Nitrate in groundwater: an isotopic multi-tracer approach

In spite of increasing efforts to reduce nitrogen inputs into groundwater from intensive agriculture, nitrate (NO3) remains one of the major pollutants of drinking-water resources worldwide. Determining the source(s) of NO3 contamination in groundwater is an important first step for improving groundwater quality by emission control, and it is with this aim that we investigated the viability of an isotopic multi-tracer approach (delta15N, delta11B, 87Sr/86Sr), in addition to conventional hydrogeologic analysis, in two small catchments of the Arguenon watershed (Brittany, France). The main anthropogenic sources (fertilizer, sewage effluent, and hog, cattle and poultry manure) were first characterized by their specific B, N and Sr isotope signatures, and compared to those observed in the ground- and surface waters. Chemical and isotopic evidence shows that both denitrification and mixing within the watershed have the effect of buffering NO3 contamination in the groundwater. Coupled delta11B, delta15N and 87Sr/86Sr results indicate that a large part of the NO3 contamination in the Arguenon watershed originates from the spreading of animal manure, with hog manure being a major contributor. Point sources, such as sewage effluents, contribute to the NO3 budget of the two watersheds.     

Conservation of the Toromiro Tree: Case Study in the Management of a Plant Extinct in the Wild

Abstract: We reviewed the history and conservation of Sophora toromiro , a species that has been extinct in the wild since 1960 but has survived as scattered individuals in botanic gardens and private collections. The short-term conservation of S. toromiro is dependent on the management of surviving ex situ stocks. This is being achieved through international collaboration by a working group established to coordinate the conservation management of the species. Molecular evidence indicates that the species retains greater genetic variability than expected. The greatest amount of genetic variability was located in specimens outside botanic garden collections. No unmodified natural habitat survives on Rapa Nui ( Easter Island); so opportunities to establish a viable wild population are limited. Evidence from past reintroductions indicates that the best short-term opportunity for the species is through conventional horticultural management in botanic gardens and traditional farm plots on Rapa Nui. Some extinct-in-the-wild taxa (sensu World Conservation Union 1994), such as the Toromiro, retain genetic variability, and appropriate reintroduction sites exist. These taxa represent valid priorities for conservation management.     

UV-Filtersubstanzen in Wasser und Fischen

A method was developed for the analysis of fish samples to detect sunscreen agents (SSA) together with organochlorides (PCB, DDT) in different fish tissues. Detection limits of the compounds analyzed are in the range of ng/kg and vary between 40 and 90 ng/kg fillet. Recovery rates range from 78 to 104%. The contamination of water and fish with SSA in Meerfelder Maar lake, the Eifel, Germany was investigated in 1991 and 1993 and allowed the identification and quantification of six different SSA in the fish. The sum of SSA concentrations in perch taken in the summer of 1991 was 2.0 mg/kg lipid and 0.50 mg/kg lipid was found in roach sampled during the summer of 1993. Both species were contaminated with SSA and organochlorides to the same ranges as PCB and DDT. Even in the fillet of roach taken from three other lakes in Germany, methylbenzylidene camphor, a lipophilic SSA, was detected. These results indicate that SSA are wide-spread in German lakes. Therefore, they can be seen as a new group of relevant environmental chemicals. In the investigated lakes, the concentrations of the SSA in water were mostly below the detection limits. Thus, fish can be used as a biomonitor for these lipophilic compounds. Due to the lack of toxicological data for aquatic organisms, an ecotoxicological assessment is impossible at the moment.     

Near-field dispersion modeling for regulatory applications

This paper evaluates the application of dispersion models to estimate near-field pollutant concentrations in two case studies. The Industrial Source Complex Short-Term Model (ISCST3) was evaluated with hexavalent chromium measurements collected within 100 m of two facilities in Barrio Logan, San Diego, CA. ISCST3 provided reasonable estimates for higher pollutant concentrations but underestimated lower concentrations. To understand the observed distribution of concentrations in Barrio Logan, a recently conducted tracer experiment was analyzed. The tracer, sulfur hexafluoride, was released at ambient temperature from an urban facility at the University of California at Riverside, and concentrations were measured within 20 m of the source. Modeling results indicated that Industrial Source Complex-Plume Rise Model Enhancement and American Meteorological Society/U.S. Environmental Protection Agency Regulatory Model-Plume Rise Model Enhancement overestimated high concentrations and underestimated low concentrations. A diagnostic study with a simple Gaussian dispersion model that incorporated site-specific meteorology was used to evaluate model results. This study found that incorporating lateral meandering for nonbuoyant urban plumes in Gaussian dispersion models could improve concentration estimates even when downwash is not considered. Incorporating a meandering component in ISCST3 resulted in improvements in estimating hexavalent chromium concentrations in Barrio Logan. Credible near-source concentration estimates depend on accurate characterization of emissions, onsite micrometeorology, and a method to account for lateral meandering in the near field.     

Biochar reduces copper toxicity in Chenopodium quinoa Willd. In a sandy soil

Mining, smelting, land applications of sewage sludge, the use of fungicides containing copper (Cu), and other human activities have led to widespread soil enrichment and contamination with Cu and potentially toxic conditions. Biochar (BC) can adsorb several substances, ranging from herbicides to plant-inhibiting allelochemicals. However, the range of potential beneficial effects on early-stage plant growth with regard to heavy metal toxicity is largely unexplored. We investigated the ameliorating properties of a forestry-residue BC under Cu toxicity conditions on early plant growth. Young quinoa plants () were grown in the greenhouse in the presence of 0, 2, and 4% BC application (w/w) added to a sandy soil with 0, 50, or 200 μg g Cu supplied. The plants without BC showed severe stress symptoms and reduced growth shortly after Cu application of 50 μg g and died at 200 μg Cu g. Increasing BC concentrations in the growth medium significantly increased the plant performance without Cu toxicity or under Cu stress. At the 4% BC application rate, the plants with 200 μg g Cu almost reached the same biomass as in the control treatment. In the presence of BC, less Cu entered the plant tissues, which had reduced Cu concentrations in the order roots, shoots, leaves. The amelioration effect also was reflected in the plant-soil system CO gas exchange, which showed clear signs of improvement with BC presence. The most likely ameliorating mechanisms were adsorption of Cu to negatively charged BC surfaces and an improvement of the water supply. Overall, BC seems to be a beneficial amendment with the potential to ameliorate Cu toxicity in sandy soils. Further research with a broad spectrum of different soil types, BCs, and crop plants is required.