Chemical recovery and browning of Nova Scotia surface waters in response to declining acid deposition,Environmental Science: Processes & Impacts

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Chemical recovery and browning of Nova Scotia surface waters in response to declining acid deposition
Environmental Science: Processes & Impacts ( IF 4.3 ) Pub Date : 2021-2-1 , DOI: 10.1039/d0em00425a
D. Redden _{1,

2,

3,

4,

5} , B. F. Trueman _{1,

2,

3,

4,

5} , D. W. Dunnington _{1,

2,

3,

4,

5} , L. E. Anderson _{1,

2,

3,

4,

5} , G. A. Gagnon _{1,

2,

3,

4,

5}

Affiliation

Declining emissions of sulfur and nitrogen have curtailed acid deposition across large areas of North America and Europe. This has allowed many lakes to recover from acidification, with decreases in sulfate, increases in pH, and increases in alkalinity. But reduced acid deposition has not always coincided with chemical lake recovery. Surface waters in Nova Scotia did not exhibit clear evidence of recovery as recently as 2007, due in part to increasing organic acidity and slow replenishment of base cations. In an updated assessment with data collected as recently as 2019, we analyze water chemistry representing 81 lakes and rivers and two precipitation monitoring stations over up to 41 years. We find that Nova Scotia surface waters are now exhibiting signs of chemical recovery. We estimated the linear decrease in precipitation sulfate and nitrate yield at up to 0.31 and 0.18 kg ha⁻¹ year⁻², respectively, and the linear increase in precipitation pH at up to 0.014 year⁻¹. Sulfate decreased in 60 of 62 lakes and 14 of 17 rivers (−0.0051 to −0.23 mg L⁻¹ year⁻¹), while pH increased in 55 of 64 lakes and 11 of 17 rivers (0.0015–0.072 year⁻¹). Apparent colour increased in 54 of 62 lakes and 13 of 17 rivers (0.0026–3.9 Pt–Co year⁻¹). We identified increasing aluminum trends in 46 of 61 lakes, and we show using size-exclusion chromatography that binding to organic and iron-based colloids may help to explain these trends. To the extent that increases in apparent colour are explained by chromophoric dissolved organic matter (DOM), they imply greater binding capacity for metals in surface waters, and greater capacity for DOM to stabilize metal (oxyhydr)oxide colloids.

中文翻译：

酸沉降减少，新斯科舍省地表水化学回收和褐变

硫和氮的排放量下降，限制了北美和欧洲大部分地区的酸沉降。这使许多湖泊从酸化中恢复，硫酸盐减少，pH值增加，碱度增加。但是减少的酸沉积并不总是与化学湖泊的恢复同时发生。直到2007年，新斯科舍省的地表水都没有显示出明显的恢复迹象，部分原因是有机酸度增加和碱性阳离子的补充缓慢。在最新的评估中，我们收集了截至2019年的数据，分析了长达41年的代表81个湖泊和河流以及两个降水监测站的水化学成分。我们发现新斯科舍省的地表水现在显示出化学回收的迹象。分别为-¹年⁻²和至0.014年^-1的降水pH线性增加。硫酸盐在62个湖泊中的60个和17条河流中的14个中减少（-0.0051至-0.23 mg L -¹年^-1），而pH在64个湖泊中的55个中和11条河流中的11个中增加（0.0015-0.072年-^1年）。62个湖泊中的54个湖泊和17条河流中的13个河流的表观颜色增加了（0.0026–3.9 Pt–Co年⁻¹）。我们在61个湖泊中的46个中发现了铝趋势的增加，并且我们使用尺寸排阻色谱法表明与有机和铁基胶体的结合可能有助于解释这些趋势。在某种程度上，表观颜色的增加是由发色溶解的有机物（DOM）解释的，它们暗示了对地表水中金属的更大结合能力，以及对DOM稳定金属（羟基氧化物）胶体的更大能力。

更新日期：2021-02-10

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