Foy R H, Lennox S D, Gibson C E
Agricultural and Environmental Science Division, Department of Agriculture and Rural Development, Newforge Lane, BT9 5PX, Northern Ireland, Belfast, UK.
Sci Total Environ. 2003 Jul 1;310(1-3):87-99. doi: 10.1016/s0048-9697(02)00625-3.
The scale and chronology of the phosphorus (P) enrichment of Lough Neagh, a large hypertrophic lake, was assessed using, as enrichment proxies, published palaeocological studies on diatoms and chironomid head capsules preserved in the lake sediments and, from 1974, monitoring data from the lake and its inflowing rivers. Enrichment commenced in 1880, and the scale and chronology of the diatom and chironomid records were similar up to 1960, but in the 1960s, chironomid accumulation rates increased dramatically, whereas diatom rates remained unchanged. From subsequent lake monitoring, the absence of a diatom response after 1960 was attributed to silica limitation so that P could be considered as the driver of increased diatom production only up to 1960. Using a coefficient for the demand for P by diatoms of 4 microg P mg SiO(2)(-1), it was calculated that the increased diatom production between 1881 and 1961 required an increase in lake P of 26 microg P l(-1). This value is close to the predicted increase of 22.5 microg P l(-1) in the lake caused by inputs of P from sewage treatment works and septic tanks. There was no evidence that diffuse source P contributed to enrichment over this period. Enrichment up to 1960 appears modest in comparison to subsequent years. From 1961 to 1974, lake P was estimated to have increased by 62 microg P l(-1), but only 25 microg P l(-1) of this increase was attributable to greater loadings of P from urban and septic tank sources. The enrichment response of chironomids at this time was also much greater than expected from a regression-derived relationship between urban P inputs and chironomid accumulation rates suggesting additional sources of P. The larger than expected increase in lake P was attributed to the onset of a significant internal loading of P and the commencement of an increase in diffuse source loadings of P. River monitoring has shown that diffuse P has increased steadily since 1974, more than counterbalancing a 40% reduction in urban P loadings that has taken place since 1980. By the end of the 20th century urban sources contributed only 19.7% of inflow P to Lough Neagh but lake P was 145 microg P l(-1) compared to an estimated concentration of 20 microg P l(-1) in 1881. Failure to control diffuse P sources has therefore been instrumental in the continued increase of lake P in Lough Neagh.
内伊湖是一个大型富营养化湖泊，利用湖泊沉积物中保存的硅藻和摇蚊头壳的已发表古生态学研究作为磷富集的代理指标，并结合自1974年以来该湖及其流入河流的监测数据，评估了该湖磷（P）富集的规模和时间顺序。富集始于1880年，直到1960年，硅藻和摇蚊记录的规模和时间顺序相似，但在20世纪60年代，摇蚊积累率急剧增加，而硅藻率保持不变。从随后的湖泊监测来看，1960年后硅藻没有反应被归因于硅限制，因此磷仅在1960年之前可被视为硅藻产量增加的驱动因素。使用硅藻对磷的需求系数为4微克磷/毫克二氧化硅（-1），计算得出1881年至1961年硅藻产量的增加需要湖泊磷增加26微克磷/升（-1）。这个值接近污水处理厂和化粪池输入磷导致湖泊中预测增加的22.5微克磷/升（-1）。没有证据表明在此期间分散源磷导致了富集。与随后几年相比，到1960年的富集似乎较为适度。从1961年到1974年，估计湖泊磷增加了62微克磷/升（-1），但其中只有25微克磷/升（-1）的增加归因于城市和化粪池源磷负荷的增加。此时摇蚊的富集反应也比根据城市磷输入与摇蚊积累率之间的回归关系预期的要大得多，这表明存在额外的磷源。湖泊磷的增加幅度大于预期，归因于磷的显著内部负荷的开始以及分散源磷负荷的增加。河流监测表明，自1974年以来，分散磷一直在稳步增加，超过了抵消自1980年以来城市磷负荷40%的减少。到20世纪末，城市源仅占流入内伊湖磷的19.7%，但湖泊磷为145微克磷/升（-1），而1881年估计浓度为20微克磷/升（-1）。因此，未能控制分散磷源在继续增加内伊湖的湖泊磷方面起到了作用。
