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.

The natural occurrence of arsenic (As) in groundwater & soils and its bioaccumulation in rice grains is a major health concern worldwide. To combat the problem, best combination of irrigation management and suitable rice variety altering As content in grains must be ensured. With this aim, a field trial was conducted with two rice varieties and water management including alternate wetting and drying (AWD) and continuous flooding (CF) irrigation regimes with As contaminated groundwater (AsW) and temporarily stored groundwater (TSG) and river water for only CF (as control). Results revealed that As content in different portions of paddy plant was significantly different (P < 0.001) with irrigation practices and rice varieties. AWD irrigation with TSG accumulated lower As in rice grains compared with CF-AsW for both varieties. Data showed that AWD-TSG practice led to 61.37% and 60.34% grain As reduction for BRRI dhan28 and BRRI dhan29, respectively, compared with CF-AsW. For Principle Component Analysis (PCA), first principle component (PC1) explained 91.7% of the variability and irrigation water As, soil total and available As, straw As, root As and husk As were the dominating parameters. With significant (P < 0.05) variation in yields between the genotypes, AWD increased grain yield by 29.25% in BRRI dhan29 Compared with CF. However, translocation factor (TF) and bioconcentration factor (BCF) for both varieties were less than one for all the treatments. The addition of this study to our knowledge base is that, AWD-TSG with BRRI dhan29 can be an As–safe practice without compromising yields.

The accumulation of arsenic in crop plants has become a worldwide concern that affects millions of people. The major source of arsenic in crop plants is irrigation water and soil. In this study, Serendipita indica, an endophytic fungus, was used to investigate the protection against arsenic and its accumulation in the tomato plant. We found that inoculation of S. indica recovers seed germination, plant growth and improves overall plant health under arsenic stress. A hyper-colonization of fungus in the plant root was observed under arsenic stress, which results in reduced oxidative stress via modulation of antioxidative enzymes, glutathione, and proline levels. Furthermore, fungal colonization restricts arsenic mobilization from root to shoot and fruit by accumulating it exclusively in the root. We observed that fungal colonization enhances the arsenic bioaccumulation factor 1.48 times in root and reduces the arsenic translocation factor by 2.96 times from root to shoot and 13.6 times from root to fruit compared to non colonized plants. Further, investigation suggests that S. indica can tolerate arsenic by immobilizing it on the cell wall and accumulating it in the vacuole. This study shows that S. indica may be helpful for the reduction of arsenic accumulation in crops grown in arsenic-contaminated agriculture fields.

Cresyl diphenyl phosphate (CDP), as a kind of aryl substituted organophosphate esters (OPEs), is commonly used as emerging flame retardants and plasticizers detected in environmental media. Due to the accumulation of CDP in organisms, it is very important to discover the toxicological mechanism and metabolic process of CDP. Hence, liver microsomes of crucian carps (Carassius carassius) were prepared for in vitro metabolism kinetics assay to estimate metabolism rates of CDP. After 140 min incubation, the depletion of CDP accounted for 58.1%–77.1% (expect 0.5 and 2 μM) of the administrated concentrations. The depletion rates were best fitted to the Michaelis-Menten model (R² = 0.995), where maximum velocity (Vₘₐₓ) and Michaelis-Menten constant (Kₘ) were 12,700 ± 2120 pmol min⁻¹·mg⁻¹ protein and 1030 ± 212 μM, respectively. Moreover, the in vitro hepatic clearance (CLᵢₙₜ) of CDP was 12.3 μL min⁻¹·mg⁻¹ protein. Log Kₒw and bioconcentration factor (BCF) of aryl-OPEs were both higher than those of alkyl- and chlorinated-OPEs, indicating that CDP may easily accumulate in aquatic organisms. The results made clear that the metabolism rate of CDP was greater than those of other OPEs detected in liver microsomes in previous research. This paper was first of its kind to comprehensively investigate the in vitro metabolic kinetics of CDP in fish liver microsomes. The present study might provide useful information to understand the environmental fate and metabolic processes of these kinds of substances, and also provide a theoretical basis for the ecological risk assessment of emerging contaminants.

The present paper reports on the interrelationships of fish, parasites and the bioaccumulation of hazardous organic compounds in the Zemplínska Šírava water reservoir in eastern Slovakia, which is heavily polluted with polychlorinated biphenyls (PCBs). The concentrations of these contaminants were measured in various fish matrices (dorsal and abdominal muscle tissues, hepatopancreas, intestine wall and adipose tissue) of the freshwater bream, Abramis brama (Cyprinidae), and in its intestinal parasite Caryophyllaeus laticeps (Cestoda), which was used for the first time as a model for a PCB bioaccumulation study. Regarding the fish, the highest concentrations of PCBs were found in the intestine, followed by hepatopancreas and muscle tissues. The amounts of PCBs were higher in abdominal muscles than in their dorsal parts. Concentrations of ∑PCBs above the limits set by European regulations were detected in both muscle parts in the fish, confirming the persistent unfavorable conditions in this locality and high risk for biota and humans. Based on bioconcentration factor values (BCFs), PCBs reached much higher levels in cestodes compared to bream matrices. Some significant differences in PCB amounts between infected and uninfected bream were determined. Fulton's condition factor (CF) significantly differed in infected and non-infected fish (p ˂ 0.05), with CF values surprisingly lower in fish free of parasites compared to parasitized fish, which suggests a “mutualistic” relationship between the parasite and its host.

Rhizosphere acidification in leguminous plants can release P from the dissolution of phosphate compounds which can reduce Pb bioavailability to them via the formation of insoluble Pb compounds in their rhizosphere. A soil polluted from Pb-acid batteries effluent (SPBE), having total Pb = 639 mg kg⁻¹, was amended with six different rates (0, 0.5, 1, 2, 4 and 6%) of oxalic acid-activated phosphate rock (OAPR) and their effects on pH, available P and bioavailable Pb concentrations in the rhizosphere and bulk soils of mung bean plant were evaluated. Furthermore, the effects of these variant OAPR rates on Pb concentrations in plant parts, bioaccumulation factor (BAF) and translocation factor (TF) for Pb in grain and traits like productivity, the activities of antioxidant enzymes, and grain biochemistry were investigated. Results revealed that increasing rates of OAPR significantly increased pH values and available P while decreased bioavailable Pb concentrations in the rhizosphere over control. The highest dissolution of P in the rhizosphere was with 4 and 6% OAPR rates. As a result, the formation of insoluble Pb compounds affected on reduced Pb concentrations in shoots, roots, and grain in addition to lower grain BAF and TF values for Pb over control. Likewise, the highest plant productivity, improved grain biochemistry, high Ca and Mg concentrations, least oxidative stress, and enhanced soil alkaline phosphatase activity were found with 4 and 6% OAPR rates. The OAPR 4% rate is suggested for reducing grain Pb concentration, cell oxidative injury, and improving grain biochemistry in mung bean.

Amendment with sewage sludge or biosolids can increase soil fertility but may also transfer biosolid-borne pollutants to the soil and the possible effects on the soil ecosystem are poorly understood, especially long-term effects. A long-term experiment was therefore established to assess the effects of repeated applications of different types of biosolids (fresh domestic, dried domestic and fresh industrial sludges) in field conditions. Nine years of sludge application led to changes in soil chemical and biological properties and generally contributed little to soil nutrient status. However, soil concentrations of potentially toxic elements (PTEs) were elevated by amendment, especially with industrial biosolids. Soil fauna are usually used to decipher the underlying effects of biosolid applications on the soil ecosystem. Here, collembolans (50.9%), nematodes (41.6%) and enchytraeid worms (7.50%) were collected and differentiated into different ecological and trophic groups and their body lengths and PTE concentrations in the body tissues were investigated. The animals showed different responses to the biosolids at population and individual levels. There were substantial changes in epigeic collembolan communities and bacterivorous nematodes increased significantly after biosolid amendment. Biosolid-borne PTEs were major factors and Redundancy (RDA) analysis indicates that collembolan communities were strongly influenced by zinc (Zn). The three groups of soil animals showed similar trends in accumulation of PTEs in the sequence cadmium (Cd) > Zn > copper (Cu), and the bioaccumulation factor (BAF) values of the PTEs were significantly higher in the industrial sludge treatment than in other two treatments with a similar trend of decreasing body length of nematodes. The results indicate that it is potentially risky to use industrial biosolids in the long term, and different species and ecological groups of collembolans and different trophic groups of nematodes should be examined when assessing soil health.

As emerging pollutants, the occurrence and risks of organophosphate esters (OPEs) in mariculture farms should be concerned; however, information is limited. Beibu Gulf is one of the essential mariculture zones in China. This study aimed to investigate the occurrence of OPEs in mariculture farms of the Beibu Gulf, their phase distribution and bioaccumulation among sediment, organisms (shrimp, crab, and oyster), water, and feed. Human exposure to OPEs through seafood consumption was also assessed. The total concentrations of the 11 target OPEs (∑₁₁OPEs) in the water samples ranged 32.9–227 ng L⁻¹. It was significantly higher in water from the culture ponds (mean 122 ng L⁻¹) than in water from the estuaries and nearshore areas (mean 51.1 ng L⁻¹) (nonparametric test, p < 0.05). ∑₁₁OPEs in the feeds averaged 46.0 (range 21.7–84.5) ng g⁻¹ dw, which is similar to the level in the organism samples (mean 55.5, range 21.3–138 ng g⁻¹ dw) and 4.4 times higher than that in the sediment (mean 10.9, range 35–22.1 ng g⁻¹ dw). The ∑₁₁OPEs released from the feeds to the culture ponds was estimated to be 49 μg m⁻² per three-month period. In the aquaculture ponds, the sediment-water distribution coefficient (log KOC), and the bioaccumulation factors from the water (log BWAFs) or the feed (log BFAFs) to the organisms, depend linearly on the hydrophobicity (log KOW) of OPEs. The log BWAFs and log BFAFs increased with increasing log KOW within the log KOW range of 1–7. The human exposure to OPEs through consumption of shrimp, crab, and oysters from the mariculture farms does not pose a health risk at present.

Production of chrysanthemum (Dendranthema grandiflora) in greenhouses often requires intensive pesticide use, which raises serious concerns over food safety and human health. This study investigated uptake, translocation and residue dissipation of typical fungicides (metalaxyl-M and fludioxonil) and insecticides (cyantraniliprole and thiamethoxam) in greenhouse chrysanthemum when applied in soils. Chrysanthemum plants could absorb these pesticides from soils via roots to various degrees, and bioconcentration factors (BCFLS) were positively correlated with lipophilicity (log Kₒw) of pesticides. Highly lipophilic fludioxonil (log Kₒw = 4.12) had the greatest BCFLS (2.96 ± 0.41 g g⁻¹), whereas hydrophilic thiamethoxam (log Kₒw = −0.13) had the lowest (0.09 ± 0.03 g g⁻¹). Translocation factors (TF) from roots to shoots followed the order of TFₗₑₐf > TFₛₜₑₘ > TFfₗₒwₑᵣ. Metalaxyl-M and cyantraniliprole with medium lipophilicity (log Kₒw of 1.71 and 2.02, respectively) and hydrophilic thiamethoxam showed relatively strong translocation potentials with TF values in the range of 0.29–0.81, 0.36–2.74 and 0.30–1.03, respectively. Dissipation kinetics in chrysanthemum flowers followed the first-order with a half-life of 21.7, 5.5, 10.0 or 8.2 days for metalaxyl-M, fludioxonil, cyantraniliprole and thiamethoxam, respectively. Final residues of these four pesticides, including clothianidin (a primary toxic metabolite of thiamethoxam), in all chrysanthemum flower samples were below the maximum residue limit (MRL) values 21 days after two soil applications each at the recommended dose (i.e., 3.2, 2.1, 4.3 and 4.3 kg ha⁻¹, respectively). However, when doubling the recommended dose, the metabolite clothianidin remained at concentrations greater than the MRL, despite that thiamethoxam concentration was lower than the MRL value. This study provided valuable insights on the uptake and residues of metalaxyl-M, fludioxonil, cyantraniliprole and thiamethoxam (including its metabolite clothianidin) in greenhouse chrysanthemum production, and could help better assess food safety risks of chrysanthemum contamination by parent pesticides and their metabolites.

The seasonal variation and distribution among different matrices of endocrine-disrupting chemicals (EDCs) were investigated in the eutrophic water ecosystem of the Pearl River Delta, Guangdong, China. The chlorophyll a (Chl a) levels were generally higher in summer than in spring; however, the concentrations of 4-tert-octylphenol (OP), 4-nonylphenol (NP), and bisphenol A (BPA) in surface water were generally higher in spring (oligotrophic) than in summer (eutrophic). The levels of EDCs in SPM were lower in spring than in summer, a pattern seen in the seasonal variation of Chl a and particulate organic carbon (POC). The seasonal variations of EDCs in water bodies with different levels of eutrophication were analyzed in several dimensions including sediment, POC, algae and fish bile. The log Kₒc for SPM/water was higher in summer than in spring. The log Kₒc values for NP, OP, and BPA exhibited the following trends between matrices: colloid/water > sediment/water > SPM/water > algae/water, colloid/water > sediment/water > algae/water > SPM/water, and colloid/water > algae/water > sediment/water > SPM/water. The EDCs levels were different in fish tissues with the order bile > liver > muscle, with the concentrations being an order of magnitude higher in bile than in liver and an order of magnitude higher in liver than in muscle. The sequence of the bioconcentration factor (log BCF) for bile/water and liver/water was NP < OP < BPA in eutrophic conditions, but NP > OP > BPA in oligotrophic conditions. The order in eutrophic conditions was the same as the log BCF and log Kₒc for algae/water, indicating that the accumulation of EDCs in water bodies could be affected by algae, which could be one of the reasons of the seasonal variation of EDCs in water.