Study of using rhinoceros beetle for metal treatment

[[abstract]]台灣重金屬污染源來源廣泛，包括工業廢水、農業與畜牧業廢水、空氣污染、事業廢棄物等; 隨著全國經濟發展、人口都市化及品質要求提高等因素，各來源重金屬總量與日俱增，使得全國受重金屬污染河道、農田亦或污染場址等問題日益嚴重。尤其土壤重金屬無法像有機化合物在土壤中被分解，容易透過生物濃縮或生物放大作用累積在人體中，也增加受污染土壤整治復育的難度。截至目前，全世界已發展出多套土壤重金屬的整治復育技術，但其中仍有許多技術的經濟可行性不高、亦或且不符時間成本，亦或是整治後難以恢復土壤原有正常功能。在永續環境前提下，如何以具環境親和力技術，有效移除土壤中重金屬並活化土地利用，是目前研究重要議題之一。本研究係以甲蟲為生物反應器，探討其對食入重金屬之代謝方式，藉以開發具環境親和力之土壤重金屬復育技術，主要研究目的包括：(1)測試銅、鋅、鎳對甲蟲生長抑制強度、(2)探討甲蟲攝食飼育材含重金屬之代謝現象、及(3)評估以蟲糞做為土壤改良劑及改良後土壤前處理之需要性。 研究主要將甲蟲飼育材以外添加工業廢污泥中常見之銅、鋅、鎳等重金屬方式進行甲蟲金屬代謝行為測試，並進一步測試甲蟲幼蟲馴化與其抗金屬毒性差異。再者，因甲蟲糞便呈顆粒狀容易收集，應可做為土壤改良劑，另考量直接使用容易造成植栽作物受蟲害影響，故以催化氧化技術做土壤前處理的需要性亦一併評估。研究結果顯示：甲蟲在四週飼養下，對含鎳飼育材之攝食量較含銅或鋅飼育材更高，其攝食量分別為111 7 g/week、93 2 g/week及60 3 g/week; 而且飼育材中金屬濃度愈高，則甲蟲對金屬吸收量愈高，但致死率也愈高。經六週飼養後，對金屬吸收累積量達到飽和而趨平緩，而且以鎳而言，其所吸收金屬量可在甲蟲蛹化過程所廢棄外皮中回收。針對重金屬毒性而言，經過四週對三齡幼蟲的飼養中發現，銅、鋅、鎳對老鼠之LD50分別為300 mg/kg、1260、275 mg/kg，而當飼育材含銅及鋅濃度分別超過600和630 mg/kg時，將造成50 %以上死亡率，但含鎳飼育材則在濃度2 730 mg/kg時，死亡率卻只有25 %; 此外，在訓養實驗中發現，於含鋅反應槽中，將甲蟲幼蟲先飼養於濃度150 mg/kg環境2個月後再移至濃度750 mg/kg飼育材的馴化作用中，甲蟲死亡率將可從直接置入750 mg/kg的67 %降至13 %。最後使用土壤與蟲糞比為4的配比土壤，並添加1 000 mg/kg豬血及0 3 %過氧化氫進行土壤前處理，土壤因蟲糞添加而有助於通透性的提升及其所貢獻之肥力使植體得到最佳生長成效。[[abstract]]The sources of Taiwan heavy metal pollution come from various industrial wastewater, agriculture and livestock wastewater, air pollution and industrial soild wastes. Due to the the development of national economy, the urbanization of population and the demand of high quality goods, the pollution of heavy metals is worsen, resulting in the increasing contamination of the river sediments, farmlands and/or soils nationalwise. Heavy metals in soil for example cannot be degraded and vanished like organic substances, and are readily bioconcentrated or biomagnified within human bodies, which increase the difficulities for their cleanups. Up to now, there are many alternatives in remedying soil heavy metals, yet most of the techniques are either economical infeasible or time inefficienct or restoration of soil function inapplicable. For environmental sustainability, use of environmental friendly technique to remove soil heavy metal effectively and reuse the remedied soil is deserved further investigation. This study was to employed beetles as bioreactors to explore the adsorption efficiency of heavy metals by beetles so that the development of environmental friendly alternative for soil heavy metal remediation becomes a reality. The objectives include: (1) To evaluate the toxicity of copper, zinc and nickel to the beetle growth, (2) to determine the adsorption efficiency of metals intaken by beetles, and (3) to study the feasible use of beetle feces as soil conditioner and the necessity of the soil pretreatment.At first commonly seen industrial heavy metals, i.e., copper, zinc and nickel, were spiked into the beetle’s feed and the fate of individual metal was analyzed. Furthermore acclimation effect was evaluated through examining beetle’s ability in standing high concentration of metals in its feed. Finally the beetle feces appear as granules, are easy to collect and are used as a soil conditioner for veggie plantation. To avoid potential insect growth due to the direct use of the feces, some catalytic oxidation means were used to pretreat the soil. The study results showed that in four weeks the beetles consumed more nickel-contaminated feed (111.7 g) than copper- and zinc- contaminated feeds (93.2 and 60.3 g respectively). Also the higher tested metal content in the feed, the higher metal adsorption and beetle death rate resulted. Metal adsorption in beetles became flat and saturated after 6 weeks. Afterwards, the most adsorbed metal (e.g. nickel) could be recovered in the discarded shell during pupation. More than 50% death rate observed if Cu and Zn content in feed was greater than 600 and 630 mg/kg respectively, yet only 25% death rate observed for nickel at 2,750 mg/kg. Acclimation of beetles using 150 mg-Zn/kg-feed before moving them to 750 mg/kg Zn-contaminated feed reduced the beetle death rate from 67 to ~13%. Use of soil/feces ratio at 4/1 and the soil pretreated with pig blood and peroxide at 1,000 mg and 3 g per kilogram soil resulted in best plant growth