Wastewater-irrigated Soil Research Articles

Comparative role of animal manure and vegetable waste induced compost for polluted soil restoration and maize growth.

Soil amendment with two types of composts: animal manure (AC) and vegetable waste (VC) induced composts have potential to alleviate Cd toxicity to maize in contaminated soil. Therefore, Cd mobility in waste water irrigated soil can be addressed through eco-friendly and cost effective organic soil amendments AC and VC that eventually reduces its translocation from polluted soil to maize plant tissues. The comparative effectiveness of AC and VC at 3% rate were evaluated on Cd solubility, its accumulation in maize tissues, translocation from root to shoot, chlorophyll contents, plant biomass, yield and soil properties (pH, NPK, OM). Results revealed that the addition of organic soil amendments significantly minimized Cd mobility and leachability in soil by 58.6% and 47%, respectively in VC-amended soil over control. While, the reduction was observed by 61.7% and 57%, respectively when AC was added at 3% over control. Comparing the control soil, Cd uptake effectively reduced via plants shoots and roots by 50%, 46% respectively when VC was added in polluted soil. However, Cd uptake was decreased in maize shoot and roots by 58% and 52.4% in AC amended soil at 3% rate, respectively. Additionally, NPK contents were significantly improved in polluted soil as well as in plant tissues in both composts amended soil Comparative to control, the addition of composts significantly improved the maize dry biomass and chlorophyll contents at 3% rate. Thus, present study confirmed that the addition of animal manure derived compost (AC) at 3% rate performed well and might be consider the suitable approach relative to vegetable compost for maize growth in polluted soil.

Short-Term Effect of Biochar on Microbial Biomass, Respiration and Enzymatic Activities in Wastewater Irrigated Soils in Urban Agroecosystems of the West African Savannah

Irrigated urban agriculture (UA) supports the economy and health of urban inhabitants in low-income countries. This system is often characterized by high nutrient inputs and mostly utilizes wastewater for irrigation. Biochar has been proposed to increase crop yields and improve soil properties. In this study, we assessed the transient effect of rice husk biochar (20 t ha−1) and/or fertilizer (NPK: 15-15-15) on microbial respiration, microbial biomass carbon and enzyme activities of irrigated (wastewater and tap water) soil from an UA field experiment in the Guinea savannah zones of Ghana. Our results showed an increase by up to 123% in soil organic carbon (SOC) after a year of biochar application, while hot water extractable carbon (HWEC) was increased by only 11 to 26% and microbial biomass carbon (MBC) by 34%. Basal respiration was significantly increased in mineral fertilized soil by up to 46% but decreased by 12–45% under wastewater irrigation. Overall, the metabolic quotient (qCO2) indicated less stress for the microbial community and increased carbon use efficiency with biochar application and wastewater irrigation. Total enzymes activity was increased under wastewater irrigation and biochar treated soils exhibit a more diverse composition of C-cycling enzymes and a higher activity of aminopeptidases. Biochar and wastewater showed positive effects on biological soil properties and contributed to soil fertility. Our results suggest beneficial effects of biochar on non-biochar SOC stocks in the long term.

Effects of Fire Phoenix (a genotype mixture of Fesctuca arundinecea L.) and Mycobacterium sp. on the degradation of PAHs and bacterial community in soil.

Phytomicrobial remediation technology of PAH-contaminated soils has drawn great attention due to its low-cost, eco-friendly, and effective characteristics, but the mechanism underlying the removal of PAHs by rhizosphere in wastewater-irrigated soil is so far not clear. To evaluate the dissipation of PAHs and the shifts of bacterial community structure under plant-microorganism symbiotic system in an agricultural soil, a rhizo-box experiment with Fire Phoenix (a genotype mixture of Fesctuca arundinecea L.) or/and inoculated Mycobacterium sp. was conducted for 60 days. The changes of bacterial community structure and the contents of PAHs were analyzed by denaturing gradient gel electrophoresis (DGGE) and high-performance liquid chromatography (HPLC), respectively. The results showed that the removal rate of PAHs in phytomicrobial combined treatment was 53.7% after 60 days. The PAH-degraders were dominated by Microbacterium sp., Sphingomonas sp., Mycobacterium sp., and Flavobacterium sp. The plant of Fire Phoenix induced the appearance of Pseudomonas sp. and TM7 phylum sp. oral clone. The highest of bacterial diversity index was observed in unrhizosphere soils (MR-), rather than that in rhizosphere soils (MR+). In combination, phytomicrobial combined treatment of Fire Phoenix and Mycobacterium strain enhanced the removal rate of PAHs and changed the structure of bacterial community and bacterial diversity. Bacterial community has great effect on PAH degradation in PAH-contaminated soil from the wastewater-irrigated site. Our study can provide support information for PAH degradation enhancement by the synergetic effect of Fire Phoenix and Mycobacterium sp.

Effect of improved land and water management strategies on crop productivity and soil fertility in wastewater irrigated eggplant (Solanum melongena)

Wastewater irrigation with efficient land and water management strategies improve the marketable yield as well as reduce the pollutant threat posed by the irrigation. A field experiment was conducted for two years (2014- 2016) at ICAR- IARI farm, New Delhi to study the effect of municipal wastewater irrigation along with two land configurations (ridge and furrow and basin) and two methods of irrigation (drip and flood) on the yield of eggplant (Solanum melongena cv. Supriya) and soil health. Wastewater irrigated eggplants resulted significantly higher yield (37.1 t/ha), fruit weight (325 g) and fruit diameter (10.02 cm) in the tune of 38, 26 and 7% higher respectively over groundwater irrigated plot. Among irrigation methods, drip irrigation increased yield, fruit weight and fruit diameter of eggplant by 10, 9 and 1% higher over flood irrigation. Significantly higher fruit weight (294 g) of eggplant was recorded with the flat bed system compared to a raised bed system (288 g) and higher yield (4%) was also recorded under a flat bed system over a raised bed system. Wastewater irrigated plots recorded higher plant height, number of branches per plant as compared to groundwater irrigated plants at 120 and 180 days after transplanting. Application of wastewater significantly enhanced available N and P content and DTPA-Pb and Fe in the soil as compared to groundwater irrigated soil. Flood irrigation led to the accumulation of DTPA-Pb and Ni in soil, compared to drip irrigation. Significantly higher dehydrogenase activity, fluorescein diacetate activity and soil microbial biomass carbon were noticed in wastewater irrigated soil as compared to groundwater plots at upper depth (0-5cm). The findings of the present investigation illustrate that wastewater applied through drip irrigation resulted in yield increment as well as reduced metal concentrations in soil.

Risk assessment of hazardous elements in wastewater irrigated soil and cultivated vegetables in Pakistan

Wastewater irrigation leads to the deposition of hazardous elements (HE) in irrigated soils which could be accumulated in cultivated vegetables, contaminating the food chain and pose threat to the human population. HE concentrations could be varied in the wastewater-irrigated and background soil and cultivated vegetables with season depending on temperature, humidity, and quantity of irrigation water. For this purpose, soil and vegetable samples were collected in the summer and winter seasons of Peshawar, Pakistan, and analyzed for HE including Cu, Cr, Cd, Co, Zn, Pb, Mn, and Ni. Results revealed that HE contaminations except for Ni in wastewater-irrigated soil and vegetables of both seasons were multifold higher than reference. Between seasons, summer had higher HE contamination in soil and vegetables compared to the winter season. The Cd and Ni concentrations in soil and Pb, Cd, and Cr in vegetables of both seasons exceeded their respective threshold limits set by the Food and Agriculture Organization/World Health Organization. Soil enrichment factors for HE contamination were observed greater than one that could be attributed to wastewater irrigation. Higher values of bioaccumulation factors were found for Cd (1.4), Co (1.8), and Cu (4.0). HE concentrations of vegetables were used for the risk assessment using average daily intake (ADI) and target hazard quotient (THQ). The ADI values of Cd and Pb were observed higher than their respective referenced dose. The THQ values ranged from 0.002–3.86 and 0.02–3.46 for adults and children. Higher THQ values could result in various health problems for the exposed human community.

Effect of Source of Irrigation Water on Soil Chemical Properties in Tamale Metropolis, Ghana

This study analyzed the effect of different water sources of irrigation on the chemical constituents of soils in the Tamale Metropolis of Ghana. Soil samples were taken from depths of 0 – 30 cm and 30 – 60 cm in wastewater, pipe water and non-irrigated (control) sites. Variations in levels of concentration of the various chemical properties, however, occurred among the three different soils. With the exception of % N and Mg, there was no significant difference among all the three soils for all the parameters. The results indicated that N level increased in wastewater irrigated soils as compared to pipe water and non-irrigated soils. P increased with wastewater irrigation but decreased with soil depth. K concentration in wastewater irrigated soils increased in the depth of 0 – 30 cm but decreased in the depth of 30 – 60 cm. Wastewater and pipe water irrigation decreased soil Na and Cl levels compared to the control (non-irrigated soils). Wastewater irrigation increased the level of EC and CEC whilst Cu, Zn and Cd levels increased with soil depth. Cu, Zn and Cd levels of the wastewater, pipe water and non-irrigated soils were higher than the FAO (1985) recommended levels for both depths. It can be concluded that irrigation with wastewater increased soil primary macro nutrients (NPK) whilst micro nutrients such as sodium and chloride decreased with wastewater and pipe water irrigation.

Critical risk analysis of metals toxicity in wastewater irrigated soil and crops: a study of a semi-arid developing region

Toxic elemental exposure through consumption of contaminated crops is becoming a serious concern for human health. Present study is based on the environment and health risk assessment of wastewater irrigated soil and crops in a semi-arid region Faisalabad, Pakistan. The concentrations of potentially toxic elements (Cu, Cr, Mn, Fe, Pb, Zn, Ni) were analysed by atomic absorption spectrometer in five different crops (Corn, rice, wheat, sugarcane and millet), while, their topsoil’s and multi targeted risks analysis were assessed. Results showed, the mean values of Pb and Zn were higher in crop than Food and Agriculture Organization guidelines for food additives and contaminants. A strong positive correlation was found among wastewater and crop’s toxic metals (r2 values in Cu, Zn, Pb, Ni and Cr were 0.913, 0.804, 0.752, 0.694, 0.587 respectively). Whereas, a strong correlation was also found among soil and wastewater lead (r2 = 0.639). The calculations of Nemerow Integrated Pollution Index (NIPI) showed the soil samples maximum pollution limit (NIPI > 3) and Potential Ecological Risk Index (PERI) was found to be higher than maximum limit (PERI > 600) for all samples. While, for non-carcinogenic risk, Hazard Index (HI) values in adult were near threshold (HI > 1) for all crop samples. In children, the HI values for Corn, Rice and Wheat were above threshold limit and for Sugarcane and Millet, these were near to threshold. Cancer risk values for Cr found higher than safe limit (1 × 10–6) in adult and children for crop samples. Crop irrigation by wastewater irrigation is a prominent alternative option for water scarce countries, however prior testing and treatment of such wastewater streams must be employed to minimize the adverse impacts on human health and environment.

Rhizobioaugmentation of Casuarina glauca with N-fixing actinobacteria Frankia decreases enzymatic activities in wastewater irrigated soil: effects of Frankia on C. glauca growth.

The use of wastewater for irrigation in agroforestry is cost-effective for water management. It is well established that rhizospheric microorganisms such as N2-fixing bacteria are able to modulate rhizobioaugmention and to boost phyoremediation process. To date, no study has been conducted to evaluate biological effects of rhizobioaugmentation in Casuarina glauca trees induced by their symbiont N-fixing actinobacteria of the genus Frankia. The objective of the present study was to evaluate the main effects of rhizobioaugmentation on the biological activity in the C. glauca's rhizosphere and on C. glauca growth in soils irrigated with industrial wastewater. Two Frankia strains (BMG5.22 and BMG5.23) were used in a single or dual inoculations of C. glauca seedlings irrigated with industrial wastewater. Soil enzymes activity related to carbon, phosphorus, sulfur and nitrogen cycling were measured. Results revealed that the BMG5.22 Frankia strain increases significantly the size (dry weight) of C. glauca shoots and roots while dual inoculation increased significantly the root length. Surprisingly, β-glucosidase (BG), cellobiohydrolase (CBH), β-N-acetylglucosaminidase (NAGase), aryl sulfatase (AS), acid phosphatase (AP), alkaline phosphatase (AlP), glycine aminopeptidase (GAP), leucine aminopeptidase (LAP), and peroxidase (PER) activity in the rhizosphere decreased significantly in soils treated with the two strains of symbionts. This suggests no positive correlations between enzymatic activity and C. glauca growth.

Risk analysis by bioaccumulation of Cr, Cu, Ni, Pb and Cd from wastewater-irrigated soil to Brassica species

In order to evaluate the possible human health risk by phyto-accumulation of five heavy metals, viz. Cr, Cd, Cu, Pb and Ni, four Brassica species, namely B. campestris, B. juncea, B. napus and B. nigra, were grown under field conditions irrigated with 100% (undiluted) and 50% (diluted) wastewater (WW). The groundwater treatment was taken as control. WW irrigations (50% and 100%) were found to increase growth parameters (length, fresh biomass and dry biomass of shoot and root) and seed yield of all Brassica species. Calculated metal indices showed tolerance ability (tolerance index, TolI > 1) of all four Brassica species growing in both 50% and 100% WW-irrigated soil, but none of these could act as hyperaccumulator (bioconcentration factor, BCF 1), representing the human health at serious risk.

Spatial distribution of metals in soils under agriculture in the Jordan Valley

The aim of this study was to evaluate levels, sources, and spatial distribution of 6 metals in soils under agriculture in the Jordan valley. A total of 127 surface soil samples (101 irrigated with treated wastewater and 26 with fresh water) were collected at a density of one sample per 2 km2, and concentrations of As, Cd, Cr, Cu, Pb, and Zn were analyzed. In addition, clay content, pH, salinity, sodicity, organic carbon, total phosphorus and total nitrogen were measured for all samples. Principal component analysis and Pearson correlation matrix were used to identify possible metal sources. Average soil metal levels in treated wastewater were higher than in fresh water except for Cd. The mean values of the heavy metals in treated wastewater irrigated soils were 1.07, 2.87, 27.39, 14.46, 43.93, and 97.21 mg kg−1, while average metal contents in fresh water irrigated soils were 0.61, 3.22, 18.68, 8.03, 33.66, and 65.87 mg kg−1. The mean concentrations of all metals were below the maximum permissible concentration according to WHO/FAO threshold values for soils under agriculture. Multivariate and geostatistical analyses suggested that soil metals were mainly derived from agricultural practices (fertilizer, organic manure, and treated wastewater use) and parent materials. Results showed that Zn, and Cu were mainly derived from fertilizer use, As mainly from soil parent materials, and Cd, and Cr, and Pb mainly from treated wastewater and organic fertilizer use. Documenting metal levels in these soils may help in understanding their sources and assisting to take certain undertaking measures and actions to protect soil quality. Caution should be taken into consideration to decrease the excessive use of inorganic fertilizers and manage more efficiently TWW use.

Ecological risk assessment of heavy metals in vegetables irrigated with groundwater and wastewater: The particular case of Sahiwal district in Pakistan

The use of wastewater for irrigation is a common practice in the developing world. It is a major route of heavy metal contamination in vegetables. The groundwater, an alternative source for irrigation, is under threat of heavy metal contamination due to long-term use of wastewater. The present study investigated heavy metals contamination from irrigation with wastewater compared to groundwater in District Sahiwal situated in the vicinity of Lahore, Pakistan. Irrigated water, soil and vegetables were analyzed for Iron, Nickel, Lead, copper, Cadmium, Manganese and Zinc; Metal transfer factor (MTF); daily intake of metals (DIM) and health risk index (HRI) were calculated. Manganese (Mn) and Cd in wastewater irrigated soil, Pb, Cd, Mn and Fe in wastewater-irrigated vegetables and Pb, Mn and Fe in groundwater-irrigated vegetables exceeded the permissible limits (WHO, 1996), particularly in Mustard and Spinach. Generally, MTF was higher in wastewater than groundwater-irrigated vegetables, particularly with Fe followed by Ni. HRI was higher for wastewater-irrigated than groundwater-irrigated vegetables. Wastewater-irrigated Mustard and Spinach showed a HRI > 1 only for Mn. Quality control mechanisms need to be applied for long-term use of groundwater. Also, treatment of wastewater prior to application to plants must be considered to save crops from contamination.

Survey of Listeria monocytogenes contamination of various environmental samples and associated health risks

Listeria monocytogenes is the causative agent of listeriosis, one of the most important foodborne infections. Pre-harvest contamination of ready to eat crops constitutes a potential source of Listeria infections. The aim of this study was to investigate the presence of Listeria spp. and L. monocytogenes via molecular methods in wastewater effluent, sewage sludge (SS) and livestock manure as potential sources of Listeria. The presence of L. monocytogenes in wastewater-irrigated soil and crops was also investigated. Quantitative microbial risk assessment (QMRA) was performed for analysis of Listeria infections for SS workers and farmers. The results of survey showed no presence of L. monocytogenes in wastewater effluent and wastewater-irrigated soil and crop samples, whereas L. monocytogenes was detected in SS (50%) and manure (8%) samples. QMRA analysis using exponential model showed that the likelihood of Listeria infections from direct ingestion of SS to be very low. In contrast, Beta-Poisson dose-response model showed an annual risk of Listeria infections higher than the proposed value of 10−4 per person per year (pppy) by EPA, with the highest risk (4.41 × 10−1 pppy) for SS workers. Based on our results, the agricultural use of wastewater doesn't seem to present risk of Listeria infections for consumers of wastewater-irrigated crops. However, direct ingestion of SS may pose a risk for exposed individuals. The estimated risk values could be further improved by obtaining accurate insights into the prevalence of Listeria infections especially at national or regional level. Further studies are also needed to determine inactivation rate of Listeria in SS-amended soils in arid and semi-arid areas.

Antibiotic resistance and class 1 integron gene dynamics along effluent, reclaimed wastewater irrigated soil, crop continua: elucidating potential risks and ecological constraints

Reuse of municipal wastewater is a growing global trend, but currently there is lack of consensus regarding the potential dissemination of antibiotic resistance elements by treated wastewater irrigation. We tracked intI1, a proxy for anthropogenic pollution, and an assemblage of antibiotic resistance genes associated with mobile elements and/or wastewater (blaGES, blaOXA2, blaOXA10, blaTEM, blaCTX-M-32 and qnrS) in treated wastewater effluents, effluent stabilization reservoirs, and along irrigation water-soil-crop continua in experimental lysimeters and large-scale commercial fields. While several of the targeted antibiotic resistance genes were profuse in effluents, there was almost no correlation between gene abundance in irrigation water and those detected in soil, and no evidence of systematic gene transfer to irrigated soil or crops. In contrast, soil intI1 abundance correlated strongly to irrigation water levels in lysimeters and sandy field soils, but this was not the case for clay-rich soils or for most of the analyzed crops, suggesting that intI1 may not always be a reliable marker for tracking the impact of treated wastewater irrigation. We hypothesize that "ecological boundaries" expedited by biotic and abiotic factors constrain dissemination of antibiotic resistance elements, and assert that a more holistic perception of these factors is crucial for understanding and managing antibiotic resistance dissemination.

The responses of a soil bacterial community under saline stress are associated with Cd availability in long-term wastewater-irrigated field soil

Long-term wastewater irrigation impacts soil geochemical properties (salinity, pH and soil aggregates) and promotes the bioaccumulation of heavy metals to plants, which may change soil function, decrease soil health, decrease the productivity of farmland, and even cause land degradation. In this study, we explored the impact of saline stress on soil bacterial communities and Cd availability in long-term wastewater-irrigated field soil. Different amounts of saline stress by adding 0.1, 0.3 and 0.5% salts in a fixed proportion (NaCl: Na2SO4: NaHCO3: Na2CO3 = 1:9:9:1) were applied in a 1-year, multiple cropping system with winter wheat (Triticum aestivum L.) and summer maize (Zea mays L.) in wastewater-polluted soil. Increased salinity in the soil increased Cd availability: compared with CK (no extra salts addition), addition of 0.5% mixed salts significantly increased soil available Cd up by 67.5% and grain Cd concentration by 43.7%, and adding 0.5% salts also resulted in the increases of soil pH (∼0.5 unit) and electric conductivity (97.4%). Soil saline stress significantly changed major soil microbes in Cd-contaminated soil. Increased saline stress enriched taxa in the Bacillaceae, Staphylococcaceae and Pseudomonadaceae bacterial families, while one family within Proteobacteria (Sphingomonadaceae) was the most sensitive biomarker, based on Cd contamination without saline stress in CK-treated soils. Structural equation modeling (SEM) analysis revealed that soil saline stress induced an increase in soil Cd availability that was regulated by the bacterial community.

Land Use Change and Water Quality Use for Irrigation Alters Drylands Soil Fungal Community in the Mezquital Valley, Mexico.

Soil fungal communities provide important ecosystem services, however, some soil borne representatives damage agricultural productivity. Composition under land-use change scenarios, especially in drylands, is rarely studied. Here, the soil fungal community composition and diversity of natural shrubland was analyzed and compared with agricultural systems irrigated with different water quality, namely rain, fresh water, dam-stored, and untreated wastewater. Superficial soil samples were collected during the dry and rainy seasons. Amplicon-based sequencing of the ITS2 region was performed on total DNA extractions and used the amplicon sequence variants to predict specific fungal trophic modes with FUNGuild. Additionally, we screened for potential pathogens of crops and humans and assessed potential risks. Fungal diversity and richness were highest in shrubland and least in the wastewater-irrigated soil. Soil moisture together with soil pH and exchangeable sodium were the strongest drivers of the fungal community. The abundance of saprophytic fungi remained constant among the land use systems, while symbiotic and pathogenic fungi of plants and animals had the lowest abundance in soil irrigated with untreated wastewater. We found lineage-specific adaptations to each land use system: fungal families associated to shrubland, rainfed and part of the freshwater were adapted to drought, hence sensitive to exchangeable sodium content and most of them to N and P content. Taxa associated to freshwater, dam wastewater and untreated wastewater irrigated systems show the opposite trend. Additionally, we identified potentially harmful human pathogens that might be a health risk for the population.

Experimental study on accumulation of heavy metals in vegetables irrigated with treated wastewater

Treated sewage and industrial effluents are used for irrigation of crops in developing countries which may contain heavy metals in high concentration. It can contaminate soil and accumulate in vegetables. In the present study, the vegetables were irrigated with treated wastewater brought from a nearby full-scale sewage treatment plant. The concentration levels of the Cd, Co, Cu, Mn and Zn in the leaves were found below toxic limits as prescribed in the literature. Daily intake metals values suggest that the consumption of plants grown in treated wastewater and tap water is nearly free of risks, as the dietary daily intake limits of Cu, Fe, Zn, and Mn in adults can range from 1.2 to 3 mg, 10 to 50 mg, 5 to 22 mg and 2 to 20 mg, respectively. The enrichment factor for the treated wastewater irrigated soil was found to decrease in order of Zn > Ni > Pb > Cr > Cu > Co > Mn > Cd.

Geochemical Analysis of Soil Physicochemical Properties and Heavy Metals Content in the Long- term Wastewater-irrigated Soils

Geochemical Analysis of Soil Physicochemical Properties and Heavy Metals Content in the Long- term Wastewater-irrigated Soils

Cadmium accumulation, translocation factor, and health risk potential in a wastewater-irrigated soil-wheat (Triticum aestivum L.) system

The accumulation of trace elements in wastewater-irrigated soils may introduce them to the food chain and therefore can threaten human health. The present study investigated the accumulation, translocation factor, and health risk potential of cadmium (Cd) in a soil-wheat system irrigated with treated wastewater compared with a reference soil (irrigated with fresh water). All treated wastewater-irrigated soils showed significantly higher levels of electrical conductivity (EC) than that of reference soil by 75–143%. Irrigation with treated wastewater increased both available and total Cd content in soil by 2–4 times. In all irrigated sites, Cd content was about twice as great as the maximum acceptable rate. Bioconcentration factor (BCF) and translocation factor (TF) indicated that Cd was mainly accumulated in the roots (BCF = 2.2–3.1), while little mobilization from roots to stems and grains was noted (TFshoot/root = 0.07–0.21; TFgrain/root = 0.18–0.24). The average hazard quotient (HQ) for different age groups of the population varied in the range of 0.1–1.0, implying low non-carcinogenic health risk of Cd to local wheat-consuming residents. The risk of Cd to cause carcinogenic health risk (CR) was in the range of 1 × 10-5 to 1 × 10-4, indicating low to moderate potential risk. CR for different age groups was in the order: individuals above 18 years old > individuals 7–18 years old > individuals 0–6 years old. For reducing potential health risks to local people, it is imperative to continuously monitor heavy metal levels in the wheat-soil system and urgently adopt more efficient managerial strategies to reduce Cd contamination.

Heavy metal contamination and ecological-health risk evaluation in peri-urban wastewater-irrigated soils of Beni-Mellal city (Morocco)

ABSTRACT The present study evaluated the metal contamination and its detrimental effects in agricultural soils irrigated by wastewater at the region of Béni-Mellal. A set of soil proprieties (texture, pH, EC, OM, CaCO3) and heavy metals (Cd, Cr, Cu, Pb, Zn, Fe) were measured. Soil contamination level and risks were assessed using geoaccumulation index (Igeo), contamination factor (CF), enrichment factor (EF) and pollution load index (PLI), ecological risk (RI), hazard quotient (HQ), and non-carcinogenic risk (HI) for ingestion exposure. Results showed that mean levels of all metal elements, except Pb, in agricultural soils were higher than the local background values. Igeo, CF and EF indices revealed a moderate to high soil contamination by heavy metals, as confirmed by PLI index suggesting an anthropogenic source of these elements. The RI index indicated a considerable ecological risk, whereas HQ and HI indices suggested no obvious non-carcinogenic risk to adults and non-carcinogenic risk to the children population.

Heavy metal bioavailability and accumulation in winter wheat (Triticum aestivum L.) irrigated with treated wastewater in calcareous soils

Irrigation with raw or diluted wastewater increases in many developing countries, but the increasing availability and use of wastewater generates challenges for public agencies charged with minimizing potential impacts on public health and the environment. In this study, the available (DTPA-extractable) concentration of Zn, Cu, Cd, Pb, and Ni in the surface soil was measured in five sites irrigated with treated wastewater as compared with a site irrigated with freshwater (control). The major sources of wastewater were municipal wastewater, household, commercial, and industrial effluents, which were treated to settle and remove solids prior its use for irrigation. In addition, the concentration of the above five heavy metals and their accumulation and mobilization characteristics were determined in the roots, shoots, and grains of winter wheat (Triticum aestivum L.) grown in treated wastewater-irrigated soils. Irrigation with treated wastewater resulted in a remarkable build-up of metal concentrations in the soil (averaged over five sites) in the order of Cd (178.2%) > Ni (105.1%) > Cu (66.4%) > Zn (66.0%) > Pb (40.9%) compared with control. However, only Cd concentration exceeded the permissible range. The concentration of heavy metals was significantly greater (P < 0.05) in wheat roots than in shoots and grains (root ≫ shoot > grain). The highest concentrations were found in the roots in the order of Cu > Zn > Pb > Cd > Ni. The maximum concentrations of Zn, Cu, Ni, Cd, and Pb in wheat grains were 3.20, 1.20, 0.52, 0.31, and 0.21 mg kg−1, respectively. The bioconcentration and translocation factors of wheat showed that heavy metals quantitatively accumulated in the roots and were poorly translocated to the grains. The potential health risks, calculated as hazard quotients (HQ), were less than unity for most heavy metals, indicating that local people are within the safe limit regarding non-carcinogenic risks. However, the HQ value of Cd exceeded 1 for both children and adults, indicating a high health hazard for the whole exposed population by this metal.