N20 emissions from forest and grassland soils in northern China

Nitrous oxide(N₂O)is a major trace gas in the atmosphere．It plays an important rote in global warming and zone depleting．In this paper，we set up a install to determine the N₂O emission flux from forest and grassland soil．We observed an interesting phenomenon：in our sampling sites，the soil always acts as a source of N₂O，but sometimes it acts as a sink when the temperature is lower than 15℃．     

Distribution and accumulation of heavy metals in A vicennia marina communi ty in Shenzhen，China

This paper deals with the absorption，accumulation and distribution of several heavy metals in Avicennia marina community at Futian Nature Reserve in Shenzhen。China．The results showed that：(1)the contents of Cu，Ph，Zn，Cd，Cr，Ni and Mn in the topsoil(O---30cm in depth)were 38．3，28．7，11．4，0．136，7 97，25．0 and 537 μg/g respectively；(2)there were significant differences in the contents of heavy metals in different fractions of Avicennia marina，and the content ranges were 1．8—13．8 for Cu，0．4—3．51 for Pb；3．4—69．5 for Zn，0．013—0．295 for Cd，0．28—0．73 for Cr，0．43—7．65 for Ni and 25一1552 μg/g for Mn；(3)The enrichment coefficient (weighted mean) of the plants to topsoil was Cd>Mn>Zn>Cu>Ni=Cr>Pb；(4)the accumulation amounts of seven elements in standing biomass of this community were 53．70，19．27，187．89，0．72，6．06，20．76 and 1631．17 mg/m² for Cu，Pb，Zn，Cd，Cr，Ni and Mn respectively．The net retention amount in the community(1993)were 4．06，1．32，16．36，1．43，107．98 rag/(m²．a)for Cu，Pb，Zn，Ni and Mn，60．21 and 431．8Oμg／(m²．a)for Cd and Cr respectively；(5)the potential amounts of the elements which existed in the residues of soil surface in the community were 2．09，1．96，5．05，1．54 and 405．54 mg／m²for Cu，Pb，Zn，Ni and Mn，and which of Cd and Cr were 19．30 and 78．00 μg/m²，respectively．     

Trends and characteristics of total ozone’and vertical profile in Kunming and Beijing，China

This paper presents the trends of total ozone at Beijing and Kunming areas during the period of 1979 to 1989．The SBUV ozone vertical profile data and the periodic oscillation in upper ozone layers over Beijing area are also described．The results show that the variation of Beijing and Kunming per decade are about-5%and-1.5%．respectively．     

Measurement of nitrous oxide emission dynamics from soil

A simple laboratory device which simulates environmental factors that affect N₂O emission from soil has been constructed． It is convenient to use it to observe the N₂O emission dynamics from soil cores while simulating some factors such as different fertilizer sources，management，temperature．and chemical inhibitors，etc．The detect limit was 2．5mg N₂O-N m^{-2．s-1 with maxinlum error about 10%, so it could be used for agricultural soils It was found that fertilizer source，fertilizer management and native soil type were preliminarily important factors on N₂O emission fluxes in some of our experiments．}     

Simula tion experiment of pyritic wastestone wea thering

The relationships for the rate of the pyritic wastestone weathering and leaching amount，surface area of the wastestone weathering，oxidant in the weathering system and the acidity of weathering solution were simulated．Jt was found that，on the basis of the logarithmic relationship between releasing amount of sulfur and leaching amount，the weathering rate of sulfide in the pyritic wastestone was changed exponentially with leaching amount．The relationships between the rate and weathering surface area of the wastestone and the rate and oxidant were exponential．It was indicated that there was scarcely relationship between the rate and acidity of the weathering solution．     

Heavy metal pollution of aquatic sediments in the Le An River-P oyang Lake area

The sediment quality mapping of Cu．Zn．Pb and Cd in the<20μm fraction of surface sedi．ments ofthe Le An River·Poyang Lake area clearly proves that the mining activities ofDexing Copper Mine and nearby smaller Pb—Zn mines have already polluted the aquatic system to some extent．Although poilution indices of the Poyang Lake sediments are still close to background values，first results from sediment cores point to a definite trend of gradually increasing contamination．     

论生物多样性的价值

从经济学角度论述了生物多样性的价值 ,并从三方面论述了生物多样性受到的威胁可能会给人类带来的危害 ,从经济价值角度揭示了保护生物多样性的重要意义。     

单板计算机用于污水流量的自动计量

本文介绍由单板计算机作为潜入式电磁型污水流量的自动计量装置。它在程序控制下,能够完成A/D转换、计时、流量的运算和累计、显示时间和流量、定时打印时间(星期、小时)和累计流量值,超量程报警和量程变换等攻能。具有精度高、稳定可靠、能在无人值守的情况下,自动计量和记录等优点。由潜入式电磁流量计和本装置构成的污水测试系统于1984年12月末通过市科委组织的技术鉴定。到会专家一致认为整个系统达到国内先进水平。     

合成氨工艺气─空气体系静态爆炸的表观实验特性

合成氨工艺气─空气体系静态爆炸的表观实验特性青海大学丁锁根青海第一化肥厂胡德福合成氨工艺气体的主要成分为Ｈ２、Ｎ２、ＣＯ、ＣＯ２和ＣＨ４等组分。其中Ｈ２、ＣＯ、ＣＨ４属于可燃煤气体。当它们各自与空气以适当的比例混合，将组成爆炸性混合气，遇到链引发条件...