481 Carpathian Journal of Earth and Environmental Sciences, August 2020, Vol. 15, No. 2 , p. 481 – 490; Doi:10.26471/ cjees /2020/015/147 ASSESSMENT… [607037]

481 Carpathian Journal of Earth and Environmental Sciences, August 2020, Vol. 15, No. 2 , p. 481 – 490; Doi:10.26471/ cjees /2020/015/147

ASSESSMENT OF ACTUAL WATER QUALITY AND
SEDIMENTOLOGICAL CONDITIONS OF THE CORBU I LAKE,
WESTERN BLACK SEA COAST

Bogdan -Adrian ISPAS
*, Laura TIRON DUȚU, Dumitru GROSU &
Glicherie CARAIVAN
National Research- Development Institute for Marine Geology and Geoecology – GeoEcoMar, 23 -25 Dimitrie Onciul
Street , RO-024053, Bucharest, Romania
Email address es: [anonimizat]*, [anonimizat], [anonimizat],
[anonimizat]

Abstract : Corbu I Lake, analyzed between July 24th and 29th, 2019, had a brackish water that from a physico –
chemical point of view, presented oxygen supersaturation, a high degree of mineralization, a rather alkaline
pH and a subunitary index of water transparency. Also, the w ater of Corbu I Lake corresponded to a moderate
ecological status (III) at the time of taking the surface sampl es, due to the pointlike and local diffuse
anthropogenic influences. From a chemical point of view, the biogenic elements containing nitrogen and
phosphorus, sulphates and detergents, were not conforming with the maximum permitted levels specified by
the O rder No. 161/2006, published in the Official Journal of Romania by the Ministry of Environment and
Water Management . Regarding the eutrophication degree, the indicators of total mineral nitrogen and total
phosphorus corresponded to the eutro- hypertrophic a nd, respectively , hypertrophic stages. T he NT mineral /PT
ratio ranged between 5.72 and 68.53, indicating the more pronounced incidence of eutrophicat ion in this lake,
which also had a high content of organic matter (> 20 mg/l), due to the zonal diffuse sources of pollution. The
ecological status of the studied aquatic environment was from good to weak classes for nitrites, ammonium
and phosphates, moderate for sulphates and weak for detergents. It had a low content of s ilica, as well as
anaerobic fermentation products ( H2S and S2-) that were undetectable and quantitatively insignificant. The
granulometry of the bottom -sediment samples of Corbu I Lake ha s identified muds, with the clay fraction
subordinated to the silt. Due to the accumulated and decomposed biogenic material, black and unctuous muds
with a specific odor were found. The interpretation of the data resulting from the gra in size analysi s highl ighted
the deposition of the sediments by suspensions in calm water with poor circulation, a different and poorly
sorting and an excess of fine clastic material.
Keywords: limnological studies, water quality, physico- chemical parameters, brackish water, eutrophication,
laser diffractometry, bottom -sediments, grain size analysis , Corbu I Lake , western Black Sea coast

1. INTRODUCTION

The southern zone of the Romanian Black Sea
coast is rich in lakes, especially maritime liman s. One
of them, Corbu Lake (Gargalâc), is located in the
southeastern part of the Central Dobrogea P lateau
(Casimcei Plateau), at an altitude of 0.9 m above the
Black Sea level (Gâștescu et al., 2016), with an area
of 5.2 km2 and a reception basin of 64.25 km2
(Romanescu, 2008). The maximum depth is 1.9 m
and the average depth is 1.4 m (Gâștescu & Breier,
1982). Also, Corbu Lake has an elongated circular shape and on its cliffs outcrop loess deposits (on the
southeastern shore ), alluvial -diluvial deposits ( on the
western shore ) and Jurassic limestone, with a slope to
the lake of about 45° (on the northeastern shore )
(Caraivan, 2010).
Genetically, Corbu Lake , like all coastal lakes
of the Black Sea, was formed due to abrasion and
marine accumulation, this processes being caused by
the sea level changes and local ep eirogen ic
movements. In this evolution, three stages may be
distinguished : the valley stage (when the sea level
was 80 m lower than the current one, during

482 Neoeuxin), the g ulf stag e (when the sea level
exceeded 3-5 meters the current level) and the lake
stage (when the conditions for the formation of sandy
belts appeared, most likely, in the Middle of the F irst
Millennium AD) (Romanescu, 2008).
Although located in an arid region , Corbu I
Lake is suppli ed with water by the Corbul and Valea
Vetrei creeks, groundwater with a rich flow, favored
by the lithologica l and tectonic conditions ( break able
rocks, with numerous fractures and fissures),
precipitation and the in flow of marine waters that
penetrate the coastal belt , in certain conditions
(Romanescu, 2008). Also, Corbu Lake communicates
through a channel with Tașaul Lake
(Alexandrov et al., 2007; Alexandrov et al., 2008). The a nthropogenic intervention has largely
influenced, especi ally in recent decades, the
lacustrine environment, in particular, the evolution of
water chemistry. Currently, the lake is used for
irrigation and pisciculture and is divided by a dam
into two sectors : the northern one, called Corbu I
(Little Corbu ) Lake and the southern sector, much
larger, called Corbu I (Big Corbu) Lake (Fig. 1).
During the summer’s expedition of 2019,
Corbu I Lake was analyzed, in terms of water quality
and sedimentology. With the help of a boat, GeoEcoMar researchers moved and took water and
bottom -sediment samples from 14 stations (Fig. 1),
performing in situ measurements and laboratory
analyses.

Figure 1. Location of the Corbu I Lake (A) and the sampling stations (B)

483 2. MATERIALS ȘI METHODS

2.1. Water quality analysis
The water samples were taken at a depth of 0.5
m using a non- metallic water sampler (Niskin bottle
of 5 litre s) and kept under standard conditions. Water
quality parameters were determined by in situ
measurements using the WTW Multiline P4F/SET3
multiparameter (for determinations of pH, salinity,
TDS, TSS, redox potential, conductivity, dissolved
oxygen, temperature ), HACH 2100 P turbidimeter
and HACH DR 500 0 UV -VIS spectrophotometer (for
nitrites, nitrates, phosphates, sulfur, sulfat es, silica,
detergents). A mmonium, total nitrogen, total
phosphorus and TO C analyzes were performed by
NIRD ECOIND from Bucharest.

2.2. Particle size analysis of bed surface
sediments

The sediment samples were taken at the water –
sediment interface (0 -20 cm), using a van Veen
bodengreifer and kept under st andard conditions.
Particle size analysis was performed in the NIRD
GeoEcoMar laboratory, by laser diffractometry,
using the granulometric analyzer “ Mastersizer 2000E
Ver. 5.20”, Malvern. The separa tion of the
granulometric classes (sand, silt, clay) and of the
fractions within each class conforms to the Udden-
Wentworth logarithmic scale (Udden, 1914,
Wentworth, 1922), completed with the det ailing of
three fractions, at interval of 1 Φ, in the clay f ield.
Sediment classification was realized according
to the Shepard diagram (1954). Based on the primary
data, using the Gradistat program (Blott & Pye,
2001), the following statistical parameters were
calculated: Median (Md = D50, Inman, 1952), graphic mean (M
z), standard deviation (σ I, sorting),
asymmetry coefficient (Sk I, skewness) and graphic
sharpness (K G, kurtosis). The last four mentioned
parameters were calculated according t o the original
formulas of Folk & Ward (1957).

3. RESULTS AND DISCUSSION
3.1. Spatial distribution of physico -chemical
and water quality parameters

Corbu I Lake recorded an alkaline trend of pH
values. The maximum values of the water pH were
registered in the CB -14 station (Tab le 1). Salinity
variations disturb the living conditions of bivalves
(Velez et al., 2016, Pokhrel et al., 2019), but Corbu I
Lake showed values of concentration s between 1.3 – 1.4‰. The fact is justified by the separation of Corbu
II Lake , wh ich in turn, is isolated by Tașaul and
Siutghiol L akes, relatively preserving its salinity
(Romanescu, 2008). Gi ven the arid climate of the
region, the sali nity of the lake s hould be high,
following intense evaporation, but the low values
were due to freshwater supply sources, as well as
anthropogenic impact, which di rectly influences the
water chemistry , especially through irrigation
(Romanescu, 2008).
The values of TDS (Total Dis solved Solids)
were in the range 1400 – 1480 mg/l and correspond ed
to oligomixohaline brackish waters (Order No.
161/2006) . TSS (Total Suspended Solids) were
situated between 29 – 112 mg/l, and the turbidit y
recorded values between 20 and 114 NTU (Fig. 2).
The E
h (Redox Potential) values, predominantly
negative, between -108 and 20 mV, show ed a
reducing environment, and the rH (Relative
Humidity) values, between 15.39 and 19.18,
indicate d a slightly aerobic water.

Figur e 2. Turbidity and TSS distribution in the Corbu I
Lake water

The electrical conductivity of water depends on
the quantity of dissolved salts and had values between
2.8 and 2.96 mS /cm, the highest value being recorded
in the CB -13 station.
Dissolved oxygen in wa ter had values between 12.78
mg/l and 17.8 mg/l (Fig. 3) . The concentrations
suggest ed an overs aturation with oxygen, but
corresponded, however, to a good water quality. The
degree of water oxygenation ( Fig. 3), at the
temperature of measuring the oxygen concentration
varied between 87.7% and 215% (coefficient of
variation of 18.25%), corresponding to the first
quality class (saturations between 90% and 110%).
The highest saturation (215%) was recorded in CB –
09 station. The water temperature was between 23.6 –
25.1°C. The highest temperature was recorded in the
CB-07 station. Distribution of the physico -chemical 020406080100120
0 50 100 150TSS (mg/l)
Turbidity (NTU)CB-01
CB-02
CB-03
CB-04
CB-05
CB-06
CB-07
CB-08Sam

484 parameters of Corbu I Lake water are shown in Table
1.

Figure 3. Dissolved oxygen concentrations and the degree
of oxygenation of the Corbu I Lake water
Therefore, Corbu I Lake had brackish water,
presenting oxygen ove rsaturation, a high degree of
mineralization, pH more alkaline than CMA
according to Order N o. 161/2006, a subunit ary water
transparency index (0.2), due to strong winds in the zone (Godeanu & Galațchi, 2007) and corresponded
to a moderate ecological status (III) at the time of
surface sampling, because of punctiform and diffuse
local anthropogenic i nfluences , such as irrigation and
fish farming . The predominance of stenohaline
organisms, which support small variations in water salinity, such as European carp ( Cyprinus carpio ),
Gibel carp ( Carrassius gibelio ), European perch
(Perca fluviati lis), Pinchuck’s goby (Ponticola
cephalargoides ), certified the bra ckish environment
of the lake. The brackish water is considered sweeter than standard seawater and saltier than freshwater,
but continental brackish environments are
compositionally different from the marine brackish
environments (Bright et al., 2018).

Table 1. Physico- chemical parameter s of the Corbu I Lake water
Sample Date Water
depth
(m) pH Salinity
(‰) TDS
(mg/l) TSS
(mg/l) Turbidity
(NTU) Eh (mV)
CB-01
7/24/2019 0.8 9.27 1.3 1410 95 79.4 -6
CB-02 1.0 8.33 1.4 1415 91 74.9 15
CB-03 1.1 9.25 1.3 1410 112 85.6 20
CB-04 1.0 9.30 1.3 1400 76 79.4 -14
CB-05 1.0 9.25 1.3 1410 92 114.0 -23
CB-06 0.8 9.48 1.3 1410 85 111.0 -44
CB-07 0.8 9.26 1.3 1410 90 100.0 -60
CB-08 1.1 9.29 1.3 1420 105 96.2 -26
CB-09 1.0 9.25 1.3 1400 101 104.0 -26
CB-10 1.0 9.31 1.3 1410 112 133.0 -92
CB-11 1.0 9.25 1.3 1420 111 114.0 -90
CB-12 0.5 9.26 1.3 1410 101 112.0 -34
CB-13 7/29/2019 0.5 10.16 1.4 1480 26 20.0 -95
CB-14 0.5 10.33 1.4 1480 29 23.2 -108
Sample Date Water
depth
(m) rH CND
(mS/cm) O2
(mg/l) O2
(%) T (0C) Water
transparency
(m)
CB-01
7/24/2019 0.8 18.33 2.82 13.03 153.5 23.7 0.2
CB-02 1.0 17.17 2.83 12.84 151.4 23.6 0.2
CB-03 1.1 19.18 2.82 14.54 172.6 24.4 0.2
CB-04 1.0 18.11 2.80 16.54 199.2 24.6 0.2
CB-05 1.0 17.71 2.82 15.61 186.4 24.4 0.2
CB-06 0.8 17.44 2.82 15.70 87.7 24.4 0.2
CB-07 0.8 16.45 2.81 14.23 169.5 25.1 0.2
CB-08 1.1 17.68 2.83 15.30 181.0 24.3 0.2
CB-09 1.0 17.60 2.80 17.80 215.0 24.8 0.2
CB-10 1.0 15.44 2.82 17.38 208.0 25.0 0.2
CB-11 1.0 15.39 2.83 15.75 189.0 24.6 0.2
CB-12 0.5 17.34 2.82 12.78 151.1 24.4 0.2
CB-13 7/29/2019 0.5 17.04 2.96 16.00 189.0 24.4 0.2
CB-14 0.5 16.93 2.95 14.52 178.0 24.5 0.2 050100150200250
10 20O2 (%)
O2(mg/l)CB-01
CB-02
CB-03
CB-04
CB-05
CB-06
CB-07
CB-08
CB-09Sam

485 The values of the chemical parameters of the
Corbu I Lake water on sampling stations are
highlighted in Table 2.
Thus, it is observed that biogenic elements
containing nitrogen and phosphorus, sulfates and
detergents, are not in compliance with the maximum
limits allowed by Order No. 161/2006. Regarding the degree of eutrophication, the indicators of total
mineral ni trogen and total phosphorus corresponded
to the eutro -hypertrophic and respectively,
hypertrophic stages. T he N
T mineral /PT ratio was 5.72 –
68.53, pointing the higher incidence of eutrophication
in this lake, which it also ha d a high content of organic
matter (> 20 mg/l), due to diffuse zonal sources of
pollution: industrial and agricultural waste,
groundwater. This process can be amplified during
the rainy periods of the year, because of the flow of
contaminated groundwater (Alexandrov et al., 2008),
which feeds the lake. Nitrogen and phosphorus have
an important role in the lake environment because they promote plant development, representing a
limiting nutrient responsible for eutrophication
(Conley et al., 2009, Barik et al., 2018). This process
also ben efits from the ability of lake sediments to
store phosphorus through a high sedimentation rate and effic ient burial, helping to regulation of
phosphorus concentration in the water column (Leote
& Epping, 2015, K owalczewska -Madura et al., 2017,
Barik et al. , 2018, 2019). Eutrophication is common
in lakes on the west ern coast of the Black Sea,
especially in recent decades, due to anthropogenic
impact. Coastal lakes such as Tașaul (Alexandrov &
Bloesch, 2009), Tăbăcărie (Godeanu & Galațchi,
2007), Costinești I and II (Romanescu, 2008), fluvial
liman s from southwestern Dobrogea (Romanescu et
al., 2010), Danube Delta lakes , including the Razim –
Sinoe lagoon complex (Galațchi & Tudor, 2006, Dinu
et al., 2015, Catianis et al., 2018), lakes from the
lowland and mid- altitude regions of Romania (Kelly
et al., 2019), glacial lakes from Rodn ei Mountains

Table 2. Chemical parameter s of the Corbu I Lake water
Sample Date Water
depth
(m) N-NO 3-
(mg/l) N-NO 2-
(mg/l) N-NH 4+
(mg/l) P-PO 43-
(mg/l) NT
(mg/l) PT
(mg/l) NT
mineral
(mg/l)
CB-01
7/24/2019 0.8 0.09 0.0225 2.1931 0.191 5.25 0.19 2.3056
CB-02 1.0 0.09 0.095 0 2.092 0 0.075 4.87 0.12 2.275 0
CB-03 1.1 0.09 0.0325 1.7265 0.175 4.83 0.23 1.8492
CB-04 1.0 0.18 0.0275 2.0297 0.116 4.69 0.10 2.2372
CB-05 1.0 0.09 0.0300 1.7265 0.100 4.54 0.12 1.8465
CB-06 0.8 0.09 0.0378 1.1821 0.133 4.86 0.15 1.3099
CB-07 0.8 0.06 0.0425 1.9831 0.116 4.95 0.19 2.0856
CB-08 1.1 0.03 0.0200 1.7109 0.216 4.39 0.10 1.7609
CB-09 1.0 0.03 0.0275 2.4186 0.133 4.70 0.08 2.4761
CB-10 1.0 0.09 0.0400 1.5242 0.083 5.06 0.14 1.6542
CB-11 1.0 0.09 0.0475 1.7732 0.108 4.46 0.09 1.9107
CB-12 0.5 0.15 0.1175 1.8509 0.108 4.98 0.20 2.1184
CB-13 7/29/2019 0.5 0.03 0.0200 0.6222 0.708 1.25 0.26 0.6722
CB-14 0.5 0.03 0.015 0 0.8788 0.516 2.78 0.33 0.9238
Sample Date Water
depth
(m) TOC
(mg/l) SO 42-
(mg/l) Detergents
(mg/l) H2S
(mg/l) S2-
(mg/l) SiO 2
(mg/l)
CB-01
7/24/2019 0.8 22.11 197.5 1.73 0 0 1.055 0
CB-02 1.0 22.70 197.5 1.64 0.0138 0.013 0 0.947 0
CB-03 1.1 21.65 182.5 1.62 0.0162 0.0100 1.4775
CB-04 1.0 21.07 135.0 1.96 0.0162 0.0100 1.8075
CB-05 1.0 21.94 172.5 2.29 0.0026 0.0025 1.9725
CB-06 0.8 22.06 172.5 2.07 0.0026 0.0025 2.0425
CB-07 0.8 22.08 190.0 3.02 0.0026 0.0025 2.2175
CB-08 1.1 21.77 165.0 2.00 0 0 1.7800
CB-09 1.0 20.21 227.5 2.40 0.0079 0.0075 1.9700
CB-10 1.0 23.18 175.0 0.57 0 0 1.8525
CB-11 1.0 22.63 182.5 0.54 0.0053 0.005 0 1.5175
CB-12 0.5 21.72 195.0 0.81 0.0026 0.0025 1.3600
CB-13 7/29/2019 0.5 14.28 192.5 0.84 0 0 0.3900
CB-14 0.5 14.27 202.5 0.92 0 0 0.3900

486 (Mare Roșca et al., 2020), lakes from the Bulgarian
Black Sea coast (Kalch evl & Botev, 1999), as well as
regions from the B lack Sea basin (Borysova et al.,
2005, Bănăduc et al., 2016, Poikane et al., 2019) are
affected by eutrophic ation. Globally, the increase of
eutro -phication in the aquatic environment, especially
in recent years, is a threat (Borek, 2018).
The ecological s tatus of the studied aquatic
environment was good to poor for nitrites,
ammonium and phosphates, moderate for sulfates and
poor for detergents. It had a low silica content, as well
as un detectable and quantitatively insignificant
anaerobic fermentation pro ducts (H 2S and S2-).
Fortunately for the water of Corbu I Lake , in
the area it was observed a low concentration of
radioactive elements, such as 137Cs, 40K, 226Ra, 228Ac
isotopes in the sands of Corbu beach (Mursa et al.,
2017), but high concentrations of 129I in c oastal water
of the Black Sea represent a threat (Enăchescu et al.,
2018).
For good ecological status and to have control
over eutrophication and water pollution factors , it is
necessary to develop a management strategy,
involving the evaluation of the relative contributions
of natural variability and anthropogenic impact on
lake flows (Wurtsbaugh et al., 2017), selection of suitable nutrient criteria (Poikane et al., 201 9), as well
as conducting seasonal limnological studies of water
quality (Guo et al., 2020).

3.2. Textur al characteristics of bottom –
sediments

The grain size analyses of th e samples taken
from the bottom -sediments of this maritime liman
revealed the occurence of muds , with a predominant
silt fraction and a subordinated sand content. The
most common textural categor y was the clayey silt,
followed by sandy silt, according to the Shepa rd
classification (1954) . CB-02 sample contained a
percentage of silt higher than 75%. Of the silty
subfractions, the most abundant was the medium
subfraction. The percentage particle size di stribution
is shown in fi gure 4.
Along with the inorganic matter , it was also an
organogenic fraction , consisting of shells, fragments
and plant debris. Due to the accumulated and
deco mposed biogenic material, black and unctuous
muds with a specific odor of the reducing environment were also formed. This phenomenon is
frequently encountered in eutrophic lakes, such as
those from the Danube Delta (R ădan et al., 2016).

Figure 4. Cumulative frequency curves of the Corbu I Lake bottom -sediments0102030405060708090100
1 0.5 0.25 0.125 0.063 0.031 0.016 0.008 0.004 0.002 0.001 <0.001Frequency (%)
Grain size (mm)CB-01
CB-02
CB-03
CB-04
CB-05
CB-06
CB-07
CB-08
CB-09
CB-10
CB-11
CB-12
CB-13
CB-14Samples

487 The presence of oxidation indicates that the
bottom -sediments were recently exposed to the aerial
environment (Lo et al., 2019), but in the case of Corbu
I Lake , the sediments did not show oxidation.
The interpretation of the data resu lting from the
grain size analyses (percentages of clay, silt, sand and
textural parameters, Table 3) highlighted the dynamic conditions in which thes e lacustrine sediments were
deposited.
The median represents the averag e particle
diameter and included values between 5.01 – 6.59 Φ.
The graphic mean recorded close values, between
5.22 – 6.68 Φ, c lassifying the sediments in the
medium and fine silt subclasses . These results
indicate d that the main process that led to the
formation of sediments is the depositi on by
suspensions in calm water with poor circulation
(Shang et al., 2019).
The standard deviation illustrates the sorting
degree of particles and also provides information
about sediment dynamics. In the case of these
samples, the sorting degree of sediments varied in the
range of 1.7 – 2.18 ( poorly and very poorly sorting
domains, according to the correlation between the
inclusive graphic standard deviation and the sorting
degree , proposed by Folk, 1968). Poor ly sorting is a
common feature of the deposited sediments by
suspensions in to quiet aquatic environments, being
determined by the process of particle agglomeration, which prevents the selective deposition.
Asymmetry expresses the difference between
the distribution compared to the normal distribution ,
which is symmetric with respect to its median value and, usually, is an indicator of the deposition (positive
domain) or erosion (negative domain) processes
(Anastasiu & Jipa, 2000). In this study , the
asymmetry had positive values, generally close to 0,
comprised the range of 0.02 – 0.2 and indicate d an
excess of fine clastic material.
Graphic sharpness (k urtosis) was included in
the range of 1.01 – 1.15 (mesokurtic – lepto kurtic
distribution s, according to the variation scale of
graphic sharpness, proposed by Folk, 1968),
suggesting a different sorting.
The dynamic conditions of the lakes are
determined by several factors, such as depth, water
volume, bottom morphology, size of the rece ption
basin, groundwater, climatic condit ions, trophic
status (Telteu & Zaharia, 2012). Given the small area
and volume , the main factors that determine the
entrainment of particles and the sedimentation rate of Corbu I Lake are waves caused by strong winds, the
anthropogenic activities (irrigati on), the flow of
surface waters and groundwater. The sedimentation
rate in lakes is usually higher than in marine
environments (Einsele, 1992).

4. CONCLUSIONS
Corbu Lake is a maritime liman , located on the
western Black Sea coast, connected by a chan nel with
Tașaul Lake . Anthropic intervention has greatly
influenced the lacustrine environment, currently, the
lake is being used for irrigation and fish farming. It is
divided by a dam into two sectors, Corbu I and Corbu
II.

Table 3. Grain size composition and textural parameters of the Corbu I Lake bottom -sediments
Sample Grain size composition Shepard
(1954)
classification Median
(Φ) Graphic
mean
(Φ) Sorting Skewness Kurtosis Sand
(%) Silt
(%) Clay
(%)
CB-01 17.21 70.76 12.03 sandy silt 5.54 5.68 1.96 0.10 1.09
CB-02 5.22 77.95 16.83 silt 6.23 6.36 1.70 0.16 1.06
CB-03 25.99 62.13 11.88 sandy silt 5.01 5.32 2.13 0.20 1.05
CB-04 28.89 60.27 10.84 sandy silt 5.07 5.22 2.18 0.09 1.01
CB-05 6.70 70.86 22.44 clayey silt 6.59 6.68 1.91 0.08 1.11
CB-06 8.99 71.25 19.76 clayey silt 6.37 6.41 1.94 0.05 1.07
CB-07 16.55 66.96 16.49 sandy silt 5.77 5.91 2.13 0.09 1.03
CB-08 8.29 72.13 19.58 clayey silt 6.36 6.45 1.92 0.08 1.12
CB-09 13.80 67.10 19.10 clayey silt 5.98 6.13 2.16 0.08 1.05
CB-10 13.53 71.67 14.80 clayey silt 5.92 5.99 1.96 0.05 1.10
CB-11 9.46 74.70 15.84 clayey silt 6.10 6.18 1.85 0.08 1.15
CB-12 9.00 74.41 16.59 clayey silt 6.13 6.21 1.85 0.10 1.08
CB-13 13.00 67.20 19.80 clayey silt 6.23 6.25 2.09 0.02 1.03
CB-14 9.02 70.67 20.31 clayey silt 6.46 6.48 1.91 0.02 1.08

488 Limnological studies conducted by NIRD
GeoEcoMar in the summer of 2019 on Corbu I Lake
reported a brackish and supersaturated with oxygen
water , a high degree of mineralization, a rather
alkaline pH , and a subunit ary water transparency
index. Due to the pollution, especially the anthropic
one, the water of Corbu I Lake corresponded to a
moderate ecological status (III) at the time of taking
the surface samples.
From a chemical point of view, the nitrogen
and phosphorus content, sulphates and detergents, did
not comply with the maximum limits allowed in the
Order No. 161/2006. T otal mineral nitrogen and total
phosphorus indicators highlight ed the more
pronounced incidence of eutrophicat ion in this lake,
which also had a high content of organic matter.
The noted negative features represent a threat
to the ecological balance. Consequently, it is
necessary to develop a manag ement that involves a
control of eutrophication and water pollution factors,
reducing of anthropogeni c impact on the
environment, as well as systematic monitoring of
water quality.
The bed surface sediments of Corbu I Lake are
made up of muds , with a sand content. The
sedimentation rate is conditioned by the action of
waves caused by strong winds, the anthropogenic
activities (irrigation), the flow of surface waters and
the inflow of groundwater.

Acknowledgements

Financial support of this study was provided by the
Ministry of Research and Innovation (Romania), through
two National Projects carried out by NIRD GeoEcoMar :
“Multidisciplinary research on the effects of anthropogenic
interventions on the Danube Delta and the coastal zone and
possibil ities of re habilitation of the environment” (PN19
20 04 01), and “Research of excellence in river -delta -sea
systems, to highlight regional and global climate changes ”
(Contract no.8PFE/16.10.2018).
The authors also express their gratitude to the NIRD
GeoEc oMar team involved in the sampling of bottom –
sediments.

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Received at: 10 . 08. 2020
Revised at: 2 1. 08. 2020
Accepted for publication at: 25 . 08. 2020
Published online at: 27 . 08. 2020