The toxicity of naphthalene to a freshwater microalga, Chlorella pyrenoidosa, and the subsequent recovery of algae from the damage were investigated under two nutrient conditions, either enriched with nitrogen （N） and phosphorus （P）, or starved of N and E Results showed that C. pyrenoidosa was more sensitive to naphthalene under N,P-enriched condition, and the inhibitory rate generally increased at first and then decreased gradually with the evaporation of naphthalene under both nutrient conditions. Enriched N, P reduced the inhibitory rate at initial naphthalene concentration of 5 and 10 mg/L, but enhanced it at 100 mg/L, at which more severe ultrastructure damages were found than those under N,P-starved condition. Observed damages included partly or totally disappearance of nucleolus, nuclear, and plasma membranes. According to the chlorophyll content and cell density measurements, C. pyrenoidosa could recover from naphthalene damage with initial concentrations ≤ 50 mg/L in 7 days under both nutrient conditions, while they could not recover if the initial concentration of naphthalene was at 100 mg/L. Under the N,P-starved condition, the inability of C. pyrenoidosa to recover from the naphthalene damage was consistent with the results of high inhibitory rate, low value of specific growth rate （SGR, 0.05 day-l）, and the severe destruction of cell structure. However, under the N,P-enriched conditions, the observed lower inhibitory rate, higher value of SGR （0.55 day^-1）, and the intact cell structure of most cells suggested that algae could potentially recover from the naphthalene damage.
Synchrotron-based X-ray techniques have been widely applied to the fields of environmental science due to their element-specific and nondestructive properties and unique spectral and spatial resolution advantages.The techniques are capable of in situ investigating chemical speciation,microstructure and mapping of elements in question at the molecular or nanometer scale,and thus provide direct evidence for reaction mechanisms for various environmental processes.In this contribution,the applications of three types of the techniques commonly used in the fields of environmental research are reviewed,namely X-ray absorption spectroscopy (XAS),X-ray fluorescence (XRF) spectroscopy and scanning transmission X-ray microscopy (STXM).In particular,the recent advances of the techniques in China are elaborated,and a selection of the applied examples are provided in the field of environmental science.Finally,the perspectives of synchrotron-based X-ray techniques are discussed.With their great progress and wide application,the techniques have revolutionized our understanding of significant geo-and bio-chemical processes.It is anticipatable that synchrotron-based X-ray techniques will continue to play a significant role in the fields and significant advances will be obtained in decades ahead.
LUO Lei & ZHANG ShuZhen State Key Laboratory of Environmental Chemistry and Ecotoxicology
