1. Freshwater chemistry across the circumpolar region was characterised using a pan-Arctic data set from 1,032 lake and 482 river stations. Temporal trends were estimated for Early (1970–1985), Middle (1986–2000), and Late (2001–2015) periods. Spatial patterns were assessed using data collected since 2001.
2. Alkalinity, pH, conductivity, sulfate, chloride, sodium, calcium, and magnesium (major ions) were generally higher in the northern-most Arctic regions than in the Near Arctic (southern-most) region. In particular, spatial patterns in pH, alkalinity, calcium, and magnesium appeared to reflect underlying geology, with more alkaline waters in the High Arctic and Sub Arctic, where sedimentary bedrock dominated.
3. Carbon and nutrients displayed latitudinal trends, with lower levels of dissolved organic carbon (DOC), total nitrogen, and (to a lesser extent) total phosphorus (TP) in the High and Low Arctic than at lower latitudes. Significantly higher nutrient levels were observed in systems impacted by permafrost thaw slumps.
4. Bulk temporal trends indicated that TP was higher during the Late period in the High Arctic, whereas it was lower in the Near Arctic. In contrast, DOC and total nitrogen were both lower during the Late period in the High Arctic sites. Major ion concentrations were higher in the Near, Sub, and Low Arctic during the Late period, but the opposite bulk trend was found in the High Arctic.
5. Significant pan-Arctic temporal trends were detected for all variables, with the most prevalent being negative TP trends in the Near and Sub Arctic, and positive trends in the High and Low Arctic (mean trends ranged from +0.57%/year in the High/Low Arctic to −2.2%/year in the Near Arctic), indicating widespread nutrient enrichment at higher latitudes and oligotrophication at lower latitudes.
6. The divergent P trends across regions may be explained by changes in deposition and climate, causing decreased catchment transport of P in the south (e.g. increased soil binding and trapping in terrestrial vegetation) and increased P availability in the north (deepening of the active layer of the permafrost and soil/sediment sloughing). Other changes in concentrations of major ions and DOC were consistent with projected effects of ongoing climate change. Given the ongoing warming across the Arctic, these region-specific changes are likely to have even greater effects on Arctic water quality, biota, ecosystem function and services, and human well-being in the future.

中文翻译：

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北极淡水化学的时空变化——反映气候引起的景观变化和生物多样性模板的变化

1. 使用来自 1,032 个湖泊和 482 个河流站的泛北极数据集对整个极地地区的淡水化学进行了表征。估计了早期（1970-1985）、中期（1986-2000）和晚期（2001-2015）时期的时间趋势。使用自 2001 年以来收集的数据评估空间模式。
2. 北极最北部地区的碱度、pH、电导率、硫酸盐、氯化物、钠、钙和镁（主要离子）通常高于近北极（最南部）地区。特别是，pH、碱度、钙和镁的空间模式似乎反映了潜在的地质情况，在以沉积基岩为主的北极高地和亚北极地区，碱性水域更多。
3. 碳和营养物质呈现出纬度趋势，与低纬度地区相比，高北极和低北极地区的溶解有机碳 (DOC)、总氮和（在较小程度上）总磷 (TP) 水平较低。在受永久冻土融化坍塌影响的系统中观察到显着更高的营养水平。
4. 整体时间趋势表明，在北极高地晚期，TP较高，而在近北极较低。相比之下，高北极地区晚期的 DOC 和总氮均较低。晚期近北极、亚北极和低北极的主要离子浓度较高，但在高北极发现相反的体积趋势。
5. 所有变量都检测到了显着的泛北极时间趋势，其中最普遍的是近北极和亚北极的负 TP 趋势，以及高北极和低北极的正趋势（平均趋势范围为 +0.57%/年低北极至近北极地区每年-2.2%），表明高纬度地区普遍存在养分富集，而低纬度地区则存在贫营养化。
6. 不同地区磷的不同趋势可能是由于沉积和气候的变化，导致南部磷的集水输送减少（例如增加土壤结合和陆地植被捕获）和增加北部的磷可用性（加深活性层永久冻土和土壤/沉积物脱落）。主要离子和 DOC 浓度的其他变化与持续气候变化的预计影响一致。鉴于整个北极地区持续变暖，这些特定区域的变化可能会对北极水质、生物群、生态系统功能和服务以及未来的人类福祉产生更大的影响。