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Wood ash recycling to forests is beneficial because it regains nutrients and prevents acidification, but wood ash application is restricted due to its cadmium (Cd) content. We question if Cd in wood ash represents a problem, since decreases in Cd bioavailability due to ash-induced pH changes may counteract increased total Cd concentration. We studied effects of wood ash (0, 3, 9 and 30 t ha-1) and lime (pH increase equivalent to the wood ash treatments) on growth and Cd uptake in Deschampsia flexuosa. After four months, we measured plant biomass and Cd accumulation, and extracted Cd from the soil using three different methods; HNO3 (total), EDTA (chelator-based) and NH4NO3 (salt-based). Wood ash and lime strongly stimulated plant growth. Cd concentration in the plant tissue decreased with wood ash and lime addition, and correlated positively with the NH4NO3 extractable fraction of Cd in the soil. In contrast, HNO3 and EDTA extracted more Cd with increased wood ash application. We conclude that wood ash amendment increases soil pH, total Cd concentration, nutrient levels and stimulates plant growth. However, it does not increase Cd accumulation in D. flexuosa, as pH-driven decreases in Cd bioavailability leads to reduced plant Cd uptake. Finally, soil bioavailable Cd is best determined using NH4NO3-extraction.

As the largest renewable electricity source, hydropower represents an alternative to fossil fuels to achieve a low-carbon future. However, increasing evidence suggests that hydropower reservoirs are an important source of biogenic greenhouse gases (GHGs), albeit with large uncertainties. Combining spatially resolved assessments of GHG fluxes and hydroelectric capacity databases, we assessed that global GHG emissions from reservoirs is 0.38 Pg CO2 eq.yr−1, accounting for 1.0% of global anthropogenic emissions. The median carbon intensity for hydropower is ∼63.0 kg CO2eq. MWh−1, which is lower than that for fossil fuels, but higher than that for other renewable energy sources. High carbon intensity is mostly linked to shallow (water storage depth <20 m) and eutrophic reservoirs. Furthermore, we found that the reservoir carbon intensity (CI) value would be markedly increased to 131.5 kg CO2eq. MWh−1 when considering the dams under construction and planning. A low-carbon future will benefit from optimal dam planning and management measures, i.e., applying sludge removal treatments, thereby reducing the proportion of shallow reservoirs and anthropogenic pollution.

The problem of wastewater has long been ubiquitous and has great consequences for the environment and its inhabitants. Microbial fuel cells (MFCs) have enormous potential for the treatment of wastewaters polluted with azo dyes. The amount of energy that can be produced from a single-chamber MFC is sufficient to perform decolorization and degradation of such dyes, which are widely used in the textile industry. This study on the azo dye, reactive black 5 (RB5), provides an alternative method through three parallel-connected MFCs to obtain electricity that directly serves for the dye's electrochemical degradation. We examined degradation followed by decolorization of RB5 using Fe and Pt electrodes, together with H2O2, to achieve the electro-Fenton process. The amount of voltage produced (295 mV), the current density (276 mA m-3) and the power density (50 mW m-3) were sufficient to degrade 25 mg L-1 RB5 dye with 0.5 mM H2O2 in just 2 h. The dye degradation mechanism was investigated using UV-VIS, FT-IR and HPLC-MS/MS. The ecotoxicity of the degradation products was assessed using a bacterial model, Aliivibrio fischeri. These tests showed that there was successful degradation of the dye to products whose toxicity is less than that of RB5.

AbstractMowing, as a common grassland utilization strategy, affects nutrient status in soil by plant biomass removal. Phosphorus (P) cycle plays an important role in determining grassland productivity. However, few studies have addressed the impacts of mowing on P cycling in grassland ecosystems. Here, we investigated the effects of various mowing regimes on soil P fractions and P accumulation in plants and litters. We specifically explored the mechanisms by which mowing regulates ecosystem P cycling by linking aboveground community with soil properties. Our results showed that mowing increased soil dissolvable P concentrations, which probably met the demand for P absorption and utilization by plants, thus contributing to an increased P accumulation by plants. Mowing promoted grassland P cycling by a reciprocal relationship between plants and microbes. Short‐term mowing enhanced P cycling mainly through increased root exudation‐evoked the extracellular enzyme activity of microbes rather than the alternations in microbial biomass and community composition. Long‐term mowing increased P cycling mainly by promoting carbon allocation to roots, thereby leading to greater microbial metabolic activity. Although mowing‐stimulation of organic P mineralization lasted for 15 consecutive years, mowing did not result in soil P depletion. These results demonstrate that P removal by mowing will not necessarily lead to soil P limitation. Our findings would advance the knowledge on soil P dynamic under mowing and contribute to resource‐efficient grassland management.

Understanding the spatial variability of CO2 emissions among and within cities and its driving factors is a prerequisite for emission reductions. Using 10 × 10 km national grid emission data (circa 2007), we quantified the spatial distribution of total CO2 emissions and emission efficiency of Chinese cities at the prefectural city scale. The emission efficiency was measured according to the emission intensity, CO2 emissions per capita, residential CO2 emissions per capita and industrial CO2 emissions per unit area. We found substantial variability in the total CO2 emissions among cities ranging from <0.1 to 214.3 million tons. High total CO2 emissions were mostly concentrated in northern, eastern and northeastern China. An overall analysis of the total CO2 emissions and emission intensity revealed that 75% of the cities in northern China had higher total emissions and lower efficiencies than the national average, and these cities shall be the main targeted cities for CO2 emissions reduction and emission intensity improvement. Additionally, urban districts had higher total CO2 emissions and emissions per capita than their surrounding regions for the majority of the prefectural cities. Four indicators, including the industrial structure, gross domestic product (GDP), total population, and size of the built-up area, were significantly related to the CO2 emissions and emission efficiency. Industrial structure was the most important driving force. Our results underscore the need to design region- and/or city-specific reduction strategies instead of a one-size-fits-all policy, and provide strategic information to public and private decision makers on controlling total emissions and improving emission efficiency.

Aim of this study is to quantify the impacts of climate change on phenology and yield of winter wheat in rainfed and irrigated regions of Pakistan by using integration of two well-known crop models including STICS and APSIM with CORDEX-SA regional climate models (RCMs). A number of different adaptation strategies based on early sowing (i.e. S1:10 and S2:20 days), irrigation (I1:15% and I2:30% additional water) and a combination of sowing and irrigation adaptations were examined to recover the potential losses that would occur due to climate change. The data for the wheat phenology, biomass (t/ha) at different stages and yield (t/ha) was obtained from several experiments at national research institutes in Pakistan under both rainfed and irrigated conditions. After calibration and validation of both crop models (STICS and APSIM), the current climate data were replaced with the CORDEX-SA RCM-projections for climate change impact analysis. A significant rising and declining trends were observed in temperature and precipitation patterns, respectively, for the selected study regions. Consequently, a substantial impact of climate change on wheat phenology (anthesis stage, maturity stage, growing length), biomass (t/ha) and yield (t/ha) was observed under scenario periods for RCP4.5 and RCP8.5. Additionally, the adaptation strategies on wheat for rainfed regions showed a substantial improvement in wheat biomass and yield simulated by STICS model particularly for sowing-2 under RCP4.5. Irrigated regions showed more improvement for irrigation-2 (I2) and combination of sowing-1 + irrigation-2 (S1 + I2) using the STICS model under both RCPs. Overall, it was observed that changes in crop phenology had a stronger impact in terms of crop yield for RCP8.5 as compare to RCP4.5. This study provides a valuable understanding and way forward for the better wheat management under changes in precipitation and temperature patterns. The study also discuss in detail, the adaptation strategies to cope with potential damage, over two different irrigation zones (rainfed and irrigated) in Pakistan.

Low cost zeolites with incorporated silver show high activity for both oxygen reduction and borohydride oxidation reaction.

Abstract The yield of cotton (Gossypium hirsutum L.) can be effectively maximized through high planting density. Estimating the yields from single-leaf photosynthesis under various plant densities is difficult as the source-sink relationship of cotton is complicated. By considering the boll-leaf system (BLS: including the main-stem leaf, sympodial leaf and non-leaf organs) as the basic unit of the cotton canopy, the present study asserts that the photosynthetic function of BLS determines single boll weight. This hypothesis was tested by establishing plant densities to explore changes in photosynthesis of the cotton BLS and the consequent effects on boll weight. The results showed that high plant density increased total boll number per unit ground area, whereas single boll weight remained relatively stable, thereby increasing cotton yield. High plant density significantly limited the biomass of the BLS and reduced the distribution ratio of assimilate to sympodial leaves, whereas the dry matter proportion of cotton bolls increased. Although the leaf area and photosynthetic rate of both the main-stem and sympodial leaves of the BLS decreased with increasing plant density, the extent of decrease in the latter was greater. CO2 assimilation within the BLS decreased slightly with increasing plant density, and significant decreases in CO2 assimilation were only evident in extremely high plant densities. A significant positive linear correlation was observed between CO2 assimilation of the BLS and single boll weight. Therefore, photosynthesis of the BLS was identified as the primary factor maintaining boll weight under various plant densities. The main-stem leaf plays a key role in maintaining photosynthesis of the BLS, whereas BLS photosynthesis can be improved by plastically regulating the photosynthetic performance in sympodial leaves.