杭州市多环芳烃的干、湿沉降

多环芳烃（PAHs）是一类典型的持久性有机物,在各种环境介质广泛存在。为了研究干湿沉降对空气中PAHs的去除,采集了杭州市6个干沉降尘土样品、9个湿沉降雨水样品、5个湿沉降雪样品和6个地表径流样品,用高效液相色谱法（HPLC）测定了其中15种多环芳烃的浓度水平,比较了这些介质中PAHs的分布特点。结果表明,降尘中15种PAHs的总平均质量分数为4323ng·g^-1;雨水、雪水和地表径流样品中15种PAHs的总平均质量浓度分别为558.4ng·L^-1、765.1ng·L^-1和576.3ng·L^-1。地表径流、雨水、雪水和干沉降尘土4种样品中,都以4环PAHs为主,其次为3环PAHs。降雪比降雨对PAHs的去除效果更好,地表径流中PAHs主要来自雨水。根据杭州市大气降尘通量和降雨量,估算了PAHs的干湿沉降通量。杭州市辖区大气中每年PAHs的干湿沉降通量分别为1419.1kg和2689.8kg,湿沉降是PAHs去除的主要方式,约为干沉降去除总量的2倍。     

湖滨带温室气体氧化亚氮(N2O)排放研究

利用不锈钢气体采集箱,在太湖梅梁湾湖区,沿水体至陆地方向对植被型和裸露型湖滨带进行温室气体N2O的原位排放观测。结果发现两种类型湖滨带N2O排放均显著高于临近的开阔水体,可以达到10~100倍,水位变幅区是湖滨带温室气体N2O排放的峰值区,是陆向和水向辐射区的5~10倍。在观测期间,N2O排放通量的范围为-159.2～1565.6μg·m-2·h-1,具有明显的时空梯度变化,时间上,9月份最高,随着气温的下降和芦苇的衰亡而逐渐减少,在1月份最低;空间上,自水向辐射区至陆向辐射区,先逐渐升高,在水位变幅区达到峰值,然后再降低。该结果初步说明了湖滨带是温室气体N2O的一个极其重要的排放源,而目前IPCC对水体N2O排放的估算可能存在很大的疏漏;同时也从一定程度上反映了湖滨带是湖泊脱氮的重要区域,其对缓解湖泊氮污染起到了举足轻重的作用。     

Atmospheric deposition of PCDD/Fs measured via automated and traditional samplers in Northern Taiwan

Most polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in the atmosphere are bound to particles which are suspended in the atmosphere, and eventually settle on soil, vegetation, water bodies or other receptors in the environment. Monitoring atmospheric deposition fluxes (dry/wet) is important in tracing the environmental fate and behavior of PCDD/Fs. PCDD/F depositions were collected via an automated PCDD/F ambient sampler and traditional cylindrical vessels, respectively, from April 2007 to February 2008. The automated PCDD/F ambient sampler used in this study can prevent both re-suspension and photo degradation of the PCDD/Fs collected and effectively separates the PCDD/F samples into dry and wet contributions. The results indicated that the ambient PCDD/F concentrations collected using the PS-1 sampler ranged from 0.02 pg I-TEQ/m³ to 0.16 pg I-TEQ/m³ in Northern Taiwan. The results also indicated that the PCDD/F deposition flux collected using the automated PCDD/F sampler (17.5 pg I-TEQ/m² d to 25.8 pg I-TEQ/m² d) was significantly higher than that sampled with the cylindrical vessels (2.0 pg I-TEQ/m² d to 9.9 pg I-TEQ/m² d). The difference was attributed to the fact that part of the PCDD/F depositions collected using the traditional cylindrical vessels had undergone photo degradation and evaporation. In addition, the wet deposition flux of PCDD/Fs (39.4 pg I-TEQ/m² rainy day to 228 pg I-TEQ/m² rainy day) observed in this study was significantly higher than the dry deposition flux (12.3 pg I-TEQ/m² sunny day to 16.7 pg I-TEQ/m² sunny day). These results demonstrated that wet deposition is the major PCDD/F removal mechanism in the atmosphere.     

麦季稻秆还田方式对后续稻季CH4排放的影响

通过田间试验研究了麦季4种稻秆还田方式（不还田、表面覆盖、均匀混施和原位焚烧）对后续稻季CH4排放的影响,以探讨稻．麦轮作系统中秸秆还田对稻田温室气体排放的后续效应。试验于2007年小麦播种期将4．8t·hm^-2水稻秸秆分别以不同方式还田（不还田处理除外）,利用静态箱／气相色谱法对2008年后续稻季CH4排放进行观测。结果表明,不同麦季稻秆还田方式显著影响后续稻季的CH4排放。与不施稻秆处理相比,表面覆盖和均匀混施处理后续稻季CH4排放量增加了75％和40％,且CH4排放量差异主要体现在水稻生长前期（0．60d）;原位焚烧处理CH4排放量与稻秆不还田处理相比无显著差异（P〉0．05）;与不施稻秆处理相比,均匀混施处理显著增加稻季开始前土壤全C质量分数6％和全N质量分数12％（P〈0．05）;各处理水稻（Oryza sativa L．）产量无显著差异（P〉0．05）;稻秆麦季均匀混施与表面覆盖相比能在一定程度上抑制后续稻季CH4排放．同时避免了秸秆焚烧导致的C、N、P等元素的大量损失,是较为合理的麦季稻秆还田方式。     

南亚热带针阔混交林土壤热通量研究

运用土壤热通量板、常规微气象观测系统等设施对鼎湖山针阔混交林的土壤热通量和微气象因子进行了系统研究,结果表明,不同热通量板测值之间的差异可达10%以上。在中小时间尺度(≤1月)上,土壤热通量板上方土壤贮热均不能忽略,否则所测算的表层土壤热通量会产生较大误差,甚至发生热通量传递方向逆转的情况。5cm深度处和表层土壤热通量的日变化均呈“S”形,且前者相位后移0.5～1h。旱季土壤为热源而雨季为热汇,表层土壤年总热通量为-0.44MJ·m-2,说明就全年尺度而言,土壤是热源。表层土壤热贮量月变动范围为-0.14~0.20MJ·m-2,是5cm深度处土壤热通量的-11.0%~1.3%。表层土壤热通量月总值占净辐射的比例变动范围为-12.0%~3.3%,由于能量平衡大多在较小时间尺度上进行比较,故必须准确考察土壤热通量的变化,否则会极大地影响能量平衡。在0.5h尺度上,表层土壤热通量与2.5h前的冠层净辐射回归方程相关性最好,达极显著水平,说明鼎湖山针阔混交林土壤热通量对冠层净辐射的反馈要延滞约2.5h。     

稻田甲烷排放的研究进展

稻田是甲烷的重要排放源之一。文章对稻田甲烷的最新研究进展作了较为详尽的综述,包括稻田甲烷排放的机理、规律;重点分析了影响稻田甲烷排放的因素以及控制稻田甲烷排放的措施。最后指出了今后的研究重点应以现有的田间数据为基础,建立稻田温室气体排放的综合模型,预测稻田温室气体排放变化。     

稻田氨挥发研究进展

就稻田氨挥发产生过程和机理、影响因素、测定方法以及减少稻田氨挥发的有效技术作一综合回顾；对稻田氨挥发研究中存在问题和今后研究的重点进行了讨论。     

陆地生态系统臭氧干沉降的观测和模拟研究进展

近地层臭氧(O³)会对植物的生长和产量均产生一定的负效应。由于人类活动引起的不断升高的近地层O³浓度已经威胁到世界粮食安全。O³主要以干沉降的方式沉降到陆地生态系统,所以需要定量确定陆地生态系统中O³通量、干沉降速率和不同沉降通道的沉降过程,预测其对植物的潜在影响。介绍了目前O³干沉降的主要观测方法及其模拟模型,从4个方面(O³通量和干沉降速率的季节变化、日变化、气象因子等对O³干沉降的影响、不同O³沉降通道的沉降过程)重点评述了不同陆地生态系统O³干沉降观测和模拟的研究进展现状,并对未来的研究工作进行了展望,以期为我国未来开展相关研究工作提供借鉴。     

Regional dynamics of persistent organic pollutants (POPs) in the Pearl River Delta, China: implications and perspectives

The mass transport budgets of 1,1,1-trichloro-2,2-bis(chlorophenyl)ethane (p,p′-DDT) and decabromodiphenyl ether (BDE-209) in the Pearl River Delta, South China were calculated based on previously collected data. Residual p,p′-DDT, mostly related to historical use, has largely settled into soil (780,000 kg), while the soil BDE-209 inventory (44,000 kg) is considerably smaller. Conversely, large amounts of BDE-209 currently used in numerous commercial products have resulted in a much higher atmospheric depositional flux of BDE-209 (28,100 kg/yr) relative to p,p′-DDT (310 kg/yr). The soil inventory of p,p′-DDT is predicted to decrease to half of its current value after 22 years, and the percent area containing soil p,p′-DDT at levels exceeding the effects range-medium (27 ng/g) will decrease from 40% to 20%. Finally, soil BDE-209 inventory will reach an equilibrium value of 940 tons in ∼60 years, when BDE-209 levels in 50% of soil will be above an equivalent risk guideline value (125 ng/g).     

重金属污染土壤微波玻璃化技术研究

采用微波技术对土壤中Cd进行玻璃化固定研究,考察了微波辐照功率、助熔剂硼砂和微波敏化剂活性炭对玻璃化效果的影响。结果表明:延长辐照时间和增大微波功率,土壤外观发生明显团聚结晶的玻璃化现象,Cd的固定率显著升高。微波(539 W)辐照5 min,Cd的固定率可达95%以上。硼砂可显著降低土样的熔融温度,从而缩短微波时间,降低能耗。添加活性炭显著提高Cd的固定率而粒径对Cd的固定率影响不显著。微波作用形成的玻璃体结构致密结实,Cd的浸出浓度满足国家标准限值,使得污染土壤资源化的实现具有一定的可行性。