[Effects of Polystyrene Nanoplastics (PS-NPs) on the Physiology of Allium sativum L.]

The pollution of micro/nanoplastics in the natural environment is becoming increasingly serious, but the potential effects of nanoplastics on crops remain unclear. In the present study, the effects of polystyrene nanoplastics (PS-NPs) with a particle size of 80 nm on the chlorophyll content, antioxidant enzyme activity, and nutritional quality of Allium sativum L. were explored via hydroponic culture. The results showed that the chlorophyll contents in leaves of A. sativum treated with PS-NPs were significantly lower than those in the control, indicating that the synthesis of chlorophyll was inhibited. The superoxide dismutase (SOD), ascorbate peroxidase (APX) activities, and proline contents in leaves of A. sativum initially increased but then decreased with the increase in ρ(PS-NPs). The activity of guaiacol peroxidase (POD) increased with the increase in ρ(PS-NPs) for 10 days of treatment; however, it was inhibited for 20 days of treatment. The malondialdehyde (MDA) content increased with the rise in ρ(PS-NPs). When ρ(PS-NPs) increased to 100 mg·L-1, the MDA content in leaves of A. sativum increased by 43.24% and 89.70% for 10 and 20-day treatments, respectively, compared with those in the control. Meanwhile, the contents of soluble protein, soluble sugar, and vitamin C were higher than those in the control for 10-day treatments; however, the vitamin C content decreased by 26.53% after 20 days of treatment. These results indicated that PS-NPs had a significant oxidative stress on A. sativum, and a high concentration of PS-NPs stress would have deleterious effects on the nutritional quality of A. sativum.

[Distributions of Arsenic Species in Different Eutrophic Waters of Lake Taihu and Their Relations to Environmental Factors].

A detailed field survey of arsenic species and water quality parameters was conducted in different eutrophicated regions of Lake Taihu (Zhushan Bay, Meiliang Bay, Gonghu Bay and Southern Taihu) in summer and winter. Furthermore, spatial and seasonal distributions of arsenic species and their relations to water quality parameters were investigated with multivariate analysis techniques. Higher average contents of total arsenic (TAs), arsenate[As(Ⅴ)], arsenite[ As(Ⅲ)] and methylarsenicals [sum of monomethylarsenic acid (MMA) and dimethylarsenic acid (DMA)] were observed in northern regions (including Zhushan Bay, Meiliang Bay, and Gonghu Bay) (TAs:2.58-3.34 µg·L-1, As(Ⅴ):1.37-2.34 µg·L-1, As(Ⅲ):0.53-0.64 µg·L-1, methylarsenicals:0.16-0.36 µg·L-1), compared to those in Southern Taihu (1.73, 1.10, 0.31, 0.10 µg·L-1). The results exhibited obvious spatial characteristics of arsenic species in the surface water of Lake Taihu. Besides, average values of TAs, As(Ⅴ), As(Ⅲ) and methylarsenicals in summer were 3.40, 2.06, 0.73 and 0.25 µg·L-1, respectively, higher than those in winter (1.78, 1.10, 0.30, 0.17 µg·L-1), reflecting significant seasonal characteristics of arsenic distribution. Factor analysis revealed the significant relationships of TAs and As(Ⅴ) with several water quality parameters, which suggested that spatial and seasonal distributions of TAs and As(Ⅴ) in Lake Taihu were affected by external pollution and internal arsenic release from sediments. Redundancy analysis further indicated significant effects of total phosphorus (TP) and total iron (TFe) on the distributions of TAs and As(Ⅴ). At the mean time, the above statistical analyses exhibited that As(Ⅲ) and methylarsenicals were positively correlated with chlorophyll-a (Chl-a). A large amount of microalgae could accumulate As(Ⅴ) and transform it more strongly to As(Ⅲ) and methylarsenicals in eutrophic regions when compared to mesotrophic region,especially in summer, reflecting the regulation of microalgae on arsenic biotransformation.

[Ecological protection and sustainable utilization of Erhai Lake, Yunnan].

Economic development and increase of population pressure have caused a series of ecological environmental problems of Erhai Lake. These problems include: (1) Quickening of eutrophication process, (2) Decrease of water level and water resources, (3) Habitat deterioration of lakeside zone, and (4) Overfishing and slow depletion of aboriginal fish. Pollutant loading of Erhai Lake is as follows: COD(Cr) 3 008 t x a(-1), TP 137.31 t x a(-1), TN 1 426.35 t x a(-1). According to the mestrophic target of water quality, loading of nitrogen and phosphorus is far above environmental capacity of Erhai Lake. Erhai Lake is now in a pivotal and hypersensitive period of trophic states change, and the position is very critical. Therefore, some countermeasures to solve the problems are presented as follows: (1) Defining the dominant functions of Erhai Lake, (2) Paying attention to the adjustment of the industrial structure and distribution in the course of urbanization, (3) Setting up lakeside zone reserve, (4) Strengthening the control of tourism pollution, (5) Properly adjusting the water level of Erhai Lake, and (6) Some ecological engineering measures for water resources protection in the basin should be taken through collecting and treating of urban sewages, ecological rehabilitating of the main inflowing rivers, constructing of ecological agricultures and improving of rural environment, ecological restoring of aquatic ecosystem, and soil and water conservation.