Nitrogen (N) deposition in China has increased greatly, but the general impact of elevated N deposition on carbon (C) dynamics in Chinese terrestrial ecosystems is not well documented. In this study we used a meta-analysis method to compile 88 studies on the effects of N deposition C cycling on Chinese terrestrial ecosystems. Our results showed that N addition did not change soil C pools but increased above-ground plant C pool. A large decrease in below-ground plant C pool was observed. Our result also showed that the impacts of N addition on ecosystem C dynamics depend on ecosystem type and rate of N addition. Overall, our findings suggest that 1) decreased below-ground plant C pool may limit long-term soil C sequestration; and 2) it is better to treat N-rich and N-limited ecosystems differently in modeling effects of N deposition on ecosystem C cycle.

Seagrass ecosystems, considered among the most efficient carbon sinks worldwide, encompass a wide variety of spatial configurations in the coastal landscape. Here we evaluated the influence of the spatial configuration of seagrass meadows at small scales (metres) on carbon storage in seagrass sediments. We intensively sampled carbon stocks and other geochemical properties (δ13C, particle size, depositional fluxes) across seagrass–sand edges in a Zostera muelleri patchy seagrass landscape. Carbon stocks were significantly higher (ca. 20%) inside seagrass patches than at seagrass–sand edges and bare sediments. Deposition was similar among all positions and most of the carbon was from allochthonous sources. Patch level attributes (e.g. edge distance) represent important determinants of the spatial heterogeneity of carbon stocks within seagrass ecosystems. Our findings indicate that carbon stocks of seagrass areas have likely been overestimated by not considering the influence of meadow landscapes, and have important relevance for the design of seagrass carbon stock assessments.

Inadequately treated effluents from industry have serious environmental and public health concerns. Even low level discharges create problems through accumulation in water and soil. In the present work, the pollutant accumulating capacity and the general environmental health status of soil which is a repository of treated and untreated effluent discharges and solid waste dumping of a giant pulp and paper mill have been evaluated with respect to some selected physicochemical parameters. The pollutant accumulating capacity of the soil in seven well-defined sites in and around the mill was found with reference to a “control” site with no history of receiving effluent discharges or solid wastes. The changes in texture, bulk density, water-holding capacity, electrical conductivity, pH, organic carbon, cation exchange capacity, exchangeable sodium, etc. of the soil up to the normal tilled depth were observed in different seasons. In most sites, the soil organic carbon was poorly correlated to the bulk density, water-holding capacity, pH, and clay and sand contents, indicating an unhealthy state of the soil and, correspondingly, nearly exhausted pollutant accumulating capacity. Considerable differences in pH, electrical conductivity, bulk density, and water-holding capacity were observed between the soil receiving effluent discharge and solid waste dumping and the control soil. The soil had accumulated considerable amounts of the exchangeable cations (Ca, Mg, Na, and K). The work has found that industrial activities have worked against the normal behavior of the soil and reduced its capacity to serve as a natural repository of carbon.

Saplings of alder (Alnus glutinosa), birch (Betula pendula), hazel (Corylus avellana), beech (Fagus sylvatica), ash (Fraxinus excelsior) and oak (Quercus robur) were exposed to five episodic ozone regimes in solardomes, with treatment means between 16 and 72 ppb. All trees were kept fully watered for the first 5 weeks of exposure, after which half the trees continued to be well-watered, whereas the other half were subjected to a moderate drought by applying approximately 45 % of the amount of water. Species-specific reductions in growth in response to both ozone and drought were found, which could result in reduced potential carbon sequestration in future ozone climates. In well watered conditions, the ozone treatments resulted in total biomass reductions for oak (18 %), alder (16 %), beech (15 %), ash (14 %), birch (14 %) and hazel (7 %) in the 72 ppb compared with the 32 ppb treatment. For beech, there was a reduction in growth in response to ozone in the well-watered treatment, but an increase in growth in response to ozone in the drought treatment, in contrast to the decreased growth that would occur as a result of stomatal closure in response to either the ozone or drought treatment, and therefore assumed to result from changes in hormonal signalling which could result in stomatal opening in combined ozone and drought conditions. For alder, in addition to a decrease in root biomass, there was reduced biomass of root nodules with high compared with low ozone for both drought-treated and well-watered trees. There was also a large reduction in the biomass of nodules from drought trees compared with well-watered. It is therefore possible that changes in the nitrogen dynamics of alder could occur due to reduced nodulation in both drought and elevated ozone conditions.

Mineral carbonation of serpentinite mining residue offers an environmentally secure and permanent storage of carbon dioxide. The strategy of using readily available mining residue for the direct treatment of flue gas could improve the energy demand and economics of CO₂ sequestration by avoiding the mineral extraction and separate CO₂ capture steps. The present is a laboratory scale study to assess the possibility of CO₂ fixation in serpentinite mining residues via direct gas–solid reaction. The degree of carbonation is measured both in the absence and presence of water vapor in a batch reactor. The gas used is a simulated gas mixture reproducing an average cement flue gas CO₂ composition of 18 vol.% CO₂. The reaction parameters considered are temperature, total gas pressure, time, and concentration of water vapor. In the absence of water vapor, the gas–solid carbonation of serpentinite mining residues is negligible, but the residues removed CO₂ from the feed gas possibly due to reversible adsorption. The presence of small amount of water vapor enhances the gas–solid carbonation, but the measured rates are too low for practical application. The maximum CO₂ fixation obtained is 0.07 g CO₂ when reacting 1 g of residue at 200 °C and 25 barg (pCO₂ ≈ 4.7) in a gas mixture containing 18 vol.% CO₂ and 10 vol.% water vapor in 1 h. The fixation is likely surface limited and restricted due to poor gas–solid interaction. It was identified that both the relative humidity and carbon dioxide-water vapor ratio have a role in CO₂ fixation regardless of the percentage of water vapor.

Renewable biomass has attracted great attention for the production of biooil, biogas, and biochar, a carbon residual applicable for carbon sequestration and environmental remediation. Rice straw is one of the most common biomasses among agricultural wastes in South Korea. As part of our advanced and environmentally friendly research, we applied biochar derived from rice straw as the anode material for lithium-ion batteries (LIBs). Porous carbons with a high surface area were prepared from rice straw. Such porous carbons have exhibited particularly large reversible capacity and hence proven to be a candidate anode material for high-rate and high-capacity LIBs. Rice straw-derived biochars were synthesized at four different temperatures: 400, 550, 700, and 900 °C. The surface was modified by using HCl and H₂O₂ on the 550 °C biochar in order to increase the surface area. The resulting biochar was characterized by X-ray diffraction (XRD) and field-emission scanning electron microscopy (FE-SEM). The surface area was measured by Brunauer–Emmett–Teller (BET) method. The electrochemical characterizations were investigated by galvanostatic charge–discharge (CD) curves, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). All samples exhibited reversible capacities of below 200 mAh g⁻¹. The surface-modified biochars exhibited improved cycle performance. Surface modification using HCl showed better cycle performance than H₂O₂. However, the capacities of the treated 550 °C biochar were similar to those of non-surface-modified biochar.

The invasion by exotic cordgrass (Spartina alterniflora) has become one of the most serious and challenging environmental and ecological problems in coastal China because it can have adverse effects on local native species, thereby changing ecosystem processes, functions, and services. In this study, 300 surface sediments were collected from 15 stations in the Jiulong River Estuary, southeast China, across four different seasons, in order to reveal the spatiotemporal variability of biogenic elements and their influencing factors in the subtropical coastal mangrove wetland. The biogenic elements including carbon, nitrogen, and sulfur (C, N, and S) were determined by an element analyzer, while the phosphorus (P) was determined by a flow injection analyzer. The concentrations of biogenic elements showed no significant differences among four seasons except total phosphorus (TP); however, our ANOVA analyses revealed a distinct spatial pattern which was closely related with the vegetation type and tidal level. Values of total carbon (TC) and total nitrogen (TN) in the surface sediment of mangrove vegetation zones were higher than those in the cordgrass and mudflat zones. The concentrations of TC, TN, TP, and total sulfur (TS) in the high tidal zones were higher than those in the middle and low tidal zones. Redundancy analysis (RDA) revealed that tidal level, vegetation type, and season had some significant influence on the distribution of biogenic elements in the Jiulong River Estuary, by explaining 18.2, 7.7, and 4.9 % of total variation in the four biogenic elements, respectively. In conclusion, S. alterniflora invasion had substantial effects on the distributions of biogenic elements in the subtropical coastal wetland. If regional changes in the Jiulong River Estuary are to persist and much of the mangrove vegetation was to be replaced by cordgrass, there would be significant decreases on the overall storage of C and N in this coastal zone. Therefore, the native mangrove reforestation and exotic cordgrass elimination should be a priority in mangrove sustainable management for coastal ecosystem health.

Alum water treatment sludge is composed of amorphous hydroxyl-Al, which has variable charge surfaces with a large Brunauer-Emmett-Teller (BET) surface area (103 m⁻² g⁻¹) capable of specific adsorption of organic matter molecules, phosphate, and heavy metals. The effects of adding dried, ground, alum water treatment sludge (10 % w/w) to the feedstock for composting municipal green waste alone, green waste plus poultry manure, or green waste plus biosolids were determined. Addition of water treatment sludge reduced water soluble C, microbial biomass C, CO₂ evolution, extractable P, and extractable heavy metals during composting. The decrease in CO₂ evolution (i.e., C sequestration) was greatest for poultry manure and least for biosolid composts. The effects of addition of water treatment sludge to mature green waste-based poultry manure and biosolid composts were also determined in a 24-week incubation experiment. The composts were either incubated alone or after addition to a soil. Extractable P and heavy metal concentrations were decreased by additions of water treatment sludge in all treatments, and CO₂ evolution was also reduced from the poultry manure compost over the first 16–18 weeks. However, for biosolid compost, addition of water treatment sludge increased microbial biomass C and CO₂ evolution rate over the entire 24-week incubation period. This was attributed to the greatly reduced extractable heavy metal concentrations (As, Cr, Cu, Pb, and Zn) present following addition of water treatment sludge, and thus increased microbial activity. It was concluded that addition of water treatment sludge reduces concentrations of extractable P and heavy metals in composts and that its effect on organic matter stabilization is much greater during the composting process than for mature compost because levels of easily decomposable organic matter are initially much higher in the feedstock than those in matured composts.