Nitrogen-fixing cyanobacterium is the general name of cyanobacteria capable of fixing nitrogen and an important resource of microorganisms in the tropical and subtropical regions. A large volume of domestic and international studies have shown that it has broad application prospects in environmental protection, such as remediation of polluted environment, eco-environment monitoring and development of environment-protecting biological materials and bioenergy. Therefore, progresses achieved in the past five years (2013-2017) in the study on application of nitrogen-fixing cyanobacteria to environmental protection were reviewed comprehensively, with focus on treatment of wastewater containing high concentrations of nitrogen and phosphorus, heavy metals, arsenic, or organic pollutants, treatment of waste gas, monitoring of ecological environment, and development of biodegradable plastics, biological catalysts, and new energies, like bio-diesel, hydrocarbons and hydrogen. Moreover, its development tendency was discussed and prospected, in an attempt to provide some reference for further development of the study in this field in China.

In order to explore the concentrations of cadmium (Cd) and lead (Pb) in soils and atmospheric particles and their contributions to rice, rice samples grown in farmlands and the corresponding soils, atmospheric particles were collected, in some typical agricultural areas of southern Jiangsu Province (Suzhou-Wuxi-Changzhou areas). The heavy metal concentrations of samples were determined and analyzed, especially for Cd and Pb. The results showed that the concentration of Cd in soil was much higher than that of the background in Jiangsu soil. The concentration of lead in the dustfall was 382 μg·g^-1. The enrichment coefficients of Cd in rice roots ranged from 0.62 to 3.20, with an average value of 1.91, which indicate that rice root can absorb Cd significantly. The enrichment coefficients of Pb in rice roots varied between 0.02 and 0.06, with an average value of 0.04. Based on the studied data, the average contribution rate of atmospheric particle to Pb concentration in rice grain was 32.7%, while the average contribution rate of atmospheric particle to Cd concentration in rice grain was 15.4%. The results show that Cd in the rice grain is mainly from the contribution of the soil, and rice accumulates Cd by transferring Cd in rice root into grain. The Cd from atmospheric deposition accounts for a small portion of grain Cd. On the contrary, the mobility in soil and the transfer of Pb in rice are weaker than those of Cd, and the Pb concentration in rice grain mainly comes from the contribution of atmospheric particle. Therefore, the different characters and sources of heavy metal will affect the absorption and accumulation of heavy metals in rice. In addition, different farmland environment and atmospheric pollution will affect the Cd and Pb contribution rates of soil and atmospheric particle to rice. Therefore, specific measures should be taken to control pollution sources and adjust the planting structure in accordance with the farmland environment.

Chakou Watershed was located in the typical loess hilly-gully region, and was selected as study area. Ten parameters of AnnAGNPS model were selected for sensitivity analysis, and Morris classification method was used to analyze the sensitivity of the parameters to the simulation results of the model. Based on the results of parameter sensitivity analysis, the model calculation results were verified. The results show that:The number of runoff curves has great positive influence on model output; Channel Manning coefficient and field water-holding capacity have negative influence on model output. The most sensitive parameters affecting the surface runoff output are the number of runoff curves and the field water-holding capacity. The most sensitive parameters affecting the sediment and nutrient output are the number of runoff curves, soil erodibility factor, tillage management factor, topographic factor, and soil and water conservation factor. The spatial distribution of nitrogen and phosphorus pollutants is not consistent, the regional differences are obvious, and the soil nitrogen and phosphorus pools are the main sources of their losses. The model can better reflect the surface runoff process (R²=0.99,Ens=0.99). The results of simulations on sediment, nitrogen and phosphorus are widely inaccurate, but to some extent, it can reflect the trend of soil and water loss and nitrogen and phosphorus pollution, and has certain reference value to the control and management of soil erosion and non-point source pollution.

Roadside ecosystems are common places susceptible to alien plant invasion. It is, therefore, of important significance to conduct hazard risk assessment of alien plants in the ecosystem. A list of alien plants in the roadside ecosystem of the Maoershan National Forest Park was worked out based on data consultation, field surveys and the 9 criteria set by Webb and Presten for determination of native or alien plants. The roadside ecosystem was divided into three levels, high, moderate and low, in terms of disturbance in the light of nature of the road, volume of traffic, width of the road and pavement of the road. The analytic hierarchy process (AHP) was adopted to build a risk assessment index system, which was then used to assess hazard risks of all the alien plants in the list. Results show that there were a total of 39 species of alien plants detected in the roadside ecosystem of the national forest park. However, compared with roadside ecosystems in areas lower in latitude, the roadside ecosystem in the national forest park was lower in number of alien species and hazard risk. The alien plants are mostly herbs from America and now widely distributed in China because of their outstanding uses. Plants of compositae make up the biggest proportion. Among the alien plants in the ecosystem, there are five species high in risk, i. e. Oenothera biennis, Bidens bipinnata, Erigeron annuus, Amaranthus retroflexus and Senecio vulgaris. In the zones, high and moderate in disturbance level, of the roadside ecosystem, the alien plants were rated higher in risk than those in the zone low in disturbance level. A. retroflexus, S. vulgaris, B. bipinnata were rated higher in risk in the zone moderate in disturbance level than in the zone high in disturbance level. To ensure ecological safety of the national forest park, it is essential to mitigate as much as possible the damage to the original environment caused by road construction in the park and pay high attention to post-construction ecological rehabilitation and at the same time to intensify the enforcement of quarantine and removal of alien plants.

To study effects of flooding on growth and photosynthetic physiology of Phoebe zhennan saplings and provide certain theoretical basis for cultivation and water management of P. zhennan saplings, a pot experiment was conducted with the pots planted with 2.5 year-old P. zhennan saplings and flooded. The experiment was designed to have 6 groups or treatments, 5 saplings each, for duration of flooding, i.e. 0(CK), 7, 14, 21, 28 and 35 days. Growth and photosynthetic indexes of the P. zhennan saplings in all the treatments were monitored. Results show:(1) Flooding significantly inhibited growth of the plants, though basal diameter of the plants increased first and then decreased in all the treatments. Net plant height decreased by 43.4%, 59.2%, 59.2% and 80.8% in Treatment 7D, 14D, 21D and 28D, respectively, as compared with CK(0 d), and the plants in Treatment 35D failed to survive; (2) Flooding altered the content and ratio of chloroplast pigments of P zhennan saplings in all the treatments, the contents of chlorophyll a (Chl a) decreased by 17.4%, 22.0%, 38.4% and 52.3%, respectively, while carotenoids/chlorophyll ratio increased by 32.3%, 71.0%, 32.3% and 45.2%, respectively in Treatment 7D, 14D, 21D and 28D, showing a trend of rising first and then declining; (3) Net photosynthetic rate (P_n), transpiration rate (T_r) and stomatal conductance (G_s) were declining significantly with the stress going on and, decreased by 89.6%, 98.2% and 98.7%, respectively in Treatment 28D. However, the concentration of carbon dioxide (C_i) between cells significantly increased by 216.2% in Treatment 28D; And (4) in the plants under stress, light compensation point (L_cp) and CO₂ compensation point (C_cp) showed an increasing trend, while the max net photosynthetic rate (P_n,max) and light saturation point (L_sp) decreased dramaticly. In conclusion, P. zhennan saplings exhibited showed low resistance to flooding stress, which significantly inhibited air exchange and photosynthetic rate and weakened the plants' ability to make use of light and CO₂, and hence their photosynthetic capacity. In the experiment, the saplings exhibited their physio-ecological traits of low resistance to flooding. Most of the saplings began to wilt and die after 28 days of flooding and all the saplings died after 35 days of flooding.

The research on ecological vulnerability, as a hot spot and important orientation of the study on ecology, is of important guiding significance to regional environmental protection, rational planning and utilization of land resources and sustainable development. Landscape vulnerability index was established based on 3S technology and theories and methods of landscape ecology for analysis of characteristics of the variation of landscape pattern and landscape vulnerability in the study area as a whole. To proceed with relatively small scaled controllable unit, 53 administrative villages in the studied area were used as evaluation units to explore characteristics of the variations of landscape ecological vulnerability and its spatiotemporal distribution in the Caohai Wetland. Results show:(1) During the period from 1995 to 2015, woodland and grassland decreased much in area, while construction land and water surface kept on increasing. Landscape vulnerability index of the study area expanded gradually in the past 20 years, but in terms of vulnerability index, the fractions of the landscape remained almost unchanged, i. e. grassland > woodland > cultivated land > construction land > water surface; (2) During the period from 1995 to 2015, villages high and moderate in landscape vulnerability were concentrated mainly around the study area and decreasing in number, while villages, so so and potential in landscape vulnerability were mostly in the central part of the study area and increasing in number; (3) The ecological vulnerabilities of the villages exhibited significant autocorrelations, but spatial agglomeration of the villages similar in landscape vulnerability declined somewhat; and (4) The spatial distribution of landscape ecology vulnerability of the administrative villages was shifting from the low-low type of agglomeration to the high-high type and most of the villages no longer exhibited much spatial autocorrelation, and no low-high type of agglomeration appeared.

Wetland conversion to paddy field is a typical land use change in the middle and lower reaches of the Yangtze River. Poyang Lake is the largest fresh water lake in China. There were total 1 466.9 km² Poyang Lake wetlands that were converted to croplands, and most of them were used as paddy cultivation. Soil samples were collected from Poyang Lake reclaimed paddy fields with different tillage years. Subsequently, soil total organic carbon (SOC), heavy fraction organic carbon (HFOC), light fraction organic carbon (LFOC) and microbial biomass carbon (MBC) were measured. The objective was to clarify the effect of tillage years on soil organic carbon fractions in the Poyang Lake reclaimed paddy fields. Results indicate that the top 30 cm soil HFOC and LFOC ranged from 5.89 to 24.01 and 0.47 to 4.14 mg·g^-1, respectively, whereas MBC varied from 12.43 to 850.53 mg·kg^-1. All three organic carbon fractions were significantly positively correlated with soil total organic carbon. HFOC, LFOC and MBC were significantly affected by tillage years. The contents of all three organic carbon fractions increased with tillage years. However, the ratios of various organic carbon fractions to soil total organic carbon differed among the three components and varied with soil depth. After 50 years tillage, HFOC in the reclaimed paddy fields was relatively stable, however, the ratio of HFOC to SOC declined in comparison to natural wetlands. Hence, to some extent, reclamation declined the stability of soil carbon pool.

Rotation or intercropping of hyperaccumulator and crop is an important way to realize the production while remediation on heavy metal polluted soils. The influence of phosphate (P) and zinc (Zn) amendments at rice growth season on cadmium (Cd) uptake in rice and succeeding Sedum plumbizincicola was studied in a pot experiment using Cd contaminated acid red soil through the rotations of rice and S. plumbizincicola. The results show that at the high P (400 mg·kg^-1) treatment soil CaCl₂ extractable Cd decreased compared with the control (100 mg·kg^-1), and the Cd concentration in rice straw was not effected obviously, but the Cd transfer coefficient from straw to grain was significantly decreased in the rice season. The soil CaCl₂ extractable Cd concentration reduced under Zn treatment, and the Cd concentration in brown rice was reduced from 0.21 mg·kg^-1 (control) to 0.15 mg·kg^-1. The P and Zn treatment at rice season had no obvious influence on the shoot biomass and Cd concentration of S. plumbizincicola at next season. Zn treatment at rice season increased Zn accumulation in rice and S. plumbizincicola. The P and Zn treatment at rice season could reduce the risk of Cd accumulation in rice and had no obvious effect on Cd removal by succeeding S. plumbizincicola. So adding Zn and P can be regarded as an adjustable way to treat Cd polluted soil with production while remediation.

Two kinds of FeCl₃ modified biochar, prepared separately out of Typha angustifolia and Phragmites communis, two aquatic plants, were used as adsorbent and potassium nitrate solution was as adsorbate in this study to simulate removal of nitrate-N by biochar, and further to analyze adsorption kinetics and adsorption isotherm characteristics of the two modified biochars and their originals, and explore effects of biochar application rate, adsorption duration, and initial concentration and pH of the adsorbate on nitrate-N adsorption by the two biochars, with the aid of infrared spectroscopy (IR), scanning electron microscopy (SEM) and elemental assay. Results showed that nitrate-N adsorption of the two modified biochars fitted the pseudo-secondary adsorption kinetics. The maximum adsorption capacity q_m of the FeCl₃ modified Typha angustifolia biochar (XP-Fe) and FeCl₃ modified Phragmites communis biochar (LW-Fe) was 15.55 and 10.63 mg·g^-1, respectively. Reduced pH of the adsorbate facilitated nitrate-N adsorption by XP-Fe and LW-Fe. XP-Fe was higher than LW-Fe in nitrate-N adsorption capacity.

In order to solve the problem of nitrate contamination in groundwater, dynamic simulation column studies on compost and compost+iron chip promoting in-situ bio-remediation were carried out. The objectives were to investigate the operating performances, to explore the changes in hydrochemical parameters, to analyze the transformation processes of nitrate, to identify the effects of groundwater velocity and influent nitrate concentration, to broaden the types of fiber-based solid organic carbon sources and to improve their denitrification rates. Results show that NO₃^- removal efficiencies of compost and compost+iron chip were 75.08%-79.57% and 82.24%-86.48%, respectively. Using compost for in-situ biological denitrification is feasible and efficient, and compost+iron chip performs better for nitrate removal via hydrogenotrophic denitrification. At the beginning of operation (≤ 8 d), compost readily led to the effluent NO₂^- concentration above the Chinese drinking water standard (GB 5749-2006), and meanwhile compost+iron chip readily resulted in the effluent NH₄⁺ concentration above the Chinese drinking water standard (GB 5749-2006). Denitrification rates of compost and compost+iron chip were 9.69 and 11.30 g·m^-3·d^-1, respectively, which were significantly higher than the value of saw dust (0.30 g·m^-3·d^-1). Total organic carbon (TOC) increment (≤ 18.34 mg·L^-1) was kept stable during the period of 25-100 d for compost. During the period of 0-100 d for operation, effluent pH was always lower than the corresponding influent value for compost. The similar trends of TOC and pH were observed for compost+iron chip. After 10 d, most of the influent NO₃^--N was transformed into gaseous nitrogen in the presence of compost and compost+iron chip, respectively. Removal efficiency decreased from 76.84% to 48.32% for compost and from 85.22% to 55.98% for compost+iron chip with Darcy velocity increasing from 0.5 to 2.0 m·d^-1. Removal efficiency decreased from 76.44% to 44.87% for compost and from 85.42% to 65.46% for compost+iron chip with influent NO₃^- concentration increasing from 100.58 to 301.02 mg·L^-1. Darcy velocity and influent nitrate concentration both have significant effects in biological denitrification performance of compost and compost+iron chip, respectively.

Microcystis aeruginosa bloom is a major harmful Cyanobacteria bloom in lakes and reservoirs. Researches on methods for prediction and forecasting of algal blooms are of important significance to mitigating harm of the blooms. Based on the CE-QUAL-W2 model, indoor growth of Microcystis aeruginosa, a dominant species, typical of Cyanobacteria blooms was simulated with the aid of the PIKAIA genetic algorithm for analysis of sensitivity of different growth kinetci parameters to its growth, and threshold of sensitive parameters. Results show that the CE-QUAL-W2 model is good at simulating indoor growth process of Microcystis aeruginosa, and AG (maximum algal growth rate), AS (algal settling rate), ASAT (light saturation intensity at maximum photosynthetic rate), ALGN (ALGP)[stoichiometric equivalent between algal biomass and nitrogen (phosphorus)], and ACHLA (ratio between algal biomass and chlorophyll a) are the sensitive parameters that affect growth of Microcystis aeruginosa. Among them, AG and ACHLA are positively related to Chlorophyll a peak, while AS, ASAT, ALGP and ALGN are negatively related. Besides, AS and ACHLA are positively related to the time Chlorophyll a peak appears, while AG, ALGP and ALGN are negatively related. Variation of ACHLA can only multiply or reduce Chlorophyll a by time, but it will not affect the time the peak appears. Optimal values of the six parameters are defined as follows:AG=7.526 8 d^-1, AS=0.002 2 m·d^-1, ASAT=102.774 4 W·m^-2, ALGP=0.000 5, ALGN=0.041 3, ACHLA=0.125 8 mg·μg^-1.

Rainfall-runoff processes are important driving factors of nitrogen loss in cropland. During the processes, dissolvable nitrogen in the topsoil of cropland gets dissolved and migrates into surface runoff. As a main way of dissolved nitrogen exporting from cropland, nitrogen dissolution from topsoil needs to be precisely estimated, which may help improve and perfect the estimation of non-point source nitrogen pollution load. Based on the concept of scouring and oozing coefficient in the calculation method of dissolved pollutant loads in the large scaled models, an approach to estimating nitrogen dissolution in plain river network areas was developed. A plot of dryland field typical of the plain river network area of Dafeng City in the north of Jiangsu Province was selected for test run of the proposed approach. The scouring and oozing coefficient with respect to topsoil nitrogen dissolution during a complete rainfall event was determined through real-time observation and modeling, and comparison was done with previous studies. The proposed approach is found to be a useful supplement for modeling and experimental studies on estimation of nitrogen release from topsoil of the dryland fields in the plain river network areas.

In order to rapidly determine difference between biochars produced at different temperatures in property, partial least squares (PLS) and least squares support vector regression (LSSVR) were used to predict properties of the biochars produced out of corn stalk through pyrolysis at 300, 400, 500 and 600℃ and then principal component analysis (PCA) and linear discrimination analysis (LDA) were done of the biochars to determine which one was pyrolyzed at what temperature. Prediction and analysis of the biochars for properties such as contents of ash, fixed carbon, carbon (C), and hydrogen (H) was performed using a near-infrared spectroscopy coupled with several statistical approaches, with root mean squares error of prediction (RMSEP) being 0.024 2, 0.029 9, 0.016 9 and 0.001 7, residual predictive deviation (RPD) being 1.32, 3.50, 3.44 and 5.66, and corresponding coefficients determination (R²) being 0.974 2, 0.912 6, 0.912 5 and 0.927 4, respectively. Moreover, the determination of temperature at which the biochars had been pyrolyzed was done successfully with 100% accuracy with LDA. Results show that compared with the wet chemical method, near-infrared spectroscopy features rapidity and non-destructiveness in analyzing biochar properties. The proposed method is of great significance to wide application of biochar.