Water resources have major effects on the temporal and spatial distribution of land use in oases and arid regions. To determine the response relation between water consumption and the land use of the oasis in the Tarim river basin, Xinjiang, China, we conducted a study analyzing the temporal and spatial synchronization in this basin by employing hydrological data, land-use maps (for 2000, 2005, and 2010), and the spatial analysis tool ArcGIS. Results show that the water consumption in the Tarim river basin fluctuated noticeably from 2000 to 2010 and was mainly concentrated in July. A close relationship was established between land-use type and water body, and the range of land fluctuation was related to the distance between these two variables. A turning point was observed two kilometers from the land site to the water body for most land-use types. The dynamic degree of unused land, forest land and grassland decreased continuously, whereas that of cultivated land, farmland and residential land increased continuously. The increase and decrease were primarily concentrated in the cultivated and unused lands, respectively. These findings also have implications in the exploration of water resources management, changing water consumption and its effects on the land use of oasis in Tarim river basin.

Urban environmental pollution intensifies with the acceleration of industrialization and urbanization. Urban green space plays an important role in improving the quality of urban environment. Statistical reports from 2002 to 2013 were analysed to estimate the environmental purification value of urban green space in Nanjing by using the production cost method and substituted expenses method. Results showed that the environmental purification value of urban green space from 2002 to 2013 increased from 0.212 billion to 0.354 billion RMB, showing an increase of 0.142 billion RMB and an annual average growth rate of 14% in the past 12 years. Carbon fixation and oxygen release of urban green space ecosystems are transferable in regional space | hence, these services can be performed by the natural ecosystems beyond the city. However, harmful gas absorption, dust detention and noise reduction of urban green space is not transferable in space and thus must be performed by the urban ecosystem. Therefore, aside from innovating technologies for pollution-reducing and pollution-controlling, increasing green space coverage, optimizing green plant distribution structure, and enhancing urban green space management must be executed to improve the urban ecological environment.

Seasonal variations of chloroplast thylakoids and plasma membrane ultrastructure and changes in some biochemical parameters (e.g., metal accumulation, photosynthetic pigments, carbohydrates, lipid peroxidation, and electrolyte leakage) were studied in fronds of Salvinia minima plants exposed to increasing concentrations of Cr(VI) in both winter and summer. Disorganization of stacked (grana) and unstacked (stroma lamellae) thylakoids was greater in winter chloroplasts than in summer chloroplasts. Plasma membrane was less affected than thylakoids. Photosynthetic pigments, lipid peroxidation, soluble sugars, and starch were affected differently in winter and summer. Our results suggest that much greater ultrastructural alterations and changes in metabolite levels occurring in winter fronds are produced by higher oxidative stress resulting from the interactive effect between low temperature, low solar irradiance, and Cr(VI) toxicity, rather than from metal accumulation per se. Seasonal differences occurring in chloroplast ultrastructure and metabolite concentrations were discussed in relation to metabolic implications. Evaluated parameters represent a relevant approach to enhance knowledge on performance and fitness of plants exposed to heavy metals under fluctuating environmental conditions. This work also indicates that selection of suitable macrophytes to remove Cr(VI) requires an additional analyzing focus on structural and metabolic interactions that occur in plants exposed to heavy metals in contrasting seasons.

The sorption behavior of cobalt by a sodium-modified zeolite-rich tuff was investigated using cobalt solutions prepared with water from the cooling system of a nuclear reactor. The sorption kinetics shows that the equilibrium was reached in less than 20 h. The isotherms showed that the sorption capacity of the sodium-modified zeolite-rich tuff for cobalt was 20.73 mg/g at 60 °C. The pH affects the sorption capacity of the sodium-modified zeolite-rich tuff for cobalt. The sorption capacity of the sodium-modified zeolite-rich tuff for cobalt was higher using nuclear purity water than water from other aqueous matrices.

Here, we report on the ability of two different water treatment residues, a Fe-based (Fe-WTR) and an Al-based (Al-WTR) ones, to accumulate Cd(II) and Zn(II) from aqueous solutions at different pH values (pH 4.5, 5.5, and 7.0). Fe-WTR showed a greater Zn(II) and Cd(II) sorption capacity than Al-WTR at all the pH values investigated, in particular at pH 7.0 (e.g., ∼0.200 and ∼0.100 mmol g⁻¹ of Me(II) sorbed by Fe- and Al-WTR at pH 7.0, respectively). The greater capacity of the Fe-WTR to accumulate Me(II) seems to be linked to its higher content of iron and manganese ions and to its higher CEC value compared to Al-WTR. The role of the inorganic and organic fractions of WTRs in metal sorption was also assessed. A higher affinity of Cd(II) with respect to Zn(II) toward functional groups of the organic matter of both WTRs was observed, while Zn(II) showed a stronger association with the inorganic phases. The sorption of both metal ions appeared mainly governed by the formation of inner-sphere surface complexes with the inorganic and organic phases of WTRs, as suggested by the sequential extraction data.

Biosolids are a source of recycled organic matter and nutrients. To evaluate the impact of biosolids application (1984–2008) on soil quality, composite soils (Genesee silt loam, fine loamy, mixed, nonacid, and mesic typic udifluvent) were randomly sampled at geo-referenced sites from 0 (control), 2, 5, and 25 years of lime-stabilized anaerobically digested biosolid-applied fields. Results showed that microbial biomass C (Cₘᵢc), N (Nₘᵢc), and P (Pₘᵢc) contents were significantly higher at both depths of the 5 and 25 years of biosolid-applied fields compared to the control. Biosolid application significantly enlarged the biologically labile C (Cₘᵢc over total organic C, Cₘᵢc:Cₒᵣg) and N (Nₘᵢc over total N, Nₘᵢc:TN) pools with an associated decrease in metabolic C loss (20–53 %) by specific maintenance respiration (qCO₂) relative to the control. The Cₒᵣg, active (AC) and soluble C (SC), TN and reactive N (RN), and reactive P (RP) contents were significantly higher in the long-term biosolid-applied fields than in the control. However, there was an indication of leaching of SC, RN, and RP between depths. Years of biosolid application significantly increased soil moisture content (θ ᵥ at −0.03 MPa) by 20–40 %, macroaggregate stability (MaA) by 2–44 %, and mean weight diameter (MWD) of aggregates by 7–51 %, respectively. Consequently, there was a decrease in soil bulk density (ρ b) and microaggregate stability (MiA) at both depths. Results confirmed that biosolids application at rates recommended is a viable management option to improve soil quality for crop production. However, long-term and repeated biosolid applications above the recommended agronomic N and P rates may be responsible for accumulation and consequent leaching and runoff of SC, RN, and RP to cause groundwater and surface water pollution with environmental consequences.

Deterioration of natural water resources due to runoff from agricultural land is a major problem in the US Great Plains. Changes in earth climate can create heavy storms and alter precipitation patterns which would affect the element concentrations in runoff. A 2-year study (dry and wet years) was conducted to assess the impact of annual precipitation on element concentrations in runoff from soils and element loadings to Salt Creek in the Roca watershed, NE. Both dissolved and sediment-associated forms of five elements (Al, Fe, Mn, Cu, and Zn) were determined in runoff. The amount of dissolved element in runoff during the wet year was greater than the dry year. Except for Zn, the total amount of element associated with sediment was greater than that found in dissolved form. The Mehlich3 extraction was applied to determine the reactive fraction of element in sediment. A small fraction of element associated with sediment was in reactive form, ranging from 1 to 33 % of the total element content. The sum of both the reactive fraction of element in sediment and amount of element dissolved in water were used to calculate the total bioactive element concentration (BEC) in runoff. During the dry year, the total BEC in runoff was 424, 349, 387, 5.2, and 26.8 μg/L for Al, Fe, Mn, Cu, and Zn, respectively. The corresponding total BEC during the wet year was 622, 479, 114, 3.7, and 19.8 μg/L for Al, Fe, Mn, Cu, and Zn, respectively. Further, the bioactive element loading (BEL) into Salt Creek was greater during the wet year than the dry year. Aluminum, Fe, and Mn contributed to the greatest BEL into the surface water body while Zn and Cu had the least contribution. We concluded that greater precipitation during the wet year would increase the negative impact of runoff from soils and BEL to surface water systems in the US Great Plains.

The reaction of Hg²⁺with sulfite is a major identified reduction pathway in the atmosphere. UV absorption spectroscopy was used to study the kinetics of Hg²⁺reduction by sulfite (Na₂SO₃) in the presence of fly ash. Upon the addition of Cumberland and Shawnee fly ash samples, the reduction rates were 0.0071 ± 0.0008 and 0.0009 ± 0.0006 s⁻¹, respectively. This represents c.a. 40 and 90 % decreases in the homogeneous rate, 0.013 ± 0.007 s⁻¹. The reduction reaction was also observed when Cumberland was added without Na₂SO₃. Sulfur elemental analyzer and high-resolution field emission scanning microscopy with energy dispersive X-ray spectroscopy (HR-FE-SEM-EDS) characterization confirmed that Cumberland fly ash particles were rich in sulfur. Nanoparticle Tracking Analysis (NTA) determined the mean particle size in solution to be 246 ± 25 nm for Cumberland fly ash and 198 ± 14 nm for Shawnee. To obtain further insight on observed Hg²⁺homogeneous reduction rates by sulfite, the effects of several environmental variables were investigated. Hg(NO₃)₂and HgO were used as the sources of Hg²⁺. Extended pH (1–7) and temperature (1.0–45.0 °C) ranges were studied for the first time. The enthalpies of activation for the HgO reduction were 94 ± 3 kJ mol⁻¹at pH 1 and 92 ± 4 kJ mol⁻¹at pH 3, while the entropies were 33 ± 9 J mol⁻¹ K⁻¹at pH 1 and 30 ± 10 J mol⁻¹ K⁻¹at pH 3. It was determined that increasing ionic strength, especially with nitrate species, slows down the reaction at pH = 7. Significance of the results on the variability of mercury reduction by sulfite at various environmental conditions, and its implication in modelling are discussed.

A high concentration of dissolved gaseous mercury (DGM) was detected in post-desulfurized waste seawater, which was discharged from a coal-fired power plant equipped with a seawater desulfurization system and which was located in a coastal area. A large amount of DGM was converted from other forms of mercury during transformation processes, such as photo-reduction. The present study targeted the photo-reduction of mercury and the effects of various environmental parameters on DGM production in the post-desulfurized seawater discharged. The results suggested that the photo-reduction of mercury was significantly induced under UV radiation, especially with UVB. The particulate mercury on suspended solids was easily photo-reduced and considered as an important source of DGM. It was confirmed that the suspended solids in post-desulfurized seawater could enhance the reduction process of mercury under UV radiation. The pseudo-first-order rate constants of DGM production, which were determined through the concentration gradient and trial methods, were 1.39 × 10⁻³ min⁻¹and 1.45 × 10⁻³ min⁻¹, respectively. The values showed no significant difference and were both much higher than the reported results, indicating that the photo-reduction of mercury in post-desulfurized seawater deserved more attention. In addition, the initial mercury level was observed when mixing the post-desulfurized seawater with fresh seawater, and this suggested that a significant amount of initial mercury would be produced when the post-desulfurized seawater was discharged into the adjacent sea area and thus becomes another considerable source of DGM.