Quantifying Transport of Particulate Inorganic Carbon in the Madre de Dios River

Transcription

1 Quantifying Transport of Particulate Inorganic Carbon in the Madre de Dios River Daniel Stirton Department of Earth Sciences University of Southern California Abstract Transport of particulate inorganic carbon in the Amazon River System is significant but not widely studied. Here we analyze samples collected at two locations on the Madre de Dios River, a tributary to the Amazon, and take measurements of total sediment load and PIC load over time. By coupling with discharge measurements, we determine the fluxes of total sediment load and POC and examine the importance of storm events. We also characterize the behavior of percent particulate inorganic carbon of river sediments, a parameter that is not usually explored, but which may be important for understanding chemical weathering processes and their role in the carbon cycle. 1

2 1. Introduction Transport of particulate carbon by mountain rivers is an important part the global carbon cycle, but the mechanics of this transport have not been fully characterized. The majority of studies on carbon transport in rivers focus on organic carbon, but much of the carbon transported by rivers is inorganic (Earth Observatory, NASA), existing as carbonate minerals dissolved in water or as carbonate mineral particles in river sediments. Whereas organic carbon is sourced from plants, soils, and fossilized organisms, inorganic carbon is eroded from sedimentary rocks and can act as a link between the fast biological carbon cycle and the slow geologic carbon cycle. Mountain rivers efficiently transport carbon-laden sediments, eventually depositing them in the ocean where carbon is fixed in limestone and other sedimentary rocks. These sedimentary rocks act as an important carbon sink for thousands of millions of years before CO2 is returned to the atmosphere in volcanic eruptions (Burdige, 2005). Because rivers carry particulate organic and inorganic carbon from multiple different sources that play different roles in the global carbon cycle, it is crucial to quantify the proportions of these different forms of carbon and understand how they mix during transport. When associated with clastic sediment particles coarser than 0.22 µm, this carbon is referred to as particulate organic and inorganic carbon (POC and PIC, respectively). Particulate inorganic carbon is often overlooked in scientific studies of river carbon transport. However, PIC contributes to outgassing of CO2 from rivers when it undergoes a hydrolysis reaction, in which solid calcium carbonate particles react with hydrogen ions to form calcium ion, water and CO2 in the following two-step reaction (Thurman, 1985): CaCO3 + 2H + -> H2CO3 + Ca 2+ -> H2O + CO2 + Ca 2+ Unlike particulate organic carbon (POC), which can act as a sink of atmospheric CO2, PIC can only act as a net source, because it is by definition being transported from a geologic carbon sink. The interface between the Andes mountain range and the Amazon River is especially important in the study of the region s carbonate geochemistry because of the high rates of erosion and nutrient transport that occur on its steep gradients. This interface, called the Andes- 2

3 Amazon Transition, is both extremely biodiverse, with more than 226 species of mammals (Upham et al., 2013), and extremely productive, with the region s rivers acting as the largest point sources of carbon to the world s oceans (Medeiros et al., 2015). Overall, the study of this region can provide valuable insights into the global biogeochemical cycles that sustain ecosystems around the world. In this study, I analyze carbon-containing suspended sediment from two locations along the Madre de Dios River and construct time-series plots of PIC and total sediment concentrations and fluxes to characterize the role of PIC in overall carbon transport by the Amazon River System. I consider samples collected on timescales of hours as well as months and examine changes in mass percent inorganic carbon of total river sediment load between the wet and dry seasons. Using discharge measurements from Ballew (2011), I examine the relationship between storm events and sediment transport to investigate the hypothesis that the vast majority of sediment transport occurs during these events. These relationships allow me to draw conclusions about the composition and behavior of inorganic carbon in the tributaries to the Amazon River, an under-researched component of a critical avenue in the global carbon cycle. 2. Review of Literature The transport of organic carbon in the Amazon river system gained attention in the mid s when Hedges et al. (1986) tracked the relative content of different forms of carbon in coarse (>63 µm) and fine (<63 µm) suspended particles over a 1,950-km reach of the lower Amazon River. Their study focused on the mixing of modern POC from different types of vascular plant tissue and tracked it by measuring % organic carbon, C/N, δ 13 C, and multiple phenolic products derived from lignin, a class of organic polymers that forms plant cell walls. By measuring these values for different Amazon plants and comparing them to values obtained from suspended sediments, Hedges and his team found that the coarse organic material was composed of 70-80% leaf tissue, 15-25% wood, and 0-10% C4 grasses by mass (Hedges et al., 1986). They were not able to precisely define the origin of fine organic material due to low yields of ligninderived content, but did show that the finer material was older and more degraded. Overall, their notable conclusions were that the composition of particulate organic material was nearly constant 3

4 over the studied length of the river and was best described as a mixture of vascular plant debris and soil humic material. More recently, riverine transport of organic carbon has been characterized at higher elevation in order to better understand the source of carbon in suspended sediments derived from Andean headwaters. Townsend-Small et al., (2008) sampled the sediment load of the Chorobamba River, approximately 1800 m above sea level in the Peruvian Andes. This study examined changes in carbon and nitrogen isotope ratios between the wet and dry seasons in addition to comparing the relative amounts of coarse and fine POC that were transported. Samples were collected weekly and at higher resolution during flood events and paired with discharge measurements, and were decarbonated and analyzed with an isotope mass spectrometer using methods that served as a model for our study. Isotopic analysis yielded δ 13 C values that were much higher in the dry season than the wet season for both fine and coarse sediments. By contrast, δ 15 N was constant over different seasons but varied with sediment grain size. These differences suggested that wet season sediments originate in mineral soils, whereas dry season sediments originate in surface soils. But Townsend-Small s most significant observation was that 81% of the total transported sediment was observed during only five storm events, suggesting that studies of suspended sediment transport must include high-resolution sampling around these flood events (Townsend-Small et al., 2008). These results showed that mountain tributaries feeding into the Amazon behave very differently from the low-elevation tributaries. Recent investigations of POC transport at the Andes-Amazon Transition have focused on the effects of factors such as slope angle, particle size, river depth, and stage height on sediment concentration and mixing of POC (Bouchez et al., 2014; Clark et al., 2014). Clark et al. (2014) examined sources of POC and their mixing at high-elevation sampling sites on the Kosñipata River in the Andes Mountains and collected samples during flood events, many of which were also considered in this study. They used analysis of carbon and nitrogen isotopes of POC sediments to determine the fractions of fossil and biospheric organic carbon. A linear relationship between δ 13 Corg and N/C showed a binary mixture between fossil and biospheric carbon, so they were able to use a two-component mixing model and found that fossil POC 4

5 consistently contributed 80% of total POC, much higher than previous estimates, while input of biospheric POC varied with time. Bouchez et al., (2014) used similar methods to quantify fossil and biospheric POC mixing in the Solimoes and Madeira Rivers, as well as the Amazon at Obidos, while also testing for age of organic carbon and variations in POC composition across depth. They found much smaller proportions of fossil POC in these rivers, ranging from 5-10% of total POC flux in all rivers samples. However, none of these studies also considered the transport of particulate inorganic carbon. But this year, Torres et al. (2016) examined the CO2 budget of the Madre de Dios River by comparing rates of alkalinity-producing carbonate (and silicate) mineral dissolution versus rates of acid-producing sulfide mineral oxidation. Torres found that lower in the Amazon, samples showed high proportions of carbonate weathering, implying that CO2 is consumed at these sites. At a higher-elevation site near the front of the Andes, higher proportions of sulfuric acid weathering indicated that weathering occurring there does not result in changes in net CO2 fluxes. This paper showed the geochemical changes along elevation gradients and the importance of inorganic carbon weathering. 3. Methods 3.1. Sample Collection Suspended sediment samples were collected by Kathryn Clark at the same two stations that were examined in Torres et al. (2016), one at the front of the Peruvian Andes and one in the Foreland floodplain region (see Torres et al., 2015 for description of study sites). Mountain-Front samples were collected at the Manu Learning Center (MLC), with a mean catchment elevation of 2,012 m and catchment area of 6,025 km 2. Foreland floodplain samples were collected at the CICRA research station, with a mean catchment elevation of 822 m and catchment area of 27,830 km 2. By sampling from a higher-elevation site underlain by plutonic, sedimentary, and metasedimentary rocks as well as a lower site underlain by marine sediments, we are able to explore the behavior of suspended carbonate sediments across the Andes-Amazon Transition. Samples were collected at approximately two-week time intervals from January 2010 through December 2011, spanning the wet seasons (January through early April) and dry seasons (mid-april through December) of 2010 and Additionally, samples were collected at three- 5

6 hour time intervals over two weeks in the 2010 wet season during a period of frequent flood events. Collection of samples during flood events ensured that a significant amount of sediment transfer was occurring, and allowed us to observe changes in sediment composition over short timescales. To obtain samples, a pole was used to reach the surface of the stream at its center, and a measured volume of river water was filtered through 0.7-µm glass fiber filters, which were then dried at ~40 C to obtain the suspended river sediment. Because the rough riverbed causes turbulent flow and mixing at the MLC site, samples taken at the surface should reflect the composition at depth at that site (Clark et al., 2013), but may reflect some bias at the foreland site, where sediment may be more fractionated with depth. Samples were chosen for gravimetric and hydrodynamic analysis to facilitate investigation of sediment composition and transport over timescales of hours, days, and months. Thus approximately half of the samples chosen for analysis were collected over a two-week period in early February 2010 while half were collected at approximately one-month intervals from March 2010 through November Location, stage height, date and time of collection, and volume of water filtered were measured for each sample Decarbonation In the lab, samples were washed off of their respective filters with DI water, dried overnight at 50 C, and weighed. Inorganic carbon was then removed from the samples via liquid-phase decarbonation, during which samples were immersed in a 5 M HCl leach for four hours at 75 C. The samples were then rinsed with DI water three times, dried, and weighed again in order to determine the difference between the decarbonated and non-decarbonated weight of each sample. Decarbonated samples, composed of petrogenic and biospheric organic carbon and silicate clasts, were homogenized with a mortar and pestle for future isotope analysis Gravimetric analysis The pre-decarbonation sample masses were used to determine suspended sediment concentrations (SSC, mg L -1 ) by dividing the sample mass by the volume of river water filtered to obtain each sample. Suspended sediment concentration is used to characterize the Madre de Dios River s capacity for sediment transport. We multiplied SSC at each point in time by discharge (m 3 sec -1, calculated by Ballew 2011) to obtain total sediment flux (g s -1 ), and 6

7 converted to kg s -1. When observed in a time series, sediment flux can be integrated to find total mass of material transported and to test the proposed hypothesis that the majority of sediment transport by mountain rivers occurs during few scattered flood events. Because liquid-phase decarbonation is meant to remove only inorganic carbon from a sample, we were able to find the mass of inorganic carbon in each sample by subtracting the post-decarbonation mass from the pre-decarbonation mass. Mass of inorganic carbon was divided by volume filtered to obtain PIC concentration, which was observed at each station over time. We also multiplied PIC concentration by discharge to obtain PIC flux (kg s -1 ). Lastly, we divided the pre-decarbonation sample masses by the decarbonated masses to find the percent particulate inorganic carbon in each sample. Quantifying the amount of PIC in sediments can complement biospheric and petrogenic organic carbon ratios in characterizing the composition of river particulate carbon. 4. Results 4.1. Suspended Sediment Concentration Total suspended sediment concentration (SSC) showed high variability across timescales of both days and months. At MLC during the period of high-resolution sampling from January 31 st, 2010 to February 3 rd, 2010, suspended sediment concentration ranged from 178 mg/l to 2,218 mg/l. The mean of the data was 735 mg/l (n = 20) with a standard error of 134 mg/l (figure 1a). At CICRA, the period of high-resolution sampling from February 3 rd, 2010 to February 11 th, 2010 yielded suspended sediment concentrations ranging from 134 mg/l to 1,740 a.) mg/l. The mean of these data was 649 mg/l (n = 39) with standard error of 64 mg/l (figure 1b). b.) Figure 1: Suspended sediment concentration and river discharge a.) at MLC from 01/31/10 to 02/03/10, and b.) at CICRA from 02/03/10 to 02/12/10 7

8 a.) The overall increase in SSC values at MLC marks the rising limb of a storm event in which runoff from the area s steep terrain results in an increase in river discharge and SSC. The decrease in the concentration values at CICRA corresponds to the falling limb of that storm during which discharge and SSC return to normal. During storm events, SSC also shows wider variation over time. At MLC during the period of low-resolution sampling from January 31 st, 2010 to May 6 th, 2011, suspended sediment concentration ranged from 3 mg/l to 1,089 mg/l. The mean of the data was 372 mg/l (n = 21) with a standard error of 81 mg/l (figure 2a). At CICRA, the period of low-resolution sampling from January 29 th, 2010 to December 27 th, 2010 yielded suspended sediment concentrations ranging from 51 mg/l to 1077 mg/l. The mean of these data was 482 mg/l (n = 18) with a standard error of 81 mg/l (figure 2b). b.) Figure 2: Suspended sediment concentration a.) at MLC from 01/31/10 to 05/10/11, and b.) at CICRA from 01/29/10 to 12/31/10 8

9 a.) The low SSC values occurring from April 2010 to December 2010 correspond to the area s dry season, during which low runoff results in low discharge and SSC. Data from CICRA for this period was not available, but would most likely show a similar trend Particulate Inorganic Carbon Concentration PIC concentration over time behaved very similarly to total SSC. At MLC during the period of high-resolution sampling from January 31 st, 2010 to February 3 rd, 2010, PIC concentration ranged from 23 mg/l to 142 mg/l. The mean of the data was 68 mg/l (n = 20) with a standard error of 9 mg/l (figure 3a). At CICRA, the period of high-resolution sampling from February 3 rd, 2010 to February 11 th, 2010 yielded suspended sediment concentrations ranging from 2 mg/l to mg/l. The mean of these data was 55 mg/l (n = 37) with a standard error of 5 mg/l (figure 3b). b.) Figure 3: Particulate inorganic carbon concentration and river discharge a.) at MLC from 01/31/10 to 02/03/10, and b.) at CICRA from 02/03/10 to 02/12/10 At MLC during the period of low-resolution sampling from January 31 st, 2010 to May 6 th, 2011, PIC concentration ranged from 0.64 mg/l to 99 mg/l. The mean of the data was 34 mg/l (n = 21) with a standard error of 7 mg/l (figure 4a). At CICRA, the period of lowresolution sampling from January 29 th, 2010 to December 27 th, 2010 yielded suspended sediment concentrations ranging from 5 mg/l to 88 mg/l. The mean of these data was 35 mg/l (n = 18) with a standard error of 6 mg/l (figure 4b). 9

10 a.) b.) Figure 4: Particulate inorganic carbon concentration a.) at MLC from 01/31/10 to 05/10/11, and b.) at CICRA from 01/29/10 to 12/31/ Mass Percent inorganic Carbon The mass percent inorganic carbon of suspended sediments was generally higher at MLC than at CICRA. At MLC during the period of high-resolution sampling from January 31 st, 2010 to February 3 rd, 2010, percent PIC of sediments ranged from 5.8% to 18.6%. The mean was 11.0% (n = 20) with a standard error of 0.6%. (figure 5a). At CICRA, percent PIC calculated for samples taken during the high-resolution sampling period from February 3 rd, 2010 to February 11 th, 2010 ranged from 0.74% to 13.3%. The mean of these values was 8.0% (n = 37) with a standard error of 0.4% (figure 5b). 10

11 a.) b.) Figure 5: Percent particulate organic carbon and river discharge a.) at MLC from 01/31/10 to 02/03/10, and b.) at CICRA from 02/03/10 to 02/12/10 Unlike suspended sediment and PIC concentration, percent PIC shows opposite variation with respect to discharge at MLC versus CICRA, increasing during the storm event at CICRA and decreasing during the storm event at MLC. This discrepancy is explored further in the discussion. At MLC during the period of low-resolution sampling from January 31 st, 2010 to May 6 th, 2011, percent PIC ranged from 2.7% to 19.0%. The mean of the data was 10.4% (n=21) with a standard error of 0.79% (figure 6a). The percent PIC of samples collected at CICRA during the low-resolution sampling period from January 29 th, 2010 to December 27 th, 2010 were again generally lower than the values at MLC, ranging from 2.1% to 9.9%. The mean value was 7.5% (n = 18) with a standard error of 0.6% (figure 6b). 11

12 a.) b.) Figure 6: Percent particulate inorganic carbon a.) at MLC from 01/31/10 to 05/10/11, and b.) at CICRA from 01/29/10 to 12/31/10 Percent PIC in sediments collected at MLC shows an overall increase from April 2010 through September 2010, corresponding to the end of the wet season and the majority of the dry season. This is in agreement with the observed decrease during flood events, suggesting that discharge and percent PIC are inversely proportional. However, it is not clear why percent PIC decreases during the last three months of the dry season Sediment Flux Total sediment flux showed very different behaviors and ranges of values across the two sampled locations and timescales. Computed for samples collected at MLC at high temporal resolution, sediment flux ranged from 85 kg/sec to 1,278 kg/sec. The mean flux was 384 kg/sec 12

13 (n = 20) with a standard error of 81 kg/sec (figure 7a). Sediment flux computed for samples collected at CICRA at high resolution ranged from 238 kg/sec to 4108 kg/sec. The mean of these a.) values was 1,382 kg/sec (n = 37) with a standard error of 159 kg/sec (figure 7b). b.) Discharge values were not included on plots of sediment flux because flux is directly proportional to discharge and sediment concentration. As the product of two values that sharply increase during storm events, sediment flux will generally increase exponentially in storm events. Figure 7: Total sediment flux a.) at MLC from 01/31/10 to 02/03/10, and b.) at CICRA from 02/03/10 to 02/12/10 During the period of low-resolution sampling, sediment flux for samples collected at MLC ranged from 0.7 kg/sec to 673 kg/sec. The mean flux was 177 kg/sec (n=21) with a standard error of 48 kg/sec (figure 8a). At CICRA, sediment flux ranged from 69 kg/sec to 2,567 kg/sec. The mean value was 854 kg/sec (n = 18) with a standard error of 173 kg/sec (figure 8b). 13

14 a.) b.) 5.5. PIC Flux Particulate inorganic carbon flux exhibited relatively consistent means and ranges within sampling sites, and differed by a factor of approximately 3.5 between sites. Computed for samples collected at MLC at high temporal resolution, sediment flux ranged from 10 kg/sec to 77 kg/sec. The mean flux was 35 kg/sec (n = 20) with a standard error of 5 kg/sec (figure 9a). Sediment flux computed for samples collected at CICRA at high resolution ranged from 4 kg/sec to 280 kg/sec. The mean of these values was 118 kg/sec (n = 37) with a standard error of 13 kg/sec (figure 9b). Figure 8: Total sediment flux a.) at MLC from 01/31/10 to 05/10/11, and b.) at CICRA from 01/29/10 to 12/31/10 14

15 a.) b.) a.) Figure 9: Particulate inorganic carbon flux a.) at MLC from 01/31/10 to 02/03/10, and b.) at CICRA from 02/03/10 to 02/12/10 During the period of low-resolution sampling, PIC flux for samples collected at MLC ranged from 0.1 kg/sec to 59 kg/sec. The mean flux was 16 kg/sec (n=21) with a standard error of 4 kg/sec (figure 10a). At CICRA, sediment flux ranged from 6 kg/sec to 209 kg/sec. The mean value was 65 kg/sec (n = 18) with a standard error of 15 kg/sec (figure 10b). 15

16 b.) 6. Discussion 6.1. Trends in Sediment and PIC Concentration Many of the time-series results were in agreement with previous research on sediment transport in the Andes-Amazon region. Increases in river discharge were correlated with increases in suspended sediment and PIC concentrations during short flooding events, which has been demonstrated by Townsend-Small et al (2008) and Clark et al (2013). Average SSC at MLC increased from 305 mg L -1 (n = 7, standard error 34 mg L -1 ) before the storm event to 1260 mg L -1 (n =9, standard error = 176) immediately after the peak, and average SSC at CICRA was recorded during the falling limb of the storm as it decreased from 852 mg L -1 (n = 23, standard error = 77 mg L -1 ) directly after the peak to 356 mg L -1 (n = 16, standard error = 53 mg L -1 ) three days later. Figure 10: Particulate inorganic carbon flux a.) at MLC from 01/31/10 to 05/10/11, and b.) at CICRA from 01/29/10 to 12/31/10 At both sites, discharge was approximately 1.5 times greater during storm events, but at MLC, average SSC increased by a factor of 4.1 during the storm event, whereas at CICRA it decreased by a factor of only 2.4 after the storm event. Though it is probable that dilution in SSC after a storm event is more gradual than the SSC increase from sudden inputs, SSC measured five days after the storm event had still only decreased by a factor of 2.5. A more probable explanation is that the MLC catchment s steeper slope angle (22 versus 9 at CICRA) and 16

17 sparser vegetation at high elevation make it extremely conducive to runoff, which is likely to carry fossil organic carbon, inorganic carbon, and other clastic particles weathered from exposed rock. Thus a storm event of similar magnitude would result in greater sediment input at MLC than at CICRA. Additionally, average discharge is lower at MLC than at CICRA by a factor of 4.4 during the wet season, so the same mass of sediment input will have a much greater effect on concentration Factors Affecting Percent PIC Variations in mass percent inorganic carbon of suspended sediments at MLC and CICRA showed the unusual behavior of PIC and the importance of storm events for its transport. Because percent PIC is inversely proportional to total sediment load, it is often negatively correlated with changes in discharge and total PIC concentration. Figure 11 shows changes in percent PIC, PIC concentration, suspended sediment concentration, and discharge measured at MLC. During the rising limb of the profiled storm event, percent PIC increases while PIC and suspended sediment concentrations decrease due to dilution. Whereas PIC and suspended sediments increase rapidly during the falling limb of the storm, percent PIC falls to 7.8%, well below its average value. Figure 11: Variations in percent PIC opposite of variation in PIC concentration and suspended sediment concentration surrounding a storm event at MLC 17

18 As percent PIC of sediments decreases at MLC, it exhibits opposite behavior at CICRA, increasing from 5.7% to 11.8% with the peak and falling limb of the storm event. Percent PIC increases even as total suspended sediment concentration increases, meaning that large amounts of PIC are being incorporated into the sediment load. Because the lowland floodplain at CICRA lacks exposed sedimentary rocks, the additional PIC must have originated at higher elevation near MLC. Thus PIC displays opposite behavior at CICRA and MLC because it is transported downstream more quickly than it is weathered during storm events, resulting in a net decrease at MLC and a net increase at CICRA. Percent PIC also shows variation opposite of suspended sediment and PIC concentration in samples collected during the dry season, from mid-april through December. Low-resolution measurements from January 2010 through March 2011 at MLC show that percent PIC reaches peak values in July and September, comprising 18% of total suspended sediment when measured in July and 19% when measured in September. Monthly variations in PIC and total suspended sediment at CICRA could not be analyzed due to a lack of data for March through August. Although concentration of PIC is low during the dry season (MLC average = 14 mg/l), total organic carbon concentration is also low enough that the proportion of PIC reaches its highest values in the year. Sediment concentrations in these months are low but not negligible, and particulate inorganic carbon can have significant contributions to carbon outgassing (England et al., 2011). 7. Conclusion The results of our high-resolution time-series measurements confirms the importance of storm events for sediment and carbon transfer in the Amazon River system. We also explored percent PIC as a useful characteristic of sediment load that provides a new perspective on its behavior. Although we calculated PIC flux over the course of the year, we were unable to reliably use this value to obtain total yearly PIC transport in kilograms because the yearly data was not high-resolution enough. For future studies, we would obtain more robust yearly data from both study sites, in addition to supplementing PIC and total sediment masses with isotope data to find proportions of 18

19 fossil and biospheric POC in order to fully characterize the particulate carbon composition. Over a time series, this could yield even more important insights about the river s behavior. Our aim is for this paper to motivate future studies of the region and its rivers to include behavior and effects of PIC transport, as we have shown that the percent of PIC transported during flood events throughout the year is significant and should not be discounted. Thus we can move one step closer to fully understanding this important system in the global carbon cycle. Acknowledgements I would first like to thank Dr. Josh West for advising me on the direction, science, and logistics this project, and for helping revise and edit drafts. I would also like to thank Dr. Kathryn Clark for collecting the sediment samples in the field, and Joyce Yager and Ellie Hara for assisting with the decarbonation process. 19

20 Data Tables MLC, High Resolution Date Time SSC (mg/l) PIC concentration (mg/l) % PIC Discharge (m^3/sec) Sediment flux (kg/s) PIC flux (kg/s) 1/31/2010 9:00 AM /31/ :00 PM /31/2010 6:00 PM /31/2010 9:00 PM /1/2010 3:00 AM /1/2010 6:00 AM /1/ :00 PM /1/2010 3:00 PM /1/2010 9:00 AM /2/ :00 AM /3/2010 3:00 AM /4/2010 6:00 AM , /5/2010 9:00 AM , /6/ :00 PM /7/2010 3:00 PM /8/2010 6:00 PM /9/2010 9:00 PM /3/ :00 AM /3/2010 3:00 AM /3/2010 6:00 AM MLC, Low Resolution Date SSC (mg/l) PIC concentration (mg/l) % PIC Discharge (m^3/sec) Sediment flux (kg/s) PIC flux (kg/s) 1/31/ /1/ /2/ /3/ /10/ /15/ /29/ /26/ /17/ /24/ /26/

21 7/30/ /31/ /13/ /15/ /13/ /24/ /7/ /7/ , /4/ n.d /3/ n.d. - - CICRA, High Resolution Date Time SSC (mg/l) PIC concentration (mg/l) % PIC Discharge (m^3/sec) Sediment flux (kg/s) PIC flux (kg/s) 2/3/2010 6:00 PM /3/2010 9:00 PM /4/ :00 AM /4/2010 3:00 AM /4/2010 6:00 AM /4/2010 9:00 AM /4/ :00 PM /4/2010 3:00 PM /4/2010 6:00 PM /4/2010 9:00 PM /5/ :00 AM /5/2010 3:00 AM /5/2010 6:00 AM /5/ :00 PM /5/2010 3:00 PM /5/2010 6:00 PM /5/2010 9:00 PM /6/ :00 AM /6/2010 3:00 AM /6/2010 6:00 AM /6/2010 9:00 AM /6/ :00 PM /6/2010 3:00 PM /9/2010 3:00 PM /9/2010 6:00 PM n.d /10/ :00 AM /10/2010 3:00 AM

22 2/10/2010 6:00 AM n.d /10/2010 9:00 AM /10/ :00 PM /10/2010 3:00 PM /10/2010 6:00 PM /11/ :00 AM /11/2010 3:00 AM /11/2010 6:00 AM /11/2010 9:00 AM /11/ :00 PM /11/2010 3:00 PM /11/2010 6:00 PM CICRA, Low Resolution Date SSC (mg/l) PIC concentration (mg/l) % PIC Discharge (m^3/sec) Sediment flux (kg/s) PIC flux (kg/s) 1/29/ /31/ , /1/ , /3/ /4/ /5/ /6/ /9/ /10/ /11/ /21/ /27/ /19/ /8/ , /22/ , /27/ ,

23 References Ballew, Natalie. "Quantifying Discharge in the Kosñipata-Madre De Dios River System, Peru." (2011): n. pag. Web. Bouchez, Julien, Valier Galy, Robert G. Hilton, Jérôme Gaillardet, Patricia Moreira-Turcq, Marcela Andrea Pérez, Christian France-Lanord, and Laurence Maurice. "Source, Transport and Fluxes of Amazon River Particulate Organic Carbon: Insights from River Sediment Depth-profiles." Geochimica Et Cosmochimica Acta 133 (2014): Web. Burdige, David J. Burial of Terrestrial Organic Matter in Marine Sediments: A Re- Assessment. Global Biogeochemical Cycles 19.4 (2005): n/a n/a. Web. Riebeek, Holli. The carbon cycle: Feature articles. NASA Earth Observatory, 16 June Web. Clark, K. E., R. G. Hilton, A. J. West, Y. Malhi, D. R. Gröcke, C. L. Bryant, P. L. Ascough, A. Robles Caceres, and M. New. "New Views on old Carbon in the Amazon River: Insight from the Source of Organic Carbon Eroded from the Peruvian Andes." Geochemistry, Geophysics, Geosystems Geochem. Geophys. Geosyst (2013): Web. Hedges, John I., Wayne A. Clark, Paul D. Quay, Jeffrey E. Richey, Allan H. Devol, and Umberto De M. Santos. "Compositions and Fluxes of Particulate Organic Material in the Amazon River." Limnol. Oceangr. Limnology and Oceanography31.4 (1986): Web. Medeiros, Patricia M., Michael Seidel, Nicholas D. Ward, Edward J. Carpenter, Helga R. Gomes, Jutta Niggemann, Alex V. Krusche, Jeffrey E. Richey, Patricia L. Yager, and Thorsten Dittmar. "Fate of the Amazon River Dissolved Organic Matter in the Tropical Atlantic Ocean." Global Biogeochem. Cycles Global Biogeochemical Cycles 29.5 (2015): Web. Thurman, E. M. Organic Geochemistry of Natural Waters. Dordrecht: M. Nijhoff, Print. Torres, Mark A., A. Joshua West, Kathryn E. Clark, Guillame Paris, Julian Bouchez, Camilo Ponton, and Sarah J. Feakins. "The Acid and Alkalinity Budgets of Weathering in the Andes Amazon 78 System: Insights into the Erosional Control of Global 23

24 Biogeochemical Cycles?" Earth and Planetary Science Letters (2016): n. pag. Web. Townsend-Small, Amy, Michael E. Mcclain, Bonnie Hall, Jorge L. Noguera, Carlos A. Llerena, and Jay A. Brandes. "Suspended Sediments and Organic Matter in Mountain Headwaters of the Amazon River: Results from a 1-year Time Series Study in the Central Peruvian Andes." Geochimica Et Cosmochimica Acta 72.3 (2008): Web. Upham, Nathan S., Reed Ojala-Barbour, Jorge Brito M, Paúl M. Velazco, and Bruce D. Patterson. "Transitions between Andean and Amazonian Centers of Endemism in the Radiation of Some Arboreal Rodents." BMC Evol Biol BMC Evolutionary Biology 13.1 (2013): 191. Web. 24