The present study evaluates the distribution of metals over the last 100 years in the Oualidia lagoon by examining their concentrations in the sediment cores. The samples were analyzed by instrumental neutron activation analysis and inductively coupled plasma mass spectrometry. Activities of Pb,Ra, and Cs were determined by gamma-ray spectrometry for establishing the age-depth relationships throughout the sediment cores by applying conventional models. The results indicated that the study area is contaminated by As and Cd revealing a detectable anthropogenic input of occurring metals as a consequence of the continuous development of human activities around the lagoon since 1950. The enrichment factor calculated for each layer of the three cores revealed that the studied sediments present no enrichment by Pb, K, and Mn; minor enrichment by Zn, Cr, Co, Cu, V, and Ni; and a moderately to severe enrichment by As and Cd. The pollution load index values increase from the bottom to the top of cores, and ranged from 0.9 to 2.8, which indicates levels of pollutants ranging from background to relatively high concentrations in the investigated sediments.

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PurposeMorocco is facing climate change, as shown by national studies conducted to date. The purpose of our research work is, on one hand, to develop an experimental protocol; simulating the Moroccan climate, through exposing concretes to accelerated aging in different cycles of temperature variation (+5 to +40 C°) and humidity (60–98% RH) and on another hand, to determine the effect of exposure to temperature and humidity variation cycles on the durability indicators (of concrete [with and without thermal cure]).Design/methodology/approachFor this purpose, three classes of concrete were studied (C35, C40 and C55). Each class of concrete was considered first with no addition of silica fume (SF) and then with a 10% addition of SF. The concrete samples underwent three types of conditioning before performing the tests. The control concretes (Ct) were demoulated after 24 h and stored under stable temperature and humidity conditions (20 ± 2 °C and 80% ± 5 RH). Treated concretes (CV) demouled after 24 h and exposed to 300 cycles of 12 h of temperature and moisture variation in a climate chamber. And finally, concretes that have undergone a heat cure (CTV) for 5 h at 90 °C, were then removed from the mold and exposed to temperature and moisture variations cycles identical to treated concrete (CV).FindingsThe results obtained show that aging accelerated by temperature change, and humidity improves durability indicators compared to Ct. Concretes that have undergone a thermal cure, followed by accelerated aging, show an improvement in durability indicators between 50 and 200 cycles, but the performance of concrete decreases after 200 exposure cycles. The addition of SF plays a beneficial role in the durability of concrete in the three exposure environments.Originality/valueThe originality of the work is, to develop an experimental protocol, simulating the Moroccan climate, through exposing concretes to accelerated aging in different cycles of temperature variation (+5 to +40 C°) and humidity (60–98% RH) and on another hand, to determine the effect of exposure to temperature and humidity variation cycles on the durability indicators of conventional concrete (with and without thermal cure).

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