Magnesium as Environmental Tracer for Karst Spring Baseflow/Overflow Assessment—A Case Study of the Pertuso Karst Spring (Latium Region, Italy)

Following a previous research carried out on the same site, this paper presents the update of the Mg2+ based method for the estimation of Pertuso Spring discharge, located in Central Italy. New collected data confirmed the validity of the proposed model and the conservative behaviour of Mg2+ for groundwater related to the Pertuso Spring aquifer. Further analysis allowed to obtain a local linear relationship between magnesium concentration and total spring discharge (including exploitation rate), regardless of the mixing model proposed with the Aniene River. As regards two samples which fall out of the linear relationship and could have been detected as “outliers”, more in-depth data processing and sensitivity analyses revealed that the lowering in magnesium, at equal discharges, is determined by the appearance of the quick-flow component, less mineralized and related to storm events. Results showed that under specific conditions, related to the absence or presence of previous intense rainfall events, Mg2+ could be effectively a useful tracer for separating spring conduit flow (overflow) from diffuse flow (baseflow) within the karst aquifer.

Pacific climate reflected in Waipuna Cave drip water hydrochemistry

Cave microclimate and geochemical monitoring is vitally important for correct interpretations of proxy time series from speleothems with regard to past climatic and environmental dynamics. We present results of a comprehensive cave-monitoring programme in Waipuna Cave in the North Island of New Zealand, a region that is strongly influenced by the Southern Westerlies and the El Niño–Southern Oscillation (ENSO). This study aims to characterise the response of the Waipuna Cave hydrological system to atmospheric circulation dynamics in the southwestern Pacific region in order to assure the quality of ongoing palaeo-environmental reconstructions from this cave. Drip water from 10 drip sites was collected at roughly monthly intervals for a period of ca. 3 years for isotopic (δ18O, δD, d-excess parameter, δ17O, and 17Oexcess) and elemental (Mg∕Ca and Sr∕Ca) analysis. The monitoring included spot measurements of drip rates and cave air CO2 concentration. Cave air temperature and drip rates were also continuously recorded by automatic loggers. These datasets were compared to surface air temperature, rainfall, and potential evaporation from nearby meteorological stations to test the degree of signal transfer and expression of surface environmental conditions in Waipuna Cave hydrochemistry. Based on the drip response dynamics to rainfall and other characteristics, we identified three types of discharge associated with hydrological routing in Waipuna Cave: (i) type 1 – diffuse flow, (ii) type 2 – fracture flow, and (iii) type 3 – combined flow. Drip water isotopes do not reflect seasonal variability but show higher values during severe drought. Drip water δ18O values are characterised by small variability and reflect the mean isotopic signature of precipitation, testifying to rapid and thorough homogenisation in the epikarst. Mg∕Ca and Sr∕Ca ratios in drip waters are predominantly controlled by prior calcite precipitation (PCP). Prior calcite precipitation is strongest during austral summer (December–February), reflecting drier conditions and a lack of effective infiltration, and is weakest during the wet austral winter (July–September). The Sr∕Ca ratio is particularly sensitive to ENSO conditions due to the interplay of congruent or incongruent host rock dissolution, which manifests itself in lower Sr∕Ca in above-average warmer and wetter (La Niña-like) conditions. Our microclimatic observations at Waipuna Cave provide a valuable baseline for the rigorous interpretation of speleothem proxy records aiming at reconstructing the past expression of Pacific climate modes.

Nutrient Losses to the Siverskyi Donets and Dniestr River Basins (Ukraine)

<p>For the quantitative assessment of the circulation of fluxes, the differentiation between point, quasi-stationary sources and diffuse, non-stationary sources play a significant role. The firsts include municipal and industrial wastewater discharges. The flow of substances from diffuse sources depends substantially on the landscape characteristics of the basin, water runoff, etc. In contrast to point sources, which always have an anthropogenic origin, the diffuse flow is associated with both natural processes and the influence of human activity.</p><p>The aim of this work was to estimate the diffuse flow within the Ukrainian part of the Severskyi Donets and Dniester basins. The focus was on evaluating the nutrients emission, among which nitrogen and phosphorus compounds were considered.</p><p>To quantify nutrient emissions from point and diffuse sources the special conceptual approach was proposed. It was a simple method for the first assessment which didn’t require detailed initial information and was based on the catchment characteristics, export coefficients and statistical data.</p><p>The Dniester basin is located in Eastern Europe and flows through Ukraine and Moldova into the Black Sea. According to the natural conditions it’s divided into 3 separate parts: Upper Carpathian, Middle Podil and Lower Dniester.</p><p>The main nitrogen pollution in the Dniester basin is caused by diffuse sources of agricultural origin. Their share in Podil Upland (about 80%) and Low part (about 90%) significantly exceeds the corresponding values in the Upper Dniester of 60%. This is due to the fact of occupying by forests about 30% of the slopes of this mountain part.</p><p>About 30% of the total phosphorus emission is formed within the Upper Carpathian part.  Municipal discharged and agricultural territories approximately equally determined this load. On the contrary within the plain territory the role of agriculture was dominant and increased from the middle to the lower part of the Dniester river - from 55 to 75%.</p><p>The Siversky Donets basin is located on the southwestern slope of the Central Russian Upland within forest-steppe and steppe zones. One of the features of this basin is the extremely high level of cultivation resulting significantly water pollution. More than 78% of the territory is covered by agricultural lands, what is much large compare to many European countries, where it does not exceed 35%. This is due to the dominance within the Siverskyi Donets basin of the most fertile chernozem soils. Disruption of the soil cover due to plowing led to significant nutrient losses due to deflation and water runoff.</p><p>More than 80% nitrogen emission are strongly affected by arable lands. The rest of the factors have a negligible impact. Compare to nitrogen the dominant part of phosphorus load comes to rivers as solid particles due to erosion processes - 56% and 36% - due to agriculture.</p>