[Wastewater pollution characteristics from typical intensive pig farms in the Pearl River Delta and its ecological risk assessment].

Based on the wastewater quality investigation data from March 2009 to November 2011, wastewater qualities from typical intensive pig farms were assessed in the Pearl River Delta by single and comprehensive pollution index model. The results showed that key pollutants of piggery wastewater were fecal coliform (FC), total phosphorus (TP), chemical oxygen demand (COD) and biochemical oxygen demand (BOD), with their average mass concentrations of 1.98 x 10(9) CFU.L-1, 158.61 mg.L-1, 5 608.68 mg.L-1 and 1984.34 mg.L-1, respectively; key pollutants of biogas slurry were FC, TP, ammonia nitrogen (NH+4 -N) and suspended substance (SS), with their average mass concentrations of 8. 10 x 10(6) CFU.L-1, 81.76 mg.L-1, 476.24 mg.L-1 and 464.58 mg.L-1, respectively. Under the effect of wastewater pollutants, environment surrounding of typical intensive pig farms was seriously polluted, which decreased gradually from piggery wastewater to biogas slurry, and comprehensive pollution indices were 11.41, 6.91, 5.27, respectively. The risk analysis showed that the high-risk wastewater could never be discharged directly and irrigated crops. After the anaerobic treatment, FC, TP, NH+4 -N and SS were still strong factors with the potential ecological risk in the biogas slurry. In the long run, the ecological risk still exists for direct discharge or irrigation of them, and it is necessary to apply further treatment.

[Impact of high salt stress on Apocynum venetum growth and ionic homeostasis].

A pot experiment was conducted in a net room to study the growth responses and related mechanisms of Apocynum venetum treated with different concentrations (100-400 mmol x L(-1)) of NaCl for 30 days. The biomass accumulation, growth rate, root vigor, salt ion content and mineral ion uptake and distribution were measured. Compared with the control, treatment 100 mmol x L(-1) NaCl had lesser effects on the plant dry mass, but decreased the plant fresh mass and growth rate significantly. With increasing NaCl concentration in the medium, the plant dry mass, fresh mass, and growth rate all decreased significantly. The plant root vigor was obviously higher under 100 and 200 mmol x L(-1) NaCl stress, but decreased significantly under 300-400 mmol x L(-1) NaCl stress. With the increase of NaCl concentration in the medium, the Na+ content in A. venetum roots, stems and leaves increased gradually while the K+ content had a slow decrease, the Ca2+ and Mg2+ contents in leaves decreased obviously, and the Ca2+ content in stems and the Mg2+ content in roots increased in different degree. Under NaCl stress, the K+ /Na+, Ca2+/Na+, and Mg2+/Na+ ratios in roots, stems, and leaves decreased markedly, while the selective absorption and transportation of K+ and Ca2+ increased significantly. The stronger ability of salt exclusion and the higher selective absorption and transportation of K+ and Ca2+ were the key adaptive mechanisms of high salt-tolerance of A. venetum.