Pesticides are heavily applied in rice–vegetable rotations in tropical China, yet publicly available information on the contamination and risk of currently used pesticides (CUPs) and legacy ...pesticides (LPs) in surface waters of river basins draining these areas is very limited. Therefore, in two tropical river basins (Nandu River and Wanquan River basins) dominated by rice–vegetable rotations in Hainan, China, pesticides were analyzed in 256 surface water samples in wet and dry seasons. Forty-one pesticides were detected, and total concentrations ranged from not detectable to 24.2 μg/L. Carbendazim and imidacloprid were the two most prevalent CUPs, detected in 59.8% and 17.7%, respectively, of surface water samples at concentrations above 0.1 μg/L. Chlorpyrifos was the main LP, detected in 9.0% of samples at a concentration above 0.05 μg/L. The fungicides difenoconazole and emamectin benzoate, the herbicide butachlor, and the insecticide acetamiprid occurred in ≥12.5% samples at concentrations above 0.1 μg/L. Surface waters typically (85.2%) contained 5 to 15 residues, with an average of nine. Seasonally, the concentrations of the 41 pesticides were in the order January > July > November > September. Spatially, the composition of the main CUPs (not LPs) was significantly different depending on position in the drainage, which also changed with seasons. Crop and pest types and wet and dry seasons were the key factors controlling the spatiotemporal distribution of CUPs and LPs in surface waters. On the basis of evaluations of the exposures to individual pesticides and the dominant combinations with ≥8 pesticides, multiple pesticides were likely a significant risk to aquatic organisms, although noncarcinogenic and carcinogenic risks to humans were low. This study provides valuable data to better understand pesticide occurrence and ecological risks in river basins draining areas with rice–vegetable rotation systems in tropical China.
Display omitted
•Forty-one currently used and legacy pesticides were detected in surface waters.•Carbendazim (CUP) and chlorpyrifos (LP) were most frequently detected.•Most surface waters (64%) in the tropical river basins had ≥8 residues.•Ecotoxicological and noncarcinogenic and carcinogenic risks of CUPs were low.•High ecological risk of multiple pesticides should not be ignored.
Pesticide residues were assessed in rice-vegetable rotation topsoil from tropical riverside basin. The 256 tropical topsoil samples from the Nandu River Basin (NRB) and Wanquan River Basin (WRB) in ...Hainan (China) were taken from 2018 to 2019. A total of 32 current-use pesticides (CUPs) and nine legacy pesticides (LPs) were detected using a method based on a QuEChERS technique. The highest residues were from the fungicide carbendazim (257.2 μg/kg) and the insecticide imidacloprid (139.4 μg/kg). The nine LPs (8 organochlorine pesticides and chlorpyrifos) were detected in 84.4% of the samples with mean concentrations ranging from 0.02 to 675.4 μg/kg. The two most commonly detected pesticides were imidacloprid and emamectin benzoate with detection rates of 96.8% and 91.8%, respectively. The highest total concentration of pesticides from the NRB and WRB was detected in July. The highest average number of multi-residues (16) was recorded in January, compared to 14 and 12 in July and November, respectively. There was a significant correlation between the multiple pesticide residues in soil and vegetable planting types (p < 0.01). There was a significant positive correlation between the pesticide number in topsoil and the pesticide number in water (p < 0.01). The multiple pesticide residues found in surface water were consistent with those in topsoil, suggesting a potential risk of water contamination in the rice-vegetable rotation.
Display omitted
•A rapid comprehensive method was to detect soil residues of a variety of pesticides.•Spatial and temporal distribution of pesticide residues was assessed in tropical soil.•Multi-residues (≥8) were observed in 87.9% of topsoil from tropical vegetable fields.•There was a good correlation between soil pesticide residues and crops-planted modes.•Pesticide residues founded in runoff were consistent with soil pesticide residue data.
Multiple pesticides are heavily applied in crops grown in China's tropics due to the prevalence of diseases and pests, thus posing potential risks to nontarget organisms (e.g., honeybees, lacewings, ...ladybugs, and humans). However, there is little information on this topic. This study is the first assessment of the occurrence, driving factors, and ecological/human health risks of 32 current-use pesticides (CUPs) in 10 frequently-planted crops collected from practicing rice-vegetable rotation systems in Hainan, China. Of the 132 whole crop samples, 44 (33.3 %) residues from ≥8 pesticides were detected in 9.09 % of crop samples with concentrations ≥0.5 mg kg−1. Six pesticide residues, namely carbendazim, pyraclostrobin, acetamiprid, thiophanate methyl, phoxim, and imidacloprid, were detected in 72.7 % of samples, with concentrations ranging from 0.0021 to 13.5 (median = 0.032) mg kg−1. Among them, carbendazim, pyraclostrobin, and acetamiprid were the most common, contributions from 10.2 to 25.5 % and a detection frequency ranging from 25.6 to 56.1 %. The order of total concentration of 32 CUPs (∑32 CUP) concentrations during the year was January > May > November > August and vegetables > rice, being highly related with pesticides usage pattern, crop type, plant accumulation/dissipation and plant lipid contents. The ecological risk quotients (RQs) to four beneficial terrestrial organisms showed that 9.6–39.1 % of samples posed a potential medium or high ecological risk, with 13.6–65.9 % of samples at ∑RQ > 1 being highly affected by the residues of neonicotinoids and emamectin benzoate. Emamectin benzoate (8.9 %) and acetamiprid (5.6 %) exceeded the individual Maximum Residue Levels based on Chinese legislation (GB2763–2021). Moreover, cumulative dietary exposure presented a higher risk to humans in 11.0 and 22.0 % of the cases for acute and chronic, mainly originating from the higher concentration contributors of systemic pesticides in edible crops. Therefore, the regulation and monitoring of CUP residues is imperative for rice-vegetable rotation systems in tropical China to avoid negative effects on nontarget organisms.
Display omitted
•CUPs residues in crops in a tropical rice-vegetable rotation were studied in 2021.•Over 8 of 32 CUPs were detected at ≥0.5 mg kg−1 in 9.09 % crop samples.•The contributions of influencing factors on CUP residues in the crops were identified.•The 13.6–65.9 % samples presented a medium risk to beneficial terrestrial organisms.•High cumulative risks in 22.0 % of crops originated from certain systemic pesticides.
Abstract
Bus reliability has long attracted attention and been extensively studied to enhance service quality. However, existing research generally evaluates bus reliability of specific routes or ...stops. To this end, this study explores en-route bus reliability with real-time data at network scale. Drawing on data of bus automatic vehicle location and smart card usage in Ningbo, China, this study calculates headway-based reliability with the difference between actual and scheduled headway at each stop. To demonstrate the trend of stop-level reliability along a bus route, reliability is graded and visualized on a map with ridership at each stop, which is then weighted with passenger-boarding volume. Route-level reliability is then quantified and mapped, where unreliable service basically concentrates in or extends through the centre area. With respect to network-level reliability, temporal changes are demonstrated with ridership on weekdays and at the weekend. It is observed that on weekdays, the reliability trend is similar to that of ridership, implying a causal relationship between bus travel-time variation and bus waiting-time at stops. Furthermore, a reliability comparison between weekdays in December and October shows the necessity of evaluating periodically and around important events to avoid negative riding experiences that discourage public transport usage. This research provides insights for bus agencies to systematically evaluate service reliability both spatially and temporarily, in order to identify and prioritize the routes and stops where the scope for reliability improvement and the expected benefit are greatest.
Rice-vegetable rotation practices prevail in subtropical and tropical agriculture worldwide, with applications of current-use herbicides (CUHs) vital for nontarget plant control. After application, ...CUHs migrate to environmental compartments, where the occurrence, fate, and ecological risks have not been well characterized. To further understand the occurrence and multiphase partitioning, as well as to evaluate potential drivers and mixture risks in environmental compartments, we analyzed 11 CUHs in 576 samples from 36 rice-vegetable rotations in Nandu River basin, Hainan, China. Samples included soil, water, suspended particulate matter, and sediment collected during both rice and vegetable planting periods. The CUH concentrations varied across environmental compartments, but with high levels of glyphosate and aminomethylphosphonic acid organophosphorus herbicides (OPHs) frequently detected, accounting for 82.3 % to 99.0 % in environmental compartments. Phenoxy acid (PAA) and chloroacetanilide (ANH) herbicides were detected at lower frequencies. Spatiotemporal variation was significantly different among OPHs, ANHs, and PAAs, with geographic and crop-related patterns most evident for CUHs rather than OPHs. Structural equation model, redundancy, and boosted regression tree analyses indicated environmental compartment properties (pH, organic matter, and Fe/Al oxides), crop type, and wet/dry climate were important drivers of spatiotemporal patterns. Fugacity ratios indicated multiphase partitioning and transport of CUHs differed in rice and vegetable planting periods. A new assessment framework based on species-sensitive distributions and environmental compartment weight index indicated unacceptable risks of CUHs (risk quotient >1 in >50 % of sites), with most risks from OPHs (10.5 % to 98.0 %) and butachlor, acetochlor, and 2,4-dichlorophenoxyacetic acid. Risk hot spots were identified as the soil, the central region, and the vegetable planting period, potentially threatening nontarget organisms (e.g., Lemna minor, Glomus intraradices, and Apis mellifera). This study provides a new risk assessment framework and demonstrates the domination of OPHs in CUH contamination and risks in the tropics, thus helping guide policymakers and stakeholders on herbicide management.
This study explored the levels, sources, and risks of PAHs in soils from Yongle Atoll (YLA) and Xuande Atoll (XDA) of the Xisha Islands (XSIs) in the South China Sea, China, under different ...vegetation cover types and soil sources. The results clearly showed that the levels of 16 US EPA priority PAHs (Σ16PAHs) are relatively low in XDA and YLA, with concentrations ranging from not detected (ND) to 151 ng/g (average 15.7 ng/g) and ND to 5.8 ng/g (average 2.1 ng/g), respectively. Three- and four-ring PAHs (62.3% and 53.8%) were widely distributed in YLA and XDA. The average concentration of Σ16PAHs in soils with shrub cover was 1.4, 1.8, 4.8, and 5.0 times higher than that in soils with herbaceous cover, vegetable cover, arbor cover, and no plant cover, respectively. Source analysis using binary diagnostic ratios and the positive matrix factorization (PMF) model suggested that PAHs have similar sources (gasoline/coal combustion, coke production, and biomass combustion), but different contributions in native soil and introduced soil. Moreover, diesel-related vehicular emission was identified to be an additional source of PAHs in native soil. Pearson's correlations revealed strong relationships between PAHs and organic matter or total organic carbon. The cancer risk of PAHs varied among different vegetation cover types and soil sources, following the orders herbaceous cover > vegetable cover > shrub cover > arbor cover > no plant cover and introduced soil > mixed soil > native soil. Nevertheless, the risk remained lower than the risk threshold (10−6), suggesting low carcinogenesis risk in the two atolls. Our findings provide new evidence for the introduction of external vegetation/soil acting as a driver of changes in the characteristics of PAHs in islands, and also underline the negligibility of the PAH increase in soils in the South China Sea, China, from the perspective of health hazards.
Display omitted
•PAH occurrence in soil with different vegetation cover and soil sources were studied.•The most widely distributed PAHs in tropical island soils were 3-/4-ring PAHs.•Both vegetation type and soil source greatly affect PAH levels and compositions.•Differential sources of PAHs were recorded in native and introduced soils.•Elevated risks of PAHs caused by external plant or soil introduction were negligible.
Epidemiological studies have shown that sleep disorders are risk factors for Alzheimer's disease (AD), but the causal relationship between sleep disorders and AD risk is unknown. We aim to assess the ...potential genetic causal association between sleep characteristics and AD, which may contribute to early identification and prediction of risk factors for AD.
Seven sleep-related traits and the outcome phenotype AD were selected from published genome-wide association studies (GWASs). These sleep-related characteristics and instrumental variables (IVs) for AD were extracted. Two-sample and multivariate Mendelian randomization (MR) analyses were performed to assess the causal relationships between sleep characteristics and AD. The inverse variance weighted (IVW), weighted median (WME), weighted mode (WM), MR-Egger regression (MR-Egger) and simple mode (SM) models were used to evaluate causality. The existence of pleiotropy was detected and corrected by MR-Egger regression, MR pleiotropy residuals and outliers.
A two-sample MR study revealed a positive causal association between sleep duration and the onset of AD (OR = 1.002, 95 % CI: 1.000–1.004), and the risk of AD increased with increasing sleep duration. The MR-Egger regression method and MR-PRESSO were used to identify and correct pleiotropy, indicating that there was no horizontal pleiotropy. Heterogeneity was evaluated by Cochran's Q, which indicated no heterogeneity. In a multivariate MR study with seven sleep characteristics corrected for each other, we found that sleep duration remained causally associated with AD (OR = 1.004, 95 % CI: 1.000–1.007). Moreover, we found that after mutual correction, daytime napping had a causal relationship with the onset of AD, and daytime napping may reduce the risk of AD (OR = 0.995, 95 % CI: 0.991–1.000).
This study is helpful for the early identification and prediction of risk factors for AD, long sleep durations are a risk factor for AD, and daytime napping can reduce the risk of AD.
1To explore the causal association between sleep characteristics and AD, and to provide a reference for the prevention of AD.2This study demonstrates that long sleep duration is a risk factor for AD and daytime napping can reduce the risk of AD.3Adjusting sleep duration and daytime napping are important for the prevention of AD.
Multimedia contamination by neonicotinoid (NEO) residues has attracted global attention. However, data regarding the multimedia polluted status under certain typical cropping scenarios and the ...associated risks are scarce. Here, the multimedia occurrence, spatiotemporal distribution, driving factors, transport, and ecological risks of NEOs from tropical rice-vegetable rotation fields were characterized. The heavy NEOs resided in multiple media, and imidacloprid and acetamiprid were the prevailing NEOs, with concentration contributions of 65–80%. The pollution levels of the NEOs, rather than their compositions, exhibited significant spatiotemporal heterogeneity and were highly correlated with the collective (agricultural practices and climate conditions) and differential (e.g., media properties) factors identified using an auto linear regression model. Furthermore, the multimedia transport of NEOs was largely similar but non-negligibly different during the rainy and dry seasons. A new multimedia ecological risk assessment revealed that 50.6% sites were at high risk, and the risk hotspots occurred in the central areas and the winter planting period. The risks were largely contributed by imidacloprid and thiamethoxam, indicating that there were non-ignorable ecological risks. Our results highlight the differential pollution patterns (distribution, transport, and driving factors) of the prevailing NEOs under tropical agricultural scenarios, and the fact that special attention should be paid to the risks posed by NEOs.
Display omitted
•NEO levels in four media from tropical rice-vegetable rotations were first reported.•Multiple NEOs with higher levels co-occurred in soils, plants, water, and sediments.•The relationships between NEOs and their transports on multimedia were indicated.•Collective/differential factors of NEO levels in multimedia were orderly identified.•A novel multimedia-based method ranked NEO risks in tropical rice-vegetable systems.
Rice–vegetable rotations are dominant in (sub)-tropical agriculture worldwide. However, fate and risks of the insecticide flonicamid (FLO) and its main degradates (collectively called FLOMs) in ...multiple substrates from those cropping systems remain largely unknown. In this study, we characterized residual concentrations, driving factors, transport, and potential ecological risks of FLOMs in different substrates in 28 tropical rice–vegetable rotations. Concentrations (median) of FLOMs were 0.013–3.03 (0.42) ng g−1 in plants, 0.012–1.92 (0.23) ng g−1 in soil, 0.029–0.63 (0.126) μg L−1 in water, and 0.002–0.398 (0.055) ng g−1 in sediments. Flonicamid and its metabolite N-(4-trifluoromethylnicotinoyl) glycine were the dominant species in the four substrates (84.1 % to 88.5 %). Plants had the highest levels of FLOMs, with the highest bioconcentration factor in peppers. According to boosted regression trees coupled with a partial least squares structural equation model, levels and composition of FLOMs showed high spatiotemporal and crop-related patterns in different substrates, with patterns highly codetermined by agricultural practices (e.g., crop type and FLO/neonicotinoid/pyrethroid applications), substrate parameters (e.g., pH, organic matter or total organic carbon), and climate features (e.g., wet/dry seasons). Moreover, a fugacity method indicated differences in transport and partitioning patterns in different substrates during rice and vegetable planting periods. Integrated substrate risk assessment of FLOMs contamination was conducted based on species-sensitive distributions and substrate weight index. Although overall risks of FLOM contamination in tropical rice–vegetable rotations were negligible to low, the highest risks were in soils, vegetable planting periods, and a central intensively planted area.
Display omitted
•Flonicamid and its metabolites were examined in tropical rice–vegetable rotations.•Occurrence and concentrations were different in soils–plants and water–sediments.•Transport and partitioning differed between vegetable and rice planting periods.•The structural equation model indicated factors of influence differed among substrates.•Overall risks were low but highest in soils, vegetable periods, and central region.
Microbial communities play crucial roles in the biogeochemical cycling of many important soil elements. Pesticides are known to affect non-targeted soil microorganisms. Glyphosate (GP) and diquat ...(DQ), two commonly used non-selective herbicides, often co-exist in lateritic paddy soil rich in iron/aluminum oxides. However, there is limited information on their co-impact on microbial community structure and diversity in this type of soil. Here, the short-term effects of combined exposure to GP and DQ on microbial diversity and community structure shifts were investigated in lateritic paddy soil from a tropical agricultural region (Hainan, China). The combined utilization dosages of two herbicides were set in three concentrations: low concentration (1 fold of the recommended dosage), medium concentration (10 fold of the recommended dosage) and high concentration (100 fold of the recommended dosage). The structure and diversity of microbial communities were determined via 16S rRNA and ITS gene high-throughput sequencing. The results revealed that Actinobacteria and Proteobacteria were the most sensitive microbial phyla to the combined exposure of GP and DQ in lateritic paddy soil. The combined exposure to GP and DQ increased the abundance of Actinobacteria but significantly inhibited that of Proteobacteria, especially at low and medium concentrations. Compared with CK, mixed herbicide (GP + DQ) had no adverse effects on the richness of bacteria and fungi communities as well as on the diversity of bacteria communities, but it significantly decreased the diversity of fungi communities at high concentrations within 28 days. However, the effects of combined exposure to GP and DQ on soil microbial richness and diversity were not significantly different from those of separate exposure of the two herbicides. In conclusion, the combined application of GP and DQ had no more adverse effects on soil microorganisms. Therefore, these two herbicides can be used reasonably in actual agricultural production.
PDF
