Background, aim and scope
Australia is the largest producer of bauxite in the world, with an annual output of approximately 62 million metric dry tons in 2007. For every tonne of alumina, about 2 tonnes of highly alkaline and highly saline bauxite-processing residue are produced. In Western Australia, Alcoa World Alumina, Australia (Alcoa) produces approximately 15 MT of residue annually from its refineries (Kwinana, Pinjarra and Wagerup). The bauxite-processing residue sand (BRS) fraction represents the primary material for rehabilitating Alcoa’s residue disposal areas (RDAs). However, the inherently hostile characteristics (high alkalinity, high salinity and poor nutrient availability) of BRS pose severe limitations for establishing sustainable plant cover systems. Alcoa currently applies 2.7 t ha−1 of di-ammonium phosphate ((NH4)2HPO4; DAP)-based fertiliser as a part of rehabilitation of the outer residue sand embankments of its RDAs. Limited information on the behaviour of the dominant components of this inorganic fertiliser in highly alkaline BRS is currently available, despite the known effects of pH on ammonium (NH4) and phosphorus (P) behaviour. The aim of this study was to quantify the effects of pH on NH3 volatilisation and residual nitrogen (N) in BRS following DAP applications. 相似文献Purpose
To examine (1) the effect of organic (poultry manure) and inorganic (residue mud and phosphogypsum) amendments on nutrient leaching losses from residue sand and (2) whether amendments improve the growth of plants in residue sand. 相似文献Background, aim and scope
Australia is the largest producer of bauxite in the world, with an annual output of approximately 62 million metric dry tons in 2007. For every tonne of alumina, about 2 tonnes of highly alkaline and highly saline bauxite-processing residue are produced. In Western Australia, Alcoa World Alumina, Australia (Alcoa) produces approximately 15 MT of residue annually from its refineries (Kwinana, Pinjarra and Wagerup). The bauxite-processing residue sand (BRS) fraction represents the primary material for rehabilitating Alcoa’s residue disposal areas (RDAs). However, the inherently hostile characteristics (high alkalinity, high salinity and poor nutrient availability) of BRS pose severe limitations for establishing sustainable plant cover systems. Alcoa currently applies 2.7 t ha?1 of di-ammonium phosphate ((NH4)2HPO4; DAP)-based fertiliser as a part of rehabilitation of the outer residue sand embankments of its RDAs. Limited information on the behaviour of the dominant components of this inorganic fertiliser in highly alkaline BRS is currently available, despite the known effects of pH on ammonium (NH4) and phosphorus (P) behaviour. The aim of this study was to quantify the effects of pH on NH3 volatilisation and residual nitrogen (N) in BRS following DAP applications.Methods
The sponge-trapping and KCl-extraction method was used for determining NH3 volatilisation from surface-applied DAP in samples of BRS collected from each of Alcoa’s three Western Australia Refineries (Kwinana, Pinjarra, Wagerup) under various pH conditions (pH 4, 7, 9 and 11). Following cessation of volatilisation, the residual N was extracted from BRS using 2 M KCl and concentrations of NH 4 + –N and NO 3 ? –N were determined by flow injection analysis.Results
The quantities of NH3 volatilised increased dramatically as the pH increased from 4 to 11. Much of the N lost as NH3 (up to 95.2%) occurred within a short period (24 h to 7 days), particularly for the pH 9 and 11 treatments. Concentrations of residual NH 4 + –N recovered in DAP-treated BRS at the end of the experiment decreased with increasing pH. This finding was consistent with increasing loss of N via volatilisation as pH increased. The concentration of NO 3 ? –N was very low due to no nitrification in BRS.Discussion
The pH was a key driver for NH3 volatilisation from DAP-treated BRS and primarily controlled N dynamics in BRS. Results indicate that NH4 not adsorbed by BRS was highly susceptible to volatilisation. The likely lack of nitrifying bacteria did not allow conversion of ammonium to nitrate, thereby further exacerbating the potential for loss via volatilisationConclusions
It was demonstrated that the pH is the key factor controlling the loss of inorganic N from BRS. Although volatilisation was considerably lower at pH 4, achieving this pH reduction in the field is not possible at present. Findings from this study highlight the need to better understand which forms of N fertiliser are most suitable for use in highly alkaline BRS.Recommendation and perspectives
Although pH reduction is the most likely means of stopping NH3 volatilisation in BRS, it is economically and operationally unfeasible to add sufficient acidity for adequately lowering pH in the BRS for revegetation. More attention on forms of fertilisers more suitable to highly alkaline, microbially inert soil conditions appears to be warranted.Introduction
A mercury (Hg) processing plant previously operating in KwaZulu-Natal Province (South Africa) discharged Hg waste into a nearby river system causing widespread contamination since the 1980s. Although the processing plant ceased operation in the 1990s, Hg contamination (due to residual Hg) remains significant. Previous studies in the area since the plant’s closure have found elevated Hg concentrations in fish, and that these concentrations were as a direct consequence of widespread contamination of the Hg processing plant operations conducted between the 1980s and 1990s. 相似文献Introduction
Understanding the sorption process in natural geomedia is necessary for effective utilization of these materials as low-cost adsorbents and consequently as controlled release hazardous elements. This research was oriented to investigate the affinity of two natural zeolite minerals towards cobalt, zinc, and nickel mixture as an important industrial and radioactive waste. 相似文献Purpose
Feral oilseed rape has become widespread in Europe on waysides and waste ground. Its potential as a source of GM impurity in oilseed rape harvests is quantified, for the first time, by a consistent analysis applied over a wide range of study areas in Europe. 相似文献Purpose
The purpose of the research is to investigate the application of bagasse fly ash, a sugar industry solid waste for the synthesis of zeolites and their behavior for the sorption of p-nitrophenol (p-NP). 相似文献Purpose
Solid waste incineration has recently attracted much attention because the combustion process involved produces highly toxic organohalogen contaminants such as dioxin-like polychlorinated biphenyls (DL-PCBs) present in fly ash. This has raised the need for simple, rapid, accurate methods for monitoring PCBs in ash samples. 相似文献This comparative field study examined the responses of bacterial community structure and diversity to the revegetation of zinc (Zn) smelting waste slag with eight plant species after 5 years. The microbial community structure of waste slag with and without vegetation was evaluated using high-throughput sequencing. The physiochemical properties of Zn smelting slag after revegetation with eight plant rhizospheres for 5 years were improved compared to those of bulk slag. Revegetation significantly increased the microbial community diversity in plant rhizospheres, and at the phylum level, Proteobacteria, Acidobacteria, and Bacteroidetes were notably more abundant in rhizosphere slags than those in bulk waste slag. Additionally, revegetation increased the relative abundance of plant growth-promoting rhizobacteria such as Flavobacterium, Streptomyces, and Arthrobacter as well as symbiotic N2 fixers such as Bradyrhizobium. Three dominant native plant species (Arundo donax, Broussonetia papyrifera, and Robinia pseudoacacia) greatly increased the quality of the rhizosphere slags. Canonical correspondence analysis showed that the differences in bacterial community structure between the bulk and rhizosphere slags were explained by slag properties, i.e., pH, available copper (Cu) and lead (Pb), moisture, available nitrogen (N), phosphorus (P), and potassium (K), and organic matter (OM); however, available Zn and cadmium (Cd) contents were the slag parameters that best explained the differences between the rhizosphere communities of the eight plant species. The results suggested that revegetation plays an important role in enhancing bacterial community abundance and diversity in rhizosphere slags and that revegetation may also regulate microbiological properties and diversity mainly through changes in heavy metal bioavailability and physiochemical slag characteristics.
相似文献Background, aim, and scope
The aim of this work was to determine phytotoxicity of washing waste-waters from a cutlery production line with high content of Cr and Ni. These waters were previously classified, without verification, as dangerous and it is now necessary to question the justice of the present classification under the new legislation for waste management (Waste Law No. 223/2001) in the Slovak Republic. 相似文献Background, aim, and scope
The purpose of this study was to compare the suitability of different phytotoxicity testing procedures for the evaluation of toxicity associated with both soil contamination and solid wastes, both of which can be of environmental risk to plants. Ten different representative types of contaminated soils and solid waste samples were chosen from the Czech Republic. 相似文献Introduction
Several hot spots of severe freshwater pollution and sediment contamination (mostly heavy metals, polyaromatic hydrocarbons and polychlorinated biphenyls) have been identified in Serbia as the consequence of outdated environmental legislation, negligible amounts of properly treated waste waters and accidental spills. 相似文献Purpose
The aim of this study was to analyze air concentrations of chemical and microbiological pollutants in the vicinity of an organic waste treatment plant, Ecoparc-2, located in Montcada i Reixac (Catalonia, Spain), as well as to determine the seasonal trends. The human health risks due to the presence of those agents were also assessed. 相似文献Residue field trials in cucumber were conducted for the safe use of a commercial formulation of cyproconazole·azoxystrobin 28% suspension concentrate (SC 294 g a.i. ha?1, three applications at a 7-day interval) in the year 2018, in China. To determine the residues of cyproconazole and azoxystrobin in cucumber, a quick, easy, cheap, effective, rugged, and safe (QuEChERS) method was developed using high-performance liquid chromatography coupled with tandem mass spectrometry. This validated method was applied to analyze cucumber samples collected from 12 specified regions. At the 3-day interval to harvest, the highest residue (HR) of azoxystrobin was 0.150 mg kg?1, which was lower than the maximum residue limit (MRL; 0.5 mg kg?1) permitted in China, and the HR of cyproconazole was 0.084 mg kg?1, for which no MRL value has been set in China. The chronic risk quotient values of cyproconazole and azoxystrobin for Chinese adults at a 3-day interval to harvest were 2.56% and 13.72%, respectively. The acute risk quotient values of cyproconazole in cucumber were specified as 5.52% for children (1–6 years old) and 2.83% for the adults (>?18 years old) in China. These results indicate that cyproconazole·azoxystrobin 28% SC sprayed on cucumber at the pre-harvest interval of 3 days has no significant potential risk for Chinese consumers.
相似文献