3.1. PAHs concentrations in water dissolved phase
The concentrations in the water dissolved phase (DP) of total PAHs detected at 10 locations of the Volturno River and its Estuary, during the four campaigns, ranged from 64.3 (site 8) to 1429.1 (site 1) ng L− 1 with a mean value of 602.6 ± 319.3 ng L− 1 (Table 1). These values ranged from 3.44 to 174.4 ng L− 1 with a mean value of 58.4 ± 39.5 ng L− 1 for 2-ring PAHs (Nap), from 19.9 to 805.1 ng L− 1 for 3-ring PAHs (Acy, Ace, Flu, Phe, An), from 12.7 to 244.1 ng L− 1 for 4-ring PAHs (Fl, Pyr, BaA, Chr), from 9.48 to 151.1 ng L− 1 for 5-ring PAHs (BbF, BkF, BaP, DahA) and from 17.6 to 74.6 ng L− 1 for 6-ring PAHs (BghiP, InP). The compositional profiles of PAH in the dissolved phase, which indicate that 2- and 3-ring PAHs were abundant in all sampling sites, representing on average over 62% of all PAHs. In addition, the suspected carcinogenic 5–6-ring PAHs was present in low concentrations, accounting for only 17% of total PAHs. The prevalence of low molecular weight PAHs (2–3-ring) in the water could be explained by their high water solubility and relatively high vapor pressures [36, 37, 38]. Compared with the water of polluted rivers in other parts of the world (Table 2), the concentration of ΣPAHs in the the Volturno River dissolved phase (64.3-1429.1 ng L− 1) was much higher than those found in the Xijiang River, China by Deng et al. [39], in the Yellow River (China) by Li et al. [40], in the Songhua River (China) by Ma et al. [41], in the Wyre River, England by Moeckel et al. [42], in the Elbe and Weser Rivers, Germany by Siemers et al. [43], in the Marseilles coastal area, France by Guigue et al. [44] and in the Tiber River (Italy) by Patrolecco et al. [45] and Montuori et al. [22]; these levels were however lower than those found in the Daliao River, China by et al. [46], in the Yellow River (China) by Zhao et al. [47], in the Songhua River (China) by Zhao et al. [48], in the Daliao River estuary (China) by Zheng et al. [49], in the Gomti River, India by Malik et al. [50], in the Cauca River, Colombia by Sarria-Villa et al. [8], in the Almendares River, Cuba by Santana et al. [51] and in the Buffalo River estuary, South Africa by Adeniji et al. [52]. Based on these results, the levels of PAHs in the dissolved phase in the Volturno River are comparable to those found in the Henan Reach of Yellow River, China by Sun et al. [53], in the Gulf of Tunis, Tunisia by Mzoughi and Chouba [54], in the Danube River, Hungary by Nagy et al. [55] and in the Sarno River by Montuori and Triassi [22].
Table 2
Concentration ranges and mean value of PAHs in the water dissolved phase (DP), suspended particulate matter (SPM) and sediments from recent studies of different rivers, estuaries and coasts in the world.
|
Area
|
References
|
Number PAHs
|
Range ∑PAHs
|
Mean ∑PAHs
|
|
Water (ng L− 1)
|
|
|
|
|
|
Xijiang River, China
|
Deng et al. [39]
|
15
|
21.7–138.0
|
-
|
|
Yellow River, China
|
Li et al. [40]
|
15
|
179.0-369.0
|
248.2
|
|
Daliao River, China
|
Guo et al. [46]
|
18
|
570.2-2318.6
|
-
|
|
Henan Reach of Yellow River, China
|
Sun et al. [53]
|
16
|
144.3–2361.0
|
662.0
|
|
Songhua River, China
|
Ma et al. [41]
|
15
|
14.0-161.0
|
33.9
|
|
Yellow River, China
|
Zhao et al. [47]
|
16
|
548.0-2598.0
|
1375.0
|
|
Songhua River, China
|
Zhao et al. [48]
|
16
|
163.5-2746.2
|
934.6
|
|
Daliao River estuary, China
|
Zheng et al. [49]
|
16
|
71.1-4255.4
|
748.8
|
|
Gomti River, India
|
Malik et al. [50]
|
16
|
60-84210.0
|
10330.0
|
|
Cauca River, Colombia
|
Sarria-Villa et al. [8]
|
12
|
52.1-12888.2
|
2344.5
|
|
Almendares River, Cuba
|
Santana et al. [51]
|
14
|
836.0-15811.0
|
2512.0
|
|
Buffalo River Estuary, South Africa
|
Adeniji et al. [52]
|
16
|
ND-24910
|
-
|
|
Gulf of Tunis, Tunisia
|
Mzoughi and Chouba [54]
|
22
|
139.2-1008.3
|
-
|
|
Wyre River, England
|
Moeckel et al. [42]
|
28
|
2.7–20.0
|
-
|
|
Elbe and Weser Rivers, Germany
|
Siemers et al. [43]
|
16
|
10.0–40.0
|
-
|
|
Marseilles coastal area, France
|
Guigue et al. [44]
|
32
|
8.1–405.0
|
-
|
|
Danube River, Hungary
|
Nagy et al. [55]
|
16
|
25.0-1208.0
|
122.6
|
|
Tiber River, Italy
|
Patrolecco et al. [45]
|
6
|
23.9–72.0
|
43.4
|
|
Tiber River, Italy
|
Montuori et al. [30]
|
17
|
1.75-607.48
|
90.46
|
|
Sarno River, Italy
|
Montuori and Triassi [22]
|
17
|
12.4-2321.1
|
739
|
|
SPM (ng L− 1)
|
|
|
|
|
|
Xijiang River, China
|
Deng et al. [39]
|
15
|
1.4–58.1
|
29.8
|
|
Yellow River, China
|
Li et al. [40]
|
13
|
54.0-155.0*
|
-
|
|
Daliao River, China
|
Guo et al. [46]
|
18
|
151.0-28483.8
|
-
|
|
Henan Reach of Yellow River, China
|
Sun et al. [53]
|
16
|
506.6-10510.0*
|
4100.0*
|
|
Songhua River, China
|
Ma et al. [41]
|
15
|
9.21–83.1
|
26.4
|
|
Yellow River, China
|
Zhao et al. [47]
|
16
|
1502.0-11562.0*
|
5591.0*
|
|
Daliao River estuary, China
|
Zheng et al. [49]
|
16
|
1969.9-11612.2
|
4015.7
|
|
Gulf of Mexico, Mexico
|
Adhikari et al. [21]
|
43
|
0.9-7.0
|
3.2
|
|
Gulf of Tunis, Tunisia
|
Mzoughi and Chouba [54]
|
22
|
909.9-8222.4*
|
-
|
|
Tiber River, Italy
|
Patrolecco et al. [45]
|
6
|
37.6–353.0
|
|
|
Tiber River, Italy
|
Montuori et al. [30]
|
17
|
4.53-473.39
|
111.51
|
|
Sarno River, Italy
|
Montuori and Triassi [22]
|
17
|
6.1-778.9
|
-
|
|
Sediment (ng g− 1)
|
|
|
|
|
|
East China Sea, China
|
Zhao et al. [62]
|
16
|
57.5-364.5
|
166.2
|
|
Yellow River, China
|
Li et al. [40]
|
13
|
31.0-133.0
|
76.8
|
|
Daliao River, China
|
Guo et al. [46]
|
18
|
102.9-3419.2
|
-
|
|
Henan Reach of Yellow River, China
|
Sun et al. [53]
|
16
|
16.4–1358.0
|
182.0
|
|
Yellow River, China
|
Zhao et al. [47]
|
16
|
181.0-1583.0
|
810.0
|
|
Bohai Bay, China
|
Li et al. [58]
|
16
|
24.6-280.6
|
79.3
|
|
Yellow River Estuary, China
|
Liu et al. [63]
|
15
|
89.5–208.0
|
140.5
|
|
Erjien River, Taiwan
|
Wang et al. [59]
|
16
|
22.0-28622.0
|
737.0
|
|
Caspian sea coast, India
|
Yancheshmeh et al. [68]
|
23
|
1294.0-9009.0
|
3228.0
|
|
Baffin Bay, Canada
|
Foster et al. [69]
|
66
|
341.0-2693.0
|
-
|
|
Cocó and Ceará Rivers, Brazil
|
Cavalcante et al. [70]
|
17
|
3.0-2234.8
|
-
|
|
Ibirité Reservoir, Brazil
|
Mozeto et al. [64]
|
16
|
79.8-219.9
|
129.5
|
|
Tampa Bay, Florida
|
Lewis and Russell [65]
|
16
|
1.7-147.9
|
18.0
|
|
Bahia Blanca Estuary, Argentina
|
Oliva et al. [10]
|
17
|
19.7-30054.5
|
1798.5
|
|
Gulf of Mexico, Mexico
|
Adhikari et al. [21]
|
43
|
70–162
|
120
|
|
Cauca River, Colombia
|
Sarria-Villa et al. [8]
|
12
|
ND-3739.0
|
1028.0
|
|
Buffalo River Estuary, South Africa
|
Adeniji et al. [52]
|
16
|
ND-7792
|
-
|
|
Yellow Sea, China
|
Li et al. [58]
|
16
|
148.3-907.5
|
548.6
|
|
Ammer River, Germany
|
Liu et al. [9]
|
16
|
112.0-22900.0
|
8770.0
|
|
Portimão Harbor, Portugal
|
Bebianno et al. [71]
|
16
|
218.0-1690.0
|
-
|
|
Danube River, Hungary
|
Nagy et al. [55]
|
16
|
8.3-1202.5
|
170.0
|
|
Gulf of Tunis, Tunisia
|
Mzoughi and Chouba [54]
|
22
|
363.3-7026.4
|
-
|
|
Durance River, France
|
Kanzari et al. [73]
|
16
|
57.0-1528.0
|
-
|
|
Huveaune River, France
|
Kanzari et al. [72]
|
16
|
571.7-4234.9
|
1966.00
|
|
Iberian coast, Spain
|
León et al. [74]
|
13
|
5.3-2627.4
|
-
|
|
Ría de Arousa, Spain
|
Peréz-Fernández et al. [6]
|
35
|
45.0-7901.0
|
-
|
|
Marano and Grado Lagoon. Italy
|
Acquavita et al. [60]
|
16
|
50.0-1026.0
|
-
|
|
Italian Marine Protected Areas, Italy
|
Perra et al. [66]
|
16
|
0.7–1550.0
|
155.3
|
|
Gulf of Trieste, Italy
|
Bajt [75]
|
16
|
214.0-4416.0
|
-
|
|
Priolo Bay, Italy
|
Di Leonardo et al. [61]
|
18
|
56.4-847.1
|
-
|
|
Tiber River, Italy
|
Patrolecco et al. [45]
|
6
|
157.8-271.6
|
215.2
|
|
Tiber River, Italy
|
Minissi et al. [67]
|
13
|
4.5-652.2
|
-
|
|
Tiber River, Italy
|
Montuori et al. [30]
|
17
|
36.21–545.60
|
155.26
|
|
Sarno River, Italy
|
Montuori and Triassi [22]
|
17
|
5.5-678.6
|
266.9
|
|
This study
|
DP
|
17
|
64.3-1429.1
|
602.6 ± 319.3
|
|
SPM
|
143.3-444.9
|
264.7 ± 83.3
|
|
Sediment
|
434.8-872.1
|
659.1 ± 136.9
|
| * ng/g |
| ND: not detectable |
3.2. PAHs concentrations in suspended particulate matter
The concentrations of PAHs in the suspended particulate matter (SPM) samples range from 149.3 ng L− 1 in site 8 to 444.9 ng L− 1 in site 1 (mean value of 264.7 ± 83.3 ng L− 1), as shown in Table 1. The concentrations of PAHs detected ranged from 4.05 to 38.9 ng L− 1 with a mean value of 15.1 ± 8.1 ng L− 1 for 2-ring PAHs (Nap), from 51.8 to 154.1 ng L− 1 for 3-ring PAHs (Acy, Ace, Flu, Phe, An), from 39.6 to 181.0 ng L− 1 for 4-ring PAHs (Fl, Pyr, BaA, Chr), from 26.5 to 103.1 ng L− 1 for 5-ring PAHs (BbF, BkF, BaP, DahA) and from 17.8 to 66.6 ng L− 1 for 6-ring PAHs (BghiP, InP). The compositional profiles of PAHs in SPMs show that 4-, 5-, 6-ring PAHs were abundant at most sampling sites, accounting for 25%, 20%, and 12% of ΣPAHs in SPMs, respectively.
The proportion of high molecular weight PAHs increased to 57%, much above than in dissolved samples, where it was 38%. The results indicated that high molecular weight PAHs were preferentially sorbed by the particulate matter due to its high hydrophobicity and hardly biodegraded, in agreement with the PAHs partition theory [45, 54, 47]. In fact, the partition coefficients (Kp, defined as the ratio of the concentration of a chemical associated with SPM to that in the DP: Kp = CSPM/CDP) showed an increasing trend of high-ring compounds in their SPM partitioning (average value of 0.80, 0.96 and 1.00 respectively for 4-, 5-, 6-ring PAHs).
Compared with other polluted rivers in the world (Table 2), PAHs in SPMs from the Volturno River were much higher than those detected in the Xijiang River and Yellow River, China by Deng et al.[39] and Li et al. [40] respectively, in the Henan Reach of Yellow River (China) by Sun et al. [53], in the Songhua River (China) by Ma et al. [41], in the Yellow River (China) by Zhao et al. [47], in the Gulf of Mexico, Mexico by Adhikari et al. [21] and in the Gulf of Tunis, Tunisia by Mzoughi and Chouba [54], but lower than those found in the Daliao River estuary, China by Guo et al and Zheng et al. [46, 49] respectively and in the Sarno River by Montuori and Triassi [22].
3.3. PAHs concentrations in sediments
The concentrations of total PAHs in sediment samples are illustrated in Table 1. Results range from 434.8 (site 8) to 872.1 (site 1) ng g− 1 with a mean value of 659.1 ± 136.9 ng g− 1. The concentrations detected ranged from 5.29 to 73.7 ng g− 1 with a mean value of 24.1 ± 27.5 ng g− 1 for 2-ring PAHs (Nap), from 42.9 to 186.3 ng g− 1 for 3-ring PAHs (Acy, Ace, Flu, Phe, An), from 61.7 to 199.7 ng g− 1 for 4-ring PAHs (Fl, Pyr, BaA, Chr), from 262.7 to 507.1 ng g− 1 for 5-ring PAHs (BbF, BkF, BaP, DahA) and from 17.5 to 133.2 ng g− 1 for 6-ring PAHs (BghiP, InP). As to the compositional profiles of PAH in sediments at each sampling sites, 4- and 5-ring PAHs were abundant at most sites, accounting for 37% and 40% of ΣPAHs in sediments, respectively. Low molecular weight PAHs were gradually decrease by diluation due to their relatively high water solubility and easier degradation. Therefore, high molecular weight PAHs could easily reach the sediment due to their low vapour pressure, low water solubility and more refractory behavior; thus, they were more resistant to degradation [56, 57, 38].
In comparison with polluted rivers in other parts of the world (Table 2), the concentration of ΣPAHs in the samples of sediment from the Volturno River and its Estuary (434.8-872.1 ng g− 1) was similar to those found in the Yellow River and Yellow Sea, China by Zhao et al. [47] and Li et al. [58] respectively, in the Erjien River, Taiwan by Wang et al. [59], in the Marano and Grado Lagoon and Priolo Bay, Italy by Acquavita et al. [60] and Di Leonardo et al. [61] respectively. The concentration of ΣPAHs in the samples of sediment from the Volturno River and its river mouth was greater than the concentration found in the East China Sea, China by Zhao et al. [62], in the Yellow River and in the Henan Reach of Yellow River, China by Li et al. [40] and Sun et al.[53] respectively, in the Yangtze River Estuary (China) by Liu et al. [63], in the Bohai Bay (China) by Li et al. [57], in the Ibirité Reservoir, Brazil by Mozeto et al. [64], in the Tampa Bay, Florida by Lewis and Russel [65], in the Gulf of Mexico, Mexico by Adhikari et al. [21], in the Danube River, Hungary by Nagy et al. [55] and in Italy, in the Italian Marine Protected Areas by Perra et al. [66], in the Tiber River by Patrolecco et al. [45], Minissi et al. [67] and Montuori et al. [30], and in the Sarno River by Montuori and Triassi [22]. The concentration of ΣPAHs in the samples of sediment from the Volturno River and river mouth was inferior than the concentration found in the Daliao River, China by Guo et al. [46], in the Caspian sea coast, India by Yancheshmeh et al. [68], in the Baffin Bay, Canada by Foster et al. [69], in the Cocó and Ceará Rivers, Brazil by Cavalcante et al. [70], in the Bahia Blanca Estuary, Argentina by Oliva et al. [10], in the Cauca River, Colombia by Sarria-Villa et al. [8], in the Buffalo River Estuary, South Africa by Adeniji et al. [52], in the Ammer River, Germany by Liu et al. [9], in the Portimão Harbor, Portugal by Bebianno et al. [71], in the Gulf of Tunis, Tunisia by Mzoughi and Chouba [54], in Durance River and Huveaune River, France by Kanzari et al. [72, 73] and in the Iberian coast and Ría de Arousa, Spain by Leòn et al. [74] and Perèz-Fernàndez et al. [6] respectively and in the Gulf of Trieste, Italy by Bajt [75]. The low concentrations of PAHs in sediments may be due to the high content of sand and low TOC contents (1.1–9.5 mg g− 1, mean 5.1). Figure 2 showed the relationship between %TOC with the ΣPAHs in the sediment samples. As results showed, a positive linear regression exists between total PAH concentration and TOC data in sediments (r = 0.97, p < 0.01) as indicated by many other studies [46, 53, 8].
3.4. PAHs seasonal and spatial distribution in DP, SPM and sediment samples
The concentrations of total PAHs in DP, SPM and sediment samples of the Volturno River at different sampling sites are illustrated in Table 1. The results show that the ratio of the concentration of ΣPAHs in DP samples to that in SPM was higher than one in all sites (average 2.5; SD ± 1.5). These results lead us to consider that the total amount of PAHs in DP samples was more abundant than in SPM samples for each site and season. These data were also confirmed by the analysis of the ratio of the individual PAHs, and it was possible to observe the same trend obtained from the reports of the sums.
Even the total amount of PAHs in SPM samples was more abundant than in sediment samples for each sampling site. In fact, the ratio of the concentration of ΣPAHs in sediment samples (ng g− 1) to that in the SPM samples (expressed in ng g− 1) was less than 1 in all sampling sites (average 0.014; range 0.006–0.022; SD ± 0.006). In particular, the results indicate that PAHs concentrations in DP were low during the wet season floods (February) and high during the dry season (July). The seasonal variation of PAHs concentrations was depending to the hydrological conditions, which could cause dilution ratio variations. Therefore, a high river flow rate resulted in a higher dilution ratio in the wet season floods caused a decrease in the PAHs concentration in both the Volturno River and its estuary. In July, the concentrations of total PAHs in SPM samples were lowest in all sampling sites. The results could be explained by the flow decrease during the dry season that a greater stagnation of SPM determining the transfer of the more polar PAHs from SPM to DP. Based on these results, it can be concluded that the load and relocate of PAHs between different phases in each sampling site of the Volturno were related to a variation in the flow during rainy and dry seasons. Therefore, high concentration of PAHs in SPMs but moderate in sediment indicated that the contamination of PAHs in Volturno River and Estuary might be caused by fresh input of PAHs.
In order to evaluate the huge input of PAHs drained from storm water runoff, tributary inflow, wastewater treatment plant and industrial effluent discharge, agricultural runoff, atmospheric deposition, dredged material disposal, the total load of PAHs into the Tyrrhenian Sea was calculated. The total PAHs loads contribution to the Tyrrhenian Sea from the Volturno River is calculated in about 3.158,2 kg/year.
The spatial distribution of PAHs in DP, SPM and sediment samples from the Volturno River and its estuary were studied by comparing the concentrations of ΣPAHs in different sampling sites in dry and rainy seasons, respectively (Fig. 3). Indeed, the level of contamination of PAHs in the water clearly decrease from location 1 to 4. The total PAHs concentrations decreased to 1219.8 ng L− 1 (DP + SPM mean values of four seasons) at location 1 (Volturno River Mouth) to 993.8 ng L− 1 (DP + SPM mean values of four seasons) at location 2 (500 m from the Mouth) to 823.0 ng L− 1 (DP + SPM mean values of four seasons) at location 3 (1000 m from the Mouth) and to 668.0 ng L− 1 (DP + SPM mean values of four seasons) at location 4 (1500 m from the Mouth). In the Tyrrhenian Sea, PAHs concentrations range in general from very high in the vicinity of the river outflows to very low in offshore areas (Fig. 3). At 500 m of river outflow, the concentration of PAHs were close to those of the Volturno mouth (Fig. 3). The concentrations at the sampling sites then decreased at 1000mt and more at 1500mt of the river outflows. Particularly, at the Volturno mouth the PAHs loads move into the Tyrrhenian sea southward (Fig. 3). As can be seen from the data obtained, the trend concentrations shows a decreasing movement from the mouth towards 1500mt at sea. This can depend both on the flow of the river which varies according to the season, and on the diluting effect of the sea.
3.5. Source identification
To investigate the origin of PAHs and identify separately petrogenic from pyrolytic inputs, chemical profiling and different diagnostic ratios on isomeric relations were used: An/(An + Phe), Fl/(Fl + Pyr), BaA/(BaA + Chr) and InP/(InP + BghiP) [13, 76]. The first group is from pyrolytic sources, which includes combustion of fossil fuels, vehicles using gasoline or diesel fuel, waste incineration and coke production, carbon black, coal tar pitch, asphalt and petroleum cracking. The second group is from petrogenic sources, which include crude oil and petrochemicals (gasoline, diesel fuel, kerosene and lubricating oil). Finally, apart from pyrolytic or petrogenic source, PAHs can be formed during diagenetic processes, i.e. the formation of sediments from organic material [6]. Each source (i.e. pyrolytic, petrogenic and diagenetic) gives rise to typical PAH patterns. In general, combustion products are dominated by relatively high molecular weight (HMW) compounds with four or more condensed aromatic rings, whereas bi- and tricyclic aromatic compounds (LMW) are more abundant in fossil fuels, which are, moreover, dominated by alkylated derivatives [9, 10, 11].
The ratio study reflected a prevailing pattern of pyrolytic inputs of PAHs in the Volturno River and its estuary. In fact, the results showed that An/(An + Phe) ratio was ˃0.1 in DP, SPM and sediments (mean 0.42, 0.40 and 0.47, respectively), which attributed the origin of PAHs to pyrogenic sources. Furthermore, Fl/(Fl + Pyr) ratios can distinguish petroleum input from combustion processes and discriminate among such sources [13, 77]. For Fl/(Fl + Pyr), low ratios (< 0.40) indicate petroleum, intermediate ratios (0.40–0.50) of liquid fossil fuel combustion, whereas ratios > 0.50 are characteristic of grass, wood, or coal combustion. In the Volturno River and Estuary, ratio Fl/(Fl + Pyr) ˃0.5 was found to water, particulate matter and sediments, indicating a variable impact urban traffic emissions and from biomass burning (Fig. 4a). Ratio BaA/(BaA + Chr) ˃0.35 was found in water and in sediments, which suggests vehicular emissions; and similar behavior it is observed for ratio InP/(InP + BghiP) ˃0.35, which indicates combustion sources (Fig. 4b). Finally, the LMW/HMW ratio was relatively low (< 1 for most sites), suggesting a pyrolytic origin of PAHs at these sites (mean 0.85; range 0.09–2.99).
These results, obtained by different molecular ratios, were correlated with the specific pollution conditions in the Volturno River. The Volturno flatland is a heavy industrial area, with many heavily polluting factories. In additions in the Campania Region has resulted in the widely documented illegal disposal of urban, toxic and industrial wastes. The industrial wastes enriched with combustion-derived PAHs are directly discharged into the Volturno River. Although none of the industries present in the the Volturno River area exceed the legal limits in terms of emissions to the atmosphere or industrial discharges as reported by the Piano Regione Campania, the emission of atmospheric particles from factories, could cause serious air pollution over time, and the particulate-associated PAHs may transport and deposit into the river over time. In addition to these inputs, some other sources such as the roads on both sides of the river and along the coast, the runoff containing street dust, and municipal wastewater, result in the pattern of pyrolytic origins of PAHs contamination in the area. About that, no other rivers in the area adjacent to that of the Volturno River has been considered with regard to the evaluation of the PAHs and for this reason valid comparisons can’t currently be made. However, some rivers have been taken into consideration for the evaluation of the PAHs, even if they are at greater distances from Volturno River [22, 78, 30].
The Volturno flatland is a heavy industrial area, with many heavily polluting factories. In additions in the Campania Region has resulted in the widely documented illegal disposal of urban, toxic and industrial wastes. The industrial wastes enriched with combustion-derived PAHs are directly discharged into the Volturno River. The emission of atmospheric particles from factories, also cause serious air pollution, and the particulate-associated PAHs may transport and deposit into the river. In addition to these inputs, some other sources such as the roads on both sides of the river and along the coast, the runoff containing street dust, and municipal wastewater, result in the pattern of pyrolytic origins of PAHs contamination in the area.
In addition to pyrolytic and petrogenic sources, Per is also produced by in situ degradation of biogenic precursors [12, 76, 6]. Indeed, Per is probably the most important diagenetic PAHs encountered in sedimentary environments and, thus, a high abundance of Per relative to other PAHs can indicate an important natural origin of the compound. Per has been frequently associated with inputs from rivers and estuaries [12, 68, 79]. In fact, it has been suggested that concentrations of Per above 10% of the total penta-aromatic isomers indicate a probable diagenetic input, whereas those in which Per accounts for less than 10% indicate a probable pyrolytic origin of the compound. In the present study, the concentrations of Per detected in all sediment samples were very low (range 4.3–15.5 ng g− 1) and contributed less than 2% to the penta-aromatic isomers, indicating a pyrolytic origin of these compounds.
3.6. A composite indicator for water pollution
In order to formalize a Water Pollution Composite Indicator (WP-CI) we analysis at the same time Dissolved phase (DP) and Suspended Particulate phase (SPM) samples collected from 10 sites (“Sou1”, “500N2”, “1000N3”, “1500N4”, “500C5”, “1000C6”, “1500C7”, “500S8”, “1000S9”, “1500S10”) during the months of April, July, November and February. The correlation matrix points out sets of correlated variables and only the first seven highest eigenvalue are larger than one. However, the first two components explain the 60,0% (32,6% and 27,4%, respectively) of the total variance. The PCA for this dataset pointed out a clear distinction of the pollution of the two phases and allowed us to define two SCIs (Specific Composite Indicator). In fact, the first factor is characterized by the presence of PAHs belonging to SPM and we named it “SPM-Composite Indicator”; the second factor is defined by the PAHs of the DP, the second factor is called “DP - Composite Indicator”. Looking at the plot of the first two principal components, and making a correlation between sites and seasons we observe that the pollution from SPM is higher in February, in the sites 500N2, 1000C6, 1500C7, 1000S9, however DP pollution is higher in July at sites 1500C7 e 1500S10 (Fig. 5a and 5b). For each SCI is possible to rank the 40 statistical units and finally it is possible to observe the final ranking based on the WP-CI (Table 3). The site that has a lower rate of global pollution in all seasons of the year is the 4, followed by 3 and then 7. However, just in reference to site 7 there is an irregular behavior of the two parties. In fact, while in November both SPM and DP appear to have a low level of pollution, in other seasons the two components have contrasting behavior. The most polluted months are February and April especially for the SPM component, on the contrary, the least polluted months are July and November, in particular for the SPM component. The month of February, instead, has a tendency to lower pollution for the DP, on the contrary, July and April are the months most polluted. Based on these results, it can be confirmed that the load and relocate of PAHs between different phases in each sampling site of the Volturno were related to a variation in the flow during rainy and dry seasons.
Table 3
Rankings based on SCIs and WP-CI according to these thresholds, (1): normalized score > 0:60, (2): normalized score > 0:30 and < 0:60, (3): normalized score < 0:30.
3.7. Risk assessment
To evaluate the potential adverse effects caused by PAHs in the Volturno River were used the sediment quality guidelines (SQGs) values developed by [80] and by [81]. Sediment quality guidelines (SQGs) are an important tool for the assessment of contamination in marine and estuarine sediments. Two sets of SQGs, including the ERL/ERM and the TEL/PEL values, were applied in this study to assess the toxic effects of individual PAHs in sediments. These sets are defined as: i) effect range low (ERL)/effect range median (ERM) and ii) the threshold effect level (TEL)/probable effect level (PEL). ERLs and TELs represent chemical concentrations below which the probability of toxicity and other effects are rare. Differently, the ERMs and PELs represent mid-range above which adverse effects would occur frequently. ERLs-ERMs and TELs-PELs represent a possible-effects range, within which negative effects would occasionally occur [61, 82]. In the Volturno River, not all PAHs concentrations in sediment samples were below the TEL and ERL values, but the concentrations were significantly lower than the PEL and ERM values (Table 4).
Table 4
A comparison of the TEL, PEL, ERL and ERM guideline values (µg Kg− 1) for polycyclic aromatic hydrocarbons and data found in the Volturno River, Southern Italy.
| |
PAHs
|
| |
Nap
|
Acy
|
Ace
|
Flu
|
Phe
|
An
|
Fl
|
Pyr
|
BaA
|
Chr
|
BbF
|
BkF
|
BaP
|
DahA
|
BghiP
|
InP
|
∑PAHs
|
|
TELa
|
34.6
|
5.87
|
6.71
|
21.2
|
86.7
|
46.9
|
113
|
153
|
74.8
|
108
|
-
|
-
|
88.8
|
6.22
|
-
|
-
|
1684
|
|
Samples percentage over the TEL
|
30
|
100
|
100
|
30
|
0
|
0
|
0
|
0
|
0
|
0
|
|
|
80
|
100
|
|
|
0
|
|
PELa
|
391
|
128
|
88.9
|
144
|
544
|
245
|
1494
|
1398
|
693
|
846
|
-
|
-
|
763
|
135
|
-
|
-
|
16770
|
|
Samples percentage over the PEL
|
0
|
0
|
0
|
0
|
0
|
0
|
0
|
0
|
0
|
0
|
|
|
0
|
10
|
|
|
0
|
|
ERLb
|
160
|
44
|
16
|
19
|
240
|
85
|
600
|
665
|
261
|
384
|
-
|
-
|
430
|
63.4
|
-
|
-
|
4022
|
|
Samples percentage over the ERL
|
0
|
0
|
70
|
30
|
0
|
0
|
0
|
0
|
0
|
0
|
|
|
0
|
100
|
|
|
0
|
|
ERM b
|
2100
|
640
|
500
|
540
|
1500
|
1100
|
5100
|
2600
|
1600
|
2800
|
-
|
-
|
1600
|
260
|
-
|
-
|
44792
|
|
Samples percentage over the ERM
|
0
|
0
|
0
|
0
|
0
|
0
|
0
|
0
|
0
|
0
|
|
|
0
|
0
|
|
|
0
|
| aMacDonald et al. [81]. |
| bLong et al. [80]. |
In relation to the individual compounds, the mean concentrations of detected PAHs were lower than their respective PEL values, while TEL values were exceeded for Acy, Ace and DahA for all samples, for Nap and Flu in 30%, and for BaP 80%, suggesting that adverse effects might occasionally occur. The concentrations of individual PAHs do not exceed their respective ERM values, but the ERL values exceeded for Flu in 30%, Ace in 70% and DahA for all samples. The results indicated that in certain sites PAHs may have been found and the environmental integrity was at risk of PAHs in the sediments from the Volturno River and Estuary.
Although compliance with EC-EQS (European Commission - Environmental Quality Standards) in surface waters is checked using an annual average of monthly whole water (DP + SPM) concentrations (Directive 2008/105/EC, 2008) [83], our data showed that the mean values of BaP and BkF + BbF concentration in the Volturno River (63.9 and 41.2 ng L− 1, respectively) were higher than the EQS values (50 and 30 ng L− 1, respectively), and mean value of BghiP + InP values (67.4 ng L− 1) was significantly higher than the EQS value of 2 ng L− 1, showing that the environmental integrity of the river watercourse was at risk. Also RQ (Risk Quotient), the ratio between the Measured Environmental Concentration (MEC) and the Predicted No Effect Concentrations (PNECs), has been calculated. OSPAR Commission, the mechanism by which 15 Governments and the EU cooperate to protect the marine environment of the North-East Atlantic, established a list of PNECs for several substances, including PAHs. In particular, in OSPAR Agreement 2014-05, in Table 2, Sect. 5, PNECs values were reported for single PAHs. According to these values, we calculated ratio between single MEC and PNEC for single PAHs. As result, we obtained, both for water (sum of DP + SPM) and sediment, an RQ > 1 for most compounds, confirming that the environmental integrity of the river watercourse was at risk.