Perfluorinated sulfonic acids (PFSAs) and perfluorinated carboxylic acids (PFCAs), as well as the replacement for the phase-out C8 PFSAs were determined in the liver samples of Indo-Pacific humpback dolphins (Sousa chinensis) and finless porpoises (Neophocaena phocaenoides) from the South China Sea between 2002 and 2014. Levels of total perfluoroalkyl substances (PFASs) in samples ranged from 136-15,300 and 30.5-2,720 ng/g dw for dolphin and porpoise, respectively. Significant increasing trends of several individual PFCAs and perfluorobutane sulfonate (PFBS) were found in cetacean samples from 2002 to 2014, whereas no significant temporal trends of ∑PFASs appeared over the sampling period. This pattern may be attributed to the increasing usage of PFCAs and C4-based PFSAs following the restriction/voluntary withdrawal of the production and use of perfluorooctane sulfonate (PFOS) related products. In addition, significantly increasing temporal shifting trends of PFOS to PFBS were observed in the dolphin liver samples. This pattern may be attributed to the substitution of PFOS by its alternative, PFBS. The highest levels of PFOS were observed in the liver samples of dolphin as compared with other marine mammal studies published since 2006, indicating high contamination of PFAS in the South China region. An assessment of relatively high concentrations of C8-based PFASs in the liver samples of cetaceans predicted that concentrations of PFOS would be expected to affect some proportion of the cetacean populations studied, based on the toxicity thresholds derived.
A long-term fertilization experiment was set up in northern Xinjiang, China to evaluate the dynamics of crop production and soil organic carbon (SOC) from 1990 to 2012 with seven fertilization treatments. The seven treatments included an unfertilized control (CK) and six different combinations of phosphorus (P), potassium (K), nitrogen (N), straw (S) and animal manure (M). The balanced fertilization treatments had significantly (P<0.05) higher average yields than the unbalanced ones. The treatment with 2/3 N from potassium sulfate (NPK) and 1/3 N from farmyard manure (NPKM) had a higher average yield than the other treatments. The average yields (over the 23 years) in the treatments of NPK, and urea, calcium superphosphate (NP) did not differ significantly (P>0.05) but were higher than that in the treatment with urea and potassium sulfate (NK; P<0.05). The results also show that the highest increases in SOC (P<0.05) occurred in NPKM with a potential increase of 1.2 t C/(hm 2 •a). The increase in SOC was only 0.31, 0.30 and 0.12 t C/(hm 2 •a) for NPKS (9/10 N from NPK and 1/10 N from straw), NPK and NP, respectively; and the SOC in the NP, NK and CK treatments were approaching equilibrium and so did not rise or fall significantly over the 23-year experiment. A complete NPK plus manure fertilization program is recommended for this extremely arid region to maximize both yields and carbon sequestration.
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