Environmental and geochemical characteristics of heavy metals in soils around the former mining area of zeïda (High Moulouya, Morocco)

The Zeïda mining center, closed in the mid-1980s, was once intensively exploited for lead concentrates. Throughout its activity, more than 12 Mt of tailings were generated and, to this day, they are still abandoned in the open air, exposed to weathering conditions without any rehabilitation. The purpose of the present study is to evaluate the environmental and geochemical characteristics of the soils, combining physicochemical, mineralogical, sequential, and kinetic extraction analyses, as well as the metallic spatial distribution and pollution indices of heavy metals (Pb, Cd, Cu, As, and Zn), levels, and risks. The results showed that the abandoned tailings had the highest concentrations of heavy metals, far exceeding their equivalents in the international and local guidelines. The soils spatial distribution maps showed that the levels of heavy metals decreased with distance from the tailings. Based on the pollution indices results, the soils located on and near the tailings are highly contaminated mainly by Pb. While downstream of the tailings, this contamination intensity decreased until becoming null. The sequential extraction results indicated that Pb, Zn, and Cd were primarily associated with the exchangeable fraction in tailings and soils. Therefore, they were more mobile and environmentally hazardous in the study area. The As was mainly associated with the residual fraction, and was thus immobile. Cu was more mobile in tailings as long as it was associated with the reducible fraction while it became immobile in the downstream soils. The kinetic extractions using EDTA and H2O revealed that the labile and less labile fractions were very significant in tailing for the majority of heavy metals. The methodology applied in this study may constitute a valuable tool to develop appropriate mine reclamation solution

Snowpack and groundwater recharge in the Atlas mountains: New evidence and key drivers

Study region: The Atlas Mountains of Morocco, specifically the High Oum Er-rbiaa (HOER) and Ourika catchments. Study focus: to identify the recharge processes within the semi-arid watersheds, in the Atlas Mountains, through monthly monitoring of snow, rainfall, surface water, and groundwater isotope signal, but also the usage of remote sensing data. New hydrological insights for the region: The spatial-temporal analysis of groundwater and precipitation isotopes reveals significant spatial heterogeneity, primarily influenced by the geological variations in each aquifer. Temporal variations indicate that direct recharge occurs in response to winter precipitation, whereas a delayed response is observed during the summer when snow replenishes groundwater towards the end of the melting season. The findings are further supported by the ''Gravity Recovery and Climate Experiment'' (GRACE) dataset, which demonstrates that high values of Total Water Storage (TWS) align with groundwater isotopes. This highlights the substantial groundwater abstraction rate between March and June to compensate for the lack of precipitation during this period. The analysis of isotope data indicates that 50% of groundwater recharge in the upstream Jurassic aquifer and 80% in the downstream Triassic-Paleozoic aquifers in the HOER catchment is sourced from snowmelt. Similarly, in the Ourika catchment, snowmelt contributes 30% and 50% of groundwater recharge in the upstream and downstream portions of the catchments respectively. This disparity is due to different melting rates across altitudinal ranges and variations in the lithology of each catchment

Environmental changes in the moroccan western rif mountains over the last 9,000 years

The aim of this study is to reconstruct the impact of past environmental changes in the Moroccan Rif mountainous ecosystems. We collected an 8.5 m sedimentary core in the western part of the Rif and analyzed its palynological content, micro-remains of fossil charcoal, particle size, and content of several chemical elements. The chronology of the record is based on ten 14C datings that indicate a continuous time span of 9,000 years. This multidisciplinary approach allowed us to reconstruct both the environmental evolution of the catchment area and the vegetation dynamics in the surrounding landscape. Besides the fossil record, we collected a series of surface samples along a transect running from Talassemtane National Park, where fir populations are currently protected, to the study site in order to determine the dispersal capacity of different plant taxa. Based on the modern observations, the fossil pollen data show that despite its closer range today to the study site than Cedrus atlantica (closest populations at ca. 20 km), Abies maroccana (populations at ca. 10 km) did not reach the studied site during the Holocene. At the same time, Cedrus atlantica was present and even dominated the landscape between 8,000 and 6,000 BP. After 6,000 BP, other species more tolerant to annual drought, such as evergreen oaks, expanded gradually. The early Holocene period was wet enough to promote a maximum expansion of cedar forest. The Atlas cedar disappears from the fossil record after 2,000 BP due to an increased human pressure. Particle size analysis and chemical elements are particularly relevant for reconstructing the landscape changes and for depicting the human impact. Their changes after 2,000 BP are well correlated with the forest cover decline

Contamination impact and human health risk in surface soils surrounding the abandoned mine of Zeïda, High Moulouya, Northeastern Morocco

International audienceThe study assesses the levels of 16 heavy metals (HMs) in soils around the Zeida mine to provide information on the extent of contamination, the ecological risk of these HMs in soils, and the health risk to the residents of the Zeida village. Total metal concentrations were determined by inductively coupled plasma-mass spectrometry (ICP-MS) for 20 sampling stations around the mining area. The average concentrations of HMs (mg/kg) in the study area were as follows: Ag (2.3), As (90.4), Ba (1605.1), Be (3.1), Co (11.2), Cr (57.6), Cu (33.9), Mn (499.6), Mo (6.1), Ni (23.4), Pb (1338.7), Sb (7.4), Se (1.3), Sn (11.3), Sr (596.5), and Zn (87.9). They were higher than those at the control sites. Twelve single and integrated ecological risk indices, namely Nemerow Pollution Index (PINemerow), Contamination degree (Cd), and Potential Ecological Risk (RI), were used and suggested that tailings and their nearby soils had a moderate to high contamination potential. Based on the US Environmental Protection Agency (USEPA), the carcinogenic risk, non-carcinogenic, hazard quotient (HQ), and hazard index (HI) were calculated with three routes: ingestion, inhalation, and dermal for children and adults. For both children and adults, HI for HMs was in the order: Mn > As > Co > Pb > 1 > other HMs. Mn, As, and Co were hazardous at 90% of soil sampling stations, while Pb was hazardous in tailings samples. The inhalation and dermal carcinogenic risks presented negligible to acceptable levels. The ingestion carcinogenic risk posed a significant issue for As, which tended to be serious for children at the majority of sampling sites

Fire activity in North West Africa during the last 30,000 cal years BP inferred from a charcoal record from Lake Ifrah (Middle atlas–Morocco): climatic implications

Paleofire activity in North Africa and its connections with past climatic changes still remains poorly documented. A new multiproxy analysis using mineralogy, geochemistry and microcharcoal data from Lake Ifrah (Middle Atlas, Morocco) provides new insights for better understanding paleofire occurrence from the Last Glacial Maximum to the present. The comparison between microcharcoal distribution and lacustrine multiproxy data highlights the variability of paleofire activity that is interpreted in term of long-term climate-driven changes. From 20,000 to 13,000 cal yr BP, the concentration in microcharcol was very low in connection with low fire activity and cold climate. The early to mid-Holocene (between 10,800 and 4,500 cal yr BP) marked a significant increase in microcharcoal abundance which likely testifies to regional emissions from forest fires. Such biomass burning events were associated to prolonged periods of drought, as inferred by synchronous abrupt decreases in surface runoff input records (e.g. organic matter, trace elements and magnetic susceptibility) and increases in carbonate content, calcite and Mg-calcite concentrations