Effects Of Exogenous Sulfur On Cadmium Stress Of Soil Animals In Red Earth And Paddy Soil In Southern Fujian

Soil is a complex ecosystem to maintain life on the earth,and the interaction of various biological and abiotic environmental factors will have an impact on the soil system.cadmium pollution in soil has been paid great attention by scholars at home and abroad because of its wide area and potential harmful risk to organisms.Sulfur is an essential element for plants to form various proteases,and sulfur-containing proteins such as plant chelate,metallothionein and glutathione play a key role in the survival of plants under heavy metal stress.as a result,a large amount of sulfur fertilizer is put into the world every year to increase crop production.Most of the existing studies focus on the effect of exogenous sulfur on cadmium stress in soil plants,but there are few reports on the effect of exogenous sulfur on cadmium stress in soil animals.Soil animal is an important part of soil ecosystem,which not only plays an irreplaceable role in the process of soil formation and development,but also is one of the important indicators to evaluate soil quality and health status.Therefore,it is necessary to take soil animals as the research object to explore the effects of exogenous sulfur on soil animals under cadmium stress,in order to clarify the ecological health risks of soil animals under cadmium stress.In this paper,the common soil animals Eisenia foetida,Folsomia candida and Caenorhabditis elegans were selected as the research objects to study the changes of ecotoxicity,antioxidant system and genotoxicity of the three soil animals under cadmium stress under the growth conditions of red soil and paddy soil in southern Fujian.To explore the effect mechanism of exogenous sulfur on cadmium stress in soil animals.The results show that:?1?The effects of exogenous sulfur on the ecotoxicity of cadmium stress in three invertebrates were studied.The reproduction numbers of E.foetida,F.candida and C.elegans decreased significantly with the increase of cadmium concentration?p<0.05?.After adding sulfur,the reproduction numbers of E.foetida and F.candida were observed to increase in different degrees at the same cadmium concentration,and the sulfur concentration addition was 100 mg?kg^-1.The increased reproduction number was more obvious than that when the sulfur concentration was 250 mg?kg^-1,but in the experiment of C.elegans,it was observed that the reproduction number decreased after adding sulfur,and the larvae were not even observed.?2?The toxicity threshold of the same organism in different soil is different,and the toxicity threshold of different organisms in the same soil is also different.It is concluded that the sensitivity of three kinds of soil invertebrates to cadmium is E.foetida,C.elegan and F.candida,while in the test of reproductive toxicity,the order of half effect concentration is F.candida,C.elegans and E.foetida.it was also found that cation exchange capacity and organic matter content were important soil environmental factors significantly affecting the toxicity threshold of cadmium?p<0.05?.if we want to carry out the ecological risk assessment of soil pollution,the sensitivity of animal reproduction rate as the test end point is better than the mortality rate.?3?The effects of exogenous sulfur on the antioxidant system of three soil animals under cadmium stress were studied.The activities of catalase?CAT?,glutathione?GSH?and metallothionein?MT?contents of E.foetida,F.candida and C.elegan fluctuated with the increase of cadmium concentration,and the change trend was different.However,compared with those without sulfur at the same cadmium concentration,it was found that the catalase?CAT?activity,glutathione?GSH?and metallothionein?MT?content of the three animals increased to some extent after adding sulfur,and the catalase?CAT?activity and glutathione?GSH?content of F.candida in the paddy soil experimental group in the same area were higher than those in the red soil group.?4?The effects of exogenous sulfur on genotoxicity of cadmium stress in three invertebrates were studied.Cadmium single pollution could cause DNA damage in E.foetida,F.candida and C.elegans cells,and there was a significant dose-effect relationship between cadmium single pollution and DNA damage in earthworm cells.Compared with the value of OTM without adding sulfur,the value of OTM in low concentration of cadmium was sometimes high and sometimes low,but at the highest concentration of cadmium,after adding sulfur(100 mg?kg^-1 and 250 mg?kg^-1),the OTM value of cells of E.foetida and C.elegans was lower than that of OTM without sulfur,indicating that the DNA damage of earthworm and nematode cells caused by cadmium decreased.In the experiment of F.candida,compared with the OTM value without adding sulfur,the OTM value was sometimes high and sometimes low,indicating that sulfur could not only enhance but also weaken the DNA damage of jumper cells under cadmium stress.