Photoinduced reactivity of titanium dioxide

Summary
The soil is important in sequestering atmospheric CO2 and in emitting trace gases (e.g. CO2, CH4 and N2O) that are radiatively active and enhance the ‘greenhouse’ effect. Land use changes and predicted global warming, through their effects on net primary productivity, the plant community and soil conditions, may have important effects on the size of the organic matter pool in the soil and directly affect the atmospheric concentration of these trace gases.

A discrepancy of approximately 350 × 1015 g (or Pg) of C in two recent estimates of soil carbon reserves worldwide is evaluated using the geo-referenced database developed for the World Inventory of Soil Emission Potentials (WISE) project. This database holds 4353 soil profiles distributed globally which are considered to represent the soil units shown on a 1/2° latitude by 1/2° longitude version of the corrected and digitized 1:5 M FAO–UNESCO Soil Map of the World.

Total soil carbon pools for the entire land area of the world, excluding carbon held in the litter layer and charcoal, amounts to 2157–2293 Pg of C in the upper 100 cm. Soil organic carbon is estimated to be 684–724 Pg of C in the upper 30 cm, 1462–1548 Pg of C in the upper 100 cm, and 2376–2456 Pg of C in the upper 200 cm. Although deforestation, changes in land use and predicted climate change can alter the amount of organic carbon held in the superficial soil layers rapidly, this is less so for the soil carbonate carbon. An estimated 695–748 Pg of carbonate-C is held in the upper 100 cm of the world's soils. Mean C: N ratios of soil organic matter range from 9.9 for arid Yermosols to 25.8 for Histosols. Global amounts of soil nitrogen are estimated to be 133–140 Pg of N for the upper 100 cm. Possible changes in soil organic carbon and nitrogen dynamics caused by increased concentrations of atmospheric CO2 and the predicted associated rise in temperature are discussed.

https://library.wur.nl/isric/fulltext/isricu_t47d6414d_001.pdf

Total carbon and nitrogen in the soils of the world

Acid mine drainage remediation options: a review

Biogeochemistry of the Human Environment.- The Biosphere.- Soils.- Waters.- Air.- Plants.- Humans.- Biogeochemistry of Trace Elements.- Trace Elements of Group 1 (Previously Group Ia).- Trace Elements of Group 2 (Previously Group IIa).- Trace Elements of Group 3 (Previously Group IIIb).- Trace Elements of Group 4 (Previously Group IVb).- Trace Elements of Group 5 (Previously Group Vb).- Trace Elements of Group 6 (Previously Group VIb).- Trace Elements of Group 7 (Previously Group VIIb).- Trace Elements of Group 8 (Previously Part of Group VIII).- Trace Elements of Group 9 (Previously Part of Group VIII).- Trace Elements of Group 10 (Previously Part of Group VIII).- Trace Elements of Group 11 (Previously Group Ib).- Trace Elements of Group 12 (Previously Group IIb).- Trace Elements of Group 13 (Previously Group IIIa).- Trace Elements of Group 14 (Previously Group IVa).- Trace Elements of Group 15 (Previously Group Va).- Trace Elements of Group 16 (Previously Group VIa).- Trace Elements of Group 17 (Previously Group VIIa).

/pdf/trace-elements-from-soil-to-human-gyujylwhl8.pdf

Trace Elements From Soil to Human

Mangroves are woody plants that grow at the interface between land and sea in tropical and sub-tropical latitudes where they exist in conditions of high salinity, extreme tides, strong winds, high temperatures and muddy, anaerobic soils. There may be no other group of plants with such highly developed morphological and physiological adaptations to extreme conditions.

Because of their environment, mangroves are necessarily tolerant of high salt levels and have mechanisms to take up water despite strong osmotic potentials. Some also take up salts, but excrete them through specialized glands in the leaves. Others transfer salts into senescent leaves or store them in the bark or the wood. Still others simply become increasingly conservative in their water use as water salinity increases Morphological specializations include profuse lateral roots that anchor the trees in the loose sediments, exposed aerial roots for gas exchange and viviparous waterdispersed propagules.

Mangroves create unique ecological environments that host rich assemblages of species. The muddy or sandy sediments of the mangal are home to a variety of epibenthic, infaunal, and meiofaunal invertebrates Channels within the mangal support communities of phytoplankton, zooplankton and fish. The mangal may play a special role as nursery habitat for juveniles of fish whose adults occupy other habitats (e.g. coral reefs and seagrass beds).

Because they are surrounded by loose sediments, the submerged mangroves' roots, trunks and branches are islands of habitat that may attract rich epifaunal communities including bacteria, fungi, macroalgae and invertebrates. The aerial roots, trunks, leaves and branches host other groups of organisms. A number of crab species live among the roots, on the trunks or even forage in the canopy. Insects, reptiles, amphibians, birds and mammals thrive in the habitat and contribute to its unique character.

Living at the interface between land and sea, mangroves are well adapted to deal with natural stressors (e.g. temperature, salinity, anoxia, UV). However, because they live close to their tolerance limits, they may be particularly sensitive to disturbances like those created by human activities. Because of their proximity to population centers, mangals have historically been favored sites for sewage disposal. Industrial effluents have contributed to heavy metal contamination in the sediments. Oil from spills and from petroleum production has flowed into many mangals. These insults have had significant negative effects on the mangroves.

Habitat destruction through human encroachment has been the primary cause of mangrove loss. Diversion of freshwater for irrigation and land reclamation has destroyed extensive mangrove forests. In the past several decades, numerous tracts of mangrove have been converted for aquaculture, fundamentally altering the nature of the habitat. Measurements reveal alarming levels of mangrove destruction. Some estimates put global loss rates at one million ha y−1, with mangroves in some regions in danger of complete collapse. Heavy historical exploitation of mangroves has left many remaining habitats severely damaged.

These impacts are likely to continue, and worsen, as human populations expand further into the mangals. In regions where mangrove removal has produced significant environmental problems, efforts are underway to launch mangrove agroforestry and agriculture projects. Mangrove systems require intensive care to save threatened areas. So far, conservation and management efforts lag behind the destruction; there is still much to learn about proper management and sustainable harvesting of mangrove forests.

Mangroves have enormous ecological value. They protect and stabilize coastlines, enrich coastal waters, yield commercial forest products and support coastal fisheries. Mangrove forests are among the world's most productive ecosystems, producing organic carbon well in excess of the ecosystem requirements and contributing significantly to the global carbon cycle. Extracts from mangroves and mangrove-dependent species have proven activity against human, animal and plant pathogens. Mangroves may be further developed as sources of high-value commercial products and fishery resources and as sites for a burgeoning ecotourism industry. Their unique features also make them ideal sites for experimental studies of biodiversity and ecosystem function. Where degraded areas are being revegetated, continued monitoring and thorough assessment must be done to help understand the recovery process. This knowledge will help develop strategies to promote better rehabilitation of degraded mangrove habitats the world over and ensure that these unique ecosystems survive and flourish.

Biology of mangroves and mangrove Ecosystems

Metals in the Hydrocycle.

1 Introduction.- 2 Interactions with Ligands, Particulate Matter and Organisms.- 2.1 Introduction.- 2.2 Metal Ions in Aquatic Systems.- 2.3 Speciation of Dissolved Metals.- 2.3.1 Physical Separation.- 2.3.2 ASV-Labile Species.- 2.3.3 Ion-Exchange Methods.- 2.3.4 Speciation Schemes.- 2.4 Interaction with Ligands.- 2.5 Interaction with Particulate Matter.- 2.5.1 Sorption Processes.- 2.5.2 Mechanisms.- 2.5.3 Sorption on Metal Oxides and Organic Substances.- 2.5.4 Sorption of Metal-Organic Complexes.- 2.5.5 Interactions in Natural Systems.- 2.6 Solid Speciation.- 2.7 Metal Interaction with Organisms.- 2.7.1 Metal Uptake by Organisms.- 2.7.2 Solid Speciation and Bioavailability.- 2.7.3 Transformation of Metal by Organisms.- 3 Sediments and the Transport of Metals.- 3.1 Introduction.- 3.2 Composition of Sediments.- 3.3 Transport of Sediments.- 3.4 Distribution and Deposition.- 3.5 Grain Size Effects.- 3.6 Anthropogenic Influences on Metal Concentrations in Sediments.- 3.6.1 Background Concentrations.- 3.6.2 Sediment Core Studies.- 3.6.3 Quantification of Environmental Impact.- 3.7 Early Diagenesis of Trace Metal Compounds in Sediments.- 3.7.1 Sampling of Interstitial Waters.- 3.7.2 Diagenetic Environments.- 3.7.3 Diagenetic Mobilization of Trace Metals.- 4 Metals in the Atmosphere.- 4.1 Introduction.- 4.2 Natural and Anthropogenic Emissions of Trace Metals.- 4.3 Atmospheric Particles.- 4.4 Deposition of Atmospheric Particles.- 4.5 Metal Concentrations in Urban, Rural and Remote Atmospheres.- 4.6 Environmental Impact of Airborne Trace Metals.- 4.6.1 Terrestrial Ecosystems..- 4.6.2 The Arctic and Antarctic Aerosol.- 4.6.2.1 Concentrations in Arctic and Antarctic Areas.- 4.6.2.2 Seasonal Changes.- 4.6.2.3 Origin of the Arctic Aerosol.- 4.6.3 Metals in the Oceanic Aerosol: Continental or Ocean Derived?.- 4.6.3.1 Formation of the Oceanic Aerosol.- 4.6.3.2 Sea Surface Microlayer.- 4.6.3.3 Composition of the Oceanic Aerosol.- 5 Metals in Continental Waters.- 5.1 Introduction.- 5.2 Metals in Rocks and Soils.- 5.2.1 Igneous and Metamorphic Rocks.- 5.2.2 Weathering and Element Migration.- 5.2.3 Chemistry of Sedimentary Rocks.- 5.2.4 Metals in Soils.- 5.2.4.1 Soil Constituents and Metal Binding.- 5.2.4.2 Trace Metal Concentrations in Soils.- 5.2.4.3 Metal Transfer from Soil to Plants.- 5.2.4.4 Problems with River-borne Metal Pollutants on Agricultural Soils.- 5.2.4.5 Land Disposal of Metal-Contaminated Waste Materials.- 5.3 Metals in Rivers.- 5.3.1 Trace Metals in River Water.- 5.3.2 Dissolved and Solid Transport.- 5.3.2.1 Geographical Variability.- 5.3.2.2 Seasonal Variability.- 5.3.3 Metals in River Sediment.- 5.3.3.1 Factors Affecting Compositions.- 5.3.3.2 Variability of Data.- 5.3.3.3 Influence of Grain Size.- 5.3.3.4 Metal Forms.- 5.3.4 Impact of Metals in River Systems.- 5.3.4.1 Distribution of Metal Pollutants.- 5.3.4.2 Historical Evolution.- 5.3.4.3 Metal Budgets and Local Inputs.- 5.3.5 Complexing Agents in River Systems.- 5.4 Metals in Lakes.- 5.4.1 Introduction.- 5.4.2 Accumulative Phases in Lake Sediments.- 5.4.3 Trace Metal Fluxes as Reflected in the Sediments.- 5.4.4 Metals Cycling in Lakes.- 5.4.5 Metals Cycling in Stratified Lakes.- 5.4.6 Atmospheric Inputs in Lakes.- 6 Metals in Estuaries and Coastal Environments.- 6.1 Introduction.- 6.2 Estuarine Circulation.- 6.3 Conservative and Non-Conservative Behaviour.- 6.4 Behaviour of Particulate Trace Metals During Estuarine Mixing.- 6.5 Iron and Manganese.- 6.6 Trace Metals in Estuaries: Field Investigations.- 6.7 Trace Metals in Estuaries: Laboratory Investigations and Simulations.- 6.8 Environmental Impact Studies.- 6.8.1 United States Estuaries and Coastal Areas.- 6.8.2 Mediterranean Sea.- 6.8.3 Western Europe.- 6.8.4 Environmental Impact of Metals in Biota.- 6.9 Estuaries as Sinks for Trace Metals?.- 7 Metals in the Ocean.- 7.1 Introduction.- 7.2 Vertical and Horizontal Distribution of Trace Metals..- 7.3 Particulates and Metal Behaviour.- 7.4 Composition of Oceanic Sediments.- 7.4.1 Marine Sedimentary Facies.- 7.4.2 Metal Concentrations.- 7.4.3 Metal Enrichment in Deep-Sea Sediments.- 7.4.3.1 Diagenetic Metal Enrichment-Manganese Nodules.- 7.4.3.2 Metal Enrichment from Hydrothermal Inputs.- 7.5 Cycling of Trace Metals Between Continents and Oceans.- 8 Summary and Qutlook.- References.

Metals in the hydrocycle

Fine-grained sediment is a natural and essential component of river systems and plays a major role in the hydrological, geomorphological and ecological functioning of rivers. In many areas of the world, the level of anthropogenic activity is such that fine-grained sediment fluxes have been, or are being, modified at a magnitude and rate that cause profound, and sometimes irreversible, changes in the way that river systems function. This paper examines how anthropogenic activity has caused significant changes in the quantity and quality of fine-grained sediment within river systems, using examples of: land use change in New Zealand; the effects of reservoir construction and management in different countries; the interaction between sediment dynamics and fish habitats in British Columbia, Canada; and the management of contaminated sediment in USA rivers. The paper also evaluates present programmes and initiatives for the management of fine sediment in river systems and suggests changes that are needed if management strategies are to be effective and sustainable. Copyright © 2005 John Wiley & Sons, Ltd.

Fine-grained sediment in river systems : Environmental significance and management issues

Environmental impact of metals derived from mining activities: Processes, predictions, prevention

Sediment analyses are used to pin‐point major sources of metal pollution and to estimate the toxicity potential of dredged materials on agricultural land. For source assessments (Part I of the present review) standardization is needed with respect to grain size effects, commonly achieved by analyzing the sieve fraction <63μm. Further aspects include sampling methods, evaluation of background data and extent of anthropogenic metal enrichment.

Wim Salomons

Papers

Metals in the Hydrocycle.

Metals in the hydrocycle

Fine-grained sediment in river systems : Environmental significance and management issues

Environmental impact of metals derived from mining activities: Processes, predictions, prevention

Trace metal analysis on polluted sediments