濁水溪潛在揚塵發生區位劃定與揚塵防治對策之研究

Abstract

摘要 台灣中部河口因冬季乾旱導致水位下降，河床裸地增加，適逢東北季風盛行，易產生揚塵危害，影響生活環境品質甚鉅，如何快速劃定潛在揚塵發生區位並有效防治極為重要。 本研究以自強大橋下游至西濱大橋為試區，蒐集試區鄰近之空氣品質測站資料，利用地理統計（克利金法）推估多期懸浮微粒PM10之等值線空間分布調查分析，結果顯示冬旱季PM10濃度值均偏高。藉由衛星影像結合影像處理技術劃定河道潛在揚塵發生區位，不同土地利用類別交界處因色階梯度變化，可利用Sobel Filter進行邊緣偵測，因裸地與水域特徵值相近，在邊緣萃取時易形成斷線導致無法形成封閉區塊，需透過影像處理將水域先行劃出，俟裸地初步萃取後再扣除水域範圍即可得到實際之裸地區位。 在揚塵防治方面，以生物聚合物三仙膠作為材料，三仙膠係一種食品增稠劑，溶於水具黏性，噴灑於土砂上可膠結表面，保護底層土壤抵抗風蝕。現地取樣進行室內試驗，分析不同濃度三仙膠處理下之定砂效益，尋求最佳之施作濃度，並於自強大橋南岸附近河岸裸地進行施作。研究結果顯示：於河道潛在揚塵發生區位施作三仙膠約可減少80%之揚塵料源，明顯提升土壤抗風蝕能力，且三仙膠性質穩定、無毒害、具生物可分解性、成本低廉，為經濟實惠之揚塵改善工法。

Abstract Due to the huge bare soil in drought season, and the monsoon effect, the estuaries of rivers in central Taiwan are susceptible to severe wind erosion. Dust emission decreases the living quality and affects the human health nearby. It is important to delineate the potential areas of the aeolian dust and prevent the dust effectively. This study focused on the dust vulnerable segment (Bridge Ziqiang to Xibin) of Jhuoshui River by using air quality monitoring data to delineate the spatial distribution of multi-temporal PM10 content in the air using Kriging method, and integrating the image process couples with edge extraction using SPOT satellite imagery and on-site investigation to depict the potential areas of the aeolian dust occurrence in the River. Sobel Filter was used to extract the edges of different land use by means of gradient of grey values, and the boundary line of classified patch for the bare land can not be closed due to the interference of water patch, which showing the same eigenvalues with bare land. The actual bare land can only be extracted by deducting the water patches, which should be pre-delineated by using image process. Xanthan gum, one kind of biopolymer, was used as a material to prevent the dust. It was an edible thickening agent with viscosity after dissolving in water. Xanthan gum solution could cement soil surface against wind erosion. Benefits of sand fixation under different concentration of Xanthan gum treatments were carried out at the laboratory by using in-situ sand materials, and the suitable application concentration was derived to employ at the bare land nearby the southern bank of Ziqiang Bridge. Results showed that the treatment of Xanthan gum could decrease 80% sources of aeolian dust. Xanthan gum obviously improved soils to resistant the wind erosion. With the properties of stability, no toxicity, biodegradability and low cost, Xanthan gum could be recommended as an economical engineering method on aeolian dust prevention.