[Periphytic Algae Community Structure and Its Relation to Environment Factors in the Main Stream of the Songhua River from 2014 to 2019].

Periphytic algae are often used as an indicator to evaluate water quality. Here, the community structure of periphytic algae and its relationship with environment factors were analyzed in the main stream of the Songhua River during the summers of 2014 to 2019. The status and trends in ecological water quality were also evaluated based on bioassessments. Phytoplankton species belonging to 4 phyla and 58 genera were recorded, including 28 Bacillariophyta genera, 17 Chlorophyta genera, 10 Cyanophyta genera, and 3 Euglenophyta genera; Bacillariophyta, Chlorophyta, and Cyanophyta accounted for 48.28%, 29.31%, and 17.24% of the community, respectively. Cell densities varied between 1.29×104 and 8.42×104 ind·cm-3, with an average of 4.35×104 ind·cm-3. The dominant genera were Cyclotella, Melosira, Asterionella, Cymbella, Synedra, Pinnularia, Navicula, and Scenedesmus. The physicochemical water quality showed notable changes during the past six-year monitoring period. Specifically, the dissolved oxygen content increased year on year; ammonia nitrogen, total phosphorus, and total nitrogen first increased and then decreased; and, overall, water quality significantly improved in 2019. Relationship between periphytic algae and environmental factors was further examined using redundancy analysis (RDA), which showed that time was the main factor driving the succession of algal community structure. Dissolved oxygen (DO), ammonia nitrogen (NH4+-N), total nitrogen (TN), total phosphorus (TP), five-day biochemical oxygen demand (BOD), and chemical oxygen demand (COD) were also important environmental variables affecting algal community structure.

[Community of Benthic Diatoms and Their Relationship with Aquatic Environmental Factors in the Tangwang River, China].

To reasonably evaluate the eco-environmental health of the Tangwang River, which is a tributary of the Songhua River in China, community structures of periphyton and cleanliness of the benthic diatom at 24 sampling sites were investigated using McNaughton's dominance index, clustering, and ecotype analysis, while the relationship between the environmental factors and the diatom communities were studied by principal component analysis, Spearman correlation test, and redundancy analysis, in August 2018 (flood season). A total of 99 species or variants of benthic diatoms have been identified, indicating that there were abundant diatoms in the Tangwang River. Achnanthidium minutissimum and other diatoms that can be used as clean water indicators were dominant species in the Tangwang River, which indicates that the eco-environmental quality of the Tangwang River was relatively healthy in the flood season. Of these, the dominant degree of A. minutissimum was 0.32, making it the absolute dominant species in Tangwang River. Sampling sites can be divided into three groups based on clustering analysis. The dominant species of group 1 and group 2 were mainly clean species, indicating that the two groups were in a relatively healthy state. Nitzschia palea, Ulnaria ulna, and other diatoms that can be used as eutrophication indicators were the dominant species of group 3, indicating that group 3 was less healthy than the other two groups. From groups 1 and 2, the results from ecotype analysis showed a decrease in the proportion of polyoxybiontic diatoms and an increase in the proportion of α-mesosaphrobe diatoms, polysaprobe diatoms, oligo-mesotrophic diatoms, mesotrophic diatoms, meso-eutrophic diatoms, and eutrophic diatoms. Compared to the other two groups, the results from ecotype analysis showed a significant increase in the proportion of α-mesosaphrobe diatoms, polysaprobe diatoms, eutrophic diatoms and hypereutrophic diatoms in group 3. The predominant aquatic influencing factors of diatom community structures for the Tangwang River were permanganate index, total nitrogen (TN), and ammonia nitrogen (NH4+-N), of which permanganate index was the main factor for group 2, while TN and NH4+-N were the main factors for group 3. As a result, the eco-environmental quality of the Tangwang River was good, and the benthic diatom was found to be an effective indicator of the nutritional conditions and saprophytic status.

[Research of early-warning method for regional groundwater pollution based on risk management].

Groundwater is the main source of water supply in China, and China's overall situation of groundwater pollution is not optimistic at present. Groundwater pollution risk evaluation and early-warning are the effective measures to prevent groundwater pollution. At present, research of groundwater early-warning method at home and abroad is still at the exploratory stage, and the sophisticated technology has not been developed for reference. This paper briefly described the data and technological demand of the early-warning method in different scales, and the main factors influencing the early-warning results of groundwater pollution were classified as protection performance of geological medium, characteristics of pollution sources, groundwater dynamics and groundwater value. Then the main early-warning indexes of groundwater pollution were screened to establish the early-warning model of regional or watershed scale by the index overlay method. At last, the established early-warning model was used in Baotou plain, and the different early-warning grades were zoned by the model. The research results could provide scientific support for the local management department to protect the groundwater resources.

[Species selection methods in deriving water quality criteria for aquatic life].

The Mann-Whitney U test method was used to analyze the species sensitivity to ammonia toxicity. And based on the analysis, the relationship between species selection method and WQC deriving method was studied by using toxicology, biological taxonomy and sampling-inference theory. Results showed that vertebrate species, especially the Actinopterygii, accounted for the vast majority in the toxicity test species. And the species composition of toxicity test species was inconsistent with the species composition of the ecosystem. Sensitivity to ammonia toxicity among different taxa varied significantly for most species except some species in individual taxa, especially the less sensitive species. The variable coefficient of interspecies decreased with the reduction of biological classification level. To a certain extent, it showed that the species sensitivities in the same taxa to toxicant were more similar than those in different taxa. According to sampling-inference theory, the WQC for aquatic life deriving method belonged to the design-based inference. And taxonomic groups could be used as auxiliary variables to conduct a stratifactory sampling for species selection in WQC deriving which could improve the sampling efficiency and precision.

[Toxicity of nitrate-N to freshwater aquatic life and its water quality criteria].

The toxicity sensitivity of different freshwater aquatic organisms was analyzed using the collected toxicity data in this paper. Three methods were used to estimate the criteria of nitrate to protect the freshwater aquatic life. The results showed that the species sensitivity to nitrate followed the order of Arthropoda > Mollusca > Chordata, and Crustacea > Insecta > Gastropoda > Bivalvia > Amphibia > Actinopterygii. Moreover, the output of assessment factor method, species sensitivity distribution method and USEPA's method was significantly different. Finally, criterias of 87.97 mg x L(-1) and 5.17 mg x L(-1) to protect aquatic life from acute and chronic toxicity were proposed using USEPA's method.

[Effect freezing and thawing cycles on fluorescence characterization of black soil dissolved organic matter].

Fluorescence characterization of soil dissolved organic matter (DOM), which is one of the most important indexes concerning study on soil organic matter, can be effected by freezing and thawing cycles. In this paper, the fluorescence characterization of black soil DOM under the effect of freezing and thawing cycles was studied, using three-dimensional excitation-emission-matrix fluorescence spectroscopic (EEM). Based on the transformation of fluorescence characterization, the influences of humification degree and active humus in black soil were analysed. The result showed, compared with untreated by freezing and thawing cycles, (1) The phenomena red-shift of UV fulvic-like was found in soil DOM. It meant that the aromatization and humification degree increased. (2) Protein-like fluorescence peak was observed in some soil samples, which meant microbial activity was enhanced. (3) Active humus and humification degree are the indexs of soil fertility. The content of TOC in the active humus rose, just the same as the value of humification degree. It meant that soil fertility was improved. (4) Compared with the ratio of UV: visible humic-like fluorescence (r(a,c)), there were positive correlations with the active humus and humification degree. It meant that r(a, c) of soil DOM was one of the indexs on active humus, humification degree and soil fertility effected by freezing and thawing cycles.

[Study of three-dimensional fluorescence spectra for measuring chlorobenzene in water].

Quantitative analysis of chlorobenzene (CB) in water by three-dimensional fluorescence spectrometry was discussed in the present paper. The study showed that there is only one fluorescence peak for CB which lies in the range of excitation wavelength (lambdaex) 210-240 nm and emission wavelength (lambdaem) 330-370 nm. When measuring CB solution of concentration 0.002-0.05 mg x L(-1), the fluorescence intensity was the strongest as lamdaex/lamdaem was 225/340 nm, which presented linear correlation with concentration, and the related coefficient was 0.99967. The study proved that three-dimensional fluorescence spectrometry can be adopted for quantitative analysis of CB in water. With this method, the detection limit was 3.68 X 10(-6) mg x L(-1) and the standard deviation was 0.04% at 90% confidence level.