Assessment of the application of two amendments (lime and biochar) on the acidification and bioavailability of Ni in a Ni-contaminated agricultural soils of northern Colombia

Soil acidification and increased bioavailability of Ni are problems that affect agricultural soils. This study aims to compare the effects of both lime and biochar from corn stover in soil acidity correction, improving soil physicochemical properties and soil re-acidification resistance. As well as assesseing the impacts on human health risk caused by bioavailability of nickel. A greenhouse pot experiment was conducted for 30 days to determine the effect of biochar and lime on soil physicochemical properties and nickel bioavailability. Afterwards, a laboratory test was carried out to determine the repercussions of both amendments on soil resistance to re-acidification and re-mobilization of nickel. Human health risk was determined using nickle bioavailable concentration. Overall, the results of this study showed that biochar application significantly reduced soil acidity from 8.2 ± 0.8 meq 100 g⁻¹ to 1.9 ± 0.3 meq 100 g⁻¹, this reduction markedly influenced the bioavailability of nickel, which decreased significantly. Moreover, soil physicochemical properties and soil resistance to acidification were improved. Furthermore, biochar significantly reduced human health risk compared to lime application, even under a re-acidification scenario. It was possible to verify that Ni immobilization in the soil was increased when biochar was used. Soil Ni immobilization is associated with co-precipitation and chemisorption. Hence, it was demonstrated that biochar is more effective than lime in reducing soil acidity and remedying nickel-contaminated agricultural soils.

Pollution characteristics, sources and health risk of metals in urban dust from different functional areas in Nanjing, China

Urban dust is an important medium of potential toxic metal (PTM) pollution that affects human health and the urban ecosystems. A total of 374 fugitive dust samples were collected in Nanjing, a fast-developing city in southern China, including six sub-types of dust (residential district, commercial district, industrial district, traffic district, cultural and educational district, green land). Chemical analysis of eighteen metal elements by inductively coupled plasma mass spectrometry was carried out to establish the sub-type sources profiles of fine particles for fugitive dust. The results show that these metals (Cu, Zn, Se, Sr, Mo, Cd, Sb, and Pb) are mainly from anthropogenic sources and present a high degree of pollution; Mn, As, and Ba are moderately affected by human activities and present a significant degree of pollution; Ni, Co, Cr, Tl, V, Be, and Ti mainly originate from natural sources and present significant, moderate and minimal degrees of pollution. For the dust types from different functional areas, the differences of enrichment factor (EF) values were relatively small. Metals were highly concentrated in dust from residential, cultural and educational district, which had high density population and would pose higher health risk. In all types of dust, the metals rich in crust (Ti, Mn, Ba, Sr) and the metals (Cu, Zn, Pb) closely connected with city activities were the main components. Factor analysis revealed that there were six main sources of metals in dust collected from Nanjing: industrial activity, building decoration, soil dust, metal smelting, traffic emissions, and brake abrasion. Generally, noncarcinogenic and carcinogenic health risks of metals found in dust are rarely found for children and adults based on health risk assessments. However, the noncarcinogenic risk of Pb in commercial districts for children should be noted because its hazard quotient was higher than the safety threshold level. For the accumulative health risk of eighteen metals, the noncarcinogenic risk values of dust from six functional areas for children were all over the threshold (1.0), whereas below 1.0 for adults. The difference between children and adults was relatively obvious. All accumulative risk values of carcinogenic metals did not exceed the carcinogenic risk threshold of 1 × 10^-4, which suggested that no risk prevention measures were needed.

Potential toxic metals (PTMs) contamination in agricultural soils and foodstuffs with associated source identification and model uncertainty

The research aimed to find out physiochemical properties, metal concentration, sources of metals using statistical analyses, and positive matrix factorization (PMF) model using 315 soil and 250 foodstuff samples (25 species) in Jhenidah as well as Kushtia district, Bangladesh. The range of Pb, Cd, As, Cu, Ni and Cr contents (mg/kg) in soils were found to be 0.97-114.72, 0.11-7.51, 1.07-23.38, 0.89-122.91, 0.91-77.32 and 0.7-23.03 mg/kg, respectively, whereas those in foodstuff samples were found to be 0.46-11.48, 0.30-11.54, 0.47-9.21, 0.20-3.59, 0.001-1.76, and 0.27-5.93 mg/kg, respectively. PMF model revealed that Cu (81.4%) in the study area soils were predominantly contributed by vehicular fuel combustion, Cr (84.9%) was primarily of natural origin, Pb (73%) resulted from traffic emissions, Cd (74.3%), and As (63.4%) mainly came from agricultural practices while Ni (70.9%) was dominated as industrial pollution. EF > 1.5 of Cu, As, and Pb suggesting mild contamination; however, soils from all the studied sites revealed moderate potential ecological risk. Cr recorded BCF values of >1 in the majority of the examined crops, suggesting higher uptake of Cr than other metals. Cr, Ni, As, and Pb showed cancer risks from food intake and risk values were greater than the threshold range (10^-4), suggesting potential cancer risks.

Ecological and human health risk evaluation of potential toxic metals in paddy soil, rice plants, and rice grains (Oryza sativa) of Omor Rice Field, Nigeria

Potential toxic metals from natural and anthropogenic sources accumulate in soil and plants, and represent important environmental contamination challenges. The ecological and human health risks of the potential toxic metals in rice grain, paddy soil, and rice plants of Omor rice field were assessed. The total metal concentration from the four sampling sections (mg/kg) were soil-Zn (29.51 ± 2.23), Mn (55.27 ± 8.10), Cd (5.49 ± 2.24), Cu (2.94 ± 1.47), Pb (14.35 ± 6.54), and Cr (27.06 ± 8.31); rice grain-Zn (21.70 ± 5.44), Mn (3.30 ± 0.21), Cd (00.14 ± 0.11), Cu (2.80 ± 0.34), Pb (11.98 ± 0.58), and Cr (15.86 ± 2.79); and for rice plant-Zn (5.24 ± 1.93), Mn (4.68 ± 1.91), Cd (0.21 ± 0.11), Cu (4.88 ± 0.61), Pb (15.24 ± 6.16), and Cr (46.5 ± 6.05). The estimated daily intakes for adult showed that Cd and Pb exceeded the safe limit by 1% and 93%, respectively. The metal hazard quotients (Zn-0.0007, Mn-0.00019, Cd-0.16, Cu-0.19, and Cr-0.0000077) were less than 1 indicating no probable health risk originating from their exposure. The total hazard index (0.35) also suggests no probable health risk connected with the rice consumption. The metals' ecological risk indices of the soil showed low-risk (< 40), except Cd in some sections of the rice field which indicated moderate potential ecological risk (40-80).

Sources evaluation, ecological and health risk assessment of potential toxic metals (PTMs) in surface soils of an industrial area, India

The present study aims to appraise the spatial distribution of potential toxic metals by using geostatistical technique and find their associated ecological and human health risks from surface soils of Durgapur industrial area, India. The results show that the mean metal concentrations are 116.03, 32.96, 154.37, 321.20, 50.08, 29.54 and 2.97 mg/kg for Pb, Cd, Cr, Fe, Cu, Ni and Hg, respectively, and majority of them is found higher than their background and world natural soil concentrations. The GIS contour map of pollution load index values clearly distinguished the studied sampling area is highly to very highly polluted by the toxic metals. Contamination factor (C_f) and geo-accumulation index (I_geo) values of studied metals show a similar sequence of Hg > Cd > Pb > Fe > Cr > Ni > Cu. Calculated enrichment factor (EF) value for Hg (13.29), Cd (5.26) and Pb (1.11) in studied soils was found significantly higher, which suggests that their primary sources are higher industrial activities in the studied area. Computation of potential ecological risk index reveals that the entire study area is under high risk level (1941.60-3367.23), in which Cd (588.52) and Hg (1979.26) possess the maximum ecological risk factor in all the sampling sites. The results of correlation analysis, principle component analysis and cluster analysis explore that industrial discharges, atmospheric disposition and waste disposal are the major sources of soil metal pollution in the studied region. Human health hazard indices are lower than 1 for all metals, indicating low non-carcinogenic risks to children and adults. Carcinogenic risk assessment reveals the existence of cancer risk of Cd (5.5E-03), Cr (8.6E-04) and Ni (3.0E-04) to child and Cd (8.2E-04) and Cr (1.3E-04) to adults in Durgapur.

Quantification and risk assessment of heavy metal build-up in soil-plant system after irrigation with untreated city wastewater in Vehari, Pakistan

In peri-urban areas of district Vehari, farmers are using untreated city wastewater for crop irrigation owing to the scarcity of good-quality irrigation water. This practice may pose severe environmental and health issues to local inhabitants attributed to the high levels of potentially toxic metals in wastewater. The present study evaluated the potential impacts of wastewater irrigation on metals (Cd, Cr, Cu, Fe, Ni, Mn, Pb and Zn) build-up in the soil-plant continuum and associated health risks. In this study, wastewater (n = 17), soil (n = 108) and plant (n = 65) samples were collected from 15 peri-urban sites of three tehsils of district Vehari. Results showed that the mean concentration (mg/L) of Cd (0.02), Mn (0.25) and Fe (1.57) in wastewater samples was higher than their respective threshold values. Similarly, Cd, Mn and Fe concentration in soil was beyond the permissible limits of agricultural soil receiving wastewater irrigation. However, plants showed high accumulation of Pb, Cr and Fe than their respective limits depending on the vegetable/crop species. The health risk parameters showed that Pb and Cd are the major toxic chemical substances to human health, and the daily intake of crop plants can pose a potential health threat due to wastewater-irrigated crop consumption. Results highlighted the necessity of wastewater pretreatment to avoid the soil and vegetable contamination by wastewater irrigation and to reduce the associated health risks.

A pediatric health risk assessment of children's toys imported from China into Nigeria

Trade liberalization led to the flooding of the Nigerian markets with ''made in China'' children's toys. Information about metal contamination in toys is vital to ensure the safety of children's product. This is a pediatric health risk assessment of three toxic metals (Pb, Cd and As) in children toys purchased from Nigerian market. Thirty cheap ''made in China'' toys were purchased from stores in Port Harcourt, Nigeria. Three toxic metals (Pb, Cd and As) in the thirty toys samples were determined by absorption spectrophotometry. Pb, Cd and As were present in all the toys at levels below the limits set by EU. The oral and dermal exposure risk assessment showed no significant non-carcinogenic and carcinogen health risks of public health concern. Some ''made in China'' toys imported into Nigeria may not add to the body burden of these metals in children.

Contamination of soil with potentially toxic metals and their bioaccumulation in wheat and associated health risk

The present study was conducted to investigate the concentrations of potential toxic metals (PTMs) in agricultural soil (n = 25) and their bioaccumulation in wheat crop (n = 25) collected from alongside the Kurram River, Pakistan. The highest concentrations of Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn in soil samples were 0.16, 19.5, 14.7, 46.5, 13.5, 14.5, 14.0, and 19.7 mg kg^-1, respectively. In the edible tissues of cultivated wheat crop, the highest concentrations of Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn were 0.15, 10.00, 8.75, 22.25, 11.00, 11.25, 10.50, and 7.50 mg kg^-1, respectively. The selected PTM concentrations in soil samples were observed within their respective permissible limits set by the Food and Agriculture Organization (FAO) and State Environmental Protection Administration (SEPA) China, while in wheat crops, the Cr and Pb concentrations were above the permissible limits of both FAO and SEPA China. The results showed that the orders of PTMs were Fe > Zn > Cr > Cu > Ni > Pb > Mn in soil and Fe > Ni > Mn > Pb > Cr > Cu > Zn in wheat. The highest PTM concentrations were reported in the sample collected near dumping sites. The results of different soil pollution indices including geo-accumulation index (Igeo), contamination factor (CF), and enrichment factor (EF) indicated that the soil of the study area was moderately to severely contaminated. The ADI values of wheat crops were less than 1, while the HQ varied among different PTMs with the highest value of 2.118 for Pb, and the lowest for Zn (0.007). The results indicated that anthropogenic intervention has made a substantial contribution to soil contamination with PTMs and subsequent uptake by wheat, which may exert potential human health risk.

Investigation of a combined continuous flow system for the removal of Pb and Cd from heavily contaminated soil

In this study, a combined continuous flow system was designed to remove Pb and Cd from heavily contaminated mine tailing soils. 0.05 M Na₂EDTA was used as a chelating agent to remove Pb and Cd from polluted soil, taken from the vicinity of Kayseri ÇİNKUR, Turkey. The initial concentrations of Pb and Cd were 16381 ± 643 and 34347 ± 1310 mg kg^-1, respectively. The electrochemical treatment process was applied to the waste washing solution, which emerged after being extracted from soil column and contained Pb and Cd. Metal ions were transformed to the metallic form by applying the electrochemical treatment process to the washing solution, containing Pb²⁺ and Cd²⁺. At the end of the leaching experiment, which was done with a 50 g soil sample in the soil column system, Pb and Cd removal efficiencies from soil were 59.72% and 58.01%, respectively. Then, the soil column solution was subjected to electrolysis through a 48 h period at 10 V. The electrochemical removal efficiency of ions, which moved from column to solution, was 84.46% for Pb and 59.21% for Cd.

Candy consumption may add to the body burden of lead and cadmium of children in Nigeria

The affordability of candies and chocolates makes their consumption common especially in children. Heavy metal contamination of these candies is well known. This study has estimated health risks associated with heavy metals (HM; Pb, Cd, Cr, Ni, and Zn) in commonly consumed candies in Nigeria. Fifty candies/sweets and chocolates/chewing gums bought from different stores in Port Harcourt and Uyo in Niger Delta, Nigeria, were processed and digested in perchloric acid. The filtrate was analyzed for these heavy metals using atomic absorption spectroscopy (AAS). Pb/Zn and Cd/Zn ratios were calculated. Daily intake, the target hazard quotient (THQ), the hazard index (HI), and the cancer risk were estimated for children. About 80% of the samples exceeded the 0.1 mg/kg permissible lead level in candies. Milk sweet had the highest Pb:Zn and Cd:Zn ratios of 0.99 and 0.40 respectively. For chocolates, the Emperor had the highest Pb:Zn (0.50) ratios and Trident had the highest Cd:Zn (0.57) ratios. The calculated percentage provisional tolerable weekly intake (%PTWI) of cadmium from consumption of chocolates and candies was higher than the Joint Expert Committee for Food Additives (JECFA) standard, and the cancer risk of lead, cadmium, and chromium ranged between 10^-7 and 10^-3. Consumption of some candies by children in Nigeria may pose significant health risks.