Phytoremediation of heavy metals by four aquatic macrophytes and their potential use as contamination indicators: a comparative assessment.

The present study estimated the ability of four aquatic macrophytes (Eichhornia crassipes (Mart.) Solms, Ludwigia stolonifera (Guill. & Perr.) P.H. Raven, Echinochloa stagnina (Retz.) P. Beauv. and Phragmites australis (Cav.) Trin. ex Steud.) to accumulate Cd, Ni and Pb and their use for indicating and phytoremediating these metals in contaminated wetlands. Three sites at five locations in the Kitchener Drain in Gharbia and Kafr El-Sheikh Governorates (Egypt) were selected for plant, water and sediment sampling. The water in the Kitchener Drain was polluted with Cd, while Pb and Ni were far below the maximum level of Pb and Ni in the irrigation water. In comparison to the other species, P. australis accumulated the highest concentrations of Cd and Ni, while E. crassipes accumulated the highest concentration of Pb in its tissues. The four species had bioaccumulation factors (BAFs) greater than one, while their translocation factors (TFs) were less than 1 for most heavy metals, except Cd in the leaf and stem of E. stagnina and L. stolonifera, respectively, and Ni in the stem and leaf of E. stagnina. The BAF and TF results indicated that the studied species are suitable for phytostabilizing the studied heavy metals, except Ni in E. stagnina and Cd in L. stolonifera, which are suitable for phytoextracting these metals. Significant positive correlations were found between the investigated heavy metals in the water or sediment and the plant tissues. Their high BAFs, with significant proportional correlations, supported the potential of these species to serve as bioindicators and biomonitors of heavy metals in general and in the investigated metals specifically.

Uptake Prediction of Ten Heavy Metals by Eruca sativa Mill. Cultivated in Soils Amended with Sewage Sludge.

This study was carried out to develop mathematical regression equations for predicting the uptake of ten heavy metals (HMs) (cadmium, Cd; cobalt, Co; chromium, Cr; copper, Cu; iron, Fe; manganese, Mn; molybdenum, Mo; nickel, Ni; lead, Pb; zinc, Zn) by a vegetable species (Eruca sativa Mill.) in the Abha region (Saudi Arabia) based on the concentration of these HMs in soils amended with sewage sludge, organic matter (OM) content and soil pH. The resultant regression equations indicated that the three soil factors were significant predictors for the uptake of the ten HMs in the plant tissues. By applying a t test, we found that there are no significant differences between the actual and predicted values of the ten HMs in the E. sativa roots and leaves (P > 0.05), which reflects the goodness of fit of these equations for predicting the uptake of these HMs. Such types of equations may be helpful for evaluating the risk of cultivation of E. sativa plants in soils amended with sewage sludge.

Iodine-deficiency disorders in the Aseer region, south-western Saudi Arabia: 20 years after the national survey and universal salt iodization.

OBJECTIVE: To study (i) the current prevalence of iodine-deficiency disorders among schoolchildren in south-western Saudi Arabia after universal salt iodization and (ii) the iodine content of table salts and water. DESIGN: Cross-sectional study on a stratified proportional allocation sample of children. Thyroid gland enlargement was assessed clinically and by ultrasound scanning. Urine, table salt and water samples were taken to measure iodine content. Settings The Aseer region, south-western Saudi Arabia. SUBJECTS: Schoolchildren aged 8-10 years. RESULTS: The study included 3046 schoolchildren. The total goitre rate amounted to 24·0 %. Prevalence of enlarged thyroid by ultrasound was 22·7 %. The median urinary iodine concentration of the study sample amounted to 17·0 µg/l. The iodine content of table salt ranged from 0 to 112 mg/kg; 22·5 % of the table salt samples were below the recommended iodine content (15 mg/kg) set by WHO. The total goitre rate increased significantly from 19·8 % among children using table salt with iodine content ≥15 mg/kg to reach 48·5 % among children using table salt with 0 mg iodine/kg. Analysis of water samples taken from schools showed that the majority of water samples (78·8 %) had an iodine content of 0 µg/l. CONCLUSIONS: The study documented that 18 years after the national study, and after more than a decade of universal salt iodization in Saudi Arabia, the problem of iodine-deficiency disorders is still endemic in the Aseer region. Efforts should focus on fostering advocacy and communication and ensuring the availability of adequately iodized salt.