Repository_data_EB_MK_2018

Major ion concentration data including sodium (Na+), potassium (K+), calcium (Ca2+), magnesium (Mg2+), chloride (Cl–), sulfate (SO42–), bicarbonate (HCO3–), carbonate (CO32–), and pH (if it was coupled with ion data) were compiled into a database. The data were drawn from a large geographic scale across Eurasia (Austria, China, Hungary, Kazakhstan, Mongolia, Russia, Serbia, and Turkey) and from a large number of saline lakes and pans (N = 220) with a minimum of 1.0 g L–1 salinity threshold. The 1.0 g L–1 salinity threshold was selected on the basis of a former study [27], where this threshold was experimentally found to be the characteristic boundary of soda ecosystems. Salinity (TDS) was estimated by the sum of major ion concentrations (Na+, K+, Ca2+, Mg2+, Cl–, SO42–, HCO3–, and CO32–) and 1 mg L-1 accuracy was used for all input concentration data independently of the theoretical accuracy of original measurements, therefore decimals were rounded to integer value. As generally known, sodium is by far the most common cation in saline lakes and necessarily the dominant cation in soda type of lakes [1]. Therefore, sites with the most abundant ion other than Na+ were excluded from the dataset. If seasonal or annual water data were available, we used mean values for the database. Most of the data came from papers [1,15,26-39] published in the period from 1956 to 2017. However, we cannot estimate a reliable universal accuracy and reproducibility for all data in this study, because none of the published papers reviewed provide data on uncertainty, furthermore, several of them were carried out by different kinds of national standard methods of ion concentration measurements, but all of them are based on the same international methods of ICP-MS for cations (ASTM 3500-Na-C, -K-C, -Ca-C, -Mg-C), alkalinity titration (ASTM 2320 B), chloride argentometric titrimetry (ASTM 4500-Cl-B) as well as sulfate ions turbidimetry (ASTM 4500-SO42-E). The large geographic distribution of the lakes and pans assessed in the dataset can be seen in the Fig. 1 by countries and references. The collected published data were supplemented with some unpublished sample series in the case of Mongolia and Kazakhstan. Coordinates, countries, sites, pH, and ion composition (e%) data of these additional sites are listed in Appendix 1. pH was measured on site using a WTW multiline field instrument with a SenTix 41 electrode. The samples were filtered through GF5 glass fiber filters (0.4 μm nominal pore size) in the laboratory. For the determination of cations (Na+, K+, Ca2+, and Mg2+), samples were analyzed with the EPA 6020 standard method of inductively coupled plasma mass spectrometry [40] with 2% accuracy. Anion concentrations were measured according to Hungarian standard analytical methods (MSZ). Chloride ion concentration was determined by the argentometric method (MSZ 448-15:1982). Sulfate ion was precipitated in a strong acidic medium with barium chloride, and the resulting turbidity was measured photometrically at 405 nm and compared with standard solutions (MSZ 12750-16:1998). Alkalinity was determined by titration, and the concentration of HCO3–, CO32–, and OH– ions was calculated using the Hungarian standard MSZ 448-11:1986. All of anions and alkalinity were measured with 5% accuracy.本研究将包含钠离子（Na+）、钾离子（K+）、钙离子（Ca²+）、镁离子（Mg²+）、氯离子（Cl–）、硫酸根离子（SO4²–）、碳酸氢根离子（HCO3–）、碳酸根离子（CO3²–）以及与离子数据配套的pH值在内的主要离子浓度数据整合至数据库中。 该数据集覆盖欧亚大陆广阔地理范围（涵盖奥地利、中国、匈牙利、哈萨克斯坦、蒙古国、俄罗斯、塞尔维亚与土耳其），包含220个盐度不低于1.0 g·L⁻¹的咸水湖与盐盘。本次研究选取1.0 g·L⁻¹作为盐度阈值，依据参考文献[27]的研究结果——该阈值经实验确定为苏打型生态系统的特征分界点。总溶解固体（Total Dissolved Solids, TDS）通过上述主要离子浓度之和进行估算；所有输入的浓度数据均统一采用1 mg·L⁻¹的精度标准，不考虑原始测量的理论精度，因此将所有小数位数值修约为整数。 众所周知，钠离子是咸水湖中最主要的阳离子，同时也是苏打型咸水湖的绝对优势阳离子[1]。因此，本数据集剔除了除钠离子外其他离子占比最高的采样点。若存在季节或年度的水体监测数据，本数据库统一采用其平均值。 本数据集大部分数据来源于1956年至2017年间发表的文献[1,15,26-39]。但由于本次调研所纳入的已发表文献均未提供数据不确定性相关信息，且部分研究采用了不同的国家标准离子浓度测定方法，因此无法对本研究中所有数据的通用精度与可重复性做出可靠评估。不过所有阳离子检测均采用电感耦合等离子体质谱（Inductively Coupled Plasma Mass Spectrometry, ICP-MS）的国际标准方法：ASTM 3500-Na-C、ASTM 3500-K-C、ASTM 3500-Ca-C、ASTM 3500-Mg-C；碱度滴定采用ASTM 2320 B标准；氯离子采用银量滴定法（ASTM 4500-Cl-B）；硫酸根离子采用浊度法（ASTM 4500-SO4²–-E）。 本数据集所涵盖的咸水湖与盐盘的大范围地理分布情况，可参见图1中按国家与参考文献标注的分布信息。针对蒙古国与哈萨克斯坦的采样点，本研究还补充了部分未发表的系列样品数据。新增采样点的坐标、所属国家、采样点位、pH值及离子组成（e%）信息详见附录1。 pH值采用WTW多参数野外检测仪搭配SenTix 41型电极进行现场测定。样品在实验室中经孔径标称值为0.4 μm的GF5型玻璃纤维滤膜过滤。阳离子（Na+、K+、Ca²+、Mg²+）的检测采用EPA 6020标准电感耦合等离子体质谱法[40]，检测精度为2%。 阴离子浓度的测定采用匈牙利国家标准分析方法（MSZ）：氯离子采用银量法（MSZ 448-15:1982）；硫酸根离子在强酸性介质中与氯化钡反应生成沉淀，通过405 nm波长下的浊度光度法测定并与标准溶液比对（MSZ 12750-16:1998）；碱度采用滴定法测定，并依据匈牙利国家标准MSZ 448-11:1986计算HCO3–、CO3²–与OH–离子浓度。所有阴离子与碱度的检测精度均为5%。