Effects of an iron-silicon material,a synthetic zeolite and an alkaline clay on vegetable uptake of As and Cd from a polluted agricultural soil and proposed remediation mechanisms

Economic and highly effective methods of in situ remediation of Cd and As polluted farmland in mining areas are urgently needed. Pot experiments with Brassica chinensis L. were carried out to determine the effects of three soil amendments [a novel iron-silicon material (ISM), a synthetic zeolite (SZ) and an alkaline clay (AC)] on vegetable uptake of As and Cd. SEM–EDS and XRD analyses were used to investigate the remediation mechanisms involved. Amendment with ISM significantly reduced the concentrations of As and Cd in edible parts of B. chinensis (by 84–94 % and 38–87 %, respectively), to levels that met food safety regulations and was much lower than those achieved by SZ and AC. ISM also significantly increased fresh biomass by 169–1412 % and 436–731 % in two consecutive growing seasons, while SZ and AC did not significantly affect vegetable growth. Correlation analysis suggested that it was the mitigating effects of ISM on soil acidity and on As and Cd toxicity, rather than nutrient amelioration, that contributed to the improvement in plant growth. SEM–EDS analysis showed that ISM contained far more Ca, Fe and Mn than did SZ or AC, and XRD analysis showed that in the ISM these elements were primarily in the form of silicates, oxides and phosphates that had high capacities for chemisorption of metal(loid)s. After incubation with solutions containing 800 mg L^?1 AsO₄ ^2? or Cd²⁺, ISM bound distinctly higher levels of As (6.18 % in relative mass percent by EDS analysis) and Cd (7.21 % in relative mass percent by EDS analysis) compared to SZ and AC. XRD analysis also showed that ISM facilitated the precipitation of Cd²⁺ as silicates, phosphates and hydroxides, and that arsenate combined with Fe, Al, Ca and Mg to form insoluble arsenate compounds. These precipitation mechanisms were much more active in ISM than in SZ or AC. Due to the greater pH elevation caused by the abundant calcium silicate, chemisorption and precipitation mechanisms in ISM treatments could be further enhanced. That heavy metal(loid)s fixation mechanisms of ISM ensure the remediation more irreversible and more resilient to environmental changes. With appropriate application rate and proper nutrients supplement, the readily available and economic ISM is a very promising amendment for safe crop production on multi-metal(loids) polluted soils.     

Arsenic occurrence in Brazil and human exposure

Environmental exposure to arsenic (As) in terms of public health is receiving increasing attention worldwide following cases of mass contamination in different parts of the world. However, there is a scarcity of data available on As geochemistry in Brazilian territory, despite the known occurrence of As in some of the more severely polluted areas of Brazil. The purpose of this paper is to discuss existing data on As distribution in Brazil based on recent investigations in three contaminated areas as well as results from the literature. To date, integrated studies on environmental and anthropogenic sources of As contamination have been carried out only in three areas in Brazil: (1) the Southeastern region, known as the Iron Quadrangle, where As was released into the drainage systems, soils and atmosphere as a result of gold mining; (2) the Ribeira Valley, where As occurs in Pb-Zn mine wastes and naturally in As-rich rocks and soils; (3) the Amazon region, including the Santana area, where As is associated with manganese ores mined over the last 50 years. Toxicological studies revealed that the populations were not exposed to elevated levels of As, with the As concentrations in surface water in these areas rarely exceeding 10 microg/L. Deep weathering of bedrocks along with formation of Fe/Al-enriched soils and sediments function as a chemical barrier that prevents the release of As into the water. In addition, the tropical climate results in high rates of precipitation in the northern and southeastern regions and, hence, the As contents of drinking water is diluted. Severe cases of human As exposure related to non-point pollution sources have not been reported in Brazil. However, increasing awareness of the adverse health effects of As will eventually lead to a more complete picture of the distribution of As in Brazil.     

Energy,food, and land — The ecological traps of humankind

Humans’ superiority over all other organisms on earth rests on five main foundations: command of fire requiring fuel; controlled production of food and other biotic substances; utilization of metals and other non-living materials for construction and appliances; technically determined, urban-oriented living standard; economically and culturally regulated societal organization. The young discipline of ecology has revealed that the progress of civilization and technology attained, and being further pursued by humankind, and generally taken for granted and permanent, is leading into ecological traps. This metaphor circumscribes ecological situations where finite resources are being exhausted or rendered non-utilizable without a realistic prospect of restitution. Energy, food and land are the principal, closely interrelated traps; but the absolutely decisive resource in question is land whose increasing scarcity is totally underrated. Land is needed for fulfilling growing food demands, for producing renewable energy in the post-fossil and post-nuclear era, for maintaining other ecosystem services, for urban-industrial uses, transport, material extraction, refuse deposition, but also for leisure, recreation, and nature conservation. All these needs compete for land, food and non-food biomass production moreover for good soils that are scarcer than ever. We are preoccupied with fighting climate change and loss of biodiversity; but these are minor problems we could adapt to, albeit painfully, and their solution will fail if we are caught in the interrelated traps of energy, food, and land scarcity. Land and soils, finite and irreproducible resources, are the key issues we have to devote our work to, based on careful ecological information, planning and design for proper uses and purposes. The article concludes with a short reflection on economy and competition as general driving forces, and on the role and reputation of today’s ecology. Updated version of the keynote lecture presented at the EcoSummit 2007 in Beijing, China, May 24. The article is gratefully dedicated to the memory of my late colleague and friend Frank B. Golley.     

Process,Characterization and Biodegradability of Aliphatic Aromatic Polyester/Sisal Fiber Composites

The biodegradability, morphology, and mechanical properties of composite materials made of Poly(butylene adipate-co-terephthalate) (PBAT) and sisal fiber (SF) were evaluated. Composites containing acrylic acid-grafted PBAT (PBAT-g-AA/SF) exhibited noticeably superior mechanical properties due to greater compatibility between the two components. The dispersion of SF in the PBAT-g-AA matrix was highly homogeneous as a result of ester formation between the carboxyl groups of PBAT-g-AA and hydroxyl groups in SF and the consequent creation of branched and cross-linked macromolecules. Each composite was subjected to biodegradation tests in Rhizopus oryzae compost. Morphological observations indicated severe disruption of film structure after 60 days of incubation, and both the PBAT and the PBAT-g-AA/SF composite films were eventually completely degraded. Water resistance of PBAT-g-AA/SF was higher than that of PBAT/SF, although weight loss of composites buried in Rhizopus oryzae compost indicated that both were biodegradable, even at high levels of SF substitution. The PBAT-g-AA/SF films were more biodegradable than those made of PBAT, implying a strong connection between these characteristics and biodegradability.     

Effects of Alkali Treatment on the Properties of Short Flax Fiber–Poly(Lactic Acid) Eco-Composites

In this study, the influence of alkali (NaOH) treatment on the mechanical, thermal and morphological properties of eco-composites of short flax fiber/poly(lactic acid) (PLA) was investigated. SEM analysis conducted on alkali treated flax fibers showed that the packed structure of the fibrils was deformed by the removal non-cellulosic materials. The fibrils were separated from each other and the surface roughness of the alkali treated flax fibers was improved. The mechanical tests indicated that the modulus of the untreated fiber/PLA composites was higher than that of PLA; on the other hand the modulus of alkali treated flax fiber/PLA was lower than PLA. Thermal properties of the PLA in the treated flax fiber composites were also affected. T_g values of treated flax fiber composites were lowered by nearly 10 °C for 10% NaOH treatment and 15 °C for 30% NaOH treatment. A bimodal melting behavior was observed for treated fiber composites different than both of neat PLA and untreated fiber composites. Furthermore, wide angle X-ray diffraction analysis showed that the crystalline structure of cellulose of flax fibers changed from cellulose-I structure to cellulose-II.     

Achieving uniform regulation of environmental lead exposure and poisoning in wildlife and humans

Lead from spent ammunition causes preventable lead exposure in wildlife and humans that may ingest it. Nontoxic substitutes for lead ammunition exist but are not adopted widely because of hunter opposition. Other forms of lead exposure in the human environment have been heavily regulated because there is no safe level of exposure. The use of lead ammunition should be regulated similarly to protect wildlife from this common disease.     

Efficacy of vermicomposting for recycling organic portion of hospital wastes using <Emphasis Type="Italic">Eisenia fetida</Emphasis>: standardization of cow manure proportion to increase enzymatic activities and fungal biomass

Hospital wastes are infectious wastes generated in hospitals and need to be disposed in such a way that they do not spread disease. In this experiment, 5, 10, 15 and 20% cow manure (CM) were mixed with hospital wastes (HW), and mixed wastes were subjected to vermicomposting. In control treatment, only HW was used for vermicomposting. Results suggested that significantly (P ≤ 0.05) higher total nitrogen content was recorded in vermicomposts when 10% or more CM was added to HW. Higher mineralization rate (decrease in C/N ratio) and cellulase activity is probably responsible for rapid organic matter decomposition (loss of total organic carbon). Ergosterol content i.e., total fungal biomass and cellulolytic fungal population were almost constant initially, but increased in the latter stage of vermicomposting. All the vermicompost samples, prepared in this experiment, showed the absence of coliform bacteria. Therefore, it could be concluded that 10% CM addition with HW was the most economical to obtain best quality vermicompost in terms of nutrient content and microbial status.