This study aimed to evaluate the concentration of heavy metals in liquid effluents and to quantify the mercury content in dental amalgam waste generated by dental clinics. Three neighbouring cities in Northeast Algeria were considered in this study (Constantine, Skikda, and Annaba). Heavy metals, such as Hg, Cu, Zn, Fe, Ni, Mn, Cr, Cd, and Pb, were analysed in wastewater and then compared with acceptable standard values. Special attention was given to mercurybecause of its dangerous effects. The results collected indicated the presence of heavy metal contamination in dental wastewater. Heavy metal concentrations were significantly high for all heavy metals and exceeded the allowed concentrations. However, Pb and Cr were shown to have acceptable concentrations. This study highlights the possible contamination of the environment by mercury and heavy metals generated by dental clinics. This study also demonstrates an order of magnitude of the concentration of these heavy metal in a large agglomeration with a population of 2.5 million people.

The impact of Industrialization has always been related to the better economic and social transformation. However, it should be well planned for environmental sustainability. Landfilling is the most used municipal solid waste (MSW) disposal method in Malaysia. Raw and treated leachate collected from Jerangau-Jabor Landfill Site (JJLS), Kuantan, Pahang were analysed for the content of silver, cadmium, chromium, copper, iron, lead, zinc using Flame Atomic Absorption Spectrometry (FAAS) and Inductively Coupled Plasma Mass Spectrometry (ICP-MS). The metal analyses result were compared with standard limits from the Environmental Quality (Control of Pollution from Solid Waste Transfer Station and Landfill) Regulations 2009, Malaysian Environmental Quality Act 1974 (Act 127) set by the Department of Environment, Ministry of Natural Resources and Environment, Malaysia and used to calculate the sub-leachate pollution index of heavy metals (sub-LPIhm) to evaluate the pollution potential of the heavy metals. The sub-LPIhm is one of the sub-index needed to calculate the Leachate Pollution Index (LPI) together with the sub-LPI organic (sub-LPIorg) and sub-LPI inorganic (sub-LPIinorg). LPI is the level of leachate pollution potential of a landfill site. All the heavy metals in the raw leachate were significantly higher than the treated leachate. Some were found to be above the permissible standard limit stipulated in the regulation. However, the sub-LPIhm showed that the level of heavy metal pollution potential of the leachate is low. It is recommended that the treated leachate should undergo continuous treatment to ensure the discharge leachate complied with the standard limit.

The main objective of this study is to evaluate heavy metals contamination of highly consumed vegetables and hazardous effects of consuming these vegetables. The study was conducted in vegetable fields in three different regions according to the level of environmental pollutions, including "Isfahan", "Flavarjan" and "Faridan, Golpayegan and Natanz". Six types of vegetables in each field with three replicates in each region were selected in the summer of 2017 by the random sampling method from vegetable fields. The level of heavy metals (Pb, Cu, Co, Cd and Cr) in vegetables has been measured for each sample. The result showed that in the Isfahan region, the highest daily intake of Pb, Cu, Co, Cd and Cr for the consumption of all the vegetables was obtained in the recipients. The highest target hazard quotient for non-cancerous diseases of contaminated vegetables was 28.9 and 21.1 in "Isfahan" for children and adults, respectively. The target hazard quotient for vegetable consumption was greater than one and at high hazard for both age groups. The principal component analysis showed that the contamination by the heavy metals in the "Isfahan" and "Falavarjan" regions overlapped and the risk of contamination of heavy metals in urban vegetables in both regions increased the hazard of non-cancerous diseases. It is highly recommended that the quality standards of foods that are imposed on the production of food crops.

In the present study, size-segregated samples of PM were collected from urban and semi-urban traffic junctions in Agra, India. PM samples were collected during the monsoon season (July to September 2015) using Grimm portable aerosol Spectrometer. The recorded mean concentration of PM10 at urban site was 137.09±61μg/m3 and at semi-urban site was 270.14±21μg/m3, which were higher than the suggested limits by WHO and NAAQS India. Mean concentrations of PM2.5 were 41.45±40μg/m3, 48.88±34μg/m3 at the urban and semi-urban site, respectively. Whereas, mean concentrations of PM1.0 were 30.35±64μg/m3, 12.64±4μg/m3 and PM0.25 were 0.06±0.05μg/m3, 0.17±0.06μg/m3 at the urban and semi-urban site, respectively. It was estimated that PM10, PM2.5 and PM0.25 values were higher at semi-urban site than urban sampling site but in case of PM1.0 concentrations were higher at urban site. The surface morphology of PM2.5 was studied using Scanning Electron Microscope (SEM). The results show flaky, branched chain like aggregates of carbon bearing spheres at the urban site while cluster, branched, spherical and fluffy particles at semi-urban site. The presences of carbonaceous particles were enhanced due to use of fuel combustion. Chemical analysis was done using ICP-AES. Concentrations of Zn and Cu were found higher while Ni was least in comparison to other metals. Elemental composition present in PM2.5 was used to calculate the health risk assessment to identify the possible health effect on human health, hazards quotient (HQ) values was found higher as Ingestion to inhalation pathways while ECR values found higher as Cr(VI)>Ni>Pb for both medium (Air and Dust).

The present study tries to investigate the effect of composting process on some properties and heavy metals status of two municipal sewage sludge (MSS) as affected by three different organic bulking agents (BAs) at three levels (10%, 25%, and 45% V/V). According to the results, the composting process could reduce the fecal coliform to class A, a reduction more obvious in treatments with BAs than produced composts without them. Changes in the chemical properties of the composts vary according to the type of MSS and Bas. Based on the compost quality standard, most of the produced samples are classified in compost-class II. Examination of the total form of three heavy metals (HMs: Zn, Ni, Fe) of both MSS shows that composting process without BAs increases the HMs total concentration, but using of BAs have not been clear trends. In the contrary, BAs application reduced the available form of Fe and Ni, but increased the Zn available form. Examination of chemical forms of each studied HMs also shows that the composting process reduces the Ni and Fe mobility factor, but increases that of Zn. Generally, while, prepared composts can classify into the compost-class II, based on their properties, the high concentration of total Zn above the standard limit makes it extremely restrictive to be used as class II compost. However, according to EPA regulations, the composts with this concentration of Zn can be used as a relatively safe organic material on agricultural land.

In order to investigate the accumulation and bio-absorption of lead and cadmium in radish and cress, the present study has been conducted in a completely randomized design in three replicates in a hydroponic growing medium. The first factor includes the plant type at two levels (radish and cress), and the second factor is consisted of lead (Pb) (first experiment) at two levels (50 and 100 mg/L), cadmium (Cd) (second experiment) at one level (10 mg/L), and a combination of lead and cadmium (third experiment) again at two levels. After 23 days, roots and aerial parts of both plants have been dried for 48 hours at 70°C in an oven. Then, half gram (0.5 g) of the dried templates has been used to measure the accumulation of Pb and Cd by means of an atomic absorption spectrometer. The highest amount of Pb in radish and crest roots belong to 100 mg/L concentration and the combined Cd (10) + Pb (100) mg/L treatment, respectively, and the highest amount of Cd occurs in Cd (10) + Pb (50) for radish roots and in Cd (10) + Pb (100) combination for cress. Moreover, the Translocation Factor (TF), with a value below 1 and higher bio-concentration factor (BCF) in roots, compared to the aerial part of both radish and cress, seem to be due to the low capability of these plants to transfer Pb and Cd from roots to aerial part. There is a high potentiality for lead accumulation in the roots that prevent its transfer to the aerial part.

Industrial activities compromise the ambient air quality at a local, regional and global level through gaseous and dust emissions. This study reviews uptake mechanisms and the associated phytotoxicity of pollutants in plants, focusing on heavy metals and SO2. It further describes detoxification mechanisms and the resultant biochemical and physiological changes in plants. Finally, the morpho-physiological and growth responses to stress-induced biochemical changes are discussed. Heavy metals and SO2 enter the plant tissue through the stomata, cuticular layers, lenticels and root hairs. In the plant cells, SO2 converts to SO32- or SO42- ions upon reacting with water molecules, which in excess are toxic to plants. However, the detoxification process of SO32- increases the production of reactive oxygen species (ROS). ROS are toxic to plants and damages biomolecules such as lipids, proteins, carbohydrates and DNA. On the other hand, heavy metals, such as Cu and Fe catalyse the Fenton/Haber-Weiss reactions, breaking down H2O2 into OH•. Additionally, Pb and Zn inhibit the activities of ROS-detoxifying enzymes, while other heavy metals bind to cellular layers making them rigid, thereby reducing cell division. Therefore, pollutant toxicity in plants affects biochemical parameters damaging organic molecules and limiting cambial activity. Damaged biomolecules inhibit the plant's capacity to carry out physiological functions, such as photosynthesis, stomatal functions, transpiration and respiration while impaired cambial activity reduces cell division and elongation resulting in reduced plant growth and productivity.

The prediction and identification of the factors controlling heavy metal transfer in soil-crop ecosystems are of critical importance. In this study, random forest (RF), gradient boosted machine (GBM), and generalised linear (GLM) models were compared after being used to model and identify prior factors that affect the transfer of heavy metals (HMs) in soil-crop systems in the Yangtze River Delta, China, based on 13 covariates with 1822 pairs of soil-crop samples. The mean bioaccumulation factors (BAFs) for all crops followed the order Cd > Zn > As > Cu > Ni > Hg > Cr > Pb. The RF model showed the best prediction ability for the BAFs of HMs in soil-crop ecosystems, followed by GBM and GLM. The R2 values of the RF models for the BAFs of Zn, Cu, Cr, Ni, Hg, Cd, As, and Pb were 0.84, 0.66, 0.59, 0.58, 0.58, 0.51, 0.30, and 0.17, respectively. The primary controlling factor in soil-to-crop transfer of all HMs under study was plant type, followed by soil heavy metal content and soil organic materials. The model used herein could be used to assist the prediction of heavy metal contents in crops based on heavy metal contents in soil and other covariates, and can significantly reduce the cost, labour, and time requirements involved with laboratory analysis. It can also be used to quantify the importance of variables and identify potential control factors in heavy metal bioaccumulation in soil-crop ecosystems.

Soil contamination in urban environment by trace metals is of public concerns. For better risk assessment, it is important to determine their background concentrations in urban soils. For this study, we determined the background concentrations of 9 trace metals including As, Ba, Cd, Co, Cu, Ni, Pb, Se, and Zn in 214 urban soils in Florida from two large cities (Orlando and Tampa) and 4 small cities (Clay County, Ocala, Pensacola and West Palm Beach). The objectives were to determine: 1) total concentrations of trace metals in urban soils in cities of different size; 2) compare background concentrations to Florida Soil Cleanup Target Levels (FSCTLs); and 3) determine their distribution and variability in urban soils via multivariate statistical analysis. Elemental concentrations in urban soils were variable, with Pb being the highest in 5 cities (165–552 mg kg⁻¹) and Zn being the highest concentration in Tampa (1,000 mg kg⁻¹). Besides, the As and Pb concentrations in some soils exceeded the FSCTL for residential sites at 2.1 mg kg⁻¹ As and 400 mg kg⁻¹ Pb. Among the cities, Clay County and Orlando had the lowest concentrations for most elements, with Cd, Co, and As being the lowest while Ba, Pb and Zn being the highest. Among all values, geometric means were the lowest while 95th percentile was the highest for all metals. Most 95th percentile values were 2–3 folds higher than the GM data, with Pb presenting the greatest difference, being 4 times greater than GM value (58.9 vs. 13.6 mg kg⁻¹). Still they were lower than FSCTL, with As exceeding FSCTL for residential sites at 2.1 mg kg⁻¹. In addition, the linear discriminate analysis showed distinct separation among the cities: Ocala (Ba & Ni) and Pensacola (As & Pb) were distinctly different from each other and from other cities with higher metal concentrations. The large variations among elemental concentrations showed the importance to establish proper background concentrations of trace metals in urban soils.

In recent years, with the expansion of the Weining county in the northeast of Caohai wetland, the construction of a new port in the north, and the large-scale development of cultivated land in the east, land use patterns in lakeshore areas have changed. These changes have affected the state of lake shores water bodies in complex ways, resulting in varying degrees of local water pollution. To explore the distribution and transformation characteristics of water chemistry and heavy metals in different areas of a water body under the influence of different land uses, especially the interactions between water chemical factors and heavy metals in different areas of a water body, this study used Circos diagrams, originally used in biological genetic analysis, to visualize these interactions. This is the first time that the Circos diagram has been applied to the analysis of environmental interactions. The results showed that there are significant differences in the distribution of water chemical factors and heavy metals in different areas of the Caohai wetland. In particular, Cd is affected by anthropogenic sources. The Cd content is higher in the NCL and UL areas, which are at greater risk from pollution. The factors controlling heavy metal levels in water bodies were different in the different regions. The NCL region was mainly affected by construction excavation ore, UL was mainly affected by man-made industrial inputs, CL was mainly affected by pesticide and fertilizer inputs, and ML and FL were mainly affected by Eh and DO. The PCA results showed that the sources of heavy metals in different types of water bodies in the lakeshore zone were both natural and anthropogenic. Therefore, controlling pollutants, reducing environmental pollution inputs to the lakeshore zone, and strengthening supervision and management near wetlands may be of great significance for handling heavy metal pollution.