混养鱼塘水中磷含量及表层沉积物中磷赋存形态的初步探究

为更好地揭示养殖系统的磷收支和污染程度,以上海郊区3口团头鲂(Megalobrama amblycephala)混养鱼塘即池塘A、B、C以及水源D为研究对象,定期测定养殖期间水体中总磷(TP)、活性磷酸盐(PO4-P)以及沉积物中总磷的含量,并探究沉积物中不同形态磷,包括交换态磷(Ex-P)、铝结合磷(Al-P)、铁结合磷(Fe-P)、闭蓄态磷(Oc-P)、原生碎屑磷(De-P)、钙结合磷(Ca-P)和有机磷(Or-P)的分布变化特征。试验发现,该养殖场水源水TP(0.17±0.06)mg·L-1及PO4-P(0.11±0.06)mg·L-1含量一直维持在稳定的较低水平,养殖生产导致池塘A、B、C水中TP大大增加,已超过地表水Ⅲ类标准和淡水养殖池塘排放标准(Ⅱ类)。养殖池塘及水源沉积物中TP浓度分别是(0.69±0.04)、(0.70±0.07)、(0.68±0.09)、(0.79±0.13)mg·g-1,池塘表层沉积物中TP含量变化不大,而水源沉积物TP变化波动性明显。池塘表层沉积物中磷主要由Fe-P(18.03±6.01)%、Oc-P(22.82±5.34)%、Ca-P(27.48±8.15)%和Or-P(20.29±6.60)%组成,Ex-P(3.07±1.06)%、Al-P(7.62±3.11)%,尤其是De-P(0.69±0.35)%仅占很少部分。研究结果提示养殖塘内源污染相对较轻,人为投饵施肥等磷输入行为对沉积物中各形态磷的含量影响较大。研究结果有利于阐明养殖系统中磷的变动规律,从而指导养殖池塘环境调控并促进养殖技术更新。

Examination of Phosphorus Contents and Its Forms in the Surficial Sediments of Polyculture Fish Ponds

To reveal situations of phosphorus balance and contamination in aquatic eco-system,three Megalobrama amblycephala polyculture ponds marked A,B,C and their water source D(as control)were selected in the suburb of Shanghai.We routinely monitored the total phosphorus(TP)and reactive phosphorus(PO4-P)concentrations in the water,and contents of TP and various phosphorus forms in the surficial sediments of the fish ponds,including the easily exchangeable phosphorus(Ex-P),aluminum-bound phosphorus(Al-P),iron-bound phosphorus(Fe-P),occluded phosphorus(Oc-P),detrital phosphorus(De-P),calcium-bound phosphorus(Ca-P)and organic phosphorus(OrP).The results showed that TP and PO4-P contents in the source water of this farm were stable at a low level(0.17±0.06)mg·L-1 and(0.11± 0.06)mg·L-1],while TP contents in the farming ponds water significantly increased,in excess of the limit in the《Environmental quality standards for surface water》(GB 3838—2002 Grade Ⅲ)and the《Requirment for Water Discharge from Freshwater Acquaculture Pond》(SC/T 9101— 2007 Grade Ⅱ).TP contents in the sediments of these four sampling points were(0.69±0.04)mg·g-1(,0.70±0.07)mg·g-1(,0.68±0.09) mg·g-1 and(0.79±0.13)mg·g-1 respectively.Although there were no significant variation about the TP contents in the sediments of the ponds,significant variation existed in the sediment of source water sediments.TP in the surficial sediments of polyculture fish ponds consistedof Fe-P(18.03±6.01)%,Oc-P(22.82±5.34)%,Ca-P(27.48±8.15)%,and Or-P(20.29±6.60)%,and a relatively small part Ex-P(3.07± 1.06)%,Al-P(7.62±3.11)%,and De-P(0.69±0.35)%.These results suggest that phosphorus input from feed and fertilization greatly affects the phosphorus forms in sediment while the internal pollution of pond sediments is weak.This study will help us to clarify the law of phosphorus changes in aquaculture system,to promote appropriate aquaculture technology,and improve pond water quality.