Data of monitoring the Oplotnica River silicate catchment (Slovenia) using stable carbon and nitrogen isotopes

Herein, we present a dataset of the geochemical and isotopic characteristics of water collected from September 2012 to June 2014 to evaluate biogeochemical processes within the Oplotnica River silicate catchments. Additionally, we collected soil samples at Javorski creek to characterize the soil profiles using stable isotopes of carbon and nitrogen.
Discharge and temperature data for the Oplotnica River at the Perovec gauging station were gathered from the Slovenian environment agency. Temperature at both Javorski and Lukanjski creeks was measured on-site, while pH and conductivity were measured in the lab with Metrohm pH low ionic strength glass electrode and Pt1000 electroconductivity electrode, connected to Metrohm 712 Conductometer. Cations (Na+, K+, Ca2+, Mg2+, Mn2+, NH4+) were analyzed with Metrohm Metrosep C4-150/4.0 column without suppression and anions (NO3-, NO32-, SO42-, Cl-, PO43-) with Metrohm Metrosep A Supp 5-150/4.0 column with chemical suppression. Both connected in Metrohm Ion Chromatography modular system. Total alkalinity was measured with double-end point titration (pH=4.5, 4.2) measuring pH with Metrohm pH low ionic strength glass electrode and titrating with 0.01 M HCl controlled by Metrohm 702 SM Titrino titrator. Dissolved organic carbon (DOC) was measured with TOC analyser Shimadzu TOC-5000A as a difference between dissolved total carbon (DTC) and dissolved inorganic carbon (DIC).
Thermodynamic modeling was performed with the PHREEQC speciation program to evaluate pCO2 and the saturation state of calcite and dolomite.
The major solute composition of the analyzed surface water was as follows: Na+Ca2+Mg2+K+ and HCO3-SO42-Cl-NO3-. In surface water the δ13CDIC ranged from -26.1‰ to -1.4‰, and the 13CPOC from -28.2 to -22.3‰, and 15N from -2.2 to 2.6‰ (measured only in September 2012). 13Corg. ranged from -28.3 to -24.9‰, while 15N ranged from -4.9 to 5.4‰ at three soil profiles (up to a depth of 70 cm) at Tratice I, II and III locations at Javorski creek. Characteristic plants within catchment area have 13C in the range from -31.2 to -29.2‰ and 15N in the range from -8.0 to -5.5‰.
Data were collected through field and laboratory analyses. These data were used to calculate saturation indices, partial pressure of CO2 (SIcalcite, SIdolomite, pCO2), and to perform a mass balance calculation of carbon to determine the processes that contribute most to the isotopic composition of dissolved inorganic carbon (δ13CDIC). Furthermore, bicarbonate weathering intensity was calculated within the catchment area. The main conclusions are that the saturation index of calcite (SIcalcite) ranges from -6.1 to -1.9, and the saturation index of dolomite (SIdolomite) ranges from -12.7 to -4.2. The bicarbonate weathering intensity is 10.4 mmol/km²·s, which is typical for silicate catchments.

本项研究中，我们呈现了一组自2012年9月至2014年6月期间收集的水样，其中包含了其地球化学和同位素特征，旨在评估奥波特尼察河流域硅酸盐流域内的生物地球化学过程。此外，我们在贾沃尔斯基溪收集了土壤样本，利用碳和氮的稳定同位素来表征土壤剖面。奥波特尼察河在佩罗韦茨流量站的流量和温度数据由斯洛文尼亚环境署提供。贾沃尔斯基和卢卡恩斯基溪的温度在现场测量，而pH值和电导率则在实验室使用Metrohm pH低离子强度玻璃电极和Pt1000电导率电极进行测量，电极连接至Metrohm 712电导率计。阳离子（Na+、K+、Ca2+、Mg2+、Mn2+、NH4+）的分析采用Metrohm Metrosep C4-150/4.0柱，无需抑制，而阴离子（NO3-、NO32-、SO42-、Cl-、PO43-）则使用带有化学抑制剂的Metrohm Metrosep A Supp 5-150/4.0柱，两者均连接至Metrohm离子色谱模块系统。总碱度通过双端点滴定法（pH=4.5、4.2）进行测量，使用Metrohm pH低离子强度玻璃电极测量pH值，并使用0.01 M HCl进行滴定，滴定过程由Metrohm 702 SM Titrino滴定仪控制。溶解有机碳（DOC）通过Shimadzu TOC-5000A总有机碳分析仪测量，其值为溶解总碳（DTC）与溶解无机碳（DIC）之差。热力学模型使用PHREEQC物种程序进行，以评估pCO2及方解石和白云石的饱和状态。所分析地表水的主要溶解质组成如下：Na+ > Ca2+ > Mg2+ > K+ 和 HCO3- > SO42- > Cl- > NO3-。在地表水中，δ13CDIC的值介于-26.1‰至-1.4‰之间，δ13CPOC的值介于-28.2至-22.3‰之间，δ15N的值介于-2.2至2.6‰（仅在2012年9月测量）。δ13Corg.的值介于-28.3至-24.9‰之间，而δ15N的值介于-4.9至5.4‰之间，测量地点为贾沃尔斯基溪的特拉齐奇I、II和III处的三个土壤剖面（深度达70厘米）。流域内的典型植物δ13C值介于-31.2至-29.2‰之间，δ15N值介于-8.0至-5.5‰之间。数据通过现场和实验室分析收集而来。这些数据被用于计算饱和指数、二氧化碳分压（SIcalcite、SIdolomite、pCO2），并执行碳质量平衡计算，以确定对溶解无机碳同位素组成（δ13CDIC）贡献最大的过程。此外，在流域区域内计算了重碳酸盐风化强度。主要结论是，方解石的饱和指数（SIcalcite）介于-6.1至-1.9之间，白云石的饱和指数（SIdolomite）介于-12.7至-4.2之间。重碳酸盐风化强度为10.4 mmol/km²·s，这对于硅酸盐流域来说是典型的。