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[en] Highlights: • O3 and KMnO4 based pretreatments caused an increase in N-nitrosamines. • Drinking water treatment systems efficiently removed N-nitrosamines precursors. • NDPhA and NMOR were found resistant toward all treatment processes. • Distribution networks also played a role in generating N-nitrosamines. • Most N-nitrosamines were far below the cancer risk level. The occurrence of mutagenic and carcinogenic N-nitrosamines in drinking water is of great concern. In this study, dynamics and removal of nine N-nitrosamines in three drinking water treatment systems of a southern city of China are monitored during one year of sampling. The impacts of physicochemical treatment units on the removal and generation of N-nitrosamines were evaluated. The O3 and KMnO4 based pre-oxidation units have caused an increase in N-nitrosamines concentration, with O3 showing the substantial generation of N-nitrosamines. The carbon filter and ultrafiltration membrane units were found effective in removing N-nitrosamine precursors. These drinking water treatment systems have been useful in removing N-nitrosamine precursors; meanwhile, a slight decrease was found in already formed N-nitrosamines concentration. However, N-nitrosomorpholine (NMOR) and N-nitrosodiphenylamine (NDPhA) were found resistant toward all kinds of physicochemical treatments, and negligible changes in concentration were noted in all drinking water treatment systems. The distribution networks in the city provided an effective contact period to residual chlorine and precursors, which caused an increase in N-nitrosamines concentration. Overall, N-nitrosodimethylamine (NDMA) and N-nitroso-diethylamine (NDEA) have been found near the cancer risk threshold (10−6) in all of the drinking water treatment systems, while the remaining seven N-nitrosamines were found below the risk level.
[en] Highlights: • A new method of caculating aerosol extinction coeificent by AOD dividing the mixing layer height was established. • NR-PM1 and black carbon together contributed about 88% to the whole aerosol light extinction. • Contribution of organics to light extinction increased on polluted days. • Aerosol extinction coefficient increased rapidly when the ratio of of NR-PM1 and BC reached 7. An aerosol mass spectrometer (AMS) was used to measure the chemical composition of non-refractory submicron particles (NR-PM1) in Beijing from 2012 to 2013. The average concentration of NR-PM1 was 56 μg·m−3, with higher value of 106 μg·m−3 when Beijing was influenced by air masses from south in winter. Organics was the primary chemical component with a concentration of 26 μg·m−3, accounting for 46% of the total NR-PM1. The ratio of NO3−/SO42− was utilized to identify the relative contribution of stationary and traffic related resource to PM pollution. When NR-PM1 concentration was between 50 and 200 μg·m−3, NO3−/SO42−was larger than 1, indicating traffic resource contributed more than stationary resource during the aerosol growth. A new method was developed to calculate aerosol extinction coefficient (σ) as a function of aerosol optical depth (AOD) and the mixing layer height (MLH). σ derived from the new method showed a statistically significant correlation with that obtained from traditional method, which was calculated using visibility (y = 0.99x + 85 R2 = 0.69). Multiple linear regressions in dependence of chemical component were performed to evaluate light extinction apportionment. Under the overall condition, NR-PM1 contributed about 88% to the whole aerosol light extinction; organics, ammonium chloride, ammonium nitrate, ammonium sulfate, black carbon contributed 30%, 6%, 24%, 26% and 6% of the NR-PM1 light extinction, respectively. By further comparing the light extinction apportionment under the different dominated air masses, we concluded that the organics and ammonium sulfate contributed more in polluted days (36% and 23%) than that in clean days (21% and 21%). Mass ratio (MR) between NR-PM1 and black carbon (MR = massNR-PM1/massBC) was used to identify black carbon aging degree, and the result showed that aerosol mass extinction efficiency increased rapidly after MR reached about 7 in the process of black carbon aging.
[en] Highlights: • A new environmental material EHPDI was synthesized. • Novel perylene diimide derivative/TiO2 photocatalyst was prepared for activating PS. • The activation mechanism of EPT/PS system under visible light was investigated. • The possible degradation pathways of carbamazepine were proposed. Removal of pharmaceutical and personal care products from wastewater is very important in water treatment process. Combining photocatalysis with persulfate (PS) could be a good solvent for this problem. Novel perylene diimide derivative (EHPDI) was designed and synthesized. Furthermore, self-assembled EHPDI/TiO2 composite photocatalyst (EPT) was prepared and applied in activating persulfate (PS) under visible light to enhance the photodegradation of pollutants. The presence of the alkyl side chain 2-ethylhexyl optimizes the self-assembly process, enabling the composite material to achieve high performance under low EHPDI loading. Various methods were used to detect the physical and chemical characteristics of EPT. Carbamazepine (CBZ) was chosen to be the model pollutant to study the removal efficiency of EPT/PS system under visible light. Within 30 min, 5.0 mg/L CBZ could be almost completely degraded, and the removal ratio of TOC was 75.2% within 60 min. The SO4–, OH, O2–, 1O2, and h+ were proved to be involved in the removal of CBZ by EPR and quenching experiments. Then, other typical pollutants were degraded by this EPT/PS system, demonstrating this system is suitable for degrading different pollutants. Besides, the degradation paths of CBZ were proposed by HPLC/MS. Finally, the EPT showed excellent recyclability and stability.
[en] Highlights: • OA and OW have deleterious effects on the fitness of T. niloticus. • Co-exposure of OA and OW is the most stressful condition. • OA and OW may adversely affect population replenishment of T. niloticus. Scientific researches have clearly indicated that ocean acidification and warming poses serious threats to coral reef ecosystems. In coral reef ecosystems, herbivorous gastropods have an important function in maintaining the stability of the ecosystem due to controlling the abundance and growth of macroalgal, which compete for nutrients and space with coral. However, limited knowledge is available on the physiological responses of the specific keystone species to the increased ocean acidity and thermal stress. In this study, we evaluated the effects of ocean acidification (OA) and warming (OW) on an herbivorous gastropod Trochus niloticus commonly found on intertidal and shallow subtidal coral reefs in the South China Sea, on the aspect of immune responses (total hemocyte counts, reactive oxygen species level and apoptosis rate), oxidative stress (lipid peroxidation level, antioxidant enzyme activities), neurotoxicity (acetylcholinesterase activity), and energy metabolism (respiration rate and cellular energy allocation), after a 28-day exposure experiment to acidic (pH 7.6) and/or thermal (30 °C) seawater. Our results demonstrated that both OA and OW could lead to physiological disturbances of the herbivorous top-shells, including impaired immune functions and oxidative balance, neurotoxicity, and disorder of energy metabolism. Furthermore, results of integrated biomarker response (IBR) confirmed that the overall fitness of T. niloticus were deleteriously impacted by OA and OW, and were more stressed under the co-exposure condition. These results indicated that increased acidity and temperature in the future ocean might impair the viability of T. niloticus in the long-run, which will indulge the proliferation of macroalgae and lead to degradation of the coral reef ecosystem.
[en] Highlights: • An imbalance between N inputs and outputs is observed at the local scale. • N mass stored in the aquifer is constantly increasing. • Variables debated during a governance process can be treated as input data to models. • Numerical models contribute to solve information and capacity governance gaps. The EU Nitrate Directive has been ruling for almost 30 years, nevertheless nitrate concentration in the Lombardy Plain did not decrease. Together with failures of management implementation, a possible cause for such field observations is that management actions were taken without adequately considering the actual hydrogeological dynamics. To consider this aspect, the paper presents a groundwater flow and transport numerical model of a specific area of the Lombardy Plain. The aim of this model is to demonstrate how modelling, as a management tool, can be useful in the governance process. The groundwater model, using well-known MODFLOW-MT3D codes, is based on existing hydrogeological information, while a nitrogen mass balance has been performed at municipal scale to determine the agricultural N surplus to the subsurface. The model adequately reproduces head levels and nitrate concentrations in observation wells for a 10-year simulation period, showing that 4.5% of the N annual input remains stored in the system. The model indicates the efficiency of rivers and springs to export N out from the system at an estimated rate of 77.5% of the annual N inputs. Back to governance, the model shows that management data at municipal level (e.g. irrigation rates, groundwater withdrawal, N net recharge) provide a satisfactory scale for successfully reproducing nitrate evolution. Hence those variables that can be object of debate during a governance process can be treated as input data to the numerical model. Therefore, backcasting exercises can be conducted to check whether the model outcome fits with the expected results of specific management actions. The model highlights how the N mass balance evolves, providing clues on which factors can be managed to reduce nitrate concentrations and meet the Directive's requirements. Numerical groundwater models, as an option to address water management issues, ultimately contribute to solve the information and capacity governance gaps.
[en] Highlights: • Tectonics is important in the land-use planning of tectonically active regions. • The characterization of the physical environment requires comprehensive studies. • Geology allows knowing the distribution of natural hazards in the land. • Tectonics can be used to define homogeneous environmental units. In this research, emphasis is placed on the information and diagnostic phase of the physical environment for land-use planning (LUP). Our work is mainly focused on a land-planning case study of a tectonic depression, the Tulum Valley, which extends into the Pampean flat-slab segment. We propose the use of tectonic structures to define Environment Units (EUs) as necessary boundaries for the LUP. For this purpose, we have studied tectonic structures using geophysical methods and, subsequently, subjected multiple dimensions of the physical environment in the territory to an exhaustive analysis. Moreover, we have examined the influence of structural geology on water, soils, processes, materials and forms in the landscape. The study revealed the close and significant relationship between the different elements of the physical environment observable on the surface (shape, distribution, appearance, degree of development) and the tectonic structures, which supported the use of this criterion to define EUs. In order to test it, we applied the same methodology in another area of South America, the city of Bucaramanga, where it was possible to define EUs based on tectonics and to also establish comparisons. The methodology proposed for the diagnostic phase based mainly on the tectonic factor represents a challenge as regards its application in other active tectonic zones. Some limitations could arise such as fragmented environmental information from different institutions or the small to non-existent number of tectonic studies available. As a strong point, we find that the method allows achieving a comprehensive study of the environmental setting and thus to propose activities and land uses in each EU according to the real reception capacity of the land. This exhaustive analysis of the physical environment will also help decision-makers to understand and manage the socio-natural risks of the territory where communities develop.
[en] Highlights: • An osmotic sampler was constructed for time-series sampling of trace metals in water. • The injected air segments could effectively separate time-series samples. • The addition of 30% HNO3 could in situ preserve trace metals in collected samples. • Time-series concentrations of trace metals in water were measured using the sampler. High-resolution time-series concentrations (CTS) are very important for the investigation of the biogeochemical processes of trace metals in the aquatic environment. However, the acquisition of CTS of trace metals in water is still challenging because of the lack of suitable samplers. In this study, an osmotic sampler coupled with air segment injection and preservative addition was employed for time-series sampling of trace metals in surface waters. In the sampler, water sampling and preservative adding are both driven by osmotic pumps (OPs), while air segment injection is accomplished by a timer-controlled micro diaphragm pump. During deployment, the sampling OP continuously draws water through a filter and stores it in a narrow-bore coil. Simultaneously, a preservative OP slowly pushes 30% HNO3 (v/v) into the collected sample for in situ preservation. Periodically, the micro diaphragm pump injects air into the continuous water stream to divide it into water segments, enabling accurate time-stamping. After retrieval, the time-series samples were pumped out from the coil and re-collected to analyze the CTS of analytes. The sampler was deployed in river, reservoir, and marine waters for 26 h and one week to measure CTS of trace metals at time resolutions of 2 h and 12 h. Results showed that the recoveries of a preloaded standard mixture (1.0 μg/L) in all samplers ranged from 93.1% to 117.8%. The measured CTS of Cd, Co, Cr, Cu, Mn, and Ni in the waters only varied in small ranges. Accordingly, the measured CTS data from the sampler were consistent with the obtained concentrations from grab sampling. The relative percent differences between the measurements from two samplers were less than 37.4%. These results demonstrate the reliability and accuracy of the sampler for time-series sampling of the chosen trace metals in surface waters.
[en] Highlights: • Eutrophication affects macrophytes through various pathways. • Increase in nutrients affects dissolved inorganic carbon influencing macrophytes. • Separation of macrophyte assemblages can be detected along the bicarbonate gradient. • Management should consider interactions of nutrients and dissolved inorganic carbon. Nitrogen and phosphorous concentrations are widely considered to drive macrophyte assemblages in rivers. However, Dissolved Inorganic Carbon (DIC) – available for plants as CO2 and HCO3− – is also of major relevance. Based on literature, we present a conceptual model on the interaction between algae, macrophytes, DIC, pH, light, N, P and the surface water and sedimental compartment. Analysing two separate datasets (i) on river physico-chemistry and chlorophyll-a, and (ii) on river physico-chemistry and macrophytes we quantify three connections within this concept: (1) the correlation of chlorophyll-a versus pH, (2) the correlation of TP versus chlorophyll-a and (3) the occurrence of HCO3-users and CO2-only-users among macrophytes along the DIC gradient. Chlorophyll-a correlated positively with pH (R-squared = 77%, p < .001) due to increased carbon dioxide uptake of phytoplankton. Surface water TP did not linearly correlate with chlorophyll-a concentrations. Obligate and optionally submerged macrophyte species that utilise HCO3− were separated from CO2-only-users by HCO3− concentrations, with an area under the curve (AUC) of 68% and 70% (both p < .001) between groups. Obligate and optionally submerged macrophyte assemblages only composed of HCO3-users and those exclusively composed of CO2-only-users showed an even stronger separation based on the HCO3− concentration, with both an AUC of 82% and 78% (both p < .001). Our results underline that DIC can greatly affect riverine macrophytes. However, absolute concentrations of HCO3− are less relevant, while the connection to pH is more important, reflecting CO2 concentrations. River monitoring and management should consider the interaction between nutrients DIC, surface water and sedimental compartment as important factors affecting macrophyte occurrence, rather than solely focussing on surface water nutrients.
[en] Highlights: • Substitution of 20–30% peat moss by biochar in potting substrate is supported. • Addition of 2% biochar to concrete achieves non-structural strength in mortar. • On-site biochar production saves waste disposal and planting substrate costs. Organic waste, the predominant component of global solid waste, has never been higher, resulting in increased landfilling, incineration, and open dumping that releases greenhouse gases and toxins that contribute to global warming and environmental pollution. The need to create and adopt sustainable closed-loop systems for waste reduction and valorization is critical. Using organic waste as a feedstock, gasification and pyrolysis systems can produce biooil, syngas, and thermal energy, while reducing waste mass by as much as 85–95% through conversion into biochar, a valuable byproduct with myriad uses from soil conditioning to bioremediation and carbon sequestration. Here, we present a novel case study detailing the circular economy of gasification biochar in Singapore's Gardens by the Bay. Biochar produced from horticultural waste within the Gardens was tested as a partial peat moss substitute in growing lettuce, pak choi, and pansy, and found to be a viable substitute for peat moss. At low percentages of 20–30% gasification biochar, fresh weight yields for lettuce and pak choi were comparable to or exceeded those of plants grown in pure peat moss. The biochar was also analyzed as a potential additive to concrete, with a 2% biochar mortar compound found to be of suitable strength for non-structural functions, such as sidewalks, ditches, and other civil applications. These results demonstrate the global potential of circular economies based on local biochar creation and on-site use through the valorization of horticultural waste via gasification, generating clean, renewable heat or electricity, and producing a carbon-neutral to -negative byproduct in the form of biochar. They also indicate the potential of scaled-up pyrolysis or gasification systems for a circular economy in waste management.
[en] Highlights: • N2O samples from static chambers (• Site preference (‰) and soil WFPS (%) used to determine N2O production pathways. • Daily N2O fluxes attributed to 34.2% nitrification and 29.0% denitrification. • δ15Nbulk and SP (drier soil) indicate ribwort plantain may inhibit nitrification. • SP drop with increasing WC (wet soil) implies stimulation of denitrification. Nitrous oxide (N2O) is a potent greenhouse gas (GHG) emitted from agricultural soils and is influenced by nitrogen (N) fertiliser management and weather and soil conditions. Source partitioning N2O emissions related to management practices and soil conditions could suggest effective mitigation strategies. Multispecies swards can maintain herbage yields at reduced N fertiliser rates compared to grass monocultures and may reduce N losses to the wider environment. A restricted-simplex centroid experiment was used to measure daily N2O fluxes and associated isotopomers from eight experimental plots (7.8 m2) post a urea-N fertiliser application (40 kg N ha−1). Experimental pastures consisted of differing proportions of grass, legume and forage herb represented by perennial ryegrass (Lolium perenne), white clover (Trifolium repens) and ribwort plantain (Plantago lanceolata), respectively. N2O isotopomers were measured using a cavity ring down spectroscopy (CRDS) instrument adapted with a small sample isotope module (SSIM) for the analysis of gas samples ≤20 mL. Site preference (SP = δ15Nα – δ15Nβ) and δ15Nbulk ((δ15Nα + δ15Nβ) / 2) values were used to attribute N2O production to nitrification, denitrification or a mixture of both nitrification and denitrification over a range of soil WFPS (%). Daily N2O fluxes ranged from 8.26 to 86.86 g N2O-N ha−1 d−1. Overall, 34.2% of daily N2O fluxes were attributed to nitrification, 29.0% to denitrification and 36.8% to a mixture of both. A significant diversity effect of white clover and ribwort plantain on predicted SP and δ15Nbulk indicated that the inclusion of ribwort plantain may decrease N2O emission through biological nitrification inhibition under drier soil conditions (31%–75% WFPS). Likewise, a sharp decline in predicted SP indicates that increased white clover content could increase N2O emissions associated with denitrification under elevated soil moisture conditions (43%–77% WFPS). Biological nitrification inhibition from ribwort plantain inclusion in grassland swards and management of N fertiliser source and application timing to match soil moisture conditions could be useful N2O mitigation strategies.