid contents and high C:N ratios. Sediments from 0-17 cm depth have C,,,:N ratios that increase with increasing lipid content. The extremely high C,,,:N ratios combined with the high lipid content of these sediments may be indicative of the presence of petrochemical products. The SI sediments were intermediate between the PI and FPC values. The organic carbon content of the FPC sediments ranged from 4 to 6% Corg The SI and PI sediments ranged from 2 to 4% Corg. Organic carbon profiles for all three cores are
plotted in Figure 3. The organic carbon contents of the three sediment cores were similar to the values reported for a series of cores taken throughout Boston Harbor (27). Depth Proflles of Polycyclic Aromatic Hydrocarbon Concentrations in Sediments and Porewaters. Porewater and sediment concentration profiles of phenanthrene, fluoranthene, pyrene, and benzo[ulpyrenefor all three cores are presented in Figure 3. These compounds were selected as representative PAHs because they have a range of molecular weights and solubilities (Table 3). They were also major components of the mix of PAHs measured in the porewaters and sediments at each site. The highest PAH concentrations in both sediments and porewaterswere seen in the FPC core (Figure3a). Extremely high PAH concentrations had been previously measured in FPC surface sediments (23). Pyrene was the most abundant PAH compound measured in both the sediment and the porewater samples. The maximum in porewater PAH concentrations at 15 cm depth corresponded to a sediment PAH concentration maximum at the same depth. The shallow, one-point maximum in sediment PAH concentrations at approximately-2 cm depthwas not reflected in the porewater profile. SI porewater PAH concentrations were approximately an order of magnitude less than those measured at Fort Point Channel. SI sediment concentrations were approximately one-fourth of the FPC sediment concentrations (Figure 3b). The lowest sediment PAH concentrations were measured in the PI core (Figure 3c): sediment concentrations were approximately one-half the concentrations measured at Spectacle Island; porewater PAH concentrations were similar to those measured for Spectacle Island porewaters. PAH Composition. In order to determine whether or not there were significant compositional differences between the porewater and sediment samples, the following ratios were calculated: phenanthrene:anthracene,pyrene: fluoranthene, and benzo[elpyrene:benzo [alpyrene. The ratios were chosen on the basis of the presence of these compounds in our quantitative PAH standard, the presence of these PAHs in appreciable concentrations in most of our porewater and sediment samples, and the availability of previously reported values of these ratios for a range of potential sources. In general,there were no significant differences between the porewater and sediment compositions as determined by these ratios (Table2). However, the pyrene:fluoranthene ratios in the FPC and SI porewater samples were sigdicantly higher than the ratios in the corresponding sediment samples. The predominance of pyrene in the FPC porewaters was particularly dramatic. We have not identified a unique source with this compositional signal. An enrichment in pyrene relative to fluoranthene is seen in asolvent-refined coal heavy distillate (SRC I1 coal liquid) (31) and in a synthoil created from the catalytichydrogenation of coal (coal synthoil C) (32)(Table 2). There are several former coal gasification plants located on the Mystic River (33). It is possible that wastes from these plants could produce the PAHs signals we observed. However, we do not have sufficient data to definitively idenufy the source of these compounds. In all three cores the composition of the porewater PAH was not simply controlledby the solubilitiesof the individual PAH. In all porewater samples the concentrations of benzo[a]pyrene were greater than or equal to the concenVOL. 29. NO. 6,1995 /ENVIRONMENTAL SCIENCE & TECHNOLOGY
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8
0
2
4
8
8
1 0 1 2 1 4 1 6 0
Depth (c m)
5
10
15
20
25 30
35 Sediment percent COrg 100 600 1100 1600 21002840 3100 3600 4100 4800
;
2:
depth (cm) 4:
1
.
1 1 1
I'
!
6:
1 1
1
0:
) 1
lo: 12: 14:
16: 1
8
8
5
Sediment percent COrg
10 15
20 25
30 35
4a Sedimnt percent COrg
40
FIGURE 3. Sediment (left) and porewater (right) PAH concentrations profiles for all three cores: (a) Fort Point Channel (lp ng/g dry wt of sediment), (b) Spectacle Island, and (c) Peddocks Island (ng/g dry wt of sediment); porewater concentrations, ng/L of porewater. (B) Phenanthrene, (A) fluoranthrene, ( x ) pyrene, and ( 0 )benzo[a]pyrene; (- -1 % Cow.
-
1546 m ENVIRONMENTAL SCIENCE &TECHNOLOGY / VOL. 29, NO. 6.1995
TABLE 2
Selected PAH Ratios sample
phenenthrene:anthrecene
FPC porewater FPC sediment
3.29 3.88 3.33 4.66 3.21 4.74 12
SI porewater SI sediment PI porewater PI sediment Boston aira gasoline exhaustb street dustC creosoted no. 2 fuel oile SRC II coal liquidf coal synthoil Cg
pyrenedluoranthene
benzo[elpyrene:benzo[a]pyrene
34.54 f 24.29 2.49 f 1.22 5.94 f 6.37 1.21 f 0.19 0.908 f 0.361 0.903 i.0.101 0.77 1.67 0.98 0.68 1.11 5.08 ’18.4
1.01 f 0.21 (n = 10) 0.712 f 0.099 ( n = 17) 1.53 f 0.73 ( n = 10) 1.26 f 0.21 ( n= 5) 2.72 f 2.54 ( n= 14) 1.09 f 0.44 ( n = 18) 1.8 13 1.04 0.99 0.2
f 2.37 f 0.53 f 1.33 f 1.64 f 1.65 f 1.94
4.13 50 38
> 1.08
See ref 3. Giger, W.; Schaffner, C. Anal. Chem. 1978,50,243-249. Takada, H.; Onda, T.; Ogura, N. Environ. Sci. Technol. 1990,24, 1179-1 186. Carey, D. A.; Farrington, J. W. Estuar. Coast. Shelf Sci. 1989,29,97-113. e Pancirov, R. J.; Brown, R. A. Proc. Conf Prev. Control Oil Pollut. 1975, 103-113. ‘See ref 31. g See ref 32. a
TABLE 3
Physical Properties and Average log Koc’Values for Selected PAHs Phenanthrene
fluoranthene
pyrene
benzo[a]pyrene
aq sol (mol/m3)a log Kowa lit. log KO, measd log KO:
6.62 x 10-3 4.57 4.12b
1.3 x 10-3 5.22 4.79=
6-67 x 10-4 5.18 4.80d
1.5 x 10-5 5.98 5.8lC
FPC
6.07 f 0.34 ( n = 12) 7.03 f 0.32 ( n= 10) 6.39 f 0.49 ( n= 17)
6.56 f 0.28 ( n = 17) 6.66 f 0.43 ( n = 10) 6.08 f 0.40 ( n = 17)
5.50 f 0.41 ( n = 17) 6.61 f 0.42 ( n = 10) 6.06 f 0.49 ( n = 17)
6.00 f 0.55 ( n = 10) 6.28 f 0.34 ( n = 8) 6.17 f 0.75 ( n= 13)
SI
PI
a Miller, M. M.; Wasik, S.P.;Huang, G.-L., Shiu; W.-Y.; Mackay, D. Environ. Sci. Technol. 1985, 79,522-529. 70, 833-846. See ref 14. See ref 36.
trations of phenanthrene despite the fact that phenanthrene is more soluble than benzo(a)pyrene. There were no samples in which the aqueous solubilities of these compounds were exceeded. In Situ Partition Coefflcients. In order to compare the partitioning behavior of these compounds for three cores with a range of PAH concentrations and organic carbon contents, the apparent organic carbon normalized partition coefficients (KO,? were calculated:
Kp‘ = c,/c, where c, is the solid phase concentration, casis the aqueous phase concentration, and foc is the sediment fraction of organic carbon. The apparent organic carbon normalized partition coefficients (IC,:) measured in all three cores were higher than the predicted partition coefficients for all four compounds (Table3). This discrepancywas largest for the lowest molecular weight compound, phenanthrene. The log KO, values measured for all four compounds were remarkably similar despite the range of solubilities and range of predicted KO,values that they represent. The log &‘ profiles of the three cores show no significant trends with depth. Chin and Gschwend (1992, ref 11) conducted fluorescence quenching experiments and sediment sorption experimentst o measure the colloidal and sediment partition coefficientsfor pyrene and phenanthrene with subsamples of the same sediment core sections and porewater samples that we analyzed. The sediment sorption experiments were
Karickhoff, S.W. Chemospherel981,
conducted with a high water:sediment ratio in order to minimize the effect of dissolved organic material on the measured partition coefficient. The measured colloidal binding coefficients and colloidal organic carbon concentrations suppoqt the application of a three-phase equilibrium partitioning model to describe in situ PAH partition behavior (11). Porewater colloidal organic carbon concentrations were measured by ChinandGschwend (1991,ref24). Thehighest concentrations of colloidal organic carbon were seen in the FPC porewaters (maximum,22.6 mg of C/L). The lowest concentrationswere measured in the PI porewaters (maximum, 5.3 mg CIL). The colloidal fraction of the total dissolved organic carbon was measured as the difference between the total DOC and the DOC concentration remaining after ultrafiltration with a 3000 molecular weight cutoff (600 molecular weight cutoff based on the configuration of random coil macromolecules) (24). The measured porewater PAH concentration contained both dissolved and colloidally bound PAH. Therefore,based on the results of the sorption experiments,we would predict that the in situ partition coefficients (KO:) would be lower than the sediment partition coefficients measured in the sorption experiments. The presence of colloidal material with significant colloid binding coefficients (Z&) should result in decreased KJ values (eq 3). The partition coefficients determined for PCB congeners in these cores were well-predicted by eq 3 (25): Kd’ =
foc,~cs
(3)
1 +foccKocc where fo,, is the sediment fraction of organic carbon (g of VOL. 29, NO. 6,1995 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
1547
Taw 4
Measured Pyrene and Phenanthrene log KO,Values from Chi4 and Gschwend (11) and in Situ log KO,’ Values (This Study) lo9 La
in situ
colloid
sed
log Koc’
5.05 5.00 4.88 4.71
5.20 5.18 4.99 5.23
5.51 5.34 5.31 7.43
4.42
4.30
5.77
pyrene FPC, 7-9 cm FPC, 15-17 cm FPIC, 25-29 cm SI, 14-16 cm
necessary to support the observed porewater concentration. The fraction of the total sediment PAH that appears to be equilibrated with the measured porewater concentration will be defined as the “availablefor equilibriumpartitioning” (AEP) fraction of the total sediment PAH concentration. Measured sediment and colloidal partition coefficients can be combined with measured porewater concentrations of organic colloids,phenanthrene and pyrene, to determine the AEP fraction of the phenanthrene and pyrene sediment concentrations. This calculation assumes that the AEP fraction of the sediment concentration has come to equilibrium with the porewater concentration:
phenanthrene FPC, 25-29 cm “See ref 11.
Corg/gof sediment),Kocsis the sediment GC(mL/gsediment Cor,), foe, is the colloidal fraction of organic carbon (g of Co,,/mL), and Koccis the colloidal KO, (mL/g of colloidal Cor,)
(28).
However, the in situ phenanthrene and pyrene KO< values were higher than the sediment &
