Abstract Agriculture is one of most important economic activities that requires large amounts of water, which, in addition to changes in climate, presents a major impact on the water availability. Excess of salt and nutrient concentrations build up damages to soil such as reduced drainage and increase in anoxic conditions in the root zone, as well as decreasing productivity and usable farm lands. The objective of the present study was to evaluate the chemical vulnerability of an aquifer in arid conditions with a high level of extraction through the detection of risk zones and potential subregions of different risks. An evaluation of the quality of the groundwater was performed, as a reconnaissance prior to more detailed studies, in which samples of 30 wells were analyzed to determine physical-chemical parameters (recorded in situ), dissolved chemical species (UV–vis spectrophotometry), and elemental content (X-ray fluorescence spectrophotometry). Concentrations of TDS, as well as Ca, Mg, S, Cl, and As determined in the water under analysis exceeded the limit established for water for consumption and irrigation. It is suggests that the origin of the elemental composition is mainly due to the mineral composition of the aquifer sediments. The wells were classified in three groups located in different zones, based on: a) alkaline earth elements, b) halogens, c) dissolved ions. Water salinity is mainly composed by sulphates and, a lesser extent, by hydrochloric salts from leaching of evaporites. Furthermore, the highest chemical vulnerability are located from central to north zone, where the soils showed crop leaching requirement by above of threshold value for pecan crops, one of the major agricultural products of the valley. In conclusion, both the salinity and the high level of water extraction for agriculture, combined with the arid conditions, are provoking an increase in contents of some chemical species in soil of crops. The immediate consequences are related to a reduction in the agricultural production and, therefore, a decrease in the productive competitiveness.

中文翻译：

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在农业用途的干旱条件下重新勘测含水层的化学脆弱区域

摘要 农业是最重要的经济活动之一，需要大量的水，除气候变化外，这对水资源的可用性也有重大影响。过多的盐分和养分浓度会对土壤造成损害，例如排水减少和根区缺氧条件增加，以及生产力和可用农田的减少。本研究的目的是通过检测风险区域和不同风险的潜在子区域，评估含水层在高提取水平的干旱条件下的化学脆弱性。对地下水的质量进行了评估，作为更详细研究之前的勘察，其中分析了 30 口井的样品以确定物理化学参数（原位记录），溶解的化学物质（UV-vis 分光光度法）和元素含量（X 射线荧光分光光度法）。被分析水中测定的 TDS 以及 Ca、Mg、S、Cl 和 As 的浓度超过了为消费和灌溉水制定的限值。这表明元素组成的起源主要是由于含水层沉积物的矿物组成。井被分为位于不同区域的三组，基于：a) 碱土元素，b) 卤素，c) 溶解离子。水的盐度主要由硫酸盐组成，在较小程度上由蒸发岩浸出的盐酸盐组成。此外，最高的化学脆弱性位于从中部到北部的区域，那里的土壤表现出高于山核桃作物阈值的作物浸出要求，河谷主要农产品之一。总之，农业的盐度和高水平的水提取，再加上干旱条件，导致作物土壤中某些化学物质的含量增加。直接后果与农业生产的减少有关，因此与生产竞争力的下降有关。