Urmia Lake is a large-scale hypersaline lake that experienced a drastic water-level fall due to natural and anthropogenic forces during the last two decades. Construction of a causeway in the central part of the lake after 1989 has divided the lake into northern and southern parts and caused an extreme change of the lake hydrochemical system. Precipitation of evaporite minerals as crust on the lake floor was caused by the combination of lake level fall and increasing water salinity. However, some parameters controlling rates of salt deposition and dissolution and temporal and spatial variation in salt thickness in Lake Urmia are poorly understood. This study reviews 90 sediment cores from various parts of the lake to put forward a better understanding of the salt depositional system and salt thickness variations in the basin for the last 40 years (1977–2017). Our results indicate that the sedimentary system of Urmia Lake changed rapidly during the last two decades from a permanent hypersaline lake with predominantly fast terrigenous–biochemical sedimentation to a seasonally changing playa sedimentary environment with predominance of evaporite minerals. These changes are responsible for rapid salt deposition that generated a salt-crust with a maximum thickness of 2.95 m overlying Holocene terrigenous sediments. The salt-crust thickness and the water depth have a positive correlation for water depth greater than 1 meter, which means that salt-crust thickness increases where water depth increases. While the thickness of shallow deposits are affected by fresh-water dissolution. In addition, the average salt precipitation rate in the northern and the southern parts of the lake is 466 and 266 times higher, respectively, than the average (0.3 mm/y) sedimentation rate before the lake shrinkage. Similar to other large hypersaline lakes such as the Great Salt Lake (USA) and the Aral Sea (Central Asia), the manmade intervention at Urmia Lake (damming of the catchment, extension of agricultural fields, and causeway construction in the middle part of the lake) threatens its further hydrologic existence.

中文翻译：

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乌尔米亚湖（伊朗西北部）的沉积环境和盐厚度变化：沉积物核心研究的真知灼见

Urmia湖是大型的高盐湖，在过去的二十年中，由于自然和人为因素，水位急剧下降。1989年以后，在湖中部修建了一条堤道，将湖分为北部和南部，并导致了湖水化学系统的极端变化。湖面水位下降和水盐度增加共同导致湖底蒸发岩矿物沉淀为地壳。然而，对控制盐沉积和溶解速率以及乌尔米亚湖盐厚度的时空变化的一些参数了解甚少。这项研究回顾了湖中各个部分的90个沉积物核心，对过去40年（1977-2017年）流域的盐分沉积系统和盐分厚度变化提出了更好的理解。我们的结果表明，在最近的二十年中，Urmia湖的沉积系统发生了快速变化，从永久的高盐度湖（主要是陆源生化快速沉积）到季节性变化的普拉亚沉积环境（主要是蒸发矿物质）。这些变化导致盐快速沉积，形成了全新世陆源沉积物上最大厚度为2.95 m的盐结壳。对于大于1米的水深，盐壳厚度与水深呈正相关，这意味着在水深增加的地方，盐壳厚度会增加。浅层沉积物的厚度受淡水溶解的影响。此外，该湖北部和南部的平均盐分沉淀率分别比该湖收缩前的平均沉淀率（0.3 mm / y）高466倍和266倍。与其他大型高盐湖如美国的大盐湖和咸海（中亚）类似，乌尔米亚湖的人为干预（集水区的溃坝，农田的扩建和中部堤道的建设）湖）威胁其进一步的水文生存。该湖北部和南部的平均盐分沉淀率分别比湖泊收缩前的平均沉淀速率（0.3 mm / y）高466倍和266倍。与其他大型高盐湖如美国的大盐湖和咸海（中亚）类似，乌尔米亚湖的人为干预（集水区的溃坝，农田的扩建和中部堤道的建设）湖）威胁其进一步的水文生存。该湖北部和南部的平均盐分沉淀率分别比湖泊收缩前的平均沉淀速率（0.3 mm / y）高466倍和266倍。与其他大型高盐湖如美国的大盐湖和咸海（中亚）类似，乌尔米亚湖的人为干预（集水区的溃坝，农田的扩建和中部堤道的建设）湖）威胁其进一步的水文生存。