查看更多>>摘要：Microbially-mediated mobilization of soil arsenic (As) is greatly influenced by the soil properties. However, in soils with contrasting iron (Fe), sulfur (S), and organic matter (OM) contents, the biogeochemical pathways controlling As transformation and distribution remain unclear. Using sequential soil As extraction and X-ray absorption spectroscopy (XAS), we investigated the causal mechanisms of As reduction and redistribution in five soils during microbial incubation. Incubation of arsenate (As(V))-reducing bacteria resulted in a significant arsenite (As(III)) release (21.6-61.9% of total soil As (As-total)). Thereafter, the re-immobilization of released As (III) was controlled by contrasting biogeochemical pathways, which were mainly dominated by soil Fe and S. For soil with high Fe content (191.1 g/kg), As immobilization is attributed to As(III)-readsorption by (neoformed) Fe(oxyhydr)oxides, despite the presence of abundant S (10.3 g/kg); while in soils with relatively low Fe content (25.9-35.6 g/kg) and high S content (1.4-1.7 g/kg), As-sequestration depends largely on As-sulfide formation (5-47% of solid-phase As), including realgar and orpiment-like phases. In contrast, released As remains in solution in soils with relatively low Fe (27.5-52.4 g/kg) and S contents (0.6-1.0 g/kg). Arsenic-XAS results show that all soil As fractions, including residual As(V), can potentially be reduced (34-92% of As-total), and solid-phase As(V) reduction was enhanced at higher OM content. Collectively, these results elucidate the dominant biogeochemical pathways controlling As fate in soils with different Fe, S, and OM contents.
查看更多>>摘要：Soil salination challenges sustainable agricultural production and management in the lowland area of the North China Plain (NCP). This study investigated the effect of varied rainfall events and hydrological years on deep drainage and salt leaching in Nanpi County in the NCP. Field experiments were conducted to measure soil matric potential (SMP) and soil water electrical conductivity (ECw) in 300 cm profiles of an irrigated cropland (CL) and unirrigated grassland (GL). The HYDRUS-1D model was calibrated and validated to optimize soil water and salt transport parameters using the SMP and ECw data obtained in 2015 and 2016, respectively. The results showed that the HYDRUS-1D model was reliable to simulate soil water and salt migration in 300 cm profiles at both sites. The salt leaching depths and degrees were positively correlated with precipitation amount. The heavy rain (45 mm) and rainstorm (68 mm) favored salt leaching within 100 cm, and severe and extreme rainstorms resulted in salt leaching within 150-200 cm both in the CL and GL. The SDP in the CL was greater than that in the GL in all hydrological years owing to agricultural cultivation and irrigation. Salt leaching in the 300 cm profiles mainly occurred in the rainy seasons of wet year, with the salt decrease percentage (SDP) being 61% in the CL and 42% in the GL. Salt leaching due to precipitation was sufficient in the irrigated CL in all hydrological years, and precipitation in normal rainfall years could remove 70-80% of soil salts within 50-63 cm soil depth. Grass growth without irrigation led to water deficits and salt accumulation when the annual precipitation amount was less than that in wet years. The results demonstrated that precipitation, combined with irrigation using of brackish and freshwater, could be usefully for soil salt leaching. A recommended irrigation scheme for water saving and salt control in CL and GL is one brackish water irrigation application and three freshwater irrigation applications each year in the NCP.
查看更多>>摘要：Coastal wetlands, located at the intersection of land and sea, are considered to be a phosphorus (P) sink, source, and reactor in the global P cycle. However, the variation in P sorption capacity with wetland age and the related sorption mechanisms are not well understood. In this study, we collected the surface soil samples (0-20 cm) from 10 coastal freshwater wetlands that had been restored for 0-44 years surrounding China's Bohai Rim. Through a series of batch experiments, we studied the factors controlling P sorption and release in these soils. The results showed that the maximum P sorption capacity (Qmax) in these wetlands was 294-2447 mg kg(-1), with an average of 1472 mg kg(-1). The Qmax generally increased with increasing wetland restoration age. The degree of P saturation (DPS) and the P eutrophication risk index (ERI) for coastal wetlands were 0.5-9.5% and 0.9-21.1%, respectively. The DPS and ERI values did not vary significantly with wetland age. These data suggest that freshwater restoration significantly increases P sorption capacity, while not greatly affecting the P release potential in the coastal wetlands surrounding Bohai Rim. These observations may be related to the soil desalination and organic matter and amorphous Fe and/or Al accumulation that occur during the freshwater restoration of degraded wetlands. Coastal wetlands (especially restored wetlands) were suggested as P storage hotspots among upland, wetland, and offshore along the coastal watersheds of Bohai. These findings indicate that the freshwater restoration significantly improved the soil properties in the degraded coastal wetlands, and therefore increased P sorption capacity in the restored wetlands.
查看更多>>摘要：Information on water table depth (WTD) in polder areas and wetlands is important in, for example, estimating emissions of greenhouse gases, assessing the agricultural and ecological potential, and flood risk management. The seasonal variation of WTDs is summarized with averages of the yearly highest (shallowest) and lowest (deepest) water tables (MHW and MLW). These characteristics show short-distance variations within the fields in polder areas, which cannot be mapped using geostatistical interpolation techniques or physical modelling against reasonable costs or with acceptable accuracy. The within-field variations depend on soil type and water management. MHW and MLW were determined from auger hole measurements of WTDs at locations being selected following stratified simple random sampling in subareas classified by soil type and water management. Within these subareas, a further classification was made on the basis of distance to ditches. For each subarea spatial distribution functions of MHW and MLW were made, taking censored observations into account. Uncertainty was quantified by 10,000 bootstrap realisations of the spatial distribution functions. From these realisations maps depicting summary statistics for the spatial distribution of WTD-characteristics within the subareas were derived, as well as a map with probabilities of exceedance of a critical level that can serve as input for risk analysis.
Muller-Stover, DoretteHansen, VeronikaJensen, Lars StoumannMagid, Jakob...
10页
查看更多>>摘要：Many organically managed farms in Europe have low levels of soil phosphorus (P). Arable farms that rely strongly on biological nitrogen fixation (BNF) have been shown to have rather low outputs and a tendency to deplete soil P and potassium (K) compared with arable farms that have a lower reliance on BNF and higher external inputs. Therefore, research focusing on providing a balanced input of nitrogen (N), P, K and sulphur (S) from alternative sources is of interest to organically managed farms in Europe. The aim of this study was to quantify P availability from different organic wastes applied alone or in combination to improve the mixtures' N:P:K:S ratio. P availability was measured by P uptake and recovery in ryegrass grown in pots. The isotope dilution approach was used in which a non-labelled fertiliser is added to a soil that has been pre-incubated and equilibrated with labelled P-33. The P recovery of the different organic wastes varied significantly (10-20 %). Manure and anaerobically digested manure mixed with ash from straw had the lowest P recovery. All the organic waste treatments had higher plant growth and P uptake compared with the negative control, but none of them reached the values observed after application of mineral P. Mixing digested manure with ash increased soil pH at the end of the experiment, which may explain the lower P availability. The highest P recovery was found in digested products, either manure alone or mixed with municipal waste or the industrial waste product Fertigro (R). However, the mixture of digested manure and Fertigro (R) led to lower dry matter production, whereas Fertigro (R) used alone resulted in high leaf P concentrations but depressed shoot and root growth, presumably due to salinity effects and a decrease in soil pH. Anaerobic digestion increased the availability of P, which may be explained by the lower immobilisation potential of the remaining organic matter in the digestate. This study highlights the potential challenges when attempting to improve the N:P:K:S ratios of waste-based fertilisers through mixing due to material interactions. However, such effects are likely to be overexpressed in pot trials that have a limited soil volume. Field trials are therefore needed to quantify such effects in practice.
查看更多>>摘要：Aeolian dust emission is a major contributing factor to soil degradation and environmental pollution and threatens human well-being. Inner Mongolia, as an ecological barrier in northern China, is a hot spot of Aeolian dust emission, which indicates that the ecosystems act very important roles in preventing mineral dust from being emitted. In this study, utilizing a widely used model, we aim to identify the impacts of local ecosystems in preventing dust emissions and the corresponding trajectories in Inner Mongolia during 2001-2018. We found that the 18 years accumulated potential dust emission was approximately 12634.027 Tg, about ten times higher than the accumulated actual dust emission (approximately 1274.925 Tg); this showed the ecosystems of Inner Mongolia had prevented 11359.102 Tg mineral dust from being emitted. So, the prevention rate of the ecosystems was approximately 0.899. By studying the flow trajectories of ecosystems dust emission prevention (EDEP), we found that the EDEP worked most frequently in Spring and in the central regions of Inner Mongolia. The effects of EDEP mainly flowed to the areas located on the southeast of Inner Mongolia, like Shanxi, Hebei, Liaoning, Jilin, and Heilongjiang Province. We further identified the distributions of the EDEP benefiting areas and the corresponding beneficiary frequency. We found that the EDEP benefiting areas were distributed in most parts of China, and the regions closer to Inner Mongolia had the higher beneficiary frequency, especially the ones located in the eastern areas. This study provides some valuable theoretical foundations for the economic analysis of restoration projects.
NSTL
Elsevier