Characterization on arsenic sorption and mobility of the sediments of Chia-Nan Plain, where Blackfoot disease occurred

Higher levels of arsenic in the aquifers of Chia-Nan Plain in southwestern Taiwan were attributed to the cause of Blackfoot disease in the area half a century ago. Although extensive studies were conducted on the occurrence, speciation, mobility, and transport of arsenic in the region, the relationship between arsenic adsorption by different aquifer materials and the concentration and speciation of arsenic in these aquifers was poorly delineated. This study focused on characterization of sediments in the region, as well as determination of relations between arsenic adsorption and other geochemical and clay mineralogical properties of the sediments. The arsenic adsorption capacity was positively related to the clay minerals, Fe, and Mn contents in the sediments. The higher arsenic adsorption capacity of the sediments served as a sink for the arsenic during its transport from the central mountains to the coast and as a source for its release under reduced environment and in the presence of humic substances.     

Geotechnical investigation of sewage wastewater disposal sites and use of GIS land use maps to assess environmental hazards: Sohag, upper Egypt

Land application is the only currently available technique for sewage wastewater disposal along the Nile Valley in Upper Egypt. Wastewater disposal projects have been established in the lowland desert zone extending between the cultivated floodplain and the Eocene Limestone plateau. The plan is to use the treated wastewater in irrigating woody farmlands. Some wastewater disposal sites are already operating, and several others will be established in the near future. The proposed wastewater disposal sites are located in a sensitive desert zone that is extremely narrow and situated very close to vital resources including the cultivated floodplain, reclaimed lands, residential areas, and surface water resources. In addition, the subsurface sediments of this zone (Pleistocene sand–gravel succession) constitute a significant part of the Quaternary aquifer of the valley. The objective of this study is to characterize and investigate the wastewater disposal sites and assess their probable environmental hazards. The study showed that the available lands are insufficient to accommodate the projected quantities of wastewater. At the currently operating sites, excess raw wastewater is accumulating on the ground surface forming large uncontrolled ponds. Such wastewater ponds represent a potential environmental hazard and might cause disastrous health effects, where chemical and bacteriological pollution of soil, crops and water resources may occur.     

Largemouth bass (Micropterus salmoides) and striped mullet (Mugil cephalus) as vectors of contaminants to human consumers in northwest Florida

The health benefits of regular consumption of fish and seafood have been espoused for many years. However, fish are also a potential source of environmental contaminants that have well known adverse effects on human health. We investigated the consumption risks for largemouth bass (Micropterus salmoides; n = 104) and striped mullet (Mugil cephalus; n = 170), two commonly harvested and consumed fish species inhabiting fresh and estuarine waters in northwest Florida. Skinless fillets were analyzed for total mercury, inorganic arsenic, polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/F), polychlorinated biphenyls (PCBs), and organochlorine pesticides. Contaminant levels were compared to screening values (SV) calculated using U.S. Environmental Protection Agency (EPA) recommendations for establishing consumption advisories. Largemouth bass were found to contain high levels of total mercury at all sampling locations (0.37–0.89 ug/g) and one location exhibited elevated total PCBs (39.4 ng/g). All of the samples exceeded Florida fish consumption advisory trigger levels for total mercury and one location exceeded the U.S. EPA SV for total PCBs. As a result of the high mercury levels, the non-cancer health risks (hazard index–HI) for bass were above 1 for all locations. Striped mullet from several locations with known point sources contained elevated levels of PCBs (overall range 3.4–59.3 ng/g). However, total mercury levels in mullet were low. Eight of the 16 mullet sampling locations exceeded the U.S. EPA SV for total PCBs and two locations exceeded an HI of 1 due to elevated PCBs. Despite the elevated levels of total PCBs in some samples, only two locations exceeded the acceptable cancer risk range and therefore cancer health risks from consumption of bass and mullet were determined to be low at most sampling locations.     

Micronekton abundance and biomass in Hawaiian waters as influenced by seamounts, eddies, and the moon

Micronekton abundance, biomass, and community composition was determined from 58 Cobb trawl samples taken from 2005 to 2008 at several locations in the lee of the Hawaiian Islands. The results indicated a strong influence of the lunar illumination on micronekton abundance and biomass. This effect was evident in shallow night tows and probably was the result of lunar light affecting the nighttime depths of migrating species. The abundance and biomass of micronekton is remarkably consistent between years and areas in Hawaiian waters after the affects of moon phase are accounted for. Micronekton, principally migratory myctophids, were reduced over the summit of Cross Seamount but not Finch Seamount that has a summit below the daytime depth of most migrators. However, during a new moon, micronekton abundance over Cross seamount was similar to surrounding areas either because of altered migration patterns or because predators such as tunas cannot forage as effectively at night without lunar illumination. Species belonging to the Hawaiian mesopelagic boundary layer community were found to vary in presence and abundance between years at Cross Seamount suggesting that a consistent seamount associated fauna does not exist. Sparse sampling of a cyclonic mid-ocean eddy suggested very high micronekton abundance and biomass both in shallow waters at night but also at depth during the day. Although preliminary, these results suggest that eddies may aggregate the micronekton which probably feed on the enhanced secondary productivity.     

Environmental impacts of sequestering carbon through forestation

An issue that arises when considering the potential damages of climate change is whether it is possible to slow or stop human caused climate change. One suggestion to reduce the threat of global warming is to change our management of forests to offset carbon emissions. This study examines the impacts of such a policy on environmental amenities in existing Douglas-fir forests. In this analysis Douglas-fir forest management is modelled in a Faustmann framework, where the forest produces three goods: timber, carbon sequestration and amenities. Using this framework, the level of amenities under profit-maximizing and carbon-sequestration management regimes are compared. The change in the level of seven specific amenities is modelled. These amenities include trout, wildlife diversity, visual aesthetics, soil stability, deer populations, elk populations, and water yield. The study finds that the effect of a carbon sequestration policy will depend on the discount rate chosen. In most situations externalities vary less than plus or minus ten percent. However, those externalities that exhibit discontinuities in their relationship to forest age may vary a hundred percent or more depending on the discount rate used.     

Melilitites: partial melts of the thermal boundary layer?

Silica-poor, calcium-rich melilitites form a chemical and isotopic end-member of the spectrum of mafic magmas of the Tertiary-Quaternary volcanic province of western and central Europe. We propose that these unusual magmas are derived by partial melting of the thermal boundary layer (TBL) at the base of the European lithosphere. The processes involved in the evolution of the TBL have been constrained using major and trace element and Nd-Sr-Pb isotope data for Tertiary melilitites from the Urach, Hegau, and Rhine graben regions of Germany. The initiation of boundary layer evolution is limited in time by a major phase of Permo-Carboniferous rifting and associated magmatism postdating the Hercynian orogeny which would have destroyed the existing TBL by delamination. Model calculations indicate that the isotopic composition of the melilitite source cannot develop within the TBL over geologically reasonable periods of time (250–300 Million years) if the TBL evolves solely by incorporation of small degree (<0.1%) partial melts from an underlying, convecting, depleted (MORB-source) mantle reservoir. On the basis of this observation, the regional geodynamic setting and the melilitite data, we propose that an isotopically distinct mantle plume, impinging on the base of the European lithosphere during the Early Cenozoic, is involved in the petrogenesis of the melilitite magmas.     

Satellite Measurements of Albedo and Radiant Temperature from Semi-Desert Grassland along the Arizona/Sonora Border

Along the international border separatingthe U.S. (Arizona) and Mexico (Sonora), differencesin the grazing intensity of domestic livestock arecommonly presumed to have created a large differencein vegetation cover between the two countries. Thisvegetation difference is reportedly responsible for anextensive albedo and temperature discontinuity thatmay be affecting regional climate. In this study, weused Landsat Thematic Mapper data to examinetrans-border differences in these two biophysicalparameters. Albedo and radiant temperature estimateswere computed for 25 km-long (east-west) transectsthrough semi-desert grassland on each side of theborder at two different times of year. Only smallaverage trans-border differences in these parameterswere found, and in some cases average albedo andtemperature data were essentially equal on each sideof the border. In addition, we found significantspatial heterogeneity in conditions on both sides ofthe border. These results suggest that, based on asmall sample, it may be difficult to assess whetherthere are significant differences in biophysicalproperties of semi-arid grassland between Arizona andMexico in the vicinity of the border. We concludethat more extensive spatial and temporal sampling iscritical in assessing any possible trans-borderdifferences in average terrain conditions that mightaffect climate, and that this data must be coupledwith more extensive meteorological data to assesswhether a difference in climate also exists.     

Science Needs and New Technology for Increasing Soil Carbon Sequestration

Fossil fuel use and land use change that began over 200 years ago are driving the rapid increase in atmospheric content of CO₂ and other greenhouse gases that may be impacting climatic change (Houghton et al., 1996). Enhanced terrestrial uptake of CO₂ over the next 50 to 100 years has been suggested as a way to reclaim the 150 or more Pg carbon (C) lost to the atmosphere from vegetation and soil since 1850 as a consequence of land use change (Batjes, 1999; Lal et al., 1998a; Houghton, 1995), thus effectively `buying time' for the development and implementation of new longer term technical solutions, such as C-free fuels. The ultimate potential for terrestrial C sequestration is not known, however, because we lack adequate understanding of (1) the biogeochemical mechanisms responsible for C fluxes and storage potential on the molecular, landscape, regional, and global scales, and (2) the complex genetic and physiological processes controlling key biological and ecological phenomena. Specifically, the structure and dynamics of the belowground component of terrestrial carbon pools, which accounts for two-thirds of global terrestrial organic C stocks, is poorly understood. Focusing primarily on forests, croplands and grasslands, the purpose of this chapter is to consider innovative technology for enhancing C sequestration in terrestrial ecosystems and address the scientific issues related to better understanding of soil C sequestration potential through appropriate and effective approaches to ecosystem management.