Description: The rate of non-oxidative galena dissolution in seawater compositions over the pH range of 2–4.5 was determined from batch reactor experiments. The derivative at zero time of a polynomial fit of the Pb concentration versus time data for the first 30 min was used to determine the rate. A plot of R Gn (rate of galena dissolution) versus pH for data from six experiments is linear ( R 2  = 0.96), with a slope of 0.5. The rate equation describing the rate of galena dissolution as a function of hydrogen ion activity is $$R_{\text{Gn}} = - \,10^{ - 10.72} \left( {a_{{{\text{H}}^{ + } }} } \right)^{0.50}$$ Varying the concentration of dissolved oxygen produced no significant effect on the measured rates. The activation energy, based on four experiments carried out over the temperature range of 7–30 °C, is 61.1 kJ/mol.

Description: In the original publication of the article, Figs. 3 and 4 were interchanged. Now the correct figures have been provided in this erratum.

Description: Interactions of the microbial mat community with the sedimentary environment were evaluated in two shallow, ephemeral lakes with markedly different hydrochemistry and mineralogy. The characterization of growing and decaying microbial mats by light microscopy observations and fluorescence in situ hybridization was complemented with biogeochemical and mineralogical measurements. The lakes studied were Eras and Altillo Chica, both located in Central Spain and representing poly-extreme environments. Lake Eras is a highly alkaline, brackish to saline lake containing a high concentration of chloride, and in which the carbonate concentration exceeds the sulfate concentration. The presence of magnesium is crucial for the precipitation of hydromagnesite in microbialites of this lake. Altillo Chica is a mesosaline to hypersaline playa lake with high concentrations of sulfate and chloride, favoring the formation of gypsum microbialites. Differences in the microbial community composition and mineralogy of the microbialites between the two lakes were primarily controlled by alkalinity and salinity. Lake Eras was dominated by the cyanobacterial genus Oscillatoria , as well as Alphaproteobacteria, Gammaproteobacteria and Firmicutes. When the mat decayed, Alphaproteobacteria and Deltaproteobacteria increased and became the dominant heterotrophs, as opposed to Firmicutes. In contrast, Deltaproteobacteria was the most abundant group in Lake Altillo Chica, where desiccation led to mats decay during evaporite formation. In addition to Deltaproteobacteria, Cyanobacteria, Actinobacteria, Alphaproteobacteria and Gammaproteobacteria were found in Altillo Chica, mostly during microbial mats growth. At both sites, microbial mats favored the precipitation of sulfate and carbonate minerals. The precipitation of carbonate is higher in the soda lake due to a stronger alkalinity engine and probably a higher degradation rate of exopolymeric substances. Our findings clarify the distribution patterns of microbial community composition in ephemeral lakes at the levels of whole communities, which were subjected to environmental conditions similar to those that may have existed during early Earth.

Description: We report the vertical and horizontal distributions of inorganic iodine (iodide and iodate) and their related species (bromide nitrate and nitrite) in the Seto Inland Sea, which is a semi-enclosed coastal sea area of western Japan. In this study, ion chromatography with ultraviolet detection was employed to determine the iodide, iodate, bromide nitrate, and nitrite levels simultaneously in a single run. Iodide was higher at inshore sites than at offshore sites. Vertical profiles showed that iodide increased in the bottom layer of inshore sites of Osaka Bay and Hiroshima Bay, but were low in the bottom layer of the Kii Channel, the main channel connecting Osaka Bay with the Pacific Ocean. Iodates were low in the low-salinity inshore surface, but were high in the bottom layer of the Kii Channel. The riverine flux of iodine to the coastal marine environment was negligible. The vertical profiles of total inorganic iodine (iodide + iodate) looked uniform; however, plots of total inorganic iodine versus salinity demonstrated a net loss of total inorganic iodine in the low-salinity inshore surface. The iodine distributions in the Seto Inland Sea could be explained by three-end-member mixing, with one member being non-iodine river water, another high-salinity and high-iodate water of the open ocean, and the final high-iodide and low-iodate inland water with a salinity of around 32–33.

Description: We report here for the first time rainwater organic carbon (OC) concentration and composition collected from open waters over the Gulf of Mexico. Rainwater OC concentrations ranged from 3.7 to 17.3 mg L −1 . The δ 13 C of these rainwater samples ranged from −26.7 to −24.2‰ pointing toward terrestrial and/or fossil fuel OC sources (64–100%) combined with marine OC sources. Colored dissolved OM absorbance and EEM fluorescence spectra were indicative of secondary organic aerosol from terrestrial sources as well as aromatic fossil fuel compounds. Air mass back trajectory analyses along with these results indicate that rainwater OC in the Gulf of Mexico may be influenced by oil and gas infrastructure and emissions from known lanes of shipping traffic within the Gulf. These results also suggest that anthropogenic and biogenic emissions from the southeastern continental USA impact rainwater OC in the Gulf of Mexico.

Description: Combined assessments from different methodologies, including hydrogeochemical analysis, multivariate statistics and stable isotopes, were used in order to characterize the groundwater resources of a heterogeneous aquifer system in central Greece and to evaluate the overall environmental regime. Results outlined the driving factors that chiefly control groundwater chemistry and delineated the major pathways of groundwater flow. Following the results of the combined assessments, hydrogeochemistry is influenced both by geogenic and anthropogenic factors including the geological substrate, intense agricultural activities and ongoing geochemical processes which impact the concentrations of redox sensitive agents like NO 3 , Fe, Mn and SO 4 . Stable isotope evaluations supplemented the above assessments by providing critical information for the hydrodynamics of the heterogeneous aquifer system. Evaporation is the main factor influencing the isotopic composition of water resources, in addition to the slow percolation rates of the thick unsaturated zone. Comparisons between δ 18 Ο and δ D values for surface and groundwater samples revealed an interaction among water systems through the developed karstic network and/or the riverbeds of higher permeabilities. Eventually, the integrated conceptual approach of diverse methodologies was applied successfully for the identification of hydrogeological and hydrogeochemical assessments in the case of Kopaida basin; evaluations were cross-confirmed and supplemented when needed, hence providing essential information for strategic planning and water resources management.

Description: The source, quantity and quality of sedimentary organic matter (SOM) were investigated in the surface sediments of Lake Fuxian, a deep oligotrophic lacustrine system in China. Granulometry, biochemical organic composition, bulk organic proxies and their stable isotopes were determined in the surface sediments (0–4 cm). The values of δ 13 C, δ 15 N and atomic ratio of total organic carbon to total nitrogen (TOC/TN) indicated that the sediments in the large partial lake were influenced by autochthonous organic matter. The concentrations of TOC, protein (PRT) and total hydrolysable amino acids may be mainly modulated by phytodetritus sinking from euphotic zones since they correlated significantly with chlorins. Otherwise, the lack of correlation between chlorins concentrations and carbohydrate (CHO) and lipid (LIP) indicated that the latter may have an additional terrestrial source. The highest sediment quantity was found in the deepest station NC owing to its fine sediment. Stations near northwestern shore accumulated more SOM than other littoral stations, which was in accordance with sewage discharge strength. Degradation quality indices, such as chlorin index, degradation index, PRT/CHO, and LIP/CHO, were in general agreement in showing the degraded status of SOM in Lake Fuxian. No clear spatial patterns were found in sediment degradation quality, which may be influenced by bottom oxygen concentration in the deep stations.

Description: Maharlu Lake with Na–Cl water type is the terminal point of a closed basin in southern Iran. A total of 10 water samples from two rivers discharging to the lake and 78 water samples of surface and pore brine of Maharlu Lake have been collected from different depths (surface, 20, 50 and 100 cm) of four sampling stations along the lake during a period of lake water-level fluctuation (November 2014–July 2015). To investigate chemical interaction between lake surface water and shallow pore water and to understand the major factors governing chemical composition of Maharlu brine, concentrations of major and minor (boron, bromide and lithium) solutes, pH and total dissolved solids have been measured in collected water samples. Saturation indices of evaporite minerals in collected water samples have been also calculated. The chemical behavior of dissolved solutes and evaporative evolution of the lake brine during a hydrological period have been simulated using PHREEQC. The results of our investigations indicated that chemical composition of lake surface water and pore brine of Maharlu Lake are mainly connected with lake water-level fluctuations and distance from input rivers (and depth), respectively. Hydrochemical investigations and statistical analysis showed that the brines chemistry of Maharlu is mainly controlled by three processes: brine evaporative evolution, dissolution–precipitation and diagenetic evolution of secondary carbonates.