Recycling of biogenic hydroxyapatite (HAP) for cleaning of lead from wastewater: performance and mechanism

Environmental Science and Pollution Research - In China, the utilization and recycling of chicken waste have become a significant environmental issue. In this study, we investigate the efficacy of...     

Diatomic remains in sediments of Le An River flowing into Po Yang Lake

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Intercomparison of Satellite Remote Sensing‐Based Flood Inundation Mapping Techniques

The objective of this study was to determine the accuracy of five different digital image processing techniques to map flood inundation extent with Landsat 8–Operational Land Imager satellite imagery. The May 2016 flooding event in the Hempstead region of the Brazos River, Texas is used as a case study for this first comprehensive comparison of classification techniques of its kind. Five flood water classification techniques (i.e., supervised classification, unsupervised classification, delta‐cue change detection, Normalized Difference Water Index [NDWI], modified NDWI [MNDWI]) were implemented to characterize flooded regions. To identify flood water obscured by cloud cover, a digital elevation model (DEM)–based approach was employed. Classified floods were compared using an Advanced Fitness Index to a “reference flood map” created based on manual digitization, as well as other data sources, using the same satellite image. Supervised classification yielded the highest accuracy of 86.4%, while unsupervised, MNDWI, and NDWI closely followed at 79.6%, 77.3%, and 77.1%, respectively. Delta‐cue change detection yielded the lowest accuracy with 70.1%. Thus, supervised classification is recommended for flood water classification and inundation map generation under these settings. The DEM‐based approach used to identify cloud‐obscured flood water pixels was found reliable and easy to apply. It is therefore recommended for regions with relatively flat topography.     

Bioremediation of petroleum‐impacted soils from investigation‐derived wastes

Optimal conditions for bioremediation of investigation‐derived wastes from petroleum‐impacted soils (PIS) were determined through biotreatability experiments. The PIS was collected as extruded cores obtained during sample drilling. These samples were processed into workable media prior to treatment in bioreactors. Soil moisture content in the bioreactors was adjusted to 30 percent, 40 percent, 50 percent (control), and 60 percent, dry‐weight basis, and nutrient levels were adjusted by applying fertilizer, yielding carbon (C) to nitrogen (N) ratios of 20:1, 10:1, and 5:1, versus a control C:N ratio of 140:1. Temperature, pH, viable bacterial plate counts, contaminant degradation rate, and microbial respiration were monitored. Concentrations of three selected branched alkanes in the aviation fuel contaminant, measured by gas chromatography, decreased for most treatments. The greatest degradation occurred with a moisture content of 40 percent and C:N ratio of 5:1. Increased contaminant degradation was consistent with increased microbial activity measured by respiration. There was poorer correlation between contaminant degradation and viable plate counts, which suggests that respirometry is a better measure of activity of the microbial population responsible for contaminant degradation. General plate counts, which enumerate only a fraction of the total population, may not be a reliable quantitative indicator of the actual microorganism population that is responsible for degradation. © 2003 Wiley Periodicals, Inc.     

Enhancement of phenanthrene adsorption on a clayey soil and clay minerals by coexisting lead or cadmium

Phenanthrene is commonly present together with heavy metals at many contaminated sites. This study investigated the influence of coexisting lead (Pb²⁺) or cadmium (Cd²⁺) on phenanthrene adsorption on soils. Batch experiments were conducted under different geochemical conditions including pH, mineral structure, organic matter content, and varying amounts of heavy metals. The results showed that the presence of heavy metals in solution at a fixed pH of 5.8 ± 0.1 enhanced phenanthrene adsorption, the extent of which was closely related to the concentrations and the electro-negativity of the metals. The enhancement on phenanthrene adsorption was positively correlated to the amount of adsorbed metals. Although Cd²⁺ is a softer Lewis acid, Pb²⁺ displayed a more significant effect as it was adsorbed to a greater extent on the soil surfaces. Thus, density of cation accumulation appears to be more influential than metal softness in enhancing phenanthrene adsorption. Moreover, with a portion of organic matter removed by heating at 550 °C, there was a stronger enhancement of phenanthrene adsorption by coexisting Pb²⁺, indicating an increasingly dominant mechanisms associated with Pb²⁺ at a lower organic matter content. Similar enhancement phenomenon was observed on bentonite and kaolinite, probably resulting from the cation-π bonding between the adsorbed soft metal cations and the aromatic ring of phenanthrene in solution. The desorption experiments further suggested that the bonding of phenanthrene adsorption was strengthened in the presence of Pb²⁺ and that a larger proportion of adsorbed phenanthrene remained on the soils (residual fraction) even after sequential methanol extractions. Further spectroscopic analyses and surface characterization are required to provide direct evidence of the formation and relative significance of cation-π bond for phenanthrene adsorption.     

SMEs and voluntary environmental initiatives: a study of stakeholders' perspectives in Hong Kong

The environmental performance of Hong Kong's businesses is currently perceived as rather poor. Small and medium-sized enterprises (SMEs) in particular are mostly unaware of the environmental impact of their business. Government and professional bodies have recently started to develop various initiatives to improve the SME sector's awareness of environmental and social issues, and external factors such as supply chain requirements, consumer preferences and energy prices are also exerting a growing influence. Based on extensive interviews with representatives of seven key stakeholder groups, this paper explores the effectiveness of such drivers to engage SMEs with environmental change and corporate social responsibility (CSR). It finds that most existing efforts, such as environmental support programmes and award schemes, do not have a great impact on the environmental and social performance of Hong Kong's SMEs.     

Enhanced irreversible fixation of cesium by wetting and drying cycles in soil

Environmental Geochemistry and Health - The retention of radioactive cesium (Cs) in soil is significantly related to the types of clay minerals, while the weathering process affects the...     

Gas-phase mechanism for dioxin formation

We consider the formation of dioxin in the gas phase through the combination of phenoxy radicals in the context of a recently published scenario regarding the possibility of forming highly chlorinated benzenes in poorly mixed systems. It is demonstrated that the production of free chlorine in fuel lean combustion systems and subsequent mixing and quenching with fuel rich mixtures leads to chlorine atoms as the main reactive radicals. Under such conditions high concentrations of chlorinated phenoxy radicals can be formed. This leads to the formation of concentrations of dioxins that are consistent with recent measurements of Sidhu et al. [Combust. Flame 100 (1995) 11]. It suggests that there may be a gas-phase channel for the dioxin formation in addition to the usually assumed surface catalyzed process.     

Pharmaceuticals and personal care products’ (PPCPs) impact on enriched nitrifying cultures

Environmental Science and Pollution Research - The impact of pharmaceutical and personal care products (PPCPs) on the performance of biological wastewater treatment plants (WWTPs) has been widely...