The effect of Mg<Superscript>2+</Superscript> on digestion performance and microbial community structures in sludge digestion systems

The important criteria in anaerobic digestion is the rate-limiting step which decides the fate of value-added products especially from waste-activated sludge (WAS). Hence, the present study investigated the effect of magnesium (Mg²⁺) addition on anaerobic digestion of WAS. The lab-scale experiments were conducted at 25 °C with Mg²⁺ doses ranging from 0.01 to 0.2 mol/L. Maximum total volatile fatty acids (VFAs) production (372.78 mg COD/L) occurred at a Mg²⁺ dose of 0.2 mol/L, which was about eight times higher than the control tests. Further, Mg²⁺ addition facilitated sludge dewaterability and phosphorus removal. The mechanism of improved VFAs generation was analyzed from the view of both chemical and biological effects. Chemical effect significantly enhanced the release of calcium and iron in WAS, resulting in the disintegration of WAS, which benefited hydrolysis and acidification processes. Illumina MiSeq sequencing analysis revealed that enrichment of functional bacteria and the increase of bacterial diversity were obtained in the 0.2 mol Mg²⁺/L experiment, while the influence was negative on the reactor with 0.025 mol/L Mg²⁺. Meanwhile, methanogens were accordantly inhibited in the experiments with Mg²⁺ addition.     

Metal-based optical chemosensors for CN<Superscript>−</Superscript> detection

This critical review focuses on recent advances (2010–2015) in the detection of cyanide anion via metal-based optical chemosensors in which a change in colour and/or fluorescence intensity (or emission wavelength) of a molecular metal complex is determined by the direct interaction of the metal centre with this anion.     

Kinetics of <Superscript>210</Superscript>Po accumulation in moss body profiles

Radionuclide concentration analysis of total moss bodies often gave relatively different results than a separate analysis of each different morphological part of the same sample. The dynamics of the transfer of metals by dust uplifted from the soil and another approach, based on the diffusion of the two radionuclides to the moss, have been analyzed. In the proposed model, short- and long-term approaches have been applied. Each part of a moss’s profile can show different radionuclides accumulation ability, including both ²¹⁰Pb and ²¹⁰Po isotopes. A first-order kinetic model has been used for ²¹⁰Po and ²¹⁰Pb transport between three body components of mosses. This mathematical approach has been applied for ²¹⁰Po activity concentration in the air estimation. For relatively clean deep forest region, calculated concentrations were from 17.2 to 43.8 μBqm^?3, while for urban air concentrations were higher from 49.1 to 104.9 μBqm^?3.     

Effect of alginate on the aggregation kinetics of copper oxide nanoparticles (CuO NPs): bridging interaction and hetero-aggregation induced by Ca<Superscript>2+</Superscript>

The stability of CuO nanoparticles (NPs) is expected to play a key role in the environmental risk assessment of nanotoxicity in aquatic systems. In this study, the effect of alginate (model polysaccharides) on the stability of CuO NPs in various environmentally relevant ionic strength conditions was investigated by using time-resolved dynamic light scattering. Significant aggregation of CuO NPs was observed in the presence of both monovalent and divalent cations. The critical coagulation concentrations (CCC) were 54.5 and 2.9 mM for NaNO₃ and Ca(NO₃)₂, respectively. The presence of alginate slowed nano-CuO aggregation rates over the entire NaNO₃ concentration range due to the combined electrostatic and steric effect. High concentrations of Ca²⁺ (>6 mM) resulted in stronger adsorption of alginate onto CuO NPs; however, enhanced aggregation of CuO NPs occurred simultaneously under the same conditions. Spectroscopic analysis revealed that the bridging interaction of alginate with Ca²⁺ might be an important mechanism for the enhanced aggregation. Furthermore, significant coagulation of the alginate molecules was observed in solutions of high Ca²⁺ concentrations, indicating a hetero-aggregation mechanism between the alginate-covered CuO NPs and the unabsorbed alginate. These results suggested a different aggregation mechanism of NPs might co-exist in aqueous systems enriched with natural organic matter, which should be taken into consideration in future studies.

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Graphical abstract Hetero-aggregation mechanism of CuO nanoparticles and alginate under high concentration of Ca²⁺

     

Fe<Superscript>0</Superscript>-based system as innovative technology for degrading trichloromethane: Redox removal characteristics

BACKGROUND: The spent waste of aliphatic chlorinated solvents has caused severe deterioration of groundwater quality. Trichloromethane (TCM), which shows health and toxicological effects on human beings, was selected as a model compound to be dechlorinated through a redox system. METHODS: The Fe0-based system including Fe0/H2O, Fe0/UV, Fe0/H2O2, and Fe0/UV/H2O2 was explored to evaluate its performance in dechlorinating TCM. H2O2 was dosed at later reaction time points to initiate Fenton or photo-Fenton reactions. The first two systems demonstrate the reductive dechlorination of TCM by Fe0-released electrons, while the latter two show dechlorination of TCM by both electron reduction and hydroxyl radical oxidation. The system parameters of TCM remaining, Cl- buildup, Fe2+ accumulation, H2O2 residue, and ORP were measured to describe different redox characteristics of TCM dechlorination. The Cl- buildup was used as a way to describe the degree of TCM dechlorination in an open reaction system. RESULTS: Reductive dechlorination efficiencies of TCM were 5% and 6% for the systems of Fe0/H2O and Fe0/UV, respectively. In contrast, the Fe/H2O2 and Fe0/UV/H2O2 systems were capable of dechlorinating TCM reductively and oxidatively by 14% and 15%, respectively. The presence of UV light was found to retard the dissolution of Fe2+, but it enhanced the rate of chloride buildup, based on the comparison of Fe0/H2O and Fe0/UV systems. In addition, WV irradiation plays only a minor role in the Fe0/UV/H2O2 system, in view of TCM dechlorination. Application of small amount of H2O2 results in the increase of Fe2+ accumulation rate in the Fe0/H2O2 system. CONCLUSIONS: TCM was dechlorinated mostly through post Fenton oxidation; reductive reaction represents a less efficient way to dechlorinate TCM. The efficiencies of overall TCM dechlorination for the two systems of Fe0/H2O2 and Fe0/UV/ H2O2 are comparable to each other, and this implies that the presence of UV irradiation imposes no significant enhancement. RECOMMENDATIONS AND OUTLOOKS: It is highly recommended to initiate effective redox dechlorination of TCM with the system of Fe0/H2O2, where the H2O2 in excess is applied at a later reaction time point.     

Irradiation of sorbents by ions of polymorphic metals for modeling <Superscript>90</Superscript>strontium sedimentation

Background, Aims and Scope Advances in radioecology can support improvements in environmental remediation technologies, especially by illuminating interaction processes between polymorphic metal radionuclides and various materials and their ions in aqueous solutions. This study modeled interaction processes of ⁹⁰Sr with transitive metals to delineate the behavior of polymorphic metal radionuclides. Experimental and modeling results confirmed Sr sedimentation was sensitive to the physical impact of radionuclides on various sorbents and possible chemical reactions occurring between the radionuclides and sorbents. Methods Models were developed to simulate ⁹⁰Sr sedimentation process, and the potential physical and chemical reactions accompanying the process. Models were verified, inorganic salts were used as sorbents to absorb metal cations, activity levels were recorded before and after mixing the inorganic salts while the efficiency of sedimentation using the heavy metals composites was quantified. Results and Discussion This research demonstrates that the process of the sedimentation is complex and occurs in several stages. Micro-structural analysis shows that zones of interaction between the sorbent and source metal are formed during the irradiation of the target’s metal surface. Electrical-microscopic analysis indicates that the composition of the formed zones of interaction of Ti (Sr) with target metals has various structures. Roentgenophase analysis indicates that the interaction of the ions of a precipitable source and a target occurs according to constitution diagrams of equilibrium systems. The results indicate that application of inorganic salts composites based on modeling increases the efficiency of the deactivation of aqueous solutions when compared to standard aluminum sulfate composite. Conclusions Experimental and modeling results confirm ⁹⁰Sr sedimentation is sensitive to the physical impact of radionuclides on various sorbents and possible chemical reactions occurring between the radionuclides and sorbents. The models support estimation of the physical impact of polymorphic metal radionuclides on various components of sorbents and possible chemical reactions occurring between the radionuclides and sorbents during the interaction. Inorganic salt composites deactivate and clear ⁹⁰Sr and Sr⁺² from water. This paper is openly accessible!     

Hg<Superscript>2+</Superscript> detection using a disposable and miniaturized screen-printed electrode modified with nanocomposite carbon black and gold nanoparticles

A miniaturized screen-printed electrode (SPE) modified with a carbon black-gold nanoparticle (CBNP-AuNP) nanocomposite has been developed as an electrochemical sensor for the detection of inorganic mercury ions (Hg²⁺). The working electrode surface has been modified with nanocomposite constituted of CBNPs and AuNPs by an easy drop casting procedure that makes this approach extendible to an automatable mass production of modified SPEs. Square wave anodic stripping voltammetry (SWASV) was adopted to perform Hg²⁺ detection, revealing satisfactory sensitivity and detection limit, equal to 14 μA ppb^?1 cm^?2 and 3 ppb, respectively. The applicability of the CBNP-AuNP-SPE for the determination of inorganic mercury has been assessed in river water by a simple filtration and acidification of the sample as well as in soil by means of a facile acidic extraction procedure assisted by ultrasound.     

Characteristics of phosphorus components in surface sediments from a Chinese shallow eutrophic lake (Lake Taihu): new insights from chemical extraction and <Superscript>31</Superscript>P NMR spectroscopy

As a primary factor responsible for lake eutrophication, a deeper understanding of the phosphorus (P) composition and its turnover in sediment is urgently needed. In this study, P species in surface sediments from a Chinese large eutrophic lake (Lake Taihu) were characterized by traditional fractionation and ³¹P nuclear magnetic resonance (NMR) spectroscopy, and their contributions to the overlying water were also discussed. Fractionation results show that NaOH-P predominated in the algal-dominated zone, accounting for 60.1% to total P in Zhushan Bay. Whereas, refractory fractions including HCl-P and residual-P were the main P burial phases in the macrophyte-dominated zone, the center and lakeshore. Recovery rates of the total P and organic P were greatly improved by using a modified single-step extraction of NaOH-EDTA, ranging from 22.6 to 66.1% and from 15.0 to 54.0%. Ortho-P, monoester-P, and pyro-P are identified as the major P components in the NaOH-EDTA extracts by ³¹P NMR analysis. Trace amount of DNA-P appeared only in sediments from algal- and macrophyte-dominated zones, ascribing to its biological origin. The relative content of ortho-P is the highest in the algal-dominated zone, while the biogenic P including ester-P and pyro-P is the highest in the macrophyte-dominated zone. Moreover, ortho-P and pyro-P correlated positively with TP and chlorophyll a in the overlying water, whereas only significant relationships were found between monoester-P, biogenic P, and chlorophyll a. These discrepancies imply that inorganic P, mainly ortho-P, plays a vital role in sustaining the trophic level of water body and algal bloom, while biogenic P makes a minor contribution to phytoplankton growth. This conclusion was supported by the results of high proportion of biogenic P in algae, aquatic macrophytes, and suspended particulate from the published literature. This study has significant implication for better understanding of the biogeochemical cycling of endogenous P and its role in affecting lake eutrophication.     

Investigation of low-level <Superscript>242</Superscript>Pu contamination on nutrition disturbance and oxidative stress in <Emphasis Type="Italic">Solanum tuberosum</Emphasis> L.

Plutonium associated with higher molecular weight molecules is presumed to be poorly mobile and hardly plant available. In our present study, we investigate the uptake and effects of Pu treatments on Solanum tuberosum plants in amended Hoagland medium at concentrations of [²⁴²Pu] = 100 and 500 nm, respectively. We found a direct proof of oxidative stress in the plants caused by these rather low concentrations. For the confirmation of oxidative stress, we explored the production of nitric oxide (NO) and hydrogen peroxide (H₂O₂) by epifluorescence microscopy. Oxidative stress markers like lipid peroxidation and superoxide radicals (O₂ ^??) are monitored through histochemical analysis. The biochemical parameters i.e. chlorophyll and carotenoids are measured as an indicator of cellular damage in the tested plants including the enzymatic parameters such as catalase and glutathione reductase. From our work, we conclude that Pu in low concentration has no significant effects on the uptake of many trace and macroelements. In contrast, the content of O₂ ^?? , malondialdehyde (MDA), and H₂O₂ increases with increasing Pu concentration in the solution, while the opposite effects was found for NO, catalase, and glutathione reductase. These findings prove that even low concentration of Pu regulates ROS production and generate oxidative stress in S. tuberosum L.     

The Asian nitrogen cycle case study

We analyzed nitrogen budgets at national and regional levels on a timeline from 1961-2030 using a model, IAP-N 1.0. The model was designed based upon the Inter-governmental Panel on Climate Change (IPCC) methods using Asia-specific parameters and a Food and Agriculture Organization of the United Nations (FAO) database. In this paper we discuss new reactive-nitrogen and its various fates, and environmental nitrogen enrichment and its driving forces. The anthropogenic reactive nitrogen of Asia dramatically increased from approximately 14.4 Tg N yr-1 in 1961 to approximately 67.7 Tg N yr-1 in 2000 and is likely to be 105.3 Tg N yr-1 by 2030. Most of the anthropogenic reactive-nitrogen has accumulated in the environment. We found that an increasing demand for food and energy supplies and the lack of effective measures to improve the efficiency of fertilizer nitrogen use, as well as effective measures for the prevention of NOx emissions from fossil-fuel combustion, are the principal drivers behind the environmental nitrogen-enrichment problem. This problem may be finally solved by substituting synthetic nitrogen fertilizers with new high-efficiency nitrogen sources, but solutions are dependent on advances in biological technology.     

Effective dose estimation and lifetime cancer mortality risk assessment from exposure to Chernobyl <Superscript>137</Superscript>Cs on the territory of Belgrade City and the region of Vojvodina,Serbia

Purpose  

The purpose of this paper is to determine the activity concentrations of radionuclide ¹³⁷Cs in soil samples on the territory of Belgrade and the province of Vojvodina. Also, the lifetime cancer mortality risk from external exposure during 1 year is assessed, and the effective dose is estimated.     

Transition to Non-toxic Gunshot Use in Olympic Shooting: Policy Implications for IOC and UNEP in Resolving an Environmental Problem

Olympic shooters discharge, annually, thousands of tons of lead shot which pose toxic risks to animals and may pollute both surface and ground waters. Non-toxic steel shot is an acceptable and effective substitute, but International Shooting Sports Federation (ISSF) rules prevent its adoption. The present policy and rules of the ISSF on lead shot use contravene the International Olympic Committee (IOC) Charter position on environmental protection. The United Nations Environment Programme (UNEP), a formal Olympic partner on environmental protection, has no stated policy on contamination from lead ammunition, despite having declared lead a Priority Area for remedial action, and is pressing to remove lead from the global human environment. The IOC Sport and Environment Commission and UNEP could examine the continued use of lead shot ammunition and advise the IOC Executive Board on appropriate changes in policy and rules that could halt the massive lead shot contamination of shooting range environments world-wide.     

Long-range transport of polycyclic aromatic hydrocarbons (PAHs) from the eastern Asian continent to Kanazawa,Japan with Asian dust

Aerosol particles were collected for 1 year, starting in April 2003, in rural areas of Kanazawa, Ishikawa, Japan to understand the role of Asian dust as a long-range transporter of polycyclic aromatic hydrocarbons (PAHs). Three sampling intervals were designated in this study, namely: (1) Dust period 1 (March 11–19, 2003); (2) Dust period 2 (March 28, 2003–April 9, 2003); and (3) Dust period 3 (April 9, 2004–April 25, 2004). The Asian dust particles are predominantly in the coarse particle size range (2.1–11 μm). PAH analyses were performed separately on both the coarse and fine (<1.1 μm) particle ranges. Seasonal trends in PAH concentrations for coarse and fine particles showed that the Asian dust particles in Dust period 3 contained significant amounts of less-volatile PAHs such as benzo[a]pyrene (BaP) and benzo[g,h,i]perylene (BghiP). A kinetic model developed in this study shows that almost none of these PAHs would be accumulated on Asian dust particles in the atmosphere, due to their extremely slow adsorption rates. These PAHs would have to originate from PAH-polluted soil particles around industrialized areas. Back trajectory analyses suggest that the Asian dust in Dust period 3 came from loess regions around industrialized areas. This indicates that geologic materials play a significant role in the atmospheric circulation of PAHs.     

The chemical and strontium isotope composition of atmospheric aerosols over Japan: the contribution of long-range-transported Asian dust (Kosa)

Atmospheric aerosols have been collected at four sites around Japan during 2000. From systematically monitoring the major (Na, Mg, Al, K, Ca, and Fe) and trace (Rb and Sr) elements, along with the Sr isotope composition, we have tried to estimate the contribution of long-range-transported Asian dust (“Kosa”) to the atmospheric aerosols.The results are summarized as follows:(1) The concentration of each element in the aerosols increased during the “Kosa” period. The increase was particularly obvious in samples collected on 8 April 2000, when the “Kosa Phenomenon” was observed at all the sampling sites in Japan, 2 days after a very heavy dust storm had occurred in China.(2) The Rb–Sr isotopic diagram shows a two-component mixing relationship: one with a high ⁸⁷Sr/⁸⁶Sr ratio and a high ⁸⁷Rb/⁸⁶Sr ratio, and the other with a low ⁸⁷Sr/⁸⁶Sr ratio and a low ⁸⁷Rb/⁸⁶Sr ratio. There is a significant difference between that of the expected end member of the Asian dust and that of the reported Asian loess, which is thought to be the possible source of the components of the “Kosa”, although the lower component is consistent with the local component at Wako.(3) Plots of the ⁸⁷Sr/⁸⁶Sr ratio vs the Ca/Al and Sr/Al ratios support a two-component mixing suggested by the Rb–Sr systematics, and they indicate that the contributing continental soil components to the “Kosa” aerosols should be composed of the silicate fraction of Asian loess.(4) The discrepancy in the Rb–Sr systematics between the expected end member and the possible sources may be caused by the dissolution of the Ca-bearing minerals via long-range dust transport, or by a combination of source characteristics and grain size separation.     

Atomization and Cloud Behavior In Venturi Scrubbing

The exact collection mechanism of a venturi scrubber has been unknown up to this time. Photographic stop-action techniques and glass venturi scrubbers have made it possible to establish where and how particles are captured and to speculate on possible gas removal possibilities. This report extends the knowledge of pneumatic atomization which is used in gas scrubbing and many other applications by providing further information on cloud-type atomization. Cloud-type atomization which is produced by pneumatic atomization of liquid streams (not drops) results in the formation of liquid droplets which appear to be less than 10 microns in diameter. These droplets coalesce and form clouds which move as single entities. Effective overall cloud diameters are determined to be a function of the velocity of the atomizing gas stream. The effective cloud diameters start at 170 [a and increase as throat gas velocities increase from 150 ft/sec. Throat velocities and liquid inlet nozzle diameters necessary to obtain water clouds of specific effective diameters can be estimated.

These large clouds are efficient impaction targets and stop most of the particulate matter within 0.5 cm from the throat scrubbing liquid inlets. High gas absorption is expected for the clouds of droplets because turbulent gas movement can exist inside and outside the clouds and the 10 μ droplets provide exceptional surface area.     

The Prediction of the Rise of a Hot Cloud from Field Experiments

The rise of a hot cloud resulting from combustion of a solid propellant rocket fuel at ground level has been determined from lapse-time movies and visual aircraft observations. The field tests were conducted near the 420 foot meteorological tower under various atmospheric conditions. A method of predicting the maximum thermal rise of a cloud, based on source and meteorological parameters, is described. Comparisons with other theoretical formulations are presented.