Effect of water quality on the leaching of potassium from sandy soil

When potassium (K⁺) fertilizers are applied to soil, K⁺ is subject to displacement through the soil profile. More generally, the application of K⁺ fertilizers to sandy soils with low clay content and small buffer capacity, in which K⁺ does not interact strongly with the soil matrix, results in localized increases in K⁺ concentration in the soil solution. Losses of K⁺ depend on the concentration of calcium (Ca²⁺) as a competing ion in the leaching water and the amount of water that passes through the soil. In this study, we examined the adsorption and movement of applied K⁺ in columns of sandy soil. Glass tubes, 4.8 cm in diameter and 40 cm in length, were packed with either native soil or Ca²⁺-saturated soil. The resulting 10-cm-long column of soil had a bulk density of 1.65 g cm⁻³. Native soil was leached with distilled water and CaCl₂ solutions of various concentrations. In the Ca²⁺-saturated soil, a pulse of K⁺ was leached with CaCl₂ solutions of various concentrations or distilled water. Increasing the CaCl₂ concentration from 3 to 15 mm resulted in earlier breakthrough, a higher peak concentration of K⁺, and greater amounts of leached K⁺. The breakthrough curve for K⁺, when leached with distilled water, showed very low concentrations and was more delayed than the other treatments. In Ca²⁺-saturated soil, the amount of K⁺ leached increased as Ca²⁺ concentration increased, with up to 54% of the added pulse K⁺ being removed from 10 pore volumes (Pv) (387 mm) of 15 mm CaCl₂. The presence of Ca²⁺ in irrigation water and soil minerals able to release Ca²⁺ is important in determining the amount of K⁺ leached from soils. Large amounts of K⁺ are leached from soils in areas where crops are irrigated with water that contains significant concentrations of Ca²⁺ and other cations.     

3种耐盐植物的根际微环境比较

研究了兰州市永登县秦王川灌区中型狼尾草（Pennisetum longissimum var. intermedium）、新疆大叶苜蓿（Medicago sativa）和皮燕麦（Avena sativa）对盐渍土的适应特点及其改盐效应。通过对3种植物不同生育期（播后90 d、120 d、150 d）根际土壤pH值、导电率（EC）、盐分离子及有机质含量的测定,探讨盐渍化土壤影响下耐盐植物根际微环境的变化。结果显示：在盐渍化逆境下,3种植物对于根际土壤微环境均有一定调节作用,生育期内土壤pH值、EC值、Na⁺、SO₄^2-、Cl^-和Ca²⁺含量逐渐降低,土壤有机质含量逐渐增加。新疆大叶苜蓿根际土壤pH值变化较为突出,其次是中型狼尾草和皮燕麦,播后150 d较播前降幅分别为2.18%、2.06%、1.21%;中型狼尾草根际土壤EC值降幅最大,其次为新疆大叶苜蓿和皮燕麦,播后150 d较播前降幅分别为42.69%、33.29%、28.33%;在3个取样期,中型狼尾草根际土壤Na⁺、SO₄^2-、Cl^-含量变化幅度最大,新疆大叶苜蓿对Ca²⁺的吸收能力强于中型狼尾草和皮燕麦;中型狼尾草在生长期内根际土壤有机质含量持续增加,新疆大叶苜蓿在生长前期有机质增量较显著,生长中后期增量减缓,根际微环境变化趋于稳定。综合而言,中型狼尾草对盐渍土的适应及改良效应较突出,其次是新疆大叶苜蓿,再次是皮燕麦。     

Plants as soil indicators along the Saudi coast of the Arabian Gulf

Soils of different vegetation types of the Saudi Arabian Gulf coast, dominated by mangrove, salt marsh and desert plant communities have been analysed for their soil profiles, texture, salinity, pH, water content and ionic concentration (Ca²⁺, Cl⁻, K⁺, Na⁺, SO₄²⁻). The results show some important relationships between soils and plants. Special emphasis was given to the dominant intertidal plantsAvicennia marina, Arthrocnemum macrostachyum, Salicornia europaea, Halocnemum strobilaceum, Halopeplis perfoliata, Limonium axillare, the terrestrialZygophyllum qatarense, and non-vegetated sabkhas.     

The controls on phosphorus availability in a Boreal lake ecosystem since deglaciation

The sediment record from a 5.3-m core from Sargent Mountain Pond, Maine USA indicates strong co-evolutionary relationships among climate, vegetation, soil development, runoff chemistry, lake processes, diatom community, and water and sediment chemistry. Early post-glacial time (16,600–12,500 Cal Yr BP) was dominated by deposition of mineral-rich sediment, low in organic matter and secondary hydroxides of Al and Fe; pollen indicate tundra conditions; diatom taxa indicate pH between 7.5 and 8, and total P concentrations of about 25 μg L⁻¹, favoring higher productivity. Chemical weathering was rapid, with high alkalinity, pH, Ca, and P in runoff. As climate ameliorated, about 12,500 Cal Yr BP, forest vegetation became established; soils would have developed vertical zonation, including organic matter accumulation, and incipient podzolic horizons, with accumulating secondary hydroxides of Al and Fe that sequestered P in the soils. Labile minerals (primarily apatite, Ca₅(PO₄)₃(OH,F,Cl)) became depleted in the soil, further reducing the supply of P to the lake. Dissolved organic carbon (DOC) from soil organic matter mobilized Al and Fe to the lake where Al(OH)₃ (primarily) and Fe(OH)₃ (minor) were precipitated. The sedimenting hydroxides adsorbed P from the water column, further reducing bioavailable P. These long-term trends of moderating climate, and changing terrestrial biology, soils, and aquatic chemistry and phytoplankton were interrupted by the 1,000-year long Younger Dryas cooling, which led to a temporary reversal of these processes, a period that ended with the major onset of Holocene warming. The sequestration of P by soils would have strengthened because of long-term soil acidification and pedogenesis. The lake was transformed from a more productive, high P, high pH, low DOC system into an oligotrophic, relatively low P, acidic, humic lake over a period of 16,600 years, a natural trend that continues. In contrast to many human-affected lakes that become increasingly eutrophic, many lakes become more oligotrophic during their history. The precursors for that are: (1) absence of human land-use in watersheds, (2) bedrock lithology and soil with a paucity of soluble Ca-rich minerals, and (3) vegetation that promotes the accumulation of soil organic matter, podzolization, and increased export of metal-DOC complexes, particularly Al.     

基于氢氧同位素与水化学的潮白河流域地下水水循环特征

为了研究变化环境下潮白河流域地下水水循环规律,通过现场调查,结合环境同位素及水化学应用,对潮白河流域浅层和深层地下水采样,测定其氢、氧环境同位素及水化学成分,通过分析其变化特征判明地下水的补给来源以及各含水层的相互联系。降水和地下水中的环境同位素δD和δ¹⁸O组成分析表明,降水是山前地下水的主要补给源,山区浅层地下水受蒸发影响非常强烈。水化学研究结果表明,山区地下水水质以 Ca²⁺和 HCO^-₃为主,属Ca²⁺-Mg²⁺-HCO^-₃型地下水。山前地下水类型为Ca²⁺-Mg²⁺-HCO^-₃、 Na⁺-K⁺-HCO^-₃、Mg²⁺-Ca²⁺-HCO^-₃和 Ca²⁺-Mg²⁺-Cl^--SO^2-₄。平原区地下水为Mg²⁺, Na⁺和HCO^-₃。滨海冲积海积平原为Ca²⁺-Mg²⁺-HCO^-₃型和Ca²⁺-Mg²⁺-Cl^--SO^2-₄型地下水。水化学分析证实了越流补给的存在。Ca²⁺ 和 HCO^-₃离子均呈山区高、山前和平原低、而滨海增高的趋势。沿潮白河流向地下水类型变化为:Ca²⁺-Mg²⁺-HCO^-₃ Na⁺＝K⁺-HCO^-₃ Ca²⁺-Mg²⁺-HCO^-₃。     

纳滤法用于铝锂分离的初步研究

本文探讨了纳滤分离Al³⁺和Li⁺的可行性,研究了含盐量和铝锂比对分离效率的影响,提出了从锂云母浸出液中分离回收锂的新方法。实验结果表明,纳滤膜对Al³⁺和Li⁺的截留率随含盐量的升高而降低,其中Li⁺始终呈现负浓度梯度扩散的趋势,而Al³⁺的截留率始终稳定在99%以上。当含盐量为45 g/L时,铝锂分离因子最高可达248.33,膜面相应Zeta电位的绝对值达到最大。随着溶液中铝锂比的变化,Al³⁺和Li⁺的截留率分别在不同铝锂比的条件下出现拐点,溶液的pH呈现先下降后上升最后下降的复杂趋势。本实验研究发现,DK膜能够在酸性环境下实现高效的铝锂分离和锂的浓缩,从而为锂云母浸出液中锂的提取提供新的思路。     

三种土壤铅和镉的质量基准初步研究*

在制定地下水源保护区污染控制措施时,最常遇到的问题之一是缺少土壤包气带和含水层中化学物质的基准和标准。文中以铅、镉为例,结合北京、唐山地下水水源地实际情况,运用“平衡分配法”,根据土壤对铅和镉的吸附容量和分配系数研究包气带土壤中的铅和镉的质量基准。结果表明,土壤中铅和镉的质量基准与溶液pH值成对数线性关系,据此可计算不同pH条件下的土壤中重金属的质量基准。     

黄土中古土壤淀积类型

作者在西安附近发现了第１、４层古土壤的双层淀积和第５、８层古土壤多层淀积现象。资料表明，双层淀积、多层淀积和厚度异常大的ＣａＣＯ３淀积层是土壤具多元发生过程或受后期淋溶的产物，它们常代表两个或两个以上的成壤期。第１层古土壤下部的两层结构均不属古土壤组合部分，该层土壤为中、酸性森林土壤。第８层古土壤特殊的厚层淀积代表了气候的多次变化和多个成壤期。第４、５层古土壤具不连续ＣａＣＯ３和Ｆｅ２Ｏ３、Ａｌ２     

察尔汗盐湖卤水自然蒸发过程中Ca2+分布规律研究

卤水中钙离子的存在会对盐湖化工生产及其产品质量造成较大影响,研究钙离子在卤水蒸发过程中的分布规律具有重要意义。通过室外自然蒸发及盐田实地采样,研究了察尔汗盐湖盐田生产过程中钙离子分布变化规律。结果表明,在自然蒸发实验中卤水钙离子浓度随蒸发量的增加逐渐减少,在盐田生产现场采样结果显示钙离子浓度随卤水蒸发而增加,结合生产实际,推断外界钙离子补给是造成这种现象的主要原因。因此,避免车间含钙尾水混入,阻止盐田卤水和周边土壤可溶性钙盐间离子交换是有效降低卤水钙离子浓度的主要方法。     

Badger (Taxidea taxus) disturbances increase soil heterogeneity in a degraded shrub-steppe ecosystem

In the western United States, overgrazing, weed invasion and wildfire have resulted in the conversion of shrub-steppe to annual grasslands, with substantial effects on ecosystem function. In these landscapes, badgers disturb large areas of soil while foraging for fossorial animals. Mounds created by badgers contained the lowest concentrations of total carbon, nitrogen and sulphur, mineral nitrogen and mineralizable nitrogen, inter-mound soils had the highest concentrations, and excavation pits had intermediate levels. Soil C:N ratio and pH were greater, and electrical conductivity and soluble Ca²⁺, Mg²⁺ and K⁺ were lower on mound soils compared with either pit or inter-mound soils. Larger pits generally trapped more litter, and increased litter mass equated with greater concentrations of active carbon, but only at the burned sites. Older mounds supported more vascular plants and cryptogamic crusts. Our results demonstrate reduced levels of nutrients and a higher C:N ratio on the mounds compared with either the pits or inter-mounds. Alteration to the homogeneous post-fire landscape by badgers contributes to patchiness in soils and vegetation, which is critical to the functioning of arid systems. Given their effect on soil C:N ratios, mounds may be important sites for recovery of indigenous shrub-steppe plant species.     

Hydrochemical regime and its mechanism in Yamzhog Yumco Basin,South Tibet

The hydrochemistry of alpine lakes reflects water characteristic and its response to climatic change. Over 300 water samples had been collected from 52 sites of 5 lakes and 7 inflowing rivers in the Yamzhog Yumco Basin, South Tibet, during 2009–2014, basing which the hydrochemical regime and its mechanism were analyzed along with the adoption of hydrological investigations in 1979 and 1984 as well. Results revealed that the waters were hard with weak alkalinity for the Yamzhog Yumco Basin. Most of them were fresh, and the rest were slightly saline. The hydrochemical types of 5 lakes (i.e., Lake Yamzhog Yum Co, Puma Yum Co, Bajiu Co, Kongmu Co, and Chen Co) were SO₄ ^2––HCO₃ ^––Mg²⁺–Na⁺, HCO₃ ^––SO₄ ^2––Mg²⁺–Ca²⁺, SO₄ ^2––Mg²⁺–Na⁺, SO₄ ^2––HCO₃ ^––Ca²⁺, and SO₄ ^2––Na⁺–Mg²⁺–Ca²⁺, respectively. As for rivers, HCO₃ ^– and SO₄ ^2– were the major anions, and Ca²⁺ was the dominant cation. Lake Yamzhog Yum Co, the largest lake in the basin, exhibited remarkable spatial variations in hydrochemistry at its surface but irregular changes with depth. The weathering of evaporates and carbonates, together with evaporation and crystallization, were the major mechanisms controlling the hydrochemistry of waters in the Yamzhog Yumco Basin. Global warming also had significant impacts on hydrochemical variations.     

Climatic Changes from 12,000 to 4,000 Years Ago in the Austrian Central Alps Tracked by Sedimentological and Biological Proxies of a Lake Sediment Core

Major and trace elements, minerals, and grain-size were analysed from the early to mid-Holocene (12 to 4 ky BP) period of a sediment core from the Alpine lake Oberer Landschitzsee (ObLAN, 2076 m a.s.l.), which is located on predominantly crystalline bedrock on the southern slopes of the Austrian Central Alps. Geochemistry and mineralogy were compared with diatom-inferred (Di-) ‘date of autumn mixing’ (A_mix), DOC, pH, and selected indicator pollen species from the same sediment core. Principal components analysis (PCA) indicated a positive correlation between processes triggered by temperature and precipitation (e.g., lake mixing, DOC). PCA grouped indicators of physical weathering and enhanced catchment run-off (sand, quartz, feldspar), elements of weathering (e.g., Ti, Rb, Mn) under dryer conditions (clay to silt fractions), and elements that probably were related to changes in redox conditions (Cu, Fe, S, Zn). The duration and height of the snow-pack played an important role in this high-alpine environment, affecting weathering, erosion, pH, and lake stratification. Low Alnus viridis pollen abundance, together with markers for increased elements of erosion, indicated extensive snow-pack. Changes in S coupled with As, and elements indicating increased weathering, reflected climate oscillations. LOI was affected by productivity and erosion. High (late) Di–A_mix coupled with increased Di-DOC indicated prolonged summers with increased productivity. Cold and wet (snow-rich) phases and subsequent melting caused low pH and a decoupling of the significant linear correlation between sedimentary Ca and Di-pH. Weathering and leaching during climate deteriorations opposed the long-term trend in a loss of cations and forced in-lake alkalinity generation during the following lake warming. Overall, the multi-proxy study indicated complex climate-driven processes within different time-scales (long-term trends, climate oscillations, seasonality). The climate oscillations within 12–5 ky BP corresponded well with the cool and wet phases known from central Europe suggesting a dominant common Atlantic climate impact. When Mediterranean climate established between 5 and 4 ky BP, its influence on the southern slopes of the Alps increased.     

基于SOFM网络的巴丹吉林沙漠湖泊聚类及其地下水补给来源推断

引入湖泊经纬度、海拔、湖水温度、湖水pH值以及湖水Na⁺、K⁺、Mg²⁺、Ca²⁺、Cl^-、 SO₄^2-、CO₃^2-、HCO₃^-浓度等13个基本变量作为聚类指标,构建了自组织特征映射（SOFM）网络,对巴丹吉林沙漠南部共计105个常年积水湖泊进行了非线性聚类,并与基于类平均法的线性聚类分析结果作对比,得到两种聚类分析方法的结果大体一致,即以雅布赖山北东—南西走向断裂带为界,湖泊呈较明显的二聚类分布,断裂带北部的湖泊聚集一类,接近断裂带以及断裂带南部的湖泊聚为一类,这与实地考察结果相互印证。对聚类结果进行判别后发现,SOFM网络的聚类结果更为准确可靠,其在识别地理现象微小差异方面更具优势。而根据断裂带两侧不同类型湖泊的分布,可以推断巴丹吉林沙漠南部湖泊群地下水源补给空间上的非同源性,以及地下岩层组分和结构上的空间差异性。     

Ground-water quality of the Nile west bank related to soil characteristics and geological setting

The objective of this study is to outline how the ground-water quality is affected by geological factors, soil characteristics and subsurface structure. The results of 25 ground-water samples, and 30 soil samples of which 10 soil samples analysed chemically provide the basis of this study. Procedures to interpret water quality data are based on a combined use of the traditional graphical methods, ratios of Na⁺/Cl⁻and Ca²⁺/Mg²⁺, multivariate geostatistical methods and computation of the saturation indices (SI) of minerals. The results of soil analyses show that the grain size ranges from very coarse sand to clayey loams, and from well sorted and extremely poorly sorted. The soil salinity increases in old alluvial plains and decreases in the dissected wadis of limestone plateaux, while vertical distribution decreases with depth. It is found that the ground-water is supersaturated with respect to calcite and dolomite, and undersaturated with respect to gypsum. Calculated values of P_CO2for the ground-water samples range from 2×10⁻⁴to 7×10⁻³with a mean value of 3×10⁻³(atm.). This indicates that the ground-water becomes charged with CO₂during infiltration processes.     

我国土壤中硒的淋溶

对我国8种典型土壤中硒淋溶迁移的研究表明,硒的淋溶与土壤PH呈正相关关系,与土壤中粘粒含量,Al₂O₃等倍半氧化物的含量、土壤硒的吸附系数呈负相关关系。受这些因素影响,不同土壤硒的淋溶强度不同。本文计算了天然降雨条件下不同土壤中硒的淋溶率。结果表明,土壤硒淋溶率受有机质等土壤理化性质的影响,变化范同为0.35-2.22%,其顺序为:紫色土>褐土>暗棕壤>黑钙土>黑土>红壤、砖红壤>灰钙土。比较我国低硒-克山病病带土壤与足硒-非病带土壤的硒淋溶率的差异,病带土壤中硒的淋溶率显著大于非病带土壤,这可能是病带土壤硒低的原因之一。     

A 15.4-ka paleoclimate record inferred from δ<Superscript>13</Superscript>C and δ<Superscript>15</Superscript>N of organic matter in sediments from the sub-alpine Daping Swamp,western Nanling Mountains,South China

We inferred past climate conditions from the δ¹³C and δ¹⁵N of organic matter (OM) in a sediment core (DP-2011-02) from the sub-alpine Daping Swamp, in the western Nanling Mountains, South China. In the study region, a 1000-m increase in altitude results in a ~0.75‰ decrease in δ¹³C and a ~2.2‰ increase in δ¹⁵N. Organic carbon stable isotope (δ¹³C) values of the dominant modern vegetation species, surface soils, and the core samples taken in the swamp exhibit a strong terrestrial C3 plant signature. Comprehensive analysis of the core indicates both terrestrial and aquatic sources contribute to the OM in sediment. Temperature and precipitation are most likely the critical factors that influence δ¹³C: warm and wet conditions favor lower δ¹³C, whereas a dry and cool climate leads to higher δ¹³C values. Higher δ¹⁵N values may result from greater water depth and increased primary productivity, promoted by large inputs of dissolved inorganic nitrogen, induced by high surface runoff. Lower δ¹⁵N values are associated with lower lake stage and reduced productivity, under drier conditions. Therefore, stratigraphic shifts in these stable isotopes were used to infer past regional climate. Measures of δ¹³C and δ¹⁵N in deglacial deposits, in combination with total organic carbon (TOC) and nitrogen (TN) concentrations, the TOC/TN ratio, coarse silt and sand fractions, dry bulk density and low-frequency mass magnetic susceptibility, reveal two dry and cold events at 15,400–14,500 and 13,000–11,000 cal a BP, which correspond to Heinrich event 1 and the Younger Dryas, respectively. A pronounced warm and wet period that occurred between those dry episodes, from 14,500 to 13,000 cal a BP, corresponds to the Bølling–Allerød. The δ¹³C and δ¹⁵N data, however, do not reflect a warm and wet early Holocene. The Holocene optimum occurred between ~8000 and 6000 cal a BP, which is different from inferences from the nearby Dongge cave stalagmite δ¹⁸O record, but consistent with our previous results. This study contributes to our understanding of climate-related influences on δ¹³C and δ¹⁵N in OM of lake sediments in South China.     

藏南普莫雍错流域水体离子组成与空间分布及其环境意义(英文)

The chemistry of major cations (Mg²⁺, Ca²⁺, Na⁺, and K⁺) and anions (HCO₃ ⁻, SO₄ ²⁻, and Cl⁻) in the water of Lake Pumayum Co and its inflow river was studied, revealing the obvious ionic difference among various inflow rivers and the lake. The chemical type of the lake water was Mg²⁺-Ca²⁺-HCO₃ ⁻-SO₄ ²⁺, but the major ions of the main inflow rivers were Ca²⁺-Mg²⁺-HCO₃ ⁻. In the lake inlet of Jiaqu River, the main inflow river, there was significant variance of water chemistry within the depth less than 2 m. However, it was almost homogeneous at other area of the lake. Therefore, with the evidence of distribution of water chemistry and oxygen isotope of lake water, a conclusion can be outlined that Jiaqu River had a distinct effect on the hydrochemistry of the water on the submerged delta, whereas this is not the case for other rivers. The Gibbs plot revealed that the dominant mechanism responsible for controlling chemical compositions of the lake water was rocks weathering in the drainage area. Ion ratios and ternary plots further explored the main processes controlling the water chemistry of the catchment, i.e., carbonate weathering, pyrite weathering, and silicate weathering. The different hydrochemistry characteristics between river water and lake water may result from the CaCO₃ precipitation. The findings will benefit the explanation of the environmental significance of carbonate in paleolimnological studies in the lake.     

分形方法在庐山第四纪沉积环境研究中的应用*

沉积物中Fe³⁺/Fe²⁺的值与形成时的古温度有益指数关系。假定Fe³⁺/Fe²⁺的值沿剖面的变化具有自相关性,那么它所反映的古温度变化是一条分形曲线。本文以庐山大校场剖面为例,根据孢粉和Fe³⁺/Fe²⁺的测试数据,建立了一个推算古温度的非线性公式。据此推算的古温度表明,本区中更新世以来共有3次明显的冷暖波动,最高年均温在22℃左右,最低达3℃左右,出现在末次冰期。未发现有低于0℃者。由粒度分数维的概念,推导出的计算公式可作为混杂堆积物粒度分布特征的度量指标。根据计算,该剖面主要接近于泥石流和石冰川的粒度分数维,而与冰碛物的粒度分数维有较大差别。综上得出,本区沉积物成因主要是间冰期季风气候下的山地泥石流和沟谷流水的洪-冲积及冰期干冷的冰缘环境下的冻融堆积。     

土壤中氟的淋溶研究

本文对8种土壤进行了氟的淋溶试验研究,表明不同的土壤氟的淋溶程度各不相同,氟的淋溶浓度的变化曲线也不一致。在此基础上分析了影响氟淋溶作用的因素,并讨论了淋溶出来的氟对人类健康的潜在威胁。     

Paleoenvironmental evolution of the Pliocene Villarroya Lake, northern Spain, from stable isotopes and trace-element geochemistry of ostracods and molluscs

Stable isotopes and trace-element content of calcite ostracod valves and aragonite mollusc shells from the Pliocene lacustrine succession of Villarroya allow depicting the geochemical record of environmental changes and to compare our data to the paleoenvironmental reconstruction obtained from other proxies. The lower sequences (A and B) are characterized by relatively high isotopic and Me/Ca values in the biogenic carbonates. The recorded large variations of δ¹⁸O in these carbonates mainly reflect variations in the δ¹⁸O_w due to precipitation–evaporation processes and, to a lesser extent, variations in temperature of calcification. The δ¹³C data inform about changes in DIC although they are probably biased by the vital effects of the studied taxa. Minor and trace element contents in ostracod (Mg/Ca, Sr/Ca) and mollusc shells (Sr/Ca) are mainly linked to the Me/Ca of the lake water (Me/Ca_w), and to a lesser extent to temperature and to uptake kinetic effects. Several possible mechanisms may make the Me/Ca_w to vary: long periods of Ca-carbonate (calcite, aragonite) deposition after charophyte development, and different inputs for Ca and Mg to the lake due to changes in drainage area configurations through time, including the changes in saline inputs (Na-Cl type) to the lake. The stable isotopes and the calculated Sr/Ca_w and Mg/Ca_w from sequence C display lower values than those from sequences A and B. The isotopic values from biogenic carbonates of unit C indicate isotopically diluted waters in a hydrologically open lacustrine environment. Distinct δ¹³C and δ¹⁸O plots for molluscs from unit C reflect the different biotopes and metabolism type. For several intervals of the Villarroya succession there is no direct relationships among: (i) salinity changes inferred from invertebrate paleoecology, (ii) paleoenvironmental slices based on isotopic signatures and Me/Ca_w calculations (from biogenic carbonate geochemistry) and (iii) climate in the hinterland deduced from pollen data. Lakes where geochemical behaviour is constrained by sporadic saline inputs and/or relative depletion in Ca due to long periods of Ca-carbonate precipitation or biomineralization, like the Pliocene Villarroya lake was, do not show clear correlation patterns between geochemical signals and climate proxies. In these lakes only major environmental trends display unambiguous geochemical signatures, and only some main shifts in the geochemical signature profiles may be correlated with significant global and/or regional environmental changes that have been reported from other paleoenvironmental records. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.