Agricultural Pollutant Penetration and Steady State in Thick Aquifers
Agricultural Pollutant Penetration and Steady State in Thick Aquifers
复制标题
厚含水层中农业污染物的渗透和稳态
作者：
G. Kraft;B. A. Browne;W. Devita;D. J. Mechenich
由于化肥和农药使用量的增加，从农田向含水层渗漏的污染物大大增加。由于这种增加是最近的，地下水污染物的浓度、负荷和出口量也可能随着污染物深入含水层而增加。我们在一个农业景观中建立了含水层剖面，其中30米的农田覆盖了57米厚的砂岩含水层，建立了地下水补给和污染物泄漏的年表。污染物浓度从含水层底部较老的地下水（1963年）增加到含水层顶部较年轻的地下水（1985年），这是污染物泄漏增加的信号。硝态氮从0.9 mg/L增加到13.2 mg/L，意味着泄漏量从1.9 kg/ha/年增加到16.5 kg/ha/年。硝态氮的负荷量和出口量可在20 ~ 40年内由130%增长到230%，达到稳定状态。氯化物的增加也是类似的。农药残留四氯乙烷磺酸（ESA）、异甲草胺（ESA）和阿特拉津残留部分渗透到含水层剖面中。它们的浓度-年龄-日期模式表现出初始增加，然后趋于稳定，对应于产品采用的时间和需求的稳定。与NO3不同，随着时间的推移，农药产品的逐步使用和退出使农药残留稳态的预测变得复杂；例如，该地区目前既没有使用甲草胺，也没有使用阿特拉津，而是采用了尚未来得及进入含水层的新产品。导致缺乏污染物稳定状态的情况并不罕见；因此，农业地区含水层缺乏稳定状态可能并不罕见。
The leakage of pollutants from agricultural lands to aquifers has increased greatly, driven by increasing fertilizer and pesticide use. Because this increase is recent, ground water pollutant concentrations, loads, and exports may also be increasing as pollutants penetrate more deeply into aquifers. We established in an aquifer profile a ground water recharge and pollutant leakage chronology in an agricultural landscape where 30 m of till blankets a 57‐m thick sandstone aquifer. Pollutant concentrations increased from older ground water (1963) at the aquifer base to younger ground water (1985) at its top, a signal of increasing pollutant leakage. Nitrate‐N increased from 0.9 to 13.2 mg/L, implying that leakage increased from 1.9 to 16.5 kg/ha/year. Nitrate load and export could increase from 130% to 230% before reaching a steady state in 20 to 40 years. Chloride increases were similar. Pesticide residues alachlor ethane sulfonic acid (ESA), metolachlor ESA, and atrazine residues partially penetrated the aquifer profile. Their concentration‐age‐date patterns exhibited an initial increase and then a leveling corresponding to the timing of product adoption and leveling of demand. Unlike NO3, projecting pesticide residue steady states is complicated by the phasing in and out of pesticide products over time; for example, neither alachlor nor atrazine is currently used in the area, and newer products, which have not had time to transit to the aquifer, have been adopted. The circumstances that resulted in the lack of a pollutant steady state are not rare; thus, the lack of steady states in agricultural region aquifers may not be uncommon.