A First Insight into the Influence of Land Cover on the Hydrochemical Properties of Spring Waters Across a Lowland Landscape

Land cover influences surface water quality, as it affects the mobilization, deposition, and migration of ions through the landscape. In recent years, a large number of studies concentrated on the impact of the catchment's land cover on the water quality properties of inland water bodies in various temporal and spatial scales. Such studies, usually conducted on streams with the use of numerous land cover datasets, as well as different types of metrics, were not applied so far in the case of spring waters. In fact, the possibility of explaining the physicochemical characteristics of spring waters by land cover properties seems to be limited, as their water chemical composition is driven mainly by geological factors, such as duration of water circulation within the soil-rock matrix and type of the dominant minerals, and simultaneously, sometimes groundwater flow paths could be complicated, particularly in karst areas. However, definitely more favorable conditions for such investigations exist across lowland, post-glacial landscapes, where recharge areas of porous aquifers are spatially extended and relatively uniform in terms of sediments. Thus, the current preliminary study attempted to evaluate the relationships between the land cover and the hydrochemical properties of Quaternary spring waters. Field measurements (SEC, pH, and water temperature) and sample collection were conducted in November 2024 across 35 springs located in Mazovian voivodeship, draining sandy aquifers and laying over impermeable clays and loams. The concentrations of major cations and anions (Ca²⁺, Mg²⁺, Na⁺, K⁺, HCO₃^-, SO₄^2-, Cl^-, F^-) and selected trace elements (being anthropopressure indicators) in spring waters were determined using ion chromatography and ICP-MS, respectively. A circular geometric approach (500 m and 250 m radius) was adopted to calculate the land cover type contribution across spring recharge areas. In such delineated areas, Sentinel 2 Global Land Cover and Topographic Objects Database (BDOT10k) datasets were used for land use quantification (as percentages of artificial, cultivated, and forested areas), while the Spearman rank correlation coefficient was used for linking the land cover with ion concentrations. The investigated spring waters differed in terms of TDS (from 67 to 2052 mg/L) and hydrochemical types (from simple HCO₃-Ca to complex Cl-SO₄-HCO₃-Ca-Na). In the case of both datasets, it was documented that the type of land cover near the spring niche could act as proxy of their water chemical composition. Increased SEC values and Cl^-, K⁺, and Na⁺ concentrations were significantly (p<0.05) related with the higher participation of artificial areas, whereas  concentrations of NO₃^- were positively linked with the share of cultivated areas. Significant positive relationships were also documented between artificial areas and selected trace elements, such as boron, chromium, nickel, copper, selenium, and arsenic, being indicators of municipal and industrial pollution. The results suggest that the land cover of spring recharge areas in a lowland landscape could affect local groundwater chemistry, however, further studies are needed using more complex land cover metrics, particularly on the seasonality of the influence.