Challenges in measuring CO2 dissolved in water

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1 耶鲁大学 - 南京信息工程大学大气环境中心 Yale-NUIST Center on Atmospheric Environment Challenges in measuring CO2 dissolved in water Qitao Xiao Video conference of YNCenter

2 uoutline l 1 Background l 2 Experience about measuring CO2 concentration dissolved in water l 3 Method 2

3 u1 Background l The global C cycle of lake in diverse lakes (by applying the active pipe concept) DIC : dissolved inorganic carbon DOC : dissolved organic carbon POC : particulate organic carbon TOC : total organic carbon 3 Lars J. Tranvik et al Limnol. Oceanogr

4 l The produce of CO2 in lake water 4 Schrier-Uijl et al Biogeochemistry

5 l The factor affect the CO2 concentration dissolved in water (1) the decomposition of sediment (2) microbial activity (3) respiration and photosynthesis of aquatic plants (4) the input of allochthonous carbon l CO2 is produced by respiration throughout lakes and lake sediments. (PETER CASPER et al Biogeochemistry) 5

6 l The most challenge is how to control the microbial activity when measure CO2 concentration dissolved in Lake Taihu. (1) The biomss in water samlpes is rich. (2) The water samples couldn t be sent to lab for analysis immediately. 6

7 lsample site and water sample Sample of spatial phytoplankton zooplankton contain Sample of daily organic matter cyanobacteria Microbial activity will have a great impact on the water sample if not analyzed immediately. 7

8 u2 Experience about measuring CO2 concentration dissolved in water l Add copper sulfate CuSO4) in water sample to control the microbial activity. Some sediment will arise in water sample after adding 5ml CuSO4(2%), and it show that CuSO4 can eliminate the impact of microbial activity. However the CO2 concentration that measured by water equilibrium method is very high when add CuSO4 in water sample. Whether CuSO4 can increase CO2 concentration,and if so, what about other sterilization, for example HgCl2 CuCl2 and so on 8

9 lexperiment scheme to confirm the impact of sterilization 3 6 A1 A2 A3 analyzed immediately after 5 minutes of shaking Group A (hollow) A4 A5 A6: after 5 minutes of 3 Shaking, waited 2 days to analyze 3 B1 B2 B3 analyzed immediately after 5 minutes of shaking 6 Group B (1ml CuSO4) 3 Water 24 sample 3 6 Group C (5ml CuSO4) B4 B5 B6: after 5 minutes of Shaking, waited 2 days to analyze C1 C2 C3 analyzed immediately after 5 minutes of shaking C4 C5 C6: after 5 minutes of Shaking, waited 2 days to analyze D1 D2 D3 analyzed immediately after 5 minutes of shaking Group D(0.5ml HgCl2) 3 D4 D5 D6: after 5 minutes of Shaking, waited 2 days to analyze 9

10 lthe result CO2 concentration at different treatment 1050 CO2(μmol/L) 900 A: hollow B: 1ml CuSO4 C: 5ml CuSO4 D: 0.5ml HgCl A1 A2 A3 B1 B2 B3 C1 C2 C3 D1 D2 D Analyzed immediately after shaking 5 minutes 1200 CO2(μmol/L) Wait 2 days to analyzed after shaking 5minutes A4 10 A5 A6 B4 B5 B6 C4 C5 C6 D4 D5 D6

11 lcorrelation: CO2 concentration and alkalinity y= x R2 = y= x R2 = Alkalinity (mg CaCO3 /L) 11 alkalinity analyzed by James data from analyzed immediately data from analyzed after waiting 2 days

12 lthe equilibria about alkalinity and CO2 concentration Alk = total alkalinity, as p. p. m. of CaCO3 (H+) = hydrogen-ion concentration, moles per liter A. A. HIRSCH et al. Journal of the American Chemistry Annual Meeting l Calculate the dissolved CO2 concentration using alkalinity and ph data and compared the calculated values with the values measured by GC next step. 12

13 Journal of the American Chemistry Annual Meeting 13

14 u3 Method l 1. Don t add any sterilization, and analysis water samples as soon as possible when they are sent to lab. sample underwater 20cm 14 save analysis

15 l 2. Gas pocket The gas to be analyzed can be transfer from water sample to gas pocket once sample and pretreatment completed. Its air tightness can be checked by whether make it vacuum. water sample gas pocket transfer 15

16 l Some questions about gas pocket when use it measure GHGs concentration. (1) whether it will break the balance between gas and liquid when transfer gas from sample to gas pocket, then promote the water emission gas. (2) whether the gas pocket can save the gas for a period of time. 16

17 l 3.Compare the data: bottle Vs gas pocket 60 CO2(μmol/L) tap water A1 A2 A3 measured by bottle A4 A5 A6 measured by gas pocket 15 0 A1 A2 CO2 μmol/l) 400 A3 A4 A5 A6 B1 B2 B3 measured by bottle river water B4 B5 B6 measured by gas pocket B1 17 B2 B3 B4 B5 B6

18 lthe data of water sample measured by bottle and gas pocket respectively 52 CO2(μmol/L) tap water 48 bottle gas pocket A1 A2 A3 340 CO2(μmol/L) river water bottle gas pocket B1 B2 B3

19 l 4. Make a choice measure dissolve CO2 concentration water sample save fridge treat «wait target gas analysis GC Vs water sample treat target gas Vs Alkalinity CO2 19 save gas pocket analysis «wait GC

20 耶鲁大学 - 南京信息工程大学大气环境中心 Yale-NUIST Center on Atmospheric Environment 20

N 2 O concentration and flux in Lake Taihu

耶鲁大学 - 南京信息工程大学大气环境中心 Yale-NUIST Center on Atmospheric Environment N 2 O concentration and flux in Lake Taihu Qitao Xiao 2016.11.18 1 Outline 2 1. Background 2. Objective 3. Material and Method 4. Results