National Marine Science Centre, Southern Cross University, Coffs Harbour, NSW, 2450, Australia.
Coffs Harbour City Council, Coffs Harbour, NSW, 2450, Australia.
Environ Pollut. 2018 Dec;243(Pt B):1036-1046. doi: 10.1016/j.envpol.2018.08.074. Epub 2018 Sep 5.
Nitrogen runoff from fertiliser intensive land uses has become an issue worldwide, contributing to algal blooms, hypoxic waters and aquatic biodiversity losses. This study assessed potential nutrient pollution from blueberry farms in subtropical Australia and examines whether nutrient loads were driven by groundwater discharge and/or surface water runoff. Streams downstream of eight blueberry farms were compared to eight nearby control sites without any blueberry activity. In the 90 day sample period, there were three rain events >90 mm day that produced runoff sufficient to create flooding. Overall, the results revealed a clear link between blueberry farming and nitrogen runoff in headwater streams. While NO (nitrate + nitrite) was the dominant nitrogen species downstream of blueberry farms, dissolved organic nitrogen (DON) was the dominant species in control sites. The concentrations and loads of NO were one order of magnitude lower in the eight non-blueberry (6.3 ± 2.0 μmol L; 1.6 ± 1.2 kg N-NO ha yr) than the eight blueberry (56.9 ± 14.2 μmol L; 21.8 ± 8.0 kg N-NO ha yr) sites. NO concentrations and loads were highest following rain events. Radon (Rn, a natural groundwater tracer) observations and low nitrogen concentration in groundwater samples further suggest that surface runoff dominates the delivery of nitrogen to the creeks investigated. NO concentrations and loads in creeks correlated with blueberry farm density. At >15% of blueberry land use in a catchment, there was a detectable influence in NO concentrations and loads in the headwater streams. Assuming that our load estimates can be up-scaled to annual nitrogen creek exports, and that local farmers use the recommended amount of fertiliser (121 kg N ha yr), between 18 and 25% of the used fertiliser was lost to the creeks. This implies that there are opportunities for decreasing the use of fertilisers in this catchment and managing any nitrogen that escapes to the creeks.
施肥强度大的土地利用导致氮素径流成为全球性问题，造成藻类大量繁殖、缺氧水域和水生生物多样性丧失。本研究评估了亚热带澳大利亚蓝莓种植场的潜在养分污染，并研究了养分负荷是由地下水排放和/或地表水径流驱动的。对 8 个蓝莓农场下游的溪流与 8 个附近没有蓝莓活动的对照点进行了比较。在 90 天的采样期内，有 3 次降雨事件大于 90 毫米/天，产生了足以造成洪泛的径流量。总的来说，研究结果表明蓝莓种植与上游溪流的氮径流之间存在明显联系。虽然硝酸盐+亚硝酸盐（NO）是蓝莓农场下游的主要氮素形态，但溶解有机氮（DON）是对照点的主要氮素形态。在 8 个非蓝莓（6.3±2.0 μmol/L；1.6±1.2 kg N-NO ha yr）农场中，NO 的浓度和负荷比 8 个蓝莓（56.9±14.2 μmol/L；21.8±8.0 kg N-NO ha yr）农场低一个数量级。NO 浓度和负荷在降雨事件后最高。氡（Rn，一种天然地下水示踪剂）观测和地下水样本中低氮浓度进一步表明，地表径流是向研究溪流输送氮的主要方式。溪流中 NO 浓度和负荷与蓝莓农场密度相关。在集水区中蓝莓用地超过 15%时，溪流中 NO 浓度和负荷可检测到影响。假设我们的负荷估算可以扩展到氮素年排放量，并且当地农民使用推荐的肥料用量（121 kg N ha yr），那么有 18%至 25%的肥料流失到溪流中。这意味着在这个集水区有减少肥料使用和管理任何逃逸到溪流中的氮的机会。
