Research On Water Environment Quality Of Higher-place Shrimp Pond

With the rapid development of the aquaculture industry,the cultivation method has gradually shifted to intensive aquaculture with high-density stocking and feed feeding,which has caused increasingly serious environmental problems.Therefore,it is of great environmental ecology significance to deeply study the water environment of the higher-place shrimp ponds reveals its potential environmental risks.In this study,a farm in Dongying Village,Haikou City was used as the research target area.Through the track?monitor and analysis of nutrients,heavy metals and antibiotics in the water during the middle and later stages of cultivation,the article revealed the changes of water quality in different aquaculture periods and evaluated potential risks to the water environment in different aquaculture periods.Through the analysis of heavy metals and carbon and nitrogen contents in the bottoms of cultured shrimp ponds,the article identified the spatial occurrence characteristics of heavy metals and carbon and nitrogen contents in the sediment environment and then evaluated potential ecological risks caused by higher-place shrimp pond culture to environment;By monitoring the contents of nutrients,heavy metals and antibiotics in aquaculture tail water,the article analyzed their residual amount and environmental load,and simulated the analysis of Ammonia nitrogen?NH₃-N?,Total phosphorus?TP?degradation and its influencing factors in aquaculture tail water.The main findings are as follows:?1?The Inorganic nitrogen?DIN?of the water quality in the middle stage of shrimp pond cultivation were higher than the standard by 1.40 times,and the comprehensive water quality pollution index was rated as qualified Levels;The TP and DIN of the water quality were higher than the standard by 1.70 and 1.66 times,respectively,and the comprehensive water quality pollution index was rated as pollution level;No Ni was detected,and the content of other heavy metals was relatively low.The Romero pollution index was rated as safe?clean?,and there was no risk of heavy metal pollution in the water body.The antibiotics sulfamethoxazole?SMX?,sulfathiazloe?STZ?and sulfamethazine?SMZ?.?2?The SMX,STZ and SMZ were not detected in the aquaculture tail water after standing,which was no NH3-N,DIN,TP and heavy metal were exceeded in the tail water.The simulation experiment confirmed that after standing the water still for more than 10 days,even the excessive nutrients in the water body will naturally degrade under high temperature and light conditions.Therefore,the aquaculture wastewater should be left at least 10 days before being discharged to reduce the risk of environmental pollution by shrimp pond aquaculture wastewater.?3?The infiltration of wastewater from higher-place shrimp ponds eventually resulted in the contents of Total carbon?TC?,Total organic carbon?TOC?,and Total nitrogen?TN?in the shrimp ponds soil outside the embankment of shrimp ponds was 5.66,6.95,and 2.49 times higher than the background values of the shrimp ponds,respectively;The contents of TC,TOC and TN in the sediment were 7.36,8.68 and 4.41 times higher than the environmental background value,which was caused by accumulation of baits and shrimp excrement in the sediment of the shrimp ponds.The contents of TN,TC,and TOC in the sediment of the shrimp pond with sand bottom were the highest in the surface layer and 2?27 times higher than that in the deep soil.In the bottom auxiliary cement shrimp pond,the contents of TN,TC and TOC in the crack were the highest in the third layer of soil,showing t3>t1>t2>t4;The contents of TN,TC,and TOC on the outside of the shrimp pond dike obviously decreased from the surface layer to the deep layer.The TOC and TN in the uncleaned shrimp pond surface sediments and bait and shrimp dung during culture were seriously exceeded the standard after the discharge of wastewater.The organic nitrogen and organic index of the surface sediments of unwashed shrimp ponds after discharge of wastewater were rated as?moderate pollution and?mild pollution,while the organic nitrogen and organic index rating of bait and shrimp dung residue during the cultivation were classified as?severe pollution;The organic indexin the lateral soil of the shrimp ponds embankment was?moderate pollution,while the organic nitrogen the rating was?severe pollution.The ratio of C:N in the sediment of the shrimp pond is low,which is conducive for the formation of humus stem from residual baits and biological excretions in sediments,if the humus are not cleaned in time,it will lead to aquaculture water quality deterioration.?4?The content of heavy metals in the bottom of the unwashed shrimp pond increased significantly from the surface to the deep;Cd in the surface sediment of the shrimp pond showed a significant accumulation?pollution?phenomenon,and exceeded the soil background value of Hainan Province by 5.47?35.18 times;The evaluation of the geoaccumulation index?Igeo?showed that there were two or more heavy metals in all types of substrates reaching mild-medium pollution level and above;The comprehensive potential ecological risk index?RI?results showed that the range of RI was 176.97?1090.87,and the comprehensive potential ecological risk in various areas reached medium or above,of which Cd was the main contributing factor;Pearson correlation analysis showed that the bait residues and prawn excreta contained in shrimp pond bottoms contained Cr,Ni,Cu,As,Cd,TOC have a very significant correlation with each other,the correlation coefficient is as high as 0.9 or more.It shows that these substances are homologous and are likely to be derived from the bait applied by farmers,and the TOC rich in bait and prawn excrement will have a certain effect on the accumulation of heavy metals Cr,Cu,As and Cd.?5?The tracking and monitoring of aquaculture tail water into the experimental pool showed that was no significant difference in the degradation of NH3-N in the two pools of the S pool on the paved basalt and the SH pool on which the hippocampus was replanted.It can be seen that the porous basalt can accelerate the removal rate of NH₃-N through ion exchange or physical adsorption.The adsorption and degradation of TP by basalt was mainly concentrated in the first 6 days,while the absorption and degradation of TP in the tail water of the shrimp hippocampus pond was in the third d reaches the maximum,and then the effect was not much different from that of S pool and J pool.If you want to discharge the tail water of shrimp ponds as soon as possible,you can consider planting hippocampus teeth in the shrimp pond drain to absorb TP in the tail water.The experimental results also showed that the tail water of the shrimp pond has undergone self-purification after 10 days.At the time,the surface type?changed to surface type?,and the content of TP could basically be degraded from type?to type?.During the experiment,the Dissolved oxygen?DO?content in the tail water of J pond was above 10.86 mg·L^-1,and the higher the DO value.It not only promotes the absorption of nitrogen and phosphorus by aquatic organisms due to reproduction and growth,but also accelerates the decomposition rate of organic matter,so that the material cycle in the ecosystem,especially the nitrogen cycle,achieves the best cycle effect and improves the self-purification ability of water qualities.