Impact of Herbicide Treatments on the Construction Materials in the Roman Wall of Lugo, Spain (UNESCO World Heritage Site)

Combined laboratory and field research examining the possible alterations caused by herbicide treatments applied to construction materials (schist some granite, bound with mortar) in Roman wall of Lugo (NW Spain), declared a World Heritage site UNESCO 2000, was performed three separate studies past 20 years. In summers 1998 1999, herbicides glyphosate, sulphosate glufosinate–ammonium, as well physical (infrared burning) were separately different areas wall. spring 2016, oxyfluorfen Goal Supreme® test areas. winter 2018, essential oils, Origanum vulgare L., Thymus zygis Loefl. ex vulgaris each Mineralogical modifications (determined X-ray diffraction analysis), visible changes, such colour appearance saline residues evaluated after treatments. 1998/9 trial, glyphosate both triggered changes vermiculite clay minerals schists, also kaolinite. None highly perceptible changes. The did not cause any mineralogical materials, but it generate an increase chloride, nitrate sulphate contents granite slight darkening this material. most recent study, only deleterious effect observed lightness reduction yellow component application L. oil granite.