Pant H K, Reddy K R
Soil and Water Science Department, IFAS, University of Florida, 106 Newell Hall, P.O. Box 110510, Gainesville, FL 32611-0510, USA.
Water Res. 2003 Mar;37(5):965-72. doi: 10.1016/s0043-1354(02)00474-8.
Wetland construction on agricultural or dairy lands could result in solubilization of phosphorus (P) stored in soils and release to the water column. To study the extent of P flux during the start-up period of a constructed wetland, intact soil-cores from areas used for dairy operations, in Okeechobee, Florida, USA were obtained and flooded with adjacent creek water. In the first 28-day hydraulic-retention period, P concentration in the water column increased several fold due to rapid P flux from impacted soils. A continuous decrease in P flux to the water column until the third hydraulic retention cycle (initial influent P concentration 0.2 mgL(-1)), and constant thereafter suggest that the effect of initial influent P upon long-term P flux from soils could be limited. The initial release maybe due to high concentration of labile P in impacted soils; however, slow dissolution of relatively stable P pools could maintain a steady flux, well above of that observed from non-impacted soils. Water soluble P along with double acid-extractable magnesium explained 76% of the variability in cumulative P flux to the water column. Apparently, co-occurrence of active adsorption-desorption phenomena due to independent maintenance of equilibrium by individual P compounds regulates P dynamics of the water column. The results indicated that equilibrium P concentration of the water column of the wetland would be above 1.3 mgL(-1), which is well above the targeted P level in the water column of the Lake Okeechobee, one of the main water bodies in the area (0.04 mg PL(-1)). This suggests construction of wetlands in agricultural lands could result to substantial internal P loading. However, preventative measures including chemical amendments, establishment of vegetative communities or flushing the initially released P may potentially stabilize the system, and maintain P removal efficiency.
在农业用地或奶牛场土地上进行湿地建设可能会导致土壤中储存的磷（P）溶解并释放到水柱中。为了研究人工湿地启动期磷通量的程度，从美国佛罗里达州奥基乔比湖用于奶牛养殖的区域获取完整的土壤芯，并使其被相邻的溪水淹没。在最初的28天水力停留期内，由于受影响土壤中磷的快速通量，水柱中的磷浓度增加了几倍。直到第三个水力停留周期（初始进水磷浓度为0.2 mgL(-1)），进入水柱的磷通量持续下降，此后保持恒定，这表明初始进水磷对土壤长期磷通量的影响可能是有限的。初始释放可能是由于受影响土壤中不稳定磷的高浓度；然而，相对稳定的磷库的缓慢溶解可以维持稳定的通量，远高于未受影响土壤中观察到的通量。水溶性磷与双酸可提取镁共同解释了进入水柱的累积磷通量变化的76%。显然，由于单个磷化合物独立维持平衡而同时出现活跃的吸附 - 解吸现象，调节了水柱的磷动态。结果表明，湿地水柱的平衡磷浓度将高于1.3 mgL(-1)，这远高于该地区主要水体之一奥基乔比湖水柱的目标磷水平（0.04 mg PL(-1)）。这表明在农业土地上建设湿地可能会导致大量的内部磷负荷。然而，包括化学改良、建立植被群落或冲洗最初释放的磷在内的预防措施可能会稳定系统，并维持磷去除效率。
