Microorganisms are significant components of beach sand.According to the research,all kind of microorganisms have been isolated from beach sand;certain genera and species are potential pathogens for humans and animals...Microorganisms are significant components of beach sand.According to the research,all kind of microorganisms have been isolated from beach sand;certain genera and species are potential pathogens for humans and animals.In resort areas,especially during the summer,certain infections(e.g.gastroenteritis and dermatitis)are usually related to polluted bathing water.Lately,the interest of scientists is also focused on the potential association of some of the above diseases with the beach sand.Relatively,recent epidemiological studies in the USA revealed positive correlation between time spent at the beach and gastroenteritis.New parameters such as wind blowing and beach users’density are also introduced for discussion in association with the sand microbial load.Regarding the preventative measures,the microbiological quality of beach sand can be improved by raising the general level of hygiene,as well as by using simple methods,such as sweeping and aeration of the sand,together with constant beach supervision.展开更多
The strength of cement substituted mortar decreases with the increase in fly ash amount,whereas the strength increases when the fly ash is blended as sand substitute.A mortar with highest strength(compressive strength...The strength of cement substituted mortar decreases with the increase in fly ash amount,whereas the strength increases when the fly ash is blended as sand substitute.A mortar with highest strength(compressive strength=30.2 Mpa;flexural strength=7.0 Mpa)was obtained when the sand replacement ratio was 0.75%.The k value(cementing efficiency)of fly ash varied between 0.36 and 0.15 for the fly ash fraction in binder between 5%and 25%.The k values of fly ash used for sand replacement were all significantly above that used for cement substitution.The macropores assigned to the gaps between particles decreased when the fly ash was used as sand replacement,providing an explanation for the strength enhancement.The waste-extraction procedure(toxicity-sulphuric acid and nitric acid method(HJ/T 299-2007))was used to evaluate metal leaching,indicating the reuse possibility of fly ash blended mortar.For the mortar with the mass ratio of fly ash to binder of 0.5%,the carcinogenic risks(CR)and non-carcinogenic hazard quotient(HQ)in sensitive scenario for blended mortar utilization were 9.66 x 10 and 0.06,respectively;these results were both lower than the threshold values,showing an acceptable health risk.The CR(9.89 x 105)and HQ(3.89)of the nonsensitive scenario for fly ash treatment exceeded the acceptable threshold values,indicating health risks to onsite workers.The main contributor to the carcinogenic and non-carcinogenic risk is Cr and Cd,respectively.The CR and HQ from inhalation was the main route of heavy metal exposure.展开更多
文摘Microorganisms are significant components of beach sand.According to the research,all kind of microorganisms have been isolated from beach sand;certain genera and species are potential pathogens for humans and animals.In resort areas,especially during the summer,certain infections(e.g.gastroenteritis and dermatitis)are usually related to polluted bathing water.Lately,the interest of scientists is also focused on the potential association of some of the above diseases with the beach sand.Relatively,recent epidemiological studies in the USA revealed positive correlation between time spent at the beach and gastroenteritis.New parameters such as wind blowing and beach users’density are also introduced for discussion in association with the sand microbial load.Regarding the preventative measures,the microbiological quality of beach sand can be improved by raising the general level of hygiene,as well as by using simple methods,such as sweeping and aeration of the sand,together with constant beach supervision.
基金The authors gratefully acknowledge the support from the National Natural Science Foundation of China(Grant No.NSFC21107062)the Key Laboratory for Solid Waste Management and Environment Safety(Tsinghua University)Foundation(Grant No.SWMES 2015-10).
文摘The strength of cement substituted mortar decreases with the increase in fly ash amount,whereas the strength increases when the fly ash is blended as sand substitute.A mortar with highest strength(compressive strength=30.2 Mpa;flexural strength=7.0 Mpa)was obtained when the sand replacement ratio was 0.75%.The k value(cementing efficiency)of fly ash varied between 0.36 and 0.15 for the fly ash fraction in binder between 5%and 25%.The k values of fly ash used for sand replacement were all significantly above that used for cement substitution.The macropores assigned to the gaps between particles decreased when the fly ash was used as sand replacement,providing an explanation for the strength enhancement.The waste-extraction procedure(toxicity-sulphuric acid and nitric acid method(HJ/T 299-2007))was used to evaluate metal leaching,indicating the reuse possibility of fly ash blended mortar.For the mortar with the mass ratio of fly ash to binder of 0.5%,the carcinogenic risks(CR)and non-carcinogenic hazard quotient(HQ)in sensitive scenario for blended mortar utilization were 9.66 x 10 and 0.06,respectively;these results were both lower than the threshold values,showing an acceptable health risk.The CR(9.89 x 105)and HQ(3.89)of the nonsensitive scenario for fly ash treatment exceeded the acceptable threshold values,indicating health risks to onsite workers.The main contributor to the carcinogenic and non-carcinogenic risk is Cr and Cd,respectively.The CR and HQ from inhalation was the main route of heavy metal exposure.
