N. Farella

Effects of Recent Human Colonization on the Presence of Mercury in Amazonian Ecosystems

Three Hg sources were characterised and mass balance calculations were used to determine their relative contributions to the contamination of the Amazonian environment. About an order of magnitude more Hg is emitted to the atmosphere by goldmining activity than by the burning of forest biomass. However, anthropogenic atmospheric Hg cannot account for the high Hg burdens found in terrestrial ecosystems: deposition of Hg from goldmining sources is estimated to account for less than 3% of the Hg present in the surface horizons of soils. We propose that erosion of deforested soils following human colonization constitutes a major disturbance of the natural Hg cycle. Deforestation thus increases soil Hg mobilisation by runoff, which may explain the increase of Hg burdens in Amazonian aquatic ecosystems in newly colonized watersheds.

The geochemistry of mercury in central Amazonian soils developed on the Alter-do-Chão formation of the lower Tapajós River Valley, Pará state, Brazil.

In an oxisol-spodosol system developed on the terrestrial surface of the lower Tapajós Valley, the determination of total mercury (Hg), organic carbon (C), iron and aluminum oxy-hydroxide (Fe(cdb) and Al(cdb)) concentrations in the surface soil horizons are used to characterise the geochemical processes controlling the accumulation of Hg in soils under natural vegetation cover and in deforested and cultivated sites. Oxisols from the plateau have homogeneous and relatively high background Hg contents and burdens constituting an important natural reservoir of Hg for the region (90-210 ng/g dry wt. and 19-33 mg/m2 for the first 20 cm). The Fe(cdb) and Al(cdb) contents associated with the fine fraction (< 63 microns) of the soil suggest that oxy-hydroxides and, particularly Al-substituted Fe oxy-hydroxides, control the Hg concentrations observed in all of the soils of the study region. Consequently, the geochemistry of these minerals along the slopes governs the accumulation or the release of the Hg according to the natural evolution of the soil cover and/or following the degradation of soils by erosion after deforestation and cultivation. These observations have important implications for the interpretation of Hg contamination patterns observed in Amazonian aquatic systems that could be linked to different drainage sources of Hg from the terrestrial surface. The sandification and podzolisation that is characteristic of the evolution of numerous pedological systems in the equatorial Amazon could be responsible for exportation of the naturally accumulated Hg, as for other metals, by acidic complexation and migration to the black waters of the Amazon. In the central Amazon region, as a result of the fragility of the soil cover, deforestation and cultivation, affecting principally the superficial soil, promote the selective erosion of fine particles enriched in oxides and Hg. The erosion of soil could be responsible for an important release of Hg, transported in particulate form by drainage waters.

Deforestation modifying terrestrial organic transport in the Rio Tapajos, Brazilian Amazon

The concentration and biomarker compositions of sedimentary organic matter (OM) as well as fine and coarse sus- pended particles were analysed to identify the impact of deforestation on the transport of terrigenous organic matter (OM) in the Rio Tapajos, a major tributary to the Amazon. Substantial shifts in the concentration and composition of recently deposited sedimentary OM suggest that intensive deforestation over the last few decades has considerably modified the natural inputs of sedimentary materials to the aquatic ecosystems by disrupting the terrigenous fluxes of humus and soil materials from the drainage basin. The observed compositional changes of bulk OM and land derived biomarkers (e.g. lignin) in recent sediments illustrate a sedimentary enrichment in OM from soil horizons that, under normal forest cover, tend to be retained in the drainage basin. On average, the recently accumulated OM is nitrogen- rich ((C/N)a=12-15) and more highly degraded ((Ac/Al)v=0.4-0.6 and DHBA/V=0.15-0.20) than deep materials ((C/N)a=20-30, (Ac/Al)v=0.25-0.4, and DHBA/V=0.05-0.10), showing that this recently accumulated material is more humified than original inputs to the aquatic system, and consistent with increased exportation of fine eroded mineral and organic particles from surface soils along river banks. The present study illustrates the relevance of using OM oxidation products in sediment profiles to evaluate deforestation impacts on aquatic ecosystems and to characterize the nature of eroded soil materials, complementing studies on mineral/metal cycling. # 2001 Elsevier Science Ltd. All rights reserved.

Historical and geographical variations of sources and transport of terrigenous organic matter within a large-scale coastal environment

Abstract Elemental and molecular analyses indicate that the sources and inputs of terrigenous organic matter (OM) to the upper St. Lawrence system have been influenced by increased discharges of industrial solid organic wastes from the pulp and paper industry following its expansion in the 1920–1940s. Moderately altered lignin-rich particles from a combination of natural and anthropogenic sources predominate within recent sediments of this system, with anthropogenic fractions ranging 10–70% and 2–30% for the Fjord and the Lower Estuary, respectively. Compositional and isotopic signatures of sedimentary OM show that the sediments within the Lower Estuary are dominated by inputs of allochthonous OM (60–80%), whereas terrigenous OM inputs are minor (15–30%) sources of OM to the Gulf/Shelf sediments. In this latter environment, the terrigenous OM pool is composed exclusively of highly altered lignin-poor soil OM with no substantial influence from anthropogenic lignin. A global mass balance calculation suggests that about half of the global annual riverine flux is degraded, leaving only the remaining half to accumulate predominantly (98%) within shelf and slope sediments. This estimate suggests that lignin does not behave conservatively within the marine environment but supports some sort of organic matter degradation.

Contributions to the International Forum on Ecosystem Approaches to Human Health

In her opening statement to the participants of the May 2003 International Forum on Ecosystem Approaches to Human Health, Dr. Gro Harlem Brundtland captured an increasingly prominent sentiment: human health must be understood in context, and as a foundation for sustainable development. Ecosystem approaches to human health (Ecohealth) attempt to make this sentiment a reality. Consolidating the myriad experiences, successes, challenges, and knowledge that result from using them provided the impetus for the International Development Research Centre (IDRC) and the Universite de Quebec a Montreal (UQAM) to jointly organize an international Forum, which brought together 358 participants representing donors, government representatives, academic institutions, nongovernmental organizations (NGOs), and researchers from 42 countries. It provided an opportunity for different stakeholders to discuss the Ecohealth framework and its relevance to improving human health and well-being, as well as to explore the implications of evidence from the field. Discussions at the Forum were built around four themes. The first, definition and conceptualization, emphasized the need to develop concepts that can be broadly defined and applied from a transdisciplinary perspective, to achieve a holistic understanding of the links between ecosystems and human health. Building on this need, the case studies theme provided descriptions and analysis of ongoing research projects to examine the application of concepts in different contexts. The third theme, linking research to policy, explored the reality that the Ecohealth approach is a research paradigm with a strong commitment to changing human behavior and organization, and therefore requires the effective translation of research results into policy. The final theme, institutionalization, focused on building individual, institutional, funding, and community capacity, in order to implement, manage, and sustain the research or its resulting interventions. This supplementary issue demonstrates that Ecohealth approaches push us in the right direction for sustainable development, and make improved health an achievable outcome. It is hoped that in addition to presenting an overview of the most prominent issues arising from the Forum, these pieces will stimulate debate, foster dialogue, and contribute to the development of an emerging community of practice in Ecohealth.