Ecological and human health hazards of soil heavy metals after wildfire: A case study of Liangshan Yi autonomous prefecture, China.

Soil samples were collected in at different depths from the conflagration area in Liangshan Yi Autonomous Region, China, to investigate the distribution characteristics and ecological and human health risks of heavy metals after a wildfire. The samples collected comprise wildfire ash (WA) above the soil surface, ash soil (AS) 0-5 cm, and plain soil (PS) 5-15 cm below the soil surface. Additionally, reference soil (RS) was collected from a nearby unburned area at the same latitude as the conflagration area. The results showed that the concentrations of zinc (Zn), copper (Cu), lead (Pb), and cadmium (Cd) in the WA and AS were significantly higher than in reference soil (RS) (p < 0.05). Concentrations of Pb in the PS were 2.52 times higher than that in RS (17.9 mg kg-1) (p < 0.05). The AS and WA had the highest Index of potential ecological risks (RI > 600). In addition, The Cd in AS and WA contributed the most to the highest Improved nemerow index (INI) and RI with a contribution of more than 80%. The concentration of heavy metals was used to establish non-carcinogenic effects and cancer risks in humans via three exposure pathways: accident ingestion of soil, dermal contact with soil, and inhalation of soil particles. Hazard index (HI) values of each sample were all less than 1, indicating the non-carcinogenic risk was within the acceptable range and would not adversely affect the local population's health. The Cancer risk (CR) values of Cr, As, Cd, and Ni were all below 1 × 10-6, indicating that heavy metal pollution from this wildfire did not pose a cancer risk to residents.

Selenium toxicity and bioaccumulation in selenium-enriched fly (Chrysomya megacephala) maggots.

Selenium (Se) is an essential trace element for human health, and as a potential animal feed, the Chrysomya megacephala (Fabricius) fly is rich in protein and fat. By using different concentrations of sodium selenite (0, 30, 50, 70 mg kg-1), the possibility of biological Se enrichment in C. megacephala (Fabricius) maggots (CMMs) was investigated. The accumulation, Se speciation, enzymatic activity, and concentrations of copper (Cu), zinc (Zn), chromium (Cr), and cadmium (Cd) in the maggots were also determined. Transcriptomics was also used to investigate the mechanism of the Se response to CMM genes. The results showed that the CMMs had a survival rate of > 80% at Se exposure concentrations ranging from 0 to 100 mg kg-1. The optimal concentration of sodium selenite for CMM growth was 50 mg kg-1, and the weight, protein content, and total Se accumulation of the larvae (10.8 g, 53.5%, and 72.6 ± 3.36 mg kg-1 (DW), respectively) were considerably higher than the control and other exposure doses (p < 0.05). In addition, Se improved the ability of maggots to absorb Cu and Zn, decreased malondialdehyde (MDA) and lipid peroxidation, but improved the antioxidant activities of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPX). Furthermore, Se negatively affected the absorption of Cd and Cr. According to the transcriptomic findings, Se supplementation can boost protein synthesis and control both antioxidant and non-antioxidant enzyme activity in CMMs. Therefore, our findings showed that Se-enriched CMMs may counteract the toxicity of Cd and Cr, and Se is an effective supplement for improving the consumption safety of cultured animals fed containing CMMs.

Using fly larvae to convert food waste for growing Oujiang color common carps: health risk assessment of polycyclic aromatic hydrocarbons.

The present study used Chrysomya megacephala larvae (CML) to transform food waste into safe and high-quality fish feed to substitute fish meal as a source of protein for growing Oujiang color common carps followed by a human health risk assessment of polycyclic aromatic hydrocarbons (PAHs). The results showed the ∑PAH concentration in the CML fed with food waste ranged from 50 to 370 µg kg-1, and the most abundant PAH compound in the CML was BaP, contributing 59-84% of ∑PAHs. The Pearson correlation analysis results indicated no correlation between the ∑PAH concentrations and the culture substrate ratio (p > 0.05). Concentrations of BaP in the CML decreased with the increase of breeding density (p < 0.01). The residues as organic fertilizers have no potential ecological risk for PAHs. The biotransformed larva meal was used to partially or completely replace the fish meal as supplementary protein in the experimental feeds (T0, 0%; T50, 50%; T100, 100%). No significant difference (p < 0.05) of survival rate, lipid, and protein content in Oujiang color common carp was noted among T0, T50, and T100 fish feeds. Concentrations of ∑PAHs in Oujiang color common carp fed with the CML fish feeds all met the food safety standards in the European Union (EU). Furthermore, the consumption of Oujiang color common carps fed with the CML feed does not pose any health risks of PAHs for humans.

Assessing the risk of human exposure to bioaccessible arsenic from total diet through market food consumption in Chengdu, China.

To assess the daily intake of total arsenic (tAs) and arsenic speciation and their potential health risks, different food groups, including vegetables, rice, meat, viscera, freshwater fish, and seafood from Chengdu, China were analyzed. The concentrations of tAs ranged from 41.3 to 1185 µg kg-1 with a median of 238 µg kg-1, and 26.0% of tAs in the food groups was of inorganic toxic form. The median concentration of As(V) in rice (184 ± 21.6 µg kg-1) was approximately 2 to 6 times higher than those in other food groups. The bioaccessible inorganic arsenic (iAs) concentrations of the food items obtained from the local markets of Chengdu ranged from 1.07 to 24.6 µg kg-1 (mean of 6.04 µg kg-1). Rice contributed toward the largest amount of daily iAs intake (66.2%). The mean daily iAs intake from vegetable, meat and viscera contributed 10.7%, 12.5% and 6.04% of total iAs intake, respectively. The actual concentration of arsenic in the food exposed to the human body depends on oral bioaccessible fraction. The oral bioaccessibility estimated daily intake (µg kg-1 bw d-1) of tAs and iAs for the residents of Chengdu was 0.32 and 0.16. Health risk assessments carried out based on bioaccessible iAs concentrations showed that the food items were safe for consumption from the iAs perspective.

Health risk assessment of mercury in Nile tilapia (Oreochromis niloticus) fed housefly maggots.

The bioaccumulation of total mercury (THg) and methylmercury (MeHg) by housefly maggots (HM) during the conversion of food waste (vegetables and meat (VM) and rice waste) under various waste feed ratios were investigated. Subsequently, Nile tilapia (Oreochromis niloticus) were fed with the commercial feed, commercial dried HM, dried HM, and fresh HM, followed by a human health risk assessment of Hg via fish consumption. The THg concentrations of HM fed with food waste ranged from 39.5 to 100 µg kg-1 ww. Concentrations of MeHg in the maggots fed with 100 % vegetables and meat (VM) waste (13.7 ± 1.12 µg kg-1 ww) was significantly higher than that fed with other mixed ratios of rice waste and VM waste (p<0.05). Concentrations of MeHg were positively correlated with the weight and lipid content of houseflies (p<0.05). THg and MeHg concentrations in tilapia fed with the converted HM (dried and fresh HM) were 22.5 ± 6.50 µg kg-1 ww and 2.43 ± 0.36 µg kg-1 ww, respectively. There was no significant difference in MeHg between tilapia fed the four experiment diets (p>0.05). Health risk assessment results indicated that mercury in tilapia fed the food waste-grown HM did not pose potential health risks to humans (target hazard quotient < 1). In conclusion, HM could convert food waste into high-quality and safe fish feeds for cultivating tilapia.

[Remediation Potential of Taraxacum kok-saghyz Rodin on Lead and Cadmium Contaminated Farmland Soil].

Taraxacum kok-saghyz Rodin (TSK) is an energy plant that can be used as a raw material for natural rubber. The aim of this study was to examine the remediation potential of TSK to lead (Pb)- and cadmium (Cd)-contaminated farmland soil. In this study, a pot experiment was conducted, and the "Soil Environmental Quality and Agricultural Land Soil Pollution Risk Control Standard (GB 15618-2018)" was used as reference. We set up four different concentrations of Pb and Cd pollution treatment to study the characteristics of the accumulation and tolerance of TSK to Pb and Cd. The results showed that as the content of Pb and Cd in the soil increased, the chlorophyll content and biomass of TSK gradually decreased, and the SOD, POD, and CAT enzyme activities gradually increased. The BCF and TF of Cd were between 1.20 and 1.50, indicating that TSK presented some characteristics of a Cd hyperaccumulator. The BCF and TF of Pb were between 0.71 and 1.11. Thus, TSK was a good Pb enrichment plant and possessed the potential to repair soil with ω(Pb) below 400 mg·kg-1. The accumulation of Pb and Cd gradually increased, and the maximum accumulation of Cd and Pb in the shoots was 9.832 µg·plant-1 and 1091.185 µg·plant-1, respectively. However, in lower concentrations of Pb- and Cd-contaminated soil, the removal rate was greater, and the remediation efficiency was better. Overall, using TSK to repair Pb- and Cd-contaminated farmland soil has good application prospects and economic value.

Polycyclic aromatic hydrocarbons in street dust from different functional areas in Chengdu, China: seasonal variation and health risk assessment.

This is the first investigation that identified seasonal variation, possible sources and health risk of 16 PAHs in street dust sampled park area (PA), educational area (EA), commercial area (CA), residential area (RA), and traffic area (TA) of Chengdu, one of the new first-tier cities in China. The total PAHs (∑16PAHs) concentrations of averaging over two seasons varied from 2.15 to 10.6 mg/kg with a median value of 4.61 mg/kg and in winter (5.48 ± 1.52 mg/kg) were significantly higher than that in summer (4.04 ± 0.91 mg/kg). The highest ∑16PAHs concentration was found in TA (median 6.74 mg/kg). Statistical analysis results indicated that mixture sources of petroleum combustion and combustion of biomass and coal seem to be the primary source of the PAHs in street dust. Carcinogenic risk by incremental lifetime cancer risk (ILCR) model for PAHs in street dust indicates an acceptable potential cancer risk for residents. The same sequences of cancer risk to be observed for both children and adults among different functional areas: TA > CA > EA > RA > PA. The results provided advice for habitants in Chengdu to encourage outdoor activities in parks and residential areas and minimize traffic areas and commercial areas.

Bioaccumulation and health risk assessment of phthalate esters in cultured low trophic level fish feded with food waste-based diets.

The present study aimed at using different types of food waste as a protein source for the fish feeds to produce safe and quality fish. The results showed the concentrations of ∑PAEs in grass crap (0.24 µg g-1 ww) and bighead carp (0.15 µg g-1 ww) fed with Food waste B feeds (mainly containing fruit, vegetable and cereal waste) was significantly lower than those fed Food waste A feeds (mainly containing meat waste) and control feeds (p<0.05), and the highest ∑PAEs concentration (1.75 µg g-1 ww) was found in the mud carp fed with control feeds in experimental ponds (p<0.05). In addition, there was no biomagnification of PAEs in the food chains within the ponds. The health risk assessment results showed no non-carcinogenic and carcinogenic risks from the PAEs via ingestion of the fish fed with food waste feeds for the local residents.

Bioaccumulation and health risk assessments of trace elements in housefly (Musca domestica L.) larvae fed with food wastes.

This study aimed to use food waste to culture housefly larvae, which serve as the major source of protein in fish feeds, to evaluate copper (Cu), zinc (Zn), iron (Fe), nickel (Ni), cadmium (Cd), and chromium (Cr) bioaccumulation and trophic transfer in the food chain. In addition, the potential health risk to humans of exposure to these metal elements via dietary intake of tilapia fed with housefly larvae feeds was also evaluated. The results showed the bioavailability of trace elements in dish waste to housefly larvae was lower than that in staple food waste. Trace element concentrations in housefly larvae fed with food waste met the animal feed standards in China and the European Union (EU). The highest concentrations of Cu, Zn, Ni, Cr, and Cd in residue did not exceed the limits specified for fertilizer in China, Canada, and Germany. The tilapia fed with dried housefly larvae presented a greater final weight and protein content than those fed with commercial feed and fresh housefly larvae (p<0.05). The Cu, Cr, and Cd concentrations in tilapia fed with commercial feed were higher than in those fed with commercial housefly larvae or dried housefly larvae (p<0.05). The highest bioaccumulation of Cu, Zn, and Ni was found in tilapia fed with fresh housefly larvae feed. The results of the health risk assessment showed that the tilapia fed with the housefly larvae feed pellets or fresh housefly larvae were safe for consumption from the perspective of trace elements.

Occurrence and distribution of phthalate esters in freshwater aquaculture fish ponds in Pearl River Delta, China.

The concentrations, congener profiles and spatial distribution of 13 phthalate esters (PAEs) in the freshwater fish ponds in the Pearl River Delta (PRD) region were investigated in water and sediment samples collect from 22 sites during Jul. 2016-Sept. 2017. The di-2-ethylhexyl phthalate (DEHP) was the predominant compounds in both water and sediment samples, accounting for 70.1% and 66.1% of ∑PAEs, respectively. The DEHP concentrations in the water samples collected from the sites of Zhongshan (35.7 µg/L), Jingmen (17.3 µg/L) and Nanhai (14.2 µg/L) were higher than that collected from other sampling sites (p <0.05), and exceed the Chinese environmental quality standards for surface water (DEHP, 8.00 µg/L). The concentrations of ΣPAEs (mean and median were 11.8 mg/kg dw and 7.95 mg/kg dw) in sediment was higher than that in sediment of river and estuary in the PRD region (p <0.05). The median concentrations of DEHP and di-n-butyl phthalate (DBP) exceeded recommend environmental risk limit (ERL) that posed a potential risk to the aquaculture fish pond environment in the PRD.

Phthalate esters distribution in coastal mariculture of Hong Kong, China.

The aim of the study is to evaluate the impact of mariculture on phthalate esters speciation and distribution in sediments and cultured fish in the Hong Kong regions and near mainland China. Concentrations of ∑phthalate esters in mariculture surface sediments (0 to 5 cm) ranged from 0.20 to 54.3 mg/kg dw (mean 10.3 mg/kg dw), with the highest recorded at M2 (20.4 mg/kg dw). Concentrations of phthalate esters were not significantly (p > 0.05) enriched in surface and sediment cores at mariculture sites relative to the reference sediments, 1 to 2 km away in areas without mariculture activities. Among different congeners, only butyl benzyl phthalate (BBP) concentrations demonstrated a significant correlation (R2 = 0.40, p < 0.05) with TOC values of sediments. The median concentrations of di-2-ethylhexyl phthalate (DEHP) and di-n-butyl phthalate (DBP) in the sediments were 1.57 and 6.96 times higher than the environmental risk levels (ERL), which may pose environmental risks. Results of health risk assessments revealed that the cultured fish (snubnose pompano, orange-spotted grouper, and red snapper) were safe for consumption, in terms of phthalate esters. This is the first study to assess the differences of phthalate esters contamination between mariculture and natural coastal sediments.

Characteristics and health risk assessment of heavy metals exposure via household dust from urban area in Chengdu, China.

To investigate the characteristics of heavy metals (Cr, Cd, Pb, Zn, Cu and Ni) in household dust in urban household environment of Chengdu, China, 90 household dust samples were collected from 6 districts of the city. The information of houses and residents were also recorded during dust sampling to identify the correlations between heavy metals in household dust and the house attributes. And also the principal component analysis and cluster analysis for sources and impactor factors. The concentrations of Pb (123mg·kg-1), Zn (675mg·kg-1), Cu (190mg·kg-1), Cr (82.7mg·kg-1), Cd (2.37mg·kg-1) and Ni (52.6mg·kg-1) in household dust are in low or moderate levels when compare with that from other counties or areas. The heavy metals of household dust samples from Chengdu is higher concentrations than that in the street dust from Chengdu, except for Cr. Statistical analysis result showed traffic sources and corrosion of alloys are important factors contributing to the rise concentrations of heavy metals in household dust. In addition, there is negative correlation (p<0.05) between the heavy metals concentrations and floor levels. The ingestion is the important pathway for Pb, Zn, Cu and Ni via household dust exposure to the residents, and the dermal contact was identified as a main route for Cr and Cd in household dust exposure to the residents. There are minor non-carcinogenic and carcinogenic risks from the heavy metals in household dust for the residents in Chengdu.