The widespread use of zinc oxide nanoparticles (ZnO-NPs) has led to their release into the environment, and they thus represent a potential risk for both humans and ecosystems. However, the negative impact of ZnO-NPs on the immune system, especially in relation to host defense against pathogenic infection and its underlying regulatory mechanisms, remains largely unexplored. This study investigated the effects of early-life long-term ZnO-NPs exposure (from L1 larvae to adults) on innate immunity and its underlying mechanisms using a host–pathogen Caenorhabditis elegans model, and this was compared with the effect of ionic Zn. The results showed that the ZnO-NPs taken up by C. elegans primarily accumulated in the intestine and that early-life long-term ZnO-NPs exposure at environmentally relevant concentrations (50 and 500 μg/L) decreased the survival of wild-type C. elegans when faced with pathogenic Pseudomonas aeruginosa PA14 infection. Early-life long-term ZnO-NPs (500 μg/L) exposure significantly increased (by about 3-fold) the accumulation of live P. aeruginosa PA14 colonies in the intestine of C. elegans. In addition, ZnO-NPs (500 μg/L) inhibited the intestinal nuclear translocation of SKN-1 and also downregulated gcs-1 gene expression, which is an SKN-1 target gene. Further evidence revealed that early-life long-term exposure to ZnO-NPs (500 μg/L) did not increase susceptibility to mutation among the genes (pmk-1, sek-1, and nsy-1) encoding the p38 mitogen-activated protein kinase (MAPK) cascade in response to P. aeruginosa PA14 infection, though ZnO-NPs significantly decreased the mRNA levels of pmk-1, sek-1, and nsy-1. This study provides regulatory insight based on evidence that ZnO-NPs suppress the innate immunity of C. elegans and highlights the potential health risks of certain environmental nanomaterials, including ZnO-NPs, in terms of their immunotoxicity at environmentally relevant concentrations.

Release of antibiotics into the environment, which often occurs downstream of wastewater treatment plants, poses a human health threat due to the potential development of bacterial antibiotic resistance. In this study, laboratory experiments were conducted to evaluate the performance of ball milled biochar on the removal of two sulfonamide antibiotics, sulfamethoxazole (SMX) and sulfapyridine (SPY) from water and wastewater. Aqueous batch sorption experiment using both pristine and ball milled biochar derived from bagasse (BG), bamboo (BB) and hickory chips (HC), made at three pyrolysis temperatures (300, 450, 600 °C), showed that ball milling greatly enhanced the SMX and SPY adsorption. The 450 °C ball milled HC biochar and BB biochar exhibited the best removal efficiency for SMX (83.3%) and SPY (89.6%), respectively. A range of functional groups were produced by ball milling, leading to the conclusion that the adsorption of sulfonamides on the biochars was controlled by multiple mechanisms including hydrophobic interaction, π–π interaction, hydrogen bonding, and electrostatic interaction. Due to the importance of electrostatic interaction, SMX and SPY adsorption was pH dependent. In laboratory water solutions, the Langmuir maximum adsorption capacities of SMX and SPY reached 100.3 mg/g and 57.9 mg/g, respectively. When tested in real wastewater solution, the 450 °C ball milled biochar still performed well, especially in the removal of SPY. The maximum adsorption capacities of SMX and SPY in wastewater were 25.7 mg/g and 58.6 mg/g, respectively. Thus, ball milled biochar has great potential for SMX and SPY removal from aqueous solutions including wastewater.

Although nanoscale surface roughness has been theoretically demonstrated to be a crucial factor in the interaction of colloids and surfaces, little experimental research has investigated the influence of roughness on colloid or silver nanoparticle (AgNP) retention and release in porous media. This study experimentally examined AgNP retention and release using two sands with very different surface roughness properties over a range of solution pH and/or ionic strength (IS). AgNP transport was greatly enhanced on the relatively smooth sand in comparison to the rougher sand, at higher pH, and lower IS and fitted model parameters showed systematic changes with these physicochemical factors. Complete release of the retained AgNPs was observed from the relatively smooth sand when the solution IS was decreased from 40 mM NaCl to deionized (DI) water and then the solution pH was increased from 6.5 to 10. Conversely, less than 40% of the retained AgNPs was released in similar processes from the rougher sand. These observations were explained by differences in the surface roughness of the two sands which altered the energy barrier height and the depth of the primary minimum with solution chemistry. Limited numbers of AgNPs apparently interacted in reversible, shallow primary minima on the smoother sand, which is consistent with the predicted influence of a small roughness fraction (e.g., pillar) on interaction energies. Conversely, larger numbers of AgNPs interacted in deeper primary minima on the rougher sand, which is consistent with the predicted influence at concave locations. These findings highlight the importance of surface roughness and indicate that variations in sand surface roughness can greatly change the sensitivity of nanoparticle transport to physicochemical factors such as IS and pH due to the alteration of interaction energy and thus can strongly influence nanoparticle mobility in the environment.

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.

Rice is a known bioaccumulator of methylmercury (MeHg). Rice consumption may be the primary pathway of MeHg exposure in certain mercury (Hg)-contaminated areas of the world. Pakistan is the 4th-largest rice exporter in the world after India, Thailand, and Vietnam. This study aimed to evaluate the Hg contamination status of rice from Pakistan and the health risks associated with Hg exposure through its consumption. 500 rice grain samples were collected from two major rice-growing provinces, Punjab and Sindh, which contain 92% of Pakistan’s rice cultivation area. Analysis of polished rice showed mean total Hg (THg) concentration of 4.51 ng.g⁻¹, while MeHg concentrations of selected samples averaged 3.71 ng.g⁻¹. Only 2% of the samples exceeded the permissible limit of 20 ng.g⁻¹. Samples collected from Punjab showed higher Hg contents than those from Sindh, possibly due to higher rates of urbanization and industrialization. Rice samples collected from areas near brick-making kilns had the highest Hg concentrations due to emissions from the low-quality coal burned. THg and MeHg contents varied by up to five and fourfold, respectively, between point and non-point Hg pollution sites. Moreover, the %Hg as MeHg in rice did not differ significantly between point and non-point Hg sources. Health risk was assessed by calculating a mean probable daily intake, revealing that Hg intake through rice consumption is within the safe limits recommended by the World Health Organization. However, rice intake may be a substantive pathway of MeHg exposure because fish, which are another major source of Hg, are consumed in Pakistan at some of the world’s lowest rates. This study provides fundamental data for further understanding of the global issue of Hg contamination of rice and its related health risks. Furthermore, the current study suggests there is a need to conduct further research in rice-growing areas at the regional level.

Environmental dissolved organic matter (DOM) has been proved to increase microbial population sizes and stimulate the degradation of some pesticide molecules. Among these molecules, the present study investigated the biodegradation of the herbicide glyphosate depending on photoautotrophs DOM supply in a microbial consortium isolated from river biofilms. Degradation experiments in the laboratory were performed in dark and light conditions, as well as after antibiotic supply, in order to characterize the eventual interactions between photoautotrophs and heterotrophs activity during glyphosate degradation. Fifty percent of the initial concentration of glyphosate (0.6 mM) was transformed into aminomethyl phosphonic acid (AMPA) after 9 days in presence or absence of light. Accordingly, the photoautotrophic DOM supply was not stimulating glyphosate degradation by microbial heterotrophs. This lack of response was probably explained by the low net primary production values and weak dissolved organic carbon production recorded in light treatments. The supply of the antibiotic drastically stopped glyphosate transformation demonstrating the central role of bacteria in the biodegradation of the herbicide. Glyphosate also modified the structure of prokaryotes assemblages in the consortium by increasing the relative abundances of Alphaproteobacteria and slightly decreasing those of Gammaproteobacteria. The chemoorganotrophic bacteria Phenylobacterium sp. (Alphaproteobacteria) was related to the transformation of glyphosate in our microbial consortium. The present study highlights the complexity of microbial interactions between photoautotrophs and heterotrophs in microbial assemblages that can contribute to the degradation of pesticides present in aquatic environments.

Dichlorodiphenyltrichloroethane (DDT) is well known for its harmful effects and has been banned around the world. However, DDT is still frequently detected in natural environments, particularly in aquaculture and harbor sediments. In this study, 15 surface sediment samples were collected from a typical tropical bay (Zhanjiang Bay) in the South China Sea, and the levels of DDT and its metabolites in sediment and porewater samples were investigated. The results showed that concentrations of DDXs (i.e., DDT and its metabolites) in bulk sediments were 1.58–51.0 ng g⁻¹ (mean, 11.5 ng g⁻¹). DDTs (DDT and its primary metabolites, dichlorodiphenyldichloroethane (DDD) and dichlorodiphenyldichloroethylene (DDE)) were the most prominent, accounting for 73.2%–98.3% (86.1% ± 12.8%) of the DDXs. Additionally, high-order metabolites (i.e., 1-chloro-2,2-bis(4′-chlorophenyl)ethylene (p,p′-DDMU), 2,2-bis(p-chlorophenyl)ethylene (p,p′-DDNU), 2,2-bis(p-chlorophenyl)ethanol (p,p′-DDOH), 2,2-bis(p-chlorophenyl)methane (p,p′-DDM), and 4,4′-dichlorobenzophenone (p,p′-DBP)) were also detected in most of the sediment and porewater samples, with DDMU and DBP being predominant. The DDTs concentration differed among the sampling sites, with relatively high DDTs concentrations in the samples from the aquaculture zone and an area near the shipping channel and the Haibin shipyard. The DDD/DDE ratios indicated a reductive dichlorination of DDT to DDD under anaerobic conditions at most of the sampling sites of Zhanjiang Bay. The possible DDT degradation pathway in the surface sediments of Zhanjiang Bay was p,p′-DDT/p,p′-DDD(p,p′-DDE)/p,p′-DDMU/p,p′-DDNU/ … /p,p′-DBP. The DDXs in the sediments of Zhanjiang Bay were mainly introduced via mixed sources of industrial DDT and dicofol, including fresh input and historical residue. The concentrations of DDXs in porewater samples varied from 66.3 to 250 ng L⁻¹, exhibiting a distribution similar to that in the accompanying sediments. However, the content of high-order metabolites was relatively lower in porewater than in sediment, indicating that high-order degradation mainly occurs in particles. Overall, this study helps in understanding the distribution, source, and degradation of DDT in a typical tropical bay.

Under the increasingly intensive measures for surface water restoration in China, point source discharge has been strictly regulated; however, for non-point sources, which constitute a large part of surface water pollutants, effective control has been difficult to reach. A comprehensive understanding of the characteristics of non-point source pollutants is essential for surface water improvement programs of cities such as Ningbo, on the southeast coast of China. Ningbo has made tremendous efforts in the past few years to control point source pollutants, but available data and management strategies on the non-point source pollutants are still limited. To this end, leachates of representative non-point source samples from the territory of Ningbo, including cropland and wetland soil, urban channel sediment, and poultry manure, were examined and compared focusing on the fluorescence characteristics and biodegradability of the dissolved organic matter (DOM). Results indicated that biodegradable dissolved organic carbon (BDOC) accounting for the total DOC was 46.7 ± 0.7% for cropland, wetland (56.3 ± 6.8%), non-sewage channel (60.1 ± 0.4%), sewage channel (74.5 ± 1.1%), and poultry manure (62.7 ± 4.5%). The leachates of the studied samples showed significant differences in both the amount and composition of DOM. However, a fluorescence component representing tryptophan-like substances identified by the excitation-emission matrix (EEM) combined with parallel factor (PARAFAC) analysis effectively predicted the BDOC variations among the studied samples. Moreover, under the studied nutrient concentrations, which were equivalent to Grade III water quality in China, nutrient limitation of microbial degradation was not observed. Threats to water quality, especially excessive consumption of dissolved oxygen, could be posed by the non-point source leachates due to their high bioavailability, large distribution, and weak nutrient restraint. Further investigations, including a quantitative evaluation of the non-point source pollution contribution, and pollutant blocking techniques are required.

Porous carbon, which can be functionalized, is considered as a potential carbon material. Herein, two-dimensional (2D) nitrogen-doped magnetic Fe₃C/C (NMC) was prepared by a simple carbonization method using potassium humate (HA-K) as raw material. Remarkably, two templates, g-C₃N₄ and KCl, were formed in situ during the carbonization process, which provide the necessary conditions for the formation of 2D NMC. The NMC was comprehensively studied by different characterization methods. The results show that NMC has a large surface area and mesoporous structure. The prepared NMC-0.50 was used to test the removal performance of Cr(VI). The effects of pH value, coexisting ions and time on Cr(VI) removal performance were investigated, and the adsorption kinetics, isotherm and thermodynamics were studied. The results showed that the adsorption isotherm model of NMC-50 accorded with the Langmuir model, and the maximum adsorption capacity was 423.73 mg g⁻¹. The reaction mechanism of Cr(VI) is adsorption and redox reaction. In addition, NMC-0.50 exhibit high selectivity, separability and regeneration performance. A convenient means for the synthesis of NMC was designed in this work, and demonstrate that NMC has practical value as an adsorbent.

Atmospheric levels of chlorinated paraffins (CPs) at five remote, six rural and four urban sites in Australia were measured using XAD-2 passive air samplers (XAD-PAS). While long-chain CP (LCCP, C>₁₇) levels were below method detection limits (MDLs), short-chain CPs (SCCPs, C₁₀₋₁₃) and, for the first time, medium-chain CPs (MCCPs, C₁₄₋₁₇) and CPs with a carbon chain length of nine (CP–C9) were found at many sites (88%, 81% and 88%, respectively) across the Australian continent, representing a range of environmental conditions. Applying preliminary sampling rates of the XAD-PAS for CPs, gaseous CP levels in Australian air were <MDL-1.3 and <MDL-1.8 ng/m³ for ΣSCCPs and ΣMCCPs, respectively, with a significant decreasing trend from more densely to less densely populated areas. Atmospheric median levels in this study (0.37 and 0.47 ng/m³ for SCCPs and MCCPs, respectively) were at the lower end of the median range (0.32–10 and 3.0–4.2 ng/m³ for SCCPs and MCCPs, respectively) reported for CPs at predominantly urban or industrial sites elsewhere (apart from China and extremely remote sites such as Antarctica). Principal component analysis matched the SCCP and MCCP congener group patterns in samples with those found in commercial mixtures, indicating a prevalence of less chlorinated congener groups in the Australian atmosphere. Information about the Australian production, use and disposal of CPs as well as their levels in other environmental matrices, including humans, is needed for assessing their emissions, behaviour, fate and potential exposure.