Environ Sci Pollut Res (2014) 21:5098–5120 DOI 10.1007/s11356-013-2462-7
RESEARCH ARTICLE
Geochemical behaviour of dissolved trace elements in a monsoon-dominated tropical river basin, Southwestern India G. P. Gurumurthy & K. Balakrishna & M. Tripti & Stéphane Audry & Jean Riotte & J. J. Braun & H. N. Udaya Shankar
Received: 21 August 2013 / Accepted: 13 December 2013 / Published online: 28 December 2013 # Springer-Verlag Berlin Heidelberg 2013
Abstract The study presents a 3-year time series data on dissolved trace elements and rare earth elements (REEs) in a monsoon-dominated river basin, the Nethravati River in tropical Southwestern India. The river basin lies on the metamorphic transition boundary which separates the Peninsular Gneiss and Southern Granulitic province belonging to Archean and Tertiary–Quaternary period (Western Dharwar Craton). The basin lithology is mainly composed of granite gneiss, charnockite and metasediment. This study highlights the importance of time series data for better estimation of metal fluxes and to understand the geochemical behaviour of metals in a river basin. The dissolved trace elements show seasonality in the river water metal concentrations forming two distinct groups of metals. First group is composed of heavy metals and minor elements that show higher concentrations during dry season and lesser concentrations during the monsoon season. Second group is composed of metals belonging to lanthanides and actinides with higher concentration in the monsoon and
lower concentrations during the dry season. Although the metal concentration of both the groups appears to be controlled by the discharge, there are important biogeochemical processes affecting their concentration. This includes redox reactions (for Fe, Mn, As, Mo, Ba and Ce) and pH-mediated adsorption/desorption reactions (for Ni, Co, Cr, Cu and REEs). The abundance of Fe and Mn oxyhydroxides as a result of redox processes could be driving the geochemical redistribution of metals in the river water. There is a Ce anomaly (Ce/Ce*) at different time periods, both negative and positive, in case of dissolved phase, whereas there is positive anomaly in the particulate and bed sediments. The Ce anomaly correlates with the variations in the dissolved oxygen indicating the redistribution of Ce between particulate and dissolved phase under acidic to neutral pH and lower concentrations of dissolved organic carbon. Unlike other tropical and major world rivers, the effect of organic complexation on metal variability is negligible in the Nethravati River water.
Responsible editor: Céline Guéguen
Keywords Nethravati–Gurupur Rivers . Dissolved trace elements . REEs . Redox processes . Sorption reaction . Tropical river . Cerium anomaly
G. P. Gurumurthy Manipal Centre for Natural Sciences, Manipal University, Manipal 576104, India K. Balakrishna (*) : M. Tripti : H. N. Udaya Shankar Department of Civil Engineering, Manipal Institute of Technology, Manipal University, Manipal 576104, India e-mail: [email protected] S. Audry : J. Riotte : J. J. Braun GET UMR 5563, Université Paul Sabatier, IRD and CNRS, 14, avenue E. Belin, 31400 Toulouse, France J. Riotte : J. J. Braun Indo-French Cell for Water Sciences, Joint IRD-IISc Laboratory, Indian Institute of Science, Bangalore 560012, India
Introduction The geochemical studies of dissolved trace elements have attracted scientific attention due to their non-degradability and bioaccumulation in the environment. Trace elements, dissolved or particulate, present in the hydrological system could be derived either from natural or anthropogenic sources. The biogeochemical processes in the aquatic system control the solubility, bioavailability, toxicity and ultimate fate of trace metals through their discharge into the open oceans. These biogeochemical processes include biological uptake, organic/
Environ Sci Pollut Res (2014) 21:5098–5120
inorganic complexation, precipitation, sorption and redox reactions (Shiller et al. 1997; Morford and Emerson 1999; Lion et al. 1982; van den Berg et al. 1987; Froelich et al. 1979). These biogeochemical processes often determine the conservative–nonconservative behaviour of metals and their residence time in the fluvial system. An understanding of biogeochemical processes that control trace element concentration in different river systems is required to understand the geochemical mass balance, the partitioning of trace elements between the particulate and dissolved phases and their residence time in the open ocean. Most of the available data on dissolved trace element concentrations focus either on human-affected systems of industrialised countries or major rivers of the world. Also, the reported metal flux estimates are based on single sampling (Gaillardet et al. 2003) with high uncertainties. Considering the variability of trace elements with seasons (Shiller 1997, 2002, 2010) and their diel cycles (Nimick et al. 2003, 2005, 2010), precise flux estimation requires time series elemental concentrations. This paper presents time series (3-year monitoring on a monthly basis) of dissolved trace element and rare earth element (REE) concentrations on a monsoon-dominated humid tropical river, the Nethravati–Gurupur basin. In spite of rapid industrial and population growth in the Indian subcontinent, there are very limited geochemical datasets on dissolved (Ajmal et al. 1985; Rengarajan and Sarin 2004; Tripti et al. 2013a) and particulate trace metal (Ramesh et al. 1990; Chakrapani and Subramanian 1996; Stummeyer et al. 2002) chemistry of the river basins. Most of these studies are either restricted to urban stretch of a river or based on few heavy Fig. 1 Map of Nethravati– Gurupur River basin showing the sample locations (lithology map obtained from Geological Society of India 1981)
5099
metals. With this background, the present research is taken up to meet the following objectives: (a) to generate time series dissolved trace element dataset of the surface waters draining granite gneissic terrain, which happens to be first on the Nethravati–Gurupur River basin, (b) to understand the biogeochemical processes and associated elemental redistribution in a monsoon-dominated humid tropical river basin and (c) to understand the temporal variability of trace element and REE concentrations in the river basin. A smaller catchment with lesser heterogeneity in the lithology provides better insights on the geochemical parameters controlling the concentration variability.
Materials and methodology Study area The Nethravati and Gurupur Rivers originate at an elevation of ∼900–1,800 m above mean sea level, in densely forested Western Ghats. It flows southwest from its origin for about 147 km and meets the Arabian Sea at Mangalore. The total drainage area of the river is 3,657 km2. The major tributaries are Kumaradhara, Shishila hole, Gundiya hole and Neriya hole (Fig. 1). The river basin is composed of rock types belonging to Tertiary and Quaternary eras in the lower catchments and older (Archaean) gneissic complex in the upper catchments. The basin is located on the southwestern side of Western Dharwar Craton, a metamorphic transition boundary demarking the southern granulite province from the Peninsular Gneisses. The Peninsular Gneiss/ Archean tonalitic–trondhjemitic–granodioritic gneiss is a major
5100
Environ Sci Pollut Res (2014) 21:5098–5120
groundwater. The discharge variation is quite similar in all the four gauging stations (Fig. 2a) of the Nethravati–Gurupur basin. Therefore, in the following discussion, the discharge data from station Mugeru, where the discharge data is available throughout the year, is used to compare the temporal variation of metals in the river water. The river carries huge amount of sediments from the forested regions of Western Ghats during the rainy season. While the sediment transport during the base flow season is quite negligible, average annual sediment discharge from Nethravati River at Bantwala station is 1.25×106 t (Dwarakish et al. 2009).
litho unit with an age of 3.3 to 3.4 Ga (Bhaskar Rao et al. 1991). The greenstone–amphibolitic facies metamorphic rocks and granulites could be seen in patches. The basin is lithologically composed of about 83 % migmatites and granodiorites, 6 % metasediments, 5 % charnockites and 2 % laterites and amphibolites (Fig. 1). The bedrock weathering process in the Nethravati–Gurupur River basin is intense and is induced by warm temperature and higher surface runoff. Silicate weathering is dominating in the area because of the nature of the bedrock. The weathering of primary minerals leads to kaolinite to gibbsite secondary mineral formation in the soil profiles (Gurumurthy et al. 2012). The discharge of Nethravati River together with Gurupur River accounts for 8 % of the total water discharge of west-flowing rivers of Peninsular India (Rao 1979; Subramanian et al. 1987) to the Arabian Sea. The Nethravati and Gurupur River flow depends on seasons; about 93 % of the total discharge is between June and October (southwest monsoon). The discharge during the lean flow season could be contributed by the
The surface water samples were collected from the centre of the river in 1 L polypropylene bottles for dissolved trace metal, major ion and dissolved organic carbon (DOC) measurement. The water samples were collected over a period of 3 years between 2006 (from October 2006 to September
4000
3 -1 Discharge (m sec )
3000
BC Road, Bantwala Mugeru, Nethravati river Shanthimugeru, Kumaradhara River Adoor, Gurupur River
(a)
2000
1000
Oct-06 Nov-06 Dec-06 Jan-07 Feb-07 Mar-07 Apr-07 May-07 Jun-07 Jul-07 Aug-07 Sep-07 Jan-09 Feb-09 Mar-09 Apr-09 May-09 Jun-09 Jul-09 Aug-09 Sep-09 Oct-09 Nov-09 Dec-09 Jan-10 Feb-10 Mar-10 Apr-10 May-10 Jun-10 Jul-10 Aug-10 Sep-10 Oct-10 Nov-10 Dec-10
0
1600
10
(b) 8
1200 1000
6
800
Q pH
600
DO (mg L-1) DOC (mg l-1)
400 200
4
2
0 Oct-06 Nov-06 Dec-06 Jan-07 Feb-07 Mar-07 Apr-07 May-07 Jun-07 Jul-07 Aug-07 Sep-07 Jan-09 Feb-09 Mar-09 Apr-09 May-09 Jun-09 Jul-09 Aug-09 Sep-09 Oct-09 Nov-09 Dec-09 Jan-10 Feb-10 Mar-10 Apr-10 May-10 Jun-10 Jul-10 Aug-10 Sep-10 Oct-10 Nov-10 Dec-10
0
pH, DO and DOC
1400
3 -1 Discharge (m sec )
Fig. 2 a, b Temporal variation of discharge, physicochemical parameters and dissolved organic carbon (average and standard deviation of all the sampling stations) in the Nethravati Gurupur River catchment. Note that the discharge data for Mugeru station is collected from Major Irrigation Department, Government of Karnataka, and for remaining stations, data are from CWC, Government of India. To maintain more clarity in figure, only upper side of the deviation is plotted in the figures
Sampling and analysis
Environ Sci Pollut Res (2014) 21:5098–5120
2007) and 2011 (January 2009 to December 2010), every month. Five water samples were collected from the Nethravati River and its tributaries between October 2006 and September 2007, while eight water samples were collected from Nethravati and Gurupur Rivers between January 2009 and December 2010. Onsite parameters such as pH, electrical conductivity (EC) and dissolved oxygen (DO) were recorded during sample collection using HACH® multiparameter apparatus connected to probes. Samples were immediately filtered through 0.22-μm pore size polycarbonate filters (Nuclepore), fitted in a Sartorius polycarbonate filter holder operated through Mytivac hand vacuum pump. Filtration was carried out under HEPA-filtered laminar flow bench. The first 100 mL of the filtration was systematically discarded to clean the membrane and filtration apparatus. Filtered solutions for cations and trace element measurements were acidified with double-distilled HNO3 to pH
RESEARCH ARTICLE
Geochemical behaviour of dissolved trace elements in a monsoon-dominated tropical river basin, Southwestern India G. P. Gurumurthy & K. Balakrishna & M. Tripti & Stéphane Audry & Jean Riotte & J. J. Braun & H. N. Udaya Shankar
Received: 21 August 2013 / Accepted: 13 December 2013 / Published online: 28 December 2013 # Springer-Verlag Berlin Heidelberg 2013
Abstract The study presents a 3-year time series data on dissolved trace elements and rare earth elements (REEs) in a monsoon-dominated river basin, the Nethravati River in tropical Southwestern India. The river basin lies on the metamorphic transition boundary which separates the Peninsular Gneiss and Southern Granulitic province belonging to Archean and Tertiary–Quaternary period (Western Dharwar Craton). The basin lithology is mainly composed of granite gneiss, charnockite and metasediment. This study highlights the importance of time series data for better estimation of metal fluxes and to understand the geochemical behaviour of metals in a river basin. The dissolved trace elements show seasonality in the river water metal concentrations forming two distinct groups of metals. First group is composed of heavy metals and minor elements that show higher concentrations during dry season and lesser concentrations during the monsoon season. Second group is composed of metals belonging to lanthanides and actinides with higher concentration in the monsoon and
lower concentrations during the dry season. Although the metal concentration of both the groups appears to be controlled by the discharge, there are important biogeochemical processes affecting their concentration. This includes redox reactions (for Fe, Mn, As, Mo, Ba and Ce) and pH-mediated adsorption/desorption reactions (for Ni, Co, Cr, Cu and REEs). The abundance of Fe and Mn oxyhydroxides as a result of redox processes could be driving the geochemical redistribution of metals in the river water. There is a Ce anomaly (Ce/Ce*) at different time periods, both negative and positive, in case of dissolved phase, whereas there is positive anomaly in the particulate and bed sediments. The Ce anomaly correlates with the variations in the dissolved oxygen indicating the redistribution of Ce between particulate and dissolved phase under acidic to neutral pH and lower concentrations of dissolved organic carbon. Unlike other tropical and major world rivers, the effect of organic complexation on metal variability is negligible in the Nethravati River water.
Responsible editor: Céline Guéguen
Keywords Nethravati–Gurupur Rivers . Dissolved trace elements . REEs . Redox processes . Sorption reaction . Tropical river . Cerium anomaly
G. P. Gurumurthy Manipal Centre for Natural Sciences, Manipal University, Manipal 576104, India K. Balakrishna (*) : M. Tripti : H. N. Udaya Shankar Department of Civil Engineering, Manipal Institute of Technology, Manipal University, Manipal 576104, India e-mail: [email protected] S. Audry : J. Riotte : J. J. Braun GET UMR 5563, Université Paul Sabatier, IRD and CNRS, 14, avenue E. Belin, 31400 Toulouse, France J. Riotte : J. J. Braun Indo-French Cell for Water Sciences, Joint IRD-IISc Laboratory, Indian Institute of Science, Bangalore 560012, India
Introduction The geochemical studies of dissolved trace elements have attracted scientific attention due to their non-degradability and bioaccumulation in the environment. Trace elements, dissolved or particulate, present in the hydrological system could be derived either from natural or anthropogenic sources. The biogeochemical processes in the aquatic system control the solubility, bioavailability, toxicity and ultimate fate of trace metals through their discharge into the open oceans. These biogeochemical processes include biological uptake, organic/
Environ Sci Pollut Res (2014) 21:5098–5120
inorganic complexation, precipitation, sorption and redox reactions (Shiller et al. 1997; Morford and Emerson 1999; Lion et al. 1982; van den Berg et al. 1987; Froelich et al. 1979). These biogeochemical processes often determine the conservative–nonconservative behaviour of metals and their residence time in the fluvial system. An understanding of biogeochemical processes that control trace element concentration in different river systems is required to understand the geochemical mass balance, the partitioning of trace elements between the particulate and dissolved phases and their residence time in the open ocean. Most of the available data on dissolved trace element concentrations focus either on human-affected systems of industrialised countries or major rivers of the world. Also, the reported metal flux estimates are based on single sampling (Gaillardet et al. 2003) with high uncertainties. Considering the variability of trace elements with seasons (Shiller 1997, 2002, 2010) and their diel cycles (Nimick et al. 2003, 2005, 2010), precise flux estimation requires time series elemental concentrations. This paper presents time series (3-year monitoring on a monthly basis) of dissolved trace element and rare earth element (REE) concentrations on a monsoon-dominated humid tropical river, the Nethravati–Gurupur basin. In spite of rapid industrial and population growth in the Indian subcontinent, there are very limited geochemical datasets on dissolved (Ajmal et al. 1985; Rengarajan and Sarin 2004; Tripti et al. 2013a) and particulate trace metal (Ramesh et al. 1990; Chakrapani and Subramanian 1996; Stummeyer et al. 2002) chemistry of the river basins. Most of these studies are either restricted to urban stretch of a river or based on few heavy Fig. 1 Map of Nethravati– Gurupur River basin showing the sample locations (lithology map obtained from Geological Society of India 1981)
5099
metals. With this background, the present research is taken up to meet the following objectives: (a) to generate time series dissolved trace element dataset of the surface waters draining granite gneissic terrain, which happens to be first on the Nethravati–Gurupur River basin, (b) to understand the biogeochemical processes and associated elemental redistribution in a monsoon-dominated humid tropical river basin and (c) to understand the temporal variability of trace element and REE concentrations in the river basin. A smaller catchment with lesser heterogeneity in the lithology provides better insights on the geochemical parameters controlling the concentration variability.
Materials and methodology Study area The Nethravati and Gurupur Rivers originate at an elevation of ∼900–1,800 m above mean sea level, in densely forested Western Ghats. It flows southwest from its origin for about 147 km and meets the Arabian Sea at Mangalore. The total drainage area of the river is 3,657 km2. The major tributaries are Kumaradhara, Shishila hole, Gundiya hole and Neriya hole (Fig. 1). The river basin is composed of rock types belonging to Tertiary and Quaternary eras in the lower catchments and older (Archaean) gneissic complex in the upper catchments. The basin is located on the southwestern side of Western Dharwar Craton, a metamorphic transition boundary demarking the southern granulite province from the Peninsular Gneisses. The Peninsular Gneiss/ Archean tonalitic–trondhjemitic–granodioritic gneiss is a major
5100
Environ Sci Pollut Res (2014) 21:5098–5120
groundwater. The discharge variation is quite similar in all the four gauging stations (Fig. 2a) of the Nethravati–Gurupur basin. Therefore, in the following discussion, the discharge data from station Mugeru, where the discharge data is available throughout the year, is used to compare the temporal variation of metals in the river water. The river carries huge amount of sediments from the forested regions of Western Ghats during the rainy season. While the sediment transport during the base flow season is quite negligible, average annual sediment discharge from Nethravati River at Bantwala station is 1.25×106 t (Dwarakish et al. 2009).
litho unit with an age of 3.3 to 3.4 Ga (Bhaskar Rao et al. 1991). The greenstone–amphibolitic facies metamorphic rocks and granulites could be seen in patches. The basin is lithologically composed of about 83 % migmatites and granodiorites, 6 % metasediments, 5 % charnockites and 2 % laterites and amphibolites (Fig. 1). The bedrock weathering process in the Nethravati–Gurupur River basin is intense and is induced by warm temperature and higher surface runoff. Silicate weathering is dominating in the area because of the nature of the bedrock. The weathering of primary minerals leads to kaolinite to gibbsite secondary mineral formation in the soil profiles (Gurumurthy et al. 2012). The discharge of Nethravati River together with Gurupur River accounts for 8 % of the total water discharge of west-flowing rivers of Peninsular India (Rao 1979; Subramanian et al. 1987) to the Arabian Sea. The Nethravati and Gurupur River flow depends on seasons; about 93 % of the total discharge is between June and October (southwest monsoon). The discharge during the lean flow season could be contributed by the
The surface water samples were collected from the centre of the river in 1 L polypropylene bottles for dissolved trace metal, major ion and dissolved organic carbon (DOC) measurement. The water samples were collected over a period of 3 years between 2006 (from October 2006 to September
4000
3 -1 Discharge (m sec )
3000
BC Road, Bantwala Mugeru, Nethravati river Shanthimugeru, Kumaradhara River Adoor, Gurupur River
(a)
2000
1000
Oct-06 Nov-06 Dec-06 Jan-07 Feb-07 Mar-07 Apr-07 May-07 Jun-07 Jul-07 Aug-07 Sep-07 Jan-09 Feb-09 Mar-09 Apr-09 May-09 Jun-09 Jul-09 Aug-09 Sep-09 Oct-09 Nov-09 Dec-09 Jan-10 Feb-10 Mar-10 Apr-10 May-10 Jun-10 Jul-10 Aug-10 Sep-10 Oct-10 Nov-10 Dec-10
0
1600
10
(b) 8
1200 1000
6
800
Q pH
600
DO (mg L-1) DOC (mg l-1)
400 200
4
2
0 Oct-06 Nov-06 Dec-06 Jan-07 Feb-07 Mar-07 Apr-07 May-07 Jun-07 Jul-07 Aug-07 Sep-07 Jan-09 Feb-09 Mar-09 Apr-09 May-09 Jun-09 Jul-09 Aug-09 Sep-09 Oct-09 Nov-09 Dec-09 Jan-10 Feb-10 Mar-10 Apr-10 May-10 Jun-10 Jul-10 Aug-10 Sep-10 Oct-10 Nov-10 Dec-10
0
pH, DO and DOC
1400
3 -1 Discharge (m sec )
Fig. 2 a, b Temporal variation of discharge, physicochemical parameters and dissolved organic carbon (average and standard deviation of all the sampling stations) in the Nethravati Gurupur River catchment. Note that the discharge data for Mugeru station is collected from Major Irrigation Department, Government of Karnataka, and for remaining stations, data are from CWC, Government of India. To maintain more clarity in figure, only upper side of the deviation is plotted in the figures
Sampling and analysis
Environ Sci Pollut Res (2014) 21:5098–5120
2007) and 2011 (January 2009 to December 2010), every month. Five water samples were collected from the Nethravati River and its tributaries between October 2006 and September 2007, while eight water samples were collected from Nethravati and Gurupur Rivers between January 2009 and December 2010. Onsite parameters such as pH, electrical conductivity (EC) and dissolved oxygen (DO) were recorded during sample collection using HACH® multiparameter apparatus connected to probes. Samples were immediately filtered through 0.22-μm pore size polycarbonate filters (Nuclepore), fitted in a Sartorius polycarbonate filter holder operated through Mytivac hand vacuum pump. Filtration was carried out under HEPA-filtered laminar flow bench. The first 100 mL of the filtration was systematically discarded to clean the membrane and filtration apparatus. Filtered solutions for cations and trace element measurements were acidified with double-distilled HNO3 to pH
