A Broad-Scale Method for Estimating Natural Background Levels of Dissolved Components in Groundwater Based on Lithology and Anthropogenic Pressure

The Water Framework Directive (WFD) requires EU member states to assess the chemical status of groundwater bodies, a status defined according to threshold values for harmful elements and based on/the natural background level (NBL). The NBL is defined as the expected value of the concentration of elements naturally present in the environment. The aim of this study is to propose a methodology that will be broadly applicable to a wide range of conditions at the regional and national scale. Using a statistical approach, the methodology seeks to determine NBLs for SO4, As, Cd, Cr, Cu, Ni, Zn, and F based on the lithology of aquifers from which groundwater monitoring data were collected. The methodology was applied in six EU countries to demonstrate validity for a wide range of European regions. An average concentration was calculated for each parameter and chosen water point and linked to a lithology. Based on the dataset created, significant differences between lithologies and pressure categories (urban, agricultural, industrial, and mining) were tested using a nonparametric test. For each parameter, 90th percentiles were calculated to provide an estimation of the maximum natural concentrations possible for each lithology.

Quality change mechanism and drinking safety of repeatedly-boiled water and prolonged-boil water: a comparative study

Quality, safety and potability of repeatedly-boiled water (RBW) and prolonged-boil water (PBW) lead to concern and even misgivings in the public from time to time, especially in China, and other societies have a habit of drinking boiled water, with improvements of living standards and owing to increasing concerns for human health. This phenomenon is mainly attributed to the fact that the conclusions drawn from existing scientific experiments could not respond well to the concerns. In order to make up for this deficiency, tap water was selected to carry out RBW and PBW experiments independently. The quality changes of RBW and PBW show very similar trends that are not as great as might be imagined, and both are impacted by the tap water quality and the physiochemical effects. The dominating physiochemical effects are the water evaporation and the resulting concentration of unreactive components (most dissolved components), which can be easily explained by the existing evaporation-concentration theory. The results show that tap water will be still safe and potable after being frequently boiled or after having undergone prolonged boiling, as long as it satisfies the sanitary standards of drinking water prior to heating. Therefore, there is no need to worry about drinking RBW or PBW in daily life.

Typhoon and weathering processes on particles export to the ocean from a small river on the oceanic island of Taiwan

<p>Huge quantity of terrigenous particles was exported from oceanic island small rivers in delivering to the ocean (Dadson et al., 2003; Milliman and Syvitsky, 1992).  Quantity of river particles entering the ocean could be related to river basin area, elevation, erosion rate, and seismic activity.  However, limited data are available regarding differences between physical and chemical weathering on erosion and their effects on particles export from oceanic type of small rivers nor data on extreme event, the typhoon, and its effect on weathering at this setting. Here we report and quantify particles as well as dissolved materials export from an oceanic small river, the Lanyang River at the northeastern Taiwan, during typhoon period and those under normal weather condition.  Our objectives are to quantify river particles and dissolved components export during normal and typhoon period; to understand factors controlling their variations; to compare efficiency of chemical and physical weathering under extreme weather condition and those at normal condition.  River particles and dissolved components were sampled monthly and during typhoons at every four hours frequency and filtered, weighted for particle concentrations as well as chemical analyses of particle and dissolved compositions in lab.  Chemical analyses include solid and dissolve silica, aluminum, iron, sodium, calcium, magnesium, and potassium as well as dissolved chloride, sulfate, and alkalinity. River discharge data were from Taiwan Water Resources Agency and precipitation data from Taiwan Central Weather Bureau.</p><p> </p><p>Our results demonstrated that typhoon is the primary mechanism in driving concentration variations of both dissolved phases and solid components in the study river.  Huge amount of precipitation flushed into river during typhoon, resulting in rapid dilution of dissolved components as well as rapid increase of suspended particles concentration in reaching hyperpycnal level.  During the period of rapid increase of particles in the river, shift of types of particles as well as dissolve components were observed.  TDS (total dissolved solid) represent a small portion of the materials export to the ocean.  TSM (total suspended matter) flushed out of river during typhoon represent a major fraction (85%) of the annual total particles, however, the amount of particles for each typhoon varied significantly (from ~10 to ~45%). </p>

Methane emissions from lakes in the Alpine region: insights from two years of mobile eddy covariance flux measurements

<p>Lakes are considered an important natural source of methane (CH<sub>4</sub>). However, direct measurements of lake-atmosphere gas exchange are still sparse especially in the Alpine region. To overcome this shortcoming, we designed a mobile eddy covariance (EC) station to measure CO<sub>2</sub>, CH<sub>4</sub>, and energy fluxes at various lakes in the Alps. EC measurements were compared to flux measurements using floating chambers and related to abiotic and biotic factors like temperature, lake morphometry, dissolved components and trophic status.</p><p>During the first year, measurements were conducted at 9 lakes at different elevations ranging from 200 to 1900 m.a.s.l. to capture the spatial variability. The following year, measurements were repeated more frequently at three contrasting lakes to capture the seasonal trends of the fluxes.</p><p>The results indicate that all lakes were supersaturated with CH<sub>4</sub>. However, there was a high variability in the magnitude of CH<sub>4</sub> emissions between lakes with generally higher emissions from warmer lakes at low elevation. In particular, the lake at the lowest elevation, Lake Caldaro, had highest dissolved CH<sub>4</sub> concentrations and emissions and showed a clear seasonal trend with emissions peaking during the hot summer months. In contrast, the lake at the highest elevation, Lake Zoccolo, showed low CH<sub>4</sub> concentrations and emissions with highest concentrations in fall when the water level was low.</p>

Subduction sediment-lherzolite interaction at 2.9 GPa: effects of metasomatism and partial melting

We present the results of analogue experiments carried out in a piston–cylinder apparatus at 750–900°C and 2.9 GPa aimed to simulate metasomatic transformation of the fertile mantle caused by fluids and melts released from the subducting sediment. A synthetic H2O- and CO2-bearing mixture that corresponds to the average subducting sediment (GLOSS, Plank, Langmuir, 1998) and mineral fractions of natural lherzolite (analogue of a mantle wedge) were used as starting materials. Experiments demonstrate that the mineral growth in capsules is controlled by ascending fluid and hydrous melt (from 850°C) flows. Migration of the liquids and dissolved components develops three horizontal zones in the sedimentary layer with different mineral parageneses that slightly changed from run to run. In the general case, however, the contents of omphacite and garnet increase towards the upper boundary of the layer. Magnesite and omphacite (± garnet ± melt ± kyanite ± phengite) are widespread in the central zone of the sedimentary layer, whereas SiO2 polymorph (± kyanite ± phengite ± biotite ± omphacite ± melt) occurs in the lower zone. Clinopyroxene disappears at the base of lherzolite layer and the initial olivine is partially replaced by orthopyroxene (± magnesite) in all experiments. In addition, talc is formed in this zone at 750°C, whereas melt appears at 850°C. In the remaining volume of the lherzolite layer, metasomatic transformations affect only grain boundaries where orthopyroxene (± melt ± carbonate) is developed. The described transformations are mainly related to a pervasive flow of liquids. Mineral growth in the narrow wall sides of the capsules is probably caused by a focused flow: omphacite grows up in the sedimentary layer, and talc or omphacite with the melt grow up in the lherzolite layer. Experiments show that metasomatism of peridotite related to a subducting sediment, unlike the metasomatism related to metabasites, does not lead to the formation of garnet-bearing paragenesis. In addition, uprising liquid flows (fluid, melt) do not remove significant amounts of carbon from the metasedimentary layer to the peridotite layer. It is assumed that either more powerful fluxes of aqueous fluid or migration of carbonate-bearing rocks in subduction melanges are necessary for more efficient transfer of crustal carbon from metasediments to a mantle in subduction zones.

Granitization and high-temperature metasomatism in mafic rocks: comparison of experimental and natural data

The paper reports newly obtained data that append older results of experimental modeling of granitization processes. The experiments were aimed at modeling high-temperature metasomatism of mafic rocks, a process that involves the transfer of major components at 750°C and 500 MPa at a pressure gradient. The source of the transported Si, Ca, and Mg in the experiments was garnet. The solution was pure H2O and 25 wt % NaCl aqueous solution. In the experiments, garnet was decomposed into pyroxenes, amphiboles, plagioclase, and minor amounts of melt, ilmenite, and iron oxides. The associated partial dissolution led to the transfer and redeposition of the dissolved components on the surface of a gabbroanorthosite underlay and to the development of mineral rims, which were analogous to those produced at garnet decomposition. The compositions of the newly formed minerals in the rims were identical to those produced at metamorphism of gabbroanorthosite at Т ≥ 750°C, P > 700 MPa. When the mineral rim was formed, some elements are removed, and this process was controlled by the composition of the fluid phase. The pure H2O fluid removed Fe, Ca, and Mg. The aqueous fluid containing NaCl (XNaCl ≈ 0.1) did not extract Ca from minerals. This indicates that no high NaCl concentrations are typical of fluid in processes that form basificates at granitization. The experiments have shown that H2O and H2O-NaCl fluids remove more Fe that other elements. Preferable Fe extraction from naturally occurring associations is evident from the elevated Fe mole fractions of the mafic minerals and from the fact that the basificates typically contain magnetite and hematite.

Experimental Modeling of Silicate and Carbonate Sulfidation under Lithospheric Mantle P,T-Parameters

: Interactions of mantle silicates with subducted carbonates, sulfides, and sulfur-rich fluids are experimentally simulated in the olivine-ankerite-sulfur and olivine-ankerite-pyrite systems using a multi-anvil high-pressure split-sphere apparatus at 6.3 GPa and range of 1050–1550 °C. Recrystallization of Fe,Ni-bearing olivine and ankerite in a sulfur melt was found to be accompanied by sulfidation of olivine and carbonate, involving partial extraction of metals, carbon, and oxygen into the melt, followed by the formation of pyrite (±pyrrhotite), diopside, and Fe-free carbonates. The main features of metasomatic alteration of Fe,Ni-olivine by a reduced sulfur fluid include: (i) a zonal structure of crystals (Fe-rich core, Mg-rich rim); (ii) inclusions of pyrite and pyrrhotite in olivine; (iii) certain Raman spectral characteristics of olivine. At T > 1350 °C, two immiscible melts, a predominantly sulfur melt with dissolved components (or a Fe–Ni–S–O melt) and a predominantly carbonate one, are generated. The redox interaction of these melts leads to the formation of metastable graphite (1350–1550 °C) and diamond growth (1550 °C). The studied olivine-ankerite-sulfur and olivine-ankerite-pyrite interactions may be considered as the basis for simulation of metasomatic processes accompanied by the formation of mantle sulfides during subduction of crustal material to the silicate mantle.