Studies on Heavy Metal Contamination and Physico-chemical Properties of Godavari River Water at Rajahmundry, Andhra Pradesh

The present study is aimed to examine the water quality of the Godavari River at Rajahmundry A.P., India. Water samples from Kotillingala Revu, Kovur Godavari river bridge, Saraswati Ghat, Dowleswaram, Pushkar Ghat were collected and analysed for pH, Electrical conductivity, Total hardness, TDS, DO, BOD, COD, Nitrates. The concentration of six heavy metals were analysed quantitatively using Atomic Absorption Spectrophotometer.


INTROdUCTION
After Ganges, the Godavari is the longest river in India, covers total area of 312,812 km 2 1,2 . It originates near Nashik, flows through five states and empties into the Bay of Bengal 3 . State wise distribution of Godavari basin is represented in Figure 1 and 2.
In Andhra Pradesh, it flows through the Papi hills 4,5 . In Rajahmundry region, the river water is polluted by many industries, domestic sewage and municipal wastages. In this research work, water samples from Kotillingala Revu, Kovur Godavari river bridge, Saraswati Ghat, Dowleswaram, Pushkar Ghat in Andhra Pradesh were collected and quality of collected samples were analysed.

Study area
In Rajahmundry, the Godavari River is polluted by industrial effluents and domestic waste water 6 . The name of the water quality sites, latitude and longitude are shown in Table 1. Water samples were collected once in every month from the water quality monitoring station Rajahmundry and samples were collected from the surface waters of the River. Samples were collected from June 2020 to May 2021.
The analysis included 14 water quality parameters like pH, electrical conductivity, total hardness, total dissolved solids, dissolved oxygen, biological oxygen demand, chemical oxygen demand and nitrates were monitored by sampling at 5 stations for 12 months (2020-2021). The quality of water samples were analysed as per the standard methods 7 . Trace metal analysis was carried out using Atomic Absorption Spectrometer (AAS) following standard methods given in APHA (2012) 8 .

RESULTS ANd dISCUSSION
Among the 840 observations, only maximum, minimum, mean and standard deviation values are shown in Table 2.

pH
During the study period, the water pH was slightly basic at all stations ( Table 2). It ranged from 7.65 to 9.56. The mild alkaline nature of river water attributed to the presence of CO 2 in water as bicarbonate 9 .

Electrical conductivity
The level of salinity indicated by electrical conductivity 10 . According to WHO standards, EC value within 400 μ mho/cm is acceptable 11 . The current investigation showed that EC value was 101 to 170 μ mho/cm, which indicated the lower level of ionic concentration Table 2.

Total dissolved solids
TDS showed a maximum value in Kotillingala Revu from September 2020 to January 2021 (410 to 441 mg/L) followed by Dowleswaram from September 2020 to December 2020 (410 to 398 mg/L). According to USPHS (United States Public Health Services, 1962) standard, TDS value should not exceed 500 mg/L 12 .

dO, bOd, COd
In the present study, the range of DO over a period of one year from June 2020 to April 2021 was found to be high at all five stations, mean value in between 6.85 to 7.44 shown in Table 2. During the study period, DO content was found in between 5.12 to 8.04 at all five stations. The oxygen balance of an aquatic environment plays an important role in pollution. The B.O.D and C.O.D. are interrelated mainly due to effluents. Present study agrees with previous report, investigated by Srinivasarao et al., (2008) 13 . The present study indicated that the quality of river water is in permissible limits (BIS 10500 (2012) 14 because of maximum level of dissolved oxygen.

Hardness
Hardness mainly due to dissolved Ca, Mg salts. In the present study, hardness found from 190 mg/L to 356 mg/L at all sites. The hard water causes kidney stones in humans 15 .
Because of flood, nitrates contributing algae from rocks minimizes fixation of nitrates during June to September 2020 in all stations.

Chromium
Chromium is used in many industries 16 . These industries discharge Cr (III) and Cr (VI). Cr (VI) is carcinogenic and toxic 17 . From the Table 2, chromium concentration found from 0.34 to 14.45 µg/L (within acceptable limit 50 µg/L). The maximum chromium concentration (14.45 µg/L) was found at Kotillingala Revu in April 2021.

Copper
The intake of large amount of copper causes chronic health issues 18 . From the present investigation, copper concentration was found between 0.18 and 28.08 µg/L, within the acceptable limit of 50 µg/L 14 . The highest copper concentration (28.08 µg/L) was observed at Kovur in May 2021 and minimum copper concentration (0.18 µg/L) was found at Pushkar ghat in June 2020.

Nickel
Nickel concentration found in between 1.10 to 19.28 µg/L. The maximum nickel concentration (19.28 µg/L) was found at Kovur Godavari river bridge in April 2021.

Lead
Intake of excess of lead causes adverse health effects, severely affect the CNS, loss of memory. In adults, chronic lead toxicity leads to joint pain and gastrointestinal symptoms 19 . Lead concentration varies from o.45 to 5.05 µg/L, but within the acceptable limit of 10 µg/L. The maximum lead concentration (5.05 µg/L) was found in Kovur Godavari river bridge at April 2021.

Zinc
Zinc concentration found from 0.0006 to 0.112 mg/L (acceptable limit 5 mg/L). The maximum lead concentration (0.112 mg/L) was found in Kotillingala Revu in May 2021.

Iron
The intake of large amount of iron leads tissue damage 18 . Iron concentration found in between 0.003 to 0.190 mg/L, however within the acceptable limit of 0.3 mg/L. The maximum iron concentration (0.190 mg/L) was found in Dowleswaram in January 2021.
According to BIS 10500 (2012), the requirement (acceptable limit) is given in Table 3.  21 . The pH, temperature, and the water disturbance affect the levels of these heavy metals in an aquatic environment. For example, heavy metals are released more easily into the water at lower pH and higher temperatures. Although many metals are considered essential, they become toxic at higher concentrations due to their ability to cause oxidative stress by forming free radicals, which can react with cellular structure proteins, enzymes and membrane systems 22 . The pollution of heavy metals in our atmosphere, soils and waters are all due to human activity 23 . Heavy metals can be removed from water. Agricultural waste, such as dairy manure, remaining waste material from rice and peanuts, natural soil seem to be the best to remove heavy metals 24 .

CONCLUSION
Based on findings, it was concluded that the water from the study area is basic in nature and saturated with dissolved oxygen. Godavari river is being polluted with the discharge of industrial effluents at Rajahmundry. There is an urgency to take up protection of river water.