ABSTRACT There is concern about the deteriorating nutrient status of aquatic receiving environments in New Zealand. We estimated the amount by which current nitrogen (N) concentrations and loads exceed criteria in rivers, lakes and estuaries nationally. Criteria corresponded to national ‘bottom-line’ (i.e. minimal) environmental objectives set by government policy. Three metrics were evaluated: (1) degree of compliance describes the current TN loads in receiving environments relative to criteria; (2) catchment N status describes the acceptability of catchment N loads compared to criteria; and (3) excess load indicates the amount by which the N load exceeds the maximum allowable load (kg yr−1). Non-compliance with N criteria was broadly distributed nationally particularly in low-elevation catchments. Catchments with unacceptable N status constituted at least 31% of New Zealand’s land area, which corresponds to at least 43% of the country’s agricultural land. The national excess load was estimated to be at least 19.1 Gg yr−1. We are 97.5% confident that estimated excess loads exceed zero for nine of 15 regions and for the nation as a whole. The analyses provide a strategic assessment of where reductions in N emissions are required to achieve the minimal national objectives.

中文翻译：

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新西兰水生接收环境的氮负荷：与监管标准的比较

摘要 新西兰水生接收环境的营养状况恶化令人担忧。我们估计了全国河流、湖泊和河口当前氮 (N) 浓度和负荷超过标准的数量。标准对应于政府政策设定的国家“底线”（即最低限度）环境目标。评估了三个指标：(1) 合规程度描述了接收环境中与标准相关的当前 TN 负载；(2) 流域 N 状态描述了流域 N 载荷与标准相比的可接受性；(3) 超载表示N 载荷超过最大允许载荷(kg yr-1) 的量。不符合 N 标准的情况在全国范围内广泛分布，特别是在低海拔集水区。N 状态不可接受的集水区至少占新西兰土地面积的 31%，相当于该国农业用地的至少 43%。估计全国超负荷至少为 19.1 Gg yr−1。我们有 97.5% 的信心，15 个地区中的 9 个地区以及整个国家的估计超载超过零。这些分析提供了战略评估，需要在哪些方面减少氮排放才能实现最低限度的国家目标。