Leaching of cyanogenic glucosides and cyanide from white clover green manure

Use of crops for green manure as a substitute for chemical fertilizers and pesticides is an important approach towards more sustainable agricultural practices. Green manure from white clover is rich in nitrogen but white clover also produces the cyanogenic glucosides (CGs) linamarin and lotaustralin; CGs release toxic hydrogen cyanide (HCN) upon hydrolysis which may be utilized for pest control. We demonstrate that applying CGs in the form of a liquid extract of white clover to large columns of intact agricultural soils can result in leaching of toxic cyanide species to a depth of at least 1m. Although degradation of the CGs during leaching proceeded with half lives in the interval 1.5-35 h depending on soil characteristics, a fraction of the applied CGs (0.9-3.2%) was recovered in the leachate as either CGs or toxic cyanide species. Detoxification of the HCN formed was rapid in soil and leachate from both sandy and loamy soil. However, 30% of the leachate samples exceeded the EU threshold value of 50 micrgl(-1) total cyanide for drinking water and 85% exceeded the US threshold of 5 micrgl(-1) for cyanide chronic ecotoxicity in fresh water. This study demonstrates that even easily degradable natural products present in crop plants as defense compounds pose a threat to the quality of groundwater and surface waters. This aspect needs consideration in assessment of the risk associated with use of crops as green manure to replace chemical fertilizers and pesticides as well as in genetic engineering approaches to design crops with improved pest resistance.     

Assessment of the natural-cultural resources in Çanakkale for nature-based tourism

While the world is going into different tourism expectations, the tourism understanding in Turkey is defined as tourism in the sea-sand-sun triangle. However, it is possible to contribute to the income and local development of the indigenous people by developing nature-based tourism. Besides, with the sustainable use and preservation of the natural-cultural assets, the damage of the traditional tourism industry on the natural and cultural environment could be reduced. In this study, it is aimed to bring up the nature-based tourism concept in Çanakkale by evaluating the nature-based tourism industry in the general of Turkey and assessing the natural-cultural resources that Çanakkale comprehends. The most important areas that have a nature-based tourism potential in Çanakkale and the tourism activities that are most suitable for these areas have been determined.     

Soil and vegetation carbon stocks in Brazilian Western Amazonia: relationships and ecological implications for natural landscapes

The relationships between soils attributes, soil carbon stocks and vegetation carbon stocks are poorly know in Amazonia, even at regional scale. In this paper, we used the large and reliable soil database from Western Amazonia obtained from the RADAMBRASIL project and recent estimates of vegetation biomass to investigate some environmental relationships, quantifying C stocks of intact ecosystem in Western Amazonia. The results allowed separating the western Amazonia into 6 sectors, called pedo-zones: Roraima, Rio Negro Basin, Tertiary Plateaux of the Amazon, Javari-Juruá-Purus lowland, Acre Basin and Rondonia uplands. The highest C stock for the whole soil is observed in the Acre and in the Rio Negro sectors. In the former, this is due to the high nutrient status and high clay activity, whereas in the latter, it is attributed to a downward carbon movement attributed to widespread podzolization and arenization, forming spodic horizons. The youthful nature of shallow soils of the Javari-Juruá-Purus lowlands, associated with high Al, results in a high phytomass C/soil C ratio. A similar trend was observed for the shallow soils from the Roraima and Rondonia highlands. A consistent east–west decline in biomass carbon in the Rio Negro Basin sector is associated with increasing rainfall and higher sand amounts. It is related to lesser C protection and greater C loss of sandy soils, subjected to active chemical leaching and widespread podzolization. Also, these soils possess lower cation exchangeable capacity and lower water retention capacity. Zones where deeply weathered Latosols dominate have a overall pattern of high C sequestration, and greater than the shallower soils from the upper Amazon, west of Madeira and Negro rivers. This was attributed to deeper incorporation of carbon in these clayey and highly pedo-bioturbated soils. The results highlight the urgent need for refining soil data at an appropriate scale for C stocks calculations purposes in Amazonia. There is a risk of misinterpreting C stocks in Amazonia when such great pedological variability is not taken into account.     

Canopy Spectra and Remote Sensing of Ashe Juniper and Associated Vegetation

A study was conducted in central Texas to determine the potential of using remote sensing technology to distinguish Ashe juniper (Juniperus ashei Buchholz) infestations on rangelands. Plant canopy reflectance measurements showed that Ashe juniper had lower near-infrared reflectance than other associated woody plant species and lower visible reflectance than mixed herbaceous species in spring and summer. Ashe juniper could be distinguished on color-infrared aerial photographs acquired in March, April, June, and August and on QuickBird false color satellite imagery obtained in June, where it had a distinct dark reddish-brown tonal response. Unsupervised classification techniques were used to classify aerial photographic and satellite imagery of study sites. An accuracy assessment performed on a computer classified map of a photographic image showed that Ashe juniper had producer's and user's accuracies of 100% and 92.9%, respectively, whereas an accuracy assessment performed on a classified map of a satellite image of the same site showed that Ashe juniper had producer's and user's accuracies of 94.1% and 88.1%, respectively. Accuracy assessments performed on classified maps of satellite images of two additional study sites showed that Ashe juniper had producer's and user's accuracies that ranged from 87.1% to 96.4%. These results indicate that both color-infrared photography and false color satellite imagery can be used successfully for distinguishing Ashe juniper infestations.     

The gill symbiont of the hydrothermal vent mussel Bathymodiolus thermophilus is a psychrophilic,chemoautotrophic, sulfur bacterium

Certain hydrothermal vent invertebrates, e.g. Riftia pachyptila and Calyptogena magnifica, are clearly established as harboring dense populations of chemoautotrophic sulfur bacteria in specialized tissues. By contrast, the physiological characteristics of the abundant intracellular gill symbiont of the vent mussel Bathymodiolus thermophilus have been questioned. The low activities of enzymes diagnostic for CO₂ fixation (Calvin cycle) and for sulfur-driven energy generation, as measured by other investigators, have been attributed to bacterial contamination of the gill surface. Based on research at the Galápagos Rift hydrothermal vents in 1988 and subsequent laboratory experiments, the current study confirms that the B. thermophilus symbiont is a psychrophile for which thiosulfate and sulfide stimulate CO₂ fixation. It strongly indicates that the symbiont is a chemoautotroph by establishing the following: (1) Sulfide and thiosulfate can stimulate CO₂ fixation by partially purified symbionts by up to 43-fold and 120-fold, respectively; (2) the ribulose-1,5-bisphosphate carboxylase/oxygenase activity of the symbiont is sufficient to account for its sulfide- or thiosulfate-stimulated CO₂ incorporation; (3) the symbiont's molar growth yield on thiosulfate, as judged by CO₂ incorporation, is indistinguishable from that of free-living chemoautotrophs. Due to the high protein-degrading activity of B. thermophilus gill lysate, it is also suggested that host lysis of symbionts plays a more important role in the nutrition of the vent mussel than in R. pachyptila or C. magnifica, for which no comparable protein-degrading activity was found.     

ARSENIC CONSUMPTION AND HEALTH RISK PERCEPTIONS IN A RURAL WESTERN U.S. AREA1

ABSTRACT: Churchill County, Nevada, has approximately 23,000 residents, among whom an estimated 13,500 relied on private wells for water supply in 2002. This study examined exposure to arsenic in water supplies among residents with private domestic wells and factors related to householder choice to consume tap water. It compared opinions and concerns about water quality with consumption habits and observed concentrations from tap water samples. The results from 351 households indicated that a majority (75 percent) of respondents consumed tap water and that a minority (38 percent) applied treatment. Approximately 66 percent of those who consumed tap water were exposed to concentrations of arsenic that exceeded 10 ppb. Water consumption was related to application of treatment. Among 98 respondents who were not at all concerned about the health effects of aqueous arsenic, 59 (60 percent) reported consuming tap water with concentrations of arsenic exceeding 10 ppb. Conversely, among 86 respondents who were highly concerned about arsenic, 33 (37 percent) consumed tap water with concentrations of arsenic exceeding 10 ppb. Results from a national sampling effort showed that 620 of 5,304 private wells sampled (11.7 percent) had arsenic concentrations above 10 ppb. The paradox of awareness of arsenic in water supplies coupled with consumption of aqueous arsenic in concentrations greater than 10 ppb may be common in other parts of the nation. Enhanced educational efforts, especially related to tap water sampling and explanations of efficacy of available treatment, may be useful means of reducing exposure through private water supplies.