Potential carbon sequestration in China’s forests

Forests are believed to be a major sink for atmospheric carbon dioxide. There are 158.94 million hectares (Mha) of forests in China, accounting for 16.5% of its land area. These extensive forests may play a vital role in the global carbon (C) cycle as well as making a large contribution to the country’s economic and environmental well-being. Currently there is a trend towards increased development in the forests. Hence, accounting for the role and potential of the forests in the global carbon budget is very important.In this paper, we attempt to estimate the carbon emissions and sequestration by Chinese forests in 1990 and make projections for the following 60 years based on three scenarios, i.e. “baseline”, “trend” and “planning”. A computer model F-CARBON 1.0, which takes into account the different biomass density and growth rates for the forests in different age classes, the life time for biomass oxidation and decomposition, and the change in soil carbon between harvesting and reforestation, was developed by the authors and used to make the calculations and projections. Climate change is not modelled in this exercise.We calculate that forests in China annually accumulate 118.1 Mt C in growth of trees and 18.4 Mt in forest soils, and release 38.9 Mt, resulting in a net sequestration of 97.6 Mt C, corresponding to 16.8% of the national CO₂ emissions in 1990. From 1990 to 2050, soil carbon accumulation was projected to increase slightly while carbon emissions increases by 73, 77 and 84%, and net carbon sequestration increases by −21, 52 and 90% for baseline, trend and planning scenarios, respectively. Carbon sequestration by China’s forests under the planning scenario in 2000, 2010, 2030 and 2050 is approximately 20, 48, 111 and 142% higher than projected by the baseline scenario, and 8, 18, 34 and 26% higher than by the trend scenario, respectively. Over 9 Gt C is projected to accumulate in China’s forests from 1990 to 2050 under the planning scenario, and this is 73 and 23% larger than projected for the baseline and trend scenarios, respectively. During the period 2008–2012, Chinese forests are likely to have a net uptake of 667, 565 and 452 Mt C, respectively, for the planning, trend and baseline scenarios. We conclude that China’s forests have a large potential for carbon sequestration through forest development. Sensitivity analysis showed that the biggest uncertainty in the projection by the F-CARBON model came from the release coefficient of soil carbon between periods after harvesting and before reforestation.     

Storage and sequestration of organic carbon in major paddy soils of China： Mechanism, stability and the impact on global change——A key project funded by the National Natural Science Foundation of China（2003-2005）

Chinapaddysoilsoccupyalandareaofabout3×107hm2andproduce44%oftotalcerealsofthestatewithalandportionof25%.Managementofpaddysoilscanbetracedbackto7000yearsB.P.andhaveledtoaparticularsoiltypeofanthropogenicwetlandsoilswithenhancedCstorageincomparisonwiththeu…     

Status of mercury pollution during resources development in Guizhou Province, China

1　ＩｎｔｒｏｄｕｃｔｉｏｎＧｕｉｚｈｏｕＰｒｏｖｉｎｃｅｉｓｌｏｃａｔｅｄｉｎｓｏｕｔｈｗｅｓｔＣｈｉｎａｗｉｔｈａｔｏｔａｌａｒｅａｏｆ 176.2 8ｔｈｏｕｓａｎｄｓｑｕａｒｅｋｉｌｏｍｅｔｅｒｓ,ｏｆｗｈｉｃｈ 87%ｉｓｍｏｕｎｔａｉｎ ,10 %ｉｓｈｉｌｌｓ,3%ｉｓｒｉｖｅｒ,ｂａｓｉｎａｎｄｐｌａｉｎ .Ｇｕｉｚｈｏｕｉｓａｍｏｕｎｔａｉｎｏｕｓｐｒｏｖｉｎｃｅｗｉｔｈｒｉｃｈｍｉｎｅｒａｌｒｅｓｏｕｒｃｅｓ,ａｍｏｎｇｗｈｉｃｈｍｅｒｃｕｒｙｒｅｓｅｒｖｅｒａｎｋｓｆｉｒｓｔｉｎＣｈｉｎａ,ｅｖｅｎｉ…     

Trends of the sunshine duration and diffuse radiation percentage on sunny days in urban agglomerations of China during 1960–2005

The long-term observational data of sunshine duration (SD) and diffuse radiation percentage (defined as diffuse solar radiation/total solar radiation, DRP) on sunny days during 1960–2005 were analyzed in 7 urban agglomerations and the whole of China. The results show that the sunny sunshine duration (SSD) has decreased significantly except at a few stations over northwestern China in the past 46 years. An obvious decrease of the SSD is found in eastern China, with the trend coefficients lower than − 0.8. Accompanied by the SSD decline, the sunny diffuse radiation percentage (SDRP) in most stations shows obvious increasing trends during the 46 years. The averaged SDRP over China has increased 2.33% per decade, while the averaged SSD shows a decrease of − 0.13 hr/day per decade. The correlation coefficient between SDRP and SSD is − 0.88. SSD decreased over urban agglomerations (small to large city clusters) in the past 46 years, especially in large cities and medium cities, due to the strong anthropogenic activities and air pollution represented by aerosol option depth (AOD) and tropospheric column NO₂ (TroNO₂). On the regional scale, SSD has an opposite trend from SDRP during 1960 to 2005, and the variation trends of regional mean values of SSD and SDRP in southeastern China are more pronounced than those in northwestern China.     

Effect of different fertilizers on methane emission from a paddy field of Zhejiang, China

ＩｎｔｒｏｄｕｃｔｉｏｎＩｎｃｒｅａｓｅｄａｇｒｉｃｕｌｔｕｒａｌｐｒｏｄｕｃｔｉｖｉｔｙｏｖｅｒｔｈｅｐａｓｔ５０—１００ｙｅａｒｓｈａｓｌｅｄｔｏｉｎｃｒｅａｓｅｄａｔｍｏｓｐｈｅｒｉｃｃｏｎｃｅｎｔｒａｔｉｏｎｓｏｆＣＯ２，ＣＨ４ａｎｄＮ２Ｏ．Ｔｈｅｓｅｇａｓｅｓ，ａｌｏｎｇｗｉｔｈａｄｄｉｔｉｏｎｔｒａｃｅｇａｓｓｐｅｃｉｅｓ（ｇｒｅｅｎｈｏｕｓｅｇａｓｅｓ）ａｒｅｃａｕｓｉｎｇａｎｉｎｃｒｅａｓｅｉｎｇｌｏｂａｌｔｅｍｐｅｒａｔｕｒｅｓａｎｄｏｚｏｎｅｄｅｐｌｅｔｉｏｎ（Ａｓｅｌｍａｎ…     

Effect of petroleum on decomposition of shrub–grass litters in soil in Northern Shaanxi of China

The impacts of petroleum contamination on the litter decomposition of shrub–grass land would directly influence nutrient cycling, and the stability and function of ecosystem. Ten common shrub and grass species from Yujiaping oil deposits were studied. Litters from these species were placed into litterbags and buried in petroleum-contaminated soil with 3 levels of contamination (slight, moderate and serious pollution with petroleum concentrations of 15, 30 and 45 g/kg, respectively). A decomposition experiment was then conducted in the lab to investigate the impacts of petroleum contamination on litter decomposition rates. Slight pollution did not inhibit the decomposition of any litters and significantly promoted the litter decomposition of Hippophae rhamnoides, Caragana korshinskii, Amorpha fruticosa, Ziziphus jujuba var. spinosa, Periploca sepium, Medicago sativa and Bothriochloa ischaemum. Moderate pollution significantly inhibited litter decomposition of M. sativa, Coronilla varia, Artemisia vestita and Trrifolium repens and significantly promoted the litter decomposition of C. korshinskii, Z. jujuba var. spinosa and P. sepium. Serious pollution significantly inhibited the litter decomposition of H. rhamnoides, A. fruticosa, B. ischaemum and A. vestita and significantly promoted the litter decomposition of Z. jujuba var. spinosa, P. sepium and M. sativa. In addition, the impacts of petroleum contamination did not exhibit a uniform increase or decrease as petroleum concentration increased. Inhibitory effects of petroleum on litter decomposition may hinder the substance cycling and result in the degradation of plant communities in contaminated areas.     

Ancient paddy soils from the Neolithic age in China’s Yangtze River Delta

Identifying prehistoric irrigated rice fields and characterizing the beginning of paddy soil development are important for a better understanding of human development and agricultural history. In 2003, paddy soils and irrigated rice fields buried at a depth of 100–130 cm were excavated at Chuo-dun-shan in the Yangtze River Delta, close to Suzhou, China. The fields of sizes between 1.4 and 16 m² were surrounded with ridges that were connected to ditches/ponds via outlets to control the water level within the fields. Many carbonized and partly carbonized rice grains with an age of 3,903 B.C.(measured ¹⁴C age 5,129±45 a BP) were recovered. The surface layers of these buried paddy fields showed a high content of soil organic matter and a considerable high density of rice opals. The latter were identified to derive from Oryza spp. Solid-state ¹³C nuclear magnetic resonance spectroscopy revealed aromatic carbon (C) as the predominant organic C form in the fossil surface layer. This is expected, if the major source represents burnt rice and straw. In summary, our data are in agreement with new evidences indicating that in China, paddy soils and irrigated rice cultivation were initiated and developed more than 6,000 years ago.     

Adsorption–desorption behavior of atrazine on agricultural soils in China

Adsorptionanddesorptionareimportantprocessesthataffectatrazinetransport,transformation,andbioavailabilityinsoils.Inthisstudy,theadsorption–desorptioncharacteristicsofatrazinein three soils (laterite, paddy soil and alluvial soil) were evaluated using the batch equilibrium method. The results showed that the kinetics of atrazine in soils was completed in two steps: a “fast” adsorption and a “slow” adsorption and could be well described by pseudo-second-order model.In addition,the adsorption equilibrium isotherms were nonlinear and were well fitted by Freundlich and Langmuir models. It was found that the adsorption data on laterite, and paddy soil were better fitted by the Freundlich model;as for alluvial soil,the Langmuir model described it better. The maximum atrazine sorption capacities ranked as follows: paddy soil > alluvial soil > laterite. Results of thermodynamic calculations indicated that atrazine adsorption on three tested soils was spontaneous and endothermic. The desorption data showed that negative hysteresis occurred. Furthermore, lower solution pH value was conducive to the adsorptionofatrazineinsoils.Theatrazineadsorptioninthesethreetestedsoilswascontrolled by physical adsorption, including partition and surface adsorption. At lower equilibrium concentration, the atrazine adsorption process in soils was dominated by surface adsorption;while with the increase of equilibrium concentration, partition was predominant.     

Adsorption–desorption behavior of atrazine on agricultural soils in China

Adsorption and desorption are important processes that affect atrazine transport,transformation,and bioavailability in soils.In this study,the adsorption–desorption characteristics of atrazine in three soils(laterite,paddy soil and alluvial soil) were evaluated using the batch equilibrium method.The results showed that the kinetics of atrazine in soils was completed in two steps:a"fast" adsorption and a "slow" adsorption and could be well described by pseudo-second-order model.In addition,the adsorption equilibrium isotherms were nonlinear and were well fitted by Freundlich and Langmuir models.It was found that the adsorption data on laterite,and paddy soil were better fitted by the Freundlich model;as for alluvial soil,the Langmuir model described it better.The maximum atrazine sorption capacities ranked as follows:paddy soil alluvial soil laterite.Results of thermodynamic calculations indicated that atrazine adsorption on three tested soils was spontaneous and endothermic.The desorption data showed that negative hysteresis occurred.Furthermore,lower solution pH value was conducive to the adsorption of atrazine in soils.The atrazine adsorption in these three tested soils was controlled by physical adsorption,including partition and surface adsorption.At lower equilibrium concentration,the atrazine adsorption process in soils was dominated by surface adsorption;while with the increase of equilibrium concentration,partition was predominant.     

Sources of methane in China

Continuous measurements of the methane flux from rice fields in Hangzhou，eastern China，arid Leshan，Sichuan Province，were carried out for 3 years．The results show that the methane flux from rice fields has a strong diurnal variation which may be explained by the soil temperature effects and rice plant growing activities，and that the day-mean flux has a large seasonal variation which may be related to soil temperature and the availability of organic substrate in the soil．An overall sources of methane for China are estimated while the rice fields are major sources，and the sewage tmatment is an important source of methane in China that has not been measure．Sewage in China is often treated in cesspools，which are similar to the biogas pits．However，no methane is recovered from such cesspools．We estimate that the total flux of methane from such sources may be of the oidcr of 10 Tg/a．The total emissions of methane from sources in China are estmmted to be about 40±lOTg/a．     

Carbon dioxide release due to change in land usein China mainland

ＣａｒｂｏｎｄｉｏｘｉｄｅｒｅｌｅａｓｅｄｕｅｔｏｃｈａｎｇｅｉｎｌａｎｄｕｓｅｉｎＣｈｉｎａｍａｉｎｌａｎｄＷａｎｇＸｉａｏｋｅ；ＺｈｕａｎｇＹａｈｕｉ；ＦｅｎｇＺｏｎｇｗｅｉ（ＲｅｓｅａｒｃｈＣｅｎｔｅｒｆｏｒＥｃｏ－ＥｎｖｉｒｏｎｍｅｎｔａｌＳ...     

Environmental analysis of mercury in China

1　Ｄｅｔｅｒｍｉｎａｔｉｏｎｏｆｔｏｔａｌｍｅｒｃｕｒｙａｎｄｓｐｅｃｉａｔｉｏｎｏｆｍｅｒｃｕｒｙｃｏｍｐｏｕｎｄｓｉｎａｔｍｏｓｐｈｅｒｅ1.1　ＤｅｔｅｒｍｉｎａｔｉｏｎｏｆｔｏｔａｌｍｅｒｃｕｒｙＡｓａｍｐｌｉｎｇｔｒａｉｎｃｏｎｓｉｓｔｉｎｇｏｆａｆｉｌｔｅｒｔｏｒｅｔａｉｎ ｐａｒｔｉｃｕｌａｔｅｐｈａｓｅｍｅｒｃｕｒｙｆｏｌｌｏｗｅｄｂｙａｎａｂｓｏｒｂｅｎｔｔｒａｐｗｈｉｃｈｒｅｔａｉｎｓｔｏｔａｌｇａｓｅｏｕｓｍｅｒｃｕｒｙｉｓｕｓｅｄｆｏｒｄｅｔｅｒｍｉｎａｔｉｏｎｏｆｔｏｔａ…     

Adsorption and desorption of Cu(Ⅱ) and Pb(Ⅱ) in paddy soils cultivated for various years in the subtropical China

The adsorption and desorption of Cu(Ⅱ) and Pb(Ⅱ) on upland red soil,and paddy soils which were originated from the upland soil and cultivated for 8,15,35 and 85 years,were investigated using the batch method.The study showed that the organic matter content and cation exchange capacity (CEC) of the soils are important factors controlling the adsorption and desorption of Cu(Ⅱ) and Pb(Ⅱ).The 15-Year paddy soil had the highest adsorption capacity for Pb(Ⅱ),followed by the 35-Year paddy soil.Both the 35-Year paddy soil and 15-Year paddy soil adsorbed more Cu(Ⅱ) than the upland soil and other paddy soils.The 15-Year paddy soils exhibited the highest desorption percentage for both Cu(Ⅱ) and Pb(Ⅱ).These results are consistent with the trend for the CEC of the soils tested.The high soil CEC contributes not only to the adsorption of Cu(Ⅱ) and Pb(Ⅱ) but also to the electrostatic adsorption of the two heavy metals by the soils.Lower desorption percentages for Cu(Ⅱ) (36.7% to 42.2%) and Pb(Ⅱ) (50.4% to 57.9%) were observed for the 85-Year paddy soil.The highest content of organic matter in the soil was responsible for the low desorption percentages for the two metals because the formation of the complexes between the organic matter and the metals could increase the stability of the heavy metals in the soils.     

Perspective in development of environmental technology in China

１　ＩｎｃｒｅａｓｉｎｇｅｎｖｉｒｏｎｍｅｎｔａｌｐｒｏｂｌｅｍｓｃａｌｌｆｏｒｔｅｃｈｎｏｌｏｇｉｃａｌｓｏｌｕｔｉｏｎｓＷｉｔｈｔｈｅｒａｐｉｄｅｃｏｎｏｍｉｃｇｒｏｗｔｈｉｎｔｈｅｐａｓｔｔｗｏｄｅｃａｄｅｓ，ａｌｌｔｈｅｍａｊｏｒｅｎｖｉｒｏｎｍｅｎｔａｌｐｒｏｂｌｅｍｓｏｆｗｏｒｌｄｗｉｄｅｃｏｎｃｅｒｎｈａｖｅａｐｐｅａｒｅｄｉｎＣｈｉｎａｉｎｏｎｅｗａｙｏｒａｎｏｔｈｅｒ．Ｔｈｅｙａｒｅｍａｉｎｌｙｒｅｆｌｅｃｔｅｄｉｎｓｏｉｌｅｒｏｓｉｏｎ，ｄｅｓｅｒｔｉｆｉｃａｔｉｏｎ，ｂｉ…     

Sources of nitrous and nitric oxides in paddy soils：Nitrification and denitrification

Rice-paddies are regarded as one of the main agricultural sources of N 2O and NO emissions. To date, however, specific N2O and NO production pathways are poorly understood in paddy soils. ^15N-tracing experiments were carded out to investigate the processes responsible for N2O and NO production in two paddy soils with substantially different soil properties. Laboratory incubation experiments were carried out under aerobic conditions at moisture contents corresponding to 60% of water holding capacity. The relative importance of nitrification and denitrification to the flux of NaO was quantified by periodically measuring and comparing the enrichments of the N2O, NH~-N and NO3-N pools. The results showed that both N2O and NO emission rates in an alkaline paddy soil with clayey texture were substantially higher than those in a neutral paddy soil with silty loamy texture. In accordance with most published results, the ammonium N pool was the main source of N2O emission across the soil profiles of the two paddy soils, being responsible for 59.7% to 97.7% of total N2O emissions. The NO3-N pool of N2O emission was relatively less important under the given aerobic conditions. The rates of N2O emission from nitrification （N2On） among different soil layers were significantly different, which could be attributed to both the differences in gross N nitrification rates and to the ratios of nitrified N emitted as NzO among soil layers. Furthermore, NO fluxes were positively correlated with the changes in gross nitrification rates and the ratios of NO/N2O in the two paddy soils were always greater than one （from 1.26 to 6.47）. We therefore deduce that, similar to N2O, nitrification was also the dominant source of NO in the tested paddy soils at water contents below 60% water holding capacity.     

Determination of hexabromocyclododecanes in sediments from the Haihe River in China by an optimized HPLC–MS–MS method

Hexabromocyclododecanes(HBCDs),a new type of persistent organic pollutants widely used as brominated flame retardants,have attracted wide attention due to their increasing level and toxicity. A method based on high-performance liquid chromatography mass spectrometry(HPLC–MS–MS)in electrospray ionization mode has been developed by optimization of various parameters,which effectively improved the separation degree and responsive intensity of α-,β-and γ-HBCD isomers. The concentrations and distribution profiles of three HBCD isomers were investigated in sediments from the Haihe River in China.It was observed that the concentrations of HBCDs varied in the range of 0.4–58.82 ng/g,showing a decreasing trend along the flow direction,possibly due to attenuation and biodegradation along the flow direction of the Haihe River. The distribution profile of α-,β-,γ-HBCD was 7.91%–88.6%,0–91.47%,and 0.62%–42.83%,respectively. Interestingly,α-HBCD dominated in most sample sites. This was different from the distribution profile in commercial industrial products,which might be attributed to the inter-transformation and different degradation rates of the three HBCD isomers. The potential ecological risk of HBCDs in sediment was characterized under the two-tiered procedure of the European Medicines Evaluation Agency for environmental risk assessment. Although the HBCDs in the selected section of the Haihe River presented "no risk" in the sediment compartment,its risk in sediment cannot be neglected since sediment is one of the important sinks and reservoirs of pollutants.     

Environmental geochemical features of arsenic in soil in China

ＥｎｖｉｒｏｎｍｅｎｔａｌｇｅｏｃｈｅｍｉｃａｌｆｅａｔｕｒｅｓｏｆａｒｓｅｎｉｃｉｎｓｏｉｌｉｎＣｈｉｎａＷｅｎｇＨｕａｎｘｉｎ，ＬｉｕＹｕｎｆｅｎｇＤｅｐａｒｔｍｅｎｔｏｆＥａｒｔｈＳｃｉｅｎｃｅｓ，ＺｈｅｊｉａｎｇＵｎｉｖｅｒｓｉｔｙ，Ｈａｎｇ...     

Lead content of urban soils in China

ＬｅａｄｃｏｎｔｅｎｔｏｆｕｒｂａｎｓｏｉｌｓｉｎＣｈｉｎａＺｈａｎｇＸｕｅｌｉｎ（ＣｈａｎｇｃｈｕｎＩｎｓｔｉｔｕｔｅｏｆＧｅｏｇｒａｐｈｙ，ＣｈｉｎｅｓｅＡｃａｄｅｍｙｏｆＳｃｉｅｎｃｅｓ，Ｃｈａｎｇｃｈｕｎ１３００２１，Ｃｈｉｎａ）ＭｅｎｇＫｅ...     

Microanalysis of the aerosol collected over south-central New Mexico during the alive field experiment,May–December 1989

Thirty-eight size-segregated aerosol samples were collected in the lower troposphere over the high desert of south-central New Mexico, using cascade impactors mounted onboard two research aircraft. Four of these samples were collected in early May, sixteen in mid-July, and the remaining ones in December 1989, during three segments of the ALIVE field initiative. Analytical electron microscope analyses of aerosol deposits and individual particles from these samples were performed to physically and chemically characterize the major particulate species present in the aerosol.Air-mass trajectories arriving at the sampling area in the May program were quite different from those calculated for the July period. In general, the May trajectories showed strong westerly winds, while the July winds were weaker and southerly, consistently passing over or very near the border cities of El Paso, Texas, and Ciudad Juarez, Mexico. Aerosol samples collected during the May period were predominantly fine (0.1–0.5 μm dia.), liquid H₂SO₄ droplets. Samples from the July experiment were comprised mostly of fine, solid (NH₄)₂SO₄ or mostly neutralized sulfate particles. In both sampling periods, numerous other particle classes were observed, including many types with probable terrestrial or anthropogenic sources. The numbers of these particles, however, were small when compared with the sulfates. Composite particle types, including sulfate/crustal and sulfate/carbonaceous, were also found to be present. The major differences in aerosol composition between the May and July samples (i.e. the extensive neutralization of sulfates in the July samples) can be explained by considering the different aerosol transport pathways and the proximity of the July aerosol to the El Paso/Juarez urban plume.Winds during the December experiment were quite variable, and may have contributed to the widely varying aerosol compositions observed in these samples. When the aircraft sampled the El Paso/Juarez urban plume, high concentrations of carbonaceous particles were collected. These C-rich particles were of three distinct types, two of which showed combustion morphologies and the third an irregular morphology. Concurrent aethalometer measurements of aerosol black carbon concentration were well correlated (r = 0.83) with the total carbonaceous particle fraction in the aerosol samples. Carbonaceous particles were not observed in abundance in any of the May or July samples (even when the winds passed over El Paso), and we attribute the high concentrations in December to increased wintertime burning of wood, fossil fuels and other combustibles in the urban area.     

Climate effects of nuclear war in China

By utilizing simulations of climatic respponse to nuclear smoke, which were made by the Lawrence Livermore National Laboratory, USA, climate change in China induced by a large-scale nuclear war is analysed. Remarkable climate change in China following nuclear smoke injections is found. The surface air temperature decreases dramatically around all China, surface cooling is 13 ℃ averaging over whole China in July and maximum cooling is 23. 4 ℃ , 3 ℃ cooling in January and maximum 8℃ for the 150 Tg smoke injection (equivalent to the base-line nuclear war). However, the change in temperature is unhomogeneous, implying that the rise in temperature happens over some parts of China. An averaging precipitation decrease in many of months of the experimental year. The precipitation defect is dependent on a scale of nuclear war, the deduction is 1.8mm/day averaging over China in July in the 150 Tg smoke injection, and 0.1 mm/d in January. Nevertheless, the precipitation enhancement in a few months over some re