Hydrogeology Of An Unconfined Sand Aquifer And Its Effect On The Behavior Of Nitrogen From A Large-Flux Septic System
Hydrogeology Of An Unconfined Sand Aquifer And Its Effect On The Behavior Of Nitrogen From A Large-Flux Septic System
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无承压砂土含水层的水文地质及其对大通量化粪池系统中氮行为的影响
DOI：
10.1007/pl00010960
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发表时间：
1992
期刊：
影响因子：
--
通讯作者：
J. Cherry
中科院分区：
文献类型：
--
作者：
W. Robertson;J. Cherry
在浅砂含水层的地下水的详细监测大通量化粪池系统的影响表明，在浅水区的瓷砖床下的地下水位区的水质是类似的小通量化粪池系统在类似的水文环境中，污水驻留在非饱和区的相似的持续时间。在4 m厚的非饱和带中停留约一周的时间内，出水NH+4大量氧化为NO−3，约75%的DOC被生物降解，上述反应产生的酸性被方解石溶解所中和。在瓦层之下，并向伊利湖海岸线横向向下延伸80米，一股明显的受影响地下水羽流很容易通过电导率、Cl−、NO−3、HCO−3、NA+、Ca 2+和K+的升高水平以及pH值和溶解氧的降低水平来区分。然而，在10 ~ 70 m下坡的厌氧羽流核心区，出现在瓦床下方的高NO− 3水平消失了，这显然是反硝化作用的结果。含水层沉积物中丰富的固相有机碳储量（2.5%）可能为异养反硝化提供了大量的有机碳。这种情况与砂含水层中的其他化粪池系统羽流形成对比，在砂含水层中，高NO− 3水平持续存在，含水层有机碳值低得多。虽然NO-3在羽流核心中减弱，但沿羽流有氧上部边缘的NO-3持续存在表明，当不存在有利于反硝化的条件时，化粪池系统能够导致砂含水层的显著水质退化。羽流水和邻近羽流并覆盖羽流的未受影响水之间的尖锐边界在距离瓦床50至100 m的下坡区域，以及整个羽流核心的非反应性溶质（例如Cl-）的未稀释性质，表明分散对羽流的影响很弱。这与许多其他砂质含水层的分散研究结果一致。
Detailed monitoring of groundwater in a shallow sand aquifer impacted by a large-flux septic system showed that water quality in the shallow water table zone below the tile bed was similar to that of smaller-flux septic systems in similar hydrologic settings where effluent residency in the unsaturated zone was of similar duration. During residency of about one week in the 4-m thick unsaturated zone, effluent NH+4was largely oxidized to NO−3, about 75% of DOC was biodegraded, and acidity produced by the above reactions was neutralized by dissolution of calcite. Beneath the tile bed and extending laterally downgradient a distance of 80 m to the Lake Erie shoreline, a distinct plume of impacted groundwater was easily distinguished by elevated levels of electrical conductance, Cl−, NO−3, HCO−3, NA+, Ca2+, and K+and by depressed levels of pH and dissolved oxygen. High NO−3levels that occur below the tile bed disappear, however, in the anaerobic plume core zone 10 to 70 m downgradient, apparently as a result of denitrification. The rich reserve of solid-phase organic carbon in the aquifer sediment (2.5%) probably provides much of the organic carbon for heterotrophic denitrification. This condition is in contrast to other septic system plumes in sand aquifers where high NO−3levels persist and where aquifer organic carbon values are much lower. Although NO−3is attenuated in the plume core, persistence of NO−3along the aerobic upper fringe of the plume demonstrates the ability of septic systems to cause significant water-quality degradation of sand aquifers when the conditions favorable for denitrification do not exist.The sharp boundary between the plume water and non-impacted water adjacent to and overlying the plume in the area 50 to 100 m downgradient from the tile bed, and the undiluted nature of non-reactive solutes such as Cl−throughout the core of the plume, demonstrates that dispersion has only a weak influence on the plume. This is consistent with dispersion studies in many other sand aquifers.