Analysis of potential volatile organic compounds in Sitophilus zeamais (Coleoptera: Curculionidae)-infested wheat based on lipid oxidation-a reference to early and rapid detection method.

The maize weevil, Sitophilus zeamais Motschulsky, is a hidden pest that presents serious risk to grain quality during postharvest storage. Lipid-derived volatile detection is considered a key reference for early prediction of S. zeamais infestation. However, the exact compositions of fatty acids and volatile organic compounds (VOCs) in S. zeamais-infested wheat are yet to be determined. In this study, we aimed to explore the effect of S. zeamais infestation on lipid metabolism in wheat infested with S. zeamais eggs (4 days), larvae (20 days), pupae (35 days), and adults (45 days). Compared to those in the control group, the activities of lipid oxidation enzymes, such as lipase, lipoxygenase, and alcohol dehydrogenase, increased by 82.73%, 105.12%, and 487.86%, respectively, during the storage period of 1 life cycle of S. zeamais. Additionally, the fatty acid composition of S. zeamais-infested wheat was significantly altered (palmitic acid [1.10-fold], oleic acid [1.07-fold], and linoleic acid [0.95-fold]). Furthermore, 91 VOCs were identified in all wheat samples; then, multivariate statistical analyses categorized these samples into 4 groups: uninfested, longer storage, lightly infested, and heavily infested. Moreover, 31, 26, and 45 potential VOCs were identified to distinguish uninfested wheat from those in the other 3 groups. These results demonstrated that S. zeamais infestation induces an elevation in lipid-related enzymatic activities, which potentially leads to a decrease in lipid content alongside the production of specific VOCs (undecan-4-olide, heptaldehyde, and 2-nonenal). These findings provide novel insights for rapidly identifying grains infested by hidden pests and effectively managing these pests during grain storage.

Impacts of Seasonal Variation on Organochlorine Pesticides in the East China Sea and Northern South China Sea.

To investigate the characteristics of historic-use organochlorine pesticides (OCPs) in the marginal seawater of China, we examined the seasonal and spatial distributions of hexachlorobenzene (HCB), hexachlorocyclohexanes (HCHs), and dichlorodiphenyltrichloroethane (DDTs) in the northern South China Sea (NSCS, 18-23° N) and East China Sea (ECS, 26-32° N). Seasonally, in the NSCS, the significantly higher concentrations (p < 0.05) of HCB, HCHs, and DDTs were found in summer, autumn, and summer through autumn, respectively. In the ECS, the higher concentrations were found in summer through winter, autumn, and summer. Spatially, HCB concentrations were significantly higher in the NSCS than in the ECS during all seasons except winter. During all four seasons, concentrations of HCHs were significantly higher in the NSCS than in the ECS. In summer and autumn, concentrations of DDTs were significantly higher in the NSCS than in the ECS, while no significant differences were found in spring and winter. Generally, regional usage, river-influenced coastal plumes, phytoplankton abundances, and ocean currents played crucial roles in the input, transport, degradation, and dilution of OCPs. These dynamic factors along with the seasonally alternating monsoon directly influenced the seasonal and spatial characteristics of OCPs. Furthermore, the profiles and diagnostic ratios of HCHs and DDTs revealed highly weathered OCP residues, attributed to eroded soils carried by surface runoff and long-range oceanic and atmospheric transport.

Seasonal Variation of Terrigenous Polycyclic Aromatic Hydrocarbons along the Marginal Seas of China: Input, Phase Partitioning, and Ocean-Current Transport.

To study the spatial distributions and seasonal differences of concentrations, source identification, and phase partitioning of polycyclic aromatic hydrocarbons (PAHs) in surface water, intensive sampling was carried out along the marginal seas of China in four seasons. In the northern South China Sea (SCS), the highest PAH levels occurred in the summer (July to August) and autumn (October to November). In the East China Sea (ECS) and the Yellow Sea, the highest occurred in the summer (August) and winter (December). In all areas, the lowest PAH levels were found in the spring (May to June). The estimated mass inventory of PAHs in the surface water (0-5 m) of the northern SCS and ECS accounted for less than 8% of PAHs outflow into the offshore environment. That showed the consistent seasonal variation with PAHs levels. Land- and ocean-based emissions, surface runoff, and the open seawater dilution were the most important environmental factors influencing the seasonal heterogeneity and the spatial distributions of PAH in the surface water. The decline of observed organic carbon normalized partition coefficients in the four seasons was probably affected by the presence of submicrometer-sized soot particles accompanying the PAH outflow from China.

[Characteristics and sources of PM10-bound PAHs during haze period in winter-spring of Xiamen].

PM10 samples were collected at Huli (industrial zone) and Dadeng Island in Xiamen from December 2008 to March 2009. Nineteen polycyclic aromatic hydrocarbons (PAHs) during haze and non-haze periods were determined by GC/MS. Combined with the meteorological data, the differences of chemical composition and source of PAHs were compared. During sampling periods, the concentrations of PM10-bound PAHs ranged from 12.93 to 79.27 ng x m(-3) with the average of 42.28 ng x m(-3), which were almost three times higher than those in the winter of 2004. PAHs concentrations were much higher during the haze periods than those in the non-haze periods. Meanwhile, during the haze periods the percentages of lower molecular weight PAHs such as Phe, Fluo and Pyr decreased significantly, on the contrary, individual components of BbF, BkF, BaP, Per, Icdp, BghiP and COR were more abundant. The main sources of PAHs were estimated by the Principal Component Analysis method and the contributions of various pollution sources to PAHs were calculated by the Multiple Linear Regression method. Results showed that the main pollutant sources of PM10-bound PAHs in winter-spring of Xiamen during the haze period were vehicle emission plus natural gas, coal combustion and coke oven, their contribution rates were 62.7%, 28.1% and 9.2%, respectively. During non-haze periods, the main pollutant sources identified were the same and the contribution rates were 48.6%, 36.9% and 14.5%, respectively. In winter-spring of Xiamen, PM10-bound PAHs were more influenced by local emission sources during the haze periods; coal combustion emissions in north China had a big contribution to PAHs during the non-haze periods.

Seasonal variation for the ratio of BaP to BeP at different sites in Great Xiamen Bay.

From March 2008 to February 2009, PM(10) samples were collected and analyzed for polycyclic aromatic hydrocarbons (PAHs) at eight sampling sites in Great Xiamen Bay, China. Analyses of the seasonal and spatial variations of these compounds revealed the following results. Significantly high levels of PAHs were found in the winter compared to the summer, sometimes exceeding 100 ng m(-3), and the spatial variations were influenced most by the sampling site surroundings. Composition profiles of PAHs of an urban and a rural site were shown to be very similar with a positive correlation coefficient larger than 0.9 at the 0.01 level of significance for the same season. Diagnostic ratios, together with principal component and multiple linear regression analysis, showed that more PAHs were from grass/wood/coal combustion in winter than in other seasons. The ratios of benzo[a]pyrene to benzo[e]pyrene (BaP-BeP) in winter and fall were 0.6-1.7 times higher than those in spring and summer, suggesting the importance of local emissions of PAHs. The BaP-BeP ratios in Kinmen were generally lower than those in Xiamen, indicating that the aging degree of PAHs was higher in Kinmen than in Xiamen. The external input of PAHs from upwind urban and industrial areas was one of the key factors causing high levels of PAHs in PM(10) in Great Xiamen Bay in winter.