Chemical weathering controls on variations in the molybdenum isotopic composition of river water: Evidence from large rivers in China

Climate Variability Controls on CO2 Consumption Fluxes and Carbon Dynamics for Monsoonal Rivers: Evidence From Xijiang River, Southwest China

“…H 2 SO 4 is a critical agent in carbonate weathering in Southwest China (Li et al, ; Xu & Liu, ) which can be mainly produced naturally through the oxidation of pyrite (Li et al, ; Liu, ; Xu & Liu, ). SO 4 2− /Na + and Ca 2+ /Na + ratios are similar to other studies in the Xijiang catchment (Gao et al, ; Sun, Han, Li, et al, ; Sun et al, ; Wang et al, ; Wei et al, ; Xu & Liu, , 2010) and overlap the range throughout the world (Figure b). However, the Xijiang River is more highly affected by carbonate weathering and by the action of H 2 SO 4 than most rivers in the world (Figure b).…”

Seasonal and Spatial Variation of Mo Isotope Compositions in Headwater Stream of Xijiang River Draining the Carbonate Terrain, Southwest China

“…The dissolved Mo isotopic compositions (δ 98/95 Mo) of the upper XJR vary between 0.51% and 1.78% (Table 1 and Figure 3), with an average of 0.96 ± 0.19% (1 SD) in the wet season and 1.09 ± 0.22% (1 SD) in the dry season, respectively. These δ 98/95 Mo values are within the ranges of the global river water reported in the previous studies (0.15% to 2.40% , Figure 3a) [15,16,19,21,33,34]. As a river flowing through the essentially mono-lithological area (carbonate rock), the δ 98/95 Mo values of upper XJR water are significantly higher than that of the mean value of average basalts and granites (0.0% to 0.4% ) [19,35].…”

“…For the HSR, Mo concentrations varied between 5.7 nmol/L and 8.1 nmol/L (with an average value of 6.7 nmol/L) during the wet season, between 6.8 nmol/L and 7.9 nmol/L (with an average value of 7.5 nmol/L) during the dry season. The Mo concentrations in all samples are higher than the world river average value (4.4 nmol/L) [31], but the range of Mo concentrations are similar to the lower XJR (5.3-10.5 nmol/L) [15]. Along the mainstream of the upper XJR (N1-N7, H1-H4), the variation in Mo concentrations is extensive ( Figure 2), with no significant pattern of spatial distribution.…”

“…As a river flowing through the essentially mono-lithological area (carbonate rock), the δ 98/95 Mo values of upper XJR water are significantly higher than that of the mean value of average basalts and granites (0.0‰ to 0.4‰) [19,35]. In contrast, the dissolved Mo isotopic compositions of upper XJR are slightly lower than that of the lower XJR (1.04‰ to 1.31‰) [15], except for the site H3 during the dry season ( Figure 3a). It should be noted that the river waters from the NPR have lower δ 98/95 Mo ratios in comparison with the BPR and HSR during the two sampling periods (Figure 3b).…”

“…Molybdenum (Mo) is a metal with seven naturally occurring isotopes: 92 Mo (14.84%), 94 Mo (9.25%), 95 Mo (15.92%), 96 Mo (16.68%), 97 Mo (9.55%), 98 Mo (24.13%), 100 Mo (9.63%) [14]. Mo is one of the most abundant transition metals in the ocean and is very sensitive to changes in redox conditions [15,16]. Recently, Mo isotope systematics has become increasingly important as a new proxy Under the influence of a warm subtropical climate, the Beipanjiang, Nanpanjiang and Hongshuihe River catchments have an average annual air temperature of 14 to 22 °C in the entire drainage basin [26,28].…”