桉树人工林区水体泛黑机理研究进展

Review on the mechanism of blackwater in eucalyptus plantation

围绕桉树人工林区水体突发性泛黑的形成机理,参考国内外关于缺氧性黑水事件的主要研究成果,重点从桉树人工林区泛黑现象的表征,致黑物质特性及来源,水体突发性泛黑的驱动因素,模拟预测及适应性调控等5个方面,讨论了桉树林区水体泛黑机理的研究进展。研究认为,桉树人工林区的黑水是一种出现在林区洼地、溪流、水库等不同规模水体的颜色如墨的水,其致黑物质主要为桉树茎叶残体浸出液富含黑色溶解性有机碳(DOC)、单宁酸等,单宁酸与金属离子结合形成的黑色络合物,以及当水体缺氧时形成的黑色金属硫化物。气象条件骤变,水文情势突变,沉积物的累积与运移等因素驱动了水体泛黑:对受水温分层结构影响的大中型水库等深水水体而言,致黑物质累积在水体底层,当气温骤降,水温分层结构失稳,水体内部多种化学反应及物质的运移过程发生变化,此时水体变黑。水文情势突变时,以潜流形式进入水库的径流将林区大量DOC、植物残渣、泥沙携带进入水体,导致水体泛黑。沉积物中微生物分解及氮、磷等的释放加重了水体底部缺氧,为致黑物质形成创造了环境。为了更好地预测和调控黑水,建立黑水运移模拟模型及对黑水进行适应性调控也尤为重要。目前现有研究大多集中于小规模水体(如溪流、河道等),而对会发生分层现象的大规模水体(如深水湖库等)的黑水发生机理仍不完全明晰,流域层面上的黑水模拟与预测还需进一步研究,桉树人工林区水库泛黑机理研究是未来重要方向。

Ecological impact of Eucalyptus plantation is a key scientific topic of global concern,especially its deforestation and water safety problem.Present research findings have evolved around the black water mechanism,its characteristics and the source of the dark component.The driving factor of black water,its prediction and adaptive control have been analyzed in this study.Research has indicated that black water appeared in depressions,streams and reservoirs of different scale in the eucalyptus forest.This was mainly caused by dissolved organic carbon and tannic acid that was extracted from eucalyptus leaf.Black complex formed by the combination of tannic acid with metal ions,and ferrous metal sulfides formed when the water was oxygen deficient.Besides,black water formation was triggered by either a change in meteorological conditions,hydrological situation or sediment accumulation,and migration.For deep waters(large and medium-sized reservoirs),which are affected by thermal stratification,dark matter accumulated in the water bottom.The water’s thermal stratification structure lost its stability when the temperature dropped,hence allowed the mixing of the water along the column in the reservoir leading to various chemical reactions,then finally caused the appearing of black water.Additionally,when the hydrological regime suddenly changes,the flood water that flows into the reservoir in the form of underflow will bring large amounts of DOC,plant residue and sediment into the water,resulting in the black water.The decomposition of microorganisms and the release of nitrogen as well as phosphorus in sediments aggravated oxygen deficiency at the bottom of the water,and created an environment for the formation of black matter.To predict and control the black water,it is very important to establish a model to simulate the transportation and regulate the adaptability of it.Present research was focused on the small-scale water(such as streams,rivers,etc.),so the formation mechanism of large-scale water that results in stratification(such as deep lakes and reservoirs,etc.)is still not entirely clear.Therefore,further study on the simulation and prediction of black water at the basin level is needed.At last,the mechanism of reservoirs in eucalyptus forest area will be an important topic in the future.