$C O_{2}$ 和 $C H_{4}$ 溶存浓度/分压

Posted Dec 4, 2024 Updated Dec 18, 2024

By culleus

2 min read

C O_{2}

和

C H_{4}

溶存浓度/分压

基础知识

DIC

溶解无机碳（dissolved inorganic carbon, DIC）组成是 $C O_{2} (e q)$ 、 $H_{2} C O_{3}$ 、 $C O_{3}^{2 -}$ 和 $H C O_{3}^{-}$

[D I C] = [C O_{3}^{2 -}] + [H C O_{3}^{-}] + [H_{2} C O_{3}] + [C O_{2}]

碱度Alkalinity

总碱度total alkalinity

T A = [H C O_{3}^{-}] + 2 [C O_{3}^{2 -}] + [O H^{-}] - [H^{+}]

Henry’s law

亨利定律：在一定温度平衡下，一种气体在液体里的溶解度与该气体的平衡压力成正比

c_{w} = K_{H} P

其中 $c_{w}$ 气体在水中平衡浓度， mol/L

$K_{H}$ 亨利定律常数， mol/(L·atm)

$p$ 气体在大气中的平衡分压， Pa 或 atm

亨利常数 $K_{H}$

亨利常数与温度和盐度有关，一般认为淡水中盐度为0

$C O_{2}$ 溶解

p K_{C O_{2}} = - 7 \times 10^{- 5} T^{2} + 0.016 T + 1.11

p K_{1} = 1.1 \times 10^{- 4} T^{2} - 0.012 T + 6.58

p K_{2} = 9 \times 10^{- 5} T^{2} - 0.0137 T + 10.62

calculation

$p C O_{2}$ 水化学平衡法

$p C O_{2} = \frac{[H C O_{3}^{-}] [H^{+}]}{K_{C O_{2}} K_{1}}$

methane AND carbon dioxide

顶空平衡法 pCO2

C_{W} = C_{1} R T K_{H} + (C_{0} - C_{1}) \frac{V_{0}}{V_{1}}

包括顶空平衡法计算过程¹

$K_{0}$ 的计算方法²

l n K_{0} = A_{1} + A_{2} \frac{100}{T} + A_{3} l n \frac{T}{100}

$p C O_{2}$ 的计算³

甲烷溶存浓度计算

⁴ 溶解甲烷浓度 dCH4

l n β = A_{1} + A_{2} (100 / T) + A_{3} l n (T / 100) + S (B_{1} + B_{2} (T / 100) + B_{3} (T / 100)^{2})

(Weiss 1970)⁵ 给出以上公式以及 $N_{2}$ $O_{2}$ Ar 的参数A B

(Weiss 1974)⁶

calculation pGas

⁷ ⁸

p G a s = \frac{(p_{F i n a l} * K_{0 E q u i l i b r i u m}) + H S / S (p_{f i n a l} - p_{i n i t i a l}) / V_{m}}{K_{0 s a m p l e}}

l n K_{C O_{2}} = - 58.0931 + 90.5069 \frac{100}{T_{K}} + 22.294 l n \frac{T_{K}}{100}

l n K_{C H_{4}} = - 115.6477 + \frac{155.5756}{T_{K} / 100} + 65.2553 l n \frac{T_{K}}{100} - 6.1698 \frac{T_{K}}{100}

l n β = - 68.8862 + 101.4956 \frac{100}{T_{K}} + 28.7314 l n \frac{T_{K}}{100}

K_{C H_{4}} = β / 22.4

李航,王晓锋,袁兴中等.淡水生态系统温室气体通量检测方法综述[J].湖泊化学,2023,35(04):1153-1175. http://www.jlakes.org/html/2023/4/20230402.html#outline_anchor_30 ↩︎
Weiss R F. Carbon dioxide in water and seawater: the solubility of a non-ideal gas[J]. Marine chemistry, 1974, 2(3): 203-215.DOI:https://doi.org/10.1016/0304-4203(74)90015-2 ↩︎
Koschorreck M, Prairie Y T, Kim J, et al. CO2 is not like CH4–limits of and corrections to the headspace method to analyse pCO2 in fresh water[J]. Biogeosciences, 2021, 18(5): 1619-1627.DOI: https://doi.org/10.5194/bg-18-1619-2021 ↩︎
Johnson K M, Hughes J E, Donaghay P L, et al. Bottle-calibration static head space method for the determination of methane dissolved in seawater[J]. Analytical Chemistry, 1990, 62(21): 2408-2412. ↩︎
Weiss R F. The solubility of nitrogen, oxygen and argon in water and seawater[C]//Deep sea research and oceanographic abstracts. Elsevier, 1970, 17(4): 721-735. ↩︎
Weiss R F. Carbon dioxide in water and seawater: the solubility of a non-ideal gas[J]. Marine chemistry, 1974, 2(3): 203-215. ↩︎
Goldenfum, J. A. GHG Measurement Guidelines for Freshwater Reservoirs: Derived From: the UNESCO/IHA Greenhouse Gas Emissions from Freshwater Reservoirs Research Project (International Hydropower Association (IHA), 2010). ↩︎
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科研

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