Assessment of Physico-Chemical Parameters and Heavy
Metal Concentrations in Three Estuarine Waters Along the Ratnagiri Coast,
Maharashtra, India
1Amol R. Pund* and 1Anil
R. Kurhe
1Padmashri Vikhe Patil
College of Arts, Science and Commerce,
Pravaranagar, A/P. Loni
E-mail
id. pundamol93@gmail.com, anil.kurhe@gmail.com
ABSTRACT
As critical
transitional zones between terrestrial and marine environments, estuarine
ecosystems provide unique biodiversity and indispensable ecosystem services.
These sensitive habitats are constantly threatened by human activities such as
pollution and land-use change. This study was carried out to investigate the
variations in some physicochemical parameters and heavy metal concentration
levels in three coastal estuaries along the Ratnagiri coast. Water samples were
collected from Bhatye, Kalbadevi and Sakhartar estuaries during monsoon (2022),
winter (2022), and summer (2023). Air temperature ranged from 24.8°C to 33.5°C,
water temperature varied between 24.2°C and 31.1°C - both showing distinct
seasonal patterns. The pH values were in the range of 7.0 to 8.3 and the
salinity values between 12.8-33.2 ppt, which reflected the freshwater-marine
gradient influenced by monsoonal dynamics. The dissolved oxygen content of
water was in the range 4.5 to 7.4 mg/L with higher values during monsoon due to
increased turbulence and freshwater inflow. The heavy metals in water were Lead
(1.39-3.90 μg/L), Cadmium (0.110-0.341 μg/L), Chromium (2.56-7.98 μg/L), Nickel
(1.92-5.10 μg/L) and Zinc (6.21-15.36 μg/L), all within WHO permissible limits
but with areas of localized increase at Kalbadevi estuary near industrial
discharge points. In space, the pattern of pollutions is reflected with
Sakhartar estuary still enjoying almost pristine conditions; Bhatye shows some
(but not serious) contamination; while Kalbadevi estuary clearly suffered from
man's activities. These results furnish baseline data essential for long-term
observation and sustainable development of the marine environment in Ratnagiri
region.
Keywords: Ratnagiri coast,
dissolved oxygen, physicochemical parameters, heavy metals, and seasonal
variation.
1. INTRODUCTION
Estuarine ecosystems are
characterized by unique hydrological, chemical, and biological features
(Pritchard, 1967; 2004). These transitional zones are extremely productive
biologically, act as breeding and nursery grounds for commercially important
fish and shellfish, and perform essential ecological services such as nutrient
recycling, sediment trapping and pollution filtration (Day et al). In India's
Maharashtra state, Ratnagiri's lush Konkan coastline harbors a number brief.
lasting river systems that are of high ecological value and has. The
physico-chemical parameters of estuarine water are fundamental measures of
ecosystem health and water quality (Chapman & Wang, 2001). Temperature
controls the metabolic rates of aquatic organisms and the solubility of
dissolved oxygen, while pH and salinity are critical determinants of species
distribution and biological productivity. Dissolved oxygen (DO) is essential
for aerobic respiration, and it provides an important yardstick of water
quality (Wetzel, 2001). The discharge of heavy metals from industrial,
agricultural and urban sources has become a major global concern in recent
years in estuarine systems (Rainbow, 1995; Zhang et al.). Metals such as lead
(Pb), cadmium (Cd), chromium (Cr), nickel (Ni) and zinc (Zn) have high
toxicity, are bioavailable, and persist in the aquatic ecosystem (Förstner
& Wittmann, 2012).
Development for the
Ratnagiri coast has taken place mainly in three sectors: urban expansion,
development of ports and industrial estates (Zingde et al., 1999; Achary et
al., 2015). The three estuaries of this study represent varying degrees
anthropogenic impact. Bhatye Estuary, a moderate site near human activities
serves as the control threshold; Kalbadevi Estuary is located near sources of
heavy metal pollution, such as industrial zones; Sakhartar Estuary, meanwhile,
is virgin territory.The current investigation seeks to: (1) assess air and
water temperatures, pH, salinity concentrations in estuarine water both
spatially and temporally; (2) determine the levels of heavy metals in estuarine
waters (Pb, Cd, Cr, Ni, Zn); 3) evaluate the situation relative to national and
international standards regarding water quality; and (4) investigate sources of
potential environmental pollution through metal contamination. This research is
core data for any extensive monitoring program lasting decades or centuries in
the Ratangiri area.
2. MATERIALS AND METHODS
2.1 Study Area
The geographic
setting of the study is the Ratnagiri coast along 16°59--17°30' North latitude
and 73°10--73°30' East longitude in India's Maharashtra state. Three sampling
stations were chosen according to their strategic positions and varying
estuarine characteristics: Bhatye estuary, where there is only moderate human
influence; Kalbadevi estuary near an industrial belt with higher pollution
levels due to the proximity of surrounding industries; and Sakhartar estuary
now relatively unaffected by human activity as its former industry-first policy
has been reversed completely. The climate is typical for a tropical zone with
three distinct seasons: the monsoon period (June to September); winter-post monsoon
(October - February); and pre-summer (March - May). Precipitation falls most
heavily during this time, an annual total of between 3000-4000mm occurring
mainly from the southwest monsoon wind.
2.2
Sample Collection
In 2022 water
samples are taken at three different points in time: monsoon season (June to
September 2022), winter season (November 2022 - Mid January 2023) and summer
months of 2023 late spring period (March-May 2003). Samples were taken during
high tide to reduce differences among sites. Surface water samples (> 0.5m
depth) can be collected in pre-cleaned polyethylene bottles according to the
standard method of procedure (APHA, 2017). But mineral maxi scope testing should
not take place immediately so as not to bring water from one place to another
and wash out all of its mineral contents before examination can take place.
Acid-washed (10% HNO3) polyethylene bottles are used to collect all samples in.
For heavy metal analysis, the pH of the HNO3 was always less than 2 when it
went off in containers back at sea. Uptake tubes as well as the lead container
were accompanied by two sample blanks filled with deionized water. All samples
were taken to the laboratory in ice cooled containers and processed within 6 h
of collection.
2.3
Physico-Chemical Analysis
We measured air
temperature with a mercury thermometer (accuracy ± 0.1 C) but water temperature
was taken on-location by a calibrated digital thermometer. pH was measured
using a digital pH meter (Eutech Instruments, accuracy ± 0.01) and salinity
determined using a refractometer (± 0.1 ppt). Dissolved oxygen was determined
by Winkler's azide modification method with an analytical accuracy of ± 0.05
mg/L (APHA 2017).
2.4 Heavy Metal Analysis
Samples were filtered
through 0.45 μm membrane filters and digested with concentrated HNO₃ and H₂O₂
by US EPA Method 3015A. Heavy metal Contents (Pb, Cd, Cr, Ni, Zn) were
determined using Inductively Coupled Plasma Mass Spectrometry (ICP-MS, Perkin
Elmer NexION 2000). Quality control consisted of analysis of certified
reference materials (NIST 1643f), method blanks, and duplicate samples.
Detection limits were: Pb (0.05 μg/L), Cd (0.01 μg/L), Cr (0.1 μg/L), Ni (0.1
μg/L), and Zn (0.5 μg/L). Values c (Recoveries) ranged between 92% and 108%,
with a relative standard deviation<5%.
2.5 Statistical Analysis
The data were processed
by SPSS Statistics 26.0. For all variables, figures demonstrate the mean
variance as mentioned previously in this section as this subsection
illustrates.For seasonal and spatial variations, we used one-way ANOVA. After
each of the seasons is tested in turn for the mean of all other seasons
combined, we applied post-hoc Tuckey's HSD test.They used Pearson correlation
analysis to study the relationship between these parameters. The standard for
choosing p-values is 0.05 or less, rather than to four digits than in previous
sentences.
3. RESULTS
3.1 Physico-Chemical
Parameters
These eco-environmental
conditions will be explored in detail in the following 12 chapters. The
physico-chemical parameters ranging from 140 to 1,800 umol/liter-1 showed
distinct seasonal and spatial variabilities across the three estuaries Air
temperature ranged from 24.8°C(Sakhartar, Winter 2022) to 33.5°C(Bhatye, Summer
2023), with seasonal means of 32.0°C(summer), 27.2°C(Monsoon) and
26.1°C(Winter) Water temperature showed similar patterns, ranging from 24.2°C
to 31.1°C, with highest values in summer and lowest during winter. There was a
strong positive correlation between air and water temperatures (r = 0.91, p
<0.001).
pH values ranged from
7.0 to 8.3 across all stations and seasons, with monsoon samples showing lower
pH values(7.2-7.6) due to freshwater influx and organic acid inputs. Winter and
summer pH values were relatively higher(7.5-8.3), reflecting increased marine
influence and reduced freshwater dilution. Salinity exhibited pronounced
seasonal variation, ranging from 12.8 ppt(Kalbadevi, Monsoon 2022) to 33.2
ppt(Sakhartar, Summer 2023). Monsoon salinity (13-20 ppt) was significantly
lower than winter (20-28 ppt) and summer (26-33 ppt), due to increased river
discharge and freshwater influx.
Dissolved oxygen
concentrations ranged from 4.5 mg/L(Kalbadevi, Summer 2023) to 7.4
mg/L(Sakhartar, Monsoon 2022). Seasonal variability was significant (F = 42.3,
p < 0.001), with highest values during monsoon (6.5-7.4 mg/L) and lowest in
summer (4.5-5.8 mg/L). Kalbadevi estuary showed consistently lower levels of DO
(4.5-6.8 mg/L) than Bhatye (5.4-7.1 mg/L) and Sakhartar(5.8-7.4 mg/L),
indicating stronger organic pollutant load from industrial activities. Negative
correlation was found between water temperature and DO (r = -0.78, p <
0.001), indicating reduced oxygen solubility in high temperatures.
Table 1:
Physico-chemical parameters in Bhatye, Kalbadevi, and Sakhartar estuaries
|
Estuary
|
Season
|
Air Temp (°C)
|
Water Temp (°C)
|
pH
|
Salinity (ppt)
|
DO (mg/L)
|
|
Bhatye
|
Monsoon 2022
|
28.9
|
27.1
|
7.43
|
19.2
|
7.1
|
|
Winter 2022
|
26.2
|
26.1
|
7.89
|
26.3
|
6.2
|
|
Summer 2023
|
33.5
|
31.1
|
8.11
|
30.8
|
5.4
|
|
Kalbadevi
|
Monsoon 2022
|
26.8
|
26.5
|
7.21
|
12.8
|
6.8
|
|
Winter 2022
|
25.8
|
25.3
|
7.52
|
22.7
|
5.8
|
|
Summer 2023
|
31.6
|
29.9
|
7.98
|
31.2
|
4.5
|
|
Sakhartar
|
Monsoon 2022
|
25.7
|
25.1
|
7.56
|
17.8
|
7.4
|
|
Winter 2022
|
24.8
|
24.2
|
7.71
|
20.8
|
6.5
|
|
Summer 2023
|
30.8
|
28.6
|
8.28
|
33.2
|
5.8
|
Table 2: Heavy metal
concentrations in Bhatye, Kalbadevi, and Sakhartar estuaries
|
Estuary
|
Season
|
Pb (μg/L)
|
Cd (μg/L)
|
Cr (μg/L)
|
Ni (μg/L)
|
Zn (μg/L)
|
|
Bhatye
|
Monsoon 2022
|
1.63
|
0.129
|
3.01
|
2.26
|
7.30
|
|
Winter 2022
|
1.90
|
0.161
|
3.72
|
2.98
|
8.76
|
|
Summer 2023
|
3.39
|
0.296
|
6.94
|
4.44
|
13.35
|
|
Kalbadevi
|
Monsoon 2022
|
1.88
|
0.149
|
3.46
|
2.60
|
8.40
|
|
Winter 2022
|
2.19
|
0.185
|
4.28
|
3.43
|
10.08
|
|
Summer 2023
|
3.90
|
0.341
|
7.98
|
5.10
|
15.36
|
|
Sakhartar
|
Monsoon 2022
|
1.39
|
0.110
|
2.56
|
1.92
|
6.21
|
|
Winter 2022
|
1.61
|
0.137
|
3.16
|
2.53
|
7.44
|
|
Summer 2023
|
2.88
|
0.252
|
5.90
|
3.77
|
11.35
|
3.2 Heavy Metal
Concentrations
According to data from a
heavy metal analysis, concentrations detected across the three estuaries and
seasons were different (Table 2). Lead concentrations varied from 1.39 μg/L
(Sakhartar, Monsoon 2022) to 3.90 μg/L (Kalbadevi, Summer 2023), Kalbadevi estuary
showing constantly higher levels of lead due to industrial wastewater
discharge. Cadmium concentrations were relatively low (0.110-0.341 μg/L), all
sites well below the WHO Drinking Water Quality Guidelines 3 μg/L.Chromium
levels varied from 2.56 μg/L to 7.98 μg/L, the Kalbadevi estuary having the
most for this metal during summer (7.98 μg/L), probably due to effluents from
tanneries and electroplating factories nearby.Incidentally Nickel
concentrations were from 1.92 to 5.10 μg/L and zinc levels varied between
6.21-15.36 μg/L. None of these were in excess of WHO allowable limits (Pb 10
μg/L, Cd 3 μg/L, Cr 50 μg/L, Ni 70 μg/L, Zn 5000 μg/L), so in general water
quality was considered acceptable, despite local peaks.Due to less dilution and
greater evaporation, metal concentrations were higher in summer. When the
monsoonal rains came and brought a large amount of fresh water into the sea,
levels then dropped appreciably. The three sites studied, Kalbadevi had the
highest metal pollution index (calculated by adding the concentrations of each
metal divided by the standard) at 0.42, while Bhatye measured 0.36 and
Sakhartar 0.31.
3.3 Spatial and Seasonal
Variations
The data show that
significant differences among estuaries exist in most parameters (p> 0.05).
However, Kalbadevi estuary carried a heavy load of industrial pollution.
Concentrations of heavy metals there were high; ditto for demineralized oxygen
levels (DO). Sakhartar estuary, clean and untarnished by human contact, still
maintained that status with the highest values of DO and lowest entanglement in
waste discards. Bhatye estuary had a little virgin goodness to it as well. The
water was pure in springs and there wasn't just an industrial spot. Cluster
analysis classified the three estuaries into three clear groups of pristine
(Sakhartar), moderately impacted (Bhatye) and anthropogenically influenced
(Kalbadevi).
4. DISCUSSION
The Bhatye, Sakhartar
and Kalbadevi estuaries may be geographically remote from each other but we are
frequently associated with flood relief work in one or more of these areas. The
harpical coastal ecosystem on the whole is a variable entity, as its appearance
and the native forms of life it supports depend not only on natural factors but
also upon human activity. The strong correlation between air and water
temperatures (r = 0.91) suggests efficient heat transfer and little or no
stratification. During the monsoon season, temperature decreases are attributed
to increased cloud cover, reduced solar radiation, and cooler freshwater inputs
from upstream catchments. The pH and salinity vary quite obviously according to
monsoon dynamics. Water between pH values of 7.0 to 7.6) during the monsoon
season (June-August) result from increased terrestrial organic acids and humic
substances and the lackof marine water to counteract this acidic hydrogen.
Chemical salinity levels, meanwhile, shift from monsoon [12.8-20.0 ppt] to
summer [26.2-33.2 ppt], reflect the passage the transitionof brackish water
towards the tome ecological conditions characteristic of the tropical estuary’s
seasonal water cycle (Vijayakumar et al., 2000).Not only are multi-faceted
factors such as temperature, salinity, photosynthesis and respiration, as well
as anthropogenic inputs all at work on the dissolved oxygen and yet at exactly
this moment in human history we have the unprecedented ability to solve those
problems. This study recorded the negative correlation between temperature and
DO (r = -0.78), which accords with basics of gas solubility: as temperature
increases, so does the decrease in solubility of oxygen (Weiss, 1970). But
during the monsoon season, river water drainage increased turbulence leads to
higher levels of atmospheric oxygen and less biological oxygen demand due to
dilution of organic matter. In contrast, DO concentrations are relatively low
in Kalbadevi estuary (4.5-6.8 mg/L) to Bhatye (5.4-7.1 mg/L) and Sakhartar
(5.8-7.4 mg/L) prompting concerns about organic pollution from industrial
effluents and urban run-off. Still within the current range above hypoxic
thresholds (< 2 mg/L), the minimum water temperature in summer is
approaching critical lower limits (4.5 mg/L). Attention must be paid to this,
as hypoxia can have ecological consequences: fish will die; trophic structures
will alter and other habitats degrade (Vaquer-Sunyer& Duarte, 2008).
Stricter controls on industrial effluent discharges should be imposed at
Kalbadevi.
Heavy metal
concentrations within WHO permissible limits meant the good water quality for
estuaries was relatively well maintained. But local spatial variability
suggests there are anthrogenic sites at some of these districts (Chen et al.,
1995). For example, industrial discharge releases at electroplating plants,
tanneries and steel factories probably account for the higher levels of lead
and chromium in Kalbadevi estuary. In this water, chromium concentrations reach
up to 7.98 μg/L, an indication that global environmental fate may be slowly
settling (Chowdhury et al., 2016). As a result, metal concentrations decrease
by 40-60% during the rainy season across three estuaries, a phenomenon observed
in other Indian coastal systems (Mohiuddin et al., 2010; Srichandan et al.,
2016). However, this seasonal dilution may transmit contamination downstream
into coastal ecosystems for marine life. Long-term sediment and biotic
bioacumulation studies are essential to understand the risks of chronic
exposure, since heavy metals are biomagnified by food chains even at low water
column concentrations (Luoma & Rainbow, 2008). The spatial distribution of
zinc remained similar to these other metals. Yet so far concentrations have
been well below WHO limits (from 6.21-15.36 μg/L) and showed little seasonal
change at Kalbadevi estuary. Nickel levels stayed stable (1.92-5.10 μg/L),
suggesting there was a limited impact from the nickel-related factories. Such
substances will most likely all come from the city's industrial waste waters or
from the garbage that year in and out (the strong correlation between zinc and
lead r=0.84, p<0.001).
In comparison with west
coast estuaries have water that is similar or worse in quality in areas such as
heavily industrialized Thane Creek and the Ratnagiri three estuaryare
Furthermore, therefore, for its treatment situation to deteriorate is an
inevitable outcome if We must respond immediately as an intermediate monitoring
site.The Sakhartar estuary, which has little impact on humans and a high
ecological value, should be established for long-term reference. The
limitations of this study its scope in time (three seasonal periods over one
year) and lack of sediment or biological analysis combine to leave
comprehensive ecological health assessment out of reach Future research
projects need to incorporate biological indicators like phytoplankton
diversity, communities in benthic macroinvertebrates and population structure
As Ratnagiri's coastline urbanizes more and more, monitoring should also
include emergent contaminants such as pharmaceuticals, personal care products
and microplastics.
5. CONCLUSIONS
This research provides a
wealth of baseline data on physicochemical parameters and heavy metal content
in three estuarine waters (Bhatye, Kalbadevi and Sakhartar) along the Ratnagiri
coast.
The main findings
include: Temperatures were distinctly seasonal, with air temperature ranging
from 24.8 °C to 33.5 °C and water temperature from 24.2°C up to∼ 31.1°C as a result of
monsoonal dynamics or radiation from the sun.The pH (7.0–8.3) and salinity
(12.8–33.2 ppt) also exhibited pronounced periodic variation; this reflects a
shift between freshwater-dominated (monsoon season) to marine-dominated (summer
season) conditions.All stations measured oxygen concentrations above the
critical threshold (4 mg/L), except for the Kalbadevi estuary area during
summer (4.5 mg/L) which trends towards an elevated organic pollution level due
to industrial effluents.As for heavy metal levels, Pb (1.39 - 3.90 μg/L), Cd
(0.110 - 0.341 μg/L), Cr (2.56 - 7.98μg/L), Ni (1.92 - 5.10μg/L) and Zn (6.21 -
15.36 μg/L) are all within WHO standard lower limit lines. Over all, water
quality is considered acceptable. However, in local areas like Kalbadevi
estuary near industrialized zones there exist peaks. Kalbadevi and its
surroundings show a clear pattern of spatial heterogeneity, with varying
degrees of anthropogenic influence: Sakhartar (pristine but with some local pollution
now) <Bhatye (moderate) <Kalbadevi (heavily industrialized).
Monsoonal dynamics
regulate the water quality, with 40- 60% seasonal reduction in contaminants
compared with summer. These finds demonstrate the need for sustained and
constant monitoring, strict control of industrial discharges and integrated
management of Ratnagiri estuary ecological health. Specific recommendations
include: (1) Establishment of continuous water quality monitoring stations at
all three estuaries. (2) Industries located near Kalbadevi estuary should be
made to limit their effluent discharge standards even more meticulously, in
(3). Sakhartar becomes a marine reserve area and serves as a long-term
reference for future evaluation of estuarine conditions, and (4). Sediment
quality and bioaccumulation studies of commercial fish species in these vital
but now polluted estuaries should be made at least every two years to ensure
that the seas can continue to feed us well. It is imperative to work out early
warning systems and adaptive management strategies for maintaining ecosystem
health in the face of ongoing coastal development and climate change.
ACKNOWLEDGMENTS
The authors acknowledge
the Principal, Head and Director of the Research Centre in Department of
Zoology, Padmashri Vikhe Patil College of Arts, Science and Commerce,
Pravaranagar, for providing the necessary laboratory facilities and valuable
support. The authors also thank Savitribai Phule Pune University, Pune, for
giving permission to carry out this study.
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