wAbstract
@The study gives insight into the source of major ions concentration
and their seasonal variability, chemical weathering rates and
associated CO2 consumption in the Godavari
River Basin (GRB). The results show that the Godavari river basin
water was mildly alkaline, with a wide range of TDS (40 to 550
mgL-1). The most dominant anion was HCO3-
followed by Cl- and the most dominant cation was Ca2+
followed by Na+ for all three sampling seasons. The
average molar ratio of Cl-/Na+ was 0.59
in pre-monsoon, 0.51 for post-monsoon and 0.66 in monsoon, which
is lower than the values, reported in earlier studies. The range
of precipitation corrected molar ratio for (Ca2+/Na+)
was 0.20 to 1.84 in pre-monsoon, 0.59 to 1.59 in post-monsoon
and 0.35 to 2.09 in monsoon season, (Mg2+/Na+)
was 0.26 to 1.18, 0.24 to 0.62 and 0.17 to 1.42 in pre-monsoon,
post-monsoon and monsoon respectively, while (HCO3-/Na+)
was 2.08 to 7.0 in pre-monsoon, 1.98 to 4.05 in post-monsoon and
1.67 to 5.79 in monsoon, which indicated the influence of basalt
weathering on river water chemistry. Factor analysis indicated
the vital role of silicate and carbonate weathering along with
atmospheric and anthropogenic input that govern the water chemistry
of the GRB. The chemical weathering rate GRB varied from 17.61
to 68.16 tkm-2yr-1 with an average of 39.49
tkm-2yr-1 in pre-monsoon, from 27.94 to
65.67 with the average of 42.02 tkm-2yr-1
in post-monsoon season and from 17.53 to 62.95 tkm-2yr-1
with an average value of 34.69 tkm-2yr-1
in monsoon. The associated CO2 consumption
rate due to chemical weathering in the GRB was `0.25~1012
mol yr-1 which is `1.04 of the annual global CO2 consumption (24~1012 mol yr-1)
by chemical weathering of silicate and carbonate rocks. The average
annual CO2 drawdown by Deccan trap (area
5~1015 km2) based on CO2
consumption rate due to silicate weathering determined in this
study was 0.29~1012 mol yr-1, `2.48 of
the annual global CO2 consumption (11.7~1012
mol yr-1) by silicate weathering [Gaillardet,J., Dupre,B.,
Allegre,C.J., 1999. Global silicate weathering and CO2
consumption rates reduced from the chemistry of large rivers.
Chemical Geology 159, 3-30.]. The present study was the first
attempt to calculate weathering rate of Deccan trap using major
ion chemistry of the Godavari River water, the third largest river
in India. The study further provides the inventory for CO2 consumption
on river basin scale, which is an important consideration from
the point of view of global warming.
Keywords: Basalt weathering; Carbon dioxide consumption; Chemical
weathering rate; Godavari river basin, Indiax
1. Introduction
2. Study area
3. Materials and methods
4. Results
5. Discussion
@5.1. Atmospheric supply (cyclic salt)
@5.2. Weathering
@5.3. Anthropogenic input
@5.4. Statistical analysis
@@5.4.1. Analysis of variance (ANOVA)
@@5.4.2. Factor analysis
@5.5. Effective CO2 pressure
@5.6. Chemical weathering rates
@5.7. CO2 consumption rates
6. Conclusion
Acknowledgements
Appendix A. Supplementary data
References