Radon hazard in shallow groundwaters II: dry season fracture drainage and alluvial fan upwelling

Inorganic contaminants from diffuse pollution in shallow groundwater of the Campanian Plain (Southern Italy). Implications for geochemical survey

The Campanian Plain (CP) shallow aquifer (Southern Italy) represents a natural laboratory to validate geochemical methods for differentiating diffuse anthropogenic pollution from natural water-rock interaction processes. The CP is an appropriate study area because of numerous potential anthropogenic pollution vectors including agriculture, animal husbandry, septic/drainage sewage systems, and industry. In order to evaluate the potential for geochemical methods to differentiate various contamination vectors, 538 groundwater wells from the shallow aquifer in Campanian Plain (CP) were sampled. The dataset includes both major and trace elements. Natural water-rock interactions, which primarily depend on local lithology, control the majority of geochemical parameters, including most of the major and trace elements. Using prospective statistical methods in combination with the traditional geochemical techniques, we determined the chemical variables that are enriched by anthropogenic contamination (i.e. NO3, SO4 and U) by using NO3 as the diagnostic variable for detecting polluted groundwater. Synthetic agricultural fertilizers are responsible for the majority of SO4 and U pollution throughout the CP area. Both SO4 and U are present in the groundmass of synthetic fertilizers; the uranium concentration is specifically applicable as a tracer for non-point source agricultural fertilizer contamination. The recognition of non-geological (anthropogenic) inputs of these elements has to be considered in the geochemical investigations of contaminated aquifers.

Dynamics of soil gas radon concentration in a highly permeable soil based on a long-term high temporal resolution observation series

This paper studies the temporal variation of soil gas radon activity concentration in a highly permeable (k = 2.0E-11 m(2)) sandy-gravelly soil in order to understand if temporal variation of soil gas radon activity concentration can affect geogenic radon potential determination. Geogenic radon potential provides information about the potential risk from radon. Its calculation takes into account the equilibrium, saturated at infinite depth, soil gas radon activity concentration (c∞). This concentration may vary at annual time scale due to the environmental conditions. A long-term (yearly) and high temporal resolution (15 min) observation, applied in this study, reveal various temporal features such as long-term trend, seasonality, daily periodicity and sudden events in soil gas radon time series. Results show seasonal and daily periodical variation of the measured soil gas radon activity concentration (csoilRn) in a highly permeable sandy-gravelly soil with definite seasons without obvious long transitional periods. The winter (from October 2010 to April 2011) is characterized by 2.5 times higher average soil gas radon activity concentration (median is 7.0 kBq m(-3)) than the summer (August, September 2010 and May, June, July 2011) (median is 2.8 kBq m(-3)). Daily periodicity, which is much less than the seasonal one, controls the soil gas radon activity concentration mainly in the summer season. Average (AM) value of csoilRn is higher at night than in the daytime with about 18% and 3.8% in summer and in winter, respectively. As a conclusion, in case of single csoilRn measurement on a highly permeable (k ≥ 2.0E-11 m(2)) soil, similar to our test site, csoilRn should be corrected according to the seasons for calculating the equilibrium activity concentration c∞ value.

Impact of volcanic plume emissions on rain water chemistry during the January 2010 Nyamuragira eruptive event: implications for essential potable water resources

On January 2, 2010 the Nyamuragira volcano erupted lava fountains extending up to 300 m vertically along an ~1.5 km segment of its southern flank cascading ash and gas on nearby villages and cities along the western side of the rift valley. Because rain water is the only available potable water resource within this region, volcanic impacts on drinking water constitutes a major potential hazard to public health within the region. During the 2010 eruption, concerns were expressed by local inhabitants about water quality and feelings of physical discomfort (e.g. nausea, bloating, indigestion, etc.) after consuming rain water collected after the eruption began. We present the elemental and ionic chemistry of drinking water samples collected within the region on the third day of the eruption (January 5, 2010). We identify a significant impact on water quality associated with the eruption including lower pH (i.e. acidification) and increases in acidic halogens (e.g. F(-) and Cl(-)), major ions (e.g. SO(4)(2-), NH(4)(+), Na(+), Ca(2+)), potentially toxic metals (e.g. Al(3+), Mn(2+), Cd(2+), Pb(2+), Hf(4+)), and particulate load. In many cases, the water's composition significantly exceeds World Health Organization (WHO) drinking water standards. The degree of pollution depends upon: (1) ash plume direction and (2) ash plume density. The potential negative health impacts are a function of the water's pH, which regulates the elements and their chemical form that are released into drinking water.

Measuring effective radium concentration with less than 5 g of rock or soil

Radon generation in natural systems and building materials is controlled by the effective radium concentration EC(Ra), product of the radium concentration C(Ra) and the emanation factor E. An experimental method is proposed to measure EC(Ra) in the laboratory by radon accumulation experiments using less than 5 g of sample inserted in 125 mL scintillation flasks. Accumulation curves with fine temporal resolution can be obtained, allowing the simultaneous determination of the effective leakage rate. The detection limit, defined as the EC(Ra) value giving a probability larger than 90% for a determination with a one-sigma uncertainty better than 50%, is moderate, varying from 2 to 5 Bq kg(-1) depending on the conditions. Obtained punctual uncertainties on EC(Ra) vary from about 10 to 20% at 10 Bq kg(-1) to less than 3% for EC(Ra) larger than 500 Bq kg(-1). The representativity of small samples to estimate meaningful values at site or system level is, however, a definite limitation of the method, and the sample dispersion needs to be considered carefully in every case. Nevertheless, the value obtained with 5 g or less differs on average by 9 ± 13% from the value given by standard methods using 100 g or more, thus is sufficiently reliable for most applications. When EC(Ra) is sufficiently large, the temperature sensitivity of EC(Ra) can be measured reliably with this method, with obtained mean values ranging from 0.39 ± 0.05% °C(-1) for Compreignac granite, to 2.8 ± 0.2% °C(-1) for La Crouzille pitchblende, both from the centre of France. This method is useful to study dedicated problems, such as the small scale variability of EC(Ra), and in circumstances when only a small amount of sample is available, for example from remote areas or from precious materials such as historical building stones.