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Beginning in 2013, China launched two phases (2013–2017 and 2018–2020) of clean air actions that have led to substantial reductions in PM 2.5 concentrations. However, improvement in PM 2.5 pollution was notably slowing down during Phase II. Here we quantify the efficacy and drivers of PM 2.5 improvement and evaluate the associated cost during 2013–2020 using an integrated framework that combines an emission inventory model, a chemical transport model and detailed cost information. We found that national population-weighted mean PM 2.5 concentrations decreased by 19.8 μg m −3 and 10.9 μg m −3 in the two phases, and the contribution of clean air policies in Phase II (2.3 μg m −3  yr −1 ) was considerably lower than that of Phase I (4.5 μg m −3  yr −1 ), after excluding the impacts from meteorological condition changes and COVID-19 lockdowns. Enhanced structure transitions and targeted volatile organic compounds and NH 3 reduction measures have successfully reduced emissions in Phase II, but measures focusing on the end-of-pipe control were less effective after 2017. From 2013 to 2020, PM 2.5 abatement became increasingly challenging, with the average cost of reducing one unit of PM 2.5 concentration in Phase II twice that of Phase I. Our results suggest there is a need for strengthened, well-balanced, emission control strategies for multi-pollutants. China’s second phase of clean air actions proved less effective than the first, highlighting the need to adapt and update policies to enable continued progress, according to an assessment combining chemical transport modelling and emission inventories.

Per- and polyfluoroalkyl substances (PFAS) are a class of fluorinated chemicals used widely in consumer and industrial products. Their human toxicity and ecosystem impacts have received extensive public, scientific and regulatory attention. Regulatory PFAS guidance is rapidly evolving, with the inclusion of a wider range of PFAS included in advisories and a continued decrease in what is deemed safe PFAS concentrations. In this study we collated PFAS concentration data for over 45,000 surface and groundwater samples from around the world to assess the global extent of PFAS contamination and their potential future environmental burden. Here we show that a substantial fraction of sampled waters exceeds PFAS drinking water guidance values, with the extent of exceedance depending on the jurisdiction and PFAS source. Additionally, current monitoring practices probably underestimate PFAS in the environment given the limited suite of PFAS that are typically quantified but deemed of regulatory concern. An improved understanding of the range of PFAS embodied in consumer and industrial products is required to assess the environmental burden and develop mitigation measures. While PFAS is the focus of this study, it also highlights society’s need to better understand the use, fate and impacts of anthropogenic chemicals. A global data analysis suggests that a large fraction of surface waters and groundwaters globally have concentrations of per- and polyfluoroalkyl substances (PFAS) that exceed international advisories or national regulations.

The fate of plastics that enter the ocean is a longstanding puzzle. Recent estimates of the oceanic input of plastic are one to two orders of magnitude larger than the amount measured floating at the surface. This discrepancy could be due to overestimation of input estimates, processes removing plastic from the surface ocean or fragmentation and degradation. Here we present a 3D global marine mass budget of buoyant plastics that resolves this discrepancy. We assimilate observational data from different marine reservoirs, including coastlines, the ocean surface, and the deep ocean, into a numerical model, considering particle sizes of 0.1–1,600.0 mm. We find that larger plastics (>25 mm) contribute to more than 95% of the initially buoyant marine plastic mass: 3,100 out of 3,200 kilotonnes for the year 2020. Our model estimates an ocean plastic input of about 500 kilotonnes per year, less than previous estimates. Together, our estimated total amount and annual input of buoyant marine plastic litter suggest there is no missing sink of marine plastic pollution. The results support higher residence times of plastics in the marine environment compared with previous model studies, in line with observational evidence. Long-lived plastic pollution in the world’s oceans, which our model suggests is continuing to increase, could negatively impact ecosystems without countermeasures and prevention strategies.A 3D global marine plastic mass budget suggests that larger items contribute more than 95% of buoyant plastics by mass and are longer lived than previously estimated, which suggests there is no missing sink of marine plastic pollution.

Soil organic carbon sequestration has been promoted to combat climate change while improving soil fertility. However, its quantitative contribution to crop productivity has proven elusive. Using data from 13,662 controlled field trials with 66,593 treatments across a broad range of soils, climates and management practices, we here show that yields increase with increased soil organic carbon, until no further increase (p < 0.05) occurs above mean optimum soil organic carbon of 43.2–43.9 g kg−1 for maize, 12.7–13.4 g kg−1 for wheat and 31.2–32.4 g kg−1 for rice. Sequestering soil organic carbon is one-fifth as effective (that is, 80% less) as nitrogen fertilization for improving crop yield where soil management is optimized. By increasing soil organic carbon beyond current technology to optimum levels, global production of the three most important staple crops increases by 4.3% (sufficient to provide calories for 640 million people). However, currently available management practices would increase crop production by only 0.7% once other production constraints have already been addressed. Therefore, yield improvements under currently available technologies are unlikely to drive adoption of soil organic carbon sequestration globally, except in hot-spot regions where crop production benefits most, or unless novel practices that allow greater soil organic carbon sequestration beyond current limitations can further increase yields cost-effectively.Increasing soil organic carbon can, under optimum management only, enhance global production of maize, wheat and rice by up to 0.7% with important regional differences, according to 13,662 field trials across a broad range of soils, climates and management practices.

Increasing incidences of eutrophication and groundwater quality impairment from agricultural nitrogen pollution are threatening humans and ecosystem health. Minimal improvements in water quality have been achieved despite billions of dollars invested in conservation measures worldwide. Such apparent failures can be attributed in part to legacy nitrogen that has accumulated over decades of agricultural intensification and that can lead to time lags in water quality improvement. Here, we identify the key knowledge gaps related to landscape nitrogen legacies and propose approaches to manage and improve water quality, given the presence of these legacies. Agricultural nitrogen legacies are delaying improvements to water quality. Comprehensive management strategies that address legacy issues are needed to ensure better environmental outcomes.

Pesticides are widely used to protect food production and meet global food demand but are also ubiquitous environmental pollutants, causing adverse effects on water quality, biodiversity and human health. Here we use a global database of pesticide applications and a spatially explicit environmental model to estimate the world geography of environmental pollution risk caused by 92 active ingredients in 168 countries. We considered a region to be at risk of pollution if pesticide residues in the environment exceeded the no-effect concentrations, and to be at high risk if residues exceeded this by three orders of magnitude. We find that 64% of global agricultural land (approximately 24.5 million km 2 ) is at risk of pesticide pollution by more than one active ingredient, and 31% is at high risk. Among the high-risk areas, about 34% are in high-biodiversity regions, 5% in water-scarce areas and 19% in low- and lower-middle-income nations. We identify watersheds in South Africa, China, India, Australia and Argentina as high-concern regions because they have high pesticide pollution risk, bear high biodiversity and suffer from water scarcity. Our study expands earlier pesticide risk assessments as it accounts for multiple active ingredients and integrates risks in different environmental compartments at a global scale. Pesticide pollution is a risk for two-thirds of agriculture land. A third of high-risk areas are in high-biodiversity regions and a fifth are in low- and lower-middle-income areas, according to environmental modelling combined with pesticide application data.

Increasing atmospheric nitrogen deposition can influence food production, environmental quality and climate change from the regional to global scales. As the largest developing country, China is expected to experience a rapid increase in N deposition. However, the lack of information on dry N deposition limits our understanding of the historical trend of the total N deposition, as well as the main drivers of this trend. Here, we use extensive datasets that include both wet and dry N deposition to evaluate the spatiotemporal variation of N deposition and the changes of its components in China during 1980–2015. Three significant transitions in N deposition in China were observed. First, the total N deposition began to stabilize in 2001–2005, mostly due to a decline in wet NH4+ deposition. Subsequently, a shift to approximately equal wet and dry N deposition occurred in 2011–2015, accompanied by increasing dry deposition. Finally, the contribution of reduced N components in the deposition decreased due to increasing NO3− deposition. These transitions were jointly driven by changes in the socioeconomic structure in China and vigorous controls in N pollution. The three observed important transitions challenge the traditional views about the continuous increase in N deposition in China.Nitrogen deposition in China has been almost constant over the past decade, as decreasing wet deposition has balanced increasing dry deposition, according to analyses of extensive datasets on wet and dry nitrogen depositions in China.

In December 2019, the International Association of Geomagnetism and Aeronomy (IAGA) Division V Working Group (V-MOD) adopted the thirteenth generation of the International Geomagnetic Reference Field (IGRF). This IGRF updates the previous generation with a definitive main field model for epoch 2015.0, a main field model for epoch 2020.0, and a predictive linear secular variation for 2020.0 to 2025.0. This letter provides the equations defining the IGRF, the spherical harmonic coefficients for this thirteenth generation model, maps of magnetic declination, inclination and total field intensity for the epoch 2020.0, and maps of their predicted rate of change for the 2020.0 to 2025.0 time period.

Surface-water availability, defined as precipitation minus evapotranspiration, can be affected by changes in vegetation. These impacts can be local, due to the modification of evapotranspiration and precipitation, or non-local, due to changes in atmospheric moisture transport. However, the teleconnections of vegetation changes on water availability in downwind regions remain poorly constrained by observations. By linking measurements of local precipitation to a new hydrologically weighted leaf area index that accounts for both local and upwind vegetation contributions, we demonstrate that vegetation changes have increased global water availability at a rate of 0.26 mm yr −2 for the 2001–2018 period. Critically, this increase has attenuated about 15% of the recently observed decline in global water availability. The water availability increase is due to a greater rise in precipitation relative to evapotranspiration for over 53% of the global land surface. We also quantify the potential hydrological impacts of regional vegetation increases at any given location across global land areas. We find that enhanced vegetation is beneficial to both local and downwind water availability for ~45% of the land surface, whereas it is adverse elsewhere, primarily in water-limited or high-elevation regions. Our results highlight the potential strong effects of deliberate vegetation changes, such as afforestation programmes, on water resources beyond local and regional scales. Vegetation change over the past two decades has limited the decline in global water availability by enhancing rainfall over evapotranspiration, according to analysis of observation-based atmospheric moisture transport data.

Stressors such as large-scale damming, hydrological change, pollution, the introduction of non-native species and sediment mining are challenging the integrity and future of large rivers, according to a synthesis of the literature on the 32 biggest rivers.