| Shellfish aquaculture is an important part of seawater aquaculture in China. Withthe gradual expansion of culture area and the continuous improvement ofintensification, a great many of inappropriate ways of aquaculture have caused theworseness of environment. Sediments is an very important living space for shellfish,and the quality of sediment environment is related to the success or failure of shellfishaquaculture. As the deterioration of the culture environment, more and more pollutantsare accumulated in sediments. And sediment pollution would restrict and endanger thedevelopment of aquaculture, so the study on environment remediation in sediments isvery necessary. The study investigated the removal efficiencies of the sulfide, totalnitrogen (TN), total phosphorus (TP), total organic carbon (TOC) and phosphorusforms in sediment of the clam culture areas at the physical (ploughing20cm or30cmin depth, both covering sand and beach ploughing) and biological remediation (add thepolychaetes Perinereis aibuhitensis at the densities of0.07kg·m-2,0.14kg·m-2,0.21kg·m-2and0.28kg·m-2, respectively) methods through simulated laboratoryexperiments. The results are as follow:(1) The results indicated that three physical remediation groups had all achievedsignificant results at the concentration of sulfide in sediment (P <0.05), and the resultof both covering sand and beach ploughing was better than only beach ploughing inexperiment, and the effect of ploughing30cm in depth was better than ploughing20cm in depth. Compared with the control group of bioremediation, all density groups ofPerinereis aibuhitensis reduced the concentration of sulfide in sediment environment,and the effects of0.14kg·m-2and0.21kg·m-2were prominent (P <0.05). The0.21kg·m-2was the best treatment group (the removal rate of sulfide was2.49×10-2mg·kg-1·d-1), however, when the density of Perinereis aibuhitensis increased to0.28kg·m-2, the removal rate of sulfide decreased to1.52×10-2mg·kg-1·d-1%.(2) The concentrations of TN, TP and TOC in sediment at two physical remediation groups (ploughing30cm in depth, both covering sand and beachploughing), and the concentration of TN and TOC in sediment at the group ofploughing20cm in depth were significantly lower than those in the control (P <0.05).The removal percentage of TN, TP and TOC were ranked in the following: bothcovering and beach ploughing> ploughing30cm in depth> ploughing20cm in depth.Two biological remediation groups (0.14kg·m-2and0.21kg·m-2) significantlydecreased the TN, TP and TOC concentrations in sediment compared to the control (P<0.05). And the results also indicated the following relationships for mean removalpercentage: the group at0.21kg·m-2> at0.28kg·m-2.(3)The contents of NH4Cl-P, Fe-P, Al-P, Ca-P, NaOH85-P and Org-P accounted for2.32%～2.81%,4.34%～6.48%,10.17%～12.98%,46.7%～55.6%,9.34%～12.47%and17.27%～20.56%of TP respectively in sediment of laboratory physicalexperiment. The contents of Fe-P, Ca-P and Org-P in sediment of at the group of bothcovering sand and beach ploughing, and the contents of Org-P at the other twophysical groups were significantly different from the control (P<0.05). The contents ofNH4Cl-P, Fe-P, Al-P, Ca-P, NaOH85-P and Org-P are2.32%～2.81%,4.34%～6.48%,10.17%～12.98%,46.7%～55.6%,9.34%～12.47%and17.27%～20.56%of TPrespectively in sediment of laboratory biological experiment. All four biologicalremediation groups significantly changed the NH4Cl-P, Fe-P and Org-P concentrationsin sediment compared to the control (P <0.05). The inorganic phosphorus was themajor phosphorus form in sediment, and the content of Al-P and NaOH85-P in sedimentwere not affected by different remediation methods in this experiment.(4)The influence of physical remediation groups on sulfide, TN, TP, TOC andphosphorus forms in sediments were ranked in the following: both covering and beachploughing> ploughing30cm in depth> ploughing20cm in depth. The effect ofPerinereis aibuhitensis was closely related to its density. the specific relationshipamong the four biological remediation groups is0.21kg·m-2>0.14kg·m-2>0.07kg·m-2, but0.21kg·m-2>0.28kg·m-2, and these can provide the evidence that theeffects of Perinereis aibuhitensis were not amplified with density absolutely. |
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