Response of Trace Element Migration to Extreme Autumn Rain in Karst Critical Zone in Northern China

<p indent="0mm">Global warming leads to frequent extreme climate events. To explore the spatial-temporal variations of trace elements in the karst critical zone in northern China under the influence of extreme autumn rain, as well as the response of trace elements in drips from various caves to heavy rainfall. From August 26 to August 28, 2023, a high-resolution continuous day and night rainstorm monitoring was conducted in Jiguan Cave and Dongshiya Cave, Luanchuan County, western Henan Province, at the north foot of the eastern section of the Qinling Mountains. The results showed that: (1) the heavy precipitation process was mainly affected by the southward retreat of the Western Pacific subtropical high, and the warm and cold air strongly intersected. The trace element ratios in different water bodies in the karst critical zone was controlled by the change of precipitation in the study area caused by the regulation of atmospheric circulation. <sc>(2) Influenced</sc> by the superposition of summer precipitation, the response time of drip rate to this extreme autumn rain event is about 10h. The leaching and dilution effects of precipitation on surface soil and bedrock are the main factors affecting the content and ratio of trace elements in the karst critical zone. (3) The trace elements and their ratios and physical and chemical parameters (HCO<inline-formula id="INLINE4"> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" mathsize="8.0pt"> <mml:mrow> <mml:msubsup other="0"> <mml:mrow other="0"/> <mml:mn mathsize="5.6pt" other="1">3</mml:mn> <mml:mo mathsize="5.6pt" other="1">−</mml:mo> </mml:msubsup> </mml:mrow> </mml:math> </inline-formula>, Cl^–, SO<inline-formula id="INLINE5"> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" mathsize="8.0pt"> <mml:mrow> <mml:msubsup other="0"> <mml:mrow other="0"/> <mml:mn mathsize="5.6pt" other="1">4</mml:mn> <mml:mrow other="1"> <mml:mn mathsize="5.6pt" other="1">2</mml:mn> <mml:mo mathsize="5.6pt" other="1">−</mml:mo> </mml:mrow> </mml:msubsup> </mml:mrow> </mml:math> </inline-formula>,NO<inline-formula id="INLINE6"> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" mathsize="8.0pt"> <mml:mrow> <mml:msubsup other="0"> <mml:mrow other="0"/> <mml:mn mathsize="5.6pt" other="1">3</mml:mn> <mml:mo mathsize="5.6pt" other="1">−</mml:mo> </mml:msubsup> </mml:mrow> </mml:math> </inline-formula>, EC) of the four drips in Jiguan Cave and Dongshiya Cave are sensitive to the heavy precipitation process. However, the fluctuation trends of trace element ratios at different drips in different caves varied due to factors such as the migration path, pipeline fracture inhomogeneity, overlaying bedrock thickness, and cave growth structure. This information will be useful in the research of trace element response mechanisms in karst critical zones to extreme climate events.