In order to study the spatiotemporal variations characteristic of water quality and potential pollution sources of Qujiang River, the water quality data of twelve water quality parameters at three monitoring sections (Tuanbaoling, Baita, and Sailong) from 2015 to 2019 were analyzed by using comprehensive pollution index (CPI) and multivariate statistical techniques (MST). The water quality parameters of Qujiang River basically meet the class 3 value of environmental quality standards for surface water (GB3838-2002, China). CPI varies from 0.62 to 1.06 and the water quality is characterized by slight pollution at the three monitoring sections. Cluster analysis (CA) results show that the months can be divided into three groups on the basis of similarities of the water quality characteristics: Group 1 (dry season), which includes January-April and November–December; Group 2 (flood season), that is, July; Group 3 (flat season), which consists of May–June and August–October. Principal component analysis (PCA) results identify four principal components (PCs) for the dry season and flood season, and five PCs for the flat season, thus explaining 58.23%, 82.94%, and 73.23% of the total variance, respectively. The results of the independent sample t-test show significant differences among the pH, Permanganate index (COD_Mn), Ammonia nitrogen (NH₃–N), Total nitrogen (TN), Fecal coliform (F.coli), and (Flow) Q in the three monitoring sections. Moreover, the pollution is more serious in Baita than Tuanbaoling and Sailong Section and the main problem in the Qujiang River is the high water organic and nitrogen nutrient pollutant content. Hence, monitoring and protection need to be strengthened in the Baita section of Qujiang River.

Elytrigia Desv. is a genus with a varied array of morphology, cytology, ecology, and distribution in Triticeae. Classification and systematic position of Elytrigia remain controversial. We used nuclear internal-transcribed spacer (nrITS) sequences and chloroplast trnL-F region to study the relationships of phylogenetic and maternal genome donor of Elytrigia Desv. sensu lato. (1) E, F, P, St, and W genomes bear close relationship with one another and are distant from H and Ns genomes. Ee and Eb are homoeologous. (2) In ESt genome species, E genome is the origin of diploid Elytrigia species with E genome, St genome is the origin of Pseudoroegneria. (3) Diploid species Et. elongata were differentiated. (4) Et. stipifolia and Et. varnensis sequences are diverse based on nrITS data. (5) Et. lolioides contains St and H genomes and belongs to Elymus s. l. (6) E genome diploid species in Elytrigia serve as maternal donors of E genome for Et. nodosa (PI547344), Et. farcta, Et. pontica, Et. pycnantha, Et. scirpea, and Et. scythica. At least two species act as maternal donor of allopolyploids (ESt and EStP genomes). Our results suggested that Elytrigia s. l. species contain different genomes, which should be divided into different genera. However, the genomes of Elytrigia species had close relationships with one another. Diploid species were differentiated, because of introgression and different geographical sources. The results also suggested that the same species and the same genomes of different species have different maternal donor. Further study of molecular biology and cytology could facilitate the evaluation of our results of phylogenetic in a more specific and accurate way.

Chromophoric dissolved organic matter (CDOM) in aquatic ecosystems can reflect the impacts of human activities on the carbon-cycling process. However, direct evidence of the combined effect of land use and anthropogenic nutrients on CDOM characteristics in river ecosystems is limited. Herein, we collected water samples from 18 sites in the Nanchong section of Jialing River in December 2019 to elucidate how the land use and nutrients affect the source and composition of CDOM through parallel factor (PARAFAC) analysis of excitation–emission matrices (EEMs). First, the absorption coefficient a254 (r2=0.29, p<0.01) and three fluorescence components (humic-like C1 and C2 and protein-like C3) (r2=0.31–0.37, p<0.01) significantly increased with increased urban area, and the four parameters were higher in the urban area than in the suburbs (p<0.05). The correlation between small-size CDOM molecule and cropland was positive (p<0.01). Second, the increase in nutrient levels increased the a254 (r2=0.84 and 0.33, p<0.01) and three fluorescence components (r2=0.30–0.84, p<0.01 or p<0.05). Third, allochthonous CDOM were prevalent in the Nanchong Section of Jialing River, and the proportions of C1 and C2 were 42 and 41%, respectively. Our findings indicated that the variability of source and composition of CDOM significantly depended on urbanization and increased nutrients in the Nanchong Section of Jialing River.

Spatiotemporal changes in the water quality index are important measures with which to analyze water quality. Fifteen water quality indices at the Longdong, Luoguo, and Jinjiang stations in the Panzhihua Section of the Jinsha River Basin from 2016 to 2018 were analyzed using cluster analysis (CA), discriminant analysis (DA), independent sample t-test and correlation analysis. The results of CA showed that the months can be divided into the following groups based on the similarities in the water quality characteristics: group 1 (dry season), January-April and December; group 2 (flood season), August-September; and group 3 (flat season), May-July and October-November. In group 1 the river is remarkably polluted. The main parameters that distinguish the spatial differences are pH level, chemical oxygen demand, chlorophyll a, fecal coliforms, and electrical conductivity. All sections of the river meet the National Level III standard, and the water quality of the Jinsha River is generally good. Spatial results show that the Luoguo station is seriously polluted compared with the other two stations. Significant negative correlation is found between forest land and COD (P < 0.05). Therefore, the management of land use and pollutant discharge should still be strengthened in the Luoguo section to improve the overall water quality of the Jinsha River.