Transport of neonicotinoid insecticides in a wetland ecosystem: Has the cultivation of different crops become the major sources?

Neonicotinoid insecticides in river water of an agriculture-dominated basin: Occurrence, flux variations, and ecological risks

The widespread use of neonicotinoid insecticides (NNIs) has led to their widespread detection in surface waters worldwide. However, pollution characteristics and transport fluxes in agriculture-dominated watersheds have not been thoroughly studied. In this study, we analyzed the pollution characteristics of NNIs in the Zhoukou Reach of the Shaying River, a typical agricultural area in northern China, focusing on their vertical distribution, transport flux, and ecological risk across different river sections. NNIs were commonly detected in the surface water in the Zhoukou section of the Shaying River, with concentrations ranging from 42.5 to 307 ng/L. The predominant compounds were imidacloprid, thiamethoxam, acetamiprid, and clothianidin at concentrations of 33.4 ng/L, 30.0 ng/L, 29.1 ng/L, and 28.7 ng/L, respectively. Vertically, higher NNI concentrations of 163 ± 88.9 ng/L were found in the bottom layer than in the surface layer (152 ± 82.9 ng/L) (p < 0.05). Compared to the upstream and midstream regions, the NNI concentration downstream was higher, primarily because of the developed fruit cultivation and high pesticide usage. The initial input flux of NNIs of the Zhoukou section of the Shaying River was 1.73 kg/d, whereas the output flux was 4.32 kg/d, with a net flux of 2.58 kg/d. In the midstream and upstream regions, NNIs pose a chronic risk to aquatic invertebrates, whereas NNIs in the downstream region present an acute risk. Therefore, it is crucial to alleviate downstream NNI pollution.

Occurrence and transport of neonicotinoid insecticides in soils from an agriculture-dominated area in Henan Province, Northern China: Insights from agricultural management practices

Neonicotinoid insecticides (NNIs) are among the most widely used pesticides and have garnered significant attention recently because of their high toxicity to non-target organisms and potential risks to human health. In this study, vertical soil profiles were collected from the Zhoukou reach of the Shaying River Basin, China, where pesticides are heavily used, to investigate the pollution characteristics and ecological risks of NNIs, with a focus on the impact of agricultural management practices on NNI residues in farmland soils. NNIs were widely detected in the soils, with a detection frequency of 100 % and a mean concentration of 73.8 ± 167 ng/g. NNI levels were higher in farmland soil than in urban areas, which were 89.5 ± 182 ng/g and 4.8 ± 6.6 ng/g, respectively. NNI levels varied considerably among farmlands growing different crops, and higher NNI residues were found in soils growing vegetables and peanuts (Veg & Pn) than in those growing corn and fruit. Vertically, NNI levels in the soil significantly decreased from the surface layer (0-15 cm) to the intermediate (15-30 cm) and bottom layers (30-50 cm) (p < 0.05), with concentrations in the intermediate and bottom layers being 49.8 % and 22.4 % of those in the surface layer, respectively. The cultivation of Veg & Pn significantly increased NNI levels in farmland soils. Conversely, using river water for irrigation, having the correct knowledge of pesticide toxicity (higher toxicity does not necessarily lead to better pest control effectiveness), and long application intervals can significantly reduce NNI residues in the soil. Although the health risks of NNI exposure are relatively low, the ecological risk to non-target organisms in the soil requires attention, particularly in farmland areas.

Neonicotinoid metabolites in farmland surface soils in China based on multiple agricultural influencing factors: A national survey

Certain neonicotinoid metabolites (mNEOs) are causing widespread concern because they are equally or even more toxic than the parent NEOs. Currently, there is limited information on the distribution of mNEOs in soil. Especially, it is unknown that the effects of agricultural factors, such as plastic filming, plowing, irrigation, and fertilization, on mNEOs. This study is the first to reveal that mNEOs were commonly found in agricultural topsoil in China, with a geometric mean concentration of ΣmNEOs of 0.298 μg/kg. Among 31 provinces in Mainland China, Fujian had the highest mNEO residues, whereas Shanghai had the lowest. Among topsoil of various crop types, that of fruits and vegetables were found the highest mNEO residues. Furthermore, higher levels of film cover were associated with higher mNEO residues. Microplastics (MPs, serving as contaminant carriers) were positively correlated with mNEOs under field conditions, which was related to the adsorption capacity of microplastics and its influence on the soil conditions and the years of film cover. Alternatively, this study shows for the first time that irrigation water and manure might be sources of mNEO input into the soil, and that the plowing frequency might also influence on mNEOs.

Screening and quantification of pesticides in wetland water, ice, sediment and soil: Occurrence, transport and risk assessment

Current researches on pesticides in wetlands are limited in terms of screening and quantification of many types of pesticides. Understanding the spatial and temporal dynamics, distribution patterns, and environmental risks of pesticides in multiple media is important for wetland ecological conservation. In this study, 222 pesticides were determined in multimedia samples collected simultaneously from the Songhua Wetland during four seasons. Concentrations of target pesticides in water, ice, sediment and soil ranged from 94.1 to 7445 ng/L, 62.6-953 ng/L, 0.82-50.2 ng/g dw, and 4.32-146 ng/g dw. Large spatial differences (p < 0.05) in pesticide concentrations in ice were found. However, there were no significant differences in the spatial and temporal distribution of pesticides in water, sediment, and soil (p > 0.05), suggesting that there were no correlation between the spatial and temporal use of pesticides. The dynamic exchange of pesticides between water-ice indicated that most pesticides were more enriched in water. However, there were still some pesticides (Dichlorvos and Biphenyl) that showed a stronger tendency to transfer from water to ice. Sediment-water exchange suggested that sediment is a source of secondary releases of most pesticides in wetland ecology, but is a sink for Biphenyl and Oxadiazon. The correlation between concentration ratios and fugacity fraction supported this finding. Most individual pesticides in wetland water and ice had shown low or moderate ecological risk conducted using risk quotient. The cumulative toxic effects of multiple pesticides had a high potential to pose a threat to wetland aquatic organisms.

Neonicotinoid insecticides in paddy fields: Dissipation dynamics, migration, and dietary risk

Neonicotinoid insecticides (NNIs) have caused widespread contamination of multiple environmental media and posed a serious threat to ecosystem health by accidently injuring non-target species. This study collected samples of water, soil, and rice plant tissues in a water-soil-plant system of paddy fields after spaying imidacloprid (IMI), thiamethoxam (THM), and clothianidin (CLO) to analyze their distribution characteristics and migration procedures and to assess related dietary risks of rice consumption. In the paddy water, the concentrations of NNIs showed a dynamic change of increasing and then decreasing during about a month period, and the initial deposition of NNIs showed a trend of CLO (3.08 μg/L) > THM (2.74 μg/L) > IMI (0.97 μg/L). In paddy soil, the concentrations of the three NNIs ranged from 0.57 to 68.3 ng/g, with the highest residual concentration at 2 h after application, and the concentration trend was opposite to that in paddy water. The initial deposition amounts of IMI, THM, and CLO in the root system were 5.19, 3.02, and 5.24 μg/g, respectively, showing a gradual decrease over time. In the plant, the initial deposition amounts were 19.3, 9.36, and 52.6 μg/g for IMI, THM, and CLO, respectively, exhibiting concentration trends similar to those in the roots. Except for IMI in soil, the dissipation of the NNIs conformed to the first-order kinetic equation in paddy water, soil, and plant. The results of bioconcentration factors (BCFs) and translocation factor (TF) indicated that NNIs can be bi-directionally transported in plants through leaf absorption and root uptake. The risk of NNIs intake through rice consumption was low for all age groups, with a slightly higher risk of exposure in males than in females.

Imidacloprid removal by modified graphitic biochar with Fe/Zn bimetallic oxides

Coping with the critical challenge of imidacloprid (IMI) contamination in sewage treatment and farmland drainage purification, this study presents a pioneering development of an advanced modified graphitic white melon seed shells biochar (Fe/Zn@WBC). The Fe/Zn@WBC demonstrates a substantial enhancement in adsorption efficiency for IMI, achieving a remarkable removal rate of 87.69% within 30 min and a significantly higher initial adsorption rate parameter h = 4.176 mg g-1·min-1. This significant improvement outperforms WBC (12.22%, h = 0.115 mg g-1·min-1) and highlights the influence of optimized adsorption conditions at 900 °C and the graphitization degree resulting from Fe/Zn bimetallic oxide modification. Characterization analysis and batch sorption experiments including kinetics, isotherms, thermodynamics and pH factors illustrate that chemical adsorption is the main type of adsorption mechanism responsible for this superior ability to remove IMI through pore filling, hydrogen bonding, hydrophobic interaction, electrostatics interaction, π-π interactions as well as complexation processes. Furthermore, we demonstrate exceptional stability of Fe/Zn@WBC across a broad pH range (pH = 3-11), co-existing ions presence along with humic acid under various real water conditions while maintaining high removal efficiency. This study presents an advanced biochar adsorbent, Fe/Zn@WBC, with efficient adsorption capacity and easy preparation. Through three regeneration cycles via pyrolysis method, it demonstrates excellent pyrolysis regeneration capabilities with an average removal efficiency of 92.02%. The magnetic properties enable rapid separation facilitated by magnetic analysis. By elucidating the efficacy and mechanistic foundations of Fe/Zn@WBC, this research significantly contributes to the field of environmental remediation by providing a scalable solution for IMI removal and enhancing scientific understanding of bimetallic oxides-hydrophilic organic pollutant interactions.

Adsorption interactions between typical microplastics and enrofloxacin: Relevant contributions to the mechanism

Microplastics (MPs) are increasingly contaminating the environment and they can combine with antibiotics as carriers to form complex contaminants. In this study, we systematically investigated the interactions between the antibiotic enrofloxacin (ENR) and MPs comprising polyethylene (PE), polyvinyl chloride (PVC), and polystyrene (PS). Characterization was performed by using conventional techniques and the mechanisms involved in interactions were initially explored based on adsorption kinetics, isotherms, and resolution experiments, and the adsorption capacities of the MPs were determined. In addition, the extended Derjaguin-Landau-Verwey-Overbeek theory was used to investigate the interaction mechanisms. The results showed that the interactions were weaker in strong acidic and alkaline environments, and the interactions were also inhibited at higher salt ion concentrations. The saturation adsorption amounts of ENR on PVC, PE, and PS were 74.63 μg/g, 103.09 μg/g, and 142.86 μg/g, respectively. The interactions between MPs and ENR were dominated by hydrophobic interactions, followed by van der Waals forces and acid-base forces. This study provides new insights into the adsorption behavior of ENR by MPs.

Chemical characteristics, distribution patterns, and source apportionment of particulate elements and inorganic ions in snowpack in Harbin, China

Snowpack, which serves as a natural archive of atmospheric deposition of multiple pollutants, is a practical environmental media that can be used for assessing atmospheric records and input of the pollutants to the surface environments and ecosystems. A total of 29 snowpack samples were collected at 20 sampling sites covering three different functional areas of a major city (Harbin) in Northeast China. Two samples at the "snow layer" and one or two samples at the "particulate layer" were collected at each sampling site in the industrial areas characterized by multi-layer snowpack, and only one sample at the "snow layer" was collected at each sampling site in the cultural and recreational as well as agricultural areas. The snow contents of 31 elements (Na, Mg, Al, K, Ca, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Y, Cd, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Pb) and six major water-soluble inorganic ions (WSIIs, NH4+, K+, Ca2+, NO2-, NO3-, and SO42-) were analyzed. The total mass of the measured elements is dominated (95.8%-99.2%) by crustal elements. Heavy metals only account for 0.77%-4.07% of the total mass of the elements, but are occasionally close to or even above the standard limit in the "Environmental Quality Standards for Surface Water" of China (GB3838-2002). SO42- and Ca2+ are the main anion and cation, accounting for 34.9%-81.1% and 1.43%-29.9%, respectively, of the measured total ions. Total atmospheric deposition of crustal elements and heavy metals is dominated by wet deposition in areas near the petrochemical plant and by dry deposition in areas near the cement plant. Coal combustion, industrial emissions, and traffic-related activities lead to the enrichment of heavy metals in the snowpacks of urban and suburban areas, while coal combustion and biomass burning contribute to pollution in rural areas. The cities and regions situated in the western, northwestern, northern, and northeastern directions from Harbin are potential source regions of these pollutant species.