$CO_2$ 和 $CH_4$ 溶存浓度/分压

基础知识

DIC

溶解无机碳（dissolved inorganic carbon, DIC）组成是 $CO_2(eq)$ 、 $H_2CO_3$ 、 $CO_3^{2-}$ 和 $HCO_3^-$

\[[DIC] = [CO_3^{2-}] + [HCO_3^-] +[H_2CO_3]+[CO_2]\]

碱度Alkalinity

总碱度total alkalinity

\[TA= [HCO_3^-]+2[CO_3^{2-}] +[OH^-] - [H^+]\]

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

\[c_w = K_HP\]

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

$CO_2$ 溶解

\[pK_{CO_2} = -7 \times 10^{-5}T^2 +0.016T +1.11\] \[pK_1 = 1.1 \times 10^{-4}T^2 -0.012T +6.58\] \[pK_2 = 9 \times 10^{-5}T^2 -0.0137T +10.62\]

calculation

$pCO_2$ 水化学平衡法

\(pCO_2 = \frac{[HCO_3^-] [H^+]}{K_{CO_2}K_1}\)

methane AND carbon dioxide

顶空平衡法 pCO2

\[C_W = C_1RTK_H + ( C_0-C_1 ) \frac{V_0}{V_1}\]

包括顶空平衡法计算过程¹

$K_0$的计算方法²

\[ln K_0 = A_1 + A_2 \frac{100}{T} + A_3 ln \frac{T}{100}\]

$pCO_2$的计算³

甲烷溶存浓度计算

⁴ 溶解甲烷浓度 dCH4

\[ln\beta =A_1+A_2(100/T)+A_3ln(T/100)+S(B_1+B_2(T/100)+B_3(T/100)^2)\]

(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}

\[pGas = \frac{(p_{Final}*K_{0Equilibrium})+HS/S (p_{final}-p_{initial})/V_m}{K_{0sample}}\] \[lnK_{CO_2} = -58.0931+90.5069 \frac{100}{T_K}+ 22.294 ln \frac{T_K}{100}\] \[lnK_{CH_4} = -115.6477+\frac{155.5756}{T_K/100} +65.2553ln\frac{T_K}{100}- 6.1698 \frac{T_K}{100}\] \[ln\beta = -68.8862+101.4956 \frac{100}{T_K}+ 28.7314 ln \frac{T_K}{100}\] \[K_{CH_4} = \beta /22.4\]

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