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Changes in land use and landscapes have a direct impact on the regional eco-environment. It is of great importance to understand the change pattern of land use, landscapes, and their mechanism on the ecological quality, especially ecologically fragile areas. The northern sand-prevention belt (NSPB) is an important ecologically fragile area in China, which has a large influence on the ecological security of the entire country. Based on the land use data of the NSPB in 2000, 2010, and 2018, we studied the spatio-temporal characteristics of land-use change and change in landscape patterns. The ecological quality represented by the remote sensing-based desertification index (RSDI) was calculated using satellite images. The effects of land use and landscape patterns on RSDI were analyzed by geographic detector and geographically weighted regression. Important results include the following: (1) Land-use change in the study area was high during 2000–2010 but slower in 2010–2018. Grassland was the largest land-use type in the NSPB, and varied greatly in terms of total change and spatial location. The major change was the conversion between dense and moderate grass, with 64,860 km2 of dense grass turning into moderate grass, and 48,505 km2 changing the other way. (2) Among the four landscape metrics, patch density, area-weighted mean fractal dimension, and edge density increased, whereas the aggregation index decreased, which indicated that the landscape was developing towards heterogeneity, fragmentation, complexity, and aggregation. Spatially, the landscape metrics presented a strip distribution in the east of the NSPB. (3) The effects of various land-use types on ecological quality, from high to low, were unused land, woodland, dense grass, cropland, moderate grass, built-up land, sparse grass, and waterbody. The areas where the ecological quality was greatly affected by the landscape patterns were concentrated in the agro-pastoral ecotone and the forest-steppe ecotone. The results of this study reveal the trends of land use and landscape patterns in the NSPB over 18 years and can help to understand their mechanism on ecological quality, which is of significance for the management of this area. • LUC in the NSPB was active from 2000 to 2010 and weakened from 2010 to 2018. • The landscape was developing towards heterogeneity, fragmentation, complexity, and aggregation. • The effects of land use and landscape on ecological quality were studied by GD and GWR. [ABSTRACT FROM AUTHOR]

Dissipation, residues and risk assessment of lufenuron during kumquat growing and kumquat processing were investigated under field and household conditions. The QuEChERS technique with high-performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS) was used to detect lufenuron residues content in kumquats and its processed products. The recoveries were 82.3–102.8% at a spike level of 0.005–0.5 mg kg−1, the relative standard deviations (RSDs) were 1.1–9.4%. The dissipation kinetics data showed that lufenuron in kumquats were degraded with the half-lives of 9.12–12.60 days. The terminal residues of lufenuron in kumquats were 0.064–0.107 mg kg−1 after application one times with a pre-harvest interval (PHI) of 14 days under the designed dosages. The juicing process can significantly reduce the residues of lufenuron in kumquats juice, and the processing factor (PF) value of juicing process was 0.15. The chronic dietary exposure assessment risk quotient (RQ) values of lufenuron in kumquats fruit and juice for different consumers were 0.71–2.13% and 0.37–0.86%, all of the RQ values were lower than 100%. The results from this study are important reference for Chinese governments to develop criteria for the safe and rational use of lufenuron on kumquats and monitor the quality safety of agricultural products and protecting consumer health. • Residue behaviorof lufenuron in kumquats during growing and processing is reported for the first time. • The degradation half-life of lufenuron showed that lufenuron degrades relatively slowly. • The juicing process can significantly reduce the residues of lufenuron in kumquats juice. • Dietary exposure risks associated with lufenuron in kumquats fruit and juice in China are all not a health concern. [ABSTRACT FROM AUTHOR]