新型锁磷剂的磷固持特征及应用效果的研究

【作者】 程鹏；

【导师】 李清曼；

【作者基本信息】 大连海洋大学 ， 水产， 2022， 硕士

【摘要】 富营养化是当今世界面临的主要水环境问题之一,而内源营养物质释放是维持水体长期富营养化的重要因素。磷是水体富营养化的主要限制因子,外源输入的磷绝大部分赋存于底泥,控制底泥磷释放是富营养化水体治理的前提条件。原位处理磷高风险底泥技术的核心是锁磷剂,其性能决定治理的效果、成本和生态环境风险,是底泥原位处理技术研究的热点和难点。本文在调查与评估洪潮江（HCJ）、牛尾岭（NWL）两座水库内源释放风险的基础上,批实验探究了基于铝氧化物和钙氧化物高温合成新型锁磷剂的磷固持特征,并通过静置释放实验验证了其实际应用效果。主要结果和结论如下:1.底泥NaOH-P（用NaOH提取的P）含量最高,占总提取P的42-51%,其次是BD-P（还原剂可溶性P,主要由Na₂S₂O₄提取的P）和Res-P（残留P）。底泥有机氮（Org-N）含量最高,占总提取氮的92-95%,其次是KCl-N（用KCl提取）和H₂SO₄-N（用H₂SO₄提取的N）。HCJ底泥TP和TN都低于NWL。NWL底泥上清液中的TP和SRP（溶解活性P）高于HCJ,而TN和NH₄⁺-N总体上差异不很明显。升高温度可提高上清液中营养物质的浓度,在25℃时,几乎所有营养物质指标（TP,SRP,TN和NH₄⁺-N）都较15℃时的高。影响TN、NH₄⁺-N、TP和SRP表观释放通量的基本因素是沉积物的吸附特性（可以用水提取P、可交换P、总无机氮和pH来表示）和氧化还原特性（可以用铁含量、可还原性P及沉积物氧化还原电位来表示）或微生物介入特性（可以用总有机碳、有机P等来表示）。控制N、P表观释放通量的基本因子与它们的形态和温度有关。其中N的表观释放通量对磷的影响有限,但两者都与温度相关。当温度从15℃增加到25℃时,两者的表观释放通量明显地增加。2.新型锁磷剂的最大磷固持量与投加前的酸化时间有关。当酸化24 h时,最大磷固持量为38.6 mg·g^-1,而酸化12 h时,最大磷固持量为30.5 mg·g^-1。与已有商品锁磷剂相比,新型锁磷剂的最大磷固持量远较它们的高。在正常沉积物pH范围内（中性pH）,锁磷剂的磷固持量最高。过高的离子强度（1.0M KCl）会降低其磷固持量,但沉积物环境的离子强度对磷固持量的影响较小,特别是当锁磷剂对磷的固持远未达到饱和时,离子强度对磷固持量的影响可以忽略。固持动力学结果表明,新型锁磷剂对磷的固持达到平衡所需要的时间较长（120 h以上）。锁磷剂对磷的固持是一个吸热且自发的过程。升高温度有利于锁磷剂对磷的固持。3.磷高风险表层底泥投加新型锁磷剂后,上覆水磷浓度下降显著（p<0.05）。与对照相比（未投加锁磷剂）,底泥磷释放通量为负值,显示锁磷剂不仅阻止底泥有磷效的释放,同时也促进了上覆水磷向底泥的转移。锁磷剂对底泥磷的钝化效果从间隙水磷和有效磷的下降得到了进一步的证实。锁磷剂投加后,有效地降低了间隙水磷和有效磷,特别是有效磷,与对照相比,其下降幅度可达50%。更多还原

【Abstract】 Nowadays,eutrophication has been one of the most severe water environmental problems around the world,and the release of nutrient elements from sediments plays a vital role in maintaining continuous eutrophication of water bodies.Phosphorus（P）is a key limiting nutrient element of eutrophication,most of the externally imported P is stored in sediments.Therefore,it is necessary to prevent the excessive release of P from sediments to the water column during the treatment of eutrophic water bodies.The phoslocks are the core of in situ passivation techniques,which have been widely applied in the treatment of P high-risk sediments.The performance of a phoslock determines the effect,cost and ecological and environmental risk of sediment treatment,which is still the hot spot and difficulty of in situ passivation techniques.Based on the investigation and assessment of the risk of internal nutrient release from Hongchaojiang（HCJ）and Niuweiling（NWL）,the P retention characteristics of a new phoslock prepared by high-temperature synthesis of aluminium oxides and calcium oxides were explored with the batch experiments,and its the practical application effect was estimated through static release experiments.The conclusions were as follows:1.The NaOH-P（P extracted by NaOH）was the highest in sediments,accounting for42-51%of the total extracted P,followed by BD-P（reducible P,exctracted by Na₂S₂O₄）and Res-P（residual P）.The organic nitrogen（Org-N）content of the sediment was the highest,accounting for 92-95%of the total N,followed by KCl-N（N extracted by KCl）and H₂SO₄-N（N extracted by H₂SO₄）.The total phosphorus（TP）and total nitrogen（TN）in HCJ sediments were lower than that in NWL sediments.The content of TP and soluble reactive phosphorus（SRP）in overlying water in the NWL were higher than HCJ,while the content of TN and NH₄⁺-N were similar.The content of most nutrients（TP,SRP,TN and NH₄⁺-N）in the overlying water at 25℃were higher than that at 15℃.The fundamental factors that impact the apparent release flux of TN,NH₄⁺-N,TP and SRP were related to the adsorption characteristics of sediments（i.e.extracting P with water,exchangeable P,total inorganic N or pH）and redox properties（i.e.iron content,reducible P or redox potential of sediments）or ones induced by sediment microorganisms（i.e.total organic carbon,organic P,etc.）.The factors responsible for the apparent release fluxes of N and P from sediments were relevant to their species and temperature.The apparent release flux of N had a limited influence on that of P.The apparent release fluxes of N and P were obviously increased when the temperature was raised from 15 to25℃.The maximum P retention of the new phoslock highly depended on acidification time.When the phoslock was acidified for 12 h,its maximum P retention reached to 30.5 mg·g^-1,and the corresponding value increased to 38.6 mg·g^-1if acidification time was increased to 24 h,meaning that they were much higher than other commercial phoslocks currently reported.2.The phoslock had the highest P retention under the natural sediment pH.Excessively high ionic strength（1.0M KCl）could decrease the maximum P retention of phoslock,however,the low ionic strength similar to that in natural sediments had less effect on P retention,especially when the phoslock to bind P was far from saturated,in which the effect of ionic strength could be ignored.The dynamic results showed the retention of P by the new phoslock was time-consuming,which more than 120 h was required to obtain equilibrium.The retention of P to the phoslock was an endothermic and spontaneous process.Raising reaction temperature was conducive to the phoslock to retain P.3.The addition of new phoslock with different amounts on the surface sediments with high P risk significantly decreased the P concentration in the overlying water（p<0.05）.The release fluxes of sediment P were calculated to be negative,compared with the treatment without phoslock,indicating that the phoslock prevented the P release from sediments,but also promoted the transfer of P from the overlying water to sediments.The effect of phoslock addition on P passivation was further confirmed by the decreases of P in interstitial water and available P in sediments.Addition of the phoslock effectively decreased interstitial water P and available P,especially available P,the reduction magnitude of which approached to 50%,compared with the treatment without phoslock.更多还原