Low level radioactivity measurements with phoswich detectors using coincident techniques and digital pulse processing analysis

A new system has been developed for the detection of low radioactivity levels of fission products and actinides using coincidence techniques. The device combines a phoswich detector for alpha/beta/gamma-ray recognition with a fast digital card for electronic pulse analysis. The phoswich can be used in a coincident mode by identifying the composed signal produced by the simultaneous detection of alpha/beta particles and X-rays/gamma particles. The technique of coincidences with phoswich detectors was proposed recently to verify the Nuclear Test Ban Treaty (NTBT) which established the necessity of monitoring low levels of gaseous fission products produced by underground nuclear explosions. With the device proposed here it is possible to identify the coincidence events and determine the energy and type of coincident particles. The sensitivity of the system has been improved by employing liquid scintillators and a high resolution low energy germanium detector. In this case it is possible to identify simultaneously by alpha/gamma coincidence transuranic nuclides present in environmental samples without necessity of performing radiochemical separation. The minimum detectable activity was estimated to be 0.01 Bq kg(-1) for 0.1 kg of soil and 1000 min counting.     

Application of the electrochemical speciation of heavy metals in tracking groundwater pollution

The application of the electrochemical speciation of heavy metals in tracking groundwater is presented. Three fractions interchangeable, associated to the organic materials and associated to the matter in suspension of the metals Zn, Cd, Pb and Cu by means of the anodic stripping voltammetry were determined. The parameters of the determination were: electrodeposition potential ‐1.2 V, time of deaerating with nitrogen 300 s, time of the electrolysis 90 s (with stirring) and the rest time 40 s. The core of this work was to determine the validity of this scheme of electrochemical speciation in the pursuit of the follow‐up of groundwater pollution caused by heavy metals after the breakdown of the mining raft at the River Guadiamar Basin (Andalusia, Spain).     

Degradation and environmental risk of surfactants after the application of compost sludge to the soil

In this work, the degradation of anionic and non-ionic surfactants in agricultural soil amended with sewage sludge is reported. The compounds analysed were: linear alkylbenzene sulphonates (LAS) with a 10-13 carbon alkylic chain, and nonylphenolic compounds (NPE), including nonylphenol (NP) and nonylphenol ethoxylates with one and two ethoxy groups (NP1EO and NP2EO). The degradation studies were carried out under winter (12.7°C) and summer (22.4°C) conditions in Andalusia region. The concentration of LAS was reduced to 2% of the initial concentration 100 day after sludge-application to the soil. The half-life time measured for LAS homologues were ranged between 4 and 14days at 12.7°C and between 4 and 7 days at 22.4°C. With regard to NPE compounds, after 8 and 4days from the beginning of the experiment at 12.7 and 22.4°C, respectively, their concentration levels were increased to 6.5 and 13.5mg/kgdm (dry matter) as consequence of the degradation of nonylphenol polyethoxylates. These concentration levels were reduced to 5% after 63 and 70 days for 12.7°C and 22.4°C, respectively. The half-life times measured for NPEs were from 8 to 16 days at 12.7°C and from 8 to 18 days at 22.4°C. Environmental risk assessment revealed that for LAS homologues no environment risk could be expected after 7 and 8 days of sludge application to the soil for 22.4 and 12.7°C, respectively; however, potential toxic effects could be observed for the nonylphenolic compounds during the first 56 days after sludge application to the soil.     

Environmental load of Cryptosporidium parvum oocysts from cattle manure in feedlots from the central and western United States

The first step in assessing the risk of water contamination by Cryptosporidium parvum oocysts from feedlot cattle (Bos taurus) production systems is to quantify the number of C. parvum oocysts present in the fecal material deposited by feedlot cattle. Our primary objective for this project was to estimate the daily environmental load of C. parvum oocysts in fecal material deposited by feedlot cattle from across the central and western USA. Our secondary goal was to genotype isolates of C. parvum from feedlot cattle to help facilitate proper identification of mammalian sources of waterborne C. parvum. Based on 5274 fecal samples from 22 feedlots in seven states (California, Washington, Colorado, Oklahoma, Texas, Nebraska, and South Dakota), we estimated a point prevalence of C. parvum of 0.99 to 1.08% in fecal material from feedlot pens from a wide range of climates and a diverse range of feedlot management systems. On average, fresh fecal material from throughout feedlot systems (recent arrivals to nearing slaughter) contained about 1.3 to 3.6 oocysts/g feces, which roughly translates to about 2.8 x 10(4) to 1.4 x 10(5) oocysts/animal per day.     

Carbon dioxide capture from combustion flue gases with a calcium oxide chemical loop. Experimental results and process development

Post-combustion carbonate looping processes are based on the capture of carbon dioxide from the flue gases of an existing power plant in a circulating fluidized bed reactor (CFB) of calcium oxide (the carbonator) particles. The calcination of calcium carbonate in a new oxy-fired CFBC power plant regenerates the sorbent (calcium oxide particles) and obtains high purity carbon dioxide. This communication presents experimental results from a small test facility (30 kWt) operated in continuous mode using two interconnected CFB reactors as carbonator and calciner. Capture efficiencies between 70 and 97% have been obtained under realistic flue gas conditions in the carbonator reactor (temperatures around 650 °C). The similarity between process conditions and those existing in CFBC power plants should allow a rapid scaling up of this technology. The next steps for this process development are also outlined.     

Environmental quality of mussel farms in the Vigo estuary: pollution by PAHs, origin and effects on reproduction

This work analyzes the influence of environmental and physiological parameters on PAHs accumulation in cultured mussels. Lipid content and reproductive stage are directly related with PAHs accumulation pattern. We observed a rapid accumulation and depuration of PAHs, mainly during periods of nutrients accumulation, spawns and gonadic restorations. Correlations between PAHs accumulation and physiological status indicate when mussels are more susceptible to adverse effects of these pollutants. A positive correlation between mutagenic congener’s accumulation and occurrence of gonadic neoplastic disorders is shown for the first time in mussels. Molecular indices were used to identify the origin of hydrocarbons accumulated by Mytilus, showing a chronic pyrolytic pollution and pollutant episodes by petrogenic sources and biomass combustion in the studied area. Multivariate analysis suggests the possibility of including physiological parameters of sentinel organisms in environmental biomonitoring programs, mainly in aquaculture areas, taking into account their two aspects: farms productivity and human food safety.     

Plant phenology, growth and nutritive quality of Briza maxima: responses induced by enhanced ozone atmospheric levels and nitrogen enrichment

An assessment of the effects of tropospheric ozone (O₃) levels and substrate nitrogen (N) supplementation, singly and in combination, on phenology, growth and nutritive quality of Briza maxima was carried out. Two serial experiments were developed in Open-Top Chambers (OTC) using three O₃ and three N levels. Increased O₃ exposure did not affect the biomass-related parameters, but enhanced senescence, increased fiber foliar content (especially lignin concentration) and reduced plant life span; these effects were related to senescence acceleration induced by the pollutant. Added N increased plant biomass production and improved nutritive quality by decreasing foliar fiber concentration. Interestingly, the effects of N supplementation depended on meteorological conditions and plant physiological activity. N supplementation counteracted the O₃-induced senescence but did not modifiy the effects on nutritive quality. Nutritive quality and phenology should be considered in new definitions of the O₃ limits for the protection of herbaceous vegetation.     

Semifield assessment of the runoff potential and environmental risk of the parasiticide drug ivermectin under Mediterranean conditions

Introduction  

The antiparasitic ivermectin is of particular concern to regulatory agencies. Ivermectin can reach the environment through the direct emission of dung from livestock on pasture and via manure application on agricultural lands.     

Mercury, methylmercury, and selenium in blood of bird species from Doñana National Park (Southwestern Spain) after a mining accident

Total mercury (Hg), monomethylmercury (MeHg), and selenium (Se) were determined in blood of 11 bird species living in Doñana National Park (DNP, Southwestern Spain) and the surrounding area in 1999 and 2000 after a mine spill accident. The total Hg contents found varied from 1.00 to 587 ng/mL, with an MeHg percentage higher than 80 %, except in mallard species. In all the cases, the concentrations found were below the threshold of high risk for the bird populations. The parameters which most affected the accumulation of Hg and MeHg in the birds studied were, first, species, or trophic position, and second sampling area. Age does not seem to have a great influence on the content of Hg in the blood of these birds. The levels of Se found ranged from 108 to 873 ng/mL, and they were not affected by species, trophic level, age, or sampling area. The blood Hg concentrations of birds living in the area directly affected by the toxic mud, outside the park, were higher than those found in the other birds, and this could be explained by the mine spill accident happened in 1998.