Assessment of the content,occurrence, and leachability of arsenic,lead, and thallium in wastes from coal cleaning processes

The aim of the study was to evaluate the content, occurrence, and leachability of arsenic (As), lead (Pb), and thallium (Tl) in wastes from coal cleaning processes with respect to the safe management of this waste. The study focused on wastes resulting from the wet gravitation and flotation processes employed for the purposes of coking coal cleaning in four coal mines situated in the Upper Silesian Coal Basin (Poland). The scope of the study included (i) determination of the content of these elements in the investigated wastes using atomic absorption spectrometry, (ii) evaluation of their mode of occurrence using electron microprobe analysis, and (iii) preliminary assessment of their leachability in deionized water. The content of the analyzed elements in the examined samples of coal waste was twice as high as the average content of these elements in the Earth’s crust. The contents of As and Pb, however, did not exceed their permissible contents in inert waste in accordance with Polish legal regulations based on EU directives. The limit on the content of Tl is not specified by these regulations, but its amount in the examined samples was similar to that occurring in the soils. Moreover, leaching tests have shown that these elements are hardly eluted from the analyzed material. Their content in the water leachates was generally lower than the detection limit of the analytical method, complying with the standards for good and very good water quality. Low leachability of these elements most probably results from their mode of occurrence in the investigated wastes. The chemical analysis using an electron microprobe and the analysis of the correlation between these elements, e.g., total and pyritic sulfur, have shown that Pb, As, and Tl are mainly found in sulfide minerals which are characterized by negligible solubility. In conclusion, the investigated hard coal processing waste does not constitute a threat to the environment and can be commercially used or safely neutralized, e.g., by landfilling.

     

Microbial spheres: a novel cyanobacterial–diatom symbiosis

Cyanobacteria, algae and bacteria are widespread inhabitants of North Sea microbial mats. Our studies of these populations showed uncommon modes of living and extraordinary structures, which have not been described before. The structures are spherical objects covering a community of cyanobacteria, diatoms and bacteria. The cultivation of these communities in the laboratory and intensive observations of their exceptional movement has led to some spectacular findings. The sphere formations go through different phases with variation in the dominance of different microorganisms. The role of the bacteria is the most important in the first phase, and can be increased by the addition of signal substances. Spheres surrounded by envelopes of unknown composition and permeability appear, with numerous bacteria and sporadic diatoms inside. Then the cyanobacteria penetrate the spheres and arrange themselves at the surface. The communities proliferate over some weeks and are finally released. Laboratory expositions of the microbial communities to different parameters pinpoint the limits of sphere formation. The metabolic products of the sphere communities are concentrated in the spheres and lead to a different kind of compound compared with the surrounding environment. In this way, the microbial communities strongly influence the structure of the sediments. Uncommon circular structures, which develop into spheres between 0.08 and 3 mm in size were found in subcultures of non-axenic filamentous cyanobacteria enrichments from North Sea microbial mats. These filamentous cyanobacteria (Phormidium sp.) together with associated benthic diatoms of the genus Navicula and associated heterotrophic bacteria were held as reproducible synergistic cultures. Phormidium sp. filaments tightly intertwined with each other, formed the surface of the spheres, trapping diatoms inside. The formation of "spheres" was the result of radial and synchronous movements of the cyanobacteria. In old cultures, the direction of the cyanobacterial movement has turned in the opposite direction, away from the sphere. The integrity of large "spheres" was influenced by chemotactic phenomena and maintained by some type of trichome-trichome interaction. This suggests the presence of metabolic secondary products, which attract cyanobacteria and influence their movement in a form of chemotactic response.     

Present to future sediment transport of the Brahmaputra River: reducing uncertainty in predictions and management

The Brahmaputra River in South Asia carries one of the world’s highest sediment loads, and the sediment transport dynamics strongly affect the region’s ecology and agriculture. However, present understanding of sediment conditions and dynamics is hindered by limited access to hydrological and geomorphological data, which impacts predictive models needed in management. We here synthesize reported peer-reviewed data relevant to sediment transport and perform a sensitivity analysis to identify sensitive and uncertain parameters, using the one-dimensional model HEC-RAS, considering both present and future climatic conditions. Results showed that there is considerable uncertainty in openly available estimates (260–720 Mt yr^?1) of the annual sediment load for the Brahmaputra River at its downstream Bahadurabad gauging station (Bangladesh). This may aggravate scientific impact studies of planned power plant and reservoir construction in the region, as well as more general effects of ongoing land use change and climate change. We found that data scarcity on sediment grain size distribution, water discharge, and Manning’s roughness coefficient had the strongest controls on the modelled sediment load. However, despite uncertainty in absolute loads, we showed that predicted relative changes, including a future increase in sediment load by about 40 % at Bahadurabad by 2075–2100, were consistent across multiple model simulations. Nevertheless, for the future scenarios we found that parameter uncertainty almost doubled for water discharge and river geometry, highlighting that improved information on these parameters could greatly advance the abilities to predict and manage current and future sediment dynamics in the Brahmaputra river basin.     

Natural organic matter controls metal speciation and toxicity for marine organisms: a review

Environmental Chemistry Letters - Heavy metals are occurring in the aquatic environment as the result of natural or anthropogenic inputs, and depending on concentration, availability and resilience...     

Seasonal patterns of the bacterioplankton community composition in a lake threatened by a pesticide disposal site

Background aim and scope  

The objective of the study was to determine the effects of ca. 35 years of pesticide contamination (pesticide dump—PD) of Lake Szeląg Wielki (located in the north-eastern Poland) on changes in the microbial communities of aquatic ecosystems. In the years 2008–2009, analyses were carried out for seasonal changes in the quantity and composition of bacterioplankton in the lake examined, which is of high significance to the tourism and fishing industries and is located in the vicinity of an area subjected to reclamation after a pesticide dump.     

The population dynamics of nitrifiers in ammonium-rich systems

Non-optimal pH, dissolved oxygen concentration, the presence of toxic substances, or the influence of grazers are known to cause disturbances in nitrification. Because activated sludge is a mixture of different organisms, bacteria, and higher organisms, the stability of processes such as carbon removal, nitrification, denitrification, and dephosphatation depends on a range of interactions. These interactions occur both between and within trophic levels. Understanding of the ecology of microorganisms involved in bioprocesses is essential for effective control of startup and operation of a particular process. The aim of the study was to gain further insight into the dynamics of nitrifiers in activated sludge at various sludge ages while treating higher concentrations of ammonium. The results confirmed the importance of Nitrosococcus mobilis and Nitrobacter sp. as the dominant nitrifiers responsible for nitritation and nitratation, respectively, in the presence of unlimited ammonium. The size of the dominant bacteria colony was larger compared to the other species present and reached 25 microm. Problems with nitrification occurred in all high-ammonium loaded reactors. The dynamics of nitrifier population was monitored by oxygen uptake rate (OUR) using a test enabling the OUR measurement separately for ammonium-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB). The results reveal the hypersensitivity of nitrifiers to the substrate and products of incomplete nitrification.     

Can Repeated Fertilizer Applications to Young Norway Spruce Enhance Avian Diversity in Intensively Managed Forests?

Repeated fertilization of forests to increase biomass production is an environmentally controversial proposal, the effects of which we assessed on breeding birds in stands of young Norway spruce (Picea abies), in an intensively managed forest area in southern Sweden. Our results show that fertilized stands had 38% more species and 21% more individuals than unfertilized stands. Compared with stands under traditional management, the further intensification of forestry by repeated applications of fertilizers thus seemed to enhance species richness and abundance of forest birds. We cannot conclude at this stage whether the response in the bird community was caused by changes in food resources or increased structural complexity in the forest canopy due to the skid roads used for the application of the fertilizers. Future studies should focus on structural and compositional effects of fertilization processes during the entire rotation period and at assessing its effects in a landscape context.