The effects of agricultural activities and atmospheric acid deposition on carbonate weathering in a small karstic agricultural catchment, Southwest China

Karst water is vital for local drinking and irrigation but is susceptible to contamination. Hydrochemistry, which is highly related to carbonate weathering in karst catchments, can affect water quality and respond rapidly to climate change. In order to explore hydrogeochemical sources, dynamics, and their responses to rainstorms, rainwater, throughfall, hillslope runoff, surface water, and groundwater were sampled synchronously during rainstorms at a karst Critical Zone Observatory (CZO), Southwest China. Results showed that the total dissolved solids (TDS) concentration in throughfall increased by 30.1 ± 8.0% relative to rainwater, but both throughfall and rainwater contributed little to TDS in surface water and groundwater compared with terrestrial sources. Hydrochemistry in surface water and groundwater was diluted by rainstorms but displayed chemostatic responses with different intensities to increasing discharge. This is possibly regulated by hydrogeological conditions, available sources of various solutes, and the difference between solute concentrations before and after rainstorms. Ca2+ and Mg2+ dynamics were mainly regulated by carbonate weathering, gypsum dissolution, and gypsum-induced dedolomitization (geological sources), which also affect Ca2+, Mg2+, and SO42- in deep confined groundwater draining a gypsum stratum. For HCO3-, CO2 from respiration and microbiologic activities is one dominant contributor, especially for spring. The chemostatic behaviors of NO3-, Cl−, and K+ were related to agricultural activities, especially in surface water. These controls on hydrochemistry may already exist as hillslope runoff occurs, which has be further demonstrated by principle component analysis (PCA). The heterogeneous permeability of epikarst can affect the mixture of groundwater from different sources and flowing pathways, enabling hydrochemistry at different hydrogeological conditions to display discrepant responses to rainstorms. The epikarst aquifer with high permeability is susceptible to changes in external environment, such as rainstorms and agricultural activities, increasing the potential risk of water environment problems (chronic pollution of nitrogen and high hardness of water) during a certain period. Drinking water safety thus deserves consideration in the agricultural karst catchment.

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Relative humidity and agricultural activities dominate wildfire ignitions in Yunnan, Southwest China: Patterns, thresholds, and implications

Agricultural and Forest Meteorology ◽

10.1016/j.agrformet.2021.108540 ◽

2021 ◽

Vol 307 ◽

pp. 108540

Author(s):

Lingxiao Ying ◽

Hujiao Cheng ◽

Zehao Shen ◽

Pingao Guan ◽

Caifang Luo ◽

...

Keyword(s):

Relative Humidity ◽

Southwest China ◽

Agricultural Activities

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Impact of different fertilizers on the carbonate weathering in a typical karst area, Southwest China: a field column experiment

10.5194/esurf-2016-50 ◽

2016 ◽

Author(s):

Chao Song ◽

Changli Liu ◽

Guilin Han

Keyword(s):

Southwest China ◽

Column Experiment ◽

Phosphate Fertilizer ◽

Global Scale ◽

Karst Area ◽

Carbonate Weathering ◽

Nitrogenous Fertilizer ◽

Co2 Consumption ◽

Common Ion ◽

Calcium Magnesium

Abstract. Carbonate weathering, as a significant vector for the movement of carbon both between and within ecosystems, are strongly influenced by anthropogenic perturbations such as agricultural fertilization. Different fertilizer may exert a different impact on carbonate weathering, but their differences are not still well-known so far. In this study, a field column experiment was employed to explore the responses of carbonate weathering to different fertilizer addition. The eleven different treatments with three replicates including control, NH4NO3, NH4HCO3, NaNO3, NH4Cl, (NH4)2CO3, Ca3(PO4)2, (NH4)3PO4, fused calcium-magnesium phosphate fertilizer (Ca-Mg-P), Urea and K2CO3 were established in this column experiment, where limestone and dolostone tablets were buried at the bottom of each to determine the weathering amount and ratio of carbonate in soil. The result showed that the addition of urea, NH4NO3, NH4HCO3, NH4Cl and (NH4)2CO3 distinctly increased carbonate weathering, which was attributed to the nitrification of NH4+, and the addition of Ca3(PO4)2, Ca-Mg-P and K2CO3 induced carbonate precipitation due to common ion effect. Whereas the (NH4)3PO4 and NaNO3 addition did not impact significantly on carbonate weathering. The results of NaNO3 treatment seem to be raising a new question: the little impact of nitrate on carbonate weathering may result in the overestimation of impact of N-fertilizer on CO2 consumption by carbonate weathering at the regional/global scale if the effect of NO3 and NH4 are not distinguished. Moreover, in order to avoid misunderstanding more or less, the statement that nitrogenous fertilizer can aid carbonate weathering should be replaced by ammonium fertilizer.

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