Long-Term Nutrient Variations in the Bohai Sea Over the Past 40 Years

As China's only continental sea, the Bohai Sea is a relatively closed environment and is vulnerable to natural changes and human activities. In this paper, the long-term variations in nutrients in the Bohai Sea and the potential influencing factors were analyzed based on historical summer and winter data from 1978 to 2016. The results showed that the concentrations of dissolved inorganic nitrogen (DIN) in the Bohai Sea continuously increased from 1990 and rapidly increased after 2002, the phosphate (PO 4 -P) concentration exhibited a decreasing trend, and the silicate (SiO 3 -Si) concentration decreased from 1978 to 1987 and increased from 1987 to 2008. The nutrient concentrations were lower in summer than in winter, and the bottom concentrations were higher than the surface concentrations in summer, whereas the vertical differences were insignificant in winter. The dominant factor determining the long-term variations in DIN were atmospheric deposition and nonpoint sources due to various human activities; the primary factors affecting PO 4 -P were riverine inputs and nonpoint sources related to natural changes and human activities; the primary factors afftecting SiO 3 -Si were riverine inputs. The N/P ratio followed the DIN variation, the Si/P ratio followed the SiO 3 -Si variation, and the Si/N ratio decreased. The nutrient ratios were lower at the bottom than at the surface and were lower in winter than in summer. The nutrient limitation changed from nitrogen limitation to phosphorus and silicon limitations. The long-term nutrient variations in the Bohai Sea have potential ecological impacts on the local red tide features

Gradual Enhancement of Stripe-Type Antiferromagnetism in Spin Ladder Material BaFe2_2S3_3 Under Pressure

We report pressure-dependent neutron diffraction and muon spin relaxation/rotation measurements combined with first-principles calculations to investigate the structural, magnetic, and electronic properties of BaFe$_2$S$_3$ under pressure. The experimental results reveal a gradual enhancement of the stripe-type ordering temperature with increasing pressure up to 2.6 GPa and no observable change in the size of the ordered moment. The ab initio calculations suggest that the magnetism is highly sensitive to the Fe-S bond lengths and angles, clarifying discrepancies with previously published results. In contrast to our experimental observations, the calculations predict a monotonic reduction of the ordered moment with pressure. We suggest that the robustness of the stripe-type antiferromagnetism is due to strong electron correlations not fully considered in the calculations

A Mott insulator continuously connected to iron pnictide superconductors

Iron-based superconductivity develops near an antiferromagnetic order and out of a bad metal normal state, which has been interpreted as originating from a proximate Mott transition. Whether an actual Mott insulator can be realized in the phase diagram of the iron pnictides remains an open question. Here we use transport, transmission electron microscopy, X-ray absorption spectroscopy, and neutron scattering to demonstrate that NaFe$_{1-x}$Cu$_x$As near $x\approx 0.5$ exhibits real space Fe and Cu ordering, and are antiferromagnetic insulators with the insulating behavior persisting above the N\'eel temperature, indicative of a Mott insulator. Upon decreasing $x$ from $0.5$, the antiferromagnetic ordered moment continuously decreases, yielding to superconductivity around $x=0.05$. Our discovery of a Mott insulating state in NaFe$_{1-x}$Cu$_x$As thus makes it the only known Fe-based material in which superconductivity can be smoothly connected to the Mott insulating state, highlighting the important role of electron correlations in the high-$T_{\rm c}$ superconductivity.Comment: in press, Nat. Commun., 4 figures, supplementary information available upon reques

The impact of giant jellyfish Nemopilema nomurai blooms on plankton communities in a temperate marginal sea

Abstract(#br)This study focused on the bloom-developing process of the giant jellyfish, Nemopilema nomurai , on phytoplankton and microzooplankton communities. Two repeated field observations on the jellyfish bloom were conducted in June 2012 and 2014 in the southern Yellow Sea where blooms of N . nomurai were frequently observed. We demonstrated that the bloom was made up of two stages, namely the developing stage and the mature stage. Total chlorophyll a increased and the concentrations of inorganic nutrients decreased during the developing stage, while both concentrations maintained stable and at low levels during the mature stage. Our analysis revealed that phosphate excreted by growing N . nomurai promoted the growth of phytoplankton at the developing stage. At the mature stage, size compositions of microzooplankton were altered and tended to be smaller via a top-down process, while phytoplankton compositions, affected mainly through a bottom-up process, shifted to be less diatoms and cryptophytes but more dinoflagellates

Harmful Algal Blooms in Chinese Coastal Waters Will Persist Due to Perturbed Nutrient Ratios

The three large marine ecosystems (LMEs) bordering China (Yellow Sea/Bohai Sea, East China Sea, and South China Sea) have received excess nitrogen (N) and phosphorus (P) in the past decades with detrimental consequences for ecosystem functioning, such as increased productivity, loss of biodiversity, and proliferation of harmful algal blooms (HABs). N loading increased much faster than that of P. Here, we show that HABs in the three LMEs started to proliferate after the N:P molar ratio exceeded the threshold value of 25 in the 1980s. The mismatch of N and P inputs is not only related to differences in loads but also inherent to the differences in their biogeochemical cycles which more efficiently filter P than N in land- and waterscapes. Future Shared Socioeconomic Pathways show that high N:P ratios will persist for decades to come, even worsening in a future oriented toward sustainability, and indicate that HABs may be a persisting problem in China’s coastal waters. While efforts in agricultural systems are governed by the agronomic crop requirements and are not easy to manage with respect to N:P ratios, the separate collection of urine in urban and rural areas could contribute to decreases in both total nutrient loads and N:P ratios

Seasonal Variation and Sources of Dissolved Nutrients in the Yellow River, China

The rapid growth of the economy in China has caused dramatic growth in the industrial and agricultural development in the Yellow River (YR) watershed. The hydrology of the YR has changed dramatically due to the climate changes and water management practices, which have resulted in a great variation in the fluxes of riverine nutrients carried by the YR. To study these changes dissolved nutrients in the YR were measured monthly at Lijin station in the downstream region of the YR from 2002 to 2004. This study provides detailed information on the nutrient status for the relevant studies in the lower YR and the Bohai Sea. The YR was enriched in nitrate (average 314 μmol·L−1) with a lower concentration of dissolved silicate (average 131 μmol·L−1) and relatively low dissolved phosphate (average 0.35 μmol·L−1). Nutrient concentrations exhibited substantial seasonal and yearly variations. The annual fluxes of dissolved inorganic nitrogen, phosphate, and silicate in 2004 were 5.3, 2.5, and 4.2 times those in 2002, respectively, primarily due to the increase in river discharge. The relative contributions of nutrient inputs to nitrogen in the YR were: wastewater > fertilizer > atmospheric deposition > soil; while to phosphorus were: wastewater > fertilizer > soil > atmospheric deposition. The ratios of N, P and Si suggest that the YR at Lijin is strongly P-limited with respect to potential phytoplankton growth

Characterization of the Particle Size Fraction associated with Heavy Metals in Suspended Sediments of the Yellow River

Variations in the concentrations of particulate heavy metals and fluxes into the sea in the Yellow River were examined based on observational and measured data from January 2009 to December 2010. A custom-built water elutriation apparatus was used to separate suspended sediments into five size fractions. Clay and very fine silt is the dominant fraction in most of the suspended sediments, accounting for >40% of the samples. Cu, Pb, Zn, Cr, Fe and Mn are slightly affected by anthropogenic activities, while Cd is moderate affected. The concentrations of heavy metals increased with decrease in particle size. For suspended sediments in the Yellow River, on average 78%–82% of the total heavy metal loading accumulated in the <16 μm fraction. About 43% and 53% of heavy metal in 2009 and 2010 respectively, were readily transported to the Bohai Sea with “truly suspended” particles, which have potentially harmful effects on marine organisms

Strategies of property developers in the context of carbon tax.

China needs to guide property developers in actively reducing emissions to reach carbon emission reduction targets and respond to global climate change. A carbon tax is an important policy tool. Still, to establish successful rules to steer property developers' reasonable carbon emission reduction behavior, we must first explore property developers' decision-making mechanisms. This study develops an emission reduction and price game model for property developers under the constraint of a carbon tax. It then applies reverse order induction and optimization methods to identify the game equilibrium solution for property developers. Using the game equilibria, we explore the carbon tax mechanism on emission reduction and property developer pricing strategies. We can derive the following conclusions if the carbon tax policy is not implemented: 1.House prices are related to the substitutability of the two types of competitive property developers. 2.The greater the substitutability, the greater the cost of emission reduction paid by consumers. 3.The game equilibrium carbon emission intensity is the average carbon emission intensity of the housing business. In the situation of enacting a carbon tax, we arrive at the following conclusions: 1.The profits of real estate developers who do not have the advantage of emission reduction continue to decline with the increase of carbon tax. 2. For real estate developers who have the advantage of decreasing emissions, profits declined initially and then increased as the carbon tax rate increased, and only when the carbon tax rate reaches Tm1* can they fully leverage the cost advantage and obtain ever-increasing profits. 3.Low tax rates should be adopted by the government at the start of the implementation of the carbon tax policy to provide a buffer time for real estate developers who do not have the advantage of emission reduction costs

Nitrogen transport, transformation, and retention in the Three Gorges Reservoir : A mass balance approach

Dam construction in river systems affects the biogeochemistry of nitrogen (N), yet most studies on N cycling in reservoirs do not consider the transformations and retention of the different N species. This study addresses the N inputs, transport, transformations, and retention in the Three Gorges Reservoir (TGR) in the Changjiang River, the world largest water storage project, during its filling phase in 2004–2007. The results indicate that dissolved inorganic nitrogen (DIN) was the most abundant N form in the TGR and particulate N was only 2% to the total N flow and retention. About 34% of the dissolved organic nitrogen (DON), 64% of nitrite, and 44% of ammonia were retained by transformation within the TGR in 2007. Time-series data show that about 8% of inflowing total dissolved N was lost by denitrification and sedimentation. Transformations of DON, nitrite and ammonia caused an increase of the nitrate load by 6%; and at the same time the DIN flux increased by 4% while the water moved through the TGR, which is the balance between formation and retention of DIN. The large contribution of biogeochemical transformations to nitrate loading in the TGR indicates the importance of internal processing for the river N species composition

Nitrogen transport, transformation, and retention in the Three Gorges Reservoir: A mass balance approach

Dam construction in river systems affects the biogeochemistry of nitrogen (N), yet most studies on N cycling in reservoirs do not consider the transformations and retention of the different N species. This study addresses the N inputs, transport, transformations, and retention in the Three Gorges Reservoir (TGR) in the Changjiang River, the world largest water storage project, during its filling phase in 2004–2007. The results indicate that dissolved inorganic nitrogen (DIN) was the most abundant N form in the TGR and particulate N was only 2% to the total N flow and retention. About 34% of the dissolved organic nitrogen (DON), 64% of nitrite, and 44% of ammonia were retained by transformation within the TGR in 2007. Time-series data show that about 8% of inflowing total dissolved N was lost by denitrification and sedimentation. Transformations of DON, nitrite and ammonia caused an increase of the nitrate load by 6%; and at the same time the DIN flux increased by 4% while the water moved through the TGR, which is the balance between formation and retention of DIN. The large contribution of biogeochemical transformations to nitrate loading in the TGR indicates the importance of internal processing for the river N species composition