A 2011 drought event affecting distribution of nutrients and chlorophyll in the Zhujiang River estuary

During the summer of 2011,a severe drought event occurred throughout the Zhujiang(Pearl)River Basin of South China.This decreased runoff into the river,resulting in increased salinity and reduced suspended substance.To examine the effects of this extreme drought on the distribution of nutrients and chlorophyll,we compared two surveys from 2006 and 2011.Results show that dissolved inorganic nitrogen concentration did not change from 2006 to 2011,whereas the proportions of NO 2 – and NH 4 + to DIN in 2011 increased.PO 4 3-concentration was lower in 2011 than in 2006,whereas there was no difference in SiO 3 2-concentration between these years.Correlation coeffi cients of salinity with levels of NO 3 –,NO 2 –,NH 4 +,PO 4 3-and SiO 3 2-in 2011 were all much higher than those in 2006,suggesting greater conservation of dissolved nutrients during the extreme drought event.Furthermore,calculated amounts of regenerated nitrate and phosphorus and their proportions to observed nutrients in 2011 were much lower than in 2006,indicating that nutrient regeneration decreased during the extreme drought period.Mean concentration of chlorophyll a(Chl-a)was considerably higher in 2011 than in 2006,and a harmful algal bloom of Cochlodinium geminatum was observed in the estuary,owing to water stagnancy and lower turbidity as a consequence of drought.Therefore,the extreme drought event in 2011 changed the composition ratio of nutrients,enhanced nutrient conservative behavior,and reduced nutrient regeneration.This affected some key ecological processes in the estuary.     

离子交换水处理工艺与双室逆流再生离子交换床

例举了离子交换水处理工艺，讨论了逆流再生离子交换器的结构设计特点，并给出主要具体设备参数。     

Land use change effects on catchment streamflow response in a humid tropical montane cloud forest region,central Veracruz,Mexico

Tropical montane cloud forests (TMCF) are recognized for their capacity to maintain high dry-season baseflow and a host of other ecosystem services. Substantial areas of TMCF have been converted to pasture and crops such as coffee, while in other areas TCMF are recovering. However, little is known about the effects of this complex dynamic on catchment hydrology. We investigated the effect of land use on rainfall-runoff response in five neighbouring headwater micro-catchments in central Veracruz, Mexico, dominated by either mature TMCF (MF), young (20 year-old) and intermediate (40 year-old) naturally regenerating TMCF (YF and IF, respectively), shaded coffee (SC), and an intensively grazed pasture (IP). We used a 4-year record of high-resolution rainfall and streamflow (10 min) data collected from 2015 to 2019. These data were analysed via comparison of hydrologic metrics that summarize streamflow responses at various time scales and magnitudes. Results showed no statistical difference in the regulation capacity of high flows in the micro-catchment with 20 years of natural regeneration, compared to the MF. In terms of baseflow sustenance, our results support the hypothesis that MF and IF better promote this hydrologic service than the other land uses. SC exhibited a high capacity to modulate peak flows comparable to that of MF, and an intermediate capacity to sustain baseflow, suggesting that the integrated functioning of this micro-catchment was largely preserved. Finally, 40 years of intense pasture management was found to have degraded the soil hydraulic properties of IP; mainly, reducing its infiltration capacity, causing a fivefold greater peak flow response and a lower baseflow compared to MF.