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| Abstract Submission No. | ABS-2022-05-0236 |
| Title of Abstract | Removal of phosphate through adsorption on estuarine sediments in the Indian estuaries |
| Authors | Kiran Kumar Reddy Shiligireddy, Dipin Ghosh, Narasimha Rao, VVSS Sarma |
| Organisation | |
| Address | CSIR-National Institute of Oceanography (NIO), D. No. 8-45-9/2, Chinna Waltair Visakhapatnam, Andhra Pradesh, India Pincode: 530003 Mobile: 9908464295 E-mail: skiran2888@gmail.com |
| Country | India |
| Presentation | Poster |
| Abstract | Dissolve inorganic phosphorus is an essential nutrient for all living organisms and plays an important role in regulating the primary production in the aquatic environment. Removal of phosphate through adsorption on sediment particles was reported to control the flux of phosphate to the coastal waters. This mechanism plays a crucial role on limiting flux of phosphate the coastal waters as excess phosphate could lead to formation of eutrophication and formation of dead zones. The intensive use of artificial fertilizers in agriculture increases the phosphate concentration in the river water and its removal to sediment is dependent on various factors such as particulate organic matter, pH, salinity, clay minerals, iron oxides, etc. Despite India being the second largest country in the utilization of fertilizers, after China, coastal eutrophication was not reported along the Indian coast and it is possible that significant fraction of dissolved inorganic phosphate may be efficiently removed from the water column resulting in low flux to coast. In order to examine this hypothesis, a series of P adsorption/desorption experiments were conducted on the estuarine sediments collected from 12 estuaries along the Indian coast to assess the adsorption capacity and influencing factors on P adsorption. Our results suggested that small estuaries (river discharge <2000 m3/s) have the greater adsorption capacity (up to 10 µM) over the large estuaries (>10000 m3/s) (up to 2 µM). The amount of P adsorption on these estuarine sediments is linearly related with the particulate organic carbon (POC), the proportion of clay and inversely related with salinity. The high pH (Avg. 7.8) condition of small estuaries supports high adsorption than the large estuaries containing low pH (Avg. 7.0) suggesting that the characteristics of these sediments play a vital role on P adsorption. Neglecting these physicochemical processes in estuarine systems may lead to the overestimation of P flux to the coastal ocean. This study confirms the high P adsorption capacities of Indian estuarine sediments might be the reason for low P availability in the coastal regions that prevent the formation of eutrophication and oxygen minimum zones along the Indian coast due to river discharge. Keywords: Phosphate; adsorption; estuarine sediments; clay minerals; Indian peninsular rivers |