滇池泥炭土制备生物炭及其理化性质研究

The potential application of biochars as soil amendments has attracted a great deal of research attention. One of the most attractive advantages of biochar is that it could sequester carbon and thus controls carbon cycling. This process is essential in regulating global climate change. The analysis of literature results indicated that during the production of biochars using common biomass, only a very small portion of carbon was stabilized. Most of the carbon was released as low-molecular weight volatile organic chemicals or was converted to biofuel. From this point of view, carbon sequestration during biochar production using biomass should be re-evaluated. Previous studies have indicated that the formation of organo-mineral complex could protect carbon element from degradation and thus could stabilize carbon. The applicant conducted a preliminary study and found that the thermally-treated sediment could sequester carbon element at much higher efficiency that biochars from biomass. The applicant also observed that sediment and peat collected around Dianchi Lake have very high organic matter content, reaching 60% of the dry mass. In addition, the farm area around Dianchi Lake is generally reclaimed on krasnozem, which is relatively infertile. The intense application of fertilizers and pesticides generated serious environmental problems, such as land retirement, groundwater contaminant, as well as surface water contaminant. Agricultural non-point source pollutant is also responsible to the water pollution of Dianchi Lake. The application of biochar in the farm field around Dianchi Lake could solve several problems. Thus, this study is proposed to study the practical potential of applying biochars originated from Dianchi sediment or peat as soil amendment in farm field around this area. Sediment from northern water body of Dianchi Lake and peat around this area will be collected. These solid particles will be thermally-treated at different temperatures. The resulted biochar-like samples will be characterized for their physicochemical properties. Importantly, the release of the organic and inorganic pollutants in the biochars will be investigated to reveal their potential risks during application. The interactions between biochars and various pollutants will also be studied regarding their sorption, desorption and leaching behaviors. This study will extend the source for biochar production and provide theoretical support for soil amelioration around Dianchi Lake.

生物炭在可持续环境中具有多方面优势，特别是其对碳的锁定是调节全球气候变化的重要途径，因此其特殊的环境效应吸引了广泛的研究兴趣。申请人关注到，用一般生物质制备生物炭的过程中，只有很少一部分碳在固体颗粒中被固定下来，其他的碳以生物柴油的形式产出。从这个意义上看，用一般生物质制备的生物炭对碳锁定的贡献有待进一步论证。申请人在前期工作中，观察到有机-无机复合体中，碳固定的效果较好，而且，对污染物的吸附能力较强，因此提出以有机质含量较高的泥炭土和沉积物来制备生物炭。本研究拟在滇池采集泥炭土和草海水域的沉积物，探讨用其制备生物炭的可行性及其理化特性，重点讨论有机-无机复合体的形成对生物炭制备过程中碳锁定的机制，对生物炭内源污染物的结合形态和释放行为进行系统探讨，并在模拟体系中探讨生物炭对外源污染物吸附、解吸、淋溶等行为的影响。本研究为生物炭的制备和应用提供新的思路，并为后续的红壤改良建立核心技术储备。

生物炭在不同领域良好的应用前景而受到广泛关注。生物炭能有效固定锁定大气中CO2，缓解全球温室效应；生物炭作为土壤改良剂能增加土壤肥力，且能减少污染物的迁移性和生物有效性等等。滇池是中国西南地区最大的淡水湖，对社会经济发展有着重要影响。然而，滇池的水质被评为劣V类水体，该地区大面积分布了泥炭，有机质含量高达50 % 以上，具有非常好的有机质应用前景。本项目研究着重于在不同热解温度下将这些高有机质含量的沉积物制备为生物炭，一方面探讨用沉积物制备的生物炭的可行性及制备出的生物炭的理化性质；另一方面研究所制备生物炭的环境影响与污染控制作用。首先，对滇池沉积物生物炭性质进行了研究，发现高有机碳含量的沉积物可用于制备成生物炭进行固碳，且相对外海沉积物，草海沉积物更适合制备成生物炭进行应用。其次，对沉积物生物炭的内源污染的研究表明，在热解过程中PAHs的总含量是大幅度下降的，因此，高温热解有利于减少生物炭中PAHs的总量。对滇池沉积物中Cd、Cu、Pb、Zn这四种重金属形态特征分析发现随着制备生物炭的温度增高，重金属倾向于转化为环境惰性的残渣晶格态，且吸附锁定重金属的效果越好。沉积物生物炭中多环芳烃和重金属的最大浓度低于土壤中的多环芳烃和重金属浓度极限，因此沉积物生物炭可安全的应用于土壤改良。最后，在生物炭与外源有机污染物相互作用的研究中，沉积物生物炭能高效地滞留有机污染物，对于降低有机污染物的迁移和风险有重要的环境意义。生物炭对外源重金属的吸附，发现沉积物生物炭比其他生物质制备的生物炭和天然吸附剂对重金属的吸附作用更强，因而滇池沉积物生物炭对重金属污染物的固定也有一定的作用。总之，沉积物生物炭的内源污染物的环境风险在可接受范围内，同时还能降低外源污染物的迁移。研究期间课题组发表的SCI论文7篇，中文核心论文3篇，并参加了1次国际学术会议。在本项目基金的资助下，共培养研究生9名。其中博士研究生2名，硕士研究生7名。