Studies on the Situation of Soil Organic Carbon Storage in Croplands in Northeast of China

This paper aims to estimate the soil organic carbon （SOC） storage in Northeast of China, identify its balance situation and changing trends under current cropping systems, and finally put forward some strategies to keep the SOC in balance. A biogeochemical model （DNDC） for agro-ecosystem was employed to predict SOC dynamics in agricultural ecosystems at regional scale. Data on climate, soil properties, cropping systems, acreage, and management practices at county scale were collected from various sources and integrated into a GIS database to support the model runs at the regional scale. The model predicted results revealed that （1） Total SOC storage in agricultural lands in Heilongjiang, Jilin and Liaoning provinces in Northeast of China is about 1 243.48 × 10^6 t （0-30cm soil layer）, respectively occupying 58.4, 25.5 and 16.1%; （2） Under the current cultivation systems, SOC is in a situation of net loss with carbon losing at a high rate of 31.22 × 10^6 t a^-1 （respectively 59.3, 25.9 and 14.8% in Heilongjiang, Jilin and Liaoning provinces） and 2.05 t ha^-1 a^-1, the situation is more serious in Heilongjiang and Jilin provinces; and （3） Protective cultivations, such as manuring, returning more residue of crop to the field, adopting no-till, are very useful for the accumulation of SOC in these regions.

Mercury in coal and its emission by coal combustion in the Northeast China

This paper reports on the mercury content distribution in coals produced in the Northeast of China, and the east of Inner Mongolia, and transmission of mercury from coals into the burned products. The arithmetic average value of mercury content in coals is 0.158 mg/kg, and the mercury content shows considerable positive correlation with ashes in coals. The mercury content in fly ash is increased as the particle diameter of fly ash decrease. After combustion, 23.1—26.9 percent of mercury in coals enters fly ash,and 56.3—69.7 percent of mercury escapes into atmosphere. We estimated that the amount of mercury in raw coals produced in the Northeast of China and the east Inner Mongolia was 30.9 tons in the whole year and the amount emitted into atmosphere was 20 30 tons in 1990.

Bioreactor performance and microbial community dynamics in a production-scale biogas plant in northeastern China

In cold regions,heating is necessary to maintain the continuous and steady year-round operation of biogas fermentation.In this study,changes in the liquid composition,biogas production,and microbial diversity in heated-and unheated-phase samples were evaluated in a production-scale biogas plant that was fed continuously with cattle manure as a mono-substrate in Heilongjiang province in northeastern China.The volatile solid(VS)and volatile fatty acid(VFA)contents both gradually decreased in the heated and unheated fermentation processes.The chemical oxygen demand(COD)removal efficiency in the unheated phase sampled on June 15(s-6-15)and October 15(a-10-15)and in the heated phase sampled on January 15(w-1-15)was 63.35%,44.2%and 44.0%,respectively.The biogas production yields were in agreement with the results obtained for the VS and VFA contents and COD removal efficiency.The performance of the reactor in the heated phase was less efficient than that in the unheated phase,and the biogas production efficiency in June-August was higher than that in the other months.However,the CH4 content in the biogas remained similar all year.Moreover,ARDRA(Amplified Ribosomal DNA Restriction Analysis)was used to study the microbial community composition in the fermentation process.The results showed that the methanogenic archaeal consortium consisted mainly of members of the genera Methanomicrobiales and Methanosarcinales.In the heated phase,hydrogenotrophic methanogens represented the dominant methanogen in w-1-15 feedstock.After fermentation,the strict aceticlastic methanogen Methanosaeta became the dominant methanogen.In the unheated phase,the hydrogenotrophic methanogens and aceticlastic methanogens were equivalent in s-6-15 feedstock and effluent,and aceticlastic methanogens were dominant in both a-10-15 feedstock and effluent.Assessments of the bacteria diversity of the microbial communities revealed that the common strains in the feed and effluent of the three samples included the rumen bacteria,Bacteroides,Clostridium,Ruminococcaceae and Proteobacteria.