Blue carbon sink function and carbon neutrality potential of mangroves

Uncovering the world's largest carbon sink-a profile of ocean carbon sinks research

As the world's largest carbon sink, the oceans are essential to achieving the 1.5 °C target. Marine ecosystems play a crucial role in the "sink enhancement" process. A deeper comprehension of research trends, hotspots, and the boundaries of ocean carbon sinks is necessary for a more effective response to climate change. To this end, academic literature in the field of ocean carbon sinks was investigated and analyzed using the core database of the Web of Science. The results show that (1) The ocean carbon sink is a global study. The number of literatures in the field of ocean carbon sinks is growing, and the USA and China are the main leaders, with the USA accounting for 31.19% of the global publications and China accounting for 26.57% of the global publications, and the environmental science discipline is the most popular in this field. (2) Keyword burst detection shows that the keywords "sink, sensitivity, land, dynamics, and seagrass" appear earliest and have high burst intensity, which are the hot spots of research in this field; the keyword clustering shows that the global ocean carbon sinks research mainly focuses on three themes: (i) carbon cycle and climate change; (ii) carbon sinks estimation models and techniques; and (iii) carbon sinks capacity and ocean biological carbon sequestration in different seas. Finally, targeted research recommendations are proposed to further match the ocean carbon sink research.

How to achieve carbon neutrality and low-carbon economic development-evidence from provincial data in China

"Carbon Peaking and Carbon Neutrality" is a major strategy for China to cope with climate change at present. We define the carbon neutrality capability (CNC) to reflect the current situation of regional carbon neutrality, and propose a new coupling model to explore the coupling relationship between regional economic development and carbon neutrality capability (CNC). Finally, the influence mechanism of the energy consumption structure on CNC was further discussed by using STRIPAT model. The results show that: during we study period, the national average carbon sink was about 77.89 Mt, and the carbon sinks in Inner Mongolia, Heilongjiang, Sichuan and Yunnan were as high as 164 Mt, mainly concentrated in the western region. The national average carbon source is 222.12 Mt, which is about three times that of carbon sink. The carbon source in Shandong, Hebei and Jiangsu are as high as 400 Mt or more, mainly concentrated in the eastern region. In addition, the growth rate of carbon source is much faster than that of carbon sink, especially the carbon emission caused by energy consumption, which leads to a general decline in CNC, and the development of CNC in various provinces is not optimistic. CNC and economic development level of most provinces are in a state of recession decoupling, and the coupling state of the provinces studied in certain years is significantly different. The spatial distribution of CNC and GDP has shown a northeast-southwest pattern. In addition, the influence of coal consumption structure on CNC is significantly negative, so we should optimize the energy consumption structure and increase the proportion of clean energy consumption. This study can make clear the current carbon neutrality capability of provinces in China, facilitate the formulation and adjustment of emission reduction strategies of provinces and cities, and help China to achieve carbon neutrality as soon as possible.

Di-2-ethylhexyl phthalate (DEHP) degradation and microbial community change in mangrove rhizosphere gradients

Di-2-ethylhexyl phthalate (DEHP) is a widespread persistent organic pollutant in the environment. As an ultimate barrier preventing pollutant entry into the ocean, mangrove plays an important role in coastal ecosystem. However, little information is known about DEHP degradation in mangrove rhizosphere. In this study, a rhizobox was used to separate four consecutive rhizosphere compartments with distance of 0-2, 2-4, 4-6, and > 6 mm to the rhizoplane of Kandelia obovata and investigate DEHP gradient degradation behavior in rhizosphere. Sediments closer to the rhizoplane exhibited higher DEHP degradation efficiencies (74.4 % in 0-2 mm layer). More precisely, mangrove rhizosphere promoted the benzoic acid pathway and non-selectively accelerated the production of mono(2-ethylhexyl) phthalate, phthalic acid and benzoic acid. Higher sediment organic matter content, lower pH and less humus in rhizosphere benefited DEHP hydrolysis. In addition, rhizosphere significantly increased microbial biomass and activities comparing to bulk sediments. Some bacterial lineages with potential DEHP degradation capability exhibited a distance-dependent pattern that decreased with the distance to the rhizoplane, including Bacillales, Acidothermaceae, Gammaproteobacteria, and Sphingobacteriales. Our findings suggested that mangrove rhizosphere could accelerate DEHP degradation by altering sediment physicochemical properties and microbial composition, showing positive effects on coastal ecosystem services for eliminating phthalate acid ester contamination.

Distribution, Risk Assessment and Source of Heavy Metals in Mangrove Wetland Sediments of Dongzhai Harbor, South China

Heavy metals are common environmental contaminants that are toxic, non-biodegradable, and bioaccumulative. They can bioaccumulate through the food chain and present a risk to both public health and ecology. Therefore, this study takes the mangrove wetland of Dongzhai Harbor as an example. The concentrations of heavy metals such as As, Cd, Cr, Cu, Ni, Pb, and Zn in the surface sediments of mangrove wetlands were measured to reveal their distribution, the contamination level was assessed, and the sources of contamination were analyzed. The distribution of Cr, Zn, Ni, Pb, Cu, and Cd concentrations are: Yanfeng East River > Sanjiang River > Yanzhou River > Yanfeng West River, while the As concentration in the Yanfeng West River is greater than that in the Yanfeng East River. According to the correlation analysis, the concentrations of Cr, Zn, Ni, Cu, and Cd are significantly and positively correlated with total organic carbon (TOC), total phosphorus (TP), total nitrogen (TN), and salinity (SAL) and shared a significantly negative correlation with pH. There is moderate contamination risk of As and slight contamination risk of Cd, Cr, Cu, Ni, Pb, and Zn in most regions within the study area. Cd, Cr, Cu, Ni, Pb, and Zn exhibit the same sources, which are mainly influenced by human sources such as aquaculture, agricultural cultivation, and livestock farming, while the source of As comes from aquaculture.

Evidence of improvements in the water quality of coastal areas around China

Coastal areas are huge carbon stores and hotspots for marine carbon fixation. Changes in the water quality of coastal areas are closely linked to their carbon fixation function. In this study, monitoring data were analyzed to identify how the water quality in China's coastal areas changed from 2001 to 2020. The results showed that the water quality in the coastal areas had improved gradually since 2001. The proportion of water quality in Class II and above gradually increased from 41.4% in 2001 to 77.4% in 2020, meanwhile, the proportion of water quality less than Class II, decreased from 58.6% to 22.6%, respectively. Of the four sea areas, the water quality was best in the Yellow Sea, and was poor in the East China Sea. The water quality varied between the different coastal provinces and cities and was good in coastal areas of Hainan, Guangxi, Shandong, and other provinces and cities, but was poor in Shanghai, Zhejiang, and Tianjin. Terrestrial anthropogenic pollutants were the main influence on the water quality in the coastal areas. As a hotspot for fixing blue carbon, the continuous improvement of the water quality of coastal areas laid a foundation for the health of the blue carbon ecosystems.