Petry J, Soulsby C, Malcolm I A, Youngson A E
Department of Geography and Environment, University of Aberdeen, Scotland, UK.
Sci Total Environ. 2002 Jul 22;294(1-3):95-110. doi: 10.1016/s0048-9697(02)00058-x.
Like many streams draining intensively farmed parts of lowland Scotland, water quality in the Newmills burn, Aberdeenshire, is characterized by relatively high nutrient levels; mean concentrations of NO3-N and NH3-N are 6.09 mg l(-1) and 0.28 mg l(-1), respectively, whilst average PO4-P concentrations reach 0.06 mg l(-1). Nutrient concentrations vary spatially and temporally with levels being highest under arable farming during the autumn and winter. Annual fluxes from the 14.5 km2 catchment are estimated at 25.67 and 1.26 kg ha(-1) a(-1) for NO3-N and NH3-N, respectively, and 0.26 kg ha(-1) a(-1) for PO4-P. Hydrological controls exert a strong influence on both nutrient concentrations and fluxes. Over short timescales nutrient concentrations and fluxes are greatest during storm events when P04-P and NH3-N are mobilized by overland flow in riparian areas, particularly where the soils have been compacted by livestock or farm machinery. Delivery of deeper soil water in subsurface storm flow, facilitated by agricultural under-drainage, provide large contributions of NO3-N on the recession limb of hydrological events. In contrast, groundwater inputs generally have lower NO3 concentrations implying that denitrification may be a pathway of N loss in the saturated zone. Approximately 75% of the N loss for the catchment occurs during the autumn and early winter when high flows dominate the hydrological regime. The close coupling of hydrological pathways and biogeochemical processes has major implications for catchment management strategies such as Nitrate Vulnerable Zones (NVZs) as it is likely that significant groundwater stores with long residence times will continue to cause N losses before water quality improvements become apparent.
与许多流经苏格兰低地集约化养殖地区的溪流一样，阿伯丁郡纽米尔斯河的水质特点是养分含量相对较高；硝酸盐氮（NO3-N）和氨氮（NH3-N）的平均浓度分别为6.09毫克/升和0.28毫克/升，而磷酸盐磷（PO4-P）的平均浓度达到0.06毫克/升。养分浓度在空间和时间上有所变化，在秋冬季节的耕地中含量最高。据估计，面积为14.5平方公里的集水区每年的硝酸盐氮和氨氮通量分别为25.67千克/公顷·年和1.26千克/公顷·年，磷酸盐磷通量为0.26千克/公顷·年。水文控制对养分浓度和通量都有很大影响。在短时间尺度上，暴雨事件期间养分浓度和通量最大，此时河岸地区的地表径流会带动磷酸盐磷和氨氮，特别是在土壤被牲畜或农业机械压实的地方。农业排水促进了地下暴雨径流中深层土壤水的输送，在水文事件的消退阶段，硝酸盐氮的贡献很大。相比之下，地下水输入的硝酸盐浓度通常较低，这意味着反硝化作用可能是饱和带氮损失的一条途径。该集水区约75%的氮损失发生在秋冬季节，此时高流量主导着水文状况。水文路径与生物地球化学过程的紧密耦合对集水区管理策略（如硝酸盐脆弱区（NVZs））具有重大影响，因为在水质改善显现之前，很可能长期存在的大量地下水库将继续导致氮损失。
