*2.2.2.1 General information on agricultural pollutants*

In 2011, pollutant emissions from the different agricultural sources were firstly considered in the Chinese national wastewater pollutant inventory [6]. These pollutants are organic and/or inorganic coming from large quantities of agrochemicals products, such as insecticides, pesticides, herbicides, fungicides, fertilizers, and veterinary products. According to the Chinese Ministry of Environmental Protection (CMEP) [19], agricultural sources were found to release a total of 11.86 million tons of chemical oxygen demand (COD), accounting for 47.4% of the total COD wastewater from all sources in 2011. Meanwhile, a total of 0.83 million tons of NH4 + –N was also released from agricultural sources, which represents 31.8% of the total NH4 + –N wastewater from all sources. In general, agriculture is responsible for the release of four categories of water pollutants into the water environment as follows: (i) nutrients, (ii) pathogens, (iii) pesticides, and (iv) silts.

### *2.2.2.1.1 Nutrients*

Animal wastes and chemical fertilizers are applied to soil to provide the nitrogen, phosphorus, and trace elements necessary for crop growth. When applied, these fertilizers are either taken up by crops, remain in the soil, or enter the aquatic environments. Nitrogen (N) compounds can accumulate in soil crust and vadose zone for years. Furthermore, N in the presence of oxygen is transformed either to N gases, nitrite (NO2ˉ), or NO3ˉ. The fundamental paths of N cycle include nitrogen fixation, nitrification, denitrification, ammonification, volatilization, and atmospheric deposition. In addition to the natural complexity of the N cycle, N fluxes continue to be substantially modified by human activities especially by agriculture and burning of fossil fuels [20]. **Figure 3** shows a simplified N cycle diagram of nitrogen [21].

**43**

**Figure 3.**

*semiarid areas [21].*

*Pollution of Water Sources from Agricultural and Industrial Effluents: Special Attention…*

Nitratation NO2

+

Nitritation NH4

allows N to remain as NO3ˉ [11].

NO3ˉ is a naturally occurring ion in the nitrogen cycle that is the stable form of N for oxygenated systems; it is of prime concern on a global scale. Nitratation is the conversion of NO2ˉ by nitrite-oxidizing bacteria (e.g., *Nitrobacter* spp.) to NO3ˉ as in

The resulting NO3ˉ ion is stable in oxic conditions and can remain in the aquifer

+ 1 ⁄2 O2 → NO2

According to Rivett et al. [22] conditions under which denitrification will occur require the presence of NO3ˉ, denitrifying bacteria, oxygen concentrations (1–2 mg/L), electron donor, favorable conditions of temperature (25–35°C), pH (from 5.5 to 8.0), and other trace nutrients. Chemical and biological processes can further reduce NO2ˉ to various compounds or oxidize it to NO3ˉ. Due to its high water solubility [23], nitrate is regarded as one of the most widespread groundwater pollutant in the world, imposing a significant hazard to drinking water supplies and thus human health. The movement of NO3ˉ into water sources is related to concentration in the soil; this concentration is directly related to the total amount of N [16]. In addition and according to many researches, natural attenuation by denitrification is minimal in aquifers in semiarid areas which

*Simplified nitrogen cycle showing the principal anoxic and oxic paths influencing groundwater N in arid and* 

for a long time. NO3ˉ can be reduced by microbial action into NO2ˉ (also called nitritation) or other forms. Nitritation is the ammonia oxidation by ammonia-oxidizing bacteria (*Nitrosomonas* spp.) under aerobic conditions into NO2ˉ, according

<sup>−</sup> + 1 ⁄2 O2 → NO3

<sup>−</sup> (1)

<sup>−</sup> + 2 H<sup>+</sup> + H2O (2)

*DOI: http://dx.doi.org/10.5772/intechopen.86921*

*2.2.2.1.1.1 Nitrate*

Eq. (1):

to Eq. (2):

*Pollution of Water Sources from Agricultural and Industrial Effluents: Special Attention… DOI: http://dx.doi.org/10.5772/intechopen.86921*

#### *2.2.2.1.1.1 Nitrate*

*Water Chemistry*

degradation.

*2.2.2 Agricultural pollution*

concentrations in urban catchments [11, 12]. Urban runoff is the greatest cause of surface water pollutants in numerous parts of the world; according to Singh and Gupta [13], urbanization is second to agriculture as the primary cause of water

Agriculture is perchance the primeval contribution of man for the survival and prosperity of human kind [14]. Just as agriculture has comprehensively changed the face of the Earth, its impacts have equally profoundly re-wrought the nature of its waters (by degrading both surface and groundwater resources) [15]. These impacts implicate effects on water chemistry, alteration of the hydrological cycles, suspended loads from soil erosion, biocide leaching, and others. Indeed, agriculture can be both cause and victim of water pollution. Since 1990, the connection that exists between land and water use in the agricultural activity is recognized by the Food and Agriculture Organization (FAO) of the United Nations, by its clear requirement "appropriate steps must be taken to ensure that agricultural activities do not adversely affect water quality so that subsequent uses of water for different purposes are not impaired" [16]. The sources of agricultural pollutants could be "point" or "nonpoint" [11, 14, 17, 18]. In fact, water pollution caused by agricultural sources, as nonpoint sources, are hard to supervise and regulate, giving the diffusive nature of agricultural sources. According to Chen et al. [17] the nonpoint source water pollution from agriculture has exceeded that from industry and has

In 2011, pollutant emissions from the different agricultural sources were firstly

–N was also released from agricultural sources, which represents 31.8% of

for the release of four categories of water pollutants into the water environment as

Animal wastes and chemical fertilizers are applied to soil to provide the nitrogen, phosphorus, and trace elements necessary for crop growth. When applied, these fertilizers are either taken up by crops, remain in the soil, or enter the aquatic environments. Nitrogen (N) compounds can accumulate in soil crust and vadose zone for years. Furthermore, N in the presence of oxygen is transformed either to N gases, nitrite (NO2ˉ), or NO3ˉ. The fundamental paths of N cycle include nitrogen fixation, nitrification, denitrification, ammonification, volatilization, and atmospheric deposition. In addition to the natural complexity of the N cycle, N fluxes continue to be substantially modified by human activities especially by agriculture and burning of fossil fuels [20]. **Figure 3** shows a simplified N cycle diagram of

follows: (i) nutrients, (ii) pathogens, (iii) pesticides, and (iv) silts.

–N wastewater from all sources. In general, agriculture is responsible

considered in the Chinese national wastewater pollutant inventory [6]. These pollutants are organic and/or inorganic coming from large quantities of agrochemicals products, such as insecticides, pesticides, herbicides, fungicides, fertilizers, and veterinary products. According to the Chinese Ministry of Environmental Protection (CMEP) [19], agricultural sources were found to release a total of 11.86 million tons of chemical oxygen demand (COD), accounting for 47.4% of the total COD wastewater from all sources in 2011. Meanwhile, a total of 0.83 million tons

become the largest source of nonpoint pollution in China.

*2.2.2.1 General information on agricultural pollutants*

**42**

nitrogen [21].

of NH4 +

the total NH4

*2.2.2.1.1 Nutrients*

+

NO3ˉ is a naturally occurring ion in the nitrogen cycle that is the stable form of N for oxygenated systems; it is of prime concern on a global scale. Nitratation is the conversion of NO2ˉ by nitrite-oxidizing bacteria (e.g., *Nitrobacter* spp.) to NO3ˉ as in Eq. (1):

$$\text{Nitrotation NO}\_2^- + \text{I}\_2\text{O}\_2 \rightarrow \text{NO}\_3^- \tag{1}$$

The resulting NO3ˉ ion is stable in oxic conditions and can remain in the aquifer for a long time. NO3ˉ can be reduced by microbial action into NO2ˉ (also called nitritation) or other forms. Nitritation is the ammonia oxidation by ammonia-oxidizing bacteria (*Nitrosomonas* spp.) under aerobic conditions into NO2ˉ, according to Eq. (2):

$$\text{Nitritation } \text{NH}\_4^\* + \text{1}\_2\text{O}\_2 \rightarrow \text{NO}\_2^- + 2\text{H}^+ + \text{H}\_2\text{O} \tag{2}$$

According to Rivett et al. [22] conditions under which denitrification will occur require the presence of NO3ˉ, denitrifying bacteria, oxygen concentrations (1–2 mg/L), electron donor, favorable conditions of temperature (25–35°C), pH (from 5.5 to 8.0), and other trace nutrients. Chemical and biological processes can further reduce NO2ˉ to various compounds or oxidize it to NO3ˉ. Due to its high water solubility [23], nitrate is regarded as one of the most widespread groundwater pollutant in the world, imposing a significant hazard to drinking water supplies and thus human health. The movement of NO3ˉ into water sources is related to concentration in the soil; this concentration is directly related to the total amount of N [16]. In addition and according to many researches, natural attenuation by denitrification is minimal in aquifers in semiarid areas which allows N to remain as NO3ˉ [11].

#### **Figure 3.**

*Simplified nitrogen cycle showing the principal anoxic and oxic paths influencing groundwater N in arid and semiarid areas [21].*

#### *2.2.2.1.1.2 Nitrate sources*

One of the main sources of NO3ˉ is the intensive use of fertilizers in agriculture activity, as already mentioned [23, 24]. It is worth mentioning that in some cases, especially in aquifers of arid and semiarid areas, agricultural and domestic wastes are commonly found mixed together and they both contribute in increasing NO3ˉ concentration [25]. According to Paschke et al. [26], an increase in NO3ˉ concentration after a 10-year period (1990–2000) is simultaneously related with a decrease of the herbicide atrazine and its degradation product desethylatrazine. NO3ˉ has a high mobility and low affinity for adsorbing onto clay particles, which facilities its passage into groundwater [27]. However, despite its high solubility, it is not distributed homogeneously within the aquifer [28]. Indeed, Zhang et al. [29] confirmed the distinctively higher concentration in shallow depths compared with deeper parts of an aquifer. Gutiérrez et al. [21] identified some of the groundwater of aquifers with NO3ˉ contamination depending on the type of area, aquifers of semiarid, arid and hyperarid areas (**Table 1**).

The impact of NO3ˉ pollution on surface water and groundwater has been the focus of several studies on many sites all over Morocco. According to Menkouchi et al. [30] the pollution of the groundwater by NO3ˉ affects nearly all the Moroccan territory with approximately 6% of resources having NO3ˉ content more than the national standard. Furthermore, Menkouchi demonstrated the contamination of Boujaad center with NO3ˉ (exceeded 80 mg/L). According to the spatial distribution of NO3ˉ contents made by Tagma et al. [31], the groundwater in Souss plain is less polluted than Chtouka-Massa plain. In fact, 36% of Chtouka-Massa's wells exceed the regulatory NO3ˉ limit while only 7% in Souss plain. Maria Calvache et al. [32] confirmed the highly presence of NO3ˉ in Chtouka Ait Baha, Massa, and Tiznit. Recently, Malki et al. [33] has studied and confirmed the NO3ˉ contamination of Belfaa and the irrigated area along Massa River. Hydrogeochemical results on groundwater samples collected in 2010 show that the Bou-Areg aquifer is vulnerable to NO3ˉ contamination [34]. The contamination of the Loukkos basin, Essaouira, and the basin of Triffa plain in northeast Morocco was confirmed.

#### *2.2.2.1.1.3 Nitrate effects on human health and environment*

Results of many studies suggest that ingestion of relatively high levels of NO3ˉ could cause health problems. The toxic action of NO3ˉ exposure, through diet or drinking water, can be divided into acute (short-term) effects and chronic (longterm) effects [35]. The main concern of an acute toxicity is the capacity of NO3ˉ to cause methemoglobinemia (known as blue baby disorder) after oral ingestion. In fact, in the gastrointestinal tract, the ingested NO3ˉ is reduced to NO2ˉ that binds to hemoglobin to form methemoglobin. In the case of infants, it only takes a 10 mg/L N-NO3ˉ to cause methemoglobinemia [21, 36]. For chronic toxicity, the consumption of NO3ˉ at levels higher than 50 ppm has been associated with (i) increased thyroid volume and subclinical thyroid disorders, (ii) increased incidence of goiter in children, (iii) carcinogenicity due to the conversion of NO3ˉ to NO2ˉ and formation of genotoxic/carcinogenic N-nitroso compounds, such as N-nitrosamines and N-nitrosamides, some of which are known carcinogens [23, 35].

Additionally, when N is present in overabundance of the requirements of the biological system, it increase NO3ˉ leaching which results in water eutrophication and acidification of sensitive soils [36]. This acidification involves changes in river and lake chemistry that produces secondary changes in the aquatic biota. The United States Environmental Protection Agency (USEPA) identifies eutrophication as the critical problem in those US surface waters with impaired water quality,

**45**

mammals simultaneously.

*50 mg(NO3ˉ)/L [21]*

*arid, and hyperarid areas.*

**Table 1.**

*2.2.2.1.1.4 Standards and regulations for nitrates*

*Pollution of Water Sources from Agricultural and Industrial Effluents: Special Attention…*

**Areas Region Land use, crops % >50, N Range of** 

A, U, sweet lime, cotton

barley

palms, vine

farming

alfalfa

Arid/hyperarid Southern Iran A, wheat 5.9%, N = 34 1.5–70.7 *Major land use: A = agricultural, L = livestock, G = grazing, U = urban. With N = number of samples exceeding* 

Chihuahua, Mexico A, U, alfalfa 40%, N = 45 2.2–266

Semiarid North China Plain A, wheat, maize 9.5%, N = 295 Ave. 45.3 Semiarid Dakar, Senegal U 61%, N = 36 0.3–1390 Semiarid Southwest Niger Land clearing 25%, N = 28 0.2–176 Semiarid Seville, Spain A, cotton, potato ~70%, N = 16 35–630

Semiarid Livermore CA, USA A, L, vineyard 17%, N = 35 5.2–60.2 Semiarid Osona, Spain L, pigs 82%, N = 60 10–529

Semiarid Grombalia, Tunisia A, U, citrus trees Shallow 73%,

**NO3ˉ values**

0.5–514 2–231

U, recovery 58%, N = 12 2–185

A, U 6%, N = 587 0.1–61

A, U 8%, N = 3539 0.1–130

A, G, corn 47%, N = 30 0.7–229

N = 26 40%, N = 25

G 0%, N = 29 0.3–49.2

18%, N = 496 0.1–896

18%, N = 684 <0.5–125

30%, N = 53 1–330

32%, N = 52 <0.1–113

0%, N = 120 5–40

whereas the United Nations Environment Programme (UNEP) states that eutrophication is "probably the most pervasive water quality problem on a global scale" (UNEP 1991). High NO3ˉ concentrations are known to stimulate heavy blue-green algal growth (such as *Cyanobacteria*), which produce poisonous toxins to fish and

*NO3ˉ concentration (mg(NO3ˉ)/L) and % samples exceeding 50 mg(NO3ˉ)/L in some aquifers from semiarid,* 

In order to restore the quality of water and deter hazards to humankind, various approaches have been targeted in terms of standards and legislation. In many countries, there are strict limits on the permissible concentration of NO3ˉ in

*DOI: http://dx.doi.org/10.5772/intechopen.86921*

Palestine

USA

USA

India

Semiarid La Mancha, Spain A, corn, wheat,

USA

Semiarid Arava Valley, Israel A, U, flowers,

Argentina

Arid/hyperarid NW China G, subsistence

Arid/hyperarid Central Iran U, A, almonds,

Semiarid Gaza Strip,

Semiarid Rio Grande Valley,

Semiarid Basin and Range,

Semiarid Andhra Pradesh,

Semiarid South Platte River,

Arid/hyperarid Monte Desert,


*Pollution of Water Sources from Agricultural and Industrial Effluents: Special Attention… DOI: http://dx.doi.org/10.5772/intechopen.86921*

#### **Table 1.**

*Water Chemistry*

*2.2.2.1.1.2 Nitrate sources*

hyperarid areas (**Table 1**).

One of the main sources of NO3ˉ is the intensive use of fertilizers in agriculture activity, as already mentioned [23, 24]. It is worth mentioning that in some cases, especially in aquifers of arid and semiarid areas, agricultural and domestic wastes are commonly found mixed together and they both contribute in increasing NO3ˉ concentration [25]. According to Paschke et al. [26], an increase in NO3ˉ concentration after a 10-year period (1990–2000) is simultaneously related with a decrease of the herbicide atrazine and its degradation product desethylatrazine. NO3ˉ has a high mobility and low affinity for adsorbing onto clay particles, which facilities its passage into groundwater [27]. However, despite its high solubility, it is not distributed homogeneously within the aquifer [28]. Indeed, Zhang et al. [29] confirmed the distinctively higher concentration in shallow depths compared with deeper parts of an aquifer. Gutiérrez et al. [21] identified some of the groundwater of aquifers with NO3ˉ contamination depending on the type of area, aquifers of semiarid, arid and

The impact of NO3ˉ pollution on surface water and groundwater has been the focus of several studies on many sites all over Morocco. According to Menkouchi et al. [30] the pollution of the groundwater by NO3ˉ affects nearly all the Moroccan territory with approximately 6% of resources having NO3ˉ content more than the national standard. Furthermore, Menkouchi demonstrated the contamination of Boujaad center with NO3ˉ (exceeded 80 mg/L). According to the spatial distribution of NO3ˉ contents made by Tagma et al. [31], the groundwater in Souss plain is less polluted than Chtouka-Massa plain. In fact, 36% of Chtouka-Massa's wells exceed the regulatory NO3ˉ limit while only 7% in Souss plain. Maria Calvache et al. [32] confirmed the highly presence of NO3ˉ in Chtouka Ait Baha, Massa, and Tiznit. Recently, Malki et al. [33] has studied and confirmed the NO3ˉ contamination of Belfaa and the irrigated area along Massa River. Hydrogeochemical results on groundwater samples collected in 2010 show that the Bou-Areg aquifer is vulnerable to NO3ˉ contamination [34]. The contamination of the Loukkos basin, Essaouira,

Results of many studies suggest that ingestion of relatively high levels of NO3ˉ could cause health problems. The toxic action of NO3ˉ exposure, through diet or drinking water, can be divided into acute (short-term) effects and chronic (longterm) effects [35]. The main concern of an acute toxicity is the capacity of NO3ˉ to cause methemoglobinemia (known as blue baby disorder) after oral ingestion. In fact, in the gastrointestinal tract, the ingested NO3ˉ is reduced to NO2ˉ that binds to hemoglobin to form methemoglobin. In the case of infants, it only takes a 10 mg/L N-NO3ˉ to cause methemoglobinemia [21, 36]. For chronic toxicity, the consumption of NO3ˉ at levels higher than 50 ppm has been associated with (i) increased thyroid volume and subclinical thyroid disorders, (ii) increased incidence of goiter in children, (iii) carcinogenicity due to the conversion of NO3ˉ to NO2ˉ and formation of genotoxic/carcinogenic N-nitroso compounds, such as N-nitrosamines

Additionally, when N is present in overabundance of the requirements of the biological system, it increase NO3ˉ leaching which results in water eutrophication and acidification of sensitive soils [36]. This acidification involves changes in river and lake chemistry that produces secondary changes in the aquatic biota. The United States Environmental Protection Agency (USEPA) identifies eutrophication as the critical problem in those US surface waters with impaired water quality,

and the basin of Triffa plain in northeast Morocco was confirmed.

and N-nitrosamides, some of which are known carcinogens [23, 35].

*2.2.2.1.1.3 Nitrate effects on human health and environment*

**44**

*NO3ˉ concentration (mg(NO3ˉ)/L) and % samples exceeding 50 mg(NO3ˉ)/L in some aquifers from semiarid, arid, and hyperarid areas.*

whereas the United Nations Environment Programme (UNEP) states that eutrophication is "probably the most pervasive water quality problem on a global scale" (UNEP 1991). High NO3ˉ concentrations are known to stimulate heavy blue-green algal growth (such as *Cyanobacteria*), which produce poisonous toxins to fish and mammals simultaneously.

#### *2.2.2.1.1.4 Standards and regulations for nitrates*

In order to restore the quality of water and deter hazards to humankind, various approaches have been targeted in terms of standards and legislation. In many countries, there are strict limits on the permissible concentration of NO3ˉ in

drinking water and in many surface waters. The USEPA [37] has set an enforceable standard called maximum contaminant level (MCL) in water for NO3ˉ at 10 parts per million (ppm) (10 mg/L) and for NO2ˉ at 1 ppm (1 mg/L), [59] and this is for all public water supplies. A summary of water quality guidelines for N-NO3ˉ, made by the USEPA, is reported in **Table 2** [39]. Furthermore, the intake limits for NO3ˉ in foods were set by the joint expert committee on food additives of the FAO/WHO and the European commission's scientific committee on food, at an acceptable daily intake for NO3ˉ of 0–3.7 mg (NO3ˉ)/kilogram (kg) body weight [40]. The same goes for Canada that set a MCL at 10 mg/L for NO3ˉ as N and 1 mg/L for NO3ˉ as N. For Morocco, the quality limits imposed by Order No. 1277-01 of 10 Shaaban 1423 (17 October 2002) setting quality standards for surface water used for the production of drinking water, has also set a MCL at 50 mg/L for NO3ˉ [41].
