Adsorption and desorption characteristics of metal(oid)s in the yellow soils of a typical karst area, southwest China

Human agricultural activities have resulted in widespread land degradation and soil contamination in the karst areas. However, the effects of reforestation after agricultural abandonment on the mobility risks and contamination of heavy metals have been rarely reported. In the present study, six soil profiles were selected from cropland and abandoned cropland with reforestation in the Puding karst regions of Southwest China. The Community Bureau of Reference (BCR) sequential extraction method was used to evaluate the compositions of different chemical fractions of soil heavy metals, including Fe, Mn, Cr, Zn, Ni, and Cd. The total contents of Cr, Ni, Zn, Cd, and Mn in the croplands were significantly higher than those in the abandoned croplands. For all soils, Cr, Ni, Zn, and Fe were mainly concentrated in the residual fractions (>85%), whereas Mn and Cd were mostly observed in the non-residual fractions (>65%). The non-residual fractions of Cd, Cr, Ni, and Zn in the croplands were higher than those in the abandoned croplands. These results indicated that the content and mobility of soil heavy metals decreased after reforestation. The individual contamination factor (ICF) and risk assessment code (RAC) showed that Cd contributed to considerable contamination of karst soils. The global contamination factor (GCF) and potential ecological risk index (RI) suggested low contamination and ecological risk of the investigated heavy metals in the croplands, moreover they can be further reduced after reforestation.

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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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Impacts of climate change on regional hydrological regimes of the Wujiang River watershed in the Karst area, Southwest China

Geoenvironmental Disasters ◽

10.1186/s40677-015-0013-x ◽

2015 ◽

Vol 2 (1) ◽

Cited By ~ 5

Author(s):

Nianxiu Qin ◽

Junneng Wang ◽

Xi Chen ◽

Guishan Yang ◽

Haoyuan Liang

Keyword(s):

Climate Change ◽

Southwest China ◽

Karst Area ◽

River Watershed ◽

Wujiang River ◽

Hydrological Regimes ◽

Impacts Of Climate Change

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Tracer vertical movement and its affecting factors in karst soil profiles using the simulated leaching method

10.5194/ismc2021-33 ◽

2021 ◽

Author(s):

Jianghu He ◽

Keli Zhang ◽

Zihao Cao ◽

Qihua Ke

Keyword(s):

Soil Erosion ◽

Soil Loss ◽

Southwest China ◽

Vertical Movement ◽

Karst Area ◽

Affecting Factors ◽

Tracer Movement ◽

Traditional Research ◽

Movement Distance ◽

Karst Geomorphology

Soil erosion is a severe issue in Southwest China due to complex karst geomorphology and excessive farming activities. It is also difficult to observe and evaluate using traditional research methods. Fortunately, as a supplement to traditional methods, the 137Cs tracing technique has strong potential to monitor and evaluate soil loss in karst regions. However, 137Cs might move downward with tiny particles under adequate rainfall conditions. This is critical because it directly affects accuracy of using the 137Cs conversion model to evaluate soil erosion. Thus, in our study, in order to explore whether tracers actually moved vertically and to evaluate the movement distance and the factors influencing the movement, magnetic powder (Fe3O4) and rare earth oxides (CeO2 and La2O3) were used as the substitute tracers under different conditions (rainfall and leaching area) of a simulated leaching experiment, which possess similar properties as 137Cs and have no toxicity problems in humans and the environment. The results showed that tracers moved downward 6 cm when water was added to simulate 1-10-year rainfall conditions and 8 cm when water was added to simulate 15-20-year rainfall conditions. The movement distance of tracers increased slowly with increasing water input, and the concentration of the tracers that moved related indirectly to the leaching area. Tracer movement at the edge of the simulated profile was affected by tracer type and concentration since there was no transition layer between soil and plastic column. Our field observations in two karst watersheds showed that ignoring the vertical movement of tracer can cause the overestimation of soil loss amount by 6.90% and 22.22% respectively. This study proved that in the karst area of Southwest China with abundant rainfall, 137Cs would move vertically, and the soil loss will be overestimated if the vertical movement distance of the tracer is ignored.

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Interpretation of regional-scale distribution of high Hg in soils of karst area in southwest China

Geochemistry Exploration Environment Analysis ◽

10.1144/geochem2018-043 ◽

2018 ◽

Vol 19 (3) ◽

pp. 289-298

Author(s):

Lanshi Nie ◽

Xuemin Liu ◽

Xueqiu Wang ◽

Hanliang Liu ◽

Wei Wang

Keyword(s):

Southwest China ◽

Regional Scale ◽

Karst Area

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Annual Runoff is Highly Linked to Precipitation Extremes in Karst Catchments of Southwest China

Journal of Hydrometeorology ◽

10.1175/jhm-d-17-0032.1 ◽

2017 ◽

Vol 18 (10) ◽

pp. 2745-2759 ◽

Cited By ~ 17

Author(s):

Zhenwei Li ◽

Xianli Xu ◽

Chaohao Xu ◽

Meixian Liu ◽

Kelin Wang ◽

...

Keyword(s):

Water Resources ◽

Southwest China ◽

Climatic Factors ◽

Precipitation Amount ◽

Heavy Precipitation ◽

Annual Runoff ◽

Climatic Variables ◽

Precipitation Extremes ◽

Karst Area ◽

Least Squares Regression

Abstract Karst landforms cover 7%–12% of the Earth’s continental area and provide water resources for 25% of the global population. Climate, particularly frequent climate extremes, may greatly affect the annual runoff, especially in climate-sensitive regions such as a karst area of southwest China. Knowledge of the linkage between climate and runoff is urgently needed for smart water resources management. This study therefore selected five catchments that have different carbonized rock coverage (from 11% to 64%) to detect the dominant climatic variables driving changes in annual runoff for the period of 1957–2011 in southwest China. Because climatic variables are highly codependent, a partial least squares regression (PLSR) was used to elucidate the linkages between runoff and 17 climatic variables. Results indicated that the dominant climatic factors driving annual runoff are annual total precipitation, rainy days, heavy precipitation amount, heavy precipitation days, rainstorm amount, and rainstorm days. These six factors are generally used to represent extreme climatic events, and hence it may demonstrate that annual runoff is highly linked to precipitation extremes in this region. The PLSR approach presented in this study is beneficial and novel, as it enables the elimination of codependency among the variables and facilitates a more unbiased view of the contribution of the changes in climatic variables to the changes in runoff. As a practical and simple tool, the PLSR approach is thus recommended for application to a variety of other catchments.

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Forestland change and soil erosion in karst watershed under the Grain to Green Project

10.5194/egusphere-egu2020-4456 ◽

2020 ◽

Author(s):

Siwen Feng ◽

Hongya Wang ◽

Hongyan Liu ◽

Chenyi Zhu ◽

Shuai Li

Keyword(s):

Soil Erosion ◽

Influencing Factors ◽

Southwest China ◽

Drainage Basin ◽

Karst Area ◽

Karst Region ◽

Vegetation Growth ◽

The Past ◽

Pixel Scale ◽

River Drainage Basin

<div>With the implementation of the Grain to Green Project, the vegetation growth in karst region in southwest China has increased. In order to explore whether the growth of trees can be sustained after artificial afforestation in karst area and the influence of the forestland change on soil erosion, the WaTEM/SEDEM model was used to simulate the 11 stages of annual soil erosion in the past 33 years in Chongan river drainage basin in Guizhou, and the dominant influencing factors of soil erosion change in the past 33 years were discussed based the pixel scale in this study. The results showed that the forestland increased in a fluctuating way after the conversion project, and the decrease of forestland was mainly caused by drought, especially in the area where the dolomites were distributed. Therefore, the change of forestland caused no significant improvement in soil erosion since the Grain to Green Project.</div>

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