•Phosphorus input into croplands is expected to increase 51–86% by the year 2050.•In developed and transition regions, legacy phosphorus attenuates the increasing need for fertilizer.•Developing ...regions will likely continue to increase fertilizer use to meet the growing agricultural demand.
A spatially explicit, two-pool soil phosphorus (P) model was used to analyze cropland P dynamics and fertilizer demand based on future crop production as projected in the shared socioeconomic pathways (SSPs). The model was initialized with historical data on P inputs and uptake, which governed the soil P accumulation up to present day. In contrast to existing scenario studies, the model accounts for both soil characteristics relevant to P retention and changing land use. At the global scale, crop uptake and the fraction of the applied P fertilizer that is directly taken up by plant roots govern the P quantities present in the soil. Despite the differences in the storylines among the SSPs, the quantitative implementation results in estimates for crop production and P inputs that are quite similar, which contrasts with the stark divergence in terms of population and incomes. In addition to global fertilizer P inputs in croplands increasing from 14.5 Tg P yr−1 in 2005 to 22–27 Tg P yr−1 in 2050, this study also estimates that 4–12 Tg P yr−1 would be needed in 2050 in global intensively managed grasslands to maintain fertility. Our new model approach can pinpoint the contribution of area expansion and crop yield improvement toward the total production, whereby the latter is shown to contribute 100% to 69%, depending on the scenario.
An integrated modeling approach was used to connect socioeconomic factors and nutrient management to river export of nitrogen, phosphorus, silica and carbon based on an updated Global NEWS model. ...Past trends (1970–2000) and four future scenarios were analyzed. Differences among the scenarios for nutrient management in agriculture were a key factor affecting the magnitude and direction of change of future DIN river export. In contrast, connectivity and level of sewage treatment and P detergent use were more important for differences in DIP river export. Global particulate nutrient export was calculated to decrease for all scenarios, in part due to increases in dams for hydropower. Small changes in dissolved silica and dissolved organics were calculated for all scenarios at the global scale. Population changes were an important underlying factor for river export of all nutrients in all scenarios. Substantial regional differences were calculated for all nutrient elements and forms. South Asia alone accounted for over half of the global increase in DIN and DIP river export between 1970 and 2000 and in the subsequent 30 years under the Global Orchestration scenario (globally connected with reactive approach to environmental problems); DIN river export decreased in the Adapting Mosaic (globally connected with proactive approach) scenario by 2030, although DIP continued to increase. Risks for coastal eutrophication will likely continue to increase in many world regions for the foreseeable future due to both increases in magnitude and changes in nutrient ratios in river export.
Abstract
Concerns about the neurotoxic potential of polyfluoroalkyl substances (PFAS) such as perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) increase, although their neurotoxic ...mechanisms of action remain debated. Considering the importance of the GABA
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receptor in neuronal function, we investigated acute effects of PFAS on this receptor and on spontaneous neuronal network activity. PFOS (Lowest Observed Effect Concentration (LOEC) 0.1 µM) and PFOA (LOEC 1 µM) inhibited the GABA-evoked current and acted as non-competitive human GABA
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receptor antagonists. Network activity of rat primary cortical cultures increased following exposure to PFOS (LOEC 100 µM). However, exposure of networks of human induced pluripotent stem cell (hiPSC)-derived neurons decreased neuronal activity. The higher sensitivity of the α
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β
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γ
2L
GABA
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receptor for PFAS as compared to neuronal networks suggests that PFAS have additional mechanisms of action, or that compensatory mechanisms are at play. Differences between rodent and hiPSC-derived neuronal networks highlight the importance of proper model composition. LOECs for PFAS on GABA
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receptor and neuronal activity reported here are within or below the range found in blood levels of occupationally exposed humans. For PFOS, LOECs are even within the range found in human serum and plasma of the general population, suggesting a clear neurotoxic risk.
Reactive nitrogen (N) inputs in agriculture strongly outpace the outputs at the global scale due to inefficiencies in cropland N use. While improvement in agricultural practices and environmental ...legislation in developed regions such as Western Europe have led to a remarkable increase in the N use efficiency since 1985, this lower requirement for reactive N inputs via synthetic fertilizers has yet to occur in many developing and transition regions. Here, we explore future N input requirements and N use efficiency in agriculture for the five shared socioeconomic pathways. Results show that under the most optimistic sustainability scenario, the global synthetic fertilizer use in croplands stabilizes and even shrinks (85 Tg N yr−1 in 2050) regardless of the increase in crop production required to feed the larger estimated population. This scenario is highly dependent on projected increases in N use efficiency, particularly in South and East Asia. In our most pessimistic scenario, synthetic fertilization application rates are expected to increase almost threefold by 2050 (260 Tg N yr−1). Excepting the sustainability scenario, all other projected scenarios reveal that the areal N surpluses will exceed acceptable limits in most of the developing regions.
The atomic structure of several nuclear graphite samples, an essential moderator material for nuclear reactors, has been investigated by X-ray diffraction. The patterns were analyzed by the ...conventional Rietveld refinement approach as well as by the CARBONXS model, which takes into account disorder and stacking faults. The refined parameters compiled with those from literature reveal a generic picture for the structure of all graphite specimens.
Highlights • This review summarises the methods used to assess image quality in CT. • CT optimisation is separated into two phases (unit and protocol oriented). • Signal detection theory as well as ...the task-based approach are presented. • The strengths and weaknesses of the different methods presented are addressed. • A summary of CT's figure of merits is provided.
As Chinese aquaculture production accounts for over half of the global aquaculture production and has increased by 50% since 2006, there is growing concern about eutrophication caused by aquaculture ...in China. This paper presents a model-based estimate of nutrient flows in China’s aquaculture system during 2006–2017 using provincial scale data, to spatially distribute nutrient loads with a 0.5° resolution. The results indicate that with the increase in fish and shellfish production from 30 to 47 million tonnes (Mt) during 2006–2017, the nitrogen (N) release increased from 1.0 to 1.6 Mt/year and that of phosphorus (P) from 0.1 to 0.2 Mt/year. Nutrient release from freshwater aquaculture was concentrated in Guangdong, Jiangsu, and Hubei, and that from mariculture in Shandong, Fujian, and Guangdong. Aquaculture is an important strongly concentrated nutrient source in both freshwater and marine environments. Its nutrient release is >20% of total nutrient inputs to freshwater environments in some provinces, and nutrients from mariculture are comparable to river nutrient export to Chinese coastal seas. Aquaculture production and nutrient excretions are now comparable to those of livestock production systems in China and need to be accounted for when analyzing causes of eutrophication and harmful algal blooms and possible mitigation strategies.
This paper presents a global model‐based country‐scale quantification of urban N and P mass flows from humans, animals, and industries and their waste N and P discharges to surface water and urban ...waste recycling in agriculture. Agricultural recycling was practiced commonly in early twentieth century Europe, Asia, and North America. During the twentieth century, global urban discharge to surface water increased ~3.5‐fold to 7.7 Tg yr‐1 for N and ~4.5‐fold to 1.0 Tg yr‐1 for P; the major part of this increase occurred between 1950 and 2000. Between 1900 and ~1940, industrial N and P flows dominated global surface water N and P loadings from urban areas; since ~1940, human wastes are the major source of urban nutrient discharge to both surface water and agricultural recycling. During the period 1900–2000, total global recycling of urban nutrients in agriculture increased from 0.4 to 0.6 Tg N yr‐1 and from 0.07 to 0.08 Tg P yr‐1. A large number of factors (the major ones related to food consumption, urban population, sewer connection, and industrial emissions) contribute to the uncertainty of −18% to +42% for N and −21% to +45% for P around the calculated surface water loading estimate for 2000.
Key Points
A global model was made to inventory urban 20th century nutrient flows
Global surface water discharge increased ~3.5‐fold for N and ~4.5‐fold for P
At present human excreta and detergents are the major urban nutrient sources
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•In 2050 anthropogenic sources will contribute up to 80% to river nutrient loading.•Curbing the global nutrient cycles requires paradigm shifts in food and waste systems.•N:P ratios ...in global rivers will further increase due to selective system retention of P.•Waste systems need to change from a disposal orientation towards conservation.
This global spatially explicit (0.5 by 0.5 degree) analysis presents the nitrogen (N) and phosphorus (P) inputs, processing and biogeochemical retention and delivery to surface waters and river export to coastal seas according to the five shared socioeconomic pathways (SSP). Four systems are considered: (i) human system; (ii) agriculture; (iii) aquaculture; (iv) nature. Exploring the changes during 1980–2015 and 2015–2050 according to the SSPs shows that the natural nutrient sources have been declining in the past decades and will continue to decline in all SSPs in future decades due to massive land transformations, while agriculture, human sewage and aquaculture are becoming increasingly dominant (globally up to 80% of nutrient delivery). More efforts than those employed in any of the SSPs are needed to slow down the global nutrient cycles. One of the drivers of the proliferation of harmful algal blooms is the tendency towards increasing N:P ratios in global freshwaters and export to the global coastal seas; this is the result of increasing N:P in inputs in food production, more efficient biogeochemical retention of P than of N in river basins, and groundwater N legacies, which seems to be most pronounced in a united world that strives after sustainability. The diverging strategies to achieve UN Sustainable Development Goals 14 (life below water), 2 (zero hunger) and 6 (clean water and sanitation) therefore require a balanced management system for both N and P in all systems, that accounts for future nutrient legacies.
We present the experimental protocol and data analysis toolbox for multi-contact 4C (MC-4C), a new proximity ligation method tailored to study the higher-order chromatin contact patterns of selected ...genomic sites. Conventional chromatin conformation capture (3C) methods fragment proximity ligation products for efficient analysis of pairwise DNA contacts. By contrast, MC-4C is designed to preserve and collect large concatemers of proximity ligated fragments for long-molecule sequencing on an Oxford Nanopore or Pacific Biosciences platform. Each concatemer of proximity ligation products represents a snapshot topology of a different individual allele, revealing its multi-way chromatin interactions. By inverse PCR with primers specific for a fragment of interest (the viewpoint) and DNA size selection, sequencing is selectively targeted to thousands of different complex interactions containing this viewpoint. A tailored statistical analysis toolbox is able to generate background models and three-way interaction profiles from the same dataset. These profiles can be used to distinguish whether contacts between more than two regulatory sequences are mutually exclusive or, conversely, simultaneously occurring at chromatin hubs. The entire procedure can be completed in 2 w, and requires standard molecular biology and data analysis skills and equipment, plus access to a third-generation sequencing platform.
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