In the carbonate rock-dominated regions, like Taihu Lake, carbonate weathering
played an important role in the neutralization processes (Yu et al. 2016b). The
surface water had high ANC because the carbonates in soil (even with low contents)
can buffer efficiently the acid input to the watershed (Hu et al. 1982). The release of
base cations by chemical weathering in the soil plays an important role in neutralization of acid in some upland lakes in southwest China (Xue and Schnoor 1994).
The subtropical forests in China have hot and humid monsoon climate (Kong et al.
1997). The forest soil is dominated by highly weathered red or yellow earth (Matson
et al. 1999), with low pH (<4.2) and BS (<10%) (Lu et al. 2015; Yan et al. 2015;
Huang et al. 2015), and experienced elevated acid deposition for more than two
decades. Dissolution of aluminosilicates buffers the H
+ input in South China due to
the low soil pH and results in high Al
3+ concentration in the soil water (Lassen et al.
2011; Yu et al. 2017c). The Al mobilization could buffer one-third of acidity input in
the NH 4 NO 3 -treated plot at Tieshanping in Chongqing (Huang et al. 2015).
The soil chemical weathering varies in different regions. In southeastern China
and large region in southwestern China, the Haplic Acrisol has a relatively low
weathering rate. The soil type in west part of southwestern China is dominated by
Haplic Luvisol, showing a higher weathering rate (Duan et al. 2002). The Haplic
Podzol and Albic Luvisol in northeast China developed from granite, having
extremely low weathering rate (Duan et al. 2002).
8.5.2 Buffering by Base Cation Deposition
The precipitation pH in China was not very low, even under elevated S and N
deposition, because of the high buffering by alkali, including base cations in
anthropogenic particulate matter (PM) (Zhu et al. 2004; Lei et al. 2011) and soil
dust (Larssen and Carmichael 2000), as well as NH 4
+ coming from NH 3 emission
from agricultural activities (Kang et al. 2016). The precipitations have higher BC
concentration in northern China than those in southern China or other industrial
nations (Wang and Wang 1996; Cao et al. 2013; Wang et al. 2012a). Therefore, the
soil-derived bases (particularly CaCO 3 ) greatly increased the precipitation pH in
northern China (Galloway et al. 1987). Different from the high base cation (mainly
as Ca
2+ ) deposition resulting from natural sources such as desert in northern and
northwestern China, the high BC deposition in eastern and southern China was
mainly attributed to the anthropogenic sources, including cement production and
coal combustion. Furthermore, NH 3 can provide alkalinity of precipitation in spite of
the consequently acidification of soil due to nitrification. Actually, ammonium was
the dominant form of N deposition in China (accounting for 60–70%; Chen and
Mulder 2007; Du et al. 2014; Fang et al. 2011; Yu et al. 2018).
The BC deposition has provided significant buffering capacity to soil acidification in China (Larssen et al. 2011; Yu et al. 2017c). However, most researches
neglected the functions of BC deposition on buffering and only focused on the
acidifying effects of acid deposition (Cui et al. 2014; Liu et al. 2013). Actually, the
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Q. Yu and L. Duan
played an important role in the neutralization processes (Yu et al. 2016b). The
surface water had high ANC because the carbonates in soil (even with low contents)
can buffer efficiently the acid input to the watershed (Hu et al. 1982). The release of
base cations by chemical weathering in the soil plays an important role in neutralization of acid in some upland lakes in southwest China (Xue and Schnoor 1994).
The subtropical forests in China have hot and humid monsoon climate (Kong et al.
1997). The forest soil is dominated by highly weathered red or yellow earth (Matson
et al. 1999), with low pH (<4.2) and BS (<10%) (Lu et al. 2015; Yan et al. 2015;
Huang et al. 2015), and experienced elevated acid deposition for more than two
decades. Dissolution of aluminosilicates buffers the H
+ input in South China due to
the low soil pH and results in high Al
3+ concentration in the soil water (Lassen et al.
2011; Yu et al. 2017c). The Al mobilization could buffer one-third of acidity input in
the NH 4 NO 3 -treated plot at Tieshanping in Chongqing (Huang et al. 2015).
The soil chemical weathering varies in different regions. In southeastern China
and large region in southwestern China, the Haplic Acrisol has a relatively low
weathering rate. The soil type in west part of southwestern China is dominated by
Haplic Luvisol, showing a higher weathering rate (Duan et al. 2002). The Haplic
Podzol and Albic Luvisol in northeast China developed from granite, having
extremely low weathering rate (Duan et al. 2002).
8.5.2 Buffering by Base Cation Deposition
The precipitation pH in China was not very low, even under elevated S and N
deposition, because of the high buffering by alkali, including base cations in
anthropogenic particulate matter (PM) (Zhu et al. 2004; Lei et al. 2011) and soil
dust (Larssen and Carmichael 2000), as well as NH 4
+ coming from NH 3 emission
from agricultural activities (Kang et al. 2016). The precipitations have higher BC
concentration in northern China than those in southern China or other industrial
nations (Wang and Wang 1996; Cao et al. 2013; Wang et al. 2012a). Therefore, the
soil-derived bases (particularly CaCO 3 ) greatly increased the precipitation pH in
northern China (Galloway et al. 1987). Different from the high base cation (mainly
as Ca
2+ ) deposition resulting from natural sources such as desert in northern and
northwestern China, the high BC deposition in eastern and southern China was
mainly attributed to the anthropogenic sources, including cement production and
coal combustion. Furthermore, NH 3 can provide alkalinity of precipitation in spite of
the consequently acidification of soil due to nitrification. Actually, ammonium was
the dominant form of N deposition in China (accounting for 60–70%; Chen and
Mulder 2007; Du et al. 2014; Fang et al. 2011; Yu et al. 2018).
The BC deposition has provided significant buffering capacity to soil acidification in China (Larssen et al. 2011; Yu et al. 2017c). However, most researches
neglected the functions of BC deposition on buffering and only focused on the
acidifying effects of acid deposition (Cui et al. 2014; Liu et al. 2013). Actually, the
172
Q. Yu and L. Duan