Heavy metal phyto-accretion, biochemical responses and non-carcinogenic human health risks of genetically diverse wheat genotypes cultivated with sewage of municipal origin.

Current study explored the effects of municipal sewage (MS) irrigation on heavy metal phyto-accretion, biochemical responses and human health risks of diverse wheat genotypes along with recycled municipal sewage (RMS). Mean concentrations of PO43-, NO3--N, chemical oxygen demand, biological oxygen demand, K, Co, Cu, Cd, Cr and Ni were found higher in MS than irrigation criteria. This led to significant increase in heavy metal contents in roots, stem and grains of MS irrigated wheat genotypes compared to RMS and control treatments. No adverse health risk effects for individual or multiple metals were recorded in RMS irrigated wheat genotypes on grounds of lowest heavy metal accumulation. Multivariate techniques i.e. principal component analyses (PCA) and hierarchical agglomerative cluster analyses (HACA) identified tolerant (inefficient metal accumulators) and sensitive (efficient metal accumulators) wheat genotypes in MS and RMS. Tolerant wheat genotypes showed lowest accumulation of heavy metals, efficient biochemical mechanisms to combat oxidative stress and lower health risks to adults/children. Cultivation of identified tolerant wheat genotypes is recommended in areas receiving municipal wastes to reduce human and environmental health risks. Moreover, genetic potential of identified tolerant wheat genotypes from MS and RMS can be utilized in breeding heavy metal tolerant wheat germplasm worldwide.

Treatment efficiency of a hybrid constructed wetland system for municipal wastewater and its suitability for crop irrigation.

Design and implementation of wastewater treatment is inevitable due to toxic effects of wastewater irrigation on crops, soil and human health. Current investigation is the pioneer attempt on full-scale hybrid constructed wetland system (HCWS) built for municipal wastewater treatment from Pakistan. HCWS was comprised of vertical sub-surface flow constructed wetland (VSSF-CW) and five phyto-treatment ponds connected in series. Higher environmental risk was associated with untreated municipal wastewater usage in irrigation as estimated through discharge of metals to recipient soils. Treatment efficiency percentages recorded for HCWS reclaimed water quality parameters were, i.e., EC (56.68), TDS (56.86), alkalinity (39.67), chloride (39.68), sulfate (46.73), Na (28.80), Mn (65.24), Cr (78.07), Ni (81.02), BOD (68.74), total hardness (19.56), Fe (70.09), phosphate (55.40), Pb (80.48), COD (63.64), Mg (17.24), K (60.05), Co (100), Cu (67.73), Zn (59.97), Cd (100), and Ca (21.47) respectively. Wastewater treatment in HCWS was due to aquatic plants [Phragmites australis Cav. Trin. ex Steud., Canna indica L. Typha latifolia L., and Hydrocotyle umbellata L.], microbial activities and substrate based wetland processes. The HCWS treated water was well under irrigation standards and recommended for safer crop production in water scarce regions.

Baseline water quality of municipal ponds and metal removal ability of Typha latifolia L. from sewage and industrial wastewaters.

Municipal effluent of three rural settings of Islamabad was assessed for physicochemical and microbiological parameters by collecting wastewater from inlet and center of ponds. Results showed that water quality was comparatively better at the center as Typha latifolia plants were growing toward the center of ponds. In another study, the wastewater treatment ability of T. latifolia was investigated by growing them in industrial and municipal effluent under greenhouse conditions. Water and plant samples were collected periodically (3rd, 10th, 17th, 24th, and 31st day after transplanting) for the measurement of Pb, Cu, and Cd concentrations. A decrease in heavy metal concentration of both effluents was observed as the experiment progressed and metal removal percentages ranged between 81% and 96%. Complementary the increase in metal concentration in plant tissues was observed over experimental period. Among plant tissues, metal concentration of Pb was highest i.e. 362 mg kg-1 in roots and 313 mg kg-1 in shoots at end of experiment. Pb, Cu, and Cd concentrations were higher in roots than shoots and hence translocation factors were less than 1.0. Metal removal efficiency was better from industrial wastewater and was in order of Pb > Cu > Cd. T. latifolia can be used for remediation of heavy metal-polluted wastewater.

Metal accumulation potential, human health risks, and yield attributes of hundred bread wheat genotypes on irrigation with municipal and remediated wastewater.

This study was carried out to screen historical diversity panel of bread wheat against municipal wastewater (MW) and remediated wastewater (RW) irrigation to find tolerant and sensitive genotypes and their impact on yield attributes. The experiment was conducted in randomized complete block design (RCBD) with three water treatments, i.e., tap water (TW), RW, and MW. Yield attributes, health risk assessment, water and soil chemistry were recorded. Principal component analysis (PCA) was used to identify tolerant and sensitive genotypes of wheat on the basis of metal accumulation. Metal accumulation in grains increased in pattern K > Fe > Zn in all irrigation treatments. Tolerant genotypes in MW showed lowest hazard quotient (HQ) and hazard index (HI) values (adults 0.62; children 0.67) for Fe and Zn as compared to sensitive genotypes (adults 1.53; children 1.70). However, HI values in sensitive and tolerant genotypes of RW were recorded < 1. Mean values of yield attributes, i.e., plant height, spike length, spikelet per spike, grains per plant, biological yield, grain yield, and thousand kernel weight, were recorded in pattern, i.e., MW > RW > TW. In this study, yield attributes and human health are affected in both cases of higher and lower concentration of Fe and Zn metal. It is suggested that tolerant genotypes can prove useful for cultivation in areas receiving MW and also provide molecular breeding opportunities for seeking tolerance against metal stresses.