Seasonal variation on chemical parameters of well water at Draa Lasfar region (Marrakech, Morocco) was studied. A total of 144 samples were collected between 2012 and 2013 and were analyzed for temperature (T°), pH, total hardness (TH), chemical oxygen demand (COD), nitrates, Cd, Pb, and Zn. Significant difference between seasons was observed for these parameters. Highest temperature (28.72±3.16) was recorded during summer. COD and Zn concentration was recorded maximum during summer (167.25±31.05 mg/l, 131.4±12.0 µg/l respectively). Highest nitrates (2.67±0.75 mg/l) concentrations were recorded during spring. Highest Pb (632.14±82.54 µg/l) and Cd (1.93±0.36 µg/l) concentrations were recorded during winter. Alternating seasons can be likened to small-scale climate change. Therefore, the impacts of this change on quality of water resources include particularly the modification of parameters values. The main drawn conclusion is that a degradation trend of well water quality in the context of climate change can lead to an increase of at-risk situations related to potential health impact.
TopIntroduction
Of all the natural resources, water is unarguably the most essential and precious. It is a universal solvent and as a solvent it provides the ionic balance and nutrients, which support all forms of life (Vanloon & Duffy, 2005). It is generally obtained from two principal natural sources; Surface water such as fresh water lakes, rivers, streams, and Groundwater such as borehole water and well water (Caroline & Wilfred, 2013).
In Morocco, the major source of water used to meet the domestic, agricultural and industrial needs is the ground water. The ground water is defined as water that is found underground in cracks and spaces in soil, sand and rocks. This source has two distinct functions; firstly, it is a significant source of both urban and rural population’s water supply and secondly it sustains many wetland ecosystems.
Unfortunately, industrialization and human activities have partially or totally turned our environment into dumping sites for waste materials. As a result, many water resources have been rendered polluted and hazardous to man and other living systems (Bakare et al., 2003).
Water is typically referred to as polluted when it is impaired by anthropogenic contaminants and either does not support a human use, such as drinking water, and/or undergoes a marked shift in its ability to support its constituent biotic communities, such as fish.
Deposition of heavy metals in groundwater from anthropogenic activities has been implicated for an increase in heavy metal concentration above recommended levels (Maine et al., 2004; Bako et al., 2008).
The term “heavy metal” is not altogether clearly defined, but in the case of water pollution, these are metals such as arsenic, cadmium, iron, cobalt, chromium, copper, manganese, mercury, molybdenum, nickel, lead, selenium, vanadium and zinc. While heavy metals do tend to have a high atomic mass, and so are heavy in that sense, toxicity seems to be a further defining factor as to what constitutes a heavy metal and what does not.
Heavy metals are important components of agro-allied products such as pesticides, herbicides, fertilizers; manufacturing and other synthetic products such as paints and batteries. Mining activities, industrial, municipal and domestic wastes have been reported to be important sources of heavy metal pollution to the groundwater (Mathews et al., 2013).
Excessive concentration of heavy metals in the groundwater is of great concern because of their non-biodegradability. Therefore, their persistence in the environment portends health hazard plants and animals and consequently trigger ecological imbalance in the ecosystem (Ekmekyapar et al., 2012).
Another concern that high concentrations of heavy metals raise is their ability to bioaccumulate across the food chain, with members that are high up the food chain having concentration of such metals several times higher than what is obtainable in the depart point of the contamination (groundwater) (Bako et al., 2009; Megateli et al., 2009).
In Morocco, Ground water was main source of water supply in most rural communities. It had good microbiological and biological properties in general as such required minimal treatment. Actually, A variety of human activities, notably industrial and mining process have been responsible for the wider diffusion of heavy metals into this type of water (Barkouch et al., 2007).
This study was carried out to determine the spatial and seasonal variations of heavy metal deposition in groundwater in a mining area near Marrakech city in Morocco in order to assess the extent of pollution generated by the mining activity and to identify the key mechanism responsible for this contamination and its relation to this mining activity.