Integrated application of multiple indicators and geographic information system-based approaches for comprehensive assessment of environmental impacts of toxic metals-contaminated agricultural soils and vegetables.

Conventional monitoring and mapping approaches are laborious, expensive, and time-consuming because they need a large number of data and consequently extensive sampling and experimental operations. Therefore, due to the growing concern about the potential of contamination of soils and agricultural products with heavy metals (HMs), a field experiment was conducted on 77 farm lands in an area of 2300 ha in the southeast of Shiraz (Iran) to investigate the source of metal contamination in the soils and vegetables and to model spatial distribution of HMs (iron, Fe; manganese, Mn; copper, Cu; zinc, Zn; cadmium, Cd; nickel, Ni, and lead, Pb) over the region using geographic information system (GIS) and geostatistical (Ordinary Kriging, OK) approaches and compare the results with deterministic approaches (Inverse Distance Weighting, IDW with different weighting power). Furthermore, some ecological and health risks indices including Pollution index (PI), Nemerow integrated pollution index (NIPI), pollution load index (PLI), degree of contamination (Cdeg), modified contamination degree (mCd), PIaverage and PIvector for soil quality, multi-element contamination (MEC), the probability of toxicity (MERMQ), the potential ecological index (RI), total hazard index (THI) and total carcinogenic risk index (TCR) based on ingestion, inhalation, and dermal exposure pathways for adults and children respectively for analyzing the noncarcinogenic and carcinogenic risks were calculated. Experimental semivariogram of the mentioned HMs were calculated and theoretical models (i.e., exponential, spherical, Gaussian, and linear models) were fitted in order to model their spatial structures and to investigate the most representative models. Moreover, principal component analysis (PCA) and cluster analysis (CA) were used to identify sources of HMs in the soils. Results showed that IDW method was more efficient than the OK approach to estimate the properties and HMs contents in the soils and plants. The estimated daily intake of metals (DIM) values of Pb and Ni exceeded their safe limits. In addition, Cd was the main element responsible for ecological risk. The PIave and PIvector indices showed that soil quality in the study area is not suitable. According to mCd values, the soils classified as ultra-high contaminated for Cu and Cd, extremely high for Zn and Pb, very high, high, and very low degree of contamination for Ni, Mn, and Fe, respectively. 36, 60, and 4 % of the sampling sites had high, medium, and low risk levels with 49, 21, and 9 % probability of toxicity, respectively. The maximum health risk index (HRI) value of 20.42 with extremely high risk for children was obtained for Ni and the HI for adults and children were 0.22 and 1.55, respectively. The THI values of Pb and Cd were the highest compared to the other HMs studied, revealing a possible non-cancer risk in children associated with exposure to these metals. The routes of exposure with the greatest influence on the THI and TCR indices were in the order of ingestion > inhalation > dermal. Therefore, ingestion, as the main route of exposure, is the route of greatest contribution to health risks. PCA analysis revealed that Fe, Mn, Cu, and Ni may originate from natural sources, while Fe was appeared to be controlled by fertilizer, and Cu primarily coming from pesticide, while Cd and Pb were mainly associated with the anthropogenic contamination, atmospheric depositions, and terrific in the urban soils. While, Zn mainly originated from fertilization. Findings are vital for developing remediation approaches for controlling the contaminants distribution as well as for monitoring and mapping the quality and health of soil resources.

Effect of Biochar on Cadmium Fractions in Some Polluted Saline and Sodic Soils.

Soil contamination by heavy metals is becoming a serious environmental problem especially in saline and sodic soils and information on different fractions of metals is useful to predict their mobility and availability in soil. Addition of organic amendments, as an important technique to remediation of metals has been considered recently. Therefore, the effect of sugarcane bagasse-derived biochar on cadmium (Cd) fractions in saline, sodic, saline-sodic and normal soils were evaluated through an incubation experiment using sequential extraction. Treatments included biochar (0, 2, and 4 wt %) of sugarcane bagasse and 50 mg Cd kg-1 with three replications. In all studied soils with 2 and 4% biochar application, the organic matter fraction was the dominant form of Cd. Biochar had no significant influence on exchangeable Cd in normal and sodic soils. Whereas, application of 2 and 4% biochar increased exchangeable Cd concentration in saline and saline-sodic soils probably due to high capacity of biochar to sorb salts that mitigate the negative effects of salts in soil solution. The mobility factor (MF) of Cd in studied soils was high (20-50%). The MF value decreased with the increase of biochar dosage. According to reduced partition index, Cd was partitioned in all fractions. Based on these results, biochar can mitigate the effect of Cd pollution in these soils.

Heavy metals content and distribution in basil (Ocimum basilicum L.) as influenced by cadmium and different potassium sources.

Despite the fact that cadmium (Cd) is a non-essential element for plants, it can influence nutrients and affect human health. Potassium (K) can influence the transportation of heavy metals (HMs) in soil-plant systems. Here, a greenhouse experiment was conducted to evaluate the effect of Cd and K fertilizers on the different partitioning forms of HMs, their concentrations, uptake in the shoots and roots of Ocimum basilicum. Treatments comprised 2 levels of Cd (0 and 40 mg kg-1) and three levels of K (0, 100, and 200 mg kg-1) from three sources, i.e. KCl, K2SO4, and K-nano-chelate. 40 mg Cd kg-1 increased the shoot (above ground parts) Cd concentration. Addition of K as KCl, K2SO4, and K-nano-chelate increased the presence of Cd in shoots by 86, 82 and 76%, respectively, compared to the control. Using the nano-chelate of K can increase the accumulation of Cd in plants grown on contaminated soils to lesser content than that of the other forms of K. Application of 40 mg Cd kg-1 reduced the concentration of Zn, Cu, and Mn in the shoot, but increased shoot Fe concentration. Transfer factor (TF), which is the ratio of metal concentration in shoot to its concentration in root, of the studied HMs, was significantly affected by Cd and K treatments. Therefore, the proper form and dose of chemical fertilizers should be applied in Cd-contaminated soils.

Antioxidant activity and essential oil composition of Satureja hortensis L. as influenced by sulfur fertilizer.

BACKGROUND: The quantity and quality of essential oils in plants can be influenced by various factors, including genetic traits, agricultural practices and environmental conditions such as nutrient availability. Macronutrients such as sulfur (S) are among the major factors influencing plant growth and development. Therefore this study was carried out to determine the effect of S fertilization at three levels (0, 0.05 and 0.1 g S kg(-1) soil) on the essential oil composition and antioxidant activity of Satureja hortensis L. RESULTS: Application of 0.05 g S kg(-1) soil increased the levels of α-terpinene, p-cymene, myrcene, α-thujene and α-pinene but decreased the level of γ-terpinene in the essential oil. This S application was most suitable for obtaining higher proportions of α-terpinene, p-cymene, myrcene, α-thujene and α-pinene, while application of 0.1 g S kg(-1) soil was preferable for carvacrol. γ-Terpinene was most abundant in the control. All extracts showed a considerable DPPH-inhibitory effect, with IC50 ranging from 0.720 g L(-1) in the control to 0.363 g L(-1) with application of 0.1 g S kg(-1) soil. The maximum antioxidant effect was observed with application of 0.1 g S kg(-1) soil. CONCLUSION: The results revealed that the use of chemical fertilizers such as S could improve the antioxidant activity of plant extracts significantly. Studying the secondary plant metabolites, mainly essential oils, is an interesting research area, so further studies are recommended to determine the effect of chemical fertilizers on the composition and antioxidant activity of essential oils of other aromatic plants.