Effects of sulfate on the photosynthetic physiology characteristics of Hydrocotyle vulgaris under zinc stress.

The effects of sulfate on the zinc (Zn) bioaccumulation characteristics and photophysiological mechanisms of the ornamental plant Hydrocotyle vulgaris were explored using a hydroponic culture under three Zn concentrations (300, 500 and 700mgL-1 ) with (400µmolL-1 ) or without the addition of sulfate. Results showed that: (1) tissue Zn concentrations and total Zn contents increased with increasing hydroponic culture Zn concentrations; and sulfate addition decreased Zn uptake and translocation from roots to shoots; (2) Zn exposure decreased photosynthetic pigment synthesis, while sulfate changed this phenomenon, especially for chlorophyll a under 300mgL-1 Zn treatment; (3) Zn exposure decreased photosynthetic function, while sulfate had positive effects, especially on the photosynthetic rate (Pn ) and stomatal conductance (Gs ); and (4) chlorophyll fluorescence parameters related to light energy capture, transfer and assimilation were generally downregulated under Zn stress, while sulfate had a positive effect on these processes. Furthermore, compared to photosynthetic pigment synthesis and photosynthesis, chlorophyll fluorescence was more responsive, especially under 300mgL-1 Zn treatment with sulfate addition. In general, Zn stress affected photophysiological processes at different levels, while sulfate decreased Zn uptake, translocation, and bioaccumulation and showed a positive function in alleviating Zn stress, ultimately resulting in plant growth promotion. All of these results provide a theoretical reference for combining H. vulgaris with sulfate application in the bioremediation of Zn-contaminated environments at the photophysiological level.

Microbial degradation of petroleum characteristic pollutants in hypersaline environment, emphasizing n-hexadecane and 2,4 di-tert-butylphenol.

In this paper, nine strains of salt-tolerant petroleum-degrading bacteria were applied to an biological aerated filter. Simulating the degradation of high-salinity petroleum wastewater with n-hexadecane and 2,4-ditert-butylphenol as the primary pollutants and analyzing the structure of the biofilm at various salt concentrations. According to the results, when the salinity was 4%, the COD removal efficiency reached 74.34%. Various halotolerant microorganisms have adapted to various salt concentrations. At a salinity of 3%, n-hexadecane exhibited the best degradation effect, with a rate of 83.21%. Shewanella, Acinetobacter, and Marinobacter were the predominant bacterial groups at the time. At 4% salinity, Acinetobacter and Pseudomonas were the predominant bacteria, and the average 2,4-ditert-butylphenol degradation rate was the highest at 63.02%. This study provided an experimental basis for further studying the biological treatment of high-salinity petroleum wastewater.