Geochemical fractionation of metals and metalloids in tailings and appraisal of environmental pollution in the abandoned Musina Copper Mine,South Africa

The economic benefits of mining industry have often overshadowed the serious challenges posed to the environments through huge volume of tailings generated and disposed in tailings dumps. Some of these challenges include the surface and groundwater contamination, dust, and inability to utilize the land for developmental purposes. The abandoned copper mine tailings in Musina (Limpopo province, South Africa) was investigated for particle size distribution, mineralogy, physicochemical properties using arrays of granulometric, X-ray diffraction, and X-ray fluorescence analyses. A modified Community Bureau of Reference (BCR) sequential chemical extraction method followed by inductively coupled plasma mass spectrometry/atomic emission spectrometry (ICP-MS/AES) technique was employed to assess bioavailability of metals. Principal component analysis was performed on the sequential extraction data to reveal different loadings and mobilities of metals in samples collected at various depths. The pH ranged between 7.5 and 8.5 (average?≈?8.0) indicating alkaline medium. Samples composed mostly of poorly grated sands (i.e. 50% fine sand) with an average permeability of about 387.6 m/s. Samples have SiO₂/Al₂O₃ and Na₂O/(Al₂O₃?+?SiO₂) ratios and low plastic index (i.e. PI?≈?2.79) suggesting non-plastic and very low dry strength. Major minerals were comprised of quartz, epidote, and chlorite while the order of relative abundance of minerals in minor quantities is plagioclase?>?muscovite?>?hornblende?>?calcite?>?haematite. The largest percentage of elements such as As, Cd and Cr was strongly bound to less extractable fractions. Results showed high concentration and easily extractable Cu in the Musina Copper Mine tailings, which indicates bioavailability and poses environmental risk and potential health risk of human exposure. Principal component analysis revealed Fe-oxide/hydroxides, carbonate and clay components, and copper ore process are controlling the elements distribution.     

Recent shoreline evolution and beach erosion along the central Adriatic coast of Italy: the case of Molise region

A study on the modern dynamics and shoreline changes from 1954 to 2014 of the Molise coast (central Adriatic Sea) has been carried out. Short to long-term shoreline changes and associated surface area variations have been assessed in GIS environment for the study coast, subdivided in nine coastal segments (S1-S9), by using 100-m regularly spaced transects. In addition, the possible influence of natural and anthropogenic factors, especially of climatic variability and engineered shoreline defense structures, has been investigated. The Molise coast has experienced notable long-term erosion (period 1054-2014) that caused an overall coastal land loss of approximately 940,000 m². Erosion was, yet, limited to coastal segments S1 and S7, nearest to the mouths of major rivers, namely Trigno and Biferno, while the major part of the study coast has remained essentially stable or even advanced. Increased shoreline protection by defense structures has generally favoured shoreline stability and frequently generated shoreline advance, except for segments S1 and S7. Observed differences in shoreline change rates over time at the decadal to interannual scale, have not find a response in the analysis of available data on meteo-marine conditions of the Molise coast and climate variability indices, pointing out the need to improve knowledge on meteomarine conditions and on climatic variability forcing of the study area. From 2004 to 2014, the Molise shoreline remained essentially stable. Nonetheless, most recent shoreline changes (period 2011-2014) and modern shoreline dynamics indicate that erosion has become more widespread, involving at least part of segments S2-S3 and S8-S9, located south of the river mouth segments. The localized long-term shoreline retreat and most recent shoreline erosion appear to be primarily related to channel adjustments of the Biferno and Trigno rivers that occurred since the 1950s under the control of human interventions on the rivers, especially the construction respectively of a dam and a check dam along their lower courses, that trap of most of their solid load, affecting so adversely the sediment budget of the river mouths areas and adjacent beaches. Overall data acquired on the recent shoreline evolution and modern shoreline dynamics of the Molise coast and on related causal factors provide a good basic knowledge for regional coastal management purposes, and for further scientific purposes. Particularly, they suggest the opportunity to deepen a number of aspects such as the relationship between the coast and river catchments feeding it, the possible influences on the Molise shoreline dynamics of the neighbouring coasts, the efficiency/obsolescence of defense structures and the present-day vulnerability to coastal erosion of the Molise coast.     

Fate of imidacloprid in soil and plant after application to cotton seeds

This study aimed to investigate the persistence of imidacloprid in soil after application to cotton seeds and to obtain a complete picture on the mass balance of this compound in soil and cotton plants. The study was carried out as a pot culture experiment under laboratory conditions using a Gaucho formulation containing ¹⁴C-labeled imidacloprid. Three treatments of cotton seeds were made in sandy loamy soil: live seeds grown in autoclaved soil, dead seeds put in live soil and live seeds grown in live soil. Results showed that total ¹⁴C recoveries decreased by time ranging 93.8–96.2, 77.1–88.4 and 53.5–62.4% of the applied radioactivity at 7, 14, and 21 d after application, respectively. The reduction in the extracted ¹⁴C from soil coincided with the increase of non-extracted ones. Levels of bound ¹⁴C was always less in autoclaved soil than in live ones. Results revealed also that only 1.8–6.8% of the applied ¹⁴C was taken up by the plants and fluctuated within the test period. ¹⁴C levels were higher in plants grown in autoclaved soil than those in live ones and the radioactivity tended to accumulate on the edges of cotton leaves. Most of the radioactivity in the soil extracts was identified as unchanged ¹⁴C-imidacloprid.     

Neurotoxic effect and metabolic responses induced by a mixture of six pesticides on the earthworm Aporrectodea caliginosa nocturna

The effects of a mixture of insecticides and/or fungicides at different environmental concentrations were investigated on a Aporrectodea caliginosa nocturna population. This laboratory experiment was carried out in order to reproduce Gaillac (France) vineyard conditions. Neurotoxicity (cholinesterase), metabolisation (glutathione-S-transferase) and oxidative stress (catalase) enzymes were studied as biomarkers in earthworms after short-term exposure in terraria. The aim was to observe the global effects of pesticide exposure, as in a vineyard, rather than focus on each isolated biomarker variation, or on each compound's impact. ChE activity was inhibited after a few days of insecticide and/or fungicide exposure, indicative of a neurotoxic effect in earthworms. The significant increase in GST and CAT activities revealed the metabolisation of these products resulting in the production of reactive oxygen species. After a long period of exposure or high concentrations, earthworms were physiologically damaged: they could not cope with the high toxicity (cellular dysfunction, protein catabolism...). Chemical analysis showed that pesticide bioaccumulation in earthworm tissues, even in those exposed to the highest concentrations and for the longest periods, was very low (under LOD) or absent. However, the study of pesticide residues in terraria after 34 days in a climate chamber suggested that earthworms participate in soil pesticide breakdown.     

Humic substances

GOAL, SCOPE AND BACKGROUND: Freshwater bodies which chemistry is dominated by dissolved humic substances (HS) seem to be the major type on Earth, due to huge non-calcareous geological formations in the Northern Hemisphere and in the tropics. Based on the paradigm of the inertness of being organic, direct interactions of dissolved HS with freshwater organisms are mostly neglected. However, dissolved organic carbon, the majority of which being HS, are natural environmental chemicals and should therefore directly interact with organisms. Major results that widened our perspective on humic substance ecology come from experiments with the compost nematode, Caenorhabditis elegans, which behaved contradictorily to textbook knowledge and provoked an in-depth re-consideration of some paradigms. APPROACH: To overcome old paradigms on HS and their potential interactions with organisms, we reviewed recent international literature, as well as 'grey' literature. We also include results from own ongoing studies. RESULTS: This review focuses on direct interactions of dissolved HS with freshwater organisms and disregards indirect effects, such as under-water light quenching. Instead we show with some macrophyte and algal species that HS adversely interfere with photosynthesis and growth, whereby closely related algal species show different response patterns. In addition to this, HS suppress cyanobacteria more than eukaryotic algae. Quinones in the HS appear to be the effective structure. Furthermore, HS can modulate the offspring numbers in the nematode C. elegans and cause feminization of fish and amphibians--they possess hormone-like properties. The ecological consequences of this potential remain obscure at present. HS also have the potential to act as chemical attractants as shown with C. elegans and exert a mild chemical stress upon aquatic organisms in many ways: induction of molecular chaperons (stress proteins), induction and modulation of biotransformation and anti-oxidant enzymes. Furthermore, they produce an oxidative stress with lipidperoxidation as one clear symptom or even stress defense strategy. Stronger chemical stresses by HS may even lead to teratogenic effects as shown with fish embryos; all physiological responses to HS-mediated stress require energy, which were compensated on the expense of yolk as shown with zebra fish embryos. One Finnish field survey supports the view of a strong chemical stress, as the weight yield in fish species decreases with increasing HS content in the lakes. DISCUSSION: HS exert a variety of stress symptoms in aquatic and compost organisms. According to current paradigms of ecotoxicology, these symptoms have to be considered adverse, because their compensation consumes energy which is deducted from the main metabolism. However, the nematode C. elegans looks actively for such stressful environments, and this behavior is only understandable in the light of new paradigms of aging mechanisms, particularly the Green Theory of Aging. In this respect, we discuss the mild HS-mediated stress to aquatic and compost organisms. New empirical findings with HS themselves and HS building blocks appear to be consistent with this emerging paradigm and show that the individual lifespan may be expanded. At present the ecological consequences of these findings remain obscure. However, a multiple-stress resistance may be acquired which improves the individual fitness in a fluctuating environment. CONCLUSIONS: It appears that dissolved HS have to be considered abiotic ecological driving forces, somewhat less obvious than temperature, nutrients, or light. PERSPECTIVES: The understanding of the ecological control by dissolved humic substances is still fragmentary and needs to be studied in more details.     

An enzyme-linked immunosorbent assay for the determination of dioxins in contaminated sediment and soil samples

A 96-microwell enzyme-linked immunosorbent assay (ELISA) method was evaluated to determine PCDDs/PCDFs in sediment and soil samples from an EPA Superfund site. Samples were prepared and analyzed by both the ELISA and a gas chromatography/high resolution mass spectrometry (GC/HRMS) method. Comparable method precision, accuracy, and detection level (8 ng kg(-1)) were achieved by the ELISA method with respect to GC/HRMS. However, the extraction and cleanup method developed for the ELISA requires refinement for the soil type that yielded a waxy residue after sample processing. Four types of statistical analyses (Pearson correlation coefficient, paired t-test, nonparametric tests, and McNemar's test of association) were performed to determine whether the two methods produced statistically different results. The log-transformed ELISA-derived 2,3,7,8-tetrachlorodibenzo-p-dioxin values and log-transformed GC/HRMS-derived TEQ values were significantly correlated (r=0.79) at the 0.05 level. The median difference in values between ELISA and GC/HRMS was not significant at the 0.05 level. Low false negative and false positive rates (<10%) were observed for the ELISA when compared to the GC/HRMS at 1,000 ng TEQ kg(-1). The findings suggest that immunochemical technology could be a complementary monitoring tool for determining concentrations at the 1,000 ng TEQ kg(-1) action level for contaminated sediment and soil. The ELISA could also be used in an analytical triage approach to screen and rank samples prior to instrumental analysis.     

Changes in sewage sludge carbon forms along a treatment stream

The behaviour and fate of macronutrients and pollutants in sewage sludge applied to the land are affected by the chemical composition of the sludge organic matter, which in turn is influenced by both sewage source and by sewage treatment processes. In this study, (13)C nuclear magnetic resonance (NMR) spectroscopy was used to characterise the organic matter of sludges collected at three different points along the treatment stream of a municipal sewage works with a domestic catchment. Sludge at the first point, an undigested liquid (UL) sludge, had a substantially different composition to the anaerobically digested (AD) and dewatered sludge cake (DC) materials, which were similar to each other. In particular, the UL sludge contained more alkyl C than the AD or DC sludges. All three sludges were found to contain mobile alkyl C that is poorly observed using the cross polarisation (CP) technique, necessitating the use of the less sensitive, but more quantitatively reliable direct polarisation (DP) technique to obtain accurate distributions of C types.     

Empirical and simulated critical loads for nitrogen deposition in California mixed conifer forests

Empirical critical loads (CL) for N deposition were determined from changes in epiphytic lichen communities, elevated NO(3)(-) leaching in streamwater, and reduced fine root biomass in ponderosa pine (Pinus ponderosa Dougl. ex Laws.) at sites with varying N deposition. The CL for lichen community impacts of 3.1kg ha(-1) year(-1) is expected to protect all components of the forest ecosystem from the adverse effects of N deposition. Much of the western Sierra Nevada is above the lichen-based CL, showing significant changes in lichen indicator groups. The empirical N deposition threshold and that simulated by the DayCent model for enhanced NO(3)(-)leaching were 17kg N ha(-1) year(-1). DayCent estimated that elevated NO(3)(-) leaching in the San Bernardino Mountains began in the late 1950s. Critical values for litter C:N (34.1), ponderosa pine foliar N (1.1%), and N concentrations (1.0%) in the lichen Letharia vulpina ((L.) Hue) are indicative of CL exceedance.     

Influence of Na2S on the degradation kinetics of CCl4 in the presence of very pure iron

This paper presents the results of kinetic studies to investigate the effect of FeS film formation on the degradation rate of CCl(4) by 99.99% pure metallic iron. The film was formed by submersing metallic iron grains in an oxygen free HCO(3)(-)/CO(3)(2-) electrolyte solution. When the grains had reached a quasi steady-state value of the corrosion potential, Na(2)S((aq)) was injected. Upon injection, a microm thick poorly crystalline FeS film formed immediately on the iron surface. Over time, the iron became strongly corroded and both the FeS film and the metallic iron grains began to crack leading to exposure of bare metallic iron to the solution. The effect of the surface film on the degradation rate of CCl(4) was investigated following four periods of aging, 1, 10, 30, and 60 days. Relative to the controls, the 1-day sulfide-aged iron showed a substantial decrease in rate of degradation of CCl(4.) However, over time, the rate of degradation increased and surpassed the degradation rate obtained in the controls. It has been proposed that CCl(4) is reduced to HCCl(3) by metallic iron by electron transfer. The FeS film is substantially less conducting than the bulk iron metal or non-stoichiometric magnetite and from the results of this study, greatly decreases the rate of CCl(4) degradation relative to iron that has not been exposed to Na(2)S. However, continued aging of the FeS film results in breakdown and stress-induced cracking of the film, followed by dissolution and cracking of the iron itself. The cracking of the bulk iron is believed to be a consequence of hydrogen embrittlement, which is promoted by sulfide. The increase in CCl(4) degradation rate, as the FeS films age, suggests that the process of hydrogen cracking increases the surface area available for charge transfer.     

The effect of nitroaromatics' composition on their toxicity in vivo: novel, efficient non-additive 1D QSAR analysis

Novel 1D QSAR approach that allows analysis of non-additive effects of molecular fragments on toxicity has been proposed. Twenty-eight nitroaromatic compounds including some well-known explosives have been chosen for this study. The 50% lethal dose concentration for rats (LD50) was used as the estimation of toxicity in vivo to develop 1D QSAR models on the framework of Simplex representation of molecular structure. The results of 1D QSAR analysis show that even the information about the composition of molecules provides the main trends of toxicity changes. The necessity of consideration of substituents' mutual impacts for the development of adequate QSAR models of nitroaromatics' toxicity was demonstrated. Statistic characteristics for all the developed partial least squares QSAR models, except the additive ones are quite satisfactory (R2=0.81-0.92; Q2=0.64-0.83; R2 test=0.84-0.87). A successful performance of such models is due to their non-additivity i.e. possibility of taking into account the mutual influence of substituents in benzene ring which plays the governing role for toxicity change and could be mediated through the different C-H fragments of the ring. The correspondence between observed and predicted by these models toxicity values is good. This allowing combine advantages of such approaches and develop adequate consensus model that can be used as a toxicity virtual screening tool.