The Arctic region is the most sensitive region to climate change. Hydrological models are fundamental tools for climate change impact assessment. However, due to the extreme weather conditions, specific hydrological process, and data acquisition challenges in the Arctic, it is crucial to select suitable hydrological model(s) for this region. In this paper, a comprehensive review and comparison of different models is conducted based on recently available studies. The functionality, limitations, and suitability of the potential hydrological models for the Arctic hydrological process are analyzed, including: (1) The surface hydrological models Topoflow, DMHS (deterministic modeling hydrological system), HBV (Hydrologiska Byråns Vattenbalansavdelning), SWAT (soil and water assessment tool), WaSiM (water balance simulation model), ECOMAG (ecological model for applied geophysics), and CRHM (cold regions hydrological model); and (2) the cryo-hydrogeological models ATS (arctic terrestrial simulator), CryoGrid 3, GEOtop, SUTRA-ICE (ice variant of the existing saturated/unsaturated transport model), and PFLOTRAN-ICE (ice variant of the existing massively parallel subsurface flow and reactive transport model). The review finds that Topoflow, HBV, SWAT, ECOMAG, and CRHM are suitable for studying surface hydrology rather than other processes in permafrost environments, whereas DMHS, WaSiM, and the cryo-hydrogeological models have higher capacities for subsurface hydrology, since they take into account the three phase changes of water in the near-surface soil. Of the cryo-hydrogeological models reviewed here, GEOtop, SUTRA-ICE, and PFLOTRAN-ICE are found to be suitable for small-scale catchments, whereas ATS and CryoGrid 3 are potentially suitable for large-scale catchments. Especially, ATS and GEOtop are the first tools that couple surface/subsurface permafrost thermal hydrology. If the accuracy of simulating the active layer dynamics is targeted, DMHS, ATS, GEOtop, and PFLOTRAN-ICE are potential tools compared to the other models. Further, data acquisition is a challenging task for cryo-hydrogeological models due to the complex boundary conditions when compared to the surface hydrological models HBV, SWAT, and CRHM, and the cryo-hydrogeological models are more difficult for non-expert users and more expensive to run compared to other models.

Background Most studies on air pollution exposure and its associations with human health in China have focused on the heavily polluted industrial areas and/or mega-cities, and studies on cities with comparatively low air pollutant concentrations are still rare. Only a few studies have attempted to analyse particulate matter (PM) for the vibrant economic centre Shenzhen in the Pearl River Delta. So far no systematic investigation of PM spatiotemporal patterns in Shenzhen has been undertaken and the understanding of pollution exposure in urban agglomerations with comparatively low pollution is still limited. Methods We analyze daily and hourly particulate matter concentrations and all-cause mortality during 2013 in Shenzhen, China. Temporal patterns of PM (PM_2.5 and PM₁₀) with aerodynamic diameters of 2.5 (10) μm or less (or less (including particles with a diameter that equals to 2.5 (10) μm) are studied, along with the ratio of PM_2.5 to PM₁₀. Spatial distributions of PM₁₀ and PM_2.5 are addressed and associations of PM₁₀ or PM_2.5 and all-cause mortality are analyzed. Results Annual average PM₁₀ and PM_2.5 concentrations were 61.3 and 39.6 μg/m³ in 2013. PM_2.5 failed to meet the Class 2 annual limit of the National Ambient Air Quality Standard. PM_2.5 was the primary air pollutant, with 8.8 % of days having heavy PM_2.5 pollution. The daily PM_2.5/PM₁₀ ratios were high. Hourly PM_2.5 concentrations in the tourist area were lower than downtown throughout the day. PM₁₀ and PM_2.5 concentrations were higher in western parts of Shenzhen than in eastern parts. Excess risks in the number of all-cause mortality with a 10 μg/m³ increase of PM were 0.61 % (95 % confidence interval [CI]: 0.50–0.72) for PM₁₀, and 0.69 % (95 % CI: 0.55–0.83) for PM_2.5, respectively. The greatest ERs of PM₁₀ and PM_2.5 were in 2-day cumulative measures for the all-cause mortality, 2-day lag for females and the young (0–65 years), and L02 for males and the elder (>65 years). PM_2.5 had higher risks on all-cause mortality than PM₁₀. Effects of high PM pollution on mortality were stronger in the elder and male. Conclusions Our findings provide additional relevant information on air quality monitoring and associations of PM and human health, valuable data for further scientific research in Shenzhen and for the on-going discourse on improving environmental policies.

Russia has experienced population decline in years and the economic development in Russia is largely restricted by labor shortage, particularly for the Far North and East region. In order to explore the migration mechanisms, six socioeconomic factors were selected to explore the influences on the net migration. Data from the 82 regions covering four time periods (2000, 2005, 2010 and 2015) was processed use spatial panel econometric analysis and the time-period fixed effects Spatial Durbin Model (SDM) was selected as the best fit model after tests. The results indicates that, unemployment and infant death rate are significantly negatively associated with net migration, while urbanization rate, urban scale and life expectancy are significantly positively associated with net migration; every 100 USD increase in per capita GRP (Gross Regional Product) is positively related with averagely 5.4 net migrates in the region; every 1 year increase in life expectancy would increase 1052 net migrates; every 1sqm increase in urban scale would increase the net migrates by 11.75 and every 1% increase in unemployment would lead to a decrease of 0.54 net migrates. Spillover effect was also found for per capita GRP and life expectancy, indicating that the increase of per capita GRP and life expectancy in neighboring regions can also increase the attractiveness in one region. It can be concluded that better job market, better economic status and health related wellbeing are all attracting factors for migrates and these factors can even make the neighborhood region more attractive for immigrates. Considering the ambitious development plan for the Russia Far North and East regions, related suggestions on attracting migrates are provided.

Removal of vanadium from liquid waste streams protects the environment from toxic vanadium species and promotes the recovery of the valuable metal. In this study, real mining ditch water was sampled from a closed vanadium mine (V-Fe-Ti oxide deposit, Finland) and used in sorption experiments at prevailing vanadium concentration (4.66-6.85 mg/L) and pH conditions (7.02-7.83). The high concentration of vanadium in the water represents a potential health concern according to the initial risk assessment carried out in this study. Vanadium was efficiently removed using four different iron sorbents: ferric oxyhydroxide with some goethite (CFH-12), poorly crystallized akaganéite (GEH 101), ferric groundwater treatment residual (GWTR), and GWTR-modified peat (GWTR-Peat). Higher dosage (6 g/L with 24 h contact time) and longer contact time (72 h using 1 g/L dosage) resulted in removal efficiencies of higher than 85%. Kinetic data were well represented by the Elovich model while intra-particle diffusion and Boyd models suggested that the sorption process in a real water matrix was significantly controlled by both film diffusion and intra-particle diffusion. Column studies with CFH-12, GEH 101, and GWTR-Peat showed that the breakthrough started earlier with the mining ditch water compared to a synthetic vanadium solution (investigated only with CFH-12), whereas GEH 101 proved to have the best performance in column mode. The Thomas and Yoon-Nelson column models were found to agree with the experimental data fairly well with the 50% breakthrough time being close to the experimental value for all the studied sorbents.