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Forest soil acidification caused by acid deposition is a serious threat to the forest ecosystem. To investigate the liming effects of biomass ash (BA) and alkaline slag (AS) on the acidic topsoil and subsoil, a three-year field experiment under artificial Masson pine was conducted at Langxi, Anhui province in Southern China. The surface application of BA and AS significantly increased the soil pH, and thus decreased exchangeable acidity and active Al in the topsoil. Soil exchangeable Ca2+ and Mg2+ in topsoil were significantly increased by the surface application of BA and AS, while an increase in soil exchangeable K+ was only observed in BA treatments. The soil acidity and active Al in subsoil were decreased by the surface application of AS. Compared with the control, soluble monomeric and exchangeable Al in the subsoil was decreased by 38.0% and 29.4% after 3 years of AS surface application. There was a minimal effect on soluble monomeric and exchangeable Al after the application of BA. The soil exchangeable Ca2+ and Mg2+ in the subsoil increased respectively by 54% and 141% after surface application of 10 t ha-1 AS. The decrease of soil active Al and increase of base cations in subsoil were mainly attributed to the high migration capacity of base cations in AS. In conclusion, the effect of surface application of AS was superior to BA in ameliorating soil acidity and alleviating soil Al toxicity in the subsoil of this Ultisol.

This study focused on the effects of plant compositions on removal rates of pollutants in microcosms through investigating rhizosphere microbial populations, photosynthetic efficiency and growth characteristics. Mixed-culture groups improved the removal efficiency of TN and TP significantly but exhibited lower COD removal rates. Total plant biomasses were improved as the species richness increased, but the N/P content in the plants was mainly affected by the type of species. The mixed-culture groups showed lower photosynthesis rates and oxygen supply generated from roots under high irradiation. Microbial communities of the cultured groups in the rhizosphere exhibited significant differences. According to principal component analysis (PCA), the fungi were the typical microbes of SPA, SPAB, and SPABC, resulted in improvement in nutrient accumulation. These results demonstrated that a mixed culture strategy can represent the overyielding of biomass, promote the photo-protection mechanism, and will further increase the removal rates of pollutants in a constructed wetland.

Abstract CBM reservoirs are extremely vulnerable to damage due to their complex pore structure. So, changing pore structures in CBM reservoirs is of vital importance for reducing reservoirs damage. Organic solvents have been considered as additives into fracturing fluids to enhance production because they can enhance the pore connectivity and loosening macromolecular network structure. It is thus of great interests to investigate how organic solvents (ethanol and ethylene glycol ether) change micropore structures and fluid distribution. In this study, samples were selected from different wells completed in No. 3 coal seam, Zhaozhuang minefield. Low-pressure nitrogen adsorption (LP-N2GA) experiments were conducted on coal samples to evaluate the changes in pore-structure parameters including specific surface area (SSA), pore diameter, and pore volume. NMR experiments were conducted on coal samples to evaluate the changes in fluid distribution. Analyzing the LP-N2GA results suggests ethylene glycol ether and ethanol can effectively increase SSA, pore diameter, and opening degree of pores in coal samples. Comparative analysis of NMR results indicates that ethylene glycol ether consistently reduces the irreducible water saturation (Swir) in samples. The average value of Swir of raw samples is 0.8670 and the average value of Swir of samples treated with ethylene glycol ether value is 0.7644. Considering the pore-structure alterations, this study demonstrates that ethylene glycol ether is more preferable for enhancing recovery from CBM reservoirs compared with ethanol.

Comparison of the water budget for the typical cropland and pear orchard ecosystems in the North China Plain Comparison of the water budget for the typical cropland and pear orchard ecosystems in the North China Plain

Virtual water flows have a profound impact on the natural water system of a country or region, and they may help conserve local water resources or exacerbate water scarcity in some areas. However, current research has only focused on the measurement of virtual water flows, without analysis of the causes of virtual water flow patterns. This study first obtained virtual water flow patterns across provinces by constructing a multi-regional input–-output (MRIO) model of the Yellow River basin in 2012 and 2017, and then analyzed its driving factors by applying the extended STIRPAT model to provide directions for using virtual water trade to alleviate water shortages in water-scarce areas of the basin. We found the following: (1) The Yellow River basin as a whole had a net virtual water inflow in 2012 and 2017, and the net inflow has increased from 2.14 billion m3 to 33.67 billion m3. (2) Different provinces or regions assume different roles in the virtual water trade within the basin. (3) There is an obvious regional heterogeneity in the virtual water flows in different subsectors. (4) Per capita GDP, tertiary industry contribution rate, consumer price index, and water scarcity are the main positive drivers of virtual water inflow in the Yellow River Basin provinces, while primary industry contribution rate, per capita water resources, and water use per unit arable area promote virtual water outflow. The results of this paper present useful information for understanding the driving factors of virtual water flow, which could promote the optimal allocation of water resources in the Yellow River basin and achieve ecological protection and high-quality development in this area.

As a porous medium with rich pore structure, activated carbon (AC) was once considered the best carrier for hydrate storage and transportation. However, the harsh conditions of the hydrate reaction in the wet carbon environment have always limited the sufficient and rapid formation of hydrate. Therefore, the influences of particle size (4–8, 8–16, 20–40 and 100 mesh) and liquid phase saturation (fully/partially saturated) in the sodium dodecyl sulfate system on hydrate reaction were investigated. The results showed that small particle in the fully saturated liquid phase system led to the increase in hydrate generation rate, with the highest hydrate reaction rate of 3.16 mmol/min in the 100 mesh AC layer, which was 1.7–2.9 times higher than other AC layers. The gas storage capability of the 4–8 mesh AC layer with a water saturation of 70% was the highest among all systems, reaching 0.198 mol/mol. The saturation of the liquid phase induced the nucleation and growth of hydrates. Adherently growing hydrates of fully saturated liquid phase systems and mushroom-like hydrates of partially saturated liquid phase systems were found in turn. This research facilitates the commercialization of AC-based hydrate technology.

Nitrogen reduction reaction (NRR) and nitrate reduction reaction (NO3−RR) provide a potential sustainable route by which to produce ammonia, a next-generation energy carrier. Many studies have been conducted over the years, mainly emphasizing material design and strategies to improve catalytic performance. Despite significant achievements in material design and corresponding fundamental knowledge, the produced ammonia is still very limited, which makes it prone to bias. The presence of interferants (e.g., cations and sacrificial reagents), the pH of the solution, and improper analytical procedure can lead to the over or underestimation of ammonia quantification. Therefore, the selection of the appropriate ammonia quantification method, which meets the sample solution condition, along with the proper analytical procedures, is of great importance. In this review, the state-of-the-art ammonia quantification method is summarized, emphasizing the advantages, limitations, and practicality for NRR and NO3−RR studies. Fundamental knowledge of the quantification method is introduced. Perspective on the considerations for selecting the suitable quantification method and for performing the quantification process is also provided. Although non exhaustive, this focused review can be useful as a guide to design the experimental setup and procedure for more reliable ammonia quantification results.

Spatio-temporal variations in extreme drought in China during 1961–2015 Spatio-temporal variations in extreme drought in China during 1961–2015

Positive forced aeration is widely used in industrial composting plants to supply sufficient oxygen, accelerating compost maturity. However, this technology results in significant gaseous emission, especially NH3 and GHGs emissions. To reduce gaseous emissions and investigate aeration efficiency, negative pressure aeration was used during cattle manure þ corn stalk composting in 50 L-scale reactors. Composting with negative pressure aeration at three different flow rates (0.25, 0.50 and 0.75 L/min/kg dry weight, named Negative-L, Negative-M and Negative-H treatments) were conducted. Treatment with positive pressure aeration was set as a control (Positive-M, with flow rate at 0.50 L/min/kg dry weight). The results showed that negative pressure aeration changed the temporal distribution of oxygen and temperature. With the same flow rate, the Negative-M treatment maintained a longer thermophilic period, accelerating organic matter degradation (47.6% in treatment Negative-M and 41.4% in Positive-M) and the maturity of feedstock (germination index was 105.9% in Negative-M and 58.5% in Positive-M). Ammonia emissions were significantly reduced by composting with negative pressure aeration. During composting, 36.7%, 15.8%, 16.8% and 16.0% of the initial total nitrogen was lost via NH3 volatilizations in the Positive-M, Negative-L, Negative-M and Negative-H treatments, respectively, indicating NH3 emissions were reduced by ~55% compared to the positive pressure aeration treatment. Even though both CH4 and N2O emission were greater from the negative pressure aeration treatments, the global warming potential was significantly reduced in treatments with negative pressure aeration because of the lower NH3 emission (an indirect N2O source). This indicates the benefit of NH3 emission mitigation was larger than the increase in CH4 and N2O emissions. Positive forced aeration is widely used in industrial composting plants to supply sufficient oxygen, accelerating compost maturity. However, this technology results in significant gaseous emission, especially NH3 and GHGs emissions. To reduce gaseous emissions and investigate aeration efficiency, negative pressure aeration was used during cattle manure þ corn stalk composting in 50 L-scale reactors. Composting with negative pressure aeration at three different flow rates (0.25, 0.50 and 0.75 L/min/kg dry weight, named Negative-L, Negative-M and Negative-H treatments) were conducted. Treatment with positive pressure aeration was set as a control (Positive-M, with flow rate at 0.50 L/min/kg dry weight). The results showed that negative pressure aeration changed the temporal distribution of oxygen and temperature. With the same flow rate, the Negative-M treatment maintained a longer thermophilic period, accelerating organic matter degradation (47.6% in treatment Negative-M and 41.4% in Positive-M) and the maturity of feedstock (germination index was 105.9% in Negative-M and 58.5% in Positive-M). Ammonia emissions were significantly reduced by composting with negative pressure aeration. During composting, 36.7%, 15.8%, 16.8% and 16.0% of the initial total nitrogen was lost via NH3 volatilizations in the Positive-M, Negative-L, Negative-M and Negative-H treatments, respectively, indicating NH3 emissions were reduced by ~55% compared to the positive pressure aeration treatment. Even though both CH4 and N2O emission were greater from the negative pressure aeration treatments, the global warming potential was significantly reduced in treatments with negative pressure aeration because of the lower NH3 emission (an indirect N2O source). This indicates the benefit of NH3 emission mitigation was larger than the increase in CH4 and N2O emissions.