Arsenic mobilization from iron oxyhydroxides is regulated by organic matter carbon to nitrogen (C:N) ratio

Arsenic (As) is mobilized from delta and floodplain aquifer sediments throughout S.E. Asia via reductive dissolution of As bound to iron (Fe) oxyhydroxides. The reductive driving force is organic carbon, but its source and constitution is uncertain. Here batch incubation experiments were conducted to investigate the role of organic matter (OM) carbon:nitrogen (C:N) ratio on the mobilization of arsenic, Fe and N from As dosed, Fe oxyhydroxide coated sands. As mobilization into pore waters from the sand was strongly regulated by the C:N ratio of the OM, and also the concentration of OM present. The lower the C:N, the more As released. Fe and ammonium release were similarly dependent on the quality and quantity of OM, but Fe mobilization was more rapid and ammonium release slower than As suggesting that the mobilization of these 3 moieties although interdependent, were not directly linked. It was concluded that low C:N ratios for OM responsible for reducing aquifers were As in groundwater is observed were likely.

Direct evidence showing the effect of root surface iron plaque on arsenite and arsenate uptake into rice (Oryza sativa) roots

The present study aimed to investigate the effects of root surface iron plaque on the uptake kinetics of arsenite and arsenate by excised roots of rice (Oryza sativa) seedlings. The results demonstrated that the presence of iron plaque enhanced arsenite and decreased arsenate uptake. Arsenite and arsenate uptake kinetics were adequately fitted by the Michaelis-Menten function in the absence of plaque, but produced poor fits to this function in the presence of plaque. Phosphate in the uptake solution did not have a significant effect on arsenite uptake irrespective of the presence of iron plaque; however phosphate had a significant effect on arsenate uptake. Without iron plaque, phosphate inhibited arsenate uptake. The presence of iron plaque diminished the effect of phosphate on arsenate uptake, possibly through a combined effect of arsenate desorption from iron plaque.

The Doñana ecological disaster:contamination of a world heritage estuarine marsh ecosystem with acidified pyrite mine waste

One of the most important bird breeding and over wintering sites in the west of Europe, the Coto Doñana, was severely impacted by the release of 5 million cubic meters of acid waste from the processing of pyrite ore. The waste entered ecologically sensitive areas of the park (including breeding areas for internationally endangered bird species) causing sustained pH decreases from pH 8.5 to 4.5 and resulting in massive metal contamination of the impacted ecosystem. The contaminating sludge waste contained arsenic at 0.6%, lead at 1.2% and zinc at 0.8% on a dry weight basis. The acid conditions facilitated the solubilization of these metals, leading to water concentrations lethal for aquatic wildlife. The accident caused considerable fish and invertebrate kills and has severe consequences for the protected bird species dependent on the impacted habitats and adjacent areas.

Arsenic, cadmium, and lead pollution and uptake by rice (Oryza sativa L.) grown in greenhouse

Purpose: Hunan province is well-known for its extensive base-metal extraction and smelting industries. However, the legacies of excavation operations, transportation, and selective smelting activities within Hunan have resulted in the generation of large quantities of mine wastes, which will become the sources of metal contamination in the environment. Thus, there is an increasingly important health issue underlying the study of arable land pollution and transfer of As, Cd, and Pb in the paddy soil–rice system.
Materials and methods: Paddy soils collected from mining- and smelting-impacted areas in Hunan province and rice seed (Oryza sativa L. cv Jia Hua-1) were used for pot experiments under greenhouse conditions. One 30-day-old seedling was transplanted into one pot containing 5.0 kg pretreated soil. At harvest, rice grains and shoots were washed with distilled water to remove surface soil, and oven-dried at 65°C for 96 h until a constant weight was reached. Roots were washed carefully with distilled water for the next process of extracting iron plaque using dithionite–citrate–bicarbonate solution. Total concentrations of As, Cd, and Pb in soil and rice plant tissues were measured by inductively coupled plasma mass spectrometer.
Results and discussion: Total concentrations of As, Cd, and Pb in the soils collected from 12 mining- and smelting-impacted areas in Hunan province were much higher than Hunan background values and exceeded the maximum concentration limit for soils set by the Ministry of Environmental Protection. The yields of rice grain from Pb/Zn mining and smelting sites were negatively correlated to overall pollution scores. Distributions of As, Cd, and Pb in rice plant followed: root >> shoot > husk > whole grain. About 30.1–88.1% of As, 11.2–43.5% of Cd, and 14.0–33.9% of Pb were accumulated in iron plaque on root surfaces.
Conclusions: High concentrations of As, Cd, and Pb are observed in paddy soils from mining- and smelting-impacted areas in Hunan province, indicating those paddy soils suffer serious combined heavy metal contamination. In particular, Cd is the dominant contaminant followed by As and Pb in paddy soils from most locations. The distributions of As, Cd, and Pb in rice tissue were: root >> shoot > husk > whole grain. Concentrations of Pb in all whole grain and of As and Cd in 50% of whole grain samples exceeded Chinese Hygienic Standard values for food.

A comparison of biodegradable municipal waste (BMW) management strategies in Ireland and the Czech Republic and the lessons learned

In order to meet the recycling and recovery targets set forth by the European Union's (EU) Waste and Landfill Directives, both the Irish and Czech governments’ policy on waste management is changing to meet these pressures, with major emphasis being placed upon the management of biodegradable municipal waste (BMW). In particular, the EU Landfill Directive requires reductions in the rate of BMW going to landfill to 35% of 1995 values by 2016 and 2020 for Ireland and the Czech Republic, respectively. In this paper, the strategies of how Ireland and the Czech Republic plan to meet this challenge are compared. Ireland either landfills or exports its waste for recovery, while the Czech Republic has a relatively new waste management infrastructure. While Ireland met the first target of 75% diversion of BMW from landfill by 2010 and preliminary 2012 data indicate that Ireland is on track to meet the 2013 target, the achievement of the 2016 target remains at risk. Indicators that were developed to monitor the Czech Republic's path to meeting the targets demonstrate that it did not meet the first target that was set for 2010 and will probably not meet its 2013 target either. The evaluation reports on the implementation of Waste Management Plan of Czech Republic suggest that the currently applied strategy to divert biodegradable waste from landfill is not effective enough. For both countries, the EU Waste Framework and Landfill Directives will be a significant influence and driver of change in waste management practices and governance over the coming decade. This means that both countries will not only have to invest in infrastructure to achieve the targets, but will also have to increase awareness among the public in diverting this waste at the household level. Improving environmental education is part of increased awareness as it is imperative for citizens to understand the consequences of their actions as affluence continues to grow producing increased levels of waste.

Graphical abstract
Despite the differences in the levels of waste generation in both the Czech Republic and Ireland, each country can learn from each other in order to meet the recycling and recovery targets set by the European Union's (EU) Waste and Landfill Directives. Both countries will not only have to invest in infrastructure to achieve the targets, but will also have to increase awareness among the public in diverting this waste at the household level. In addition, there needs to be minimum safe standards when land-spreading organic agricultural and organic municipal and industrial materials on agricultural land used for food production, as well as incentives to increase BMW diversion from landfill such as the increased landfill levy implemented in Ireland and the acceptance of MBT and/or incineration as a means of treating residual waste.

Silicon, the silver bullet for mitigating biotic and abiotic stress, and improving grain quality, in rice?

Adequate silicon fertilization greatly boosts rice yield and mitigates biotic and abiotic stress, and improves grain quality through lowering the content of cadmium and inorganic arsenic. This review on silicon dynamics in rice considers recent advances in our understanding of the role of silicon in rice, and the challenges of maintaining adequate silicon fertility within rice paddy systems. Silicon is increasingly considered as an element required for optimal plant performance, particularly in rice. Plants can survive with very low silicon under laboratory/glasshouse conditions, but this is highly artificial and, thus, silicon can be considered as essential for proper plant function in its environment. Silicon is incorporated into structural components of rice cell walls were it increases cell and tissue rigidity in the plant. Structural silicon provides physical protection to plants against microbial infection and insect attack as well as reducing the quality of the tissue to the predating organisms. The abiotic benefits are due to silicon's effect on overall organ strength. This helps protect against lodging, drought stress, high temperature (through efficient maintenance of transpiration), and photosynthesis by protecting against high UV. Furthermore, silicon also protects the plant from saline stress and against a range of toxic metal stresses (arsenic, cadmium, chromium, copper, nickel and zinc). Added to this, silicon application decreases grain concentrations of various human carcinogens, in particular arsenic, antimony and cadmium. As rice is efficient at stripping bioavailable silicon from the soil, recycling of silicon rich rice straw biomass or addition of inorganic silicon fertilizer, primarily obtained from iron and steel slag, needs careful management. Silicon in the soil may be lost if the silicon-cycle, traditionally achieved via composting of rice straw and returning it to the land, is being broken. As composting of rice straw and incorporation of composted or non-composted straw back to land are resource intensive activities, these activities are declining due to population shifts from the countryside to cities. Processes that accelerate rice straw composting, therefore, need to be identified to aid more efficient use of this resource. In addition, rice genetics may help address declining available silicon in paddy soils: for example by selecting for characteristics during breeding that lead to an increased ability of roots to access recalcitrant silicon sources from soil and/or via selection for traits that aid the maintenance of a high silicon status in shoots. Recent advances in understanding the genetic regulation of silicon uptake and transport by rice plants will aid these goals.

Knowledge Management Techniques to Augment Textual CBR (PhD Thesis)

The past decade had witnessed an unprecedented growth in the amount of available digital content, and its volume is expected to continue to grow the next few years. Unstructured text data generated from web and enterprise sources form a large fraction of such content. Many of these contain large volumes of reusable data such as solutions to frequently occurring problems, and general know-how that may be reused in appropriate contexts. In this work, we address issues around leveraging unstructured text data from sources as diverse as the web and the enterprise within the Case-based Reasoning framework. Case-based Reasoning (CBR) provides a framework and methodology for systematic reuse of historical knowledge that is available in the form of problemsolution
pairs, in solving new problems. Here, we consider possibilities of enhancing Textual CBR systems under three main themes: procurement, maintenance and retrieval. We adapt and build upon the stateof-the-art techniques from data mining and natural language processing in addressing various challenges therein. Under procurement, we investigate the problem of extracting cases (i.e., problem-solution pairs) from data sources such as incident/experience
reports. We develop case-base maintenance methods specifically tuned to text targeted towards retaining solutions such that the utility of the filtered case base in solving new problems is maximized. Further, we address the problem of query suggestions for textual case-bases and show that exploiting the problem-solution partition can enhance retrieval effectiveness by prioritizing more useful query suggestions. Additionally, we illustrate interpretable clustering as a tool to drill-down to domain specific text collections (since CBR systems are usually very domain specific) and develop techniques for improved similarity assessment in social media sources such as microblogs. Through extensive empirical evaluations, we illustrate the improvements that we are able to
achieve over the state-of-the-art methods for the respective tasks.

A Microscopic Study of Iron and Manganese Oxide Distribution in Soils from East Tennessee (U.S.A.)

Soils and saprolites developed from interbedded shales and limestones of the Conasauga Group are widespread in the Valley and Ridge Province of East Tennessee. Thin sections from four soil profiles were examined by petrographic and scanning electron microscopy including backscatter electron and energy-dispersive X-ray analyses. Iron and manganese released by weathering had migrated differentially downward and precipitated as crystalline and noncrystalline oxides. Oxides were observed as nodules, granular particulates, pore fillings, and coatings on other minerals, packing voids, vesicles, channels, and chambers. Iron oxides formed predominantly as coatings on packing-void walls and on laminated clays in vesicles and channels. Manganese oxides occurred as an early replacement phase of packing voids and of fracture-filling carbonate minerals. Iron oxides were dominant in moderately well-drained and oxidized horizons of the soil solum, whereas manganese oxides were abundant in the oxidized and moderately leached saprolite zone where the water table fluctuates seasonally. Therefore, a manganese enrichment zone, on a bulk soil basis, occurred generally below the iron oxide zone in the soil profile. Such differential migration and accumulation of iron and manganese have been controlled by localized soil microenvironments. Micromorphologic features observed in this study are important in land-use evaluation for hazardous waste disposal. © 1990.

Preparation and evaluation of Fuller's Earth Beads for removal of Cesium from waste streams

This work deals with removal of Cesium (radioactive waste) in dilute aqueous phase by adsorption. Fullers earth was used as an adsorbent. The adsorption capacity of Fullers earth with respect to Cesium was found to be high, 26.3 mg / g of adsorbent.