Journal of Water Resource and Protection, 2013, 5, 458-468
http://dx.doi.org/10.4236/jwarp.2013.54045 Published Online April 2013 (http://www.scirp.org/journal/jwarp)
Chemical and Microbiological Parameters in
Fresh Water and Sediments to Evaluate the
Pollution Risk in the Reno River Watershed
(North Italy)
Chiara Ferronato, Monica Modesto, Ilaria Stefanini, Gilmo Vianello,
Bruno Biavati, Livia Vittori Antisari
Department of Agricultural Science, Alma Mater Studiorum, University of Bologna, Bologna, Italy
Received January 14, 2013; revised February 26, 2013; accepted March 7, 2013
Copyright © 2013 Chiara Ferronato et al. This is an open access article distributed under the Creative Commons Attribution License,
which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
ABSTRACT
The European Water Framework (WFD) establishes a framework for the protection and the monitoring condition of all
natural superficial waters of the member States. The Italian Legislative Decree n. 156/2006 implements the WFD estab-
lishing a monitoring system which foresees a detailed detection of several physical, chemical and microbiological pa-
rameters in order to assess the qualitative status of the water body. This study reports the freshwater quality in the Reno
river basin (North Italy) from 2003 to 2011. The Reno superficial water was classified as “good” in the mountain sta-
tions and at the closed basin while in all the other stations of the Po plain the quality was from “mediocre” to “poor”.
The decrease of water quality was due to the flowing of artificial canals that collect discharges the wastewater of sew-
age treatment plants, drainage and run-off from the urban, industrial and agricultural lands. In spring-summer 2011,
characterized by severe drought, a study on the distribution of pollutants and nutrients in water of the Reno river and its
tributaries highlight the impact of highway (Via Emilia) that closes the mountain basin of water courses. Along this
street cities and industrial and craft have developed, increasing discharges of pollutants and nutrients in rivers. An in-
crease of metals and nutrients was found from upstream to downstream, furthermore the concentration of the microbi-
ological faecal indicators were two to three times higher than those determined in the water upstream of urban/industrial
settlements. The thresholds of Italian Law for Hg and Pb were exceeding in all most rivers. The sediments analysis was
also performed because they can be considered a sink and/or source for pollutants. In many monitoring sites the metals
concentrations was higher than the thresholds of Italia Low (data not shown), but the availability of these metals was
tested with mixtures of different strength extracting (EDTA, DTPA and water). The coefficient of partition solid/water
(Kd) was calculated to evaluate the metals affinity to be in the aqueous phase and it increase as following Cr > Mn > Ni
> Pb > Zn > Cu > Cd.
Keywords: Water Quality; Sediment Quality; Reno River; Italy; Pollutants
1. Introduction
The chemical, physical and biological pollution of sur-
face water is a topic of great attention all over the world.
Rivers play an important role since they collect munici-
pal and industrial wastewaters but also they collect pollu-
tion from agricultural activities. Studies on water con-
tamination have developed over the last 20 years with a
view to monitoring and preventing water pollution. At
international level there are different guideline systems
for monitoring and assessing the quality of aquatic eco-
systems. The European community, in the Water Frame-
work Directive 2000/60/EC (WFD) proposes an analytic
method based on the detection of several physical, che-
mical and biological parameters in order to be summa-
rized in a quality index. The European objective is to
obtain a “good” quality status for all the natural superfi-
cial waters within the Member States by 2015. Chemical
analysis of freshwater can quantify nutrients and pollut-
ants in aquatic environments, but provides no direct in-
dication of the potential toxic effects of these metals on
aquatic biota. The excess nutrients may lead to various
problems including an increase of algal bloom, loss of
C
opyright © 2013 SciRes. JWARP

C. FERRONATO ET AL. 459
oxygen, fish deaths and loss of biodiversity. Agricultural
and urban activities are considered to be major sources of
N and P in aquatic ecosystems [1-4], while metals are
collected in rivers from a variety of sources, either natu-
ral or anthropogenic [5,6]. Pollutants may accumulate in
microorganisms, aquatic flora and fauna and enter the
human food chain. In the aquatic environment there is a
continuous adsorption and desorption process between
water column and bed sediment: studying these dynamics
is the key to understanding the behavior of toxicants in a
lotic system and its biological life. Because of different
physico-chemical processes (e.g. adsorption, hydrolysis,
co-precipitation) only a small portion of free metals are
dissolved in water while a larger amount is deposited in
sediments [7]. The ability of sediments to faithfully re-
cord the “environmental impact” on freshwater ecosys-
tems over time is demonstrated [8-10]. Sediment pro-
vides habitats for benthic organisms, for microbial and
fungal populations, and for all the species which reflect
the quality and health of the ecosystem [11]. Contami-
nants are not necessarily fixed permanently by the sedi-
ments, and under changing environmental conditions
they may be released into the water column by various
processes of remobilization [12]. The marked tendency
for heavy metals towards solid and water phase parti-
tioning and the ability of sediments to integrate long-
term information makes the sediments attractive for as-
sessing the impact of industry and urban development on
the fluvial environment [13,14]. Sediment contamination
is indeed a worldwide problem, especially in industrial-
ized countries, even though the response to this problem
varies in terms of jurisdictions [15]. The Reno river is
one of the most important water bodies of northern Italy
to have affected the hydrographic system and develop-
ment of the Po Valley (North Italy). The current con-
figuration of the Reno basin is due to historical remedia-
tion (from the Roman Age to the early years of the last
century). The protection of the hydraulic system has led
to strong anthropogenic waterways to the detriment of
their naturalness, and also the presence of industrial and
urban settlements has similarly decreased the quality of
the water. The aim of this work was therefore to evaluate
the water quality of the Reno watershed from 2003 to
2008. Besides, to understand the dynamics of water pol-
lution and sediment in the Reno basin, the Via Emilia, a
main road on which the majority of civil and industrial
settlements are located and which is crossed by 104 - 105
vehicles per day [16], was taken as a watershed of human
activities. For this reason the variations of microbiologi-
cal and chemical pollutants in the river Reno and its tri-
butaries were studied up- and downstream of the Via
Emilia during the period spring-summer 2011. In fact, in
this season the rainfall is low and the rivers are fed only
by wastewater from urban and industrial centers.
2. Material and Methods
2.1. Study Area
The basin of the river Reno has a total area of 4930 sq
km. The territorial network composed by the river and its
tributaries is the result of the countless conversions made
since Roman times, in terms of extensive remediation
and hydraulic protection. The reclamation of the plain
has led to a radical change in the river basin where the
surface water, beyond the Via Emilia, flows within arti-
ficial embankments that carry the river water to the Adri-
atic Sea. The mountains of Corno alle Scale (1945 m
a.s.l.) and Monte Orsigna (1555 m a.s.l.) catch the wa-
tershed of the Reno river basin, with elevations varying
from 1500 to 500 m a.s.l., and the territory is formed by a
wide range of major and minor valleys arranged in a
south-western and north-eastern direction. The hills fi-
nally meet the Via Emilia, where many towns and artisan
industries have developed. The geology of the hills is
characterized by gullies and outcrops of gypsum, while
behind them the last stretch of the high-end plain, be-
tween 100 and 50 m a.s.l., consists of fluvial sediment
that has given rise to the formation of cones. The area of
the Via Emilia is characterized by alluvial deposits,
formed by river waters over the centuries. The alluvial
deposits (gravel, sand, silt) are of different sizes and
these have formed cones in the direction of the plain. The
plain itself is characterized by the vertical overlap of se-
dimentary bodies and was formed during the flooding of
many rivers in the course of history.
The Reno river basin lies between the Apennines and
the Adriatic sea, in a northern temperate zone, to the
south-central border of the Po Valley.
Table 1 shows the average rainfall in the mountain ba-
sin of the river Reno. The less rainy months were from
May to August, while those of autumn-winter were cha-
racterized by higher rainfall.
2.2. Water and Sediment Sampling Survey
The water quality of Reno and its tributaries was moni-
tored each month in different stations from 2003 to 2011,
as established by Italian law (Legislative Decree 152/
2006) by Agency of Environmental Protection of Emilia
Romagna Region (ARPA-Emilia Romagna). The moni-
toring stations (Figure 1), starting from the Apennines
(193 m a.s.l.) from upstream to downstream are: Vergato
(VE), Casalecchio di Reno (CR, closure of the mountain
basin—70 m a.s.l.), Pieve di Cento (PC, after the conflu-
ence of the artificial high water canals of the Dosolo and
those of low water, and the stream Samoggia into the
river Reno), Malabergo (MA, after the confluence into
the river Reno of the artificial canal that passes through
Bologna) and Bastia (BA, where the stream Idice and
Sillaro flow into the Reno river). The Reno tributaries

C. FERRONATO ET AL. 460
Table 1. Average rainfall (1997-2010) in the mountain basin of the Reno watershed (data are expressed as mm of rainfall).
River Pluviometric station 1 2 3 4 5 6 7 8
Reno (REN) Porretta (352 m asl) 71 113 158 25 19 92 49 4
Samoggia (SAM) Monte Ombraro (700 m asl) 49 67 117 28 25 110 65 0
Idice (IDI) Loiano (741 m asl) 56 64 83 26 21 150 33 0
Sillaro (SIL) San Clemente (166 m asl) 62 65 96 17 47 108 63 0
Santerno (SAN) Fiorenzuola (476 m asl) 79 96 167 27 18 108 49 0
Figure 1. Map of the Reno river basin and location of the
sampling stations on Reno river and on some of its tribu-
taries.
flowing under the Bologna district (Samoggia (SAM),
Idice (IDI), Sillaro (SIL) and Santerno (SAN)) were mo-
nitored only in one station of the Po plain upstream of the
Via Emilia.
During spring-summer 2011, a new survey was per-
formed. Water and sediment samples were collected from
the stations of the river Reno and its tributaries (Figure 1)
upstream and downstream of the Via Emilia, The sam-
pling stations upstream of the road are situated within the
hilly/mountainous morphology, characterized, as reported
above, by evaporitic formations (Vena del gesso) and
gullies. The downstream stations are characterized by al-
luvial gravel deposits in the western area and more silt-
clay in the eastern area. On the plain human activity in-
creases and industrialization becomes heavier. The lati-
tude and longitude coordinates of the monitoring stations
are shown in Figure 1.
Water samples in 2011 survey were collected in glass
bottles and kept refrigerated until analyzed and microbi-
ological analysis was performed 24 h from the sampling.
Bottles for chemical analysis were washed with diluted
nitric acid to remove trace elements and then flushed
with milli-Q water, while those for microbiological ana-
lysis were sterilized before use. Sediment samples (0 - 10
cm) were collected in sterilized plastic bags and kept
refrigerated at 4˚C until analysis. Microbiological analy-
sis was performed 48 h from sampling, while for chemi-
cal analysis samples were first air dried. In Idice up-
stream station (IDIu) it was not possible to collect any
sample because of the high percentage of gravel in the
bed.
2.3. Chemical and Microbiological Analysis of
Fresh Water Samples
Water samples were processed for the following analysis:
electrical conductivity (EC), temperature and pH were
measured in the field (Hach-Lange probe). The concen-
tration of carbonate ion (3) was performed in labo-
ratory by titration with 0.02 N HCl at the end point of pH
4.4. Dissolved organic C and N (DOC and DON) were
determined by TOC analyzer (TOC-UV series, Shimazu
Instruments) on unfiltered samples.
HCO
23
NO,NO, Cl,SO,PO
The detection limits was 0.5 ppb for both total C and
N. Major and trace elements were determined by Induc-
tive Coupled Plasma-Optical Emission Spettroscopy (ICP-
OES) (Ametek, Spectro) [17].
Anions (32 4 4

  
) were deter-
mined by Integrated Capillary High-Pressure Ionic Chro-
matography (Dionex, ICS 4000 Thermo Scientific).
For microbiological analysis samples were first diluted
(until 1:10000) in Phosphate Buffered Saline (PBS buffer,
BR0014G, Oxoid) and filtered through nitrocellulose
membranes (0.45 m pore size, 47 mm diameter, Sarto-
rious). Filters were placed on solid selective media for
the detection and enumeration of fecal indicators (E. coli,
Enterococcus spp.). Chromcult Coliformen Agar (1.00850,
Merck) was used for Escherichia coli detection after in-

C. FERRONATO ET AL. 461
cubation in aerobic conditions at 44˚C for 24 h. E. coli
typically appears as blue/purple colonies whereas coli-
forms appear as red/rose colonies. Testing for indole pro-
duction and citocrome oxidase activity gave further con-
firmation of the microorganism identity.
Slanetz & Bartley (1.05262, Merck), selective agar Wa
used for Enterococcus spp. detection after incubation in
aerobic conditions for 48 h at 37˚C. Membranes with
red-maroon or pink colonies were then transferred to
plates with Bile Aesculine Azide Agar (100072, Merck)
and incubated for 2 h at 44˚C. Colonies that turned dark
brown to black with a typical dark halo were considered
to be fecal enterococci colonies.
Colonies were enumerated and the results were ex-
pressed in CFU/100mL, according to the following equa-
tion:

CANVsFBVt
where C = n. of colonies confirmed in 100 ml; A = n. of
colonies confirmed; B = n. of colonies to confirm; N = n.
of colonies suspected; T = volume of sample analyzed;
Vs = reference volume (100 ml); F = dilution factor.
2.4. Chemical and Microbiological Analysis of
Sediment Samples
Sediment samples were air-dried and sieved to 2 mm.
Electrical conductivity (EC, Orion) was performed on the
1:2.5 ratio w:v with distilled and on the same ratio pH
was determined by potenziometric pHmeter (pH metro,
Crison). Total carbonate (CaCO3) were quantified by vo-
lumetric method, according to Dietrich-Fruehing. Total C
(TOC) was determined according to Springer and Klee
(1954) methodology [18] while Total Nitrogen (TN) with
Kjeldahl method [19]. The major and trace elements con-
centrations were carried out in aqua regia where 250 mg
of sample, finely ground in agate mortar, ware digested
in microwave oven (Millestone, 1200) with 6 mL HCl
and 2 mL HNO3, suprapure (Carlo Erba), brought to 20
ml with milli-Q water, filtered on Wathmann 42. The so-
lution was detect by ICP-OES. For the available metals
fraction, 2.5 g of sediment sample was extracted in 25 ml
EDTA (ethylenediaminetetraacetic acid buffered to pH
4.65 with ammonium acetate and acetic acid) and 10 g
were extracted in 20 ml DTPA (diethylenetriamine pen-
taacetic acid + TEA buffered to pH 7.3) [20]. The sus-
pensions were shacked for 1 h and, after filtration with
Wathman 42, the solution was detected for Cd, Co, Cr,
Cu, Ni, Pb, Zn by ICP-OES. 10 g of sediment sample
were extracted with distilled water (1:10 w:v) shacked
for 16 h, centrifugated and filtrated with Millipore sys-
tem at 0.45 µm; the solution was analyzed by ICP-OES.
The partitioning coefficient Kd (l/kg, [21]) was calcu-
lated according to the following equation:
K
dCsCw
NH3 PO
where Cs is the pseudo total metal concentration ex-
tracted with acqua regia (mg·kg−1), and Cw is the dis-
solved metal concentration extracted with deionized wa-
ter (mg·kg−1). Results were then expressed as log value.
Spores of Clostridium spp. were detected according to
[22] with slight modifications. Breafly, 15 g of sediment
sample were first placed in 135 ml of sterile Phosphate
Buffered Saline (PBS buffer, BR0014G, Oxoid) plus
Tween 80 (0.1%, V/V) and then stirred for 30 min to
standardize the mixing. A further serial dilution (1:100)
of each samples was heated at 85˚C for 10 min to facili-
tate the sporulation. Each dilution (10−1 and 10−2) was
tested in quintuplicate by seeding 0.5 mL of the suspen-
sion in Sulfite Polymyxin Sulfadiazine Agar (110,235,
Merck) and incubated in anaerobic conditions at 37˚C for
24 ± 1 h. Suspected Clostridium perfrigens black colo-
nies were purified in Tryptone Soya Agar (1.05458,
Merck) and identified by catalase production and bio-
chemical profile (API 20 A, Biomerieux).
3. Results
3.1. Water Quality
The water quality of Reno river from 2003 to 2011 was
classified as “good” in the mountain stations and at the
closed basin (VE and CR, respectively) while in all the
other stations of the plain the quality was “mediocre” and
“poor”. This trend is clearly evident in the box plot con-
structed from the chemical and physical data of the time
series (Figure 2). The deterioration of the water quality
followed the increase in electrical conductivity (EC) and
nutrient load and the first critical point was the PC sta-
tion, after the closure of the basin, where Samoggia
(SAM) river and the network of artificial drainage canals
with a high pollutants load [23] flow into Reno. Similarly,
in Bastia station (BA) high pollutants load were found
after confluence of Sillaro (SIL), Idice (IDI) and artificial
canals (Canale Navile and Savena Abbandonato) which
cross the Bologna city and collect its municipal and in-
dustrial wastewater. The nutrients concentration were
high with an average amount of 4 and 4

of 6
and 3 mg·L−1 respectively, showing an endpoint of 12 mg
4
1
NH L31 PO L and 7 mg 4


 (data not shown, authors’
communication). The percentage of dissolved oxygen
decreases to 4% - 5% so that the quality of water in Reno
was compromised. From station PC to BA Reno river
was able to self-purify by pollutants, decreasing their
concentrations at the Malabergo (MA) station as shown
in Figure 2.
The self-purification capacity of Reno was compro-
mised by the poor water quality of its tributaries than that
of the artificial canals network (Table 2). The water qua-
lity of tributaries was classified “poor” every years ac-
cording to Italian Law (D. lgs 152/2006). The values of
EC in the water of the tributaries increase as follows:

C. FERRONATO ET AL. 462
Figure 2. Boxplot of the historical trend in Reno river and its tridutaries. Data present mean, maximum and minimum value
of some fundamnental parameters on water.
Table 2. Average, maximum and minimum concentration of water quality parameters of the Reno tributaries (rivers Samog-
gia, Idice, Sillaro and Santerno). Suspended solids (SS), total nitrogen (TN), ammonium



4
NH , nitrate


3
NO , nitrite
(NO2), dissolved oxygen (DO), biochemical and chemical oxygen demand (BOD5 and CO5, respectively), total phosphorus
(TP), orthophosphate (ORT-P), chloride and sulphate (Cl and

2
4
SO) are expressed as mg·L−1, Electrical conductivity (EC)
as µS·cm−1. Data of microbiological parameters are expressed as log Escherichia coli (log ES) and Enterococci (log EN).
Samoggia (SAM) Idice (IDI) Sillaro (SIL) Santerno (SAN)
Mean Max Min Mean Max Min Mean Max Min Mean Max Min
SS 147.9 2290.0 6.4 125.8 1362.0 7.0 1170.3 64632.0 31.0 50.0 460.0 4.0
CE 898.1 1305.0 570.0 805.5 1878.0 531.0 1120.8 1930.0 338.0 670.6 963.0 350.0
pH 8.1 8.7 7.3 8.2 8.8 7.8 8.2 8.6 7.3 8.2 8.7 6.9
TN 5.2 12.5 1.6 4.0 8.2 1.3 6.2 13.5 2.5 2.5 6.7 1.3

4
NH
2
4
SO
0.8 3.7 0.0 0.3 1.3 0.0 0.4 3.1 0.0 0.6 5.8 0.0
NO3 3.0 10.0 0.2 2.4 6.7 0.0 4.1 8.7 0.3 1.5 5.0 0.2
NO2 0.1 0.5 0.0 0.1 1.9 0.0 0.1 1.0 0.0 0.1 0.8 0.0
DO 7.1 15.9 2.2 8.2 13.0 2.3 7.6 13.0 2.0 7.1 18.4 1.7
O2 66.3 120.0 23.0 81.4 134.0 27.0 72.1 142.0 23.0 63.6 143.0 10.0
BOD5 6.2 32.0 2.0 4.0 12.0 2.0 2.7 11.0 2.0 3.4 13.5 2.0
COD5 22.2 70.6 6.0 18.1 54.0 8.0 14.5 87.0 4.0 15.6 77.0 5.0
ORT-P 0.2 0.7 0.0 0.1 0.4 0.0 0.0 0.3 0.0 0.1 0.6 0.0
PT 0.4 1.0 0.1 0.3 0.9 0.0 0.3 1.9 0.1 0.2 1.0 0.0
Cl 56.6 152.0 18.0 52.1 216.0 2.6 94.3 429.0 12.0 26.9 62.0 10.0
130.3 243.0 64.5 138.8 303.0 9.6 230.1 533.0 20.6 123.7 306.0 48.0
Log ES 3.9 5.0 0.0 4.0 5.3 0.0 3.7 5.1 0.0 4.5 5.7 0.0
Log EN 3.5 4.5 0.0 3.6 4.9 0.0 3.8 5.5 0.0 4.0 5.1 0.0

C. FERRONATO ET AL. 463
SIL SAMISI SAN
?
NO
while the highest nutrient load
was detected in water of SIL and SAM streams.
The dissolved oxygen varied from an average per-
centage of 90 in SAN to 66 to 75% for the other tribu-
taries. BOD5 and COD in SAM water were two and
three times higher than the other fresh waters while high
amount of chlorides and sulfates was detected in SIL
stream. The water quality of both Reno and its tributaries
was compromised by a high number of colonies of pa-
thogen microorganisms. In particular the maximum num-
ber of colonies of both Escherichia coli and Enterococ-
cus spp. in Reno was of 15,000 and 10,000 CFU 100
mL−1 in the VE and CR stations, respectively, increasing
to 68,000 and 63,000 CFU 100 mL−1 in the stations on
the plain (e.g. PC and BA). The presence of E. coli colo-
nies varies as follows: IDI (220,000 CFU 100 mL−1) >
SIL (127,000 CFU 100 mL−1) SAM (11,800 CFU
100 mL−1) > SAN (8000 CFU 100 mL−1), while the av-
erage of the Enterococcus spp. colonies are 300,000 CFU
100 mL−1 in SIL and 73,000 CFU 100 mL−1 in IDI; lower
values are found for SAM and SAN (7.800 and 600 CFU
100 mL−1 respectively). The percentage of Salmonella
spp. in the Reno water ranges from 21 to 31% of positive
cases of pathogen presence, while in the tributaries it is
as follows: SIL 20%, IDI 28%, SAM 31% and SAN
37%.
The results obtained by Spring-Summer 2011 survey
were showed in Table 3. High amount of major anion
(e.g. 3

, Cl−, 4
2
SO

and 3), nutrient load (dis-
solved organic C, N, S and ) and pathogen micro-
HCO
3
4
PO 

3
HCO 
3
NO 
2
NO 2
4
SO
Table 3. Mean concentration of chemical-physical and microbiological elements in up- and downstream stations. Chemical
parameters are expressed as mg·L−1, CE is expressed as µS·cm−1 and microbiological parameters are expressed as CFU 100
mL−1.
Upstream stations Cl− TDSpHCEFC E. coliEN DOM DON DOS

3
4
PO
IDI u Mean 112.9 2.190.12 28.73 54.413398.2644246 598 242 2.64 0.58 4.02 0.44
Max 137.2 3.690.44 47.85 60.334378.483011002000 540 3.93 0.73 11.491.04
Min 91.8 1.040.01 13.14 42.141927.936510 130 76 1.73 0.33 0.10 0.01
REN u Mean 71.7 0.980.02 15.41 17.061688.131944 512 69 2.22 1.40 2.55 0.04
Max 76.3 2.080.03 25.15 29.562428.5460100 2000110 2.79 2.65 5.82 0.07
Min 68.6 0.220.01 8.47 7.56 1237.72340 60 20 1.82 0.50 0.10 0.01
SAM u Mean 106.9 6.550.03 33.66 51.503928.17451566452 452 2.22 0.76 8.45 0.04
Max 127.8 14.130.06 42.71 63.916558.212457000 700 12702.83 1.05 32.090.08
Min 87.2 1.280.01 24.11 45.182417.845880 90 112 1.53 0.38 0.10 0.01
SAN u Mean 107.0 1.040.01 65.31 38.203348.063435 72 30 3.29 0.96 15.640.04
Max 156.8 2.780.03 145.34 54.905378.4102090 200 80 4.39 1.22 41.400.07
Min 75.4 0.010.00 11.36 22.962257.34290 3 11 2.74 0.67 5.29 0.01
SIL u Mean 96.7 1.820.12 29.79 81.524558.0865107 113 72 3.14 0.83 33.250.04
Max 108.9 4.460.54 53.18 117.298558.51625400 200 103 5.00 1.27 107.350.05
Min 76.9 0.010.00 14.14 17.281837.634712 21 11 2.22 0.30 0.10 0.02
Downstream stations
IDI d Mean 117.5 4.830.17 42.36 62.073758.0713314 1471739 3.14 2.58 6.95 0.19
Max 151.4 7.140.38 86.18 66.834848.19201400700033005.27 6.04 22.010.43
Min 93.6 3.670.03 20.15 56.521847.93490 0 45 2.43 0.64 0.10 0.04
REN d Mean 77.0 3.990.04 28.50 34.562278.0431563 721 594 3.86 1.64 2.25 0.05
Max 112.5 16.510.06 38.53 67.832958.45612200220020005.63 2.91 7.41 0.09
Min 61.5 0.470.00 21.72 22.101327.425020 7 0 2.04 0.57 0.10 0.02
SAM d Mean 136.2 5.510.05 47.58 49.564218.18012780 2931525 2.90 1.10 25.000.24
Max 178.8 13.490.18 67.21 75.775378.4102013,00013,00020005.04 1.70 104.560.45
Min 86.3 0.170.00 13.57 15.972367.744920 176 80 1.26 0.27 0.10 0.10
SAN d Mean 109.3 3.890.06 73.83 51.114108.07801064 1280199 3.90 1.75 9.30 0.25
Max 150.2 5.190.19 143.82 69.996508.5123550005000 660 5.08 2.04 15.730.54
Min 69.6 2.240.00 16.22 24.032207.541840 48 14 2.81 1.19 0.10 0.01
SIL d Mean 135.7 22.210.17 112.65 111.576578.11250172012,7723272 3.78 3.12 9.71 0.27
Max 196.9 34.460.44 260.04 138.239728.41848600041,00012,800 4.90 5.00 48.130.47
Min 77.0 6.660.00 20.76 95.204047.876840 220 60 3.22 1.06 0.10 0.08

C. FERRONATO ET AL. 464
organisms (fecal coliforms, E. coli, Enterococcus spp.) as
well as metals concentrations (Table 4) was clearly de-
tected in downstream stations. The concentration of the
microbiological fecal indicators was two to three times
higher than those determined in the water upstream of
urban/industrial settlements. The Reno river had the nu-
trients load lower than the other rivers while SIL had the
higher load. In these two rivers Hg concentration higher
than threshold of Italian law (1 μg·L−1), compromising
their water quality which were classified “poor”. In all
samples the Pb concentration in fresh waters were higher
than legal threshold (10 μg·L−1).
3.2. Sediment Quality
The sediments of IDI, SAM and SAN had higher percen-
tages of skeleton upstream than the plain stations, while
these of REN and SIL had an homogeneous fine texture
(Table 5). Total organic C (TOC) and total N (TN) range
from 0.4 to 2.4 g·kg−1 and from 0.1 to 1.4 g·kg−1, respec-
tively, whereby the C/N ratio was low (8 - 12), except for
Reno (32 and 22). pH values range from 8.1 to 9.3 and
the highest values are found in SAN and SAM down-
stream stations. The fecal contamination in sediments has
been estimated by the content of Clostridium spp. spores
Table 4. Mean, minimum and maximum value of trace elements concentration on water in up and downstream stations. Data
are expressed in μg·L−1.
Idice (IDI) Reno (REN) Samoggia (SAM) Santerno (SAN) Sillaro (SIL)
Mean Max Min Mean Max MinMeanMax MinMeanMax Min Mean Max Min
Upstream stations
Al 4.9 14.9 0.3 84.5 285.0 1.4 4.9 14.2 0.3 11.9 23.2 0.3 30.2 87.8 0.3
As 3.0 7.9 0.1 1.7 5.0 0.1 1.4 6.6 0.1 3.0 9.6 0.1 2.1 5.2 0.1
B 175.3 237.0 87.5 66.7 130.0 41.4 225.0305.0142.0260.9462.062.4 371.6 634.0175.0
Ba 53.7 84.5 23.4 43.9 68.2 19.533.1 47.7 16.3 56.8 89.0 25.9 48.2 92.3 14.5
Cu 6.4 16.3 1.0 4.7 9.1 1.0 5.0 9.2 1.0 4.6 8.9 1.0 4.5 9.1 1.0
Fe 15.7 32.3 2.2 15.4 34.8 4.0 7.7 20.0 1.3 24.0 53.8 3.6 21.0 51.5 2.3
Hg 1.0 1.6 0.5 1.1 3.5 0.0 1.0 1.7 0.0 0.4 0.7 0.0 4.6 17.2 0.4
Li 38.9 51.2 20.0 11.1 21.6 6.4 42.3 53.4 28.127.5 40.3 11.8 70.0 108.034.1
Mn 10.8 33.2 1.3 6.2 13.4 1.7 2.3 4.8 0.6 8.8 25.1 2.0 4.2 6.8 1.3
Ni 2.2 3.6 0.0 1.4 2.6 0.0 1.7 2.8 0.0 2.1 4.1 0.0 2.4 3.2 1.6
Pb 50.5 122.0 5.8 33.2 74.2 4.5 31.4 84.8 7.1 46.7 122.05.6 42.8 97.3 2.4
Se 5.5 12.4 1.6 3.3 6.5 1.6 3.0 9.1 1.3 4.6 11.8 1.6 5.3 9.3 1.6
Sr 780.2 1089.0 435.0 333.0 573.0 248.0 727.6874.0504.0 747.81067.0398.0 977.0 1349.0560.0
Zn 28.2 68.3 3.7 11.9 27.8 0.1 15.5 43.9 0.1 95.5 441.03.3 12.7 23.4 2.3
Downstream stations
Al 5.5 13.9 0.3 39.7 80.9 8.6 6.9 17.5 0.3 15.1 34.3 2.5 6.5 17.8 0.3
As 3.5 8.9 0.1 3.1 6.1 0.1 5.8 11.0 0.1 4.5 10.4 0.1 4.2 12.5 0.1
B 167.4 201.0 101.0 84.4 129.0 47.9279.4340.0199.0153.0204.066.2 319.6 393.0206.0
Ba 51.5 75.2 17.5 53.5 86.5 25.759.0 89.1 25.6 56.6 98.0 18.9 58.4 86.1 22.4
Cu 7.9 15.7 1.0 4.1 6.4 1.0 4.2 8.2 1.0 6.2 14.5 1.0 4.7 8.6 1.0
Fe 31.6 58.8 2.4 28.6 47.4 7.5 20.3 32.4 5.5 30.6 52.7 4.8 12.9 25.7 3.0
Hg 0.9 1.3 0.4 1.0 2.5 0.3 0.9 1.5 0.5 0.4 0.5 0.0 2.0 6.3 0.6
Li 40.8 46.9 28.8 14.5 21.9 7.9 45.1 50.5 39.0 19.0 27.4 11.1 67.1 84.1 43.0
Mn 40.9 152.0 4.3 8.5 16.7 1.3 141.6412.07.4 25.7 57.1 1.3 111.7 254.016.1
Ni 4.4 6.8 2.1 1.7 2.8 0.0 5.4 7.6 2.9 2.6 4.4 0.0 4.6 8.8 1.7
Pb 49.4 112.0 7.5 39.4 88.2 6.2 75.7 150.011.650.2 112.09.0 70.5 173.00.0
Se 5.0 11.0 1.6 4.5 7.7 1.6 7.1 13.7 1.6 4.7 8.8 1.6 6.7 16.0 1.6
Sr 851.4 1074.0 579.0 430.0 657.0 295.0 897.21135.0640.0596.4889.0349.0 1075.6 1384.0694.0
Zn 18.6 30.9 3.3 12.7 19.0 3.3 17.5 24.0 8.3 18.8 51.9 0.1 11.6 17.5 0.1

C. FERRONATO ET AL. 465
Table 5. Sediment characterization by Skeleton (Sk) and fine earth percentage and some macro descriptors. EC is expressed
as µS·cm−1, CaCO3 and Total Organic Carbon (TOC) are expressed as percentage value. Total Nitrogen (TN), Total Phos-
phorous (TP) and Total Sulfur (TS) are expressed as mg·kg−1. Clostridium spp. (Clos) are expressed as CFU·g−1.
Sk Fine earth pH EC CaCO3 TOC TN TP TS Clos
IDI d 81.3 18.7 8.99 175 18.4 0.4 0.5 413 708 400
REN u 1.6 95.4 8.16 379 25.5 2.4 0.6 433 969 8000
REN d 5.8 94.2 9.22 140 20.5 0.6 0.3 216 362 700
SAM u 95.2 4.8 8.84 259 37.2 0.5 0.4 278 1382 800
SAM d 0.4 99.6 9.32 113 17.3 1.5 1.4 350 612 400
SAN u 59.5 40.5 8.54 334 31.3 0.3 0.3 334 629 1800
SAN d 4.3 95.6 9.32 113 17.3 1.5 1.4 764 910 400
SIL u 0 100 9.04 142 12.9 0.7 0.8 343 664 560
SIL d 4.1 95.9 8.1 539 20.1 0.1 0.1 343 1152 5000
which were higher in upstream Reno and SAN than the
other river, an increasing trend was found in SIL. The co-
efficient of correlation (data not shown) showed that en-
richment of Clostridium spores were influenced by in-
crease of EC and total organic C and S and by decrease
of pH value.
The metals concentration in sediments increased from
upstream to downstream and in SAN they exceeded the
threshold value for Pb and Sn (100 and 1 mg·kg−1, re-
spectively) (Table 6). The percentage of available metals
on total aqua regia determination decreased as a function
of extracting solutions (Figure 3). As expected EDTA, an
acid chelate agent (pH 4.65), extracted a greater amount
than DTPA (pH 7.3), while deionized water was the
weakest extract agent. The mobility of metals in the
aquatic system was usually studied by the partitioning
coefficient (Kd) from liquid phase and sediments. The lo-
garithmic values of this coefficient ranged from 1.9 for
Cd to 4.3 for Cr whereby the Kd decreased as follows:
. Cr MnNi Pb Zn Cu Cd
4. Discussions
The water quality of the Reno basin is strongly influ-
enced by human impact related to the very high density
of inhabitants. When Reno river flows in the plain its bed
is hanging and its river banks manifest a reduced biodi-
versity vegetation [23]; despite this, Reno river is able to
implement processes of self-purification. The type of
land cover can influence the water quality, which can im-
prove greatly in forest areas [24] compared to agricul-
tural land, where pollution is widespread. The riparian
vegetation of Reno is able to decrease the pollutants and
nutrients load between PC and BA stations, when no
natural tributaries or artificial canals flow into its water,
despite that the land-use of the plain is prevalently agri-
cultural.
The Spring-Summer 2011 survey highlights how the
settlements of the Via Emilia are the main cause of pol-
lution due to an increase of nutrients load, pathogens and
contaminants [25]. The high concentrations of N and P
downstream are due to urban wastewater discharge [7]
rather than runoff from agricultural land [25]. In this re-
cent years, a severe doughty in Spring and Summer time
is characterized by low rainfall and increasing of the
evaporation process, while the minimum vital outflow of
rivers decreases and consequently the concentrations of
pollutants increase. Indeed, under this latter condition the
increase in EC was correlated to an increase in the nutri-
ent load [26]. In this season only episodic storms that
increase the soil losses due to soil erosion were observed,
that fail to dilute the content of water pollutants. Tem-
perature and rainfall can affect the some microorganisms
growth and permanence such as E. coli and Enterococcus
spp. [27,28]. The increase of pollutants load (e.g. Pb and
Zn) in water can be expected with the reduction of flow,
whereby the decrease of pathogens concentration can be
due to high concentrations of metals (e.g. Hg and Pb)
discharges in rivers. The enrichment of metals and nutri-
ents concentrations in sediments, especially in those with
the fine texture, highlights that the adsorption process is
the prevailing self-purification mechanism [29]. As well
as the sediments represent a memory of aquatic ecosys-
tem [30], their role of sink of pollutants and nutrients is
correlated to fine size (silt and clay) and iron and man-
ganese oxides. The Clostridium spores in sediments in-
dicate a fecal contamination [22] and their growth de-
pends on the S and C content because they are sulphur
reductive bacteria involving in the sulphur-compound de-
molition in anoxic environment [31].
The high concentration of metals in sediments can
compromise the life of the aquatic ecosystem [11], but
the pollution risk from metals depends on their chemical
speciation rather their total elemental contents [32]. The
extraction with EDTA and DTPA solutions reveals a dif-
ferent percentage of availability of the metals in sedi-
ments and the high amount extracted by EDTA is due to

C. FERRONATO ET AL. 466
Table 6. Total trace element concentration in sediment. Data are expressed in mg·kg−1 on dry weight.
As B Ba Cd Co Cr Cu Mn Ni Pb Sb Sn V Zn
RE u 2.9 38 139 0.2 24 73 36 782 47 41 1.2 0.7 42 74
RE d 2.0 12 96 0.1 10 81 13 674 30 84 1.4 0.4 17 36
SAM u 3.0 35 207 0.1 20 54 26 1472 26 84 1.1 0.4 34 57
SAM d 4.0 36 191 0.1 23 102 27 817 47 41 1.5 0.7 43 62
SAN u 5.2 13 80 0.1 15 71 14 852 27 94 1.1 0.4 26 43
SAN d 4.3 48 300 0.2 32 111 31 847 38 171 4.7 2.0 40 108
SILL u 3.6 116 202 0.1 34 84 50 546 50 78 1.1 0.7 84 95
SILL d 4.2 36 275 0.1 22 45 30 905 35 98 1.1 0.2 36 71
Figure 3. Mean, min and max value of some metal avail-
ability among EDTA, DTPA and water. Data are expressed
as percentage on the total fraction determined by aqua
regia.
the acid pH [33,34], while the DTPA with neutral pH
does not extract the metals immobilized in sediments
[34,35]. High percentage of Pb and Cu are extracted by
both solutions highlighting a greater pollution risk than
the other metals which are poorly extractable. The same
trends are found by the water-sediment partitioning coef-
ficient (Kd) [21], in which relatively low values of log
Kd of Cd (1.85), Cu (2.07), Pb (2.76) and Zn (2.35) sug-
gesting that these metals are less likely associated with
sediments and more free for transportation and mobiliza-
tion in water, Kd higher than 2.8 suggesting a low geo-
chemical mobility in water.
5. Conclusion
The mediocre and poor water quality determined in the
Reno watershed is due to the anthropogenic impact due
to the municipal and industrial waters discharged into
fresh water rivers. The nutrient and pollutant loads affect
the self-purification capacity of the Reno river. Adsorp-
tion of pollutants in sediments seems be the main self-
purification mechanism while the low pathogenic con-
tamination is related to severe drought during the spring-
summer period that, lowering the river flow, will in-
crease the concentration of pollutants in water.
The study of the release of pollutants in sediment-
water interface is therefore a very important goal to in-
crease the self-purification capacity. Sediment is the sink
of nutrients and pollutants and their hazard can be evalu-
ated by metals speciation and by their availability. The
partition coefficient (Kd) of metals from water to sedi-
ment seems to be a good source of information about
pollution risks. Therefore, the impact of anthropogenic
activities on the fluvial ecosystems should be studied tak-
ing into account the water-sediment interface.
6. Acknowledgements
This research was partially funded by the “Consorzio
della Bonifica Renana” of Emilia Romagna Region.
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