The rocket (Euruca sativa) is an important vegetable in human´s feed and one of the most nutritious, rich in minerals such as potassium, sulfur and iron, and vitamins A and C. Since the late 90’s the rocket is gaining more market, with an increase in quantity sold, and its area planted. The aim for this study is to assess the effect of potassium on the yield characteristics, SPAD reading and efficiency in water use by plants of rocket. The experiment was conducted in a greenhouse during May-June 2011. The experimental plot consisted of vase built by PET 2.5 liter bottle with a capacity of 1 dm-3 of soil, using a wool wick for irrigation by capillary. The experimental design was completely randomized and its treatments consisted of six doses ofK2O: 0; 50; 100; 150; 200 and 250 mg dm-3 and using as source KCl and six replications. The variables analyzed were SPAD readings, leaf number, fresh mass, dry mass, root dry mass and water use efficiency. The potassium fertilization increases the SPAD reading and water use efficiency by rocket plants in potassium doses of 156.4 and 200 mg dm-3, respectively. Variables fresh and dry mass of plants are influenced by potassium fertilization with adjust of linear regression model. Variables number of leaves and root dry weight are not influenced by potassium fertilization.ResumoA rúcula (Euruca sativa) é uma hortaliça relevante na alimentação humana sendo uma das mais nutritivas, ricas emminerais como potássio, enxofre e ferro, além das vitaminas A e C. Desde o final da década de 90 a rúcula vem conquistandomercado com um aumento na quantidade comercializada e na sua área de plantio. Objetivou-se pelo presente estudo avaliaro efeito de doses de potássio nas características produtivas, leitura SPAD e eficiência no uso da água por plantas de rúcula.O experimento foi realizado em casa de vegetação no período de maio a junho de 2011. A parcela experimental consistiu devaso construído por garrafa PET de 2,5 litros, com capacidade para 1 dm-3 de solo, utilizando-se pavio de lã para irrigação porcapilaridade. O delineamento experimental foi inteiramente casualizado cujos tratamentos consistiram de seis doses de K2O: 0;50; 100; 150; 200 e 250 mg dm-3 utilizando-se como fonte o KCl e seis repetições. As variáveis analisadas foram leitura SPAD,número de folhas, massa fresca e massa seca da parte aérea, massa seca da raiz e eficiência no uso da água. A adubação compotássio aumenta a leitura SPAD e a eficiência no uso de água por plantas de rúcula nas doses de potássio de 156,4 e 200 mg dm-3,respectivamente. As variáveis massas fresca e seca de plantas são influenciadas pela adubação potássica com ajuste a modelolinear de regressão. As variáveis número de folhas e massa seca de raiz não são influenciadas pela adubação potássica.

La material seca nodular (MSN) y el nitrógeno acumulado (N-acum.) en el cultivo de soja fueron evaluados en función del sistema de labranza [siembra directa (SD) y labranza convencional (LC)] y la disponibilidad de azufre (S). Para ello, se realizaron en Balcarce durante la campaña 2002-03 dos experimentos, uno conducido bajo riego (Ri) y otro en secano (Se). La MSN determinada en R5 no fue afectada por la aplicación de S (P>0.10), sin embargo fue mayor bajo SD en Se (P<0,05). Bajo Ri la MSN fue mayor en SD que en LC, siendo dichas diferencias no significativas. El N-acum no fue afectado por la fertilización azufrada y bajo condiciones de Se fue significativamente mayor en LC (P<0,05). El N-acum se relacionó positivamente con la MSN, sin embargo el r² fue bajo (36%) sugiriendo que no es en único factor involucrado en la regulación de la fijación biológica del nitrógeno. | Nodular dry matter (NDM) and accumulated nitrogen (AN) in a soybean crop were evaluated as a function of tillage system [no-tillage (NT) and conventional tillage(CT)] and sulfur (S) availability in two experiments carried out under irrigation (Ri) and rainfed conditions (Se). The experiment was carried out at Balcarce in the 2002-2003 growing season. The NDM, determined at R5 stage, was not affected by S fertilization (P>0.10) but was higher under NT in Se (P< 0.05). Under Ri NDM was higher under NT but this difference was not significant. The AN was not affected by S fertilization, and under rainfed conditions, it was significantly lower (P<0.05) under CT. The AN was positively related with NDM but the r² value was low (36%), suggesting that NDM was not the only factor regulating biological N2-fixation.

La material seca nodular (MSN) y el nitrógeno acumulado (N-acum.) en el cultivo de soja fueron evaluados en función del sistema de labranza [siembra directa (SD) y labranza convencional (LC)] y la disponibilidad de azufre (S). Para ello, se realizaron en Balcarce durante la campaña 2002-03 dos experimentos, uno conducido bajo riego (Ri) y otro en secano (Se). La MSN determinada en R5 no fue afectada por la aplicación de S (P>0.10), sin embargo fue mayor bajo SD en Se (P<0,05). Bajo Ri la MSN fue mayor en SD que en LC, siendo dichas diferencias no significativas. El N-acum no fue afectado por la fertilización azufrada y bajo condiciones de Se fue significativamente mayor en LC (P<0,05). El N-acum se relacionó positivamente con la MSN, sin embargo el r² fue bajo (36%) sugiriendo que no es en único factor involucrado en la regulación de la fijación biológica del nitrógeno.<br>Nodular dry matter (NDM) and accumulated nitrogen (AN) in a soybean crop were evaluated as a function of tillage system [no-tillage (NT) and conventional tillage(CT)] and sulfur (S) availability in two experiments carried out under irrigation (Ri) and rainfed conditions (Se). The experiment was carried out at Balcarce in the 2002-2003 growing season. The NDM, determined at R5 stage, was not affected by S fertilization (P>0.10) but was higher under NT in Se (P< 0.05). Under Ri NDM was higher under NT but this difference was not significant. The AN was not affected by S fertilization, and under rainfed conditions, it was significantly lower (P<0.05) under CT. The AN was positively related with NDM but the r² value was low (36%), suggesting that NDM was not the only factor regulating biological N2-fixation.

Geothermal resources are practical and competitive clean-energy alternatives to fossil fuels, and study on the recharge sources of geothermal water supports its sustainable exploitation. In order to provide evidence on the recharge source of water and circulation dynamics of the Tangshan Geothermal System (TGS) near Nanjing (China), a comprehensive investigation was carried out using multiple chemical and isotopic tracers (δ²H, δ¹⁸O, δ³⁴S, ⁸⁷Sr/⁸⁶Sr, δ¹³C, ¹⁴C and ³H). The results confirm that a local (rather than regional) recharge source feeds the system from the exposed Cambrian and Ordovician carbonate rocks area on the upper part of Tangshan Mountain. The reservoir temperature up to 87 °C, obtained using empirical as well as theoretical chemical geothermometers, requires a groundwater circulation depth of around 2.5 km. The temperature of the geothermal water is lowered during upwelling as a consequence of mixing with shallow cold water up to a 63% dilution. The corrected ¹⁴C age shows that the geothermal water travels at a very slow pace (millennial scale) and has a low circulation rate, allowing sufficient time for the water to become heated in the system. This study has provided key information on the genesis of TGS and the results are instructive to the effective management of the geothermal resources. Further confirmation and even prediction associated with the sustainability of the system could be achieved through continuous monitoring and modeling of the responses of the karstic geothermal reservoir to hot-water mining.

With depleted coal resources or deteriorating mining geological conditions, some coal mines have been abandoned in the Fengfeng mining district, China. Water that accumulates in an abandoned underground mine (goaf water) may be a hazard to neighboring mines and impact the groundwater environment. Groundwater samples at three abandoned mines (Yi, Er and Quantou mines) in the Fengfeng mining district and the underlying Ordovician limestone aquifer were collected to characterize their chemical and isotopic compositions and identify the sources of the mine water. The water was HCO₃·SO₄-Ca·Mg type in Er mine and the auxiliary shaft of Yi mine, and HCO₃·SO₄-Na type in the main shaft of Quantou mine. The isotopic compositions (δD and δ¹⁸O) of water in the three abandoned mines were close to that of Ordovician limestone groundwater. Faults in the abandoned mines were developmental, possibly facilitating inflows of groundwater from the underlying Ordovician limestone aquifers into the coal mines. Although the Sr²⁺ concentrations differed considerably, the ratios of Sr²⁺/Ca²⁺ and ⁸⁷Sr/⁸⁶Sr and the ³⁴S content of SO₄²⁻ were similar for all three mine waters and Ordovician limestone groundwater, indicating that a close hydraulic connection may exist. Geochemical and isotopic indicators suggest that (1) the mine waters may originate mainly from the Ordovician limestone groundwater inflows, and (2) the upward hydraulic gradient in the limestone aquifer may prevent its contamination by the overlying abandoned mine water. The results of this study could be useful for water resources management in this area and other similar mining areas.

Recently collected naturally occurring geochemical and isotopic groundwater tracers were combined with historic data from the Pahute Mesa area of the Nevada National Security Site (NNSS), Nevada, USA, to provide insights into long-term regional groundwater flow patterns, mixing and recharge. Pahute Mesa was the site of 85 nuclear detonations between 1965 and 1992, many of them deeply buried devices that introduced radionuclides directly into groundwater. The dataset examined included major ions and field measurements, stable isotopes of hydrogen (δ²H), oxygen (δ¹⁸O), carbon (δ¹³C) and sulfur (δ³⁴S), and radioisotopes of carbon (¹⁴C) and chloride (³⁶Cl). Analysis of the patterns of groundwater ¹⁴C data and the δ²H and δ¹⁸O signatures indicates that groundwater recharge is predominantly of Pleistocene age, except for a few localized areas near major ephemeral drainages. Steep gradients in sulfate (SO₄) and chloride (Cl) define a region near the western edge of the NNSS where high-concentration groundwater flowing south from north of the NNSS merges with dilute groundwater flowing west from eastern Pahute Mesa in a mixing zone that coincides with a groundwater trough associated with major faults. The ³⁶Cl/Cl and δ³⁴S data suggest that the source of the high Cl and SO₄ in the groundwater was a now-dry, pluvial-age playa lake north of the NNSS. Patterns of groundwater flow indicated by the combined data sets show that groundwater is flowing around the northwest margin of the now extinct Timber Mountain Caldera Complex toward regional discharge areas in Oasis Valley.